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+
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+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-presence-attrs-04.txt 15 January 2007
+Expires: 15 July 2007
+
+
+ User Online Presence and Information Attributes
+ <draft-riikonen-presence-attrs-04.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+
+Abstract
+
+ This document defines set of attributes that can represent the online
+ user's presence in a network, and to provide general information about
+ the user. The purpose is to provide a generic mechanism to share
+ online presence and status, and general information about the user
+ to be used in several kind of network protocols and applications.
+ These attributes could be used by for example chat and conferencing
+ protocols (such as Instant Message protocols), network games, and
+ other similar network protocols and applications that has online
+ users in a network.
+
+
+
+
+
+
+
+
+
+Riikonen [Page 1]
+\f
+Internet Draft 15 January 2007
+
+
+Table of Contents
+
+ 1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 2
+ 2 Attributes Concept ............................................ 3
+ 2.1 Requesting Attributes ..................................... 3
+ 2.2 Replying Attributes ....................................... 3
+ 2.3 Attribute Data Types ...................................... 4
+ 2.4 Attribute Payload ......................................... 4
+ 2.5 Attributes ................................................ 5
+ 3 Security Considerations ....................................... 12
+ 4 References .................................................... 12
+ 5 Author's Address .............................................. 13
+ 6 Full Copyright Statement ...................................... 13
+
+
+1. Introduction
+
+ This document defines set of attributes that can represent the online
+ user's presence in a network, and to provide general information about
+ the user. The purpose is to provide a generic mechanism to share
+ online presence and status, and general information about the user
+ to be used in several kind of network protocols and applications.
+ These attributes could be used by for example chat and conferencing
+ protocols (such as Instant Message protocols), network games, and
+ other similar network protocols and applications that has online
+ users in a network.
+
+ This document does not define these attributes to be used in any
+ specific protocol, but assumes that they can be used generally in
+ any kind of online network protocol. Furthermore, the document
+ pays attention to special needs of various protocols, such as
+ mobile network protocols, which requires the attributes to be
+ both robust and compact. The attributes are also considered to be
+ easily implementable and for this reason a clear and robust structure
+ was chosen for the attributes.
+
+ This document is strongly influenced by Wireless Village Initiative
+ where similar attributes are defined, and credits for the ideas are
+ due there. However, they are defined only in the context of the
+ Wireless Village, and the format of the attributes used is not
+ suitable for general purpose usage.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+
+
+
+Riikonen [Page 2]
+\f
+Internet Draft 15 January 2007
+
+
+ interpreted as described in [RFC2119].
+
+
+2 Attributes Concept
+
+ Many network protocols needs a way to transfer and retrieve status
+ information about users in a network. For example, many chat and
+ conferencing protocols such as IRC, and all Instant Message (IM)
+ protocols, such as ICQ has a way to retrieve presence and status
+ information about the users in the network. This could be added to
+ several other kind of network protocols as well, and for this reason
+ a defined mechanism to provide these informations is needed.
+
+ The attributes are usually requested by an entity in the network
+ from other entity, usually a user or end user's device in the network.
+ The recipient then replies to each of the requested attributes and
+ sends the reply to the requester.
+
+ This document does not define the actual transport for requesting and
+ providing the replies to the requests, since this is irrelevant.
+ This document defines a payload for requesting, and providing the
+ information, but how the payload is transported is not defined in
+ this document. In a client-server network model the user requesting
+ attributes usually destine the request to a remote user and the
+ server relays the attributes to the remote user. It is also possible
+ that the concept is not user-to-user, but the server replies to the
+ requested attributes on behalf of the user.
+
+
+2.1 Requesting Attributes
+
+ When an entity requests attributes from a user in the network,
+ it assembles a list of Attribute Payloads, and sets the requested
+ attribute value into the payload. Each requested attribute is a separate
+ Attribute Payload and they MUST be appended one after the other. The
+ requester need to understand that the recipient may not understand all
+ the requested attributes, and may not reply to all of the requested
+ attributes. The requester also need to understand that the recipient
+ may reply with additional attributes that were not requested.
+
+
+2.2 Replying Attributes
+
+ When en entity receives the Attribute Payloads it parses them one after
+ the other. The entity can parse each of the Attribute Payload separately
+ since it knows the length of the current attribute; next attribute
+ begins after the current attribute ends. The entity then checks the
+ requested attribute and SHOULD reply either with valid value or with
+
+
+
+Riikonen [Page 3]
+\f
+Internet Draft 15 January 2007
+
+
+ an indication that the attribute is unsupported or unknown. It is
+ also possible to reply with additional attributes that were not
+ requested.
+
+ When replying to the requested attributes the entity assembles a list
+ of Attribute Payloads, each including the attribute type and the
+ actual attribute data.
+
+
+2.3 Attribute Data Types
+
+ This section defines basic data types that can appear in the attributes
+ in this document.
+
+ All integer values are stored in the MSB first order. The size of the
+ integer is provided separately with the attribute. Integer is
+ represented as "integer" in this documentation.
+
+ Strings MUST be UTF-8 [RFC2279] encoded, and include 2 bytes length
+ field indicating the length of the string. Hence, when "string" value
+ appears in this documentation it is encoded as:
+
+ Length Type Value
+ 2 bytes integer Length of String field
+ variable UTF-8 String
+
+ If string is not present then the length field includes zero (0)
+ value.
+
+ Boolean value is represented as "boolean" and its size is 1 byte.
+ Value 0x00 indicates false value and value 0x01 indicates true value.
+
+
+2.4 Attribute Payload
+
+ The Attribute Payload is used to request an attribute, and to reply
+ to the requested attribute. One payload includes one attribute.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Attribute | Attr Flags | Attribute Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Attribute Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+
+Riikonen [Page 4]
+\f
+Internet Draft 15 January 2007
+
+
+ Figure 1: Attribute Payload
+
+
+ o Attribute (1 byte) - Indicates the attribute included in this
+ Attribute Payload.
+
+ o Attribute Flags (1 byte) - Indicates the flags associated
+ with this attribute. The following flags are defined:
+
+ 0x01 ATTRIBUTE_FLAG_INVALID
+
+ The attribute value in Attribute Data is invalid, or
+ unknown. This may be set to indicate that a requested
+ attribute is not available, its value is unknown, or
+ sender does not understand it.
+
+ 0x02 ATTRIBUTE_FLAG_VALID
+
+ The attribute value is included in the Attribute Data.
+
+ When sending this payload to request attributes this value
+ MUST be set to zero (0) value. When sending a reply to the
+ request this field MUST NOT include a zero (0) value.
+
+ o Attribute Length (2 bytes) - Indicates the length of the
+ Attribute Data field, not including any other field.
+
+ o Attribute Data (variable length) - The Attribute Data.
+ The contents of this field is attribute specific, defined
+ subsequently.
+
+
+2.5 Attributes
+
+ The following values can appear in the Attribute field in the
+ Attribute Payload to indicate the content of the attribute. The
+ format of the attribute data is represented as length, type and
+ value. Example:
+
+ Length Type Value
+ 2 bytes integer Some integer value
+ variable string Some string
+ 1 byte boolean Boolean value
+
+ When sending multiple Attribute Payloads it is possible to include
+ multiple same attributes in the packet.
+
+
+
+
+
+Riikonen [Page 5]
+\f
+Internet Draft 15 January 2007
+
+
+ 0 ATTRIBUTE_NONE
+
+ This attribute is reserved and it is never sent.
+
+
+ 1 ATTRIBUTE_USER_INFO
+
+ This attribute includes general information about the user, their
+ name and contact information. The content of this attribute is
+ a VCard version 3.0 as defined in RFC 2426 [RFC2426] and RFC 2425
+ [RFC2425]. Note that some of the information that VCard provides
+ can be also provided in the means of providing other attributes.
+ The rationale for this is that the VCard does not provide all the
+ information, or with the required precision that may be desired in
+ some applications. It is therefore RECOMMENDED that this attribute
+ would be used to provide only basic and constant user information,
+ such as name and contact information, but not online status
+ information.
+
+ Length Type Value
+ variable VCard Basic user information
+
+
+ 2 ATTRIBUTE_SERVICE
+
+ This attribute indicates a service in the Internet that the user
+ is currently using or has logged in. It also shows when the user
+ started using the service, and how long user has been idle in the
+ service. The value of this attribute is as follows:
+
+ Length Type Value
+ 4 bytes integer Service Port (IANA specified)
+ variable string Service Address
+ 1 byte boolean Online status. If this is set to
+ 0x01 (true) it means the user is online
+ in the service. Set to 0x00 (false) when
+ out of reach.
+ variable string Signon date and time, UTC date, format as
+ in ISO 8601
+ 4 bytes integer Idle time
+
+
+ 3 ATTRIBUTE_STATUS_MOOD
+
+ This attribute indicates the mood of the user. It can indicate
+ whether the user is eager to participate in the network. The
+ value of this attribute is as follows:
+
+
+
+
+Riikonen [Page 6]
+\f
+Internet Draft 15 January 2007
+
+
+ Length Type Value
+ 4 bytes integer Mood mask (values ORed together)
+
+ The following mood values are defined:
+
+ 0x00000000 MOOD_NORMAL No specific mood, normal mood
+ 0x00000001 MOOD_HAPPY The user feels happy
+ 0x00000002 MOOD_SAD The user feels sad
+ 0x00000004 MOOD_ANGRY The user feels angry
+ 0x00000008 MOOD_JEALOUS The user feels jealous
+ 0x00000010 MOOD_ASHAMED The user feels ashamed
+ 0x00000020 MOOD_INVINCIBLE The user feels invincible
+ 0x00000040 MOOD_INLOVE The user feels being in love
+ 0x00000080 MOOD_SLEEPY The user feels sleepy
+ 0x00000100 MOOD_BORED The user feels bored
+ 0x00000200 MOOD_EXCITED The user feels excited
+ 0x00000400 MOOD_ANXIOUS The user feels anxious
+
+
+ 4 ATTRIBUTE_STATUS_FREETEXT
+
+ This attribute includes the user's online status free text. It
+ can provide personal status as a text message. The contents of
+ this attribute is a UTF-8 encoded free text string.
+
+ Length Type Value
+ variable string Free text status string
+
+
+ 5 ATTRIBUTE_STATUS_MESSAGE
+
+ This attribute includes the user's online status message. It
+ could provide for example a multi media message showing the status
+ of the user. The contents of this attribute is a MIME object,
+ which can be used to provide for example video, audio, image or
+ other similar status message. It could also provide a reference
+ to the message, for example an URL address.
+
+ Length Type Value
+ variable MIME Status message as MIME object
+
+
+ 6 ATTRIBUTE_PREFERRED_LANGUAGE
+
+ This attribute indicates the preferred language to be used when
+ communicating. The encoding of this attribute is as follows:
+
+ Length Type Value
+
+
+
+Riikonen [Page 7]
+\f
+Internet Draft 15 January 2007
+
+
+ variable string ISO 639-2/T three letter code
+
+
+ 7 ATTRIBUTE_PREFERRED_CONTACT
+
+ This attribute indicates the preferred contact methods. It can
+ indicate the method the user prefers when contacting. The value
+ of this attribute is as follows:
+
+ Length Type Value
+ 4 bytes integer Contact mask (values ORed together)
+
+ The following contact methods are defined:
+
+ 0x00000000 CONTACT_NONE No specific preferred contact method
+ 0x00000001 CONTACT_EMAIL Email is preferred
+ 0x00000002 CONTACT_CALL Phone call is preferred
+ 0x00000004 CONTACT_PAGE Paging is preferred
+ 0x00000008 CONTACT_SMS SMS is preferred
+ 0x00000010 CONTACT_MMS MMS is preferred
+ 0x00000020 CONTACT_CHAT Chatting is preferred
+ 0x00000040 CONTACT_VIDEO Video conferencing is preferred
+
+
+ 8 ATTRIBUTE_TIMEZONE
+
+ This attribute can be used to provide the current local time for
+ the user. The contents of this attribute is a UTF-8 encoded
+ string and the format of the string is UTC time zone defined
+ in the ISO 8601.
+
+ Length Type Value
+ variable string UTC date, format as in ISO 8601
+
+ Note that ATTRIBUTE_USER_INFO may also provide this information.
+ However it is RECOMMENDED that this attribute is used when
+ current time zone information is provided.
+
+
+ 9 ATTRIBUTE_GEOLOCATION
+
+ This attribute can be used to provide measured global location of
+ the user. How this information is gathered is out of scope of
+ this document. The attribute can provide latitude and longitude
+ lateral positions, but also a vertical position. A parameter
+ describing the accuracy of the information can also be provided.
+
+ Length Type Value
+
+
+
+Riikonen [Page 8]
+\f
+Internet Draft 15 January 2007
+
+
+ variable string Longitude (ex. 31 17 14.321W)
+ variable string Latitude (ex. 12 11 21.2N)
+ variable string Altitude
+ variable string Accuracy in meters
+
+ Note that ATTRIBUTE_USER_INFO may also provide this information,
+ however it does not have the vertical position, or the accuracy
+ parameter. It is RECOMMENDED that this attribute is used when
+ providing current global position information.
+
+
+ 10 ATTRIBUTE_DEVICE_INFO
+
+ This attribute includes information about the user's device.
+ The encoding of this attribute is as follows:
+
+ Length Type Value
+ 4 bytes integer Device type
+ variable string Name of the device manufacturer
+ variable string Device version
+ variable string Device model
+ variable string Device language (ISO 639-2/T)
+
+ The following Device types are defined:
+
+ 0 DEVICE_COMPUTER Device is a computer
+ 1 DEVICE_MOBILE_PHONE Device is a mobile phone
+ 2 DEVICE_PDA Device is a PDA
+ 3 DEVICE_TERMINAL Device is a terminal
+
+
+ 11 ATTRIBUTE_EXTENSION
+
+ This attribute indicates that the attribute value is vendor,
+ application or service specific attribute extension. This field
+ MUST include a MIME object, which is the extension value. This
+ document does not specify any explicit MIME objects for this
+ attribute.
+
+ Length Type Value
+ variable MIME Attribute extension as MIME object
+
+
+ 12 ATTRIBUTE_USER_PUBLIC_KEY
+
+ This attribute includes the user's public key or certificate.
+ As the public key and certificate format depends on which sort
+ of algorithm or certificate encoding user is using we need to
+
+
+
+Riikonen [Page 9]
+\f
+Internet Draft 15 January 2007
+
+
+ define a mechanism to differentiate the public key types from
+ each other. This document specifies the most common public keys
+ and certificates. This attribute can be used to deliver the
+ user's public key, and it MUST be present if also the
+ ATTRIBUTE_USER_DIGITAL_SIGNATURE is present. Note that the
+ recipient of this attribute SHOULD verify the public key from
+ a third party, for example from Certification Authority. If
+ there are more than one ATTRIBUTE_USER_PUBLIC_KEY attributes set
+ and ATTRIBUTE_USER_DIGITAL_SIGNATURE is also set, the digital
+ signature SHOULD be verifiable with the first set public key.
+
+ Length Type Value
+ variable string Public key/certificate type
+ variable data Public key/certificate data
+
+ The following public key/certificate types are defined:
+
+ ssh-rsa SSH RSA public key [SSH-TRANS]
+ ssh-dss SSH DSS public key [SSH-TRANS]
+ silc-rsa SILC RSA public key [SILC1]
+ silc-dss SILC DSS public key [SILC1]
+ pgp-sign-rsa OpenPGP RSA certificate [RFC2440]
+ pgp-sign-dss OpenPGP DSS certificate [RFC2440]
+ x509v3-sign-rsa X.509 Version 3 RSA certificate [RFC2459]
+ x509v3-sign-dss X.509 Version 3 DSS certificate [RFC2459]
+
+ Most of these public key/certificate types are equivalent to
+ the types specified for SSH protocol [SSH-TRANS] and are expected
+ to be officially assigned by IANA.
+
+ The encoding of the public key/certificate data in the attribute
+ is done in the manner defined in their respective definitions.
+
+ Note that these public keys are intended for signing. Some
+ certificates may have a key usage restrictions and same key cannot
+ be used for both encryption and signing. Therefore, the name
+ of the certificate type indicates if they are intended for
+ signing only.
+
+
+ 13 ATTRIBUTE_SERVER_PUBLIC_KEY
+
+ This attribute includes a third party server or authority public
+ key or CA certificate and MUST be present if the attribute
+ ATTRIBUTE_SERVER_DIGITAL_SIGNATURE is also present. The format
+ for this attribute is identical to the ATTRIBUTE_USER_PUBLIC_KEY
+ attribute. If there are more than one ATTRIBUTE_SERVER_PUBLIC_KEY
+ attributes set and ATTRIBUTE_SERVER_DIGITAL_SIGNATURE is also set,
+
+
+
+Riikonen [Page 10]
+\f
+Internet Draft 15 January 2007
+
+
+ the digital signature SHOULD be verifiable with the first set public
+ key.
+
+
+ 14 ATTRIBUTE_USER_DIGITAL_SIGNATURE
+
+ This attribute value includes digital signature of all Attribute
+ Payloads except this attribute. This signature can be provided by
+ the user. This attribute SHOULD be last attribute provided in the
+ reply so that it is easier for the receiver to compute the signature
+ data to be verified. The format and encoding of this attribute
+ depends on the public key or certificate used to produce the
+ signature. See the ATTRIBUTE_USER_PUBLIC_KEY for all public keys
+ and certificates that can be used to produce a signature.
+
+ Length Type Value
+ variable data Digital signature data
+
+ The encodings are as follows per public key/certificate type:
+
+ ssh-rsa and ssh-dss Defined in [SSH-TRANS]
+ silc-rsa and silc-dss Defined in [SILC1]
+ pgp-sign-rsa and pgp-sign-dss Defined in [RFC2440]
+ x509v3-sign-rsa and x509v3-sign-dss Defined in [PKCS7]
+
+ The procedure producing the signature and encoding it are done
+ in the manner defined in their respective definitions, see the
+ provided references. Also the hash function used with the
+ signature procedure is defined by the public key/certificate type.
+
+
+ 15 ATTRIBUTE_SERVER_DIGITAL_SIGNATURE
+
+ This attribute value includes digital signature of all Attribute
+ Payloads except this attribute, but including the attribute
+ ATTRIBUTE_USER_DIGITAL_SIGNATURE. This signature can be provided
+ by a third party server or an authority which has verified the
+ information provided by the user. How it verifies this information
+ is out of scope of this document, however it may base its
+ information to a previous registration information and current
+ online status of the user in a service. This attribute SHOULD be
+ last when provided, so that it is easier for the receiver to
+ compute the signature data to be verified. The format for this
+ attribute is identical to the ATTRIBUTE_USER_DIGITAL_SIGNATURE
+ attribute.
+
+
+ 16 ATTRIBUTE_USER_ICON
+
+
+
+Riikonen [Page 11]
+\f
+Internet Draft 15 January 2007
+
+
+ This attribute includes the user's icon or picture that can be
+ associated with the user in the application's user interface.
+ The attribute is a MIME object of which content MUST be one of
+ the MIME image media types.
+
+ Length Type Value
+ variable MIME Icon as MIME image message
+
+
+3 Security Considerations
+
+ The use of these attributes dictates whether the attributes need to
+ be secured or not. However, as the attributes are considered to provide
+ accurate status information about specific user, it is suggested that
+ the attributes would be secured. The attributes should be digitally
+ signed whenever it is possible. Attributes can also be encrypted
+ if it is provided by the protocol using the attributes. A third party,
+ like a server in the network, could also verify the information and provide
+ digital signature in case the information is accurate.
+
+ Even though the attributes would be digitally signed by the sender of
+ the attributes, the information contained in the attribute may still
+ be incorrect. The third party server should not apply digital signature
+ unless it can verify every attribute. The receiver of the attributes
+ should also not trust that the information in fact is correct.
+
+ However, it is possible that the context where these attributes are used
+ the attributes are provided by a party that can provide the accurate
+ information. For example a server in the network could reply to the
+ attributes on behalf of the actual user for some of the attributes.
+
+
+4 References
+
+ [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 2279, January 1998.
+
+ [RFC2425] Howes, T., et al, "A MIME Content-Type for Directory
+ Information", RFC 2425, September 1998.
+
+ [RFC2426] Dawson, F., et al, "vCard MIME Directory Profile",
+ RFC 2426, September 1998.
+
+ [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, January 2007.
+
+
+
+Riikonen [Page 12]
+\f
+Internet Draft 15 January 2007
+
+
+ [RFC2440] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
+ November 1998.
+
+ [RFC2459] Housley, R., et al, "Internet X.509 Public Key
+ Infrastructure, Certificate and CRL Profile", RFC 2459,
+ January 1999.
+
+ [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
+ Internet Draft.
+
+ [PKCS7] Kalinski, B., "PKCS #7: Cryptographic Message Syntax,
+ Version 1.5", RFC 2315, March 1998.
+
+
+
+
+5 Author's Address
+
+ Pekka Riikonen
+ Helsinki
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+6 Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 13]
+\f
--- /dev/null
+
+
+
+
+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-silc-commands-07.txt 15 January 2007
+Expires: 15 July 2007
+
+
+ SILC Commands
+ <draft-riikonen-silc-commands-07.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+Abstract
+
+ This memo describes the commands used in the Secure Internet Live
+ Conferencing (SILC) protocol, specified in the Secure Internet Live
+ Conferencing, Protocol Specification [SILC1]. The SILC Commands are
+ very important part of the SILC protocol. Usually the commands are used
+ by SILC clients to manage the SILC session, but also SILC servers may
+ use the commands. This memo specifies detailed command messages and
+ command reply messages.
+
+
+
+
+
+
+
+
+Table of Contents
+
+
+
+Riikonen [Page 1]
+\f
+Internet Draft 15 January 2007
+
+
+ 1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 2
+ 2 SILC Commands ................................................. 2
+ 2.1 SILC Commands Syntax ...................................... 4
+ 2.2 SILC Command Argument Idioms .............................. 4
+ 2.3 SILC Commands List ........................................ 5
+ 2.4 SILC Command Status Payload ............................... 43
+ 3 SILC Status Types ............................................. 44
+ 4 Security Considerations ....................................... 51
+ 5 References .................................................... 51
+ 6 Author's Address .............................................. 52
+ Appendix A ...................................................... 52
+ Full Copyright Statement ........................................ 54
+
+
+1. Introduction
+
+ This document describes the commands used in the Secure Internet Live
+ Conferencing (SILC) protocol, specified in the Secure Internet Live
+ Conferencing, Protocol Specification [SILC1]. This document specifies
+ detailed command messages and command reply messages.
+
+ Commands are very important part on SILC network especially for client
+ which uses commands to operate on the SILC network. Commands are used
+ to set nickname, join to channel, change modes and many other things.
+
+ See the [SILC1] for the requirements and the restrictions for the usage
+ of the SILC commands. The [SILC2] defines the command packet type and
+ the Command Payload which is actually used to deliver the commands and
+ command reply messages.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+ interpreted as described in [RFC2119].
+
+
+2 SILC Commands
+
+2.1 SILC Commands Syntax
+
+ This section briefly describes the syntax of the command notions
+ in this document. Every field in command is separated from each
+ other by whitespaces (` ') indicating that each field is independent
+ argument and each argument MUST have own Command Argument Payload.
+ The number of maximum arguments are defined with each command
+
+
+
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+
+ separately. The Command Argument Payload is described in [SILC2].
+
+ Every command defines specific number for each argument. Currently,
+ they are defined in ascending order; first argument has number one
+ (1), second has number two (2) and so on. This number is set into the
+ Argument Type field in the Command Argument Payload. This makes it
+ possible to send the arguments in free order as the number MUST be
+ used to identify the type of the argument. This makes is it also
+ possible to have multiple optional arguments in commands and in
+ command replies. The number of argument is marked in parentheses
+ before the actual argument.
+
+
+
+ Example: Arguments: (1) <nickname> (2) <username@host>
+
+
+ Every command replies with Status Payload. This payload tells the
+ sender of the command whether the command was completed successfully or
+ whether there was an error. If error occurred the payload includes the
+ error type. In the next section the Status Payload is not described
+ as it is common to all commands and has been described here. Commands
+ MAY reply with other arguments as well. These arguments are command
+ specific and are described in the next section.
+
+ Example command:
+
+ EXAMPLE_COMMAND
+
+ Max Arguments: 3
+ Arguments: (1) <nickname>[@<server>] (2) <message>
+ (3) [<count>]
+
+ The command has maximum of 3 arguments. However, only first
+ and second arguments are mandatory.
+
+ First argument <nickname> is mandatory but may have optional
+ <nickname@server> format as well. Second argument is mandatory
+ <message> argument. Third argument is optional <count> argument.
+
+ The numbers in parentheses are the argument specific numbers
+ that specify the type of the argument in Command Argument Payload.
+ The receiver always knows that, say, argument number two (2) is
+ <message> argument, regardless of the ordering of the arguments in
+ the Command Payload.
+
+ Reply messages to the command:
+
+
+
+
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+
+
+ Max Arguments: 4
+ Arguments: (1) <Status Payload> (2) [<channel list>]
+ (3) <idle time> (4) [<away message>]
+
+ This command may reply with maximum of 4 arguments. However,
+ only the first and third arguments are mandatory. The numbers
+ in the parentheses have the same meaning as in the upper
+ command sending specification.
+
+ Every command reply with <Status Payload>, it is mandatory
+ argument for all command replies and for this reason it is not
+ described in the command reply descriptions.
+
+
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_NICK
+
+ Every command reply also defines set of status message that it
+ may return inside the <Status Payload>. All status messages
+ are defined in the section 2.3 SILC Command Status Payload
+ The status messages defined with the command are recommendations.
+ It is possible to return other status messages not listed with
+ the command reply definition.
+
+
+2.2 SILC Command Argument Idioms
+
+ All commands that has an ID as argument (for example <Client ID>) are
+ actually ID Payloads, defined in [SILC2] that includes the type of the
+ ID, length of the ID and the actual ID data. This way variable length
+ ID's can be sent as arguments.
+
+ All passphrases that may be sent in commands as arguments MUST be
+ UTF-8 [RFC3629] encoded. All strings sent as arguments in command and
+ command reply are also UTF-8 encoded, unless otherwise defined. See
+ the [SILC1] for general UTF-8 definition in SILC protocol.
+
+ All public keys and certificates that are sent as arguments are actually
+ Public Key Payloads [SILC2]. This way it is possible to send different
+ kind of public keys and certificate types as arguments.
+
+
+
+
+
+
+
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+
+2.3 SILC Commands List
+
+ This section lists all SILC commands, however, it is expected that a
+ implementation and especially client implementation has many more
+ commands that has only local affect. These commands are official
+ SILC commands that has both client and server sides and cannot be
+ characterized as local commands.
+
+ List of all defined commands in SILC follows.
+
+ 0 SILC_COMMAND_NONE
+
+ None. This is reserved command and MUST NOT be sent.
+
+
+ 1 SILC_COMMAND_WHOIS
+
+ Max Arguments: 256
+ Arguments: (1) [<nickname>[@<server>]] (2) [<count>]
+ (3) [<Requested Attributes>] (4) [<Client ID>]
+ (n) [...]
+
+ Whois command is used to query various information about specific
+ user. The user may be requested by their nickname and server name.
+ The query may find multiple matching users as there are no unique
+ nicknames in the SILC. The <count> option may be given to narrow
+ down the number of accepted results. If this is not defined there
+ are no limit of accepted results. The query may also be narrowed
+ down by defining the server name of the nickname. The <count> is
+ 32 bit MSB first order integer.
+
+ It is also possible to search the user by Client ID. If the
+ <Client ID> is provided server MUST use it as the search value
+ instead of the <nickname>. It is also possible to define multiple
+ Client ID's to search multiple users sending only one WHOIS
+ command. In this case the Client ID's are appended as normal
+ arguments.
+
+ The <Requested Attributes> is defined in [ATTRS] and can be used
+ to request various information about the client. See Appendix A
+ for definition of using these attributes in SILC. If neither the
+ <nickname> or <Client ID> arguments are present but the attributes
+ are, the server MUST use the attributes to do the searching. If
+ none of the arguments, <nickname>, <Client ID> and <Requested
+ Attributes> are present, error MUST be retuned. Server MAY
+ use the <Requested Attributes> to narrow down the search if they
+ present at any time.
+
+
+
+
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+
+ To prevent miss-use of this command wildcards in the nickname
+ or in the server name are not permitted. It is not allowed
+ to request all users on some server. The WHOIS requests MUST
+ be based on explicit nickname request.
+
+ The WHOIS request MUST be always sent to the router by normal
+ server so that all users are searched. However, the server still
+ MUST search its locally connected clients. The router MUST send
+ this command to the server which owns the requested client, if
+ the router is unable to provide all mandatory information about
+ the client. That server MUST reply to the command. Server MUST
+ NOT send whois replies to the client until it has received the
+ reply from its router.
+
+ Reply messages to the command:
+
+ Max Arguments: 11
+ Arguments: (1) <Status Payload> (2) <Client ID>
+ (3) <nickname>[@<server>] (4) <username@host>
+ (5) <real name> (6) [<Channel Payload
+ list>]
+ (7) [<user mode>] (8) [<idle time>]
+ (9) [<fingerprint>] (10) <channel user
+ mode list>
+ (11) [<Attributes>]
+
+
+ This command may reply with several command reply messages to
+ form a list of results. In this case the status payload will
+ include STATUS_LIST_START status in the first reply and
+ STATUS_LIST_END in the last reply to indicate the end of the
+ list. If there are only one reply the status is set to normal
+ STATUS_OK. If multiple Client IDs was requested then each found
+ and unfound client MUST cause successful or error reply,
+ respectively.
+
+ The command replies include the Client ID of the nickname,
+ nickname and server name, user name and host name and user's real
+ name. Client should process these replies only after the last
+ reply has been received with the STATUS_LIST_END status. If the
+ <count> option were defined in the query there will be only
+ <count> many replies from the server.
+
+ The server returns the list of channels if the client has
+ joined channels. In this case the list is list of Channel
+ Payloads. The Mode Mask in the Channel Payload is the channel's
+ mode. The list is encoded by adding the Channel Payloads one
+ after the other. Private and secret channels MUST NOT be sent,
+
+
+
+Riikonen [Page 6]
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+
+
+ except if the sender of this command is on those channels, or
+ the sender is server. The <channel user mode list> MUST also
+ be sent if client is joined channels. This list includes 32 bit
+ MSB first order values one after the other and each indicate
+ the user's mode on a channel. The order of these values MUST
+ be same as the channel order in the <Channel Payload list>.
+
+ The server also returns client's user mode, idle time, and the
+ fingerprint of the client's public key. The <fingerprint> is the
+ binary hash digest of the public key. The fingerprint MUST NOT
+ be sent if the server has not verified the proof of possession of
+ the corresponding private key. Server can do this during the
+ SILC Key Exchange protocol. The <fingerprint> is SHA1 digest.
+
+ The <Attributes> is the reply to the <Requested Attributes>.
+ See the Appendix A for more information.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_LIST_START
+ SILC_STATUS_LIST_END
+ SILC_STATUS_ERR_NO_SUCH_NICK
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+
+
+ 2 SILC_COMMAND_WHOWAS
+
+ Max Arguments: 2
+ Arguments: (1) <nickname>[@<server>] (2) [<count>]
+
+ Whowas. This command is used to query history information about
+ specific user. The user may be requested by their nickname and
+ server name. The query may find multiple matching users as there
+ are no unique nicknames in the SILC. The <count> option may be
+ given to narrow down the number of accepted results. If this
+ is not defined there are no limit of accepted results. The query
+ may also be narrowed down by defining the server name of the
+ nickname. The <count> is 32 bit MSB first order integer.
+
+ To prevent miss-use of this command wildcards in the nickname
+ or in the server name are not permitted. The WHOWAS requests MUST
+ be based on specific nickname request.
+
+ The WHOWAS request MUST be always sent to the router by server
+
+
+
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+
+ so that all users are searched. However, the server still must
+ search its locally connected clients.
+
+ Reply messages to the command:
+
+ Max Arguments: 5
+ Arguments: (1) <Status Payload> (2) <Client ID>
+ (3) <nickname>[@<server>] (4) <username@host>
+ (5) [<real name>]
+
+ This command may reply with several command reply messages to form
+ a list of results. In this case the status payload will include
+ STATUS_LIST_START status in the first reply and STATUS_LIST_END in
+ the last reply to indicate the end of the list. If there are only
+ one reply the status is set to normal STATUS_OK.
+
+ The command replies with nickname and user name and host name.
+ Every server MUST keep history for some period of time of its
+ locally connected clients.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_LIST_START
+ SILC_STATUS_LIST_END
+ SILC_STATUS_ERR_NO_SUCH_NICK
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+
+
+ 3 SILC_COMMAND_IDENTIFY
+
+ Max Arguments: 256
+ Arguments: (1) [<nickname>[@<server>]] (2) [<server name>]
+ (3) [<channel name>] (4) [<count>]
+ (5) [<ID Payload>] (n) [...]
+
+ Identify command is used to query information about an entity by
+ the entity's name or ID. This command can be used to query
+ information about clients, servers and channels.
+
+ The query may find multiple matching entities. The <count> option
+ may be given to narrow down the number of accepted results. If
+ this is not defined there are no limit of accepted results. The
+ <count> is 32 bit MSB first order integer.
+
+ It is also possible to search the entity by its ID. If the
+
+
+
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+
+ <ID Payload> is provided server must use it as the search value
+ instead of the entity's name. One of the arguments MUST be given.
+ It is also possible to define multiple ID Payloads to search
+ multiple entities sending only one IDENTIFY command. In this case
+ the ID Payloads are appended as normal arguments. The type of the
+ entity is defined by the type of the ID Payload.
+
+ To prevent miss-use of this command wildcards in the names are
+ not permitted. It is not allowed to request for example all users
+ on server.
+
+ Implementations may not want to give interface access to this
+ command as it is hardly a command that would be used by an end
+ user. However, it must be implemented as it is most likely used
+ with private message sending.
+
+ The IDENTIFY command MUST be always sent to the router by server
+ so that all users are searched. However, server MUST still search
+ its locally connected clients.
+
+ Reply messages to the command:
+
+ Max Arguments: 4
+ Arguments: (1) <Status Payload> (2) <ID Payload>
+ (3) [<entity's name>] (4) [<info>]
+
+ This command may reply with several command reply messages to form
+ a list of results. In this case the status payload will include
+ STATUS_LIST_START status in the first reply and STATUS_LIST_END in
+ the last reply to indicate the end of the list. If there are only
+ one reply the status is set to normal STATUS_OK. If multiple Client
+ IDs was requested then each found and unfound client must cause
+ successful or error reply, respectively.
+
+ When querying clients the <entity's name> must include the client's
+ nickname in the following format: nickname[@server]. The
+ <info> must include the client's username and host in the following
+ format: username@host.
+
+ When querying servers the <entity's name> must include the server's
+ full name. The <info> may be omitted.
+
+ When querying channels the <entity's name> must include the
+ channel's name. The <info> may be omitted.
+
+ If the <count> option were defined in the query there will be only
+ <count> many replies from the server.
+
+
+
+
+Riikonen [Page 9]
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+Internet Draft 15 January 2007
+
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_LIST_START
+ SILC_STATUS_LIST_END
+ SILC_STATUS_ERR_NO_SUCH_NICK
+ SILC_STATUS_ERR_NO_SUCH_SERVER
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+
+
+ 4 SILC_COMMAND_NICK
+
+ Max Arguments: 1
+ Arguments: (1) <nickname>
+
+ Set/change nickname. This command is used to set nickname for
+ user. See [SILC1] for definition of correctly formatted
+ nickname.
+
+ When nickname is changed new Client ID is generated. Server MUST
+ distribute SILC_NOTIFY_TYPE_NICK_CHANGE to local clients on the
+ channels (if any) the client is joined on. Then it MUST send
+ SILC_NOTIFY_TYPE_NICK_CHANGE notify to its primary route to
+ notify about nickname and Client ID change.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <New ID Payload>
+ (3) <nickname>
+
+ This command replies always with <New ID Payload> that is
+ generated by the server every time user changes their nickname.
+ Client receiving this payload MUST start using the received
+ Client ID as its current valid Client ID. The New ID Payload
+ is described in [SILC2]. The <nickname> is the user's new
+ nickname.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_WILDCARDS
+
+
+
+Riikonen [Page 10]
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+Internet Draft 15 January 2007
+
+
+ SILC_STATUS_ERR_NICKNAME_IN_USE
+ SILC_STATUS_ERR_BAD_NICKNAME
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+
+
+ 5 SILC_COMMAND_LIST
+
+ Max Arguments: 1
+ Arguments: (1) [<Channel ID>]
+
+ The list command is used to list channels and their topics on the
+ current server. If the <Channel ID> parameter is used, only the
+ status of that channel is displayed. Secret channels are not
+ listed at all. Private channels are listed with status indicating
+ that the channel is private. Router MAY reply with all channels
+ it knows about.
+
+ Reply messages to the command:
+
+ Max Arguments: 5
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) <channel> (4) [<topic>]
+ (5) [<user count>]
+
+ This command may reply with several command reply messages to form
+ a list of results. In this case the status payload will include
+ STATUS_LIST_START status in the first reply and STATUS_LIST_END in
+ the last reply to indicate the end of the list. If there are only
+ one reply the status is set to normal STATUS_OK.
+
+ This command replies with Channel ID, name and the topic of the
+ channel. If the channel is private channel the <topic> SHOULD
+ include the "*private*" string.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_LIST_START
+ SILC_STATUS_LIST_END
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_NO_SUCH_SERVER
+
+
+
+
+Riikonen [Page 11]
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+Internet Draft 15 January 2007
+
+
+ 6 SILC_COMMAND_TOPIC
+
+ Max Arguments: 2
+ Arguments: (1) <Channel ID> (2) [<topic>]
+
+ This command is used to change or view the topic of a channel.
+ The topic for channel <Channel ID> is returned if there is no
+ <topic> given. If the <topic> parameter is present, the topic
+ for that channel will be changed, if the channel modes permit
+ this action.
+
+ After setting the topic the server MUST send the notify type
+ SILC_NOTIFY_TYPE_TOPIC_SET to its primary router and then to
+ the channel which topic was changed.
+
+ Reply messages to the command:
+
+ Max Arguments: 2
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) [<topic>]
+
+ The command may reply with the topic of the channel if it is
+ set.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ON_CHANNEL
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_BAD_CHANNEL_ID
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_CHANNEL_PRIV
+
+
+ 7 SILC_COMMAND_INVITE
+
+ Max Arguments: 4
+ Arguments: (1) <Channel ID> (2) [<Client ID>]
+ (3) [<add | del>] (4) [<invite list>]
+
+ This command can be used to invite other clients to join to a
+ channel, and to manage the channel's invite list. The <Client
+ ID> argument is the target client's ID that is being invited.
+
+
+
+Riikonen [Page 12]
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+
+ The <Channel ID> is the Channel ID of the requested channel.
+ The sender of this command MUST be on the channel. The server
+ MUST also send the notify type SILC_NOTIFY_TYPE_INVITE to its
+ primary router and then to the client indicated by the <Client
+ ID>.
+
+ The <add | del> is an argument of size of 1 byte where 0x00 means
+ adding a client to invite list, and 0x01 means deleting a client
+ from invite list. The <invite list>, if present, indicates
+ the information to be added to or removed from the invite list.
+ It may include a string for matching clients, public key of a
+ client (Public Key Payload) or Client ID of a client. The
+ <invite list> is an Argument List Payload.
+
+ The following Argument Types has been defined for invite list
+ Argument Payloads:
+
+ 0x01 - Argument is an invite string of following format:
+
+ [<nickname>[@<server>]!][<username>]@[<hostname or IP/MASK>]
+
+ The <hostname> may also be in format of IP/MASK to indicate
+ a network, for example 10.2.1.0/255.255.0.0.
+
+ 0x02 - Argument is the public key of a client
+ 0x03 - Argument is the Client ID of a client
+
+ If unknown type value is received or there is invalid amount of
+ Argument Payloads present in the list, the command MUST be
+ discarded. When argument that is to be deleted from the invite
+ list does not exist in the list the argument is ignored.
+
+ When adding to or removing from the invite list the server MUST
+ send the notify type SILC_NOTIFY_TYPE_INVITE to its primary router.
+ When the SILC_CHANNEL_MODE_INVITE is set the client which executes
+ this command MUST have at least channel operator privileges to be
+ able to add to or remove from the invite list. If this channel
+ mode is not set the list manipulation is allowed for all clients.
+ Wildcards MAY be used with this command. When this command is
+ used to invite explicit client with <Client ID> the ID MUST be
+ added to the invite list by the server.
+
+ When this command is given with only <Channel ID> argument then
+ the command merely returns the invite list of the channel. This
+ command MUST fail if the requested channel does not exist, the
+ requested <Client ID> is already on the channel or if the channel
+ is invite only channel and the caller of this command does not
+ have at least channel operator privileges on the channel.
+
+
+
+Riikonen [Page 13]
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+Internet Draft 15 January 2007
+
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) [<invite list>]
+
+ This command replies with the invite list of the channel if it
+ exists.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_NO_CLIENT_ID
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_NOT_ON_CHANNEL
+ SILC_STATUS_ERR_USER_ON_CHANNEL
+ SILC_STATUS_ERR_NO_CHANNEL_PRIV
+ SILC_STATUS_ERR_RESOURCE_LIMIT
+
+
+ 8 SILC_COMMAND_QUIT
+
+ Max Arguments: 1
+ Arguments: (1) [<quit message>]
+
+ This command is used by client to end SILC session. The server
+ must close the connection to a client which sends this command.
+ if <quit message> is given it will be sent to other clients on
+ channel if the client is on channel when quitting.
+
+ Reply messages to the command:
+
+ This command does not reply anything.
+
+
+ 9 SILC_COMMAND_KILL
+
+ Max Arguments: 3
+ Arguments: (1) <Client ID> (2) [<comment>]
+ (3) [<auth payload>]
+
+ This command can be used by SILC operators to remove a client from
+ SILC network. It also can be used by a normal client to remove
+
+
+
+Riikonen [Page 14]
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+Internet Draft 15 January 2007
+
+
+ its own client from network by providing correct authentication
+ data.
+
+ Router operator killing a client:
+
+ The removing has temporary effects and client may reconnect to
+ SILC network. The <Client ID> is the client to be removed from SILC.
+ The <comment> argument may be provided to give to the removed client
+ some information why it was removed from the network. The killer
+ MUST have SILC operator privileges.
+
+ When killing a client the router MUST first send notify type
+ SILC_NOTIFY_TYPE_KILLED to all channels the client has joined.
+ The packet MUST NOT be sent to the killed client on the channels.
+ Then, the router MUST send the same notify type to its primary
+ router. Finally, the router MUST send the same notify type
+ destined directly to the client which was killed. The killed
+ client MUST also be removed from the invite lists of joined
+ channels if it is explicitly added in the invite lists.
+
+ Normal client killing by authentication:
+
+ When normal client executes this command the <Client ID> is the
+ destination client to be removed from the network. The client
+ MUST provide the <auth payload> which includes a digital signature
+ that MUST be verified with the public key of the client indicated
+ by <Client ID>. The <Client ID> MUST be local client to the server.
+ If the signature verification is successful the server sends
+ SILC_NOTIFY_TYPE_SIGNOFF to network and to the destination client.
+ The SILC_NOTIFY_TYPE_KILLED MUST NOT be used in this case. If the
+ verification fails the destination client remains in network.
+ The hash function used in <auth payload> computing is selected
+ by user or SHA1 otherwise.
+
+ Reply messages to the command:
+
+ Max Arguments: 2
+ Arguments: (1) <Status Payload> (2) <Client ID>
+
+ This command returns with the requested Client ID.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+
+
+
+Riikonen [Page 15]
+\f
+Internet Draft 15 January 2007
+
+
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_NO_CLIENT_ID
+ SILC_STATUS_ERR_NO_ROUTER_PRIV
+
+
+ 10 SILC_COMMAND_INFO
+
+ Max Arguments: 2
+ Arguments: (1) [<server>] (2) [<Server ID>]
+
+ This command is used to fetch various information about a server.
+ If <server> argument is specified the command MUST be sent to
+ the requested server.
+
+ If the <Server ID> is specified the server information if fetched
+ by the provided Server ID. One of the arguments MUST always be
+ present.
+
+ Reply messages to the command:
+
+ Max Arguments: 4
+ Arguments: (1) <Status Payload> (2) <Server ID>
+ (3) <server name> (4) <string>
+
+ This command replies with the Server ID of the server and a
+ string which tells the information about the server.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_SERVER
+ SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+ SILC_STATUS_ERR_NO_SERVER_ID
+
+
+ 11 SILC_COMMAND_STATS
+
+ Max Arguments: 1
+ Arguments: (1) <Server ID>
+
+ This command is used to fetch various statistical information
+ from the server indicated by <Server ID>, which is the ID of
+ server where sender is connected to. Server receiving this
+ command MAY also send this further to its router for fetching
+
+
+
+Riikonen [Page 16]
+\f
+Internet Draft 15 January 2007
+
+
+ other cell and network wide statistics to accompany the reply.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <Server ID>
+ (3) [<statistics structure>]
+
+ This command replies with the Server ID of the server and
+ optional statistics structure which includes 32 bit MSB first
+ ordered integer values to represent various statistical
+ information. The structure is as follows:
+
+ starttime - time when server was started
+ uptime - uptime of the server
+ my clients - number of locally connected clients
+ my channels - number of locally created channels
+ my server ops - number of local server operators
+ my router ops - number of local router operators
+ cell clients - number of clients in local cell
+ cell channels - number of channels in local cell
+ cell servers - number of servers in local cell
+ clients - number of client in SILC network
+ channels - number of channels in SILC network
+ servers - number of servers in SILC network
+ routers - number of routers in SILC network
+ server ops - number of server operators in SILC network
+ router ops - number of router operators in SILC network
+
+ If some value is unknown it is set to zero (0) value. The
+ "starttime" is the start time of the server, and is seconds
+ since Epoch (POSIX.1). The "uptime" is time difference of
+ current time and "starttime" in the server, and is seconds
+ in value.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+ SILC_STATUS_ERR_NO_SUCH_SERVER
+ SILC_STATUS_ERR_NO_SERVER_ID
+
+
+ 12 SILC_COMMAND_PING
+
+
+
+
+Riikonen [Page 17]
+\f
+Internet Draft 15 January 2007
+
+
+ Max Arguments: 1
+ Arguments: (1) <Server ID>
+
+ This command is used by client and server to test the communication
+ channel to its server if one suspects that the communication is not
+ working correctly. The <Server ID> is the ID of the server the
+ sender is connected to.
+
+ Reply messages to the command:
+
+ Max Arguments: 1
+ Arguments: (1) <Status Payload>
+
+ This command replies only with Status Payload. Server returns
+ SILC_STATUS_OK in Status Payload if pinging was successful.
+
+
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SERVER_ID
+ SILC_STATUS_ERR_NO_SUCH_SERVER
+ SILC_STATUS_ERR_NOT_REGISTERED
+
+
+ 13 SILC_COMMAND_OPER
+
+ Max Arguments: 2
+ Arguments: (1) <username> (2) <authentication payload>
+
+ This command is used by normal client to obtain server operator
+ privileges on some server or router. Note that router operator
+ has router privileges that supersedes the server operator
+ privileges and this does not obtain those privileges. Client
+ MUST use SILCOPER command to obtain router level privileges.
+
+ The <username> is the username set in the server configurations
+ as operator. The <authentication payload> is the data that the
+ client is authenticated against. It may be passphrase prompted
+ for user on client's screen or it may be public key authentication
+ based on digital signatures. The public key used to verify the
+ signature should be locally saved in the server, and server should
+ not use public key received during the SKE to verify this signature.
+
+ After changing the mode the server MUST send the notify type
+
+
+
+Riikonen [Page 18]
+\f
+Internet Draft 15 January 2007
+
+
+ SILC_NOTIFY_TYPE_UMODE_CHANGE to its primary router.
+
+ Reply messages to the command:
+
+ Max Arguments: 1
+ Arguments: (1) <Status Payload>
+
+ This command replies only with Status Payload.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_AUTH_FAILED
+
+
+ 14 SILC_COMMAND_JOIN
+
+ Max Arguments: 7
+ Arguments: (1) <channel> (2) <Client ID>
+ (3) [<passphrase>] (4) [<cipher>]
+ (5) [<hmac>] (6) [<founder auth>]
+ (7) [<channel auth>]
+
+ Join to channel/create new channel. This command is used to
+ join to a channel. If the channel does not exist the channel is
+ created. If server is normal server this command MUST be sent
+ to router which will create the channel. The channel MAY be
+ protected with passphrase. If this is the case the passphrase
+ MUST be sent along the join command. See the [SILC1] for
+ definition of correctly formatted channel name, <channel>.
+
+ The second argument <Client ID> is the Client ID of the client
+ which is joining to the client. When client sends this command
+ to the server the <Client ID> MUST be the client's own ID.
+
+ Cipher to be used to secure the traffic on the channel MAY be
+ requested by sending the name of the requested <cipher>. This
+ is used only if the channel does not exist and is created. If
+ the channel already exists the cipher set previously for the
+ channel will be used to secure the traffic. The computed MACs
+ of the channel message are produced by the default HMAC or by
+ the <hmac> provided for the command.
+
+ The <founder auth> is Authentication Payload providing the
+ authentication for gaining founder privileges on the channel
+
+
+
+Riikonen [Page 19]
+\f
+Internet Draft 15 January 2007
+
+
+ when joining the channel. The client may provide this if it
+ knows that it is the founder of the channel and that the
+ SILC_CMODE_FOUNDER_AUTH mode is set on the channel. The server
+ MUST verify whether the client is able to gain the founder
+ privileges the same way as the client had given the
+ SILC_COMMAND_CUMODE command to gain founder privileges. The
+ client is still able to join the channel even if the founder
+ privileges could not be gained. The hash function used with
+ the <founder payload> is selected by user or SHA1 otherwise.
+
+ If the <channel auth> is present and the channel mode
+ SILC_CMODE_CHANNEL_AUTH is set the server MUST verify the
+ <channel auth> with channel public key(s). If public key that
+ can verify <channel auth> does not exist on the channel public
+ key list the client MUST NOT be allowed to join the channel.
+ Because more than one public key may be set on channel the
+ <channel auth> Authentication Payload's Public Data field
+ MUST include an indication of the public key to be used. The
+ first 20 bytes of the Public Data field MUST be SHA-1 digest of
+ the public key that must be used in verification. The digest
+ is the SILC Public Key fingerprint. Rest of thePublic Data field
+ are set as defined in [SILC1]. This way server can determine from
+ the digest whether that public key exist on the channel and then
+ use that key in verification. The hash function used with
+ <channel auth> is selected by user or SHA1 otherwise.
+
+ The server MUST check whether the user is allowed to join to
+ the requested channel. Various modes set to the channel affect
+ the ability of the user to join the channel. These conditions
+ are:
+
+ o The user MUST be invited to the channel if the channel
+ is invite-only channel.
+
+ o The Client ID/nickname/username/host name/public key
+ MUST NOT match any active bans.
+
+ o The correct passphrase MUST be provided if passphrase
+ is set to the channel, and/or digital signature verification
+ with channel public key MUST be successful if public keys
+ has been set to the channel.
+
+ o The user count limit, if set, MUST NOT be reached.
+
+ If the client provided correct <founder auth> payload it can
+ override these conditions, except the condition for the passphrase.
+ The correct passphrase MUST be provided even if <founder auth>
+ payload is provided.
+
+
+
+Riikonen [Page 20]
+\f
+Internet Draft 15 January 2007
+
+
+ Reply messages to the command:
+
+ Max Arguments: 17
+ Arguments: (1) <Status Payload> (2) <channel>
+ (3) <Channel ID> (4) <Client ID>
+ (5) <channel mode mask> (6) <created>
+ (7) [<Channel Key Payload>] (8) [<ban list>]
+ (9) [<invite list>] (10) [<topic>]
+ (11) [<hmac>] (12) <list count>
+ (13) <Client ID list> (14) <client mode list>
+ (15) [<founder pubkey>] (16) [<channel pubkeys>]
+ (17) [<user limit>]
+
+ This command replies with the channel name requested by the
+ client, channel ID of the channel and topic of the channel
+ if it exists. The <Client ID> is the Client ID which was joined
+ to the channel. It also replies with the channel mode mask
+ which tells all the modes set on the channel. If the channel
+ is created the mode mask is zero (0) and <created> is 0x01.
+ If ban mask and/or invite list is set they are sent as well.
+ The <user limit> is the user limit on the channel, if one is set.
+
+ The <list count>, <Client ID list> and <client mode list> are
+ the clients currently on the channel and their modes on the
+ channel. The <Client ID list> is formed by adding the ID Payloads
+ one after the other. The <client mode list> is formed by adding
+ 32 bit MSB first order values one after the other. The <founder
+ pubkey> is the public key (or certificate) of the channel founder.
+ The <channel pubkeys> is Argument List Payload containing the
+ channel public keys that has been set for the channel.
+
+ Client receives the channel key in the reply message as well
+ inside <Channel Key Payload>.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_BAD_PASSWORD
+ SILC_STATUS_ERR_CHANNEL_IS_FULL
+ SILC_STATUS_ERR_NOT_INVITED
+ SILC_STATUS_ERR_BANNED_FROM_CHANNEL
+ SILC_STATUS_ERR_BAD_CHANNEL
+ SILC_STATUS_ERR_USER_ON_CHANNEL
+
+
+
+
+Riikonen [Page 21]
+\f
+Internet Draft 15 January 2007
+
+
+ 15 SILC_COMMAND_MOTD
+
+ Max Arguments: 1
+ Arguments: (1) <server>
+
+ This command is used to query the Message of the Day of the server.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <Server ID>
+ (3) [<motd>]
+
+ This command replies with the motd message if it exists.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NO_SUCH_SERVER
+
+
+ 16 SILC_COMMAND_UMODE
+
+ Max Arguments: 2
+ Arguments: (1) <Client ID> (2) [<client mode mask>]
+
+ This command is used by client to set/unset modes for itself.
+ However, there are some modes that the client MUST NOT set itself,
+ but they will be set by server. However, client MAY unset any
+ mode. Modes may be masked together ORing them thus having
+ several modes set. Client MUST keep its client mode mask
+ locally so that the mode setting/unsetting would work without
+ problems. Client may change only its own modes.
+
+ After changing the mode server MUST send the notify type
+ SILC_NOTIFY_TYPE_UMODE_CHANGE to its primary router.
+
+ The following client modes are defined:
+
+ 0x00000000 SILC_UMODE_NONE
+
+ No specific mode for client. This is the initial
+ setting when new client is created. The client is
+ normal client and is present in the network.
+
+
+
+
+Riikonen [Page 22]
+\f
+Internet Draft 15 January 2007
+
+
+ 0x00000001 SILC_UMODE_SERVER_OPERATOR
+
+ Marks the user as server operator. Client MUST NOT
+ set this mode itself. Server sets this mode to the
+ client when client attains the server operator
+ privileges by SILC_COMMAND_OPER command. Client
+ MAY unset the mode itself.
+
+
+ 0x00000002 SILC_UMODE_ROUTER_OPERATOR
+
+ Marks the user as router (SILC) operator. Client
+ MUST NOT set this mode itself. Router sets this mode
+ to the client when client attains the router operator
+ privileges by SILC_COMMAND_SILCOPER command. Client
+ MAY unset the mode itself.
+
+
+ 0x00000004 SILC_UMODE_GONE
+
+ Marks that the user is not currently present in the
+ SILC Network. Client MAY set and unset this mode.
+
+
+ 0x00000008 SILC_UMODE_INDISPOSED
+
+ Marks that the user is currently indisposed and may
+ not be able to receive any messages, and that user may
+ not be present in the network. Client MAY set and
+ unset this mode.
+
+
+ 0x00000010 SILC_UMODE_BUSY
+
+ Marks that the user is currently busy and may not
+ want to receive any messages, and that user may not
+ be present in the network. Client MAY set and unset
+ this mode.
+
+
+ 0x00000020 SILC_UMODE_PAGE
+
+ User is not currently present or is unable to receive
+ messages, and prefers to be paged in some mechanism
+ if the user needs to be reached. Client MAY set and
+ unset this mode.
+
+
+
+
+
+Riikonen [Page 23]
+\f
+Internet Draft 15 January 2007
+
+
+ 0x00000040 SILC_UMODE_HYPER
+
+ Marks that the user is hyper active and is eager to
+ receive and send messages. Client MAY set and unset
+ this mode.
+
+
+ 0x00000080 SILC_UMODE_ROBOT
+
+ Marks that the client is actually a robot program.
+ Client MAY set and unset this mode.
+
+
+ 0x00000100 SILC_UMODE_ANONYMOUS
+
+ Marks that the client is anonymous client. Server
+ that specifically is designed for anonymous services
+ can set and unset this mode. Client MUST NOT set or
+ unset this mode itself. A client with this mode set
+ would have the username and the hostname information
+ scrambled by the server which set this mode.
+
+
+ 0x00000200 SILC_UMODE_BLOCK_PRIVMSG
+
+ Marks that the client wishes to block private
+ messages sent to the client, unless the Private
+ Message Key flag is set in the SILC packet header.
+ If this mode is set server MUST NOT deliver private
+ messages to the client without the Private Message
+ Key flag being set. The Private Message Key flag set
+ indicates that the private message is protected with
+ a key shared between the sender and the recipient.
+
+ A separate service could provide additional filtering
+ features for accepting private messages from certain
+ sender. However, this document does not specify such
+ service.
+
+ The client MAY set and unset this mode.
+
+
+ 0x00000400 SILC_UMODE_DETACHED
+
+ Marks that the client is detached from the SILC network.
+ This means that the actual network connection to the
+ client is lost but the client entry is still valid. The
+ detached client can be resumed at a later time. This
+
+
+
+Riikonen [Page 24]
+\f
+Internet Draft 15 January 2007
+
+
+ mode MUST NOT be set by client. It can only be set when
+ client has issued command SILC_COMMAND_DETACH. The server
+ sets this mode. This mode cannot be unset with this
+ command. It is unset when the client is resuming back to
+ the network and SILC_PACKET_RESUME_CLIENT packet is
+ received.
+
+ This flag MUST NOT be used to determine whether a packet
+ can be sent to the client or not. Only the server that
+ had the original client connection can make the decision
+ by knowing that the network connection is not active.
+ In this case the default case is to discard the packet.
+
+
+ 0x00000800 SILC_UMODE_REJECT_WATCHING
+
+ Marks that the client rejects that it could be watched
+ by someone else. If this mode is set notifications about
+ this client is not send, even if someone is watching the
+ same nickname this client has. Client MAY set and unset
+ this mode. Any changes for this client MUST NOT be
+ notified to any watcher when this mode is set.
+
+ A separate service could provide additional filtering
+ features for rejecting and accepting the watching from
+ certain users. However, this document does not specify
+ such service.
+
+
+ 0x00001000 SILC_UMODE_BLOCK_INVITE
+
+ Marks that the client wishes to block incoming invite
+ notifications. Client MAY set and unset this mode.
+ When set server does not deliver invite notifications
+ to the client. Note that this mode may make it harder
+ to join invite-only channels.
+
+ If the <client mode mask> was not provided this command merely
+ returns the mode mask to the client.
+
+
+ Reply messages to the command:
+
+ Max Arguments: 2
+ Arguments: (1) <Status Payload> (2) <client mode mask>
+
+ This command replies with the changed client mode mask that
+ the client MUST to keep locally.
+
+
+
+Riikonen [Page 25]
+\f
+Internet Draft 15 January 2007
+
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_BAD_CLIENT_ID
+ SILC_STATUS_ERR_NOT_YOU
+ SILC_STATUS_ERR_PERM_DENIED
+ SILC_STATUS_ERR_UNKNOWN_MODE
+ SILC_STATUS_ERR_NO_CLIENT_ID
+
+
+ 17 SILC_COMMAND_CMODE
+
+ Max Arguments: 9
+ Arguments: (1) <Channel ID> (2) [<channel mode mask>]
+ (3) [<user limit>] (4) [<passphrase>]
+ (5) [<cipher>] (6) [<hmac>]
+ (7) [<auth payload>] (8) [<founder pubkey>]
+ (9) [<channel pubkey>]
+
+ This command is used by client to set or change channel flags on
+ a channel. Channel has several modes that set various properties
+ of a channel. Modes may be masked together by ORing them thus
+ having several modes set. The <Channel ID> is the ID of the
+ target channel. The client changing channel mode MUST be on
+ the same channel and posses sufficient privileges to be able to
+ change the mode.
+
+ When the mode is changed SILC_NOTIFY_TYPE_CMODE_CHANGE notify
+ type MUST be distributed to the channel.
+
+ The following channel modes are defined:
+
+ 0x00000000 SILC_CMODE_NONE
+
+ No specific mode on channel. This is the default when
+ channel is created. This means that channel is just plain
+ normal channel.
+
+
+ 0x00000001 SILC_CMODE_PRIVATE
+
+ Channel is private channel. Private channels are shown
+ in the channel list listed with SILC_COMMAND_LIST command
+ with indication that the channel is private. Also,
+
+
+
+Riikonen [Page 26]
+\f
+Internet Draft 15 January 2007
+
+
+ client on private channel will no be detected to be on
+ the channel as the channel is not shown in the client's
+ currently joined channel list. Channel founder and
+ channel operator MAY set/unset this mode.
+
+
+ 0x00000002 SILC_CMODE_SECRET
+
+ Channel is secret channel. Secret channels are not shown
+ in the list listed with SILC_COMMAND_LIST command. Secret
+ channels can be considered to be invisible channels.
+ Channel founder and channel operator MAY set/unset this
+ mode.
+
+
+ 0x00000004 SILC_CMODE_PRIVKEY
+
+ Channel uses private channel key to protect the traffic
+ on the channel. When this mode is set the client will be
+ responsible to set the key it wants to use to encrypt and
+ decrypt the traffic on channel. Server generated channel
+ keys are not used at all. This mode provides additional
+ security as clients on channel may agree to use private
+ channel key that even servers do not know. Naturally,
+ this requires that every client on the channel knows
+ the key before hand (it is considered to be pre-shared-
+ key). The key material SHOULD be processed as stated
+ in the [SILC3] in the section Processing the Key Material.
+
+ As it is local setting it is possible to have several
+ private channel keys on one channel. In this case several
+ clients can talk on same channel but only those clients
+ that share the key with the message sender will be able
+ to hear the talking. Client SHOULD NOT display those
+ message for the end user that it is not able to decrypt
+ when this mode is set.
+
+ Only channel founder MAY set/unset this mode. If this
+ mode is unset the server will distribute new channel
+ key to all clients on the channel which will be used
+ thereafter.
+
+
+ 0x00000008 SILC_CMODE_INVITE
+
+ Channel is invite only channel. Client may join to this
+ channel only if it is invited to the channel. Channel
+ founder and channel operator MAY set/unset this mode.
+
+
+
+Riikonen [Page 27]
+\f
+Internet Draft 15 January 2007
+
+
+ 0x00000010 SILC_CMODE_TOPIC
+
+ The topic of the channel may only be set by client that
+ is channel founder or channel operator. Normal clients
+ on channel will not be able to set topic when this mode
+ is set. Channel founder and channel operator MAY set/
+ unset this mode.
+
+
+ 0x00000020 SILC_CMODE_ULIMIT
+
+ User limit has been set to the channel. New clients
+ may not join to the channel when the limit set is
+ reached. Channel founder and channel operator MAY set/
+ unset the limit. The <user limit> argument is the
+ number of limited users.
+
+
+ 0x00000040 SILC_CMODE_PASSPHRASE
+
+ Passphrase has been set to the channel. Client may
+ join to the channel only if it is able to provide the
+ correct passphrase. Setting passphrases to channel
+ is entirely safe as all commands are protected in the
+ SILC network. Only channel founder MAY set/unset
+ the passphrase. The <passphrase> argument is the
+ set passphrase.
+
+
+ 0x00000080 SILC_CMODE_CIPHER
+
+ Sets specific cipher to be used to protect channel
+ traffic. The <cipher> argument is the requested cipher.
+ When set or unset the server must re-generate new
+ channel key. Only channel founder MAY set the cipher of
+ the channel. When unset the new key is generated using
+ default cipher for the channel.
+
+
+ 0x00000100 SILC_CMODE_HMAC
+
+ Sets specific hmac to be used to compute the MACs of the
+ channel message. The <hmac> argument is the requested hmac.
+ Only channel founder may set the hmac of the channel.
+
+
+ 0x00000200 SILC_CMODE_FOUNDER_AUTH
+
+
+
+
+Riikonen [Page 28]
+\f
+Internet Draft 15 January 2007
+
+
+ Channel founder may set this mode to be able to regain
+ channel founder rights even if the client leaves the
+ channel. The <auth payload> is the Authentication Payload
+ consisting of the public key authentication method and the
+ digital signature for that method. The passphrase or NONE
+ authentication methods MUST NOT be accepted.
+
+ The server does not save <auth payload> but MUST verify it.
+ The public key used to verify the payload is the <founder
+ pubkey> if present, or the public key of the client sending
+ this command. If <founder pubkey> is present also that
+ public key MUST be saved as founder's public key. This
+ mode may be set only if the <auth payload> was verified
+ successfully. The hash function used with the <auth
+ payload> is selected by user or SHA1 otherwise.
+
+ The public key of the founder is sent in the
+ SILC_NOTIFY_TYPE_CMODE_CHANGE notify type so that other
+ routers and servers in the network may save the public key.
+ This way the founder can reclaim the founder rights back
+ to the channel from any server in the network. The founder
+ rights can be regained by the SILC_CUMODE_FOUNDER channel
+ user mode, or during joining procedure with the command
+ SILC_COMMAND_JOIN.
+
+ If this mode is already set but the <founder pubkey> is
+ different the new key will replace the old founder key and
+ the new key is distributed in the network with the
+ SILC_NOTIFY_TYPE_CMODE_CHANGE notify. Only the original
+ founder may set this mode multiple times and the client
+ MUST have SILC_CUMODE_FOUNDER mode on the channel.
+
+ When this channel mode is set the channel also becomes
+ permanent. If all clients leave the channel while this
+ mode is set the channel MUST NOT be destroyed. The founder
+ can reclaim the founder mode back on these empty channels
+ at any time. Implementations MAY limit the number of how
+ many channels a user can own and how long they remain
+ persistent.
+
+
+ 0x00000400 SILC_CMODE_SILENCE_USERS
+
+ Channel founder may set this mode to silence normal users
+ on the channel. Users with operator privileges are not
+ affected by this mode. Messages sent by normal users
+ are dropped by servers when this mode is set. This mode
+ can be used to moderate the channel. Only channel founder
+
+
+
+Riikonen [Page 29]
+\f
+Internet Draft 15 January 2007
+
+
+ may set/unset this mode.
+
+
+ 0x00000800 SILC_CMODE_SILENCE_OPERS
+
+ Channel founder may set this mode to silence operators
+ on the channel. When used with SILC_CMODE_SILENCE_USERS
+ mode this can be used to set the channel in state where only
+ the founder of the channel may send messages to the channel.
+ Messages sent by operators are dropped by servers when this
+ mode is set. Only channel founder may set/unset this mode.
+
+
+ 0x00001000 SILC_CMODE_CHANNEL_AUTH
+
+ When this mode is set the channel has one or more public keys
+ or certificates set, and ability to join the channel requires
+ a client to provide digital signature that can be successfully
+ verified with one of the channel public keys. This mode is
+ equivalent to the SILC_MODE_PASSPHRASE except that digital
+ signatures are used to gain access to the channel. Both
+ modes MAY be set at the same time. Channel founder may set
+ and unset this mode.
+
+ The <channel pubkey> argument is an Argument List Payload
+ where each argument is Public Key Payload including public
+ key to be added or removed from the channel public key list.
+ To add a public key to channel this mode is set and the
+ argument type is 0x00, and the argument is the public key.
+ To remove a public key from channel public key list the
+ argument type is 0x01, and the argument is the public key
+ to be removed from the list. To remove all public keys at
+ once this mode is unset. An implementation MAY limit the
+ number of public keys that can be set for the channel.
+ This mode MUST NOT be set if <channel pubkey> is not present
+ when the mode is set for the first time. Implementation MAY
+ add and remove multiple public keys at the same time by
+ including multiple arguments to the <channel pubkey>
+ Argument List Payload.
+
+
+ To make the mode system work, client MUST keep the channel mode
+ mask locally so that the mode setting and unsetting would work
+ without problems. The client receives the initial channel mode
+ mask when it joins to the channel. When the mode changes on
+ channel the server MUST distribute the changed channel mode mask
+ to all clients on the channel by sending the notify type
+ SILC_NOTIFY_TYPE_CMODE_CHANGE. The notify type MUST also be sent
+
+
+
+Riikonen [Page 30]
+\f
+Internet Draft 15 January 2007
+
+
+ to the server's primary router. If the <channel mode mask> was
+ not provided this command returns the mode mask, founder key,
+ channel public key list and the current user limit to the client.
+
+ Reply messages to the command:
+
+ Max Arguments: 6
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) <channel mode mask> (4) [<founder pubkey>]
+ (5) [<channel pubkeys>] (6) [<user limit>]
+
+ This command replies with the changed channel mode mask that
+ client MUST keep locally. It may also return the channel
+ founder's public key if it is set. It may also return list of
+ channel public keys when the list was altered. The <channel
+ pubkeys> is Argument List Payload and each argument includes
+ one public key. The <user limit> is the current user limit
+ on the channel, if one is set.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ON_CHANNEL
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_BAD_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_PRIV
+ SILC_STATUS_ERR_NO_CHANNEL_FOPRIV
+ SILC_STATUS_ERR_UNKNOWN_MODE
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_AUTH_FAILED
+
+
+ 18 SILC_COMMAND_CUMODE
+
+ Max Arguments: 4
+ Arguments: (1) <Channel ID> (2) <mode mask>
+ (3) <Client ID> (4) [<auth payload>]
+
+ This command is used by client to change channel user modes on
+ channel. Users on channel may have some special modes and this
+ command is used by channel operators to set or change these modes.
+ The <Channel ID> is the ID of the target channel. The <mode mask>
+ is OR'ed mask of modes. The <Client ID> is the target client.
+ The client changing channel user modes MUST be on the same channel
+
+
+
+Riikonen [Page 31]
+\f
+Internet Draft 15 January 2007
+
+
+ as the target client and posses sufficient privileges to be able to
+ change the mode.
+
+ When the mode is changed SILC_NOTIFY_TYPE_CUMODE_CHANGE notify
+ type is distributed to the channel.
+
+ The following channel modes are defined:
+
+ 0x00000000 SILC_CUMODE_NONE
+
+ No specific mode. This is the normal situation for client.
+ Also, this is the mode set when removing all modes from
+ the target client.
+
+
+ 0x00000001 SILC_CUMODE_FOUNDER
+
+ The client is channel founder of the channel. Usually this
+ mode is set only by the server when the channel was created.
+ However, if the SILC_CMODE_FOUNDER_AUTH channel mode has
+ been set, the client can claim channel founder privileges
+ by providing the <auth payload> that the server will use
+ to authenticate the client. The public key that server will
+ use to verify the <auth payload> MUST be the same public key
+ that was saved when the SILC_CMODE_FOUNDER_AUTH channel
+ mode was set. The client MAY remove this mode at any time.
+
+
+ 0x00000002 SILC_CUMODE_OPERATOR
+
+ Sets channel operator privileges on the channel for a
+ client on the channel. Channel founder and channel operator
+ MAY set/unset this mode. The client MAY remove this mode
+ at any time.
+
+
+ 0x00000004 SILC_CUMODE_BLOCK_MESSAGES
+
+ Marks that the client wishes not to receive any channel
+ messages sent for the channel. Client MAY set and unset
+ this mode to itself. Client MUST NOT set it to anyone else.
+ When this mode is set server MUST NOT deliver channel
+ messages to this client. Other packets such as channel
+ key packets are still sent to the client.
+
+ A separate service could provide additional filtering
+ features for accepting channel messages from certain
+ sender. However, this document does not specify such
+
+
+
+Riikonen [Page 32]
+\f
+Internet Draft 15 January 2007
+
+
+ service.
+
+
+ 0x00000008 SILC_CUMODE_BLOCK_MESSAGES_USERS
+
+ Marks that the client wishes not to receive any channel
+ messages sent from normal users. Only messages sent by
+ channel founder or channel operator is accepted. Client
+ MAY set and unset this mode to itself. Client MUST NOT
+ set it to anyone else. When this mode is set server MUST
+ NOT deliver channel messages that are sent by normal users
+ to this client.
+
+ A separate service could provide additional filtering
+ features for accepting channel messages from certain
+ sender. However, this document does not specify such
+ service.
+
+
+ 0x00000010 SILC_CUMODE_BLOCK_MESSAGES_ROBOTS
+
+ Marks that the client wishes not to receive any channel
+ messages sent from robots. Messages sent by users with
+ the SILC_UMODE_ROBOT user mode set are not delivered.
+ Client MAY set and unset this mode to itself. Client MUST
+ NOT set it to anyone else. When this mode is set server
+ MUST NOT deliver channel messages that are sent by robots
+ to this client.
+
+
+ 0x00000020 SILC_CUMODE_QUIET
+
+ Marks that the client cannot talk on the channel. This
+ mode can be set by channel operator or channel founder to
+ some other user that is not operator or founder. The
+ target client MUST NOT unset this mode. When this mode
+ is set the server MUST drop messages sent by this client
+ to the channel.
+
+
+ Reply messages to the command:
+
+ Max Arguments: 4
+ Arguments: (1) <Status Payload> (2) <channel user mode mask>
+ (3) <Channel ID> (4) <Client ID>
+
+ This command replies with the changed channel user mode mask that
+ client MUST keep locally. The <Channel ID> is the specified
+
+
+
+Riikonen [Page 33]
+\f
+Internet Draft 15 January 2007
+
+
+ channel. The <Client ID> is the target client.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ON_CHANNEL
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_BAD_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_PRIV
+ SILC_STATUS_ERR_NO_CHANNEL_FOPRIV
+ SILC_STATUS_ERR_UNKNOWN_MODE
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_AUTH_FAILED
+
+
+ 19 SILC_COMMAND_KICK
+
+ Max Arguments: 3
+ Arguments: (1) <Channel ID> (2) <Client ID>
+ (3) [<comment>]
+
+ This command is used by channel operators to remove a client from
+ channel. The <channel> argument is the channel the client to be
+ removed is on currently. Note that the "kicker" must be on the same
+ channel. If <comment> is provided it will be sent to the removed
+ client.
+
+ After kicking the client the server MUST send the notify type
+ SILC_NOTIFY_TYPE_KICKED to the channel and to its primary router.
+ The client is removed from the channel after sending this notify.
+ The kicked client MUST be removed from the invite list of the
+ channel if it is explicitly added in the list. The channel key
+ MUST also be re-generated after kicking, unless the
+ SILC_CMODE_PRIVKEY mode is set.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) <Client ID>
+
+ This command returns the Channel ID and Client ID that was kicked
+ from the channel.
+
+
+
+
+Riikonen [Page 34]
+\f
+Internet Draft 15 January 2007
+
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_NO_CHANNEL_PRIV
+ SILC_STATUS_ERR_NO_CLIENT_ID
+
+
+
+ 20 SILC_COMMAND_BAN
+
+ Max Arguments: 3
+ Arguments: (1) <Channel ID> (2) [<add | del>]
+ (3) [<ban list>]
+
+ This command is used to manage the ban list of the channel
+ indicated by the <Channel ID>. A client that is banned from
+ channel is no longer able to join the channel. The client which
+ is executing this command MUST have at least channel operator
+ privileges on the channel.
+
+ The <add | del> is an argument of size of 1 byte where 0x00 means
+ adding a client to ban list, and 0x01 means deleting a client
+ from ban list. The <ban list>, if present, indicates the
+ information to be added to or removed from the ban list. It
+ may include a string for matching clients, public key of a
+ client (Public Key Payload) or Client ID of a client. The
+ <ban list> is an Argument List Payload.
+
+ The following Argument Types has been defined for ban list
+ Argument Payloads:
+
+ 0x01 - Argument is an ban string of following format:
+
+ [<nickname>[@<server>]!][<username>]@[<hostname or IP/MASK>]
+
+ The <hostname> may also be in format of IP/MASK to indicate
+ a network.
+
+ 0x02 - Argument is the public key of a client
+ 0x03 - Argument is the Client ID of a client
+
+ If unknown type value is received or there is invalid amount of
+ Argument Payloads present in the list, the command MUST be
+
+
+
+Riikonen [Page 35]
+\f
+Internet Draft 15 January 2007
+
+
+ discarded. When argument that is to be deleted from the ban
+ list does not exist in the list the argument is ignored.
+
+ The server MUST send the notify type SILC_NOTIFY_TYPE_BAN to its
+ primary router after adding to or removing from the ban list.
+ The wildcards MAY be used with this command. If this command
+ is executed without the ban arguments the command merely replies
+ with the current ban list.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) [<ban list>]
+
+ This command replies with the <Channel ID> of the channel and
+ the current <ban list> of the channel if it exists.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_NOT_ON_CHANNEL
+ SILC_STATUS_ERR_NO_CHANNEL_PRIV
+ SILC_STATUS_ERR_RESOURCE_LIMIT
+
+
+
+
+ 21 SILC_COMMAND_DETACH
+
+ Max Arguments: 0
+ Arguments:
+
+ This command is used to detach from the network. Client can
+ send this command to its server to indicate that it will be
+ detached. By detaching the client remains in the network but
+ the actual network connection to the server is closed. The
+ client may then later resume the old session back.
+
+ When this command is received the server MUST check that the
+ client is locally connected client, and set the user mode
+ SILC_UMODE_DETACHED flag. The SILC_NOTIFY_TYPE_UMODE_CHANGE
+ MUST be also sent to routers. The server then sends command
+ reply to this command and closes the network connection.
+
+
+
+Riikonen [Page 36]
+\f
+Internet Draft 15 January 2007
+
+
+ The server MUST NOT remove the client from its lists, or send
+ any signoff notifications for this client. See the [SILC1]
+ for detailed information about detaching.
+
+ Reply messages to the command:
+
+ Max Arguments: 1
+ Arguments: (1) <Status Payload>
+
+ This command replies only with the status indication.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+
+
+
+ 22 SILC_COMMAND_WATCH
+
+ Max Arguments: 4
+ Arguments: (1) <Client ID> (2) [<add nickname>]
+ (3) [<del nickname>] (4) [<public key>]
+
+ This command is used to set up a watch for <add nickname>
+ nickname. When a user in the network appears with the
+ nickname, or signoffs the network or user's mode is changed
+ the client which set up the watch will be notified about
+ this change. This can be used to watch for certain nicknames
+ in the network and receive notifications when for example a
+ friend appears in the network or leaves the network.
+
+ The <del nickname> is a nickname that has been previously
+ added to watch list and is now removed from it. Notifications
+ for that nickname will not be delivered anymore. The nickname
+ set to watch MUST NOT include any wildcards. Note also that a
+ nickname may match several users since nicknames are not unique.
+ Implementations MAY set limits for how many nicknames client
+ can watch.
+
+ OPTIONALLY this command may also be set to watch clients' actions
+ in the network using their public key or certificate. The
+ <public key> MAY be present, and it is an Argument List Payload
+ where each argument is a Public Key Payload including public key
+ to be added or removed from the watch list. To To add a public
+ key to watch list the argument type is 0x00, and the argument is
+ the public key. To remove a public key from watch list list the
+ argument type is 0x01, and the argument is the public key to be
+
+
+
+Riikonen [Page 37]
+\f
+Internet Draft 15 January 2007
+
+
+ removed from the list. An implementation MAY limit the number of
+ public keys that can be set on the watch list. Implementation MAY
+ add and remove multiple public keys at the same time by including
+ multiple arguments to the <public key> Argument List Payload.
+
+ The <Client ID> is the Client ID of the sender of this command.
+
+ When normal server receives this command from client it
+ MUST send it to its router. Router will process the command
+ and actually keeps the watch list.
+
+ Reply messages to the command:
+
+ Max Arguments: 1
+ Arguments: (1) <Status Payload>
+
+ This command replies only with the status indication.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_BAD_NICKNAME
+ SILC_STATUS_ERR_WILDCARDS
+ SILC_STATUS_ERR_RESOURCE_LIMIT
+ SILC_STATUS_ERR_NO_SUCH_NICK
+ SILC_STATUS_ERR_NICKNAME_IN_USE
+
+
+ 23 SILC_COMMAND_SILCOPER
+
+ Max Arguments: 2
+ Arguments: (1) <username> (2) <authentication payload>
+
+ This command is used by normal client to obtain router operator
+ privileges (also known as SILC operator) on the router. Note
+ that router operator has privileges that supersedes the server
+ operator privileges.
+
+ The <username> is the username set in the server configurations
+ as operator. The <authentication payload> is the data that the
+ client is authenticated against. It may be passphrase prompted
+ for user on client's screen or it may be public key or certificate
+ authentication data (data signed with private key). The public
+ key that router will use to verify the signature found in the
+ payload should be verified. It is recommended that the public
+
+
+
+Riikonen [Page 38]
+\f
+Internet Draft 15 January 2007
+
+
+ key is saved locally in the router and router would not use
+ any public keys received during the SKE.
+
+ Difference between router operator and server operator is that
+ router operator is able to handle cell level properties while
+ server operator (even on router server) is able to handle only
+ local properties, such as, local connections and normal server
+ administration. The router operator is also able to use the
+ SILC_COMMAND_KILL command.
+
+ After changing the mode server MUST send the notify type
+ SILC_NOTIFY_TYPE_UMODE_CHANGE to its primary router.
+
+ Reply messages to the command:
+
+ Max Arguments: 1
+ Arguments: (1) <Status Payload>
+
+ This command replies only with Status Payload.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_AUTH_FAILED
+
+
+
+
+ 24 SILC_COMMAND_LEAVE
+
+ Max Arguments: 1
+ Arguments: (1) <Channel ID>
+
+ This command is used by client to leave a channel the client is
+ joined to.
+
+ When leaving channel the server MUST send the notify type
+ SILC_NOTIFY_TYPE_LEAVE to its primary router and to the channel.
+ The channel key MUST also be re-generated when leaving the channel
+ and distribute it to all clients still currently on the channel.
+ The key MUST NOT be re-generated if the SILC_CMODE_PRIVKEY mode
+ is set.
+
+ Reply messages to the command:
+
+
+
+
+Riikonen [Page 39]
+\f
+Internet Draft 15 January 2007
+
+
+ Max Arguments: 2
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+
+ The <Channel ID> is the ID of left channel.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_BAD_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+
+
+ 25 SILC_COMMAND_USERS
+
+ Max Arguments: 2
+ Arguments: (1) [<Channel ID>] (2) [<channel name>]
+
+ This command is used to list user names currently on the requested
+ channel; either the argument <Channel ID> or the <channel name>.
+ One of these arguments must be present. The server MUST resolve
+ the joined clients and reply with a lists of users on the channel
+ and with list of user modes on the channel.
+
+ If the requested channel is a private or secret channel, this
+ command MUST NOT send the list of users, except if the sender is
+ on the channel, or the sender is a server. Otherwise, error is
+ returned to the sender.
+
+ Reply messages to the command:
+
+ Max Arguments: 5
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) <list count> (4) <Client ID list>
+ (5) <client mode list>
+
+ This command replies with the Channel ID of the requested channel
+ Client ID list of the users on the channel and list of their modes.
+ The Client ID list has Client ID's of all users in the list. The
+ <Client ID list> is formed by adding Client ID's one after another.
+ The <client mode list> is formed by adding client's user modes on
+ the channel one after another (4 bytes (32 bits) each). The <list
+ count> of length of 4 bytes (32 bits), tells the number of entries
+ in the lists. Both lists MUST have equal number of entries.
+
+
+
+
+Riikonen [Page 40]
+\f
+Internet Draft 15 January 2007
+
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+ SILC_STATUS_ERR_BAD_CHANNEL_ID
+ SILC_STATUS_ERR_NO_CHANNEL_ID
+ SILC_STATUS_ERR_NOT_ON_CHANNEL
+
+
+ 26 SILC_COMMAND_GETKEY
+
+ Max Arguments: 1
+ Arguments: (1) <ID Payload>
+
+ This command is used to fetch the public key of the client or
+ server indicated by the <ID Payload>. The public key is fetched
+ from the server where to the client is connected.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <ID Payload>
+ (3) [<Public Key Payload>]
+
+ This command replies with the client's or server's ID and with
+ the <Public Key Payload>.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+ SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+
+
+ 27 SILC_COMMAND_SERVICE
+
+ Max Arguments: 256
+ Arguments: (1) [<service name>] (2) [<auth payload>]
+ (n) [...]
+
+ This command is used to negotiate a service agreement with a
+ remote server. If this command is given without arguments it
+
+
+
+Riikonen [Page 41]
+\f
+Internet Draft 15 January 2007
+
+
+ MAY return the service list, if it is publicly available. The
+ <service name> is a service specific identifier, and the
+ <auth payload> MAY be used to authenticate the requester to the
+ remote service. The authentication to a service may be based
+ on previous agreement with the requester and the service
+ provider. The command MAY also take additional service
+ specific arguments.
+
+ This document does not specify any services. How the services
+ are configured and put available in a server is also out of
+ scope of this document.
+
+ This command MAY be used by client to start using some service
+ in a server, but it also MAY be used by server to negotiate
+ to start using a service in some other server or router.
+
+ After the negotiation is done both of the parties need to know
+ from the service identifier how the service can be used. The
+ service can be considered to be a protocol which both of the
+ parties need to support.
+
+ Reply messages to the command:
+
+ Max Arguments: 256
+ Arguments: (1) <Status Payload> (2) [<service list>]
+ (3) [<service name>] (n) [...]
+
+
+ This command MAY reply with the <service list> when command is
+ given without arguments, and the list is a comma separated list
+ of service identifiers. The <service name> is the service that
+ the sender requested and this is provided when the server has
+ accepted the sender to use the <service name>. The command
+ reply MAY also have additional service specific arguments.
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SUCH_SERVICE
+ SILC_STATUS_ERR_AUTH_FAILED
+ SILC_STATUS_ERR_PERM_DENIED
+
+
+
+ 28 - 199
+
+
+
+Riikonen [Page 42]
+\f
+Internet Draft 15 January 2007
+
+
+ Currently undefined commands.
+
+
+ 200 - 254
+
+ These commands are reserved for private use and will not be defined
+ in this document.
+
+
+ 255 SILC_COMMAND_MAX
+
+ Reserved command. This must not be sent.
+
+
+2.4 SILC Command Status Payload
+
+ Command Status Payload is sent in command reply messages to indicate
+ the status of the command. The payload is one of argument in the
+ command thus this is the data area in Command Argument Payload described
+ in [SILC2]. The payload is only 2 bytes in length. The following
+ diagram represents the Command Status Payload (fields are always in
+ MSB first order).
+
+
+ 1
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Status | Error |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 6: SILC Command Status Payload
+
+
+ o Status (1 byte) - Indicates the status message type,
+ error, start of list, entry of list or end of list.
+
+ o Error (1 byte) - Indicates the error if the Status
+ field is some list status, which means there are list
+ of errors.
+
+ The values in Status and Error fields are set according
+ the following rules:
+
+ o If there is single reply and error has not occurred
+ then Status field includes value SILC_STATUS_OK, and
+ the Error field MUST be ignored (and set to zero
+ value).
+
+
+
+
+Riikonen [Page 43]
+\f
+Internet Draft 15 January 2007
+
+
+ o If there is single error, then Status field includes
+ one of the error values, and the Error field MUST be
+ ignored (and set to zero value).
+
+ o If there will be multiple successful command replies
+ then Status field includes SILC_STATUS_LIST_START,
+ SILC_STATUS_LIST_ITEM or SILC_STATUS_LIST_END value,
+ and Error field is set to SILC_STATUS_OK.
+
+ o If there are multiple error replies then Status field
+ includes SILC_STATUS_LIST_START, SILC_STATUS_LIST_ITEM
+ or SILC_STATUS_LIST_END value, and the Error field
+ includes the error value.
+
+ This way it is possible to send single successful or
+ single error reply, but also multiple successful and
+ multiple error replies. Note that it is possible to
+ send both list of successful replies and list of error
+ replies at the same time, however in this case the
+ list of error replies MUST be sent after the successful
+ replies. This way the recipient may ignore the multiple
+ errors if it wishes to do so. Also note that in this
+ case the successful and error replies belong to the
+ same list.
+
+ All Status messages are described in the next section.
+
+
+3 SILC Status Types
+
+ Status messages are returned in SILC protocol in command reply
+ packet and in notify packet. The SILC_PACKET_COMMAND_REPLY is
+ the command reply packet and status types are sent inside the
+ Status Payload as one of command reply argument, as defined in
+ previous sections. For SILC_PACKET_NOTIFY packet they can be sent
+ as defined in [SILC2] for SILC_NOTIFY_TYPE_ERROR type. The same
+ types defined in this section are used in both cases.
+
+ When returning status messages in the command reply message they
+ indicate whether the command was executed without errors. If error
+ occurred the status indicates which error occurred. If error
+ occurred the arguments to the command replies are dictated by the
+ error type. If arguments are to be sent, they are defined below
+ with the error status types.
+
+ When sending status messages in SILC_NOTIFY_TYPE_ERROR notify type
+ they always send some error status. Usually they are sent to
+ indicate that error occurred while processing some SILC packet.
+
+
+
+Riikonen [Page 44]
+\f
+Internet Draft 15 January 2007
+
+
+ Please see the [SILC1] and [SILC2] for more information sending
+ status types in SILC_NOTIFY_TYPE_ERROR notify.
+
+ The Status Types are only numeric values and the receiver must
+ convert the numeric values into human readable messages if this
+ is desired in the application.
+
+ List of all defined status types:
+
+ Generic status messages:
+
+ 0 SILC_STATUS_OK
+
+ Ok status. Everything went Ok. The status payload maybe
+ safely ignored in this case.
+
+ 1 SILC_STATUS_LIST_START
+
+ Start of the list. There will be several command replies and
+ this reply is the start of the list.
+
+ 2 SILC_STATUS_LIST_ITEM
+
+ Item in the list. This is one of the item in the list but not the
+ first or last one.
+
+ 3 SILC_STATUS_LIST_END
+
+ End of the list. There were several command replies and this
+ reply is the last of the list. There won't be other replies
+ belonging to this list after this one.
+
+ 4 - 9
+
+ Currently undefined and has been reserved for the future.
+
+
+ Error status message:
+
+
+
+ 10 SILC_STATUS_ERR_NO_SUCH_NICK
+
+ "No such nickname". Requested nickname does not exist.
+ The next argument MUST be the requested nickname.
+
+ 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL
+
+
+
+
+Riikonen [Page 45]
+\f
+Internet Draft 15 January 2007
+
+
+ "No such channel". Requested channel name does not exist.
+ The next argument MUST be the requested channel name.
+
+ 12 SILC_STATUS_ERR_NO_SUCH_SERVER
+
+ "No such server". Requested server name does not exist.
+ The next argument MUST be the requested server name.
+
+ 13 SILC_STATUS_ERR_INCOMPLETE_INFORMATION
+
+ "Incomplete registration information". Information remote
+ sent was incomplete.
+
+ 14 SILC_STATUS_ERR_NO_RECIPIENT
+
+ "No recipient given". Command required recipient which was
+ not provided.
+
+ 15 SILC_STATUS_ERR_UNKNOWN_COMMAND
+
+ "Unknown command". Command sent to server is unknown by the
+ server.
+
+ 16 SILC_STATUS_ERR_WILDCARDS
+
+ "Wildcards cannot be used". Wildcards were provided but they
+ weren't permitted.
+
+ 17 SILC_STATUS_ERR_NO_CLIENT_ID
+
+ "No Client ID given". Client ID were expected as command
+ parameter but were not found.
+
+ 18 SILC_STATUS_ERR_NO_CHANNEL_ID
+
+ "No Channel ID given". Channel ID were expected as command
+ parameter but were not found.
+
+ 19 SILC_STATUS_ERR_NO_SERVER_ID
+
+ "No Serve ID given". Server ID were expected as command
+ parameter but were not found.
+
+ 20 SILC_STATUS_ERR_BAD_CLIENT_ID
+
+ "Bad Client ID". Client ID provided were erroneous.
+ The next argument MUST be the provided ID.
+
+
+
+
+Riikonen [Page 46]
+\f
+Internet Draft 15 January 2007
+
+
+ 21 SILC_STATUS_ERR_BAD_CHANNEL_ID
+
+ "Bad Channel ID". Channel ID provided were erroneous.
+ The next argument MUST be the provided ID.
+
+ 22 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+
+ "No such Client ID". Client ID provided does not exist.
+ The unknown Client ID MUST be provided as next argument
+ in the reply.
+
+ 23 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+
+ "No such Channel ID". Channel ID provided does not exist.
+ The unknown Channel ID MUST be provided as next argument
+ in the reply.
+
+ 24 SILC_STATUS_ERR_NICKNAME_IN_USE
+
+ "Nickname already exists". Nickname created could not be
+ registered because number of same nicknames were already set to
+ maximum. This is not expected to happen in real life but is
+ possible to occur.
+
+ 25 SILC_STATUS_ERR_NOT_ON_CHANNEL
+
+ "You are not on that channel". The command were specified for
+ channel user is not currently on. The next argument MUST be the
+ Channel ID.
+
+ 26 SILC_STATUS_ERR_USER_NOT_ON_CHANNEL
+
+ "They are not on channel". The requested target client is not
+ on requested channel. The next two arguments, in this order,
+ MUST be the requested Client ID and Channel ID.
+
+ 27 SILC_STATUS_ERR_USER_ON_CHANNEL
+
+ "User already on channel". User were invited on channel they
+ already are on. The next two arguments, in this order, MUST be
+ the requested Client ID and Channel ID.
+
+ 28 SILC_STATUS_ERR_NOT_REGISTERED
+
+ "You have not registered". User executed command that requires
+ the client to be registered on the server before it may be
+ executed.
+
+
+
+
+Riikonen [Page 47]
+\f
+Internet Draft 15 January 2007
+
+
+ 29 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+
+ "Not enough parameters". Command requires more parameters
+ than provided.
+
+ 30 SILC_STATUS_ERR_TOO_MANY_PARAMS
+
+ "Too many parameters". Too many parameters were provided
+ for the command.
+
+ 31 SILC_STATUS_ERR_PERM_DENIED
+
+ "Permission denied". Generic permission denied error status
+ to indicate disallowed access.
+
+ 32 SILC_STATUS_ERR_BANNED_FROM_SERVER
+
+ "You are banned from this server". The client tried to register
+ on server that has explicitly denied this host to connect.
+
+ 33 SILC_STATUS_ERR_BAD_PASSWORD
+
+ "Cannot join channel. Incorrect password". Password provided for
+ channel were not accepted. The next argument MUST be the
+ Channel ID.
+
+ 34 SILC_STATUS_ERR_CHANNEL_IS_FULL
+
+ "Cannot join channel. Channel is full". The channel is full
+ and client cannot be joined to it. The next argument MUST be
+ the Channel ID.
+
+ 35 SILC_STATUS_ERR_NOT_INVITED
+
+ "Cannot join channel. You have not been invited". The channel
+ is invite only channel and client has not been invited. The next
+ argument MUST be the Channel ID.
+
+ 36 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
+
+ "Cannot join channel. You have been banned". The client has
+ been banned from the channel. The next argument MUST be the
+ Channel ID.
+
+ 37 SILC_STATUS_ERR_UNKNOWN_MODE
+
+ "Unknown mode". Mode provided by the client were unknown to
+ the server.
+
+
+
+Riikonen [Page 48]
+\f
+Internet Draft 15 January 2007
+
+
+ 38 SILC_STATUS_ERR_NOT_YOU
+
+ "Cannot change mode for other users". User tried to change
+ someone else's mode.
+
+ 39 SILC_STATUS_ERR_NO_CHANNEL_PRIV
+
+ "Permission denied. You are not channel operator". Command may
+ be executed only by channel operator. The next argument MUST be
+ the Channel ID.
+
+ 40 SILC_STATUS_ERR_NO_CHANNEL_FOPRIV
+
+ "Permission denied. You are not channel founder". Command may
+ be executed only by channel operator. The next argument MUST be
+ the Channel ID.
+
+ 41 SILC_STATUS_ERR_NO_SERVER_PRIV
+
+ "Permission denied. You are not server operator". Command may
+ be executed only by server operator.
+
+ 42 SILC_STATUS_ERR_NO_ROUTER_PRIV
+
+ "Permission denied. You are not SILC operator". Command may be
+ executed only by router (SILC) operator.
+
+ 43 SILC_STATUS_ERR_BAD_NICKNAME
+
+ "Bad nickname". Nickname requested contained illegal characters
+ or were malformed.
+
+ 44 SILC_STATUS_ERR_BAD_CHANNEL
+
+ "Bad channel name". Channel requested contained illegal characters
+ or were malformed.
+
+ 45 SILC_STATUS_ERR_AUTH_FAILED
+
+ "Authentication failed". The authentication data sent as
+ argument were wrong and thus authentication failed.
+
+ 46 SILC_STATUS_ERR_UNKOWN_ALGORITHM
+
+ "The algorithm was not supported." The server does not support the
+ requested algorithm. The next argument MUST be the algorithm name
+ string.
+
+
+
+
+Riikonen [Page 49]
+\f
+Internet Draft 15 January 2007
+
+
+ 47 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+
+ "No such Server ID". Server ID provided does not exist.
+ The unknown Server ID MUST be provided as next argument
+ in the reply.
+
+ 48 SILC_STATUS_ERR_RESOURCE_LIMIT
+
+ "No more resources available". This can mean that server cannot
+ or will not accept something due to resource limitations.
+
+ 49 SILC_STATUS_ERR_NO_SUCH_SERVICE
+
+ "Service does not exist". Requested service identifier is
+ unknown. The next argument MUST be the service identifier.
+
+ 50 SILC_STATUS_ERR_NOT_AUTHENTICATED
+
+ "You have not been authenticated". Remote connection is not
+ authenticated even though it is supposed to be.
+
+ 51 SILC_STATUS_ERR_BAD_SERVER_ID
+
+ "Server ID is not valid". Provided server ID is not valid.
+ The next argument MUST be the provided ID.
+
+ 52 SILC_STATUS_ERR_KEY_EXCHANGE_FAILED
+
+ "Key exchange failed". Key Exchange protocol failed.
+
+ 53 SILC_STATUS_ERR_BAD_VERSION
+
+ "Bad version". Protocol or software version mismatch.
+
+ 54 SILC_STATUS_ERR_TIMEDOUT
+
+ "Operation timed out". Operation or service request timed
+ out, and thus was not processed.
+
+ 55 SILC_STATUS_ERR_UNSUPPORTED_PUBLIC_KEY
+
+ "Unsupported public key type". The public key or certificate
+ type is not supported in this implementation.
+
+ 56 SILC_STATUS_ERR_OPERATION_ALLOWED
+
+ "Operation is not allowed". A operation, for example a command,
+ is not allowed or it's execution is not allowed.
+
+
+
+Riikonen [Page 50]
+\f
+Internet Draft 15 January 2007
+
+
+4 Security Considerations
+
+ Security is central to the design of this protocol, and these security
+ considerations permeate the specification. Common security considerations
+ such as keeping private keys truly private and using adequate lengths for
+ symmetric and asymmetric keys must be followed in order to maintain the
+ security of this protocol.
+
+
+5 References
+
+ [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, January 2007.
+
+ [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
+ January 2007.
+
+ [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
+ Protocols", Internet Draft, January 2007.
+
+ [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
+ RFC 1459, May 1993.
+
+ [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
+ April 2000.
+
+ [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
+ 2811, April 2000.
+
+ [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
+ 2812, April 2000.
+
+ [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
+ 2813, April 2000.
+
+ [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
+ Internet Draft.
+
+ [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
+ November 1998.
+
+ [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
+ September 1999.
+
+ [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
+ Infrastructure, Certificate and CRL Profile", RFC 2459,
+ January 1999.
+
+
+
+
+Riikonen [Page 51]
+\f
+Internet Draft 15 January 2007
+
+
+ [Schneier] Schneier, B., "Applied Cryptography Second Edition",
+ John Wiley & Sons, New York, NY, 1996.
+
+ [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
+ CRC Press 1997.
+
+ [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
+ RFC 2412, November 1998.
+
+ [ISAKMP] Maughan D., et al, "Internet Security Association and
+ Key Management Protocol (ISAKMP)", RFC 2408, November
+ 1998.
+
+ [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
+ (IKE)", RFC 2409, November 1998.
+
+ [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
+ Authentication", RFC 2104, February 1997.
+
+ [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
+ Specifications, Version 2.0", RFC 2437, October 1998.
+
+ [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 3629, November 2003.
+
+ [ATTRS] Riikonen, P., "User Online Presence and Information
+ Attributes", Internet Draft, May 2002.
+
+
+6 Author's Address
+
+ Pekka Riikonen
+ Helsinki
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+Appendix A
+
+ This appendix defines the usage of the <Requested Attributes> argument in
+ the SILC_COMMAND_WHOIS command. The attributes are defined in [ATTRS],
+ and may be used to request additional information about the user. Since
+ the information that may be requested using the attributes is something
+ that server cannot deliver to the sender, it is possible to send the WHOIS
+
+
+
+Riikonen [Page 52]
+\f
+Internet Draft 15 January 2007
+
+
+ command directly to the destination client whom will then provide the
+ requested attributes. This requires the servers to relay the WHOIS
+ command to the client, and it requires capability for handling the WHOIS
+ command in the client end.
+
+ The <Requested Attributes> MAY include several attributes that are
+ requested. The format and encoding of the <Requested Attributes> is as
+ defined in [ATTRS]. When <Requested Attributes> argument is set the
+ server MAY process the attributes to see whether it can narrow down
+ the WHOIS search, for example when searching with a nickname. The
+ normal servers MUST process the WHOIS command as normal WHOIS command,
+ that is to send the command directly to the router. The router MAY
+ process the attributes, but it MUST send the command to the server
+ that owns the requested client.
+
+ The server that owns the client and receives the command MUST check
+ whether the client is detached from the network. If it is detached,
+ that is the user mode has the SILC_UMODE_DETACHED mode set, it SHOULD
+ process the attributes and provide as many of the requested attributes
+ as possible and then send reply back to the sender. If the client is
+ active in the network it MUST send the command to the client for
+ processing.
+
+ The client receiving WHOIS command SHOULD check whether the
+ <Requested Attributes> argument is set. If it is not set then the
+ WHOIS command SHOULD be discarded. The client processes the requested
+ attributes and SHOULD reply to each of the requested attribute with
+ either valid value, or with an indication that the requested attribute
+ is not known or supported. This is to be done as defined in [ATTRS].
+ The client always MUST send a reply to the command when some attributes
+ were requested. The client MAY also add additional attributes to the
+ reply even if they were not requested. The client MAY also digitally
+ sign the attributes with ATTRIBUTE_USER_DIGITAL_SIGNATURE as defined
+ in [ATTRS]. Then the client sends the reply back to the sender of
+ the command. The command reply that client assembles does not need
+ to include any other argument but the <Status Payload> (1), and the
+ <Attributes> (11). The server receiving reply from client MUST allow
+ this sort of command reply for WHOIS command.
+
+ The information received from the client MAY be cached in the
+ server's end. The caching may be desired for example if the client
+ can be detached from the network. This way the server is then able
+ to provide at least partial information for a requester. The
+ server MAY also process the command reply and verify whether the
+ attributes provided in the reply are actually valid. If it can do
+ this, and verify that they indeed are valid values it MAY append
+ a digital signature at the end of the attributes with the
+ ATTRIBUTE_SERVER_DIGITAL_SIGNATURE as defined in [ATTRS]. The
+
+
+
+Riikonen [Page 53]
+\f
+Internet Draft 15 January 2007
+
+
+ server then MUST provide valid WHOIS command reply to the sender
+ of the command. Other servers and routers that receive the command
+ reply en route to the original sender MAY also cache the information.
+
+ The client which receives the command reply to the WHOIS command
+ SHOULD verify the ATTRIBUTE_USER_DIGITAL_SIGNATURE and the
+ ATTRIBUTE_SERVER_DIGITAL_SIGNATURE if they are provided.
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 54]
+\f
--- /dev/null
+
+
+
+
+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-flags-payloads-04.txt 2 December 2003
+Expires: 2 June 2004
+
+
+ SILC Message Flag Payloads
+ <draft-riikonen-flags-payloads-04.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+Abstract
+
+ This memo describes the data payloads associated with the SILC Message
+ Flags, as defined in the SILC Packet Protocol specification [SILC2]. The
+ purpose of the Message Flags is to augment the function of the Message
+ Payload used to send both private and channel messages, by allowing the
+ sender to tell the receiver what type of data the payload includes, and
+ how the data should be processed. Some of the Message Flags may define
+ additional payloads to be associated with the flag, and this memo
+ describes these payloads.
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 1]
+\f
+Internet Draft 2 December 2003
+
+
+Table of Contents
+
+ 1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 2
+ 2 SILC Message Flags ............................................ 3
+ 3 SILC Message Flag Payloads .................................... 3
+ 3.1 SILC_MESSAGE_FLAG_REQUEST ................................. 3
+ 3.2 SILC_MESSAGE_FLAG_REPLY ................................... 4
+ 3.3 SILC_MESSAGE_FLAG_SIGNED .................................. 4
+ 3.4 SILC_MESSAGE_FLAG_DATA .................................... 7
+ 3.5 SILC_MESSAGE_FLAG_ACK ..................................... 8
+ 4 Security Considerations ....................................... 9
+ 5 References .................................................... 9
+ 6 Author's Address .............................................. 10
+ 7 Full Copyright Statement ...................................... 10
+
+
+1. Introduction
+
+ The Secure Internet Live Conferencing [SILC1] supports sending binary
+ messages between users in the network. To make the data sending, and
+ processing at the receiver's end as simple as possible the SILC defines
+ Message Flags to the Message Payload [SILC2] that is used to send private
+ and channel messages, which can help the receiver to decide how the data
+ is encoded, and how it should be interpreted. Some of the Message Flags
+ may define additional payloads to be associated with the flag, but the
+ [SILC2] does not define them. This memo defines the payloads for those
+ Message Flags that was marked to include additional payloads in [SILC2].
+
+ By defining the payloads for the Message Flags the Message Payload
+ can be augmented to support any kind of data, which can be easily
+ interpreted at the receiver end. For example, it would be possible to
+ send audio stream, video stream, image files and HTML pages as messages,
+ and the receiver can either choose to ignore the message or to process
+ it, or to perhaps pass the message to some application for processing.
+ Without specific payloads for Message Flags it is almost impossible for
+ the receiver to interpret binary data from the payload.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+ interpreted as described in [RFC2119].
+
+
+
+
+
+
+
+Riikonen [Page 2]
+\f
+Internet Draft 2 December 2003
+
+
+2 SILC Message Flags
+
+ The Message Flags was added to the SILC protocol for the reason that SILC
+ provides sending binary data as messages between users, and entities in
+ the network, and interpreting pure binary data is almost impossible.
+ With the Message Flags the purpose, the reason, and the method for how
+ the message must be interpreted can be told to the recipient. Other
+ conferencing protocols which are usually ASCII based protocols do not have
+ such problems since they do not generally support sending of binary data
+ at all, or require specific encoding of the data before it can be sent
+ over the network.
+
+ The Message Payload in SILC can have flags that can augment the function
+ of the payload. The flags can tell for example that the message is a
+ request, or a reply to an earlier received request. They can tell that
+ the message is some action that the sender is performing, or they can tell
+ that the message is an auto reply, or that it is explicitly digitally
+ signed by the sender.
+
+ The problem of Message Flags is that the space for flags mask is only 16
+ bits, so there is a limited number of flags available. For this reason
+ having a flag that defines a generic way of sending any kind of data as
+ a message, and can be easily interpreted at the receiver's end is important.
+ For this reason the flag SILC_MESSAGE_FLAG_DATA was added to the protocol
+ which can represent any data. This memo describe how this flag is used
+ and how the associated payload is constructed and processed. This memo
+ also describes payloads for all the other flags that can have associated
+ payloads.
+
+
+3 SILC Message Flag Payloads
+
+ The [SILC2] defines the flags which may have associated payloads. This
+ section will list these flags and define the payloads.
+
+
+3.1 SILC_MESSAGE_FLAG_REQUEST
+
+ Currently this flag can be used in the context of application specific,
+ service specific or vendor specific requests, and the data payload type is
+ dependent of this context. Therefore, payload is not defined for this
+ flag in this memo. This flag may also be masked with some other flag in
+ the message payload, including with some other flag that defines
+ additional payload.
+
+
+
+
+
+
+
+Riikonen [Page 3]
+\f
+Internet Draft 2 December 2003
+
+
+3.2 SILC_MESSAGE_FLAG_REPLY
+
+ Currently this flag can be used in the context of application specific,
+ service specific or vendor specific replies, and the data payload type is
+ dependent of this context. Therefore, payload is not defined for this
+ flag in this memo. This flag may also be masked with some other flag in
+ the message payload, including with some other flag that defines
+ additional payload.
+
+
+3.3 SILC_MESSAGE_FLAG_SIGNED
+
+ This flag is used to tell the recipient that the sent message is
+ digitally signed by the sender, and that the recipient should verify
+ the signature to verify the true authenticity of the received message.
+ All message payloads in SILC provides message authentication code (MAC)
+ which can be used to verify that the sender produced and sent the message.
+ Even so, signing messages digitally can be used to verify the authenticity
+ of the message when recipient trusts the sender and to provide
+ non-repudiation.
+
+ This flag defines a payload which is used to deliver the actual message,
+ sender's public key and the digital signature. The payload for
+ SILC_MESSAGE_FLAG_SIGNED is as follows:
+
+ (*) indicates that the field is not encrypted.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 4]
+\f
+Internet Draft 2 December 2003
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Start of Message Payload ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Public Key Payload * ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Signature Data Length * | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Signature Data * ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Initial Vector * ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ MAC * ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 1: SILC_MESSAGE_FLAG_SIGNED Payload
+
+
+ o Start of Message Payload (variable length) - This is the
+ start of the Message Payload without the IV and MAC fields,
+ since those fields are appended at the end of this payload.
+
+ o Public Key Payload (variable length) - This includes the
+ Public Key Payload [SILC2] which can be used to deliver the
+ sender's public key (or certificate). It also indicates the
+ type of the public key (or certificate) which the recipient
+ use to identify how the signature must be verified. This
+ payload must always be present but it is not required to
+ include the public key data. The Public Key Type field in
+ the Public Key Payload MUST be set to the correct type of
+ the key, even if the actual public key data is not included.
+ This field is not encrypted but is authenticated.
+
+ o Signature Data Length (2 bytes) - Indicates the length of
+ the Signature Data field not including any other field.
+ This field is not encrypted but is authenticated.
+
+
+
+
+Riikonen [Page 5]
+\f
+Internet Draft 2 December 2003
+
+
+ o Signature Data (variable length) - Includes the actual
+ signature data. The signature computation and encoding
+ is key type specific. See [SILC3] for all key types, and
+ their respective references for how to compute and encode
+ the signature. This field is not encrypted but is
+ authenticated.
+
+ o Initial Vector (variable length) - the IV of the Message
+ Payload as defined in [SILC2]. This field is not encrypted
+ but is authenticated.
+
+ o MAC (variable length) - the MAC of the Message Payload as
+ defined in [SILC2]. The MAC is computed after encryption
+ and after signature computation. All data in the Message
+ Payload and this payload, including the IV field are
+ included in the MAC computation. This field is not
+ encrypted.
+
+ How the data is processed before it is signed is key type specific.
+ The actual data that to be signed MUST be the plaintext message
+ payload before encryption. The data to be signed is concatenation
+ of the Start of Message Payload field and the Public Key Payload,
+ in that order. Any other fields are not included for signature data.
+ Before signing, the data is always processed, usually hashed. The
+ hash function to be used is defined in the key type specific
+ definitions. See the key type specific references in [SILC3].
+
+ If the public key of the sender is included in the payload the
+ recipient SHOULD verify it before accepting the public key. Recipient
+ SHOULD verify the signature before accepting and caching the public key.
+ With certificates the certificate verification may be done before
+ verifying the signature. If the signature verification fails the
+ message should still be displayed. The end user should also be
+ notified about the result of the signature verification.
+
+ To make the packet size smaller implementations may not want to
+ include the actual public key in all signed messages. Sending the
+ public key in the first message is usually sufficient. Subsequent
+ messages may include empty Public Key Payload with an indication of
+ the public key type.
+
+ Implementations that do not support this flag can still process the
+ message payload in normal manner. These implementations merely parse
+ the decrypted payload in normal manner and ignore the extra data in
+ the payload. They can do this by extracting the MAC and the IV from
+ the end of the data buffer and thus ignoring the data between start of
+ the Message Payload and the Initial Vector field.
+
+
+
+
+Riikonen [Page 6]
+\f
+Internet Draft 2 December 2003
+
+
+ This flag MAY be masked with any other Message Flag including those that
+ define additional payloads. As long as the defined payload resides in
+ the data area of the message payload this flag may be masked with the
+ other flags.
+
+
+3.4 SILC_MESSAGE_FLAG_DATA
+
+ This flag is used to represent any data as a message in the way that it
+ can be easily interpreted by the recipient. This flag is used to send
+ MIME objects as messages from the sender to the receiver. The MIME as
+ defined in [RFC2045], [RFC2046], [RFC2047], [RFC2048] and [RFC2049] is
+ well established protocol for sending different kind of data with many
+ applications and protocols. It support dozens of different media types
+ and encodings, and for this reason is ideal for sending data in SILC
+ message payloads as well.
+
+ When the receiver has checked that the message payload includes the
+ SILC_MESSAGE_FLAG_DATA flag, it may then start parsing the MIME header.
+ It would also be possible to pass the message to some application which
+ can already interpret MIME objects. If the receiver does not support the
+ media type received in the MIME header, it SHOULD be treated as
+ "application/octet-stream". The receiver MAY also ignore and discard
+ messages that it does not support.
+
+ The MIME header MUST be at the start of the data area of the Message
+ Payload. The MIME header received in the data area of the payload SHOULD
+ have the MIME-Version field at first and then Content-Type field. The
+ MIME-Version field is not required to be present in each body part of
+ multipart entity. Additionally the header MAY also include any other
+ MIME compliant headers. The character encoding for the MIME Header
+ strings inside the message payload is US-ASCII, as defined in [RFC2045].
+ The actual MIME object may define additional character sets or encodings
+ for the data it delivers.
+
+ Hence, the MIME Header in the message payload may be as follows:
+
+ MIME-Version: 1.0\r\n
+ Content-Type: discrete/composite\r\n
+ Content-Transfer-Encoding: binary\r\n
+ \r\n
+
+ The Content-Transfer-Encoding field behaves as defined in [RFC2045] and
+ defines the encoding of the data in the MIME object. The preferred data
+ encoding with SILC is "binary". However, many MIME media types defines
+ their preferred encoding and they may be used if binary encoding is not
+ suitable.
+
+
+
+
+Riikonen [Page 7]
+\f
+Internet Draft 2 December 2003
+
+
+ When sending large amounts of traffic or large files as MIME objects the
+ limits of the SILC Packet needs to be taken into consideration. The
+ maximum length of SILC Packet is 2^16 bytes, and larger messages would
+ need to be fragmented. MIME provides way of fragmenting and reassembling
+ messages, and it is to be done with SILC as defined in [RFC2046]. The
+ MIME fragmentation is defined for gateway usage, but in case of SILC the
+ sender (for example, a client) may also start sending fragmented MIME
+ objects.
+
+ This flag SHOULD NOT be masked with some other Message Flag that defines
+ payloads for message data. Generally this sort of setting would be
+ impossible for the receiver to interpret. However, flags that does not
+ define any specific payloads MAY be masked with this flag as well. For
+ example, this flag could be masked also with SILC_MESSAGE_FLAG_REQUEST flag.
+ It also can be masked with SILC_MESSAGE_FLAG_SIGNED flag since it does not
+ define data specific payload.
+
+
+3.5 SILC_MESSAGE_FLAG_ACK
+
+ This flag is used to send acknowledgement messages. When sender of a
+ message requires the recipient to acknowledge the received message, the
+ sender MUST set the SILC_MESSAGE_FLAG_ACK and MUST NOT set the
+ SILC_MESSAGE_FLAG_NOREPLY. When a message with this flag set is received
+ an acknowledgement message MUST be sent back. In the acknowledgement
+ message the sender MUST set the SILC_MESSAGE_FLAG_ACK,
+ SILC_MESSAGE_FLAG_AUTOREPLY and SILC_MESSAGE_FLAG_NOREPLY flags. The
+ receiver MUST NOT acknowledge the acknowledgement message. This flag
+ MUST NOT be used with channel messages, and MUST be ignored if received
+ in a channel message.
+
+ The construction of the acknowledgement reply message is normal Message
+ Payload where the Message Data field includes a computed MAC of the
+ original received Message Payload MAC. Hence, the MAC is computed as
+ follows:
+
+ ack_mac = mac(key, MAC);
+
+ Where the 'key' is the MAC key used to compute MACs for the Message
+ Payload, and the 'MAC' is the MAC taken from the received Message Payload.
+ The 'ack_mac' is placed in the Message Data field in a new Message
+ Payload, and the payload is encrypted in normal manner. After this the
+ message is sent back to the original sender of the message.
+
+ The receiver of the acknowledgement reply message SHOULD verify the MAC
+ from the Message Data field to assure that acknowledgement was received to
+ an earlier sent message. Implementation needs to keep the old message
+ MACs stored until acknowledgement is received. It is left for
+
+
+
+Riikonen [Page 8]
+\f
+Internet Draft 2 December 2003
+
+
+ implementation to decide any possible retransmission strategy if
+ acknowledgement messages are not received.
+
+
+4 Security Considerations
+
+ In case of SILC_MESSAGE_FLAG_DATA the implementors should pay special
+ attention to the security implications of any media type that can cause
+ the remote execution of any actions in the receiver's environment. The
+ [RFC2046] and [RFC2048] discusses more MIME specific security
+ considerations. Even though SILC provides secured messages, in case of
+ MIME which can be used to transfer files and documents which are stored in
+ the receiver's local environment, securing separately the MIME object may
+ be desired. For example, augmenting the MIME support in SILC messages to
+ support S/MIME may be desired in some implementations.
+
+
+5 References
+
+ [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, June 2003.
+
+ [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
+ June 2003.
+
+ [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
+ Protocols", Internet Draft, June 2003.
+
+ [RFC2045] Freed, N., et al., "Multipurpose Internet Mail Extensions
+ (MIME) Part One: Format of Internet Message Bodies",
+ Standards Track, RFC 2045, November 1996.
+
+ [RFC2046] Freed, N., et al., "Multipurpose Internet Mail Extensions
+ (MIME) Part Two: Media Types", Standards Track, RFC 2045,
+ November 1996.
+
+ [RFC2047] Moore K., "MIME (Multipurpose Internet Mail Extensions)
+ Part Three: Message Header Extensions for Non-ASCII Text"
+ Standards Track, RFC 2047, November 1996.
+
+ [RFC2048] Freed, N., et al., "Multipurpose Internet Mail Extensions
+ (MIME) Part Four: Registration Procedures", Standards
+ Track, RFC 2048, November 1996.
+
+ [RFC2049] Freed, N., et al., "Multipurpose Internet Mail Extensions
+ (MIME) Part Five: Conformance Criteria and Examples",
+ Standards Track, RFC 2049, November 1996.
+
+
+
+
+Riikonen [Page 9]
+\f
+Internet Draft 2 December 2003
+
+
+ [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+
+
+6 Author's Address
+
+ Pekka Riikonen
+ Snellmaninkatu 34 A 15
+ 70100 Kuopio
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+
+7 Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 10]
+\f
--- /dev/null
+
+
+
+
+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-silc-ke-auth-09.txt 15 January 2007
+Expires: 15 July 2007
+
+
+ SILC Key Exchange and Authentication Protocols
+ <draft-riikonen-silc-ke-auth-09.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+Abstract
+
+ This memo describes two protocols used in the Secure Internet Live
+ Conferencing (SILC) protocol, specified in the Secure Internet Live
+ Conferencing, Protocol Specification [SILC1]. The SILC Key Exchange
+ (SKE) protocol provides secure key exchange between two parties
+ resulting into shared secret key material. The protocol is based
+ on Diffie-Hellman key exchange algorithm and its functionality is
+ derived from several key exchange protocols.
+
+ The second protocol, SILC Connection Authentication protocol provides
+ user level authentication used when creating connections in SILC
+ network. The protocol supports passphrase (pre-shared secret)
+ authentication and public key (and certificate) authentication based
+ on digital signatures.
+
+
+
+
+
+
+Riikonen [Page 1]
+\f
+Internet-Draft 15 January 2007
+
+
+Table of Contents
+
+ 1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 3
+ 2 SILC Key Exchange Protocol .................................... 3
+ 2.1 Key Exchange Payloads ..................................... 4
+ 2.1.1 Key Exchange Start Payload .......................... 4
+ 2.1.2 Key Exchange Payload ................................ 9
+ 2.2 Key Exchange Procedure .................................... 11
+ 2.3 Processing the Key Material ............................... 13
+ 2.4 SILC Key Exchange Groups .................................. 15
+ 2.4.1 diffie-hellman-group1 ............................... 15
+ 2.4.2 diffie-hellman-group2 ............................... 15
+ 2.4.3 diffie-hellman-group3 ............................... 16
+ 2.5 Key Exchange Status Types ................................. 16
+ 3 SILC Connection Authentication Protocol ....................... 18
+ 3.1 Connection Auth Payload ................................... 19
+ 3.2 Connection Authentication Types ........................... 20
+ 3.2.1 Passphrase Authentication ........................... 20
+ 3.2.2 Public Key Authentication ........................... 21
+ 3.3 Connection Authentication Status Types .................... 21
+ 4 Security Considerations ....................................... 22
+ 5 References .................................................... 22
+ 6 Author's Address .............................................. 23
+ 7 Full Copyright Statement ...................................... 24
+
+
+List of Figures
+
+ Figure 1: Key Exchange Start Payload
+ Figure 2: Key Exchange Payload
+ Figure 3: Connection Auth Payload
+
+
+1 Introduction
+
+ This memo describes two protocols used in the Secure Internet Live
+ Conferencing (SILC) protocol specified in the Secure Internet Live
+ Conferencing, Protocol Specification [SILC1]. The SILC Key Exchange
+ (SKE) protocol provides secure key exchange between two parties
+ resulting into shared secret key material. The protocol is based on
+ Diffie-Hellman key exchange algorithm and its functionality is derived
+ from several key exchange protocols, such as SSH2 Key Exchange protocol,
+ Station-To-Station (STS) protocol and the OAKLEY Key Determination
+ protocol [OAKLEY].
+
+ The second protocol, SILC Connection Authentication protocol provides
+ user level authentication used when creating connections in SILC
+
+
+
+Riikonen [Page 2]
+\f
+Internet-Draft 15 January 2007
+
+
+ network. The protocol supports passphrase (pre-shared secret)
+ authentication and public key (and certificate) authentication based
+ on digital signatures.
+
+ The basis of secure SILC session requires strong and secure key exchange
+ protocol and authentication. The authentication protocol is secured and
+ no authentication data is ever sent in the network without encrypting
+ and authenticating it first. Thus, authentication protocol may be used
+ only after the key exchange protocol has been successfully completed.
+
+ This document constantly refers to other SILC protocol specifications
+ that should be read to be able to fully understand the functionality
+ and purpose of these protocols. The most important references are
+ the Secure Internet Live Conferencing, Protocol Specification [SILC1]
+ and the SILC Packet Protocol [SILC2].
+
+ The protocol is intended to be used with the SILC protocol thus it
+ does not define own framework that could be used. The framework is
+ provided by the SILC protocol.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+ interpreted as described in [RFC2119].
+
+
+2 SILC Key Exchange Protocol
+
+ SILC Key Exchange Protocol (SKE) is used to exchange shared secret
+ material used to secure the communication channel. The protocol use
+ Diffie-Hellman key exchange algorithm and its functionality is derived
+ from several key exchange protocols, such as SSH2 Key Exchange protocol,
+ Station-To-Station (STS) protocol and the OAKLEY Key Determination
+ protocol [OAKLEY]. The protocol does not claim any conformance
+ to any of these protocols, they were only used as a reference when
+ designing this protocol. The protocol can mutually authenticate the
+ negotiating parties during the key exchange.
+
+ The purpose of SILC Key Exchange protocol is to create session keys to
+ be used in current SILC session. The keys are valid only for some period
+ of time (usually an hour) or at most until the session ends. These keys
+ are used to protect packets traveling between the two entities.
+ Usually all traffic is secured with the key material derived from this
+ protocol.
+
+ The Diffie-Hellman implementation used in the SILC SHOULD be compliant
+
+
+
+Riikonen [Page 3]
+\f
+Internet-Draft 15 January 2007
+
+
+ to the PKCS #3.
+
+
+2.1 Key Exchange Payloads
+
+ During the key exchange procedure public data is sent between initiator
+ and responder. This data is later used in the key exchange procedure.
+ There are several payloads used in the key exchange. As for all SILC
+ packets, SILC Packet Header, described in [SILC2], is at the beginning
+ of all packets sent in during this protocol. All the fields in the
+ following payloads are in MSB (most significant byte first) order.
+
+
+2.1.1 Key Exchange Start Payload
+
+ The key exchange between two entities MUST be started by sending the
+ SILC_PACKET_KEY_EXCHANGE packet containing Key Exchange Start Payload.
+ Initiator sends the Key Exchange Start Payload to the responder filled
+ with all security properties it supports. The responder then checks
+ whether it supports the security properties.
+
+ It then sends a Key Exchange Start Payload to the initiator filled with
+ security properties it selected from the original payload. The payload
+ sent by responder MUST include only one chosen property per list. The
+ character encoding for the security property values as defined in [SILC1]
+ SHOULD be UTF-8 [RFC2279] in Key Exchange Start Payload.
+
+ The Key Exchange Start Payload is used to tell connecting entities what
+ security properties and algorithms should be used in the communication.
+ The Key Exchange Start Payload is sent only once per session. Even if
+ the PFS (Perfect Forward Secrecy) flag is set the Key Exchange Start
+ Payload is not re-sent. When PFS is desired the Key Exchange Payloads
+ are sent to negotiate new key material. The procedure is equivalent to
+ the very first negotiation except that the Key Exchange Start Payload
+ is not sent.
+
+ As this payload is used only with the very first key exchange the payload
+ is never encrypted, as there are no keys to encrypt it with.
+
+ A cookie is also sent in this payload. A cookie is used to randomize the
+ payload so that none of the key exchange parties can determine this
+ payload before the key exchange procedure starts. The cookie MUST be
+ returned to the original sender unmodified by the responder.
+
+ Following diagram represents the Key Exchange Start Payload. The lists
+ mentioned below are always comma (`,') separated and the list MUST NOT
+ include white spaces (` ').
+
+
+
+
+Riikonen [Page 4]
+\f
+Internet-Draft 15 January 2007
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | RESERVED | Flags | Payload Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ + +
+ | |
+ + Cookie +
+ | |
+ + +
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Version String Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Version String ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Key Exchange Grp Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Key Exchange Groups ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | PKCS Alg Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ PKCS Algorithms ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Encryption Alg Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Encryption Algorithms ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Hash Alg Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Hash Algorithms ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | HMAC Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ HMACs ~
+ | |
+
+
+
+Riikonen [Page 5]
+\f
+Internet-Draft 15 January 2007
+
+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Compression Alg Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Compression Algorithms ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 1: Key Exchange Start Payload
+
+
+ o RESERVED (1 byte) - Reserved field. Sender fills this with
+ zero (0) value.
+
+ o Flags (1 byte) - Indicates flags to be used in the key
+ exchange. Several flags can be set at once by ORing the
+ flags together. The following flags are reserved for this
+ field:
+
+ No flags 0x00
+
+ In this case the field is ignored.
+
+ IV Included 0x01
+
+ This flag is used to indicate that Initialization
+ Vector (IV) in encryption will be included in the
+ ciphertext which the recipient must use in decryption.
+ At the beginning of the SILC packet, before the SILC
+ Packet header an 8-bit Security ID (SID) MUST be
+ placed. After the SID, the IV MUST be placed. After
+ the IV, a 32-bit MSB first ordered packet sequence
+ number MUST be placed. The SID and IV MUST NOT be
+ encrypted, but the sequence number MUST be included
+ in encryption. The recipient MUST use the sequence
+ number during MAC verification [SILC2]. All fields
+ however are authenticated with MAC.
+
+ The Security ID is set to value 0 when the key
+ exchange is performed for the first time. It is
+ monotonically increased after each re-key, wrapping
+ eventually. The SID in combination with the current
+ session can be used to identify which key has been
+ used to encrypt an incoming packet. This is especially
+ important after rekey when using UDP/IP protocol,
+ where packets may be lost or reordered. A packet with
+ unknown SID will result into discarding the packet as
+ it cannot be decrypted. After rekey, implementation
+
+
+
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+
+
+ should understand that it may still receive packets
+ with old SID and be prepared to decrypt them with the
+ old key.
+
+ With this flag it is possible to use SILC protocol on
+ unreliable transport such as UDP/IP which may cause
+ packet reordering and packet losses. By default,
+ this flag is not set and thus IV is not included
+ in the ciphertext. Setting this flag increases the
+ packet length by one ciphertext block plus 1 byte for
+ the Security ID and 32 bits for the sequence number.
+ Responder MAY override this flag for the initiator,
+ however without this flag UDP connection cannot be
+ used. The flag MAY also be used in TCP connection.
+
+ When using with UDP/IP implementations SHOULD use
+ anti-replay methods where an anti-replay window
+ defines what packets are replays. An example of
+ anti-window protocol is in [RFC2406] Section 3.4.2
+ with example source code in [RFC2401] Appendix C.
+ While [RFC2401] and [RFC2406] does not relate to SILC,
+ the anti-replay method used is applicable in SILC.
+
+ PFS 0x02
+
+ Perfect Forward Secrecy (PFS) to be used in the
+ key exchange protocol. If not set, re-keying
+ is performed using the old key. See the [SILC1]
+ for more information on this issue. When PFS is
+ used, re-keying and creating new keys for any
+ particular purpose MUST cause new key exchange with
+ new Diffie-Hellman exponent values. In this key
+ exchange only the Key Exchange Payload is sent and
+ the Key Exchange Start Payload MUST NOT be sent.
+ When doing PFS the Key Exchange Payloads are
+ encrypted with the old keys.
+
+ Mutual Authentication 0x04
+
+ Both of the parties will perform authentication
+ by providing signed data for the other party to
+ verify. By default, only responder will provide
+ the signature data. If this is set then the
+ initiator must also provide it. Initiator MAY
+ set this but also responder MAY set this even if
+ initiator did not set it.
+
+ Rest of the flags are reserved for the future and
+
+
+
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+
+ MUST NOT be set.
+
+ o Payload Length (2 bytes) - Length of the entire Key Exchange
+ Start payload, not including any other field.
+
+ o Cookie (16 bytes) - Cookie that randomize this payload so
+ that each of the party cannot determine the payload before
+ hand. This field MUST be present.
+
+ o Version String Length (2 bytes) - The length of the Version
+ String field, not including any other field.
+
+ o Version String (variable length) - Indicates the version of
+ the sender of this payload. Initiator sets this when sending
+ the payload and responder sets this when it replies by sending
+ this payload. See [SILC1] for definition for the version
+ string format. This field MUST be present and include valid
+ version string.
+
+ o Key Exchange Grp Length (2 bytes) - The length of the
+ key exchange group list, not including any other field.
+
+ o Key Exchange Group (variable length) - The list of
+ key exchange groups. See the section 2.4 SILC Key Exchange
+ Groups for definitions of these groups. This field MUST
+ be present.
+
+ o PKCS Alg Length (2 bytes) - The length of the PKCS algorithms
+ list, not including any other field.
+
+ o PKCS Algorithms (variable length) - The list of PKCS
+ algorithms. This field MUST be present.
+
+ o Encryption Alg Length (2 bytes) - The length of the encryption
+ algorithms list, not including any other field.
+
+ o Encryption Algorithms (variable length) - The list of
+ encryption algorithms. This field MUST be present.
+
+ o Hash Alg Length (2 bytes) - The length of the Hash algorithm
+ list, not including any other field.
+
+ o Hash Algorithms (variable length) - The list of Hash
+ algorithms. The hash algorithms are mainly used in the
+ SKE protocol. This field MUST be present.
+
+ o HMAC Length (2 bytes) - The length of the HMAC list, not
+ including any other field.
+
+
+
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+
+
+ o HMACs (variable length) - The list of HMACs. The HMAC's
+ are used to compute the Message Authentication Code (MAC)
+ of the SILC packets. This field MUST be present.
+
+ o Compression Alg Length (2 bytes) - The length of the
+ compression algorithms list, not including any other field.
+
+ o Compression Algorithms (variable length) - The list of
+ compression algorithms. This field MAY be omitted.
+
+
+2.1.2 Key Exchange Payload
+
+ Key Exchange payload is used to deliver the public key (or certificate),
+ the computed Diffie-Hellman public value and possibly signature data
+ from one party to the other. When initiator is using this payload
+ and the Mutual Authentication flag is not set then the initiator MUST
+ NOT provide the signature data. If the flag is set then the initiator
+ MUST provide the signature data so that the responder can verify it.
+
+ The Mutual Authentication flag is usually used when a separate
+ authentication protocol will not be executed for the initiator of the
+ protocol. This is case for example when the SKE is performed between
+ two SILC clients. In normal case, where client is connecting to a
+ server, or server is connecting to a router the Mutual Authentication
+ flag MAY be omitted. However, if the connection authentication protocol
+ for the connecting entity is not based on digital signatures (it is
+ based on pre-shared key or there is no authentication) then the Mutual
+ Authentication flag SHOULD be enabled. This way the connecting entity
+ has to provide proof of possession of the private key for the public key
+ it will provide in this protocol.
+
+ When performing re-key with PFS selected this is the only payload that
+ is sent in the SKE protocol. The Key Exchange Start Payload MUST NOT
+ be sent at all. However, this payload does not have all the fields
+ present. In the re-key with PFS the public key and a possible signature
+ data SHOULD NOT be present. If they are present they MUST be ignored.
+ The only field that is present is the Public Data that is used to create
+ the new key material. In the re-key the Mutual Authentication flag, that
+ may be set in the initial negotiation, MUST also be ignored.
+
+ This payload is sent inside SILC_PACKET_KEY_EXCHANGE_1 and inside
+ SILC_PACKET_KEY_EXCHANGE_2 packet types. The initiator uses the
+ SILC_PACKET_KEY_EXCHANGE_1 and the responder the latter.
+
+ The following diagram represent the Key Exchange Payload.
+
+
+
+
+
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+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Public Key Length | Public Key Type |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Public Key of the party (or certificate) ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Public Data Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Public Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Signature Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Signature Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 2: Key Exchange Payload
+
+
+ o Public Key Length (2 bytes) - The length of the Public Key
+ (or certificate) field, not including any other field.
+
+ o Public Key Type (2 bytes) - The public key (or certificate)
+ type. This field indicates the type of the public key in
+ the packet. Following types are defined:
+
+ 1 SILC style public key (mandatory)
+ 2 SSH2 style public key (optional)
+ 3 X.509 Version 3 certificate (optional)
+ 4 OpenPGP certificate (optional)
+ 5 SPKI certificate (optional)
+
+ The only required type to support is type number 1. See
+ [SILC1] for the SILC public key specification. See
+ SSH2 public key specification in [SSH-TRANS]. See X.509v3
+ certificate specification in [PKIX-Part1]. See OpenPGP
+ certificate specification in [PGP]. See SPKI certificate
+ specification in [SPKI]. If this field includes zero (0)
+ or unsupported type number the protocol MUST be aborted
+ sending SILC_PACKET_FAILURE message and the connection SHOULD
+ be closed immediately.
+
+
+
+
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+
+ o Public Key (or certificate) (variable length) - The
+ public key or certificate of the party. This public key
+ may be used to verify the digital signature. The public key
+ or certificate in this field is encoded in the manner as
+ defined in their respective definitions; see previous field.
+
+ o Public Data Length (2 bytes) - The length of the Public Data
+ field, not including any other field.
+
+ o Public Data (variable length) - The public data to be
+ sent to the receiver (computed Diffie-Hellman public values).
+ See section 2.2 Key Exchange Procedure for detailed description
+ how this field is computed. This field is MP integer and is
+ encoded as defined in [SILC1].
+
+ o Signature Length (2 bytes) - The length of the signature,
+ not including any other field.
+
+ o Signature Data (variable length) - The signature signed
+ by the sender. The receiver of this signature MUST
+ verify it. The verification is done using the sender's
+ public key. See section 2.2 Key Exchange Procedure for
+ detailed description how to produce the signature. If
+ the Mutual Authentication flag is not set then initiator
+ MUST NOT provide this field and the Signature Length field
+ MUST be set to zero (0) value. If the flag is set then
+ also the initiator MUST provide this field. The responder
+ always MUST provide this field. The encoding for signature
+ is defined in [SILC1].
+
+
+
+2.2 Key Exchange Procedure
+
+ The key exchange begins by sending SILC_PACKET_KEY_EXCHANGE packet with
+ Key Exchange Start Payload to select the security properties to be used
+ in the key exchange and later in the communication.
+
+ After Key Exchange Start Payload has been processed by both of the
+ parties the protocol proceeds as follows:
+
+
+ Setup: p is a large and public safe prime. This is one of the
+ Diffie Hellman groups. q is order of subgroup (largest
+ prime factor of p). g is a generator and is defined
+ along with the Diffie Hellman group.
+
+ 1. Initiator generates a random number x, where 1 < x < q,
+
+
+
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+
+
+ and computes e = g ^ x mod p. The result e is then
+ encoded into Key Exchange Payload, with the public key
+ (or certificate) and sent to the responder.
+
+ If the Mutual Authentication flag is set then initiator
+ MUST also produce signature data SIGN_i which the responder
+ will verify. The initiator MUST compute a hash value
+ HASH_i = hash(Initiator's Key Exchange Start Payload |
+ public key (or certificate) | e). The '|' stands for
+ concatenation. It then signs the HASH_i value with its
+ private key resulting a signature SIGN_i.
+
+ 2. Responder generates a random number y, where 1 < y < q,
+ and computes f = g ^ y mod p. It then computes the
+ shared secret KEY = e ^ y mod p, and, a hash value
+ HASH = hash(Initiator's Key Exchange Start Payload |
+ public key (or certificate) | Initiator's public key
+ (or certificate) | e | f | KEY). It then signs
+ the HASH value with its private key resulting a signature
+ SIGN.
+
+ It then encodes its public key (or certificate), f and
+ SIGN into Key Exchange Payload and sends it to the
+ initiator.
+
+ If the Mutual Authentication flag is set then the responder
+ SHOULD verify that the public key provided in the payload
+ is authentic, or if certificates are used it verifies the
+ certificate. The responder MAY accept the public key without
+ verifying it, however, doing so may result to insecure key
+ exchange (accepting the public key without verifying may be
+ desirable for practical reasons on many environments. For
+ long term use this is never desirable, in which case
+ certificates would be the preferred method to use). It then
+ computes the HASH_i value the same way initiator did in the
+ phase 1. It then verifies the signature SIGN_i from the
+ payload with the hash value HASH_i using the received public
+ key.
+
+ 3. Initiator verifies that the public key provided in
+ the payload is authentic, or if certificates are used
+ it verifies the certificate. The initiator MAY accept
+ the public key without verifying it, however, doing
+ so may result to insecure key exchange (accepting the
+ public key without verifying may be desirable for
+ practical reasons on many environments. For long term
+ use this is never desirable, in which case certificates
+ would be the preferred method to use).
+
+
+
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+
+
+ Initiator then computes the shared secret KEY =
+ f ^ x mod p, and, a hash value HASH in the same way as
+ responder did in phase 2. It then verifies the
+ signature SIGN from the payload with the hash value
+ HASH using the received public key.
+
+
+ If any of these phases is to fail the SILC_PACKET_FAILURE MUST be sent
+ to indicate that the key exchange protocol has failed, and the connection
+ SHOULD be closed immediately. Any other packets MUST NOT be sent or
+ accepted during the key exchange except the SILC_PACKET_KEY_EXCHANGE_*,
+ SILC_PACKET_FAILURE and SILC_PACKET_SUCCESS packets.
+
+ The result of this protocol is a shared secret key material KEY and
+ a hash value HASH. The key material itself is not fit to be used as
+ a key, it needs to be processed further to derive the actual keys to be
+ used. The key material is also used to produce other security parameters
+ later used in the communication. See section 2.3 Processing the Key
+ Material for detailed description how to process the key material.
+
+ If the Mutual Authentication flag was set the protocol produces also
+ a hash value HASH_i. This value, however, must be discarded.
+
+ After the keys are processed the protocol is ended by sending the
+ SILC_PACKET_SUCCESS packet. Both entities send this packet to
+ each other. After this both parties MUST start using the new keys.
+
+
+2.3 Processing the Key Material
+
+ Key Exchange protocol produces secret shared key material KEY. This
+ key material is used to derive the actual keys used in the encryption
+ of the communication channel. The key material is also used to derive
+ other security parameters used in the communication. Key Exchange
+ protocol produces a hash value HASH as well.
+
+ The keys MUST be derived from the key material as follows:
+
+ Sending Initial Vector (IV) = hash(0x0 | KEY | HASH)
+ Receiving Initial Vector (IV) = hash(0x1 | KEY | HASH)
+ Sending Encryption Key = hash(0x2 | KEY | HASH)
+ Receiving Encryption Key = hash(0x3 | KEY | HASH)
+ Sending HMAC Key = hash(0x4 | KEY | HASH)
+ Receiving HMAC Key = hash(0x5 | KEY | HASH)
+
+
+ The Initial Vector (IV) is used in the encryption when doing for
+ example CBC mode. As many bytes as needed are taken from the start of
+
+
+
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+
+
+ the hash output for IV. Sending IV is for sending key and receiving IV
+ is for receiving key. For receiving party, the receiving IV is actually
+ sender's sending IV, and, the sending IV is actually sender's receiving
+ IV. Initiator uses IV's as they are (sending IV for sending and
+ receiving IV for receiving).
+
+ The Encryption Keys are derived as well from the hash(). If the hash()
+ output is too short for the encryption algorithm more key material MUST
+ be produced in the following manner:
+
+ K1 = hash(0x2 | KEY | HASH)
+ K2 = hash(KEY | HASH | K1)
+ K3 = hash(KEY | HASH | K1 | K2) ...
+
+ Sending Encryption Key = K1 | K2 | K3 ...
+
+
+ K1 = hash(0x3 | KEY | HASH)
+ K2 = hash(KEY | HASH | K1)
+ K3 = hash(KEY | HASH | K1 | K2) ...
+
+ Receiving Encryption Key = K1 | K2 | K3 ...
+
+
+ The key is distributed by hashing the previous hash with the original
+ key material. The final key is a concatenation of the hash values.
+ For Receiving Encryption Key the procedure is equivalent. Sending key
+ is used only for encrypting data to be sent. The receiving key is used
+ only to decrypt received data. For receiving party, the receive key is
+ actually sender's sending key, and, the sending key is actually sender's
+ receiving key. Initiator uses generated keys as they are (sending key
+ for sending and receiving key for receiving).
+
+ The HMAC keys are used to create MAC values to packets in the
+ communication channel. As many bytes as needed are taken from the start
+ of the hash output to generate the MAC keys.
+
+ These procedures are performed by all parties of the key exchange
+ protocol. This MUST be done before the protocol has been ended by
+ sending the SILC_PACKET_SUCCESS packet, to assure that parties can
+ successfully process the key material.
+
+ This same key processing procedure MAY be used in the SILC in some
+ other circumstances as well. Any changes to this procedure is defined
+ separately when this procedure is needed. See the [SILC1] and the
+ [SILC2] for these circumstances.
+
+
+
+
+
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+
+
+2.4 SILC Key Exchange Groups
+
+ The Following groups may be used in the SILC Key Exchange protocol.
+ The first group diffie-hellman-group1 is REQUIRED, other groups MAY be
+ negotiated to be used in the connection with Key Exchange Start Payload
+ and SILC_PACKET_KEY_EXCHANGE packet. However, the first group MUST be
+ proposed in the Key Exchange Start Payload regardless of any other
+ requested group (however, it does not have to be the first in the list).
+
+
+2.4.1 diffie-hellman-group1
+
+ The length of this group is 1024 bits. This is REQUIRED group.
+ The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
+
+ Its hexadecimal value is
+
+ FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
+ 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
+ EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
+ E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
+ EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
+ FFFFFFFF FFFFFFFF
+
+
+ The generator used with this prime is g = 2. The group order q is
+ (p - 1) / 2.
+
+ This group was taken from RFC 2412.
+
+
+2.4.2 diffie-hellman-group2
+
+ The length of this group is 1536 bits. This is OPTIONAL group.
+ The prime is 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }.
+
+ Its hexadecimal value is
+
+ FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
+ 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
+ EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
+ E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
+ EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D
+ C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F
+ 83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D
+ 670C354E 4ABC9804 F1746C08 CA237327 FFFFFFFF FFFFFFFF
+
+ The generator used with this prime is g = 2. The group order q is
+
+
+
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+
+
+ (p - 1) / 2.
+
+ This group was taken from RFC 3526.
+
+
+2.4.3 diffie-hellman-group3
+
+ The length of this group is 2048 bits. This is OPTIONAL group.
+ This prime is: 2^2048 - 2^1984 - 1 + 2^64 * { [2^1918 pi] + 124476 }.
+
+ Its hexadecimal value is
+
+ FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
+ 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
+ EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
+ E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
+ EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D
+ C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F
+ 83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D
+ 670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B
+ E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9
+ DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510
+ 15728E5A 8AACAA68 FFFFFFFF FFFFFFFF
+
+ The generator used with this prime is g = 2. The group order q is
+ (p - 1) / 2.
+
+ This group was taken from RFC 3526.
+
+ Additional larger groups are defined in RFC 3526 and may be used in SKE
+ by defining name for them using the above name format.
+
+
+2.5 Key Exchange Status Types
+
+ This section defines all key exchange protocol status types that may
+ be returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets
+ to indicate the status of the protocol. Implementations may map the
+ status types to human readable error message. All types except the
+ SILC_SKE_STATUS_OK type MUST be sent in SILC_PACKET_FAILURE packet.
+ The length of status is 32 bits (4 bytes). The following status types
+ are defined:
+
+ 0 SILC_SKE_STATUS_OK
+
+ Protocol were executed successfully.
+
+
+
+
+
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+
+
+ 1 SILC_SKE_STATUS_ERROR
+
+ Unknown error occurred. No specific error type is defined.
+
+
+ 2 SILC_SKE_STATUS_BAD_PAYLOAD
+
+ Provided KE payload were malformed or included bad fields.
+
+
+ 3 SILC_SKE_STATUS_UNSUPPORTED_GROUP
+
+ None of the provided groups were supported.
+
+
+ 4 SILC_SKE_STATUS_UNSUPPORTED_CIPHER
+
+ None of the provided ciphers were supported.
+
+
+ 5 SILC_SKE_STATUS_UNSUPPORTED_PKCS
+
+ None of the provided public key algorithms were supported.
+
+
+ 6 SILC_SKE_STATUS_UNSUPPORTED_HASH_FUNCTION
+
+ None of the provided hash functions were supported.
+
+
+ 7 SILC_SKE_STATUS_UNSUPPORTED_HMAC
+
+ None of the provided HMACs were supported.
+
+
+ 8 SILC_SKE_STATUS_UNSUPPORTED_PUBLIC_KEY
+
+ Provided public key type is not supported.
+
+
+ 9 SILC_SKE_STATUS_INCORRECT_SIGNATURE
+
+ Provided signature was incorrect.
+
+
+ 10 SILC_SKE_STATUS_BAD_VERSION
+
+ Provided version string was not acceptable.
+
+
+
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+
+
+ 11 SILC_SKE_STATUS_INVALID_COOKIE
+
+ The cookie in the Key Exchange Start Payload was malformed,
+ because responder modified the cookie.
+
+
+3 SILC Connection Authentication Protocol
+
+ Purpose of Connection Authentication protocol is to authenticate the
+ connecting party with server. Usually connecting party is client but
+ server may connect to router server as well. Its other purpose is to
+ provide information for the server about which type of entity the
+ connection is. The type defines whether the connection is client,
+ server or router connection. Server use this information to create the
+ ID for the connection.
+
+ Server MUST verify the authentication data received and if it is to fail
+ the authentication MUST be failed by sending SILC_PACKET_FAILURE packet.
+ If authentication is successful the protocol is ended by server by sending
+ SILC_PACKET_SUCCESS packet.
+
+ The protocol is executed after the SILC Key Exchange protocol. It MUST
+ NOT be executed in any other time. As it is performed after key exchange
+ protocol all traffic in the connection authentication protocol is
+ encrypted with the exchanged keys.
+
+ The protocol MUST be started by the connecting party by sending the
+ SILC_PACKET_CONNECTION_AUTH packet with Connection Auth Payload,
+ described in the next section. This payload MUST include the
+ authentication data. The authentication data is set according
+ authentication method that MUST be known by both parties. If connecting
+ party does not know what is the mandatory authentication method it MAY
+ request it from the server by sending SILC_PACKET_CONNECTION_AUTH_REQUEST
+ packet. This packet is not part of this protocol and is described in
+ section Connection Auth Request Payload in [SILC2]. However, if
+ connecting party already knows the mandatory authentication method
+ sending the request is not necessary.
+
+ See [SILC1] and section Connection Auth Request Payload in [SILC2] also
+ for the list of different authentication methods. Authentication method
+ MAY also be NONE, in which case the server does not require
+ authentication. However, in this case the protocol still MUST be
+ executed; the authentication data is empty indicating no authentication
+ is required.
+
+ If authentication method is passphrase the authentication data is
+ plaintext passphrase. As the payload is encrypted it is safe to have
+ plaintext passphrase. It is also provided as plaintext passphrase
+
+
+
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+
+
+ because the receiver may need to pass the entire passphrase into a
+ passphrase verifier, and a message digest of the passphrase would
+ prevent this. See the section 3.2.1 Passphrase Authentication for
+ more information.
+
+ If authentication method is public key authentication the authentication
+ data is a digital signature of the hash value of hash HASH and Key
+ Exchange Start Payload, established by the SILC Key Exchange protocol.
+ This signature MUST then be verified by the server. See the section
+ 3.2.2 Public Key Authentication for more information.
+
+ See the section 4 SILC Procedures in [SILC1] for more information about
+ client creating connection to server, and server creating connection
+ to router, and how to register the session in the SILC Network after
+ successful Connection Authentication protocol.
+
+
+3.1 Connection Auth Payload
+
+ Client sends this payload to authenticate itself to the server. Server
+ connecting to another server also sends this payload. Server receiving
+ this payload MUST verify all the data in it and if something is to fail
+ the authentication MUST be failed by sending SILC_PACKET_FAILURE packet.
+
+ The payload may only be sent with SILC_PACKET_CONNECTION_AUTH packet.
+ It MUST NOT be sent in any other packet type. The following diagram
+ represent the Connection Auth Payload.
+
+
+
+
+
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Connection Type |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Authentication Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 3: Connection Auth Payload
+
+
+ o Payload Length (2 bytes) - Length of the entire Connection
+
+
+
+Riikonen [Page 19]
+\f
+Internet-Draft 15 January 2007
+
+
+ Auth Payload.
+
+ o Connection Type (2 bytes) - Indicates the type of the
+ connection. See section Connection Auth Request Payload
+ in [SILC2] for the list of connection types. This field MUST
+ include valid connection type or the packet MUST be discarded
+ and authentication MUST be failed.
+
+ o Authentication Data (variable length) - The actual
+ authentication data. Contents of this depends on the
+ authentication method known by both parties. If no
+ authentication is required this field does not exist.
+
+
+3.2 Connection Authentication Types
+
+ SILC supports two authentication types to be used in the connection
+ authentication protocol; passphrase authentication or public key
+ authentication based on digital signatures. The following sections
+ defines the authentication methods. See [SILC2] for defined numerical
+ authentication method types.
+
+
+3.2.1 Passphrase Authentication
+
+ Passphrase authentication or pre-shared key based authentication is
+ simply an authentication where the party that wants to authenticate
+ itself to the other end sends the passphrase that is required by
+ the other end, for example server. The plaintext passphrase is put
+ to the payload, that is then encrypted. The plaintext passphrase
+ MUST be in UTF-8 [RFC2279] encoding. If the passphrase is in the
+ sender's system in some other encoding it MUST be UTF-8 encoded
+ before transmitted. The receiver MAY change the encoding of the
+ passphrase to its system's default character encoding before verifying
+ the passphrase.
+
+ If the passphrase matches with the one in the server's end the
+ authentication is successful. Otherwise SILC_PACKET_FAILURE MUST be
+ sent to the sender and the protocol execution fails.
+
+ This is REQUIRED authentication method to be supported by all SILC
+ implementations.
+
+ When password authentication is used it is RECOMMENDED that maximum
+ amount of padding is applied to the SILC packet. This way it is not
+ possible to approximate the length of the password from the encrypted
+ packet.
+
+
+
+
+Riikonen [Page 20]
+\f
+Internet-Draft 15 January 2007
+
+
+3.2.2 Public Key Authentication
+
+ Public key authentication may be used if passphrase based authentication
+ is not desired. The public key authentication works by sending a
+ digital signature as authentication data to the other end, say, server.
+ The server MUST then verify the signature by the public key of the sender,
+ which the server has received earlier in SKE protocol, or which the
+ server has cached locally at some previous time.
+
+ The signature is computed using the private key of the sender by signing
+ the HASH value provided by the SKE protocol previously, and the Key
+ Exchange Start Payload from SKE protocol that was sent to the server.
+ These are concatenated and hash function is used to compute a hash value
+ which is then signed.
+
+ auth_hash = hash(HASH | Key Exchange Start Payload);
+ signature = sign(auth_hash);
+
+ The hash() function used to compute the value is the hash function
+ negotiated in the SKE protocol. The server MUST verify the data, thus
+ it must keep the HASH and the Key Exchange Start Payload saved during
+ SKE and authentication protocols. These values can be discarded after
+ Connection Authentication protocol is completed.
+
+ If the verified signature matches the sent signature, the authentication
+ were successful and SILC_PACKET_SUCCESS is sent. If it failed the
+ protocol execution is stopped and SILC_PACKET_FAILURE is sent.
+
+ This is REQUIRED authentication method to be supported by all SILC
+ implementations.
+
+
+
+3.3 Connection Authentication Status Types
+
+ This section defines all connection authentication status types that
+ may be returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets
+ to indicate the status of the protocol. Implementations may map the
+ status types to human readable error message. All types except the
+ SILC_AUTH_STATUS_OK type MUST be sent in SILC_PACKET_FAILURE packet.
+ The length of status is 32 bits (4 bytes). The following status types
+ are defined:
+
+ 0 SILC_AUTH_OK
+
+ Protocol was executed successfully.
+
+
+
+
+
+Riikonen [Page 21]
+\f
+Internet-Draft 15 January 2007
+
+
+ 1 SILC_AUTH_FAILED
+
+ Authentication failed.
+
+
+4 Security Considerations
+
+ Security is central to the design of this protocol, and these security
+ considerations permeate the specification. Common security considerations
+ such as keeping private keys truly private and using adequate lengths for
+ symmetric and asymmetric keys must be followed in order to maintain the
+ security of this protocol.
+
+
+5 References
+
+ [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, January 2007.
+
+ [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
+ January 2007.
+
+ [SILC4] Riikonen, P., "SILC Commands", Internet Draft, January 2007.
+
+ [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
+ RFC 1459, May 1993.
+
+ [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
+ April 2000.
+
+ [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
+ 2811, April 2000.
+
+ [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
+ 2812, April 2000.
+
+ [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
+ 2813, April 2000.
+
+ [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
+ Internet Draft.
+
+ [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
+ November 1998.
+
+ [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
+ September 1999.
+
+
+
+
+Riikonen [Page 22]
+\f
+Internet-Draft 15 January 2007
+
+
+ [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
+ Infrastructure, Certificate and CRL Profile", RFC 2459,
+ January 1999.
+
+ [Schneier] Schneier, B., "Applied Cryptography Second Edition",
+ John Wiley & Sons, New York, NY, 1996.
+
+ [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
+ CRC Press 1997.
+
+ [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
+ RFC 2412, November 1998.
+
+ [ISAKMP] Maughan D., et al, "Internet Security Association and
+ Key Management Protocol (ISAKMP)", RFC 2408, November
+ 1998.
+
+ [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
+ (IKE)", RFC 2409, November 1998.
+
+ [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
+ Authentication", RFC 2104, February 1997.
+
+ [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
+ Specifications, Version 2.0", RFC 2437, October 1998.
+
+ [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 2279, January 1998.
+
+ [RFC2401] Kent, S., et al, "Security Architecture for the Internet
+ Protocol", RFC 2401, November 1998.
+
+ [RFC2406] Kent, S., et al, "Security Architecture for the Internet
+ Protocol", RFC 2406, November 1998.
+
+
+6 Author's Address
+
+ Pekka Riikonen
+ Helsinki
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+
+
+
+Riikonen [Page 23]
+\f
+Internet-Draft 15 January 2007
+
+
+7 Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 24]
+\f
--- /dev/null
+
+
+
+
+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-silc-multimedia-session-00.txt 15 January 2007
+Expires: 15 July 2007
+
+
+ Multimedia Sessions in SILC protocol
+ <draft-riikonen-silc-multimedia-session-00.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+Abstract
+
+ This document defines the use of multimedia protocols and the set up
+ of multimedia sessions in the Secure Internet Live Conferencing (SILC)
+ protocol [SILC1].
+
+
+Table of Contents
+
+ 1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 2
+ 2 Recommended Protocol .......................................... 2
+ 3 Session Description Protocol (SDP) ............................ 2
+ 3.1 SDP field usage in SILC ................................... 3
+ 3.2 SDP Examples .............................................. 5
+ 4 Session Initiation Protocol (SIP) ............................. 6
+ 5 Other Protocols ............................................... 6
+ 6 Security Considerations ....................................... 7
+
+
+
+Riikonen [Page 1]
+\f
+Internet-Draft 15 January 2007
+
+
+ 7 References .................................................... 7
+ 8 Author's Address .............................................. 7
+ 9 Full Copyright Statement ...................................... 7
+
+
+1 Introduction
+
+ This document defines the use of multimedia protocols and the set up
+ of multimedia sessions in the Secure Internet Live Conferencing (SILC)
+ protocol [SILC1]. The SILC protocol supports multimedia messages
+ with the Message Payload [SILC2] and SILC_MESSAGE_FLAG_DATA which
+ has the ability to define what type of content is delievered within
+ the payload. The Message Payload is used to encapsulate the multimedia
+ session set up procedure and the actual multimedia session data. We
+ define the recommended multimedia session protocol for SILC and also
+ consider some other protocols in the scope of SILC.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+ interpreted as described in [RFC2119].
+
+
+2 Recommended Protocol
+
+ Since SILC protocol can encapsulate practically any protocol for setting
+ up a multimedia session we have selected the Session Description Protocol
+ (SDP) as RECOMMENDED protocol. It was chosen for its maturity, simplicity
+ and versatility. If multimedia features are implemented in SILC
+ application it is recommended that at least support for SDP is added.
+
+
+3 Session Description Protocol (SDP)
+
+ The SDP [SDP] protocol defines a general purpose multimedia session
+ description protocol. SDP is one of the simplest protocols to negotiate
+ multimedia sessions and is suited perfectly for SILC protocol. Since SDP
+ does not itself define how it is used to set up the session, we define it
+ here for SILC. The definition is based on the [RFC3264] and [RFC4145].
+
+ In SILC the SDP messages are sent as data messages (MIME message). They
+ can be destined directly to a client for direct conferencing, or to a
+ channel for group conferencing. It is also possible to send the message
+ directly to client to invite them to group conferencing before they have
+ joined the channel. The MIME type used is application/sdp.
+
+
+
+
+Riikonen [Page 2]
+\f
+Internet-Draft 15 January 2007
+
+
+ To set up a multimedia session a client sends SILC message with
+ SILC_MESSAGE_FLAG_DATA and SILC_MESSAGE_FLAG_REQUEST flags set and with
+ MIME SDP message in the message payload. If the receiver wants to
+ participate in the multimedia session it sends MIME SDP message back with
+ SILC_MESSAGE_FLAG_DATA and SILC_MESSAGE_FLAG_REPLY flags set to the
+ sender. If reply is not received after an application defined period of
+ time the message may be retransmitted or the session set up may be
+ terminated.
+
+ After reply has been received the multimedia session is started according
+ to the SDP and all multimedia data is sent using SILC data messages. When
+ performing peer-to-peer connection the SDP defines which party initiates
+ the connection. After initiation the SILC Key Exchange protocol MUST be
+ performed. The resulted key material will be used to protect the multimedia
+ session. Multimedia data transmission may start after the key exchange
+ has been performed. When performing group conferencing all parties
+ independently connect to the SILC server specified in the SDP. In other
+ cases when performing the multimedia session inside the SILC network, any
+ party may start transmitting the multimedia data after the SDPs have been
+ exchanged.
+
+ To terminate the session, or to reject incoming request, an MD5 digest
+ MUST be computed from the original SDP data, and the digest is sent back
+ with the SILC_MESSAGE_FLAG_DATA and SILC_MESSAGE_FLAG_STOP flags set.
+ The receiver of such message should verify the MD5 digest and terminate
+ the session if it matches any active session. The session may also be
+ terminated by closing network connection. In group sessions simply by
+ leaving the channel terminates the session. The original sender of the
+ SDP message may send the terminating message to notify all clients on the
+ channel to terminate the session. If the original sender on channel
+ receives the terminating message it takes no action on it.
+
+3.1 SDP field usage in SILC
+
+ The Encryption Keys (k=) field describes encryption key to protect the
+ multimedia session. As SILC protocol transport and the multimedia session
+ is secured by default this field SHOULD NOT be used.
+
+
+ The Origin (o=) field describes from where the session originates. The
+ <username> sub-field is the sender's SILC nickname. Examples:
+
+ o=foobar 2890844521 2890842804 IN IP4 10.2.1.7
+
+
+ The Connection Data (c=) field describes the connection information for
+ the multimedia session. When performing peer-to-peer multimedia session
+ the <network type> is 'IN', indicating Internet connection. When
+
+
+
+Riikonen [Page 3]
+\f
+Internet-Draft 15 January 2007
+
+
+ performing multimedia session inside SILC network it is 'SILC'. When
+ the 'SILC' network type is used the <address type> and <connection address>
+ sub-fields are omitted. Examples:
+
+ c=SILC
+ c=IN IP4 10.2.1.7
+
+
+ The Media Announcements (m=) field describes the media information for the
+ multimedia session. If the network type in c= field is 'SILC' the <port>
+ sub-field MUST be set to 9 (discard). The <transport> for RTP over UDP
+ is 'RTP/AVP', for RTP over TCP it is 'TCP/RTP/AVP', and for non-RTP protocol
+ over UDP it is 'udp' and over TCP it is 'tcp'. The <fmt> sub-field
+ includes the RTP media payload number when using RTP. When using non-RTP
+ protocol it includes MIME subtype. Examples:
+
+ c=SILC
+ m=audio 9 TCP/RTP/AVP 3
+ a=rtpmap:3 GSM/8000
+
+ c=SILC
+ m=audio 9 tcp mpeg
+
+
+ The Attributes (a=) field can be used to set various session and media
+ specific attributes. For SILC we define attribute "silc".
+
+ a=silc:<session type> <parameters>
+
+ The <session type> is either "direct" or "group". When it is "direct"
+ and the c= field defines a connection point the connection will be
+ peer-to-peer connection to the remote client. If it is "group" and the
+ the c= field defines a connection point the connection will be to a remote
+ SILC server for group conferencing. If c= field includes "SILC" network
+ type, then "direct" is for direct session with a client in SILC network
+ and "group" is for group conferencing in SILC network. If the "silc"
+ attribute is omitted the session type is expected to be "direct". The
+ following parameters are defined for attribute "silc".
+
+ channel The name of the channel for group conferencing.
+ Can be used only with "group" session type.
+ More than one channel parameters may be defined.
+
+
+ The [RFC4145] specifies a "setup" attribute that defines which party of the
+ session will initiate the connection when performing peer-to-peer session.
+ Its use in SILC is as specified in [RFC4145] and MUST be present in SDP
+ when the c= field includes an actual connection point and when the "silc"
+
+
+
+Riikonen [Page 4]
+\f
+Internet-Draft 15 January 2007
+
+
+ attribute session type is "direct", or if the attribute is not present at
+ all. When performing group conferencing each party always need to create
+ the connection to the server and the "setup" attribute need not be present
+ in SDP.
+
+3.2 SDP Examples
+
+ v=0
+ o=foobar 2890844521 2890842804 IN IP4 10.2.1.100
+ s=peer-to-peer example
+ t=0 0
+ m=audio 5000 TCP/RTP/AVP 3
+ c=IN IP4 10.2.1.100
+ a=rtpmap:3 GSM/8000
+ a=silc:direct
+ a=setup:active
+
+ This example sets up a peer-to-peer session to remote client at
+ 10.2.1.100 at port 5000.
+
+ v=0
+ o=foobar 2890844521 2890842804 IN IP4 10.2.1.32
+ s=Group conferencing example
+ c=IN IP4 10.2.1.7
+ t=0 0
+ a=silc:group channel=foobar
+ m=audio 706 TCP/RTP/AVP 3
+ a=rtpmap:3 GSM/8000
+
+ This example sets up a session to a remote SILC server 10.2.1.7 at port
+ 706. Once connected the channel "foobar" will be joined for group
+ conferencing.
+
+ v=0
+ o=foobar 2890844521 2890842804 IN IP4 10.2.1.32
+ s=SILC network chat example
+ c=SILC
+ t=0 0
+ m=audio 9 TCP/RTP/AVP 3
+ a=rtpmap:3 GSM/8000
+
+ This example sets up a session inside SILC network with the remote user
+ "foobar".
+
+ v=0
+ o=foobar 2890844521 2890842804 IN IP4 10.2.1.32
+ s=SILC network group conferencing example
+ t=0 0
+
+
+
+Riikonen [Page 5]
+\f
+Internet-Draft 15 January 2007
+
+
+ m=audio 9 TCP/RTP/AVP 3
+ c=SILC
+ a=rtpmap:3 GSM/8000
+ a=silc:group channel=group-chat
+
+ This example sets up a group conferencing session inside SILC network on
+ channel "group-chat".
+
+
+4 Session Initiation Protocol (SIP)
+
+ The SIP [SIP] protocol is a general purpose protocol for setting up,
+ modifying and terminating different kinds of sessions, including
+ multimedia sessions. The SIP protocol use the SDP to describe the
+ multimedia session.
+
+ In SILC the SIP messages are sent as data messages (MIME message). They
+ can be destined directly to a client for direct conferencing, or to a
+ channel for group conferencing. It is also possible to send the message
+ directly to client to invite them to group conferencing before they have
+ joined the channel. The MIME type used is application/sip. The
+ SILC_MESSAGE_FLAG_DATA flag must be set in each message and the message
+ payload includes a MIME SIP message. The actual SIP session set up and
+ termination is described in the SIP protocol specification, and SILC
+ protocol merely provides a secure transport for the session. After the
+ session is set up all multimedia data is sent using SILC data messages.
+ The MIME type for the multimedia data messages is defined during the SIP
+ session set up.
+
+ The rules for SDP fields described in previous section also applies for
+ SDP with SIP in the context of SILC.
+
+ Proxy and redirection servers usually would not be used in the context of
+ SILC, unless the sessions are redirected to outside SILC network. This
+ may compromise the security of the session.
+
+ The S/MIME need not be used when using SIP in SILC protocol. The SILC
+ protocol transport and the created multimedia session is secured by
+ default.
+
+
+5 Other Protocols
+
+ There are other open and proprietary protocols for setting up multimedia
+ sessions. One important is H.323 using the H.225 to set up the session.
+ This document should later define the use of H.323 with SILC.
+ Practically any protocol to set up multimedia sessions may be used with
+ SILC by using SILC as a secure transport to set up the session, and to use
+
+
+
+Riikonen [Page 6]
+\f
+Internet-Draft 15 January 2007
+
+
+ SILC data messages (MIME messages) to secure and deliver the actual
+ multimedia data once the session has been established.
+
+
+6 Security Considerations
+
+ Security is central to the design of this protocol, and these security
+ considerations permeate the specification. Common security considerations
+ such as keeping private keys truly private and using adequate lengths for
+ symmetric and asymmetric keys must be followed in order to maintain the
+ security of this protocol.
+
+
+7 References
+
+ [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, June 2003.
+
+ [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
+ June 2003.
+
+ [RFC3264] Rosenberg, J., et. al., "An Offer/Answer Model with the
+ Session Description Protocol (SDP)", RFC 3264, June 2002.
+
+ [RFC4145] Yon, D., et. al., "TCP-Based Media Transport in the
+ Session Description Protocol (SDP)", RFC 4145, September
+ 2005.
+
+ [SIP] Rosenberg, J., et. al., "SIP: Session Initiation Protocol",
+ RFC 3261, June 2002.
+
+
+
+8 Author's Address
+
+ Pekka Riikonen
+ Helsinki
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+9 Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+
+
+
+Riikonen [Page 7]
+\f
+Internet-Draft 15 January 2007
+
+
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 8]
+\f
--- /dev/null
+
+
+
+
+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-silc-pp-09.txt 15 January 2007
+Expires: 15 July 2007
+
+
+ SILC Packet Protocol
+ <draft-riikonen-silc-pp-09.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+
+Abstract
+
+ This memo describes a Packet Protocol used in the Secure Internet Live
+ Conferencing (SILC) protocol, specified in the Secure Internet Live
+ Conferencing, Protocol Specification [SILC1]. This protocol describes
+ the packet types and packet payloads which defines the contents of the
+ packets. The protocol provides secure binary packet protocol that
+ assures that the contents of the packets are secured and authenticated.
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 1]
+\f
+Internet Draft 15 January 2007
+
+
+Table of Contents
+
+ 1 Introduction .................................................. 3
+ 1.1 Requirements Terminology .................................. 4
+ 2 SILC Packet Protocol .......................................... 4
+ 2.1 SILC Packet ............................................... 4
+ 2.2 SILC Packet Header ........................................ 5
+ 2.3 SILC Packet Types ......................................... 8
+ 2.3.1 SILC Packet Payloads ................................ 15
+ 2.3.2 Generic payloads .................................... 16
+ 2.3.2.1 ID Payload .................................. 16
+ 2.3.2.2 Argument Payload ............................ 17
+ 2.3.2.3 Argument List Payload ....................... 17
+ 2.3.2.4 Channel Payload ............................. 18
+ 2.3.2.5 Public Key Payload .......................... 19
+ 2.3.2.6 Message Payload ............................. 20
+ 2.3.3 Disconnect Payload .................................. 23
+ 2.3.4 Success Payload ..................................... 24
+ 2.3.5 Failure Payload ..................................... 25
+ 2.3.6 Reject Payload ...................................... 25
+ 2.3.7 Notify Payload ...................................... 26
+ 2.3.8 Error Payload ....................................... 35
+ 2.3.9 Channel Message Payload ............................. 35
+ 2.3.10 Channel Key Payload ................................ 36
+ 2.3.11 Private Message Payload ............................ 38
+ 2.3.12 Private Message Key Payload ........................ 38
+ 2.3.13 Command Payload .................................... 40
+ 2.3.14 Command Reply Payload .............................. 41
+ 2.3.15 Connection Auth Request Payload .................... 41
+ 2.3.16 New ID Payload ..................................... 42
+ 2.3.17 New Client Payload ................................. 43
+ 2.3.18 New Server Payload ................................. 44
+ 2.3.19 New Channel Payload ................................ 45
+ 2.3.20 Key Agreement Payload .............................. 45
+ 2.3.21 Resume Router Payload .............................. 47
+ 2.3.22 File Transfer Payload .............................. 47
+ 2.3.23 Resume Client Payload .............................. 48
+ 2.3.24 Acknowledgement Payload ............................ 50
+ 2.4 SILC ID Types ............................................. 50
+ 2.5 Packet Encryption And Decryption .......................... 51
+ 2.5.1 Normal Packet Encryption And Decryption ............. 51
+ 2.5.2 Channel Message Encryption And Decryption ........... 52
+ 2.5.3 Private Message Encryption And Decryption ........... 53
+ 2.6 Packet MAC Generation ..................................... 53
+ 2.7 Packet Padding Generation ................................. 54
+ 2.8 Packet Compression ........................................ 54
+ 2.9 Packet Sending ............................................ 55
+ 2.10 Packet Reception ......................................... 55
+
+
+
+Riikonen [Page 2]
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+Internet Draft 15 January 2007
+
+
+ 2.11 Packet Routing ........................................... 55
+ 2.12 Packet Broadcasting ...................................... 57
+ 3 Security Considerations ....................................... 57
+ 4 References .................................................... 57
+ 5 Author's Address .............................................. 59
+ 6 Full Copyright Statement ...................................... 59
+
+List of Figures
+
+ Figure 1: Typical SILC Packet
+ Figure 2: SILC Packet Header
+ Figure 3: ID Payload
+ Figure 4: Argument Payload
+ Figure 5: Argument List Payload
+ Figure 6: Channel Payload
+ Figure 7: Public Key Payload
+ Figure 8: Message Payload
+ Figure 9: Disconnect Payload
+ Figure 10: Success Payload
+ Figure 11: Failure Payload
+ Figure 12: Reject Payload
+ Figure 13: Notify Payload
+ Figure 14: Error Payload
+ Figure 15: Channel Key Payload
+ Figure 16: Private Message Key Payload
+ Figure 17: Command Payload
+ Figure 18: Connection Auth Request Payload
+ Figure 19: New Client Payload
+ Figure 20: New Server Payload
+ Figure 21: Key Agreement Payload
+ Figure 22: Resume Router Payload
+ Figure 23: File Transfer Payload
+ Figure 24: Resume Client Payload
+
+
+1. Introduction
+
+ This document describes a Packet Protocol used in the Secure Internet
+ Live Conferencing (SILC) protocol specified in the Secure Internet Live
+ Conferencing, Protocol Specification [SILC1]. This protocol describes
+ the packet types and packet payloads which defines the contents of the
+ packets. The protocol provides secure binary packet protocol that
+ assures that the contents of the packets are secured and authenticated.
+ The packet protocol is designed to be compact to avoid unnecessary
+ overhead as much as possible. This makes the SILC suitable also in
+ environment of low bandwidth requirements such as mobile networks. All
+ packet payloads can also be compressed to further reduce the size of
+ the packets.
+
+
+
+Riikonen [Page 3]
+\f
+Internet Draft 15 January 2007
+
+
+ All packets in SILC network are always encrypted and their integrity
+ is assured by computed MACs. The protocol defines several packet types
+ and packet payloads. Each packet type usually has a specific packet
+ payload that actually defines the contents of the packet. Each packet
+ also includes a default SILC Packet Header that provides sufficient
+ information about the origin and the destination of the packet.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+ interpreted as described in [RFC2119].
+
+
+2 SILC Packet Protocol
+
+2.1 SILC Packet
+
+ SILC packets deliver messages from sender to receiver securely by
+ encrypting important fields of the packet. The packet consists of
+ default SILC Packet Header, Padding, Packet Payload data, and, packet
+ MAC.
+
+ The following diagram illustrates typical SILC packet.
+
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+ | n bytes | 1 - n bytes | n bytes | n bytes
+ | SILC Header | Padding | Data Payload | MAC
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+ Figure 1: Typical SILC Packet
+
+
+ SILC Header is always the first part of the packet and its purpose
+ is to provide information about the packet. It provides for example
+ the packet type, origin of the packet and the destination of the packet.
+ The header is variable in length. See the following section for
+ description of SILC Packet header. Packets without SILC header or
+ with malformed SILC header MUST be dropped.
+
+ Padding follows the packet header. The purpose of the padding is to
+ make the packet multiple by eight (8) or by the block size of the
+ cipher used in the encryption, which ever is larger. The maximum
+ length of padding is currently 128 bytes. The padding is always
+ encrypted. The padding is applied always, even if the packet is
+ not encrypted. See the section 2.7 Padding Generation for more
+ detailed information.
+
+
+
+Riikonen [Page 4]
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+Internet Draft 15 January 2007
+
+
+ Data payload area follows padding and it is the actual data of the
+ packet. The packet data is the packet payloads defined in this
+ protocol. The data payload area is always encrypted.
+
+ The last part of SILC packet is the packet MAC that assures the
+ integrity of the packet. See the section 2.6 Packet MAC Generation
+ for more information. If compression is used the compression is
+ always applied before encryption.
+
+ All fields in all packet payloads are always in MSB (most significant
+ byte first) order.
+
+
+2.2 SILC Packet Header
+
+ The SILC packet header is applied to all SILC packets and it is
+ variable in length. The purpose of SILC Packet header is to provide
+ detailed information about the packet. The receiver of the packet
+ uses the packet header to parse the packet and gain other relevant
+ parameters of the packet.
+
+ The following diagram represents the SILC packet header.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Flags | Packet Type |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Pad Length | RESERVED | Source ID Len | Dest ID Len |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Src ID Type | |
+ +-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Source ID ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Dst ID Type | |
+ +-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Destination ID ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 2: SILC Packet Header
+
+ o Payload Length (2 bytes) - Indicates the length of the
+ packet not including the padding of the packet.
+
+
+
+
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+
+
+ o Flags (1 byte) - Indicates flags to be used in packet
+ processing. Several flags may be set by ORing the flags
+ together.
+
+ The following flags are reserved for this field:
+
+
+ No flags 0x00
+
+ In this case the field is ignored.
+
+
+ Private Message Key 0x01
+
+ Indicates that the packet data MUST include private
+ message that is encrypted using private key set by
+ client. Servers does not know this key and cannot
+ decrypt the payload, but simply passes it along. See
+ section 2.5.3 Private Message Encryption And Decryption
+ for more information.
+
+
+ List 0x02
+
+ Indicates that the packet consists of list of
+ packet payloads indicated by the Packet Type field.
+ The payloads are added one after the other. Note that
+ there are packet types that must not be used as
+ list. Parsing of list packet is done by calculating
+ the length of each payload and parsing them one by
+ one.
+
+
+ Broadcast 0x04
+
+ Marks the packet to be broadcasted. Client and normal
+ server cannot send broadcast packets. Only router server
+ may send broadcast packet. The router receiving of packet
+ with this flag set MUST send (broadcast) the packet to
+ its primary route. If router has several router connections
+ the packet may be sent only to the primary route. See
+ section 2.12 Packet Broadcasting for description of
+ packet broadcasting.
+
+
+ Compressed 0x08
+
+ Marks that the payload of the packet is compressed.
+
+
+
+Riikonen [Page 6]
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+Internet Draft 15 January 2007
+
+
+ The sender of the packet marks this flag when it
+ compresses the payload, and any server or router
+ en route to the recipient MUST NOT unset this flag.
+ See section 2.8 Packet Compression for description of
+ packet compressing.
+
+
+ Acknowledgement 0x10
+
+ Marks that the packet needs to be acknowledged by the
+ recipient. The ACK packet MUST NOT have this flag set.
+ The acknowledgement packet is SILC_PACKET_ACK packet.
+ If the packet is not acknowledged the packet may be
+ retransmitted. This flag is especially useful when
+ using UDP/IP and SHOULD NOT be used with TCP/IP. The
+ flag MUST NOT be used with message packets. The
+ SILC_MESSAGE_FLAG_ACK can be used instead. Broadcast
+ packets MUST NOT set this flag. Retransmission
+ may use for example exponential backoff algorithm.
+
+
+ o Packet Type (1 byte) - Indicates the type of the packet.
+ Receiver uses this field to parse the packet. See section
+ 2.3 SILC Packets for list of defined packet types.
+
+ o Pad Length (1 byte) - Indicates the length of the padding
+ applied after the SILC Packet header. Maximum length for
+ padding is 128 bytes.
+
+ o RESERVED (1 byte) - Reserved field and must include a
+ zero (0) value.
+
+ o Source ID Length (1 byte) - Indicates the length of the
+ Source ID field in the header, not including this or any
+ other fields.
+
+ o Destination ID Length (1 byte) - Indicates the length of the
+ Destination ID field in the header, not including this or
+ any other fields.
+
+ o Src ID Type (1 byte) - Indicates the type of ID in the
+ Source ID field. See section 2.4 SILC ID Types for
+ defined ID types.
+
+ o Source ID (variable length) - The actual source ID that
+ indicates which is the original sender of the packet.
+
+ o Dst ID Type (1 byte) - Indicates the type of ID in the
+
+
+
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+
+
+ Destination ID field. See section 2.4 SILC ID Types for
+ defined ID types.
+
+ o Destination ID (variable length) - The actual destination
+ ID that indicates which is the end receiver of the packet.
+
+
+
+2.3 SILC Packet Types
+
+ SILC packet types defines the contents of the packet and it is used by
+ the receiver to parse the packet. The packet type is 8 bits in length.
+ The range for the packet types are from 0 - 255, where 0 is never sent and
+ 255 is currently reserved for future extensions and MUST NOT be defined to
+ any other purpose. Every SILC specification compliant implementation
+ SHOULD support all the following packet types.
+
+ The below list of the SILC Packet types includes reference to the packet
+ payload as well. Packet payloads are the actual packet data area. Each
+ packet type defines packet payload which usually may only be sent with
+ the specific packet type.
+
+ Most of the packets are packets that must be destined directly to entity
+ that is connected to the sender. It is not allowed, for example, for a
+ router to send SILC_PACKET_DISCONNECT packet to client that is not
+ directly connected to the router. However, there are some special packet
+ types that may be destined to some entity that the sender does not have
+ direct connection with. These packets are for example private message
+ packets, channel message packets, command packets and some other packets
+ that may be broadcasted in the SILC network. The following packet
+ desription list will define it separately if a packet is allowed to be
+ sent to indirectly connected entity. Other packets MUST NOT be sent or
+ accepted, if sent, to indirectly connected entities.
+
+ Some packets MAY be sent as lists by adding the List flag to the Packet
+ Header and constructing multiple packet payloads one after the other.
+ When this is allowed it is separately defined in the following list.
+ Other packets MUST NOT be sent as list and the List flag MUST NOT be set.
+
+
+ List of SILC Packet types are defined as follows.
+
+ 0 SILC_PACKET_NONE
+
+ This type is reserved and it is never sent.
+
+
+ 1 SILC_PACKET_DISCONNECT
+
+
+
+Riikonen [Page 8]
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+Internet Draft 15 January 2007
+
+
+ This packet is sent to disconnect the remote end. Reason of
+ the disconnection is sent inside the packet payload.
+
+ Payload of the packet: See section 2.3.3 Disconnect Payload
+
+
+ 2 SILC_PACKET_SUCCESS
+
+ This packet is sent upon successful execution of a protocol.
+ The status of the success is sent in the packet payload.
+
+ Payload of the packet: See section 2.3.4 Success Payload
+
+
+ 3 SILC_PACKET_FAILURE
+
+ This packet is sent upon failure of a protocol. The status
+ of the failure is sent in the packet payload.
+
+ Payload of the packet: See section 2.3.5 Failure Payload
+
+
+ 4 SILC_PACKET_REJECT
+
+ This packet MAY be sent upon rejection of a protocol. The
+ status of the rejection is sent in the packet payload.
+
+ Payload of the packet: See section 2.3.6 Reject Payload
+
+
+ 5 SILC_PACKET_NOTIFY
+
+ This packet is used to send notify message. The packet is
+ usually sent between server and client, but also between
+ server and router. Client MUST NOT send this packet. Server
+ MAY destine this packet to channel as well when the packet is
+ distributed to all clients on the channel. This packet MAY
+ be sent as list.
+
+ Payload of the packet: See section 2.3.7 Notify Payload.
+
+
+ 6 SILC_PACKET_ERROR
+
+ This packet is sent when an error occurs. Server MAY
+ send this packet. Client MUST NOT send this packet. The
+ client MAY entirely ignore the packet, however, server is
+ most likely to take action anyway. This packet MAY be sent
+
+
+
+Riikonen [Page 9]
+\f
+Internet Draft 15 January 2007
+
+
+ to entity that is indirectly connected to the sender.
+
+ Payload of the packet: See section 2.3.8 Error Payload.
+
+
+ 7 SILC_PACKET_CHANNEL_MESSAGE
+
+ This packet is used to send messages to channels. The packet
+ includes Channel ID of the channel and the actual message to
+ the channel. Messages sent to the channel are always protected
+ by channel specific keys. This packet MAY be sent to entity
+ that is indirectly connected to the sender.
+
+ Payload of the packet: See section 2.3.9 Channel Message
+ Payload
+
+
+ 8 SILC_PACKET_CHANNEL_KEY
+
+ This packet is used to distribute new key for particular
+ channel when server generates it. Each channel has their own
+ independent keys that is used to protect the traffic on the
+ channel. It is also possible to use channel private keys that
+ are not server generated. In this case this packet is not used.
+ Client MUST NOT send this packet. This packet MAY be sent to
+ entity that is indirectly connected to the sender.
+
+ Payload of the packet: See section 2.3.10 Channel Key Payload
+
+
+ 9 SILC_PACKET_PRIVATE_MESSAGE
+
+ This packet is used to send private messages from client
+ to another client. By default, private messages are protected
+ by session keys established by normal key exchange protocol.
+ However, it is possible to use specific key to protect private
+ messages. See [SILC1] for private message key generation.
+ This packet MAY be sent to entity that is indirectly connected
+ to the sender.
+
+ Payload of the packet: See section 2.3.11 Private Message
+ Payload
+
+
+ 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
+
+ This packet is OPTIONAL and sender of the packet can indicate
+ that a private message key should be used in private message
+
+
+
+Riikonen [Page 10]
+\f
+Internet Draft 15 January 2007
+
+
+ communication. The actual key material is not sent in this
+ packet but must be either static or pre-shared key. The
+ receiver of the packet is considered to be the responder
+ when processing the static or pre-shared key material as
+ defined in [SILC1] and [SILC3] for private message keys.
+ This packet MAY be sent to entity that is indirectly connected
+ to the sender.
+
+ Payload of the packet: See section 2.3.12 Private Message
+ Key Payload
+
+
+ 11 SILC_PACKET_COMMAND
+
+ This packet is used to send commands from client to server.
+ Server MAY send this packet to other servers as well. All
+ commands are listed in their own section SILC Command Types
+ in [SILC4]. The contents of this packet is command specific.
+ This packet MAY be sent to entity that is indirectly connected
+ to the sender.
+
+ Payload of the packet: See section 2.3.13 Command Payload
+
+
+ 12 SILC_PACKET_COMMAND_REPLY
+
+ This packet is sent as reply to the SILC_PACKET_COMMAND packet.
+ The contents of this packet is command specific. This packet
+ MAY be sent to entity that is indirectly connected to the
+ sender. This packet MAY be sent as list.
+
+ Payload of the packet: See section 2.3.14 Command Reply
+ Payload and section 2.3.13 Command
+ Payload
+
+
+ 13 SILC_PACKET_KEY_EXCHANGE
+
+ This packet is used to start SILC Key Exchange Protocol,
+ described in detail in [SILC3].
+
+ Payload of the packet: Payload of this packet is described
+ in the section SILC Key Exchange
+ Protocol and its sub sections in
+ [SILC3].
+
+
+ 14 SILC_PACKET_KEY_EXCHANGE_1
+
+
+
+Riikonen [Page 11]
+\f
+Internet Draft 15 January 2007
+
+
+ This packet is used as part of the SILC Key Exchange Protocol.
+
+ Payload of the packet: Payload of this packet is described
+ in the section SILC Key Exchange
+ Protocol and its sub sections in
+ [SILC3].
+
+
+ 15 SILC_PACKET_KEY_EXCHANGE_2
+
+ This packet is used as part of the SILC Key Exchange Protocol.
+
+ Payload of the packet: Payload of this packet is described
+ in the section SILC Key Exchange
+ Protocol and its sub sections in
+ [SILC3].
+
+
+ 16 SILC_PACKET_CONNECTION_AUTH_REQUEST
+
+ This packet is used to request an authentication method to
+ be used in the SILC Connection Authentication Protocol. If
+ initiator of the protocol does not know the mandatory
+ authentication method this packet MAY be used to determine it.
+ The party receiving this payload SHOULD respond with the same
+ packet including the mandatory authentication method.
+
+ Payload of the packet: See section 2.3.15 Connection Auth
+ Request Payload
+
+
+ 17 SILC_PACKET_CONNECTION_AUTH
+
+ This packet is used to start and perform the SILC Connection
+ Authentication Protocol. This protocol is used to authenticate
+ the connecting party. The protocol is described in detail in
+ [SILC3].
+
+ Payload of the packet: Payload of this packet is described
+ in the section SILC Authentication
+ Protocol and it sub sections in [SILC].
+
+
+ 18 SILC_PACKET_NEW_ID
+
+ This packet is used to distribute new IDs from server to
+ router and from router to all other routers in SILC network.
+ This is used when for example new client is registered to
+
+
+
+Riikonen [Page 12]
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+Internet Draft 15 January 2007
+
+
+ SILC network. The newly created IDs of these operations are
+ distributed by this packet. Only server may send this packet,
+ however, client MUST be able to receive this packet. This
+ packet MAY be sent to entity that is indirectly connected
+ to the sender. This packet MAY be sent as list.
+
+ Payload of the packet: See section 2.3.16 New ID Payload
+
+
+ 19 SILC_PACKET_NEW_CLIENT
+
+ This packet is used by client to register itself to the
+ SILC network. This is sent after key exchange and
+ authentication protocols has been completed. Client sends
+ various information about itself in this packet to the server.
+
+ Payload of the packet: See section 2.3.17 New Client Payload
+
+
+ 20 SILC_PACKET_NEW_SERVER
+
+ This packet is used by server to register itself to the
+ SILC network. This is sent after key exchange and
+ authentication protocols has been completed. Server sends
+ this to the router it connected to, or, if router was
+ connecting, to the connected router. Server sends its
+ Server ID and other information in this packet. The client
+ MUST NOT send or receive this packet.
+
+ Payload of the packet: See section 2.3.18 New Server Payload
+
+
+ 21 SILC_PACKET_NEW_CHANNEL
+
+ This packet is used to notify routers about newly created
+ channel. Channels are always created by the router and it MUST
+ notify other routers about the created channel. Router sends
+ this packet to its primary route. Client MUST NOT send this
+ packet. This packet MAY be sent to entity that is indirectly
+ connected to the sender. This packet MAY be sent as list.
+
+ Payload of the packet: See section 2.3.19 New Channel Payload
+
+
+ 22 SILC_PACKET_REKEY
+
+ This packet is used to indicate that re-key must be performed
+ for session keys. See section Session Key Regeneration in
+
+
+
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+Internet Draft 15 January 2007
+
+
+ [SILC1] for more information. This packet does not have
+ a payload.
+
+
+ 23 SILC_PACKET_REKEY_DONE
+
+ This packet is used to indicate that re-key is performed and
+ new keys must be used hereafter. This packet does not have a
+ payload.
+
+
+ 24 SILC_PACKET_HEARTBEAT
+
+ This packet is used by clients, servers and routers to keep the
+ connection alive. It is RECOMMENDED that all servers implement
+ keepalive actions and perform it to both direction in a link.
+ This packet does not have a payload.
+
+
+ 25 SILC_PACKET_KEY_AGREEMENT
+
+ This packet is used by clients to request key negotiation
+ between another client in the SILC network. If the negotiation
+ is started it is performed using the SKE protocol. The result of
+ the negotiation, the secret key material, can be used for
+ example as private message key. The server and router MUST NOT
+ send this packet.
+
+ Payload of the packet: See section 2.3.20 Key Agreement Payload
+
+
+ 26 SILC_PACKET_RESUME_ROUTER
+
+ This packet is used during backup router protocol when the
+ original primary router of the cell comes back online and wishes
+ to resume the position as being the primary router of the cell.
+
+ Payload of the packet: See section 2.3.21 Resume Router Payload
+
+
+ 27 SILC_PACKET_FTP
+
+ This packet is used to perform an file transfer protocol in the
+ SILC session with some entity in the network. The packet is
+ multi purpose. The packet is used to tell other entity in the
+ network that the sender wishes to perform an file transfer
+ protocol. The packet is also used to actually tunnel the
+ file transfer protocol stream. The file transfer protocol
+
+
+
+Riikonen [Page 14]
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+Internet Draft 15 January 2007
+
+
+ stream is always protected with the SILC binary packet protocol.
+
+ Payload of the packet: See section 2.3.22 File Transfer Payload
+
+
+ 28 SILC_PACKET_RESUME_CLIENT
+
+ This packet is used to resume a client back to the network
+ after it has been detached. A client is able to detach from
+ the network but the client is still valid client in the network.
+ The client may then later resume its session back by sending
+ this packet to a server. Routers also use this packet to notify
+ other routers in the network that the detached client has resumed.
+
+ Payload of the packet: See section 2.3.23 Resume Client Payload
+
+
+ 29 SILC_PACKET_ACK
+
+ This packet is used to acknowledge a packet that had the
+ Acknowledgement packet flag set.
+
+ Payload of the packet: See section 2.3.24 Acknowledgement
+ Payload
+
+
+ 30 - 199
+
+ Currently undefined commands.
+
+
+ 200 - 254
+
+ These packet types are reserved for private use and they will
+ not be defined by this document.
+
+
+ 255 SILC_PACKET_MAX
+
+ This type is reserved for future extensions and currently it
+ MUST NOT be sent.
+
+
+2.3.1 SILC Packet Payloads
+
+ All payloads resides in the main data area of the SILC packet. However
+ all payloads MUST be at the start of the data area after the SILC
+ packet header and padding. All fields in the packet payload are always
+
+
+
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+Internet Draft 15 January 2007
+
+
+ encrypted, as they reside in the data area of the packet which is
+ always encrypted. Most of the payloads may only be sent with specific
+ packet type which is defined in the description of the payload.
+
+ There are some other payloads in SILC as well. However, they are not
+ common in the sense that they could be sent at any time. These payloads
+ are not described in this section. These are payloads such as SILC
+ Key Exchange payloads and so on. These are described in [SILC1],
+ [SILC3] and [SILC4].
+
+
+2.3.2 Generic payloads
+
+ This section describes generic payloads that are not associated to any
+ specific packet type. They can be used for example inside some other
+ packet payload.
+
+
+2.3.2.1 ID Payload
+
+ This payload can be used to send an ID. ID's are variable in length
+ thus this payload provides a way to send variable length ID.
+
+ The following diagram represents the ID Payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | ID Type | ID Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ ID Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 3: ID Payload
+
+
+ o ID Type (2 bytes) - Indicates the type of the ID. See
+ section 2.4 SILC ID Types for list of defined ID types.
+
+ o ID Length (2 bytes) - Length of the ID Data area not
+ including the length of any other fields in the payload.
+
+ o ID Data (variable length) - The actual ID data. The encoding
+ of the ID data is defined in section 2.4 SILC ID Types.
+
+
+
+
+
+Riikonen [Page 16]
+\f
+Internet Draft 15 January 2007
+
+
+2.3.2.2 Argument Payload
+
+ Argument Payload is used to set arguments for any packet payload that
+ need and support arguments, such as commands. Number of arguments
+ associated with a packet MUST be indicated by the packet payload which
+ need the arguments. Argument Payloads MUST always reside right after
+ the packet payload needing the arguments. Incorrect amount of argument
+ payloads MUST cause rejection of the packet.
+
+ The following diagram represents the Argument Payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Data Length | Argument Type | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Argument Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 4: Argument Payload
+
+
+ o Data Length (2 bytes) - Length of the Argument Data field
+ not including the length of any other field in the payload.
+
+ o Argument Type (1 byte) - Indicates the type of the argument.
+ Every argument can have a specific type that are defined
+ by the packet payload needing the argument. For example
+ every command specify a number for each argument that may be
+ associated with the command. By using this number the receiver
+ of the packet knows what type of argument this is. If there is
+ no specific argument type this field is set to zero (0) value.
+
+ o Argument Data (variable length) - Argument data.
+
+
+2.3.2.3 Argument List Payload
+
+ Argument List Payload is a list of Argument Payloads appended one
+ after the other. The number of arguments is indicated in the
+ payload.
+
+ The following diagram represents the Argument List Payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+
+
+
+Riikonen [Page 17]
+\f
+Internet Draft 15 January 2007
+
+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Argument Nums | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Argument Payloads ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 5: Argument List Payload
+
+
+ o Argument Nums (2 bytes) - Indicates the number of Argument
+ Payloads. If zero (0) value is found in this field no
+ arguments are present.
+
+ o Argument Payloads (variable length) - The Argument Payloads
+ appended one after the other. The payloads can be decoded
+ since the length of the payload is indicated in each of
+ the Argument Payload.
+
+
+
+
+
+2.3.2.4 Channel Payload
+
+ Generic Channel Payload may be used to send information about a channel,
+ its name, the Channel ID and a mode.
+
+ The following diagram represents the Channel Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Channel Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Channel Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Channel ID Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Channel ID ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Mode Mask |
+
+
+
+Riikonen [Page 18]
+\f
+Internet Draft 15 January 2007
+
+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 6: New Channel Payload
+
+
+ o Channel Name Length (2 bytes) - Length of the Channel Name
+ field.
+
+ o Channel Name (variable length) - The name of the channel.
+
+ o Channel ID Length (2 bytes) - Length of the Channel ID field.
+
+ o Channel ID (variable length) - The encoded Channel ID.
+
+ o Mode Mask (4 bytes) - A mode. This can be the mode of the
+ channel but it can also be the mode of a client on the
+ channel. The contents of this field is dependent of the
+ usage of this payload. The usage is defined separately
+ when this payload is used. This is a 32 bit MSB first value.
+
+
+
+
+
+
+2.3.2.5 Public Key Payload
+
+ Generic Public Key Payload may be used to send different type of
+ public keys and certificates.
+
+ The following diagram represents the Public Key Payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Public Key Length | Public Key Type |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Public Key (or certificate) ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 7: Public Key Payload
+
+
+ o Public Key Length (2 bytes) - The length of the Public Key
+ (or certificate) field, not including any other field.
+
+
+
+
+Riikonen [Page 19]
+\f
+Internet Draft 15 January 2007
+
+
+ o Public Key Type (2 bytes) - The public key (or certificate)
+ type. This field indicates the type of the public key in
+ the packet. See the [SILC3] for defined public key types.
+
+ o Public Key (or certificate) (variable length) - The
+ encoded public key or certificate data.
+
+
+2.3.2.6 Message Payload
+
+ Generic Message Payload can be used to send messages in SILC. It
+ is used to send channel messages and private messages.
+
+ The following diagram represents the Message Payload.
+
+ (*) indicates that the field is not encrypted.
+
+
+
+
+
+
+
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Message Flags | Message Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Message Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Padding Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Padding ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Initialization Vector * ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ MAC * ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+
+Riikonen [Page 20]
+\f
+Internet Draft 15 January 2007
+
+
+ Figure 8: Message Payload
+
+
+ o Message Flags (2 bytes) - Includes the Message Flags of the
+ message. The flags can indicate a reason or a purpose for
+ the message. The following Message Flags are defined:
+
+ 0x0000 SILC_MESSAGE_FLAG_NONE
+
+ No specific flags set.
+
+ 0x0001 SILC_MESSAGE_FLAG_AUTOREPLY
+
+ This message is an automatic reply to an earlier
+ received message.
+
+ 0x0002 SILC_MESSAGE_FLAG_NOREPLY
+
+ There should not be reply messages to this
+ message.
+
+ 0x0004 SILC_MESSAGE_FLAG_ACTION
+
+ The sender is performing an action and the message
+ is the indication of the action.
+
+ 0x0008 SILC_MESSAGE_FLAG_NOTICE
+
+ The message is for example an informational notice
+ type message.
+
+ 0x0010 SILC_MESSAGE_FLAG_REQUEST
+
+ This is a generic request flag to send request
+ messages. A separate document should define any
+ payloads associated to this flag.
+
+ 0x0020 SILC_MESSAGE_FLAG_SIGNED
+
+ This flag indicates that the message is signed
+ with sender's private key and thus can be verified
+ by the receiver using the sender's public key. A
+ separate document should define the detailed procedure
+ of the signing process and any associated payloads
+ for this flag.
+
+ 0x0040 SILC_MESSAGE_FLAG_REPLY
+
+
+
+
+Riikonen [Page 21]
+\f
+Internet Draft 15 January 2007
+
+
+ This is a generic reply flag to send a reply to
+ previously received request. A separate document
+ should define any payloads associated to this flag.
+
+ 0x0080 SILC_MESSAGE_FLAG_DATA
+
+ This is a generic data flag, indicating that the
+ message includes some data which can be interpreted
+ in a specific way. Using this flag any kind of data
+ can be delivered inside message payload. A separate
+ document should define how this flag is interpreted
+ and define any associated payloads.
+
+ 0x0100 SILC_MESSAGE_FLAG_UTF8
+
+ This flag indicates that the message is UTF-8 encoded
+ textual message. When sending text messages in SILC
+ this flag SHOULD be used. When this flag is used the
+ text sent as message MUST be UTF-8 encoded.
+
+ 0x0200 SILC_MESSAGE_FLAG_ACK
+
+ This flag indicates the sender requires the recpipient
+ to acknowledge the received message. This same flag
+ is used in the acknowledgement. A separate document
+ should define how the acknowledgement is performed.
+
+ 0x0400 - 0x1000 RESERVED
+
+ Reserved for future flags.
+
+ 0x2000 - 0x8000 PRIVATE RANGE
+
+ Private range for free use.
+
+ o Message Length (2 bytes) - Indicates the length of the
+ Message Data field in the payload, not including any
+ other field.
+
+ o Message Data (variable length) - The actual message data.
+
+ o Padding Length (2 bytes) - Indicates the length of the
+ Padding field in the payload, not including any other
+ field.
+
+ o Padding (variable length) - If this payload is used as
+ channel messages, the padding MUST be applied because
+ this payload is encrypted separately from other parts
+
+
+
+Riikonen [Page 22]
+\f
+Internet Draft 15 January 2007
+
+
+ of the packet. If this payload is used as private
+ messages, the padding is present only when the payload
+ is encrypted with private message key. If encrypted
+ with session keys this field MUST NOT be present and the
+ Padding Length field includes a zero (0) value. The
+ padding SHOULD be random data.
+
+ o Initialization Vector (variable length) - This field MUST
+ be present when this payload is used as channel messages.
+ The IV SHOULD be random data for each channel message.
+
+ When encrypting private messages with session keys this
+ field MUST NOT be present. For private messages this field
+ is present only when encrypting with a static private
+ message key (pre-shared key). If randomly generated key
+ material is used this field MUST NOT be present. Also,
+ If Key Agreement (SKE) was used to negotiate fresh key
+ material for private message key this field MUST NOT be
+ present. See the section 4.6 in [SILC1] for more
+ information about IVs when encrypting private messages.
+
+ This field includes the initialization vector used in message
+ encryption. It need to be used in the packet decryption
+ as well. Contents of this field depends on the encryption
+ algorithm and encryption mode. This field is not encrypted,
+ is not included in padding calculation and its length
+ equals to cipher's block size. This field is authenticated
+ by the message MAC.
+
+ o MAC (variable length) - The MAC computed from the
+ Message Flags, Message Length, Message Data, Padding Length,
+ Padding and Initialization Vector fields in that order.
+ The MAC is computed after the payload is encrypted. This
+ is so called Encrypt-Then-MAC order; first encrypt, then
+ compute MAC from ciphertext. The MAC protects the integrity
+ of the Message Payload. Also, when used as channel messages
+ it is possible to have multiple private channel keys set,
+ and receiver can use the MAC to verify which of the keys
+ must be used in decryption. This field is not present
+ when encrypting private messages with session key. This
+ field is not encrypted. This field is authenticated by
+ the SILC packet MAC.
+
+
+2.3.3 Disconnect Payload
+
+ Disconnect payload is sent upon disconnection. Reason of the
+ disconnection is sent to the disconnected party in the payload.
+
+
+
+Riikonen [Page 23]
+\f
+Internet Draft 15 January 2007
+
+
+ The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
+ MUST NOT be sent in any other packet type. The following diagram
+ represents the Disconnect Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Status | |
+ +-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Disconnect Message ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 9: Disconnect Payload
+
+ o Status (1 byte) - Indicates the Status Type, defined in [SILC3]
+ for the reason of disconnection.
+
+ o Disconnect Message (variable length) - Human readable UTF-8
+ encoded string indicating reason of the disconnection. This
+ field MAY be omitted.
+
+
+2.3.4 Success Payload
+
+ Success payload is sent when some protocol execution is successfully
+ completed. The payload is simple; indication of the success is sent.
+ This may be any data, including binary or human readable data, and
+ it is protocol dependent.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Success Indication ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 10: Success Payload
+
+
+ o Success Indication (variable length) - Indication of
+ the success. This may be for example some flag that
+ indicates the protocol and the success status or human
+ readable success message. The true length of this
+ payload is available by calculating it from the SILC
+
+
+
+Riikonen [Page 24]
+\f
+Internet Draft 15 January 2007
+
+
+ Packet Header.
+
+
+2.3.5 Failure Payload
+
+ This is opposite of Success Payload. Indication of failure of
+ some protocol is sent in the payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Failure Indication ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 11: Failure Payload
+
+
+ o Failure Indication (variable length) - Indication of
+ the failure. This may be for example some flag that
+ indicates the protocol and the failure status or human
+ readable failure message. The true length of this
+ payload is available by calculating it from the SILC
+ Packet Header.
+
+
+2.3.6 Reject Payload
+
+ This payload is sent when some protocol is rejected to be executed.
+ Other operations MAY send this as well that was rejected. The
+ indication of the rejection is sent in the payload. The indication
+ may be binary or human readable data and is protocol dependent.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Reject Indication ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 12: Reject Payload
+
+
+ o Reject Indication (variable length) - Indication of
+ the rejection. This maybe for example some flag that
+
+
+
+Riikonen [Page 25]
+\f
+Internet Draft 15 January 2007
+
+
+ indicates the protocol and the rejection status or human
+ readable rejection message. The true length of this
+ payload is available by calculating it from the SILC
+ Packet Header.
+
+
+
+2.3.7 Notify Payload
+
+ Notify payload is used to send notify messages. The payload is usually
+ sent from server to client and from server to router. It is also used
+ by routers to notify other routers in the network. This payload MAY also
+ be sent to a channel. Client MUST NOT send this payload. When this
+ packet is received by client it SHOULD process it. Servers and routers
+ MUST process notify packets.
+
+ The payload may only be sent with SILC_PACKET_NOTIFY packet. It MUST
+ NOT be sent in any other packet type. The following diagram represents
+ the Notify Payload.
+
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Notify Type | Payload Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Argument Nums |
+ +-+-+-+-+-+-+-+-+
+
+ Figure 13: Notify Payload
+
+
+ o Notify Type (2 bytes) - Indicates the type of the notify
+ message.
+
+ o Payload Length (2 bytes) - Length of the entire Notify Payload
+ including any associated Argument Payloads.
+
+ o Argument Nums (1 byte) - Indicates the number of Argument
+ Payloads associated to this payload. Notify types may define
+ arguments to be sent along the notify message.
+
+ Following the list of currently defined notify types. The format for
+ notify arguments is same as in SILC commands described in [SILC4].
+ Note that all IDs sent in arguments are sent inside ID Payload. Also
+ note that all strings sent as arguments MUST be UTF-8 [RFC3629] encoded,
+ unless otherwise defined. Also note that all public keys or
+
+
+
+Riikonen [Page 26]
+\f
+Internet Draft 15 January 2007
+
+
+ certificates sent inside arguments are actually Public Key Payloads.
+
+
+ 0 SILC_NOTIFY_TYPE_NONE
+
+ If no specific notify type apply for the notify message this type
+ MAY be used.
+
+ Max Arguments: 1
+ Arguments: (1) <message>
+
+ The <message> is implementation specific free text string.
+ Receiver MAY ignore this message.
+
+
+ 1 SILC_NOTIFY_TYPE_INVITE
+
+ Sent when an client is invited to a channel. This is also sent
+ when the invite list of the channel is changed. This notify type
+ is sent to local servers on the channel, but MUST NOT be sent
+ to clients on the channel. Router MUST broadcast this to its
+ primary router and to local servers on the channel. When a client
+ was directly invited to the channel this is also sent to that
+ client. In this case the packet is destined to the client.
+
+ Max Arguments: 5
+ Arguments: (1) <Channel ID> (2) <channel name>
+ (3) [<sender Client ID>] (4) [<add | del>]
+ (5) [<invite list>]
+
+ The <Channel ID> is the channel. The <channel name> is the name
+ of the channel and is provided because the client which receives
+ this notify packet may not have a way to resolve the name of the
+ channel from the <Channel ID>. The <sender Client ID> is the
+ Client ID which invited the client to the channel. The
+ <add | del> is an argument of size of 1 byte where 0x00 means
+ adding a client to invite list, and 0x01 means deleting a client
+ from invite list. The <invite list>, if present, indicates the
+ information to be added to or removed from the invite list.
+ The <invite list> format is defined in [SILC4] with
+ SILC_COMMAND_INVITE command. When this notify is destined to
+ a client the <add | del> and <invite list> MUST NOT be sent.
+ When <add | del> is used to announce information during server
+ connecting phase the argument type MUST be 0x03. See section
+ 4.2.1 in [SILC1] for more information.
+
+
+ 2 SILC_NOTIFY_TYPE_JOIN
+
+
+
+Riikonen [Page 27]
+\f
+Internet Draft 15 January 2007
+
+
+ Sent when client has joined to a channel. The server MUST
+ distribute this type to the local clients on the channel and then
+ send it to its primary router. Note that, when router is joining
+ the client on behalf of normal server then router MUST send this
+ notify type locally and globally. The router or server receiving
+ the packet distributes this type to the local clients on the
+ channel and broadcast it to the network. This notify is sent
+ also to the client that joined the channel.
+
+ Max Arguments: 2
+ Arguments: (1) [<Client ID>] (2) <Channel ID>
+
+ The <Client ID> is the client that joined to the channel
+ indicated by the <Channel ID>.
+
+
+ 3 SILC_NOTIFY_TYPE_LEAVE
+
+ Sent when client has left a channel. The server must distribute
+ this type to the local clients on the channel and then send it
+ to its primary router. The router or server receiving the
+ packet distributes this type to the local clients on the channel
+ and broadcast it to the network. This notify MUST NOT be sent to
+ the leaving client.
+
+ Max Arguments: 1
+ Arguments: (1) <Client ID>
+
+ The <Client ID> is the client which left the channel.
+
+
+ 4 SILC_NOTIFY_TYPE_SIGNOFF
+
+ Sent when client signoff from SILC network. The server MUST
+ distribute this type to the local clients on the channel and
+ then send it to its primary router. The router or server
+ receiving the packet distributes this type to the local clients
+ on the channel and broadcast it to the network. This notify
+ MUST NOT be sent to the quitting client. The Destination ID
+ in the packet may be any ID depending to who it is destined.
+
+ Max Arguments: 2
+ Arguments: (1) <Client ID> (2) <message>
+
+ The <Client ID> is the client which left SILC network. The
+ <message> is free text string indicating the reason of the
+ signoff.
+
+
+
+
+Riikonen [Page 28]
+\f
+Internet Draft 15 January 2007
+
+
+ 5 SILC_NOTIFY_TYPE_TOPIC_SET
+
+ Sent when topic is set/changed on a channel. This type may be
+ sent only to the clients which are joined on the channel which
+ topic was just set or changed. The packet is destined to the
+ channel.
+
+ Max Arguments: 2
+ Arguments: (1) <ID Payload> (2) <topic>
+
+ The <ID Payload> is the ID of the entity who set the topic.
+ It usually is Client ID but it can be Server ID and Channel ID
+ as well.
+
+
+ 6 SILC_NOTIFY_TYPE_NICK_CHANGE
+
+ Sent when client changes nick on a channel. The server MUST
+ distribute this type only to the local clients on the channel
+ and then send it to its primary router. The router or server
+ receiving the packet distributes this type to the local clients
+ on the channel and broadcast it to the network. This packet is
+ destined directly to the sent entity. This MUST be sent to those
+ clients that are joined on same channels as the client that
+ changed the nickname. This notify MUST NOT be sent multiple
+ times to the same recipient. This notify MUST be sent also to
+ the client that changed the nickname.
+
+ Max Arguments: 3
+ Arguments: (1) <Old Client ID> (2) <New Client ID>
+ (3) <nickname>
+
+ The <Old Client ID> is the old ID of the client which changed
+ the nickname. The <New Client ID> is the new ID generated by
+ the change of the nickname. The <nickname> is the new nickname.
+ Note that it is possible to send this notify even if the
+ nickname has not changed, but client ID was changed.
+
+
+ 7 SILC_NOTIFY_TYPE_CMODE_CHANGE
+
+ Sent when channel mode has changed. This type MUST be sent only
+ to the clients which are joined on the channel which mode was
+ changed. This packet is destined to the channel.
+
+ Max Arguments: 8
+ Arguments: (1) <ID Payload> (2) <mode mask>
+ (3) [<cipher>] (4) <[hmac>]
+
+
+
+Riikonen [Page 29]
+\f
+Internet Draft 15 January 2007
+
+
+ (5) [<passphrase>] (6) [<founder public key>]
+ (7) [<channel pubkey>] (8) [<user limit>]
+
+ The <ID Payload> is the ID (usually Client ID but it can be
+ Server ID as well when the router is enforcing channel mode
+ change) of the entity which changed the mode. The <mode mask>
+ is the new mode mask of the channel. The client can safely
+ ignore the <cipher> argument since the SILC_PACKET_CHANNEL_KEY
+ packet will force the new channel key change anyway. The <hmac>
+ argument is important since the client is responsible of setting
+ the new HMAC and the hmac key into use. The <passphrase> is
+ the passphrase of the channel, if it was now set. The <founder
+ public key> argument is sent when the founder mode on the
+ channel was set. All routers and servers that receive the packet
+ MUST save the founder's public key so that the founder can
+ reclaim the channel founder rights back for the channel on any
+ server in the network. The <user limit> argument is present when
+ the user limit was set or changed on the channel.
+
+ The <channel pubkey> is an Argument List Payload and it is used
+ to add and/or remove channel public keys from the channel. Also,
+ when announcing channel information between servers and routers
+ during connecting phase this argument includes the list of channel
+ public keys. To add a public key to channel public key list the
+ SILC_CMODE_CHANNEL_AUTH mode is set and the argument type is 0x00,
+ and the argument is the public key. To remove a public key from
+ the channel public key list the argument type is 0x01, and the
+ argument is the public key to be removed. If the mode
+ SILC_CMODE_CHANNEL_AUTH is unset (and was set earlier) all public
+ keys are removed at once. Implementation MAY add and remove
+ multiple public keys at the same time by including multiple
+ arguments to the <channel pubkey> Argument List Payload where each
+ argument is one Public Key Payload. When <channel pubkey> is used
+ to announce information during server connecting phase the
+ argument type MUST be 0x03. See section 4.2.1 in [SILC1] for
+ more information.
+
+
+ 8 SILC_NOTIFY_TYPE_CUMODE_CHANGE
+
+ Sent when user mode on channel has changed. This type MUST be
+ sent only to the clients which are joined on the channel where
+ the target client is on. This packet is destined to the channel.
+
+ Max Arguments: 4
+ Arguments: (1) <ID Payload> (2) <mode mask>
+ (3) <Target Client ID> (4) [<founder pubkey>]
+
+
+
+
+Riikonen [Page 30]
+\f
+Internet Draft 15 January 2007
+
+
+ The <ID Payload> is the ID (usually Client ID but it can be
+ Server ID as well when the router is enforcing user's mode
+ change) of the entity which changed the mode. The <mode mask>
+ is the new mode mask of the channel. The <Target Client ID>
+ is the client which mode was changed. The <founder pubkey>
+ is the public key of the channel founder and may be sent only
+ when first time setting the channel founder mode using the
+ SILC_COMMAND_CUMODE command, and when sending this notify.
+
+
+ 9 SILC_NOTIFY_TYPE_MOTD
+
+ Sent when Message of the Day (motd) is sent to a client.
+
+ Max Arguments: 1
+ Arguments: (1) <motd>
+
+ The <motd> is the Message of the Day. This notify MAY be
+ ignored and is OPTIONAL.
+
+
+ 10 SILC_NOTIFY_TYPE_CHANNEL_CHANGE
+
+ Sent when channel's ID has changed for a reason or another.
+ This is sent by normal server to the client. This can also be
+ sent by router to other server to force the Channel ID change.
+ The Channel ID MUST be changed to use the new one. When sent
+ to clients, this type MUST be sent only to the clients which are
+ joined on the channel. This packet is destined to the sent
+ entity.
+
+ Max Arguments: 2
+ Arguments: (1) <Old Channel ID> (2) <New Channel ID>
+
+ The <Old Channel ID> is the channel's old ID and the <New
+ Channel ID> is the new one that MUST replace the old one.
+ Server which receives this from router MUST re-announce the
+ channel to the router by sending SILC_PACKET_NEW_CHANNEL packet
+ with the new Channel ID.
+
+
+ 11 SILC_NOTIFY_TYPE_SERVER_SIGNOFF
+
+ Sent when server quits SILC network. Those clients from this
+ server that are on channels must be removed from the channel.
+ This packet is destined to the sent entity.
+
+ Max Arguments: 256
+
+
+
+Riikonen [Page 31]
+\f
+Internet Draft 15 January 2007
+
+
+ Arguments: (1) <Server ID> (n) [<Client ID>] [...]
+
+ The <Server ID> is the server's ID. The rest of the arguments
+ are the Client IDs of the clients which are coming from this
+ server and are thus quitting the SILC network also. If the
+ maximum number of arguments are reached another
+ SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify packet MUST be sent.
+ When this notify packet is sent between routers the Client ID's
+ MAY be omitted. Server receiving the Client ID's in the payload
+ may use them directly to remove the client.
+
+
+ 12 SILC_NOTIFY_TYPE_KICKED
+
+ Sent when a client has been kicked from a channel. This MUST
+ also be sent to the client which was kicked from the channel.
+ The client which was kicked from the channel MUST be removed
+ from the channel. The client MUST also be removed from channel's
+ invite list if it is explicitly added in the list. This packet
+ is destined to the channel. The router or server receiving the
+ packet distributes this type to the local clients on the channel
+ and broadcast it to the network.
+
+ Max Arguments: 3
+ Arguments: (1) <Client ID> (2) [<comment>]
+ (3) <Kicker's Client ID>
+
+ The <Client ID> is the client which was kicked from the channel.
+ The kicker may have set the <comment> string to indicate the
+ reason for the kicking. The <Kicker's Client ID> is the kicker.
+
+
+ 13 SILC_NOTIFY_TYPE_KILLED
+
+ Sent when a client has been killed from the network. This MUST
+ also be sent to the client which was killed from the network.
+ This notify MUST be sent to those clients which are joined on
+ same channels as the killed client. The client which was killed
+ MUST be removed from the network. This packet is destined
+ directly to the sent entity. The router or server receiving
+ the packet distributes this type to the local clients on the
+ channel and broadcast it to the network. The client MUST also
+ be removed from joined channels invite list if it is explicitly
+ added in the lists. This notify MUST NOT be sent multiple
+ times to same recipient.
+
+ Max Arguments: 3
+ Arguments: (1) <Client ID> (2) [<comment>]
+
+
+
+Riikonen [Page 32]
+\f
+Internet Draft 15 January 2007
+
+
+ (3) <Killer's ID>
+
+ The <Client ID> is the client which was killed from the network.
+ The killer may have set the <comment> string to indicate the
+ reason for the killing. The <Killer's ID> is the killer, which
+ may be client but also router server.
+
+
+ 14 SILC_NOTIFY_TYPE_UMODE_CHANGE
+
+ Sent when user's mode in the SILC changes. This type is sent
+ only between routers as broadcast packet.
+
+ Max Arguments: 2
+ Arguments: (1) <Client ID> (2) <mode mask>
+
+ The <Client ID> is the client which mode was changed. The
+ <mode mask> is the new mode mask.
+
+
+ 15 SILC_NOTIFY_TYPE_BAN
+
+ Sent when the ban list of the channel is changed. This notify
+ type is sent to local servers on the channel, but MUST NOT be
+ sent to clients on the channel. Router MUST broadcast this to
+ its primary router and to local servers on the channel.
+
+ Max Arguments: 3
+ Arguments: (1) <Channel ID> (2) [<add | del>]
+ (3) [<ban list>]
+
+ The <Channel ID> is the channel which ban list was changed.
+ The <add | del> is an argument of size of 1 byte where 0x00 means
+ adding a client to ban list, and 0x01 means deleting a client
+ from ban list. The <ban list> indicates the information to be
+ added to or removed from the ban list. The <ban list> format
+ format is defined in [SILC4] with SILC_COMMAND_BAN command.
+ When <add | del> is used to announce information during server
+ connecting phase the argument type MUST be 0x03. See section
+ 4.2.1 in [SILC1] for more information.
+
+
+ 16 SILC_NOTIFY_TYPE_ERROR
+
+ Sent when an error occurs during processing some SILC procedure.
+ This is not used when error occurs during command processing, see
+ [SILC4] for more information about commands and command replies.
+ This type is sent directly to the sender of the packet whose
+
+
+
+Riikonen [Page 33]
+\f
+Internet Draft 15 January 2007
+
+
+ packet caused the error. See [SILC1] for definition when this
+ type can be sent.
+
+ Max Arguments: 256
+ Arguments: (1) <Status Type> (n) [...]
+
+ The <Status Type> is the error type defined in [SILC4]. Note
+ that same types are also used with command replies to indicate
+ the status of a command. Both commands and this notify type
+ share same status types. Rest of the arguments are status type
+ dependent and are specified with those status types that can be
+ sent currently inside this notify type in [SILC4]. The <Status
+ Type> is size of 1 byte.
+
+
+ 17 SILC_NOTIFY_TYPE_WATCH
+
+ Sent to indicate change in a watched user. Client can set
+ nicknames to be watched with SILC_COMMAND_WATCH command, and
+ receive notifications when they login to network, signoff from
+ the network or their user mode is changed. This notify type
+ is used to deliver these notifications. The notify type is
+ sent directly to the watching client.
+
+ Max Arguments: 5
+ Arguments: (1) <Client ID> (2) [<nickname>]
+ (3) <user mode> (4) [<Notify Type>]
+ (5) [<public key>]
+
+ The <Client ID> is the user's Client ID which is being watched,
+ and the <nickname> is its nickname. If the client just
+ changed the nickname, then <nickname> is the new nickname, but
+ the <Client ID> is the old client ID. The <user mode> is the
+ user's current user mode. The <Notify Type> can be same as the
+ Notify Payload's Notify Type, and is 16 bit MSB first order
+ value. If provided it may indicate the notify that occurred
+ for the client. If client logged in to the network the
+ <Notify Type> MUST NOT be present. The <public key> MAY be
+ present, and it is the public key of the client being watched.
+
+ Notify types starting from 16384 are reserved for private notify
+ message types.
+
+ Router server which receives SILC_NOTIFY_TYPE_SIGNOFF,
+ SILC_NOTIFY_TYPE_SERVER_SIGNOFF, SILC_NOTIFY_TYPE_KILLED,
+ SILC_NOTIFY_TYPE_NICK_CHANGE and SILC_NOTIFY_TYPE_UMODE_CHANGE
+ MUST check whether someone in the local cell is watching the nickname
+ the client has, and send the SILC_NOTIFY_TYPE_WATCH notify to the
+
+
+
+Riikonen [Page 34]
+\f
+Internet Draft 15 January 2007
+
+
+ watcher, unless the watched client in case has the user mode
+ SILC_UMODE_REJECT_WATCHING set. If the watcher client and the client
+ that was watched is same the notify SHOULD NOT be sent.
+
+
+2.3.8 Error Payload
+
+ Error payload is sent upon error in protocol. Error may occur in
+ various conditions when server sends this packet. Client MUST NOT
+ send this payload but MUST be able to accept it. However, client
+ MAY ignore the contents of the packet as server is going to take
+ action on the error anyway. However, it is recommended that the
+ client takes error packet seriously.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Error Message ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 14: Error Payload
+
+
+ o Error Message (variable length) - Human readable error
+ message.
+
+
+2.3.9 Channel Message Payload
+
+ Channel Message Payload is used to send message to channels, a group
+ of users. These messages can only be sent if client has joined to
+ some channel. Even though this packet is very common in SILC it
+ is still special packet. Some special handling on sending and
+ reception of channel message is required.
+
+ Padding MUST be applied into this payload since the payload is
+ encrypted separately from other parts of the packet with the
+ channel specific key. Hence the requirement of the padding.
+ The packet MUST be made multiple by eight (8) or by the block
+ size of the cipher, which ever is larger.
+
+ The SILC header in this packet is encrypted with the session key
+ of the next receiver of the packet. Nothing else is encrypted
+ with that key. Thus, the actual packet and padding to be
+ encrypted with the session key is SILC Header plus padding to it.
+
+
+
+Riikonen [Page 35]
+\f
+Internet Draft 15 January 2007
+
+
+ Receiver of the the channel message packet is able to determine
+ the channel the message is destined to by checking the Destination
+ ID from the SILC Packet header which tells the destination channel.
+ The original sender of the packet is also determined by checking
+ the source ID from the header which tells the client which sent
+ the message. The Destination ID MUST be Channel ID in the SILC
+ Packet header.
+
+ This packet use generic Message Payload as Channel Message Payload.
+ See section 2.3.2.6 for generic Message Payload.
+
+
+2.3.10 Channel Key Payload
+
+ All traffic in channels are protected by channel specific keys.
+ Channel Key Payload is used to distribute channel keys to all
+ clients on the particular channel. Channel keys are sent when
+ the channel is created, when new user joins to the channel and
+ whenever a user has left a channel. Server creates the new
+ channel key and distributes it to the clients by encrypting this
+ payload with the session key shared between the server and
+ the client. After that, client MUST start using the key received
+ in this payload to protect the traffic on the channel.
+
+ The client which is joining to the channel receives its key in the
+ SILC_COMMAND_JOIN command reply message thus it is not necessary to
+ send this payload to the entity which sent the SILC_COMMAND_JOIN
+ command.
+
+ Channel keys are cell specific thus every router in the cell have
+ to create a channel key and distribute it if any client in the
+ cell has joined to a channel. Channel traffic between cell's
+ are not encrypted using channel keys, they are encrypted using
+ normal session keys between two routers. Inside a cell, all
+ channel traffic is encrypted with the specified channel key.
+ Channel key SHOULD expire periodically, say, in one hour, in
+ which case new channel key is created and distributed.
+
+ Note that, this packet is not used if SILC_CMODE_PRIVKEY mode is set
+ on channel. This means that channel uses channel private keys which
+ are not server generated. For this reason server cannot send this
+ packet as it does not know the key.
+
+ The destination ID in the packet SHOULD be the entity to whom the
+ packet is sent. Using Channel ID as destination ID is not
+ necessary as the Channel ID is included in the Channel Key Payload.
+
+ The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
+
+
+
+Riikonen [Page 36]
+\f
+Internet Draft 15 January 2007
+
+
+ It MUST NOT be sent in any other packet type. The following diagram
+ represents the Channel Key Payload.
+
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Channel ID Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Channel ID ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Cipher Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Cipher Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Channel Key Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Channel Key ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 15: Channel Key Payload
+
+
+
+ o Channel ID Length (2 bytes) - Indicates the length of the
+ Channel ID field in the payload, not including any other
+ field.
+
+ o Channel ID (variable length) - The Channel ID of the
+ channel.
+
+ o Cipher Name Length (2 bytes) - Indicates the length of the
+ Cipher name field in the payload, not including any other
+ field.
+
+ o Cipher Name (variable length) - Name of the cipher used
+ in the protection of channel traffic. This name is
+ initially decided by the creator of the channel but it
+ may change during the life time of the channel as well.
+
+ o Channel Key Length (2 bytes) - Indicates the length of the
+
+
+
+Riikonen [Page 37]
+\f
+Internet Draft 15 January 2007
+
+
+ Channel Key field in the payload, not including any other
+ field.
+
+ o Channel Key (variable length) - The actual channel key
+ material. See [SILC1] on how to start using the key.
+
+
+2.3.11 Private Message Payload
+
+ Private Message Payload is used to send private message between
+ two clients. The messages are sent only to the specified user
+ and no other user inside SILC network is able to see the message.
+
+ The message can be protected by the session key established by the
+ SILC Key Exchange Protocol. However, it is also possible to agree
+ to use a private message key to protect just the private messages.
+ It is for example possible to perform Key Agreement between two
+ clients. See section 2.3.20 Key Agreement Payload how to perform
+ key agreement. It is also possible to use static or pre-shared keys
+ to protect private messages. See the 2.3.12 Private Message Key
+ Payload and [SILC1] section 4.6 for detailed description for private
+ message key generation.
+
+ If normal session key is used to protect the message, every server
+ between the sender client and the receiving client MUST decrypt the
+ packet and always re-encrypt it with the session key of the next
+ receiver of the packet. See section Client To Client in [SILC1].
+
+ When the private message key is used, and the Private Message Key
+ flag was set in the SILC Packet header no server or router en route
+ is able to decrypt or re-encrypt the packet. In this case only the
+ SILC Packet header is processed by the servers and routers en route.
+ Section Client To Client in [SILC1] gives example of this scheme.
+
+ This packet use generic Message Payload as Private Message Payload.
+ See section 2.3.2.6 for generic Message Payload.
+
+
+2.3.12 Private Message Key Payload
+
+ This payload is OPTIONAL and can be used to indicate that a static
+ or pre-shared key should be used in the private message communication
+ to protect the messages. The actual key material has to be sent
+ outside the SILC network, or it has to be a static or pre-shared key.
+ The sender of this packet is considered to be the initiator and the
+ receiver the responder when processing the raw key material as
+ described in the section 4.6 in [SILC1] and in the section 2.3 in
+ [SILC3].
+
+
+
+Riikonen [Page 38]
+\f
+Internet Draft 15 January 2007
+
+
+ Note that it is also possible to use static or pre-shared keys in
+ client implementations without sending this packet. Clients may
+ naturally agree to use a key without sending any kind of indication
+ to each other. The key may be for example a long-living static key
+ that the clients has agreed to use at all times. Note that it is
+ also possible to agree to use private message key by performing
+ a Key Agreement. See the section 2.3.20 Key Agreement Payload.
+
+ This payload may only be sent by client to another client. Server
+ MUST NOT send this payload. After sending this payload and setting the
+ key into use this payload the sender of private messages MUST set the
+ Private Message Key flag into the SILC Packet Header.
+
+ The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
+ packet. It MUST NOT be sent in any other packet type. The following
+ diagram represents the Private Message Key Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Cipher Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Cipher Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | HMAC Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ HMAC Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 16: Private Message Key Payload
+
+
+
+ o Cipher Name Length (2 bytes) - Indicates the length of the
+ Cipher Name field in the payload, not including any other
+ field.
+
+ o Cipher Name (variable length) - Name of the cipher to use
+ in the private message encryption. If this field does not
+ exist then the default cipher of the SILC protocol is used.
+ See the [SILC1] for defined ciphers.
+
+ o HMAC Name Length (2 bytes) - Indicates the length of the
+
+
+
+Riikonen [Page 39]
+\f
+Internet Draft 15 January 2007
+
+
+ HMAC Name field in the payload, not including any other
+ field.
+
+ o HMAC Name (variable length) - Name of the HMAC to use
+ in the private message MAC computation. If this field does
+ not exist then the default HMAC of the SILC protocol is used.
+ See the [SILC1] for defined HMACs.
+
+
+2.3.13 Command Payload
+
+ Command Payload is used to send SILC commands from client to server.
+ Also server MAY send commands to other servers. The following diagram
+ represents the Command Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | SILC Command | Arguments Num |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Command Identifier |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 17: Command Payload
+
+
+ o Payload Length (2 bytes) - Length of the entire command
+ payload including any command argument payloads associated
+ with this payload.
+
+ o SILC Command (1 byte) - Indicates the SILC command. This MUST
+ be set to non-zero value. If zero (0) value is found in this
+ field the packet MUST be discarded.
+
+ o Arguments Num (1 byte) - Indicates the number of arguments
+ associated with the command. If there are no arguments this
+ field is set to zero (0). The arguments MUST follow the
+ Command Payload. See section 2.3.2.2 for definition of the
+ Argument Payload.
+
+ o Command Identifier (2 bytes) - Identifies this command at the
+ sender's end. The entity which replies to this command MUST
+ set the value found from this field into the Command Payload
+ used to send the reply to the sender. This way the sender
+ can identify which command reply belongs to which originally
+ sent command. What this field includes is implementation
+ issue but it is RECOMMENDED that wrapping counter value is
+
+
+
+Riikonen [Page 40]
+\f
+Internet Draft 15 January 2007
+
+
+ used in the field.
+
+ See [SILC4] for detailed description of different SILC commands,
+ their arguments and their reply messages.
+
+
+2.3.14 Command Reply Payload
+
+ Command Reply Payload is used to send replies to the commands. The
+ Command Reply Payload is identical to the Command Payload thus see
+ the 2.3.13 section for the payload specification.
+
+ The entity which sends the reply packet MUST set the Command Identifier
+ field in the reply packet's Command Payload to the value it received
+ in the original command packet.
+
+ See SILC Commands in [SILC4] for detailed description of different
+ SILC commands, their arguments and their reply messages.
+
+
+2.3.15 Connection Auth Request Payload
+
+ Client MAY send this payload to server to request the authentication
+ method that must be used in authentication protocol. If client knows
+ this information beforehand this payload is not necessary to be sent.
+ Server performing authentication with another server MAY also send
+ this payload to request the authentication method. If the connecting
+ server already knows this information this payload is not necessary
+ to be sent.
+
+ Server receiving this request SHOULD reply with same payload sending
+ the mandatory authentication method. Algorithms that may be required
+ to be used by the authentication method are the ones already
+ established by the SILC Key Exchange protocol. See section Key
+ Exchange Start Payload in [SILC3] for detailed information.
+
+ The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
+ packet. It MUST NOT be sent in any other packet type. The following
+ diagram represents the Connection Auth Request Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Connection Type | Authentication Method |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 18: Connection Auth Request Payload
+
+
+
+Riikonen [Page 41]
+\f
+Internet Draft 15 January 2007
+
+
+ o Connection Type (2 bytes) - Indicates the type of the
+ connection. The following connection types are defined:
+
+
+ 1 Client connection
+ 2 Server connection
+ 3 Router connection
+
+ If any other type is found in this field the packet MUST be
+ discarded and the authentication MUST be failed.
+
+ o Authentication Method (2 bytes) - Indicates the authentication
+ method to be used in the authentication protocol. The following
+ authentication methods are defined:
+
+ 0 NONE (mandatory)
+ 1 password (mandatory)
+ 2 public key (mandatory)
+
+ If any other type is found in this field the packet MUST be
+ discarded and the authentication MUST be failed. If this
+ payload is sent as request to receive the mandatory
+ authentication method this field MUST be set to zero (0),
+ indicating that receiver should send the mandatory
+ authentication method. The receiver sending this payload
+ to the requesting party, MAY also set this field to zero (0)
+ to indicate that authentication is not required. In this
+ case authentication protocol still MUST be started but
+ server is most likely to respond with SILC_PACKET_SUCCESS
+ immediately.
+
+
+2.3.16 New ID Payload
+
+ New ID Payload is a multipurpose payload. It is used to send newly
+ created ID's from clients and servers. When client connects to server
+ and registers itself to the server by sending SILC_PACKET_NEW_CLIENT
+ packet, server replies with this packet by sending the created ID for
+ the client. Server always creates the ID for the client.
+
+ This payload is also used when server tells its router that new client
+ has registered to the SILC network. In this case the server sends
+ the Client ID of the client to the router. Similarly when router
+ distributes information to other routers about the client in the SILC
+ network this payload is used.
+
+ Also, when server connects to router, router use this payload to inform
+ other routers about new server in the SILC network. However, every
+
+
+
+Riikonen [Page 42]
+\f
+Internet Draft 15 January 2007
+
+
+ server (or router) creates their own ID's thus the ID distributed by
+ this payload is not created by the distributor in this case. Servers
+ create their own ID's. Server registers itself to the network by
+ sending SILC_PACKET_NEW_SERVER to the router it connected to. The case
+ is same when router connects to another router.
+
+ This payload MUST NOT be used to send information about new channels.
+ New channels are always distributed by sending the dedicated
+ SILC_PACKET_NEW_CHANNEL packet. Client MUST NOT send this payload.
+ Both client and server (and router) MAY receive this payload.
+
+ The packet use generic ID Payload as New ID Payload. See section
+ 2.3.2.1 for generic ID Payload.
+
+
+2.3.17 New Client Payload
+
+ When client is connected to the server, keys has been exchanged and
+ connection has been authenticated, client MUST register itself to the
+ server. Client's first packet after key exchange and authentication
+ protocols MUST be SILC_PACKET_NEW_CLIENT. This payload tells server all
+ the relevant information about the connected user. Server creates a new
+ client ID for the client when received this payload and sends it to the
+ client in New ID Payload.
+
+ This payload sends username and real name of the user on the remote host
+ which is connected to the SILC server with SILC client. The server
+ creates the client ID according the information sent in this payload.
+ The nickname of the user becomes the nickname sent in this payload.
+
+ The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
+ MUST NOT be sent in any other packet type. The following diagram
+ represents the New Client Payload.
+
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Username Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Username ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Real Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+
+
+
+Riikonen [Page 43]
+\f
+Internet Draft 15 January 2007
+
+
+ ~ Real Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 19: New Client Payload
+
+
+ o Username Length (2 bytes) - Length of the Username field.
+
+ o Username (variable length) - The username of the user on
+ the host where connecting to the SILC server.
+
+ o Real Name Length (2 bytes) - Length of the Real Name field.
+
+ o Real Name (variable length) - The real name of the user
+ on the host where connecting to the SILC server.
+
+
+2.3.18 New Server Payload
+
+ This payload is sent by server when it has completed successfully both
+ key exchange and connection authentication protocols. The server
+ MUST register itself to the SILC Network by sending this payload.
+ The first packet after these key exchange and authentication protocols
+ is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
+ of the server that it has created by itself. It also includes a
+ name of the server that is associated to the Server ID.
+
+ The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
+ MUST NOT be sent in any other packet type. The following diagram
+ represents the New Server Payload.
+
+
+
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Server ID Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Server ID Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Server Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+
+
+
+Riikonen [Page 44]
+\f
+Internet Draft 15 January 2007
+
+
+ ~ Server Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 20: New Server Payload
+
+
+ o Server ID Length (2 bytes) - Length of the Server ID Data
+ field.
+
+ o Server ID Data (variable length) - The encoded Server ID
+ data.
+
+ o Server Name Length (2 bytes) - Length of the server name
+ field.
+
+ o Server Name (variable length) - The server name string.
+
+
+2.3.19 New Channel Payload
+
+ Information about newly created channel is broadcasted to all routers
+ in the SILC network by sending this packet payload. Channels are
+ created by router of the cell. Server never creates channels unless
+ it is a standalone server and it does not have router connection,
+ in this case server acts as router. Normal server send JOIN command
+ to the router (after it has received JOIN command from client) which
+ then processes the command and creates the channel. Client MUST NOT
+ send this packet. Server MAY send this packet to a router when it is
+ announcing its existing channels to the router after it has connected
+ to the router.
+
+ The packet use generic Channel Payload as New Channel Payload. See
+ section 2.3.2.3 for generic Channel Payload. The Mode Mask field in the
+ Channel Payload is the mode of the channel.
+
+
+2.3.20 Key Agreement Payload
+
+ This payload is used by clients to request key negotiation between
+ another client in the SILC Network. The key agreement protocol used
+ is the SKE protocol. The result of the protocol, the secret key
+ material, can be used for example as private message key between the
+ two clients. This significantly adds security as the clients agree
+ about the key without any server interaction. The protocol is executed
+ peer to peer. The server and router MUST NOT send this payload.
+
+ The sender MAY tell the receiver of this payload the hostname and the
+
+
+
+Riikonen [Page 45]
+\f
+Internet Draft 15 January 2007
+
+
+ port where the SKE protocol is running in the sender's end. The
+ receiver MAY then initiate the SKE negotiation with the sender. The
+ sender MAY also optionally not to include the hostname and the port
+ of its SKE protocol. In this case the receiver MAY reply to the
+ request by sending the same payload filled with the receiver's hostname
+ and the port where the SKE protocol is running. The sender MAY then
+ initiate the SKE negotiation with the receiver.
+
+ This payload may be sent with SILC_PACKET_KEY_AGREEMENT and
+ SILC_PACKET_FTP packet types. It MUST NOT be sent in any other packet
+ types. The following diagram represents the Key Agreement Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Hostname Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Hostname ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Protocol | Port |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 21: Key Agreement Payload
+
+
+ o Hostname Length (2 bytes) - Indicates the length of the
+ Hostname field.
+
+ o Hostname (variable length) - The hostname or IP address where
+ the SKE protocol is running, as UTF-8 encoded string. The sender
+ MAY fill this field when sending the payload. If the receiver
+ sends this payload as reply to the request it MUST fill this field.
+
+ o Protocol (2 bytes) - The internet protocol used for the key
+ agreement connection. Possible values are 0 for TCP and 1 for
+ UDP. Other values are unsupported. This is a 16 bit MSB first
+ order value. If Hostname field is not present, the value in
+ this field is ignored.
+
+ o Port (2 bytes) - The port where the SKE protocol is bound.
+ The sender MAY fill this field when sending the payload. If
+ the receiver sends this payload as reply to the request it
+ MUST fill this field. This is a 16 bit MSB first order value.
+
+
+
+
+
+Riikonen [Page 46]
+\f
+Internet Draft 15 January 2007
+
+
+ After the key material has been received from the SKE protocol it is
+ processed as the [SILC3] describes. If the key material is used as
+ channel private key then the Sending Encryption Key, as defined in
+ [SILC3] is used as the channel private key. Other key material must
+ be discarded. The [SILC1] in section 4.6 defines the way to use the
+ key material if it is intended to be used as private message keys.
+ Any other use for the key material is undefined.
+
+
+2.3.21 Resume Router Payload
+
+ See the [SILC1] for Resume Router protocol where this payload is
+ used. The payload may only be sent with SILC_PACKET_RESUME_ROUTER
+ packet. It MUST NOT be sent in any other packet type. The following
+ diagram represents the Resume Router Payload.
+
+
+ 1
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Type | Session ID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 22: Resume Router Payload
+
+
+ o Type (1 byte) - Indicates the type of the backup resume
+ protocol packet. The type values are defined in [SILC1].
+
+ o Session ID (1 bytes) - Indicates the session ID for the
+ backup resume protocol. The sender of the packet sets this
+ value and the receiver MUST set the same value in subsequent
+ reply packet.
+
+
+
+
+2.3.22 File Transfer Payload
+
+ File Transfer Payload is used to perform file transfer protocol between
+ two entities in the network. The actual file transfer protocol is always
+ encapsulated inside the SILC Packet. The actual data stream is also sent
+ peer to peer outside SILC network.
+
+ When an entity, usually a client wishes to perform file transfer protocol
+ with another client in the network, they perform Key Agreement protocol
+ as described in the section 2.3.20 Key Agreement Payload and in [SILC3],
+ inside File Transfer Payload. After the Key Agreement protocol has been
+
+
+
+Riikonen [Page 47]
+\f
+Internet Draft 15 January 2007
+
+
+ performed the subsequent packets in the data stream will be protected
+ using the new key material. The actual file transfer protocol is also
+ initialized in this stage. All file transfer protocol packets are always
+ encapsulated in the File Transfer Payload and protected with the
+ negotiated key material.
+
+ The payload may only be sent with SILC_PACKET_FTP packet. It MUST NOT
+ be sent in any other packet type. The following diagram represents the
+ File Transfer Payload.
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Type | |
+ +-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 23: File Transfer Payload
+
+
+ o Type (1 byte) - Indicates the type of the file transfer
+ protocol. The following file transfer protocols has been
+ defined:
+
+ 1 Secure File Transfer Protocol (SFTP) (mandatory)
+
+ If zero (0) value or any unsupported file transfer protocol
+ type is found in this field the packet MUST be discarded.
+ The currently mandatory file transfer protocol is SFTP.
+ The SFTP protocol is defined in [SFTP].
+
+ o Data (variable length) - Arbitrary file transfer data. The
+ contents and encoding of this field is dependent of the usage
+ of this payload and the type of the file transfer protocol.
+ When this payload is used to perform the Key Agreement
+ protocol, this field include the Key Agreement Payload,
+ as defined in the section 2.3.20 Key Agreement Payload.
+ When this payload is used to send the actual file transfer
+ protocol data, the encoding is defined in the corresponding
+ file transfer protocol.
+
+
+2.3.23 Resume Client Payload
+
+
+
+
+Riikonen [Page 48]
+\f
+Internet Draft 15 January 2007
+
+
+ This payload is used by client to resume its detached session in the
+ SILC Network. A client is able to detach itself from the network by
+ sending SILC_COMMAND_DETACH command to its server. The network
+ connection to the client is lost but the client remains as valid
+ client in the network. The client is able to resume the session back
+ by sending this packet and including the old Client ID, and an
+ Authentication Payload [SILC1] which the server use to verify with
+ the detached client's public key. This also implies that the
+ mandatory authentication method is public key authentication.
+
+ Server or router that receives this from the client also sends this,
+ without the Authentication Payload, to routers in the network so that
+ they know the detached client has resumed. Refer to the [SILC1] for
+ detailed description how the detaching and resuming procedure is
+ performed.
+
+ The payload may only be sent with SILC_PACKET_RESUME_CLIENT packet. It
+ MUST NOT be sent in any other packet type. The following diagram
+ represents the Resume Client Payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Client ID Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Client ID ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Authentication Payload ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 24: Resume Client Payload
+
+
+ o Client ID Length (1 byte) - The length of the Client ID
+ field not including any other field.
+
+ o Client ID (variable length) - The detached client's Client
+ ID. The client that sends this payload must know the Client
+ ID.
+
+ o Authentication Payload (variable length) - The authentication
+ payload that the server will verify with the detached client's
+ public key. If the server doesn't know the public key, it must
+ retrieve it for example with SILC_COMMAND_GETKEY command.
+
+
+
+Riikonen [Page 49]
+\f
+Internet Draft 15 January 2007
+
+
+2.3.24 Acknowledgement Payload
+
+ This payload is used to acknowledge a packet that had the Acknowledgement
+ packet flag set. The payload includes the sequence number of the packet
+ that had the flag set, which the recipient can use to identify that the
+ packet was acknowledged.
+
+ The payload may only be sent with SILC_PACKET_ACK packet. It
+ MUST NOT be sent in any other packet type. The following diagram
+ represents the Acknowledgement Payload.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packet Sequence Number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 24: Resume Client Payload
+
+
+ o Packet Sequence Number (4 bytes) - The packet sequence number
+ of the packet that had the Acknowledgement flag set.
+
+
+2.4 SILC ID Types
+
+ ID's are used in the SILC network to associate different entities.
+ The following ID's has been defined to be used in the SILC network.
+
+ 0 No ID
+
+ This is used when other ID type is available at the time.
+
+ 1 Server ID
+
+ Server ID to associate servers. See the format of
+ this ID in [SILC1].
+
+ 2 Client ID
+
+ Client ID to associate clients. See the format of
+ this ID in [SILC1].
+
+ 3 Channel ID
+
+ Channel ID to associate channels. See the format of
+ this ID in [SILC1].
+
+
+
+
+Riikonen [Page 50]
+\f
+Internet Draft 15 January 2007
+
+
+ When encoding different IDs into the ID Payload, all fields are always
+ in MSB first order. The IP address, port, and/or the random number
+ are encoded in the MSB first order.
+
+
+2.5 Packet Encryption And Decryption
+
+ SILC packets are encrypted almost entirely. Only the MAC at the end
+ of the packet is never encrypted. The SILC Packet header is the first
+ part of a packet to be encrypted and it is always encrypted with the
+ key of the next receiver of the packet. The data payload area of the
+ packet is always entirely encrypted and it is usually encrypted with
+ the next receiver's key. However, there are some special packet types
+ and packet payloads that require special encryption process. These
+ special cases are described in the next sections. First is described
+ the normal packet encryption process.
+
+
+
+2.5.1 Normal Packet Encryption And Decryption
+
+ Normal SILC packets are encrypted with the session key of the next
+ receiver of the packet. The entire SILC Packet header and the packet
+ data payload is is encrypted with the same key. Padding of the packet
+ is also encrypted always with the session key, also in special cases.
+ Computed MAC of the packet MUST NOT be encrypted.
+
+ Decryption process in these cases are straightforward. The receiver
+ of the packet MUST first decrypt the SILC Packet header, or some parts
+ of it, usually first 16 bytes of it. Then the receiver checks the
+ packet type from the decrypted part of the header and can determine
+ how the rest of the packet must be decrypted. If the packet type is
+ any of the special cases described in the following sections the packet
+ decryption is special. If the packet type is not among those special
+ packet types rest of the packet can be decrypted with the same key.
+ At this point the receiver is also able to determine the length of the
+ packet.
+
+ With out a doubt, this sort of decryption processing causes some
+ overhead to packet decryption, but never the less, is required.
+
+ The MAC of the packet is also verified at this point. The MAC is
+ computed from the ciphertext of the packet so it can be verified
+ at this stage. The length of the packet need to be known to be able
+ to verify the MAC from the ciphertext so the first 16 bytes need to
+ be decrypted to determine the packet length. However, the MAC MUST
+ be verified from the entire ciphertext.
+
+
+
+
+Riikonen [Page 51]
+\f
+Internet Draft 15 January 2007
+
+
+2.5.2 Channel Message Encryption And Decryption
+
+ Channel Messages (Channel Message Payload) are always encrypted with
+ the channel specific key. However, the SILC Packet header is not
+ encrypted with that key. As in normal case, the header is encrypted
+ with the key of the next receiver of the packet. Note that, in this
+ case the encrypted data area is not touched at all; it MUST NOT be
+ re-encrypted with the session key.
+
+ Receiver of a channel message, who ever that is, is REQUIRED to decrypt
+ the SILC Packet header to be able to recognize the packet to be as
+ channel message. This is same procedure as for normal SILC packets.
+ As the receiver founds the packet to be channel message, rest of the
+ packet processing is special. Rest of the SILC Packet header is
+ decrypted with the same session key along with the padding of the
+ packet. After that the packet is protected with the channel specific
+ key and thus can be decrypted only if the receiver is the client on
+ the channel. See section 2.7 Packet Padding Generation for more
+ information about padding on special packets.
+
+ If the receiver of the channel message is router which is routing the
+ message to another router then it MUST decrypt the Channel Message
+ payload too. Between routers (that is, between cells) channel messages
+ are protected with session keys shared between the routers. This
+ causes another special packet processing for channel messages. If
+ the channel message is received from another router then the entire
+ packet, including Channel Message payload, MUST be encrypted with the
+ session key shared between the routers. In this case the packet
+ decryption process is as with normal SILC packets. Hence, if the
+ router is sending channel message to another router the Channel
+ Message payload MUST have been decrypted and MUST be re-encrypted
+ with the session key shared between the another router. In this
+ case the packet encryption is as with any normal SILC packet.
+
+ It must be noted that this is only when the channel messages are sent
+ from router to another router. In all other cases the channel
+ message encryption and decryption is as described before. This
+ different processing of channel messages with router to router
+ connection is because channel keys are cell specific. All cells have
+ their own channel keys thus the channel message traveling from one
+ cell to another MUST be protected as it would be any normal SILC
+ packet.
+
+ If the SILC_CMODE_PRIVKEY channel mode has been set for the channel
+ then the router cannot decrypt the packet as it does not know the
+ private key. In this case the entire packet MUST be encrypted with
+ the session key and sent to the router. The router receiving the
+ packet MUST check the channel mode and decrypt the packet accordingly.
+
+
+
+Riikonen [Page 52]
+\f
+Internet Draft 15 January 2007
+
+
+2.5.3 Private Message Encryption And Decryption
+
+ By default, private message in SILC are protected by session keys.
+ In this case the private message encryption and decryption process is
+ equivalent to normal packet encryption and decryption.
+
+ However, private messages MAY be protected with private message key
+ which causes the packet to be special packet. The procedure in this
+ case is very much alike to channel packets. The actual private message
+ is encrypted with the private message key and other parts of the
+ packet is encrypted with the session key. See 2.7 Packet Padding
+ Generation for more information about padding on special packets.
+
+ The difference from channel message processing is that server or router
+ en route never decrypts the actual private message, as it does not
+ have the key to do that. Thus, when sending packets between router
+ the processing is same as in any other case as well; the packet's header
+ and padding is protected by the session key and the data area is not
+ touched and is not re-encrypted.
+
+ The true receiver of the private message is able to decrypt the private
+ message as it shares the key with the sender of the message.
+
+
+2.6 Packet MAC Generation
+
+ Data integrity of a packet is protected by including a message
+ authentication code (MAC) at the end of the packet. The MAC is computed
+ from shared secret MAC key, that is established by the SILC Key Exchange
+ protocol, from packet sequence number, and from the encrypted packet
+ data. The MAC is always computed after packet is encrypted. This is
+ so called Encrypt-Then-MAC order; packet is first encrypted, then MAC
+ is computed from the encrypted data.
+
+ The MAC is computed from entire packet. Every bit of data in the packet,
+ including SILC Packet Header is used in the MAC computing. This way
+ the entire packet becomes authenticated.
+
+ Hence, packet's MAC generation is as follows:
+
+ mac = MAC(key, sequence number | Encrypted SILC packet)
+
+ The MAC key is negotiated during the SKE protocol. The sequence number
+ is a 32 bit MSB first value starting from zero for first packet and
+ increasing for subsequent packets, finally wrapping after 2^32 packets.
+ The value is never reset, not even after rekey has been performed.
+ However, rekey MUST be performed before the sequence number wraps
+ and repeats from zero. Note that the sequence number is incremented only
+
+
+
+Riikonen [Page 53]
+\f
+Internet Draft 15 January 2007
+
+
+ when MAC is computed for a packet. If packet is not encrypted and MAC is
+ not computed then the sequence number is not incremented. Hence, the
+ sequence number is zero for the very first encrypted packet.
+
+ See [SILC1] for defined and allowed MAC algorithms.
+
+
+2.7 Packet Padding Generation
+
+ Padding is needed in the packet because the packet is encrypted. It
+ always MUST be multiple by eight (8) or multiple by the block size
+ of the cipher, which ever is larger. The padding is always encrypted.
+
+ For normal packets the padding is added after the SILC Packet Header
+ and between the Data Payload area. The padding for normal packets
+ may be calculated as follows:
+
+ padding_length = 16 - (packet_length mod block_size)
+ if (padding_length < 8)
+ padding_length += block_size
+
+ The `block_size' is the block size of the cipher. The maximum padding
+ length is 128 bytes, and minimum is 8 bytes. For example, packets that
+ include a passphrase or a password for authentication purposes SHOULD
+ pad the packet up to the maximum padding length. The maximum padding
+ is calculated as follows:
+
+ padding_length = 128 - (packet_length mod block_size)
+
+ For special packets the padding calculation is different as special
+ packets may be encrypted differently. In these cases the encrypted
+ data area MUST already be multiple by the block size thus in this case
+ the padding is calculated only for SILC Packet Header, not for any
+ other area of the packet. The same algorithm works in this case as
+ well, except that the `packet length' is now the SILC Packet Header
+ length.
+
+ The padding MUST be random data, preferably, generated by
+ cryptographically strong random number generator for each packet
+ separately.
+
+
+2.8 Packet Compression
+
+ SILC Packets MAY be compressed. In this case the data payload area
+ is compressed and all other areas of the packet MUST remain as they
+ are. After compression is performed for the data area, the length
+ field of Packet Header MUST be set to the compressed length of the
+
+
+
+Riikonen [Page 54]
+\f
+Internet Draft 15 January 2007
+
+
+ data.
+
+ The compression MUST always be applied before encryption. When
+ the packet is received and decrypted the data area MUST be decompressed.
+ Note that the true sender of the packet MUST apply the compression and
+ the true receiver of the packet MUST apply the decompression. Any
+ server or router en route SHOULD NOT decompress the packet.
+
+
+2.9 Packet Sending
+
+ The sender of the packet MUST assemble the SILC Packet Header with
+ correct values. It MUST set the Source ID of the header as its own
+ ID, unless it is forwarding the packet. It MUST also set the Destination
+ ID of the header to the true destination. If the destination is client
+ it will be Client ID, if it is server it will be Server ID and if it is
+ channel it will be Channel ID.
+
+ If the sender wants to compress the packet it MUST apply the
+ compression now. Sender MUST also compute the padding as described
+ in above sections. Then sender MUST encrypt the packet as has been
+ described in above sections according whether the packet is normal
+ packet or special packet. Then sender MUST compute the MAC of the
+ packet. The computed MAC MUST NOT be encrypted.
+
+
+2.10 Packet Reception
+
+ On packet reception the receiver MUST check that all fields in the
+ SILC Packet Header are valid. It MUST check the flags of the
+ header and act accordingly. It MUST also check the MAC of the packet
+ and if it is to be failed the packet MUST be discarded. Also if the
+ header of the packet includes any bad fields the packet MUST be
+ discarded.
+
+ See above sections on the decryption process of the received packet.
+
+ The receiver MUST also check that the ID's in the header are valid
+ ID's. Unsupported ID types or malformed ID's MUST cause packet
+ rejection. The padding on the reception is always ignored.
+
+ The receiver MUST also check the packet type and start parsing the
+ packet according to the type. However, note the above sections on
+ special packet types and their parsing.
+
+
+2.11 Packet Routing
+
+
+
+
+Riikonen [Page 55]
+\f
+Internet Draft 15 January 2007
+
+
+ Routers are the primary entities in the SILC network that takes care
+ of packet routing. Normal servers performs packet forwarding, for
+ example, when they are forwarding channel message to the local clients.
+ Routing is quite simple as every packet tells the true origin and the
+ true destination of the packet.
+
+ It is still RECOMMENDED for routers that has several routing connections
+ to create route cache for those destinations that has faster route than
+ the router's primary route. This information is available for the router
+ when other router connects to the router. The connecting party then
+ sends all of its locally connected clients, servers and channels. These
+ informations helps to create the route cache. Also, when new channels
+ are created to a cell its information is broadcasted to all routers
+ in the network. Channel ID's are based on router's ID thus it is easy
+ to create route cache based on these informations. If faster route for
+ destination does not exist in router's route cache the packet MUST be
+ routed to the primary route (default route).
+
+ However, there are some issues when routing channel messages to group
+ of users. Routers are responsible of routing the channel message to
+ other routers, local servers and local clients as well. Routers MUST
+ send the channel message to only one router in the network, preferably
+ to the shortest route to reach the channel users. The message can be
+ routed into either upstream or downstream. After the message is sent
+ to a router in the network it MUST NOT be sent to any other router in
+ either same route or other route. The message MUST NOT be routed to
+ the router it came from.
+
+ When routing for example private messages they should be routed to the
+ shortest route always to reach the destination client as fast as possible.
+
+ For server which receives a packet to be forwarded to an entity that is
+ indirectly connected to the sender, the server MUST check whether that
+ particular packet type is allowed to be sent to that destination. Not
+ all packets may be sent by some odd entity to for example a local client,
+ or to some remote server or router, that is indirectly connected to the
+ sender. See section 2.3 SILC Packet Types and paragraph about indirectly
+ connected entities and sending packets to them. That section defines the
+ packets that may be sent to indirectly connected entities. When a server
+ or a router receives a packet that may be sent to indirectly connected
+ entity and it is destined to other entity except that server, it MUST
+ route it further either to shortest route or to the primary route to reach
+ that destination.
+
+ Routers form a ring in the SILC network. However, routers may have other
+ direct connections to other routers in the network too. This can cause
+ interesting routing problems in the network. Since the network is a ring,
+ the packets usually should be routed into clock-wise direction, or if it
+
+
+
+Riikonen [Page 56]
+\f
+Internet Draft 15 January 2007
+
+
+ cannot be used then always counter clock-wise (primary route) direction.
+ Problems may arise when a faster direct route exists and router is routing
+ a channel message. Currently channel messages must be routed either
+ in upstream or downstream, they cannot be routed to other direct routes.
+ The SILC protocol should have a shortest path discovery protocol, and some
+ existing routing protocol, that can handle a ring network with other
+ direct routes inside the ring (so called hybrid ring-mesh topology),
+ MAY be defined to be used with the SILC protocol. Additional
+ specifications MAY be written on the subject to permeate this
+ specification.
+
+
+2.12 Packet Broadcasting
+
+ SILC packets MAY be broadcasted in SILC network. However, only router
+ server may send or receive broadcast packets. Client and normal server
+ MUST NOT send broadcast packets and they MUST ignore broadcast packets
+ if they receive them. Broadcast packets are sent by setting Broadcast
+ flag to the SILC packet header.
+
+ Broadcasting packets means that the packet is sent to all routers in
+ the SILC network, except to the router that sent the packet. The router
+ receiving broadcast packet MUST send the packet to its primary route.
+ The fact that SILC routers may have several router connections can
+ cause problems, such as race conditions inside the SILC network, if
+ care is not taken when broadcasting packets. Router MUST NOT send
+ the broadcast packet to any other route except to its primary route.
+
+ If the primary route of the router is the original sender of the packet
+ the packet MUST NOT be sent to the primary route. This may happen
+ if router has several router connections and some other router uses
+ the router as its primary route.
+
+ Routers use broadcast packets to broadcast for example information
+ about newly registered clients, servers, channels etc. so that all the
+ routers may keep these informations up to date.
+
+
+3 Security Considerations
+
+ Security is central to the design of this protocol, and these security
+ considerations permeate the specification. Common security considerations
+ such as keeping private keys truly private and using adequate lengths for
+ symmetric and asymmetric keys must be followed in order to maintain the
+ security of this protocol.
+
+
+4 References
+
+
+
+Riikonen [Page 57]
+\f
+Internet Draft 15 January 2007
+
+
+ [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, January 2007.
+
+ [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
+ Protocols", Internet Draft, January 2007.
+
+ [SILC4] Riikonen, P., "SILC Commands", Internet Draft, January 2007.
+
+ [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
+ RFC 1459, May 1993.
+
+ [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
+ April 2000.
+
+ [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
+ 2811, April 2000.
+
+ [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
+ 2812, April 2000.
+
+ [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
+ 2813, April 2000.
+
+ [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
+ Internet Draft.
+
+ [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
+ November 1998.
+
+ [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
+ September 1999.
+
+ [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
+ Infrastructure, Certificate and CRL Profile", RFC 2459,
+ January 1999.
+
+ [Schneier] Schneier, B., "Applied Cryptography Second Edition",
+ John Wiley & Sons, New York, NY, 1996.
+
+ [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
+ CRC Press 1997.
+
+ [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
+ RFC 2412, November 1998.
+
+ [ISAKMP] Maughan D., et al, "Internet Security Association and
+ Key Management Protocol (ISAKMP)", RFC 2408, November
+ 1998.
+
+
+
+Riikonen [Page 58]
+\f
+Internet Draft 15 January 2007
+
+
+ [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
+ (IKE)", RFC 2409, November 1998.
+
+ [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
+ Authentication", RFC 2104, February 1997.
+
+ [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
+ Specifications, Version 2.0", RFC 2437, October 1998.
+
+ [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [SFTP] Ylonen T., and Lehtinen S., "Secure Shell File Transfer
+ Protocol", Internet Draft, March 2001.
+
+ [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 3629, November 2003.
+
+
+5 Author's Address
+
+ Pekka Riikonen
+ Helsinki
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+6 Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+Riikonen [Page 59]
+\f
--- /dev/null
+
+
+
+
+
+
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-silc-spec-09.txt 15 January 2007
+Expires: 15 July 2007
+
+
+ Secure Internet Live Conferencing (SILC),
+ Protocol Specification
+ <draft-riikonen-silc-spec-09.txt>
+
+Status of this Draft
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts. Internet-Drafts are draft documents valid for a maximum of
+ six months and may be updated, replaced, or obsoleted by other
+ documents at any time. It is inappropriate to use Internet-Drafts as
+ reference material or to cite them other than as "work in progress".
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/1id-abstracts.html
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+
+
+Abstract
+
+ This memo describes a Secure Internet Live Conferencing (SILC)
+ protocol which provides secure conferencing services over insecure
+ network channel. SILC provides advanced and feature rich conferencing
+ services with security as main design principal. Strong cryptographic
+ methods are used to protect SILC packets inside the SILC network.
+ Three other specifications relates very closely to this memo;
+ SILC Packet Protocol [SILC2], SILC Key Exchange and Authentication
+ Protocols [SILC3] and SILC Commands [SILC4].
+
+
+
+
+
+
+
+
+
+Riikonen [Page 1]
+\f
+Internet Draft 15 January 2007
+
+
+Table of Contents
+
+ 1 Introduction .................................................. 3
+ 1.1 Requirements Terminology .................................. 4
+ 2 SILC Concepts ................................................. 4
+ 2.1 SILC Network Topology ..................................... 5
+ 2.2 Communication Inside a Cell ............................... 6
+ 2.3 Communication in the Network .............................. 7
+ 2.4 Channel Communication ..................................... 7
+ 2.5 Router Connections ........................................ 8
+ 3 SILC Specification ............................................ 9
+ 3.1 Client .................................................... 9
+ 3.1.1 Client ID ........................................... 10
+ 3.2 Server .................................................... 11
+ 3.2.1 Server's Local ID List .............................. 11
+ 3.2.2 Server ID ........................................... 12
+ 3.2.3 SILC Server Ports ................................... 12
+ 3.3 Router .................................................... 13
+ 3.3.1 Router's Local ID List .............................. 13
+ 3.3.2 Router's Global ID List ............................. 14
+ 3.3.3 Router's Server ID .................................. 15
+ 3.4 Channels .................................................. 15
+ 3.4.1 Channel ID .......................................... 16
+ 3.5 Operators ................................................. 17
+ 3.6 SILC Commands ............................................. 17
+ 3.7 SILC Packets .............................................. 17
+ 3.8 Packet Encryption ......................................... 18
+ 3.8.1 Determination of the Source and the Destination ..... 18
+ 3.8.2 Client To Client .................................... 19
+ 3.8.3 Client To Channel ................................... 20
+ 3.8.4 Server To Server .................................... 21
+ 3.9 Key Exchange And Authentication ........................... 21
+ 3.9.1 Authentication Payload .............................. 22
+ 3.10 Algorithms ............................................... 24
+ 3.10.1 Ciphers ............................................ 24
+ 3.10.1.1 CBC Mode .................................. 24
+ 3.10.1.2 CTR Mode .................................. 25
+ 3.10.1.3 Randomized CBC Mode ....................... 27
+ 3.10.2 Public Key Algorithms .............................. 27
+ 3.10.2.1 Multi-Precision Integers .................. 28
+ 3.10.3 Hash Functions ..................................... 28
+ 3.10.4 MAC Algorithms ..................................... 28
+ 3.10.5 Compression Algorithms ............................. 29
+ 3.11 SILC Public Key .......................................... 29
+ 3.12 SILC Version Detection ................................... 32
+ 3.13 UTF-8 Strings in SILC .................................... 33
+ 3.13.1 UTF-8 Identifier Strings ........................... 33
+ 3.14 Backup Routers ........................................... 34
+
+
+
+Riikonen [Page 2]
+\f
+Internet Draft 15 January 2007
+
+
+ 3.14.1 Switching to Backup Router ......................... 36
+ 3.14.2 Resuming Primary Router ............................ 37
+ 4 SILC Procedures ............................................... 39
+ 4.1 Creating Client Connection ................................ 39
+ 4.2 Creating Server Connection ................................ 41
+ 4.2.1 Announcing Clients, Channels and Servers ............ 42
+ 4.3 Joining to a Channel ...................................... 43
+ 4.4 Channel Key Generation .................................... 44
+ 4.5 Private Message Sending and Reception ..................... 45
+ 4.6 Private Message Key Generation ............................ 46
+ 4.7 Channel Message Sending and Reception ..................... 47
+ 4.8 Session Key Regeneration .................................. 47
+ 4.9 Command Sending and Reception ............................. 48
+ 4.10 Closing Connection ....................................... 49
+ 4.11 Detaching and Resuming a Session ......................... 49
+ 4.12 UDP/IP Connections ...................................... 51
+ 5 Security Considerations ....................................... 52
+ 6 References .................................................... 53
+ 7 Author's Address .............................................. 55
+ Appendix A ...................................................... 55
+ Appendix B ...................................................... 56
+ Appendix C ...................................................... 57
+ Appendix D ...................................................... 57
+ Full Copyright Statement ........................................ 58
+
+List of Figures
+
+ Figure 1: SILC Network Topology
+ Figure 2: Communication Inside cell
+ Figure 3: Communication Between Cells
+ Figure 4: Router Connections
+ Figure 5: SILC Public Key
+ Figure 6: Counter Block
+ Figure 7: CTR Mode Initialization Vector
+
+
+1. Introduction
+
+ This document describes a Secure Internet Live Conferencing (SILC)
+ protocol which provides secure conferencing services over insecure
+ network channel. SILC can be used as a secure conferencing service
+ that provides rich conferencing features. Some of the SILC features
+ are found in traditional chat protocols such as IRC [IRC] but many
+ of the SILC features can also be found in Instant Message (IM) style
+ protocols. SILC combines features from both of these chat protocol
+ styles, and can be implemented as either IRC-like system or IM-like
+ system. Some of the more advanced and secure features of the
+ protocol are new to all conferencing protocols. SILC also supports
+
+
+
+Riikonen [Page 3]
+\f
+Internet Draft 15 January 2007
+
+
+ multimedia messages and can also be implemented as a video and audio
+ conferencing system.
+
+ Strong cryptographic methods are used to protect SILC packets inside
+ the SILC network. Three other specifications relates very closely
+ to this memo; SILC Packet Protocol [SILC2], SILC Key Exchange and
+ Authentication Protocols [SILC3] and SILC Commands [SILC4].
+
+ The protocol uses extensively packets as conferencing protocol
+ requires message and command sending. The SILC Packet Protocol is
+ described in [SILC2] and should be read to fully comprehend this
+ document and protocol. [SILC2] also describes the packet encryption
+ and decryption in detail. The SILC Packet Protocol provides secured
+ and authenticated packets, and the protocol is designed to be compact.
+ This makes SILC also suitable in environment of low bandwidth
+ requirements such as mobile networks. All packet payloads in SILC
+ can be also compressed.
+
+ The security of SILC protocol sessions are based on strong and secure
+ key exchange protocol. The SILC Key Exchange protocol is described
+ in [SILC3] along with connection authentication protocol and should
+ be read to fully comprehend this document and protocol.
+
+ The SILC protocol has been developed to work on both TCP/IP and UDP/IP
+ network protocols. However, typical implementation would use only TCP/IP
+ with SILC protocol. Typical implementation would be made in client-server
+ model.
+
+
+1.1 Requirements Terminology
+
+ The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL, when they appear in this document, are to be
+ interpreted as described in [RFC2119].
+
+
+2. SILC Concepts
+
+ This section describes various SILC protocol concepts that forms the
+ actual protocol, and in the end, the actual SILC network. The mission
+ of the protocol is to deliver messages from clients to other clients
+ through servers and routers in secure manner. The messages may also
+ be delivered from one client to many clients forming a group, also
+ known as a channel.
+
+ This section does not focus to security issues. Instead, basic network
+ concepts are introduced to make the topology of the SILC network
+ clear.
+
+
+
+Riikonen [Page 4]
+\f
+Internet Draft 15 January 2007
+
+
+2.1 SILC Network Topology
+
+ SILC network forms a ring as opposed to tree style network topology that
+ conferencing protocols usually have. The network has a cells which are
+ constructed from a router and zero or more servers. The servers are
+ connected to the router in a star like network topology. Routers in the
+ network are connected to each other forming a ring. The rationale for
+ this is to have servers that can perform specific kind of tasks what
+ other servers cannot perform. This leads to two kinds of servers; normal
+ SILC servers and SILC router servers.
+
+ A difference between normal server and router server is that routers
+ knows all global information and keep the global network state up to date.
+ They also do the actual routing of the messages to the correct receiver
+ within the cell and between other cells. Normal servers knows only local
+ information and receive global information only when it is needed. They do
+ not need to keep the global network state up to date. This makes the
+ network faster and scalable as there are less servers that needs to
+ maintain global network state.
+
+ This, on the other hand, leads into a cellular like network, where
+ routers are in the center of the cell and servers are connected to the
+ router.
+
+ The following diagram represents SILC network topology.
+
+ ---- ---- ---- ---- ---- ----
+ | S8 | S5 | S4 | | S7 | S5 | S6 |
+ ----- ---- ----- ----- ---- -----
+ | S7 | S/R1 | S2 | --- | S8 | S/R2 | S4 |
+ ---- ------ ---- ---- ------ ----
+ | S6 | S3 | S1 | | S1 | S3 | S2 | ---- ----
+ ---- ---- ---- ---- ---- ---- | S3 | S1 |
+ Cell 1. \ Cell 2. | \____ ----- -----
+ | | | S4 | S/R4 |
+ ---- ---- ---- ---- ---- ---- ---- ------
+ | S7 | S4 | S2 | | S1 | S3 | S2 | | S2 | S5 |
+ ----- ---- ----- ----- ---- ----- ---- ----
+ | S6 | S/R3 | S1 | --- | S4 | S/R5 | S5 | ____/ Cell 4.
+ ---- ------ ---- ---- ------ ----
+ | S8 | S5 | S3 | | S6 | S7 | S8 | ... etc ...
+ ---- ---- ---- ---- ---- ----
+ Cell 3. Cell 5.
+
+ Figure 1: SILC Network Topology
+
+
+ A cell is formed when a server or servers connect to one router. In
+
+
+
+Riikonen [Page 5]
+\f
+Internet Draft 15 January 2007
+
+
+ SILC network normal server cannot directly connect to other normal
+ server. Normal server may only connect to SILC router which then
+ routes the messages to the other servers in the cell. Router servers
+ on the other hand may connect to other routers to form the actual SILC
+ network, as seen in above figure. However, router is also able to act
+ as normal SILC server; clients may connect to it the same way as to
+ normal SILC server. This, however is not a requirement and if needed
+ router servers may be hidden from users by not allowing direct client
+ connections. Normal server also cannot have active connections to more
+ than one router. Normal server cannot be connected to two different
+ cells. Router servers, on the other hand, may have as many router to
+ router connections as needed. Other direct routes between other routers
+ is also possible in addition of the mandatory ring connections. This
+ leads into a hybrid ring-mesh network topology.
+
+ There are many issues in this network topology that needs to be careful
+ about. Issues like routing, the size of the cells, the number of the
+ routers in the SILC network and the capacity requirements of the
+ routers. These issues should be discussed in the Internet Community
+ and additional documents on the issue may be written.
+
+
+2.2 Communication Inside a Cell
+
+ It is always guaranteed that inside a cell message is delivered to the
+ recipient with at most two server hops. A client which is connected to
+ server in the cell and is talking on channel to other client connected
+ to other server in the same cell, will have its messages delivered from
+ its local server first to the router of the cell, and from the router
+ to the other server in the cell.
+
+ The following diagram represents this scenario:
+
+
+ 1 --- S1 S4 --- 5
+ S/R
+ 2 -- S2 S3
+ / |
+ 4 3
+
+
+ Figure 2: Communication Inside cell
+
+
+ Example: Client 1. connected to Server 1. send message to
+ Client 4. connected to Server 2. travels from Server 1.
+ first to Router which routes the message to Server 2.
+ which then sends it to the Client 4. All the other
+
+
+
+Riikonen [Page 6]
+\f
+Internet Draft 15 January 2007
+
+
+ servers in the cell will not see the routed message.
+
+
+ If the client is connected directly to the router, as router is also normal
+ SILC server, the messages inside the cell are always delivered only with
+ one server hop. If clients communicating with each other are connected
+ to the same server, no router interaction is needed. This is the optimal
+ situation of message delivery in the SILC network.
+
+
+2.3 Communication in the Network
+
+ If the message is destined to client that does not belong to local cell
+ the message is routed to the router server to which the destination
+ client belongs, if the local router is connected to destination router.
+ If there is no direct connection to the destination router, the local
+ router routes the message to its primary route. The following diagram
+ represents message sending between cells.
+
+
+
+ 1 --- S1 S4 --- 5 S2 --- 1
+ S/R - - - - - - - - S/R
+ 2 -- S2 S3 S1
+ / | \
+ 4 3 2
+
+ Cell 1. Cell 2.
+
+
+ Figure 3: Communication Between Cells
+
+
+ Example: Client 5. connected to Server 4. in Cell 1. sends message
+ to Client 2. connected to Server 1. in Cell 2. travels
+ from Server 4. to Router which routes the message to
+ Router in Cell 2, which then routes the message to
+ Server 1. All the other servers and routers in the
+ network will not see the routed message.
+
+
+ The optimal case of message delivery from the client point of view is
+ when clients are connected directly to the routers and the messages
+ are delivered from one router to the other.
+
+
+
+
+
+
+
+Riikonen [Page 7]
+\f
+Internet Draft 15 January 2007
+
+
+2.4 Channel Communication
+
+ Messages may be sent to group of clients as well. Sending messages to
+ many clients works the same way as sending messages point to point, from
+ message delivery point of view. Security issues are another matter
+ which are not discussed in this section.
+
+ Router server handles the message routing to multiple recipients. If
+ any recipient is not in the same cell as the sender the messages are
+ routed further.
+
+ Server distributes the channel message to its local clients which are
+ joined to the channel. Router also distributes the message to its
+ local clients on the channel.
+
+
+2.5 Router Connections
+
+ Router connections play very important role in making the SILC like
+ network topology to work. For example, sending broadcast packets in
+ SILC network require special connections between routers; routers must
+ be connected in a specific way.
+
+ Every router has their primary route which is a connection to another
+ router in the network. Unless there is only two routers in the network
+ must not routers use each other as their primary routes. The router
+ connections in the network must form a ring.
+
+ Example with three routers in the network:
+
+
+ S/R1 - < - < - < - < - < - < - S/R2
+ \ /
+ v ^
+ \ - > - > - S/R3 - > - > - /
+
+
+ Figure 4: Router Connections
+
+
+ Example: Network with three routers. Router 1. uses Router 2. as its
+ primary router. Router 2. uses Router 3. as its primary router,
+ and Router 3. uses Router 1. as its primary router. When there
+ are four or more routers in th enetwork, there may be other
+ direct connections between the routers but they must not be used
+ as primary routes.
+
+ The above example is applicable to any amount of routers in the network
+
+
+
+Riikonen [Page 8]
+\f
+Internet Draft 15 January 2007
+
+
+ except for two routers. If there are only two routers in the network both
+ routers must be able to handle situation where they use each other as their
+ primary routes.
+
+ The issue of router connections are very important especially with SILC
+ broadcast packets. Usually all router wide information in the network is
+ distributed by SILC broadcast packets. This sort of ring network, with
+ ability to have other direct routes in the network can cause interesting
+ routing problems. The [SILC2] discusses the routing of packets in this
+ sort of network in more detail.
+
+
+3. SILC Specification
+
+ This section describes the SILC protocol. However, [SILC2] and
+ [SILC3] describes other important protocols that are part of this SILC
+ specification and must be read.
+
+
+3.1 Client
+
+ A client is a piece of software connecting to SILC server. SILC client
+ cannot be SILC server. Purpose of clients is to provide the user
+ interface of the SILC services for end user. Clients are distinguished
+ from other clients by unique Client ID. Client ID is a 128 bit ID that
+ is used in the communication in the SILC network. The client ID is
+ based on the user's IP address and nickname. User use logical nicknames
+ in communication which are then mapped to the corresponding Client ID.
+ Client IDs are low level identifications and should not be seen by the
+ end user.
+
+ Clients provide other information about the end user as well. Information
+ such as the nickname of the user, username and the host name of the end
+ user and user's real name. See section 3.2 Server for information of
+ the requirements of keeping this information.
+
+ The nickname selected by the user is not unique in the SILC network.
+ There can be 2^8 same nicknames for one IP address. As for comparison to
+ IRC [IRC] where nicknames are unique this is a fundamental difference
+ between SILC and IRC. This typically causes the server names or client's
+ host names to be used along with the nicknames on user interface to
+ identify specific users when sending messages. This feature of SILC
+ makes IRC style nickname-wars obsolete as no one owns their nickname;
+ there can always be someone else with the same nickname. Also, any kind
+ of nickname registering service becomes obsolete. See the section 3.13.1
+ for more information about nicknames.
+
+
+
+
+
+Riikonen [Page 9]
+\f
+Internet Draft 15 January 2007
+
+
+3.1.1 Client ID
+
+ Client ID is used to identify users in the SILC network. The Client ID
+ is unique to the extent that there can be 2^128 different Client IDs,
+ and IDs based on IPv6 addresses extends this to 2^224 different Client
+ IDs. Collisions are not expected to happen. The Client ID is defined
+ as follows.
+
+ 128 bit Client ID based on IPv4 addresses:
+
+ 32 bit Server ID IP address (bits 1-32)
+ 8 bit Random number or counter
+ 88 bit Truncated MD5 hash value of the nickname
+
+ 224 bit Client ID based on IPv6 addresses:
+
+ 128 bit Server ID IP address (bits 1-128)
+ 8 bit Random number or counter
+ 88 bit Truncated MD5 hash value of the nickname
+
+ o Server ID IP address - Indicates the server where this
+ client is coming from. The IP address hence equals the
+ server IP address where the client is connected.
+
+ o Random number or counter - Random number to further
+ randomize the Client ID. Another choice is to use
+ a counter starting from the zero (0). This makes it
+ possible to have 2^8 same nicknames from the same
+ server IP address.
+
+ o MD5 hash - MD5 hash value of the case folded nickname is
+ truncated taking 88 bits from the start of the hash value.
+ This hash value is used to search the user's Client ID
+ from the ID lists. Note that the nickname MUST be prepared
+ using the stringprep [RFC3454] profile described in the
+ Appendix A before computing the MD5 hash. See also the
+ section 3.13.1 for more information.
+
+ Collisions could occur when more than 2^8 clients using same nickname
+ from the same server IP address is connected to the SILC network.
+ Server MUST be able to handle this situation by refusing to accept
+ anymore of that nickname.
+
+ Another possible collision may happen with the truncated hash value of
+ the nickname. It could be possible to have same truncated hash value
+ for two different nicknames. However, this is not expected to happen
+ nor cause any serious problems if it would occur. Nicknames are usually
+ logical and it is unlikely to have two distinct logical nicknames
+
+
+
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+\f
+Internet Draft 15 January 2007
+
+
+ produce same truncated hash value. Use of MD5 in nickname hash is not
+ a security feature.
+
+
+3.2 Server
+
+ Servers are the most important parts of the SILC network. They form the
+ basis of the SILC, providing a point to which clients may connect to.
+ There are two kinds of servers in SILC; normal servers and router servers.
+ This section focus on the normal server and router server is described
+ in the section 3.3 Router.
+
+ Normal servers MUST NOT directly connect to other normal server. Normal
+ servers may only directly connect to router server. If the message sent
+ by the client is destined outside the local server it is always sent to
+ the router server for further routing. Server may only have one active
+ connection to router on same port. Normal server MUST NOT connect to other
+ cell's router except in situations where its cell's router is unavailable.
+
+
+3.2.1 Server's Local ID List
+
+ Normal server keeps various information about the clients and their end
+ users connected to it. Every normal server MUST keep list of all locally
+ connected clients, Client IDs, nicknames, usernames and host names and
+ user's real name. Normal servers only keeps local information and it
+ does not keep any global information. Hence, normal servers knows only
+ about their locally connected clients. This makes servers efficient as
+ they do not have to worry about global clients. Server is also responsible
+ of creating the Client IDs for their clients.
+
+ Normal server also keeps information about locally created channels and
+ their Channel IDs.
+
+ Hence, local list for normal server includes:
+
+ server list - Router connection
+ o Server name
+ o Server IP address
+ o Server ID
+ o Sending key
+ o Receiving key
+ o Public key
+
+ client list - All clients in server
+ o Nickname
+ o Username@host
+ o Real name
+
+
+
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+Internet Draft 15 January 2007
+
+
+ o Client ID
+ o Sending key
+ o Receiving key
+ o Public key
+
+ channel list - All channels in server
+ o Channel name
+ o Channel ID
+ o Client IDs on channel
+ o Client ID modes on channel
+ o Channel key
+
+
+3.2.2 Server ID
+
+ Servers are distinguished from other servers by unique 64 bit Server ID
+ (for IPv4) or 160 bit Server ID (for IPv6). The Server ID is used in
+ the SILC to route messages to correct servers. Server IDs also provide
+ information for Client IDs, see section 3.1.1 Client ID. Server ID is
+ defined as follows.
+
+ 64 bit Server ID based on IPv4 addresses:
+
+ 32 bit IP address of the server
+ 16 bit Port
+ 16 bit Random number
+
+ 160 bit Server ID based on IPv6 addresses:
+
+ 128 bit IP address of the server
+ 16 bit Port
+ 16 bit Random number
+
+ o IP address of the server - This is the real IP address of
+ the server.
+
+ o Port - This is the port the server is bound to.
+
+ o Random number - This is used to further randomize the Server ID.
+
+ Collisions are not expected to happen in any conditions. The Server ID
+ is always created by the server itself and server is responsible of
+ distributing it to the router.
+
+
+3.2.3 SILC Server Ports
+
+ The following ports has been assigned by IANA for the SILC protocol:
+
+
+
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+
+
+ silc 706/tcp SILC
+ silc 706/udp SILC
+
+
+ If there are needs to create new SILC networks in the future the port
+ numbers must be officially assigned by the IANA.
+
+ Server on network above privileged ports (>1023) SHOULD NOT be trusted
+ as they could have been set up by untrusted party.
+
+
+3.3 Router
+
+ Router server in SILC network is responsible for keeping the cell together
+ and routing messages to other servers and to other routers. Router server
+ may also act as normal server when clients may connect to it. This is not
+ requirement and router servers may be hidden from clients.
+
+ However, router servers have a lot of important tasks that normal servers
+ do not have. Router server knows everything and keeps the global state.
+ They know all clients currently on SILC, all servers and routers and all
+ channels in SILC. Routers are the only servers in SILC that care about
+ global information and keeping them up to date at all time.
+
+
+3.3.1 Router's Local ID List
+
+ Router server as well MUST keep local list of connected clients and
+ locally created channels. However, this list is extended to include all
+ the informations of the entire cell, not just the server itself as for
+ normal servers.
+
+ However, on router this list is a lot smaller since routers do not need
+ to keep information about user's nickname, username and host name and real
+ name since these are not needed by the router. The router keeps only
+ information that it needs.
+
+ Hence, local list for router includes:
+
+ server list - All servers in the cell
+ o Server name
+ o Server ID
+ o Router's Server ID
+ o Sending key
+ o Receiving key
+
+ client list - All clients in the cell
+ o Client ID
+
+
+
+Riikonen [Page 13]
+\f
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+
+
+ channel list - All channels in the cell
+ o Channel ID
+ o Client IDs on channel
+ o Client ID modes on channel
+ o Channel key
+
+
+ Note that locally connected clients and other information include all the
+ same information as defined in section section 3.2.1 Server's Local ID
+ List. Router MAY also cache same detailed information for other clients
+ if needed.
+
+
+3.3.2 Router's Global ID List
+
+ Router server MUST also keep global list. Normal servers do not have
+ global list as they know only about local information. Global list
+ includes all the clients on SILC, their Client IDs, all created channels
+ and their Channel IDs and all servers and routers on SILC and their
+ Server IDs. That is said, global list is for global information and the
+ list must not include the local information already on the router's local
+ list.
+
+ Note that the global list does not include information like nicknames,
+ usernames and host names or user's real names. Router does not need to
+ keep these informations as they are not needed by the router. This
+ information is available from the client's server which maybe queried
+ when needed.
+
+ Hence, global list includes:
+
+ server list - All servers in SILC
+ o Server name
+ o Server ID
+ o Router's Server ID
+
+ client list - All clients in SILC
+ o Client ID
+
+ channel list - All channels in SILC
+ o Channel ID
+ o Client IDs on channel
+ o Client ID modes on channel
+
+
+
+
+
+
+
+
+Riikonen [Page 14]
+\f
+Internet Draft 15 January 2007
+
+
+3.3.3 Router's Server ID
+
+ Router's Server ID is equivalent to normal Server ID. As routers are
+ normal servers same types of IDs applies for routers as well. See
+ section 3.2.2 Server ID.
+
+
+
+
+3.4 Channels
+
+ A channel is a named group of one or more clients which will all receive
+ messages addressed to that channel. The channel is created when first
+ client requests JOIN command to the channel, and the channel ceases to
+ exist when the last client has left it. When channel exists, any client
+ can reference it using the Channel ID of the channel. If the channel has
+ a founder mode set and last client leaves the channel the channel does
+ not cease to exist. The founder mode can be used to make permanent
+ channels in the network. The founder of the channel can regain the
+ channel founder privileges on the channel later when he joins the
+ channel.
+
+ Channel names are unique although the real uniqueness comes from 64 bit
+ Channel ID. However, channel names are still unique and no two global
+ channels with same name may exist. See the section 3.13.1 for more
+ information about channel names.
+
+ Channels can have operators that can administrate the channel and operate
+ all of its modes. The following operators on channel exist on the
+ SILC network.
+
+ o Channel founder - When channel is created the joining client becomes
+ channel founder. Channel founder is channel operator with some more
+ privileges. Basically, channel founder can fully operate the channel
+ and all of its modes. The privileges are limited only to the
+ particular channel. There can be only one channel founder per
+ channel. Channel founder supersedes channel operator's privileges.
+
+ Channel founder privileges cannot be removed by any other operator on
+ channel. When channel founder leaves the channel there is no channel
+ founder on the channel. However, it is possible to set a mode for
+ the channel which allows the original channel founder to regain the
+ founder privileges even after leaving the channel. Channel founder
+ also cannot be removed by force from the channel.
+
+ o Channel operator - When client joins to channel that has not existed
+ previously it will become automatically channel operator (and channel
+ founder discussed above). Channel operator is able to administrate the
+
+
+
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+Internet Draft 15 January 2007
+
+
+ channel, set some modes on channel, remove a badly behaving client
+ from the channel and promote other clients to become channel
+ operator. The privileges are limited only to the particular channel.
+
+ Normal channel user may be promoted (opped) to channel operator
+ gaining channel operator privileges. Channel founder or other
+ channel operator may also demote (deop) channel operator to normal
+ channel user.
+
+
+
+
+3.4.1 Channel ID
+
+ Channels are distinguished from other channels by unique Channel ID.
+ The Channel ID is a 64 bit ID (for IPv4) or 160 bit ID (for IPv6), and
+ collisions are not expected to happen in any conditions. Channel names
+ are just for logical use of channels. The Channel ID is created by the
+ server where the channel is created. The Channel ID is defined as
+ follows.
+
+ 64 bit Channel ID based on IPv4 addresses:
+
+ 32 bit Router's Server ID IP address (bits 1-32)
+ 16 bit Router's Server ID port (bits 33-48)
+ 16 bit Random number or counter
+
+ 160 bit Channel ID based on IPv6 addresses:
+
+ 128 bit Router's Server ID IP address (bits 1-128)
+ 16 bit Router's Server ID port (bits 129-144)
+ 16 bit Random number or counter
+
+ o Router's Server ID IP address - Indicates the IP address of
+ the router of the cell where this channel is created. This is
+ taken from the router's Server ID. This way SILC routers know
+ where this channel resides in the SILC network.
+
+ o Router's Server ID port - Indicates the port of the channel on
+ the server. This is taken from the router's Server ID.
+
+ o Random number or counter - To further randomize the Channel ID.
+ Another choice is to use a counter starting from zero (0).
+ This makes sure that there are no collisions. This also means
+ that in a cell there can be 2^16 different channels.
+
+
+
+
+
+
+Riikonen [Page 16]
+\f
+Internet Draft 15 January 2007
+
+
+3.5 Operators
+
+ Operators are normal users with extra privileges to their server or
+ router. Usually these people are SILC server and router administrators
+ that take care of their own server and clients on them. The purpose of
+ operators is to administrate the SILC server or router. However, even
+ an operator with highest privileges is not able to enter invite-only
+ channels, to gain access to the contents of encrypted and authenticated
+ packets traveling in the SILC network or to gain channel operator
+ privileges on public channels without being promoted. They have the
+ same privileges as any normal user except they are able to administrate
+ their server or router.
+
+
+3.6 SILC Commands
+
+ Commands are very important part on SILC network especially for client
+ which uses commands to operate on the SILC network. Commands are used
+ to set nickname, join to channel, change modes and many other things.
+
+ Client usually sends the commands and server replies by sending a reply
+ packet to the command. Server MAY also send commands usually to serve
+ the original client's request. Usually server cannot send commands to
+ clients, however there MAY be commands that allow the server to send
+ commands to client. By default servers MAY send commands only to other
+ servers and routers.
+
+ Note that the command reply is usually sent only after client has sent
+ the command request but server is allowed to send command reply packet
+ to client even if client has not requested the command. Client MAY
+ choose to ignore the command reply.
+
+ It is expected that some of the commands may be misused by clients
+ resulting various problems on the server side. Every implementation
+ SHOULD assure that commands may not be executed more than once, say,
+ in two (2) seconds. However, to keep response rate up, allowing for
+ example five (5) commands before limiting is allowed. It is RECOMMENDED
+ that commands such as SILC_COMMAND_NICK, SILC_COMMAND_JOIN,
+ SILC_COMMAND_LEAVE and SILC_COMMAND_KILL SHOULD be limited in all cases
+ as they require heavy operations. This should be sufficient to prevent
+ the misuse of commands.
+
+ SILC commands are described in [SILC4].
+
+
+3.7 SILC Packets
+
+ Packets are naturally the most important part of the protocol and the
+
+
+
+Riikonen [Page 17]
+\f
+Internet Draft 15 January 2007
+
+
+ packets are what actually makes the protocol. Packets in SILC network
+ are always encrypted using, usually the shared secret session key
+ or some other key, for example, channel key, when encrypting channel
+ messages. It is not possible to send a packet in SILC network without
+ encryption. The SILC Packet Protocol is a wide protocol and is described
+ in [SILC2]. This document does not define or describe details of
+ SILC packets.
+
+
+3.8 Packet Encryption
+
+ All packets passed in SILC network MUST be encrypted. This section
+ gives generic description of how packets must be encrypted in the SILC
+ network. The detailed description of the actual encryption process
+ of the packets are described in [SILC2].
+
+ Client and its server shares secret symmetric session key which is
+ established by the SILC Key Exchange Protocol, described in [SILC3].
+ Every packet sent from client to server, with exception of packets for
+ channels, are encrypted with this session key.
+
+ Channels have a channel key that are shared by every client on the channel.
+ However, the channel keys are cell specific thus one cell does not know
+ the channel key of the other cell, even if that key is for same channel.
+ Channel key is also known by the routers and all servers that have clients
+ on the channel. However, channels MAY have channel private keys that are
+ entirely local setting for the client. All clients on the channel MUST
+ know the channel private key beforehand to be able to talk on the
+ channel. In this case, no server or router knows the key for the channel.
+
+ Server shares secret symmetric session key with router which is
+ established by the SILC Key Exchange Protocol. Every packet passed from
+ server to router, with exception of packets for channels, are encrypted
+ with the shared session key. Same way, router server shares secret
+ symmetric key with its primary router. However, every packet passed
+ from router to other router, including packets for channels, are
+ encrypted with the shared session key. Every router connection MUST
+ have their own session keys.
+
+
+3.8.1 Determination of the Source and the Destination
+
+ The source and the destination of the packet needs to be determined
+ to be able to route the packets to correct receiver. This information
+ is available in the SILC Packet Header which is included in all packets
+ sent in SILC network. The SILC Packet Header is described in [SILC2].
+
+ The header MUST be encrypted with the session key of who is the next
+
+
+
+Riikonen [Page 18]
+\f
+Internet Draft 15 January 2007
+
+
+ receiver of the packet along the route. The receiver of the packet, for
+ example a router along the route, is able to determine the sender and the
+ destination of the packet by decrypting the SILC Packet Header and
+ checking the IDs attached to the header. The IDs in the header will
+ tell to where the packet needs to be sent and where it is coming from.
+
+ The header in the packet MUST NOT change during the routing of the
+ packet. The original sender, for example client, assembles the packet
+ and the packet header and server or router between the sender and the
+ receiver MUST NOT change the packet header. Note however, that some
+ packets such as commands may be resent by a server to serve the client's
+ original command. In this case the command packet sent by the server
+ includes the server's IDs as it is a different packet. When server
+ or router receives a packet it MUST verify that the Source ID is
+ valid and correct ID for that sender.
+
+ Note that the packet and the packet header may be encrypted with
+ different keys. For example, packets to channels are encrypted with
+ the channel key, however, the header is encrypted with the session key
+ as described above. Most other packets have both header and packet
+ payload encrypted with the same key, such as command packets.
+
+
+3.8.2 Client To Client
+
+ The process of message delivery and encryption from client to another
+ client is as follows.
+
+ Example: Private message from client to another client on different
+ servers. Clients do not share private message delivery
+ keys; normal session keys are used.
+
+ o Client 1 sends encrypted packet to its server. The packet is
+ encrypted with the session key shared between client and its
+ server.
+
+ o Server determines the destination of the packet and decrypts
+ the packet. Server encrypts the packet with session key shared
+ between the server and its router, and sends the packet to the
+ router.
+
+ o Router determines the destination of the packet and decrypts
+ the packet. Router encrypts the packet with session key
+ shared between the router and the destination server, and sends
+ the packet to the server.
+
+ o Server determines the client to which the packet is destined
+ to and decrypts the packet. Server encrypts the packet with
+
+
+
+Riikonen [Page 19]
+\f
+Internet Draft 15 January 2007
+
+
+ session key shared between the server and the destination client,
+ and sends the packet to the client.
+
+ o Client 2 decrypts the packet.
+
+
+ Example: Private message from client to another client on different
+ servers. Clients have established a secret shared private
+ message delivery key with each other and that is used in
+ the message encryption.
+
+ o Client 1 sends encrypted packet to its server. The packet header
+ is encrypted with the session key shared between the client and
+ server, and the private message payload is encrypted with the
+ private message delivery key shared between clients.
+
+ o Server determines the destination of the packet and sends the
+ packet to the router. Header is encrypted with the session key.
+
+ o Router determines the destination of the packet and sends the
+ packet to the server. Header is encrypted with the session key.
+
+ o Server determines the client to which the packet is destined
+ to and sends the packet to the client. Header is encrypted with
+ the session key.
+
+ o Client 2 decrypts the packet with the secret shared key.
+
+ If clients share secret key with each other the private message
+ delivery is much simpler since servers and routers between the
+ clients do not need to decrypt and re-encrypt the entire packet.
+ The packet header however is always encrypted with session key and
+ is decrypted and re-encrypted with the session key of next recipient.
+
+ The process for clients on same server is much simpler as there is
+ no need to send the packet to the router. The process for clients
+ on different cells is same as above except that the packet is routed
+ outside the cell. The router of the destination cell routes the
+ packet to the destination same way as described above.
+
+
+3.8.3 Client To Channel
+
+ Process of message delivery from client on channel to all the clients
+ on the channel.
+
+ Example: Channel of four users; two on same server, other two on
+ different cells. Client sends message to the channel.
+
+
+
+Riikonen [Page 20]
+\f
+Internet Draft 15 January 2007
+
+
+ Packet header is encrypted with the session key, message
+ data is encrypted with channel key.
+
+ o Client 1 encrypts the packet with channel key and sends the
+ packet to its server.
+
+ o Server determines local clients on the channel and sends the
+ packet to the Client on the same server. Server then sends
+ the packet to its router for further routing.
+
+ o Router determines local clients on the channel, if found
+ sends packet to the local clients. Router determines global
+ clients on the channel and sends the packet to its primary
+ router or fastest route.
+
+ o (Other router(s) do the same thing and sends the packet to
+ the server(s).)
+
+ o Server determines local clients on the channel and sends the
+ packet to the client.
+
+ o All clients receiving the packet decrypts it.
+
+
+3.8.4 Server To Server
+
+ Server to server packet delivery and encryption is described in above
+ examples. Router to router packet delivery is analogous to server to
+ server. However, some packets, such as channel packets, are processed
+ differently. These cases are described later in this document and
+ more in detail in [SILC2].
+
+
+3.9 Key Exchange And Authentication
+
+ Key exchange is done always when for example client connects to server
+ but also when server and router, and router and another router connect
+ to each other. The purpose of key exchange protocol is to provide secure
+ key material to be used in the communication. The key material is used
+ to derive various security parameters used to secure SILC packets. The
+ SILC Key Exchange protocol is described in detail in [SILC3].
+
+ Authentication is done after key exchange protocol has been successfully
+ completed. The purpose of authentication is to authenticate for example
+ client connecting to the server. However, clients MAY be accepted
+ to connect to server without explicit authentication. Servers are
+ REQUIRED to use authentication protocol when connecting. The
+ authentication may be based on passphrase (pre-shared secret) or public
+
+
+
+Riikonen [Page 21]
+\f
+Internet Draft 15 January 2007
+
+
+ key based on digital signatures. All passphrases sent in SILC protocol
+ MUST be UTF-8 [RFC3629] encoded. The connection authentication protocol
+ is described in detail in [SILC3].
+
+
+3.9.1 Authentication Payload
+
+ Authentication Payload is used separately from the SKE and the Connection
+ Authentication protocols. It can be used during the session to
+ authenticate with a remote. For example, a client can authenticate
+ itself to a server to become server operator. In this case,
+ Authentication Payload is used.
+
+ The format of the Authentication Payload is as follows:
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Authentication Method |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Public Data Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Public Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Authentication Data Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Authentication Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 5: Authentication Payload
+
+
+ o Payload Length (2 bytes) - Length of the entire payload.
+
+ o Authentication Method (2 bytes) - The method of the
+ authentication. The authentication methods are defined
+ in [SILC2] in the Connection Auth Request Payload. The NONE
+ authentication method SHOULD NOT be used.
+
+ o Public Data Length (2 bytes) - Indicates the length of
+ the Public Data field.
+
+ o Public Data (variable length) - This is defined only if
+ the authentication method is public key. If it is any other
+
+
+
+Riikonen [Page 22]
+\f
+Internet Draft 15 January 2007
+
+
+ this field MAY include random data for padding purposes.
+ However, in this case the field MUST be ignored by the
+ receiver.
+
+ When the authentication method is public key this includes
+ 128 to 4096 bytes of non-zero random data that is used in
+ the signature process, described subsequently.
+
+ o Authentication Data Length (2 bytes) - Indicates the
+ length of the Authentication Data field. If zero (0)
+ value is found in this field the payload MUST be
+ discarded.
+
+ o Authentication Data (variable length) - Authentication
+ method dependent authentication data.
+
+
+ If the authentication method is passphrase-based, the Authentication
+ Data field includes the plaintext UTF-8 encoded passphrase. It is safe
+ to send plaintext passphrase since the entire payload is encrypted. In
+ this case the Public Data Length is set to zero (0), but MAY also include
+ random data for padding purposes. It is also RECOMMENDED that maximum
+ amount of padding is applied to SILC packet when using passphrase-based
+ authentication. This way it is not possible to approximate the length
+ of the passphrase from the encrypted packet.
+
+ If the authentication method is public key based (or certificate)
+ the Authentication Data is computed as follows:
+
+ HASH = hash(random bytes | ID | public key (or certificate));
+ Authentication Data = sign(HASH);
+
+ The hash() and the sign() are the hash function and the public key
+ cryptography function selected in the SKE protocol, unless otherwise
+ stated in the context where this payload is used. The public key
+ is SILC style public key unless certificates are used. The ID is the
+ entity's ID (Client or Server ID) which is authenticating itself. The
+ ID encoding is described in [SILC2]. The random bytes are non-zero
+ random bytes of length between 128 and 4096 bytes, and will be included
+ into the Public Data field as is.
+
+ The receiver will compute the signature using the random data received
+ in the payload, the ID associated to the connection and the public key
+ (or certificate) received in the SKE protocol. After computing the
+ receiver MUST verify the signature. Also in case of public key
+ authentication this payload is always encrypted. This payload is
+ always sent as part of some other payload.
+
+
+
+
+Riikonen [Page 23]
+\f
+Internet Draft 15 January 2007
+
+
+3.10 Algorithms
+
+ This section defines all the allowed algorithms that can be used in
+ the SILC protocol. This includes mandatory cipher, mandatory public
+ key algorithm and MAC algorithms.
+
+
+3.10.1 Ciphers
+
+ Cipher is the encryption algorithm that is used to protect the data
+ in the SILC packets. See [SILC2] for the actual encryption process and
+ definition of how it must be done. SILC has a mandatory algorithm that
+ must be supported in order to be compliant with this protocol.
+
+ The following ciphers are defined in SILC protocol:
+
+ aes-256-cbc AES in CBC mode, 256 bit key (REQUIRED)
+ aes-256-ctr AES in CTR mode, 256 bit key (RECOMMENDED)
+ aes-256-rcbc AES in randomized CBC mode, 256 bit key (OPTIONAL)
+ aes-192-<mode> AES in <mode> mode, 192 bit key (OPTIONAL)
+ aes-128-<mode> AES in <mode> mode, 128 bit key (RECOMMENDED)
+ twofish-256-<mode> Twofish in <mode> mode, 256 bit key (OPTIONAL)
+ twofish-192-<mode> Twofish in <mode> mode, 192 bit key (OPTIONAL)
+ twofish-128-<mode> Twofish in <mode> mode, 128 bit key (OPTIONAL)
+ cast-256-<mode> CAST-256 in <mode> mode, 256 bit key (OPTIONAL)
+ cast-192-<mode> CAST-256 in <mode> mode, 192 bit key (OPTIONAL)
+ cast-128-<mode> CAST-256 in <mode> mode, 128 bit key (OPTIONAL)
+ serpent-<len>-<mode> Serpent in <mode> mode, <len> bit key (OPTIONAL)
+ rc6-<len>-<mode> RC6 in <mode> mode, <len> bit key (OPTIONAL)
+ mars-<len>-<mode> MARS in <mode> mode, <len> bit key (OPTIONAL)
+ none No encryption (OPTIONAL)
+
+ The <mode> is either "cbc", "ctr" or "rcbc". Other encryption modes MAY
+ be defined to be used in SILC using the same name format. The <len> is
+ either 256, 192 or 128 bit key length. Also, additional ciphers MAY be
+ defined to be used in SILC by using the same name format as above.
+
+ Algorithm "none" does not perform any encryption process at all and
+ thus is not recommended to be used. It is recommended that no client
+ or server implementation would accept "none" algorithm except in special
+ debugging mode.
+
+
+3.10.1.1 CBC Mode
+
+ The "cbc" encryption mode is the standard cipher-block chaining mode.
+ The very first IV is derived from the SILC Key Exchange protocol.
+ Subsequent IVs for encryption is the previous ciphertext block. The very
+
+
+
+Riikonen [Page 24]
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+
+
+ first IV MUST be random and is generated as described in [SILC3].
+
+
+3.10.1.2 CTR Mode
+
+ The "ctr" encryption mode is Counter Mode (CTR). The CTR mode in SILC is
+ stateful in encryption and decryption. Both sender and receiver maintain
+ the counter for the CTR mode and thus can precompute the key stream for
+ encryption and decryption. By default, CTR mode does not require
+ plaintext padding, however implementations MAY apply padding to the
+ packets. If the last key block is larger than the last plaintext block
+ the resulted value is truncated to the size of the plaintext block and
+ the most significant bits are used. When sending authentication data
+ inside packets the maximum amount of padding SHOULD be applied with
+ CTR mode as well.
+
+ In CTR mode only the encryption operation of the cipher is used. The
+ decryption operation is not needed since both encryption and decryption
+ process is simple XOR with the plaintext block and the key stream block.
+
+ The counter block is used to create the key for the CTR mode. The format
+ of the 128 bit counter block is as follows:
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Truncated HASH from SKE |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Sending/Receiving IV from SKE |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packet Counter |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Block Counter |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 6: Counter Block
+
+ o Truncated HASH from SKE (4 bytes) - This value is the first 4
+ bytes from the HASH value that was computed as a result of SKE
+ protocol. This acts as session identifier and each rekey MUST
+ produce a new HASH value.
+
+ o Sending/Receiving IV from SKE (4 bytes) - If the CTR mode is fully
+ stateful this field MUST include the first 4 bytes from the Sending
+ IV or Receiving IV generated in SKE protocol. When this mode is
+ used to encrypt sending traffic the Sending IV is used, when used
+ to decrypt receiving traffic the Receiving IV is used. This assures
+ that two parties of the protocol use different IV for sending
+
+
+
+Riikonen [Page 25]
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+Internet Draft 15 January 2007
+
+
+ traffic. Each rekey MUST produce a new value.
+
+ If the IV Included flag is negotiated in SKE or CTR mode is used
+ where the IV is included in the data payload, this field is the
+ Nonce field from the IV received in the packet, defined below.
+
+ o Packet Counter (4 bytes) - This is MSB first ordered monotonically
+ increasing packet counter. It is set value 1 for first packet and
+ increases for subsequent packets. After rekey the counter MUST
+ restart from 1.
+
+ If the IV Included flag is negotiated in SKE or CTR mode is used
+ where the IV is included in the data payload, this field is the
+ Packet Counter field from the IV received in the packet, defined
+ below.
+
+ o Block Counter (4 bytes) - This is an MSB first ordered block
+ counter starting from 1 for first block and increasing for
+ subsequent blocks. The counter is always set to value 1 for
+ a new packet.
+
+ CTR mode MUST NOT be used with "none" MAC. Implementations also MUST
+ assure that the same counter block is not used to encrypt more than
+ one block. None of the counters must be allowed to wrap without rekey.
+ Also, the key material used with CTR mode MUST be fresh key material.
+ Static keys (pre-shared keys) MUST NOT be used with CTR mode. For this
+ reason using CTR mode to encrypt for example channel messages or private
+ messages with a pre-shared key is inappropriate. For private messages,
+ the Key Agreement [SILC2] could be performed to produce fresh key material.
+
+ If the IV Included flag was negotiated in SKE, or CTR mode is used to
+ protect channel messages where the IV will be included in the Message
+ Payload, the Initialization Vector (IV) to be used is a 64-bit block
+ containing randomness and packet counter. Also note, that in this case
+ the decryption process is not stateful and receiver cannot precompute
+ the key stream. Hence, the Initialization Vector (IV) when CTR mode is
+ used is as follows.
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Nonce |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Packet Counter |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 7: CTR Mode Initialization Vector
+
+
+
+
+Riikonen [Page 26]
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+Internet Draft 15 January 2007
+
+
+ o Nonce (4 bytes) - This field should be random or otherwise not
+ easily determinable and SHOULD change for each packet.
+
+ o Packet Counter (4 bytes) - This is MSB first ordered monotonically
+ increasing packet counter. It is set value 1 for first packet and
+ increases for subsequent packets. After rekey the counter MUST
+ restart from 1.
+
+ When decrypting the packet the Counter Block is assembled by concatenating
+ the truncated hash, with the received nonce and packet counter, and with
+ the block counter. The Counter Block is then used to compute the key
+ stream to perform the decryption.
+
+
+3.10.1.3 Randomized CBC Mode
+
+ The "rcbc" encryption mode is CBC mode with randomized IV. This means
+ that each IV for each packet MUST be chosen randomly. When encrypting
+ more than one block the normal IV chaining is used, but for the first
+ block new random IV is selected in each packet. In this mode the IV
+ is appended to the ciphertext. If this mode is used to secure the SILC
+ session, the IV Included flag must be negotiated in SILC Key Exchange
+ protocol. It may also be used to secure Message Payloads which can
+ deliver the IV to the recipient.
+
+
+3.10.2 Public Key Algorithms
+
+ Public keys are used in SILC to authenticate entities in SILC network
+ and to perform other tasks related to public key cryptography. The
+ public keys are also used in the SILC Key Exchange protocol [SILC3].
+
+ The following public key algorithms are defined in SILC protocol:
+
+ rsa RSA (REQUIRED)
+ dss DSS (OPTIONAL)
+
+ DSS is described in [Menezes]. The RSA MUST be implemented according
+ PKCS #1 [PKCS1]. When using SILC Public Key version 2 the PKCS #1
+ implementation MUST be compliant with PKCS #1 version 1.5. The signatures
+ are computed with appendix; the hash OID is included in the signature.
+ The user may always select the hash algorithm for the signatures. When
+ using SILC Public Key version 1 the PKCS #1 implementation MUST be
+ compliant with PKCS #1 version 1.5 where signatures are computed without
+ appendix; the hash OID is not present in the signature. The hash
+ algorithm used is specified separately or the default hash algorithm is
+ used, as defined below.
+
+
+
+
+Riikonen [Page 27]
+\f
+Internet Draft 15 January 2007
+
+
+ Additional public key algorithms MAY be defined to be used in SILC.
+
+ When signatures are computed in SILC the computing of the signature is
+ denoted as sign(). The signature computing procedure is dependent of
+ the public key algorithm, and the public key or certificate encoding.
+ When using SILC public key the signature is computed as described in
+ previous paragraph for RSA and DSS keys. If the hash function is not
+ specified separately for signing process SHA-1 MUST be used, except with
+ SILC public key version 2 and RSA algorithm when the user MAY always
+ select the hash algorithm. In this case the hash algorithm is included
+ in the signature and can be retrieved during verification. When using
+ SSH2 public keys the signature is computed as described in [SSH-TRANS].
+ When using X.509 version 3 certificates the signature is computed as
+ described in [PKCS7]. When using OpenPGP certificates the signature is
+ computed as described in [PGP] and the PGP signature type used is 0x00.
+
+
+3.10.2.1 Multi-Precision Integers
+
+ Multi-Precision (MP) integers in SILC are encoded and decoded as defined
+ in PKCS #1 [PKCS1]. MP integers are unsigned, encoded with the exact
+ octet length of the integer. No extra leading zero octets may appear.
+ The actual length of the integer is the bit size of the integer not
+ counting any leading zero bits. The octet length is derived by calculating
+ (bit_length + 7) / 8.
+
+
+3.10.3 Hash Functions
+
+ Hash functions are used as part of MAC algorithms defined in the next
+ section. They are also used in the SILC Key Exchange protocol defined
+ in the [SILC3].
+
+ The following Hash algorithm are defined in SILC protocol:
+
+ sha1 SHA-1, length = 20 bytes (REQUIRED)
+ sha256 SHA-256, length = 32 bytes (RECOMMENDED)
+ md5 MD5, length = 16 bytes (RECOMMENDED)
+
+
+3.10.4 MAC Algorithms
+
+ Data integrity is protected by computing a message authentication code
+ (MAC) of the packet data. See [SILC2] for details how to compute the
+ MAC for a packet.
+
+ The following MAC algorithms are defined in SILC protocol:
+
+
+
+
+Riikonen [Page 28]
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+
+
+ hmac-sha1-96 HMAC-SHA1, length = 12 bytes (REQUIRED)
+ hmac-sha256-96 HMAC-SHA256, length = 12 bytes (RECOMMENDED)
+ hmac-md5-96 HMAC-MD5, length = 12 bytes (OPTIONAL)
+ hmac-sha1 HMAC-SHA1, length = 20 bytes (OPTIONAL)
+ hmac-sha256 HMAC-SHA256, length = 32 bytes (OPTIONAL)
+ hmac-md5 HMAC-MD5, length = 16 bytes (OPTIONAL)
+ none No MAC (OPTIONAL)
+
+ The "none" MAC is not recommended to be used as the packet is not
+ authenticated when MAC is not computed. It is recommended that no
+ client or server would accept none MAC except in special debugging
+ mode.
+
+ The HMAC algorithm is described in [HMAC]. The hash algorithms used
+ in HMACs, the SHA-1 is described in [RFC3174] and MD5 is described
+ in [RFC1321]. The SHA-256 algorithm and its used with HMAC is described
+ in [SHA256].
+
+ Additional MAC algorithms MAY be defined to be used in SILC.
+
+
+3.10.5 Compression Algorithms
+
+ SILC protocol supports compression that may be applied to unencrypted
+ data. It is recommended to use compression on slow links as it may
+ significantly speed up the data transmission. By default, SILC does not
+ use compression which is the mode that must be supported by all SILC
+ implementations.
+
+ The following compression algorithms are defined:
+
+ none No compression (REQUIRED)
+ zlib GNU ZLIB (LZ77) compression (OPTIONAL)
+
+ Additional compression algorithms MAY be defined to be used in SILC.
+
+
+3.11 SILC Public Key
+
+ This section defines the type and format of the SILC public key. All
+ implementations MUST support this public key type. See [SILC3] for
+ other optional public key and certificate types allowed in the SILC
+ protocol. Public keys in SILC may be used to authenticate entities
+ and to perform other tasks related to public key cryptography.
+
+ The format of the SILC Public Key is as follows:
+
+
+
+
+
+Riikonen [Page 29]
+\f
+Internet Draft 15 January 2007
+
+
+ 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Public Key Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Algorithm Name Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Algorithm Name ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Identifier Length | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+ | |
+ ~ Identifier ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ ~ Public Data ~
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 5: SILC Public Key
+
+
+ o Public Key Length (4 bytes) - Indicates the full length
+ of the SILC Public Key, not including this field.
+
+ o Algorithm Name Length (2 bytes) - Indicates the length
+ of the Algorithm Length field, not including this field.
+
+ o Algorithm name (variable length) - Indicates the name
+ of the public key algorithm that the key is. See the
+ section 3.10.2 Public Key Algorithms for defined names.
+
+ o Identifier Length (2 bytes) - Indicates the length of
+ the Identifier field, not including this field.
+
+ o Identifier (variable length) - Indicates the identifier
+ of the public key. This data can be used to identify the
+ owner of the key. The identifier may be of the following
+ format:
+
+ UN User name
+ HN Host name or IP address
+ RN Real name
+ E EMail address
+ O Organization
+
+
+
+Riikonen [Page 30]
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+
+
+ C Country
+ V Version
+
+ Examples of an identifier:
+
+ `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi'
+
+ `UN=sam, HN=dummy.fi, RN=Sammy Sam, C=Finland, V=2'
+
+ At least user name (UN) and host name (HN) MUST be provided as
+ identifier. The fields are separated by commas (`,'). If
+ comma is in the identifier string it must be escaped as `\,',
+ for example, `O=Company XYZ\, Inc.'. Other characters that
+ require escaping are listed in [RFC2253] and are to be escaped
+ as defined therein. The Version (V) may only be a decimal digit.
+
+ o Public Data (variable length) - Includes the actual
+ public data of the public key.
+
+ The format of this field for RSA algorithm is
+ as follows:
+
+ 4 bytes Length of e
+ variable length e
+ 4 bytes Length of n
+ variable length n
+
+
+ The format of this field for DSS algorithm is
+ as follows:
+
+ 4 bytes Length of p
+ variable length p
+ 4 bytes Length of q
+ variable length q
+ 4 bytes Length of g
+ variable length g
+ 4 bytes Length of y
+ variable length y
+
+ The variable length fields are multiple precession
+ integers encoded as strings in both examples.
+
+ Other algorithms must define their own type of this
+ field if they are used.
+
+ The SILC Public Key is version is 2. If the Version (V) identifier is
+ not present the SILC Public Key version is expected to be 1. All new
+
+
+
+Riikonen [Page 31]
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+
+
+ implementations SHOULD support version 1 but SHOULD only generate version 2.
+ In this case the Version (V) identifier MUST be present.
+
+ All fields in the public key are in MSB (most significant byte first)
+ order. All strings in the public key MUST be UTF-8 encoded.
+
+ If an external protocol needs to refer to SILC Public Key by name, the
+ names "silc-rsa" and "silc-dss" for SILC Public Key based on RSA algorithm
+ and SILC Public Key based on DSS algorithm, respectively, are to be used.
+ However, this SILC specification does not use these names directly, and
+ they are defined here for external protocols (protocols that may like
+ to use SILC Public Key).
+
+ A fingerprint from SILC Public Key is computed from the whole encoded
+ public key data block. All fields are included in computation. Compliant
+ implementations MUST support computing a 160-bit SHA-1 fingerprint.
+
+
+3.12 SILC Version Detection
+
+ The version detection of both client and server is performed at the
+ connection phase while executing the SILC Key Exchange protocol. The
+ version identifier is exchanged between initiator and responder. The
+ version identifier is of the following format:
+
+ SILC-<protocol version>-<software version>
+
+ The version strings are of the following format:
+
+ protocol version = <major>.<minor>
+ software version = <major>[.<minor>[.<build or vendor string>]]
+
+ Protocol version MUST provide both major and minor version. Currently
+ implementations MUST set the protocol version and accept at least the
+ protocol version as SILC-1.2-<software version>. If new protocol version
+ causes incompatibilities with older version the <minor> version number
+ MUST be incremented. The <major> is incremented if new protocol version
+ is fully incompatible.
+
+ Software version MAY provide major, minor and build (vendor) version.
+ The software version MAY be freely set and accepted. The version string
+ MUST consist of printable US-ASCII characters.
+
+ Thus, the version strings could be, for example:
+
+ SILC-1.1-2.0.2
+ SILC-1.0-1.2
+ SILC-1.2-1.0.VendorXYZ
+
+
+
+Riikonen [Page 32]
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+
+
+ SILC-1.2-2.4.5 Vendor Limited
+
+
+3.13 UTF-8 Strings in SILC
+
+ By default all strings that are sent in SILC protocol MUST be UTF-8
+ [RFC3269] encoded, unless otherwise defined. This means that any string
+ sent inside for example, command, command reply, notify or any packet
+ payload is UTF-8 encoded. Also nicknames, channel names, server names,
+ and hostnames are UTF-8 encoded. This definition does not affect
+ messages sent in SILC, as the Message Payload provides its own mechanism
+ to indicate whether a message is UTF-8 text message, data message, which
+ may use its own character encoding, or pure binary message [SILC2].
+
+ Certain limitations are imposed on the UTF-8 encoded strings in SILC.
+ The UTF-8 encoded strings MUST NOT include any characters that are
+ marked in the Unicode standard as control codes, noncharacters,
+ reserved or private range characters, or any other illegal Unicode
+ characters. Also the BOM (Byte-Order Mark) MUST NOT be used as byte
+ order signature in UTF-8 encoded strings. A string containing these
+ characters MUST be treated as malformed UTF-8 encoding.
+
+ The Unicode standard defines that malformed sequences shall be signalled
+ by replacing the sequence with a replacement character. Even though,
+ in case of SILC these strings may not be malformed UTF-8 encodings
+ they MUST be treated as malformed strings. Implementation MAY use
+ a replacement character, however, the character Unicode standard defines
+ MUST NOT be used, but another character must be chosen. It is, however,
+ RECOMMENDED that an error is returned instead of using replacement
+ character if it is possible. For example, when setting a nickname
+ with SILC_COMMAND_NICK command, implementation is able to send error
+ indication back to the command sender. It must be noted that on server
+ implementation if a character sequence is merely outside of current
+ character subset, but is otherwise valid character, it MUST NOT be
+ replaced by a replacement character.
+
+ On user interface where UTF-8 strings are displayed the implementation
+ is RECOMMENDED to escape any character that it is unable to render
+ properly. The escaping may be done for example as described in
+ [RFC2253]. The escaping makes it possible to retrieve the original
+ UTF-8 encoding. Alternatively, a replacement character may be used
+ if it does not cause practical problems to the implementation.
+
+
+3.13.1 UTF-8 Identifier Strings
+
+ Identifier strings are special strings in SILC protocol that require
+ more careful processing, than the general UTF-8 strings described in the
+
+
+
+Riikonen [Page 33]
+\f
+Internet Draft 15 January 2007
+
+
+ previous section. These strings include the nicknames, server names,
+ hostnames and some other identifier strings. These strings are prepared
+ using the stringprep [RFC3454] standard. The Appendix A defines the
+ stringprep profile for SILC identifier strings and conforming
+ implementation MUST use the profile to prepare any identifier string.
+
+ The stringprep profile describes how identifier strings are prepared,
+ what characters they may include, and which characters are prohibited.
+ Identifier strings with prohibited characters MUST be treated as
+ malformed strings.
+
+ The channel name is also special identifier strings with some slight
+ differences to other identifier strings. The Appendix B defines the
+ stringprep profile for the channel name strings and conforming
+ implementation MUST use the profile to prepare any channel name string.
+
+ Because of the profile the identifier strings in SILC may generally
+ include only letters, numbers, most punctuation characters, and some
+ other characters. For practical reasons most symbol characters and
+ many other special characters are prohibited. All identifier strings
+ are case folded and comparing the identifier strings MUST be done as
+ caseless matching.
+
+ In general, the identifier strings does not have a maximum length.
+ However, the length of a nickname string MUST NOT exceed 128 bytes, and
+ the length of a channel name string MUST NOT exceed 256 bytes. Since
+ these strings are UTF-8 encoded the length of one character may be
+ longer than one byte. This means that the character length of these
+ strings may be shorter than the maximum length of the string in bytes.
+ The minimum length of an identifier string MUST be at least one character,
+ which may be one byte or more in length. Implementation MAY limit the
+ maximum length of an identifier string, with exception of the nickname
+ and channel name strings which has the explicit length definition.
+
+
+3.14 Backup Routers
+
+ Backup routers may exist in the cell in addition to the primary router.
+ However, they must not be active routers or act as routers in the cell.
+ Only one router may be acting as primary router in the cell. In the case
+ of failure of the primary router one of the backup routers becomes active.
+ The purpose of backup routers are in case of failure of the primary router
+ to maintain working connections inside the cell and outside the cell and
+ to avoid netsplits.
+
+ Backup routers are normal servers in the cell that are prepared to take
+ over the tasks of the primary router if needed. They need to have at
+ least one direct and active connection to the primary router of the cell.
+
+
+
+Riikonen [Page 34]
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+
+
+ This communication channel is used to send the router information to
+ the backup router. When the backup router connects to the primary router
+ of the cell it MUST present itself as router server in the Connection
+ Authentication protocol, even though it is normal server as long as the
+ primary router is available. Reason for this is that the configuration
+ needed in the responder end requires usually router connection level
+ configuration. The responder, however must understand and treat the
+ connection as normal server (except when feeding router level data to
+ the backup router).
+
+ Backup router must know everything that the primary router knows to be
+ able to take over the tasks of the primary router. It is the primary
+ router's responsibility to feed the data to the backup router. If the
+ backup router does not know all the data in the case of failure some
+ connections may be lost. The primary router of the cell must consider
+ the backup router being an actual router server when it feeds the data
+ to it.
+
+ In addition to having direct connection to the primary router of the
+ cell, the backup router must also have connection to the same router
+ to which the primary router of the cell is connected. However, it must
+ not be the active router connection meaning that the backup router must
+ not use that channel as its primary route and it must not notify the
+ router about having connected servers, channels and clients behind it.
+ It merely connects to the router. This sort of connection is later
+ referred to as being a passive connection. Some keepalive actions may
+ be needed by the router to keep the connection alive.
+
+ It is required that other normal servers have passive connections to
+ the backup router(s) in the cell. Some keepalive actions may be needed
+ by the server to keep the connection alive. After they notice the
+ failure of the primary router they must start using the connection to
+ the first backup router as their primary route.
+
+ Also, if any other router in the network is using the cell's primary
+ router as its own primary router, it must also have passive connection
+ to the cell's backup router. It too is prepared to switch to use the
+ backup router as its new primary router as soon as the original primary
+ router becomes unresponsive.
+
+ All of the parties of this protocol know which one is the backup router
+ of the cell from their local configuration. Each of the entities must
+ be configured accordingly and care must be taken when configuring the
+ backup routers, servers and other routers in the network.
+
+ It must be noted that some of the channel messages and private messages
+ may be lost during the switch to the backup router, unless the message
+ flag SILC_MESSAGE_FLAG_ACK is set in the message. The announcements
+
+
+
+Riikonen [Page 35]
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+
+
+ assure that the state of the network is not lost during the switch.
+
+ It is RECOMMENDED that there would be at least one backup router in
+ the cell. It is NOT RECOMMENDED to have all servers in the cell acting
+ as backup routers as it requires establishing several connections to
+ several servers in the cell. Large cells can easily have several
+ backup routers in the cell.
+
+ The order of the backup routers are decided at the local configuration
+ phase. All the parties of this protocol must be configured accordingly to
+ understand the order of the backup routers. It is not required that the
+ backup server is actually an active server in the cell. The backup router
+ may be a redundant server in the cell that does not accept normal client
+ connections at all. It may be reserved purely for the backup purposes.
+
+ If also the first backup router is down as well and there is another
+ backup router in the cell then it will start acting as the primary
+ router as described above.
+
+
+3.14.1 Switching to Backup Router
+
+ When the primary router of the cell becomes unresponsive, for example
+ by sending EOF to the connection, all the parties of this protocol MUST
+ replace the old connection to the primary router with first configured
+ backup router. The backup router usually needs to do local modifications
+ to its database in order to update all the information needed to maintain
+ working routes. The backup router must understand that clients that
+ were originated from the primary router are now originated from some of
+ the existing server connections and must update them accordingly. It
+ must also remove those clients that were owned by the primary router
+ since those connections were lost when the primary router became
+ unresponsive.
+
+ All the other parties of the protocol must also update their local
+ database to understand that the route to the primary router will now go
+ to the backup router.
+
+ Servers connected to the backup router MUST send SILC_PACKET_RESUME_ROUTER
+ packet with type value 21, to indicate that the server will start using
+ the backup router as primary router. The backup router MUST NOT allow
+ this action if it detects that primary is still up and running. If
+ backup router knows that primary is up and running it MUST send
+ SILC_PACKET_FAILURE with type value 21 (4 bytes, MSB first order) back
+ to the server. The server then MUST NOT use the backup as primary
+ router, but must try to establish connection back to the primary router.
+ If the action is allowed type value 21 is sent back to the server from
+ the backup router. It is RECOMMENDED that implementations use the
+
+
+
+Riikonen [Page 36]
+\f
+Internet Draft 15 January 2007
+
+
+ SILC_COMMAND_PING command to detect whether primary router is responsive.
+ If the backup router notices that the primary router is unresponsive
+ it SHOULD NOT start sending data to server links before the server has
+ sent the SILC_PACKET_RESUME_ROUTER with type value 21.
+
+ The servers connected to the backup router must then announce their
+ clients, channels, channel users, channel user modes, channel modes,
+ topics and other information to the backup router. This is to assure
+ that none of the important notify packets were lost during the switch
+ to the backup router. The backup router must check which of these
+ announced entities it already has and distribute the new ones to the
+ primary router.
+
+ The backup router too must announce its servers, clients, channels
+ and other information to the new primary router. The primary router
+ of the backup router too must announce its information to the backup
+ router. Both must process only the ones they do not know about. If
+ any of the announced modes do not match then they are enforced in
+ normal manner as defined in section 4.2.1 Announcing Clients, Channels
+ and Servers.
+
+
+3.14.2 Resuming Primary Router
+
+ Usually the primary router is unresponsive only a short period of time
+ and it is intended that the original router of the cell will resume
+ its position as primary router when it comes back online. The backup
+ router that is now acting as primary router of the cell must constantly
+ try to connect to the original primary router of the cell. It is
+ RECOMMENDED that it would try to reconnect in 30 second intervals to
+ the primary router.
+
+ When the connection is established to the primary router the backup
+ resuming protocol is executed. The protocol is advanced as follows:
+
+ 1. Backup router sends SILC_PACKET_RESUME_ROUTER packet with type
+ value 1 to the primary router that came back online. The packet
+ will indicate the primary router has been replaced by the backup
+ router. After sending the packet the backup router will announce
+ all of its channels, channel users, modes etc. to the primary
+ router.
+
+ If the primary knows that it has not been replaced (for example
+ the backup itself disconnected from the primary router and thinks
+ that it is now primary in the cell) the primary router send
+ SILC_PACKET_FAILURE with the type value 1 (4 bytes, MSB first
+ order) back to the backup router. If backup receives this it
+ MUST NOT continue with the backup resuming protocol.
+
+
+
+Riikonen [Page 37]
+\f
+Internet Draft 15 January 2007
+
+
+ 2. Backup router sends SILC_PACKET_RESUME_ROUTER packet with type
+ value 1 to its current primary router to indicate that it will
+ resign as being primary router. Then, backup router sends the
+ SILC_PACKET_RESUME_ROUTER packet with type value 1 to all
+ connected servers to also indicate that it will resign as being
+ primary router.
+
+ 3. Backup router also send SILC_PACKET_RESUME_ROUTER packet with
+ type value 1 to the router that is using the backup router
+ currently as its primary router.
+
+ 4. Any server and router that receives the SILC_PACKET_RESUME_ROUTER
+ with type value 1 must reconnect immediately to the primary
+ router of the cell that came back online. After they have created
+ the connection they MUST NOT use that connection as active primary
+ route but still route all packets to the backup router. After
+ the connection is created they MUST send SILC_PACKET_RESUME_ROUTER
+ with type value 2 back to the backup router. The session ID value
+ found in the first packet MUST be set in this packet.
+
+ 5. Backup router MUST wait for all packets with type value 2 before
+ it continues with the protocol. It knows from the session ID values
+ set in the packet when it has received all packets. The session
+ value should be different in all packets it has sent earlier.
+ After the packets are received the backup router sends the
+ SILC_PACKET_RESUME_ROUTER packet with type value 3 to the
+ primary router that came back online. This packet will indicate
+ that the backup router is now ready to resign as being primary
+ router. The session ID value in this packet MUST be the same as
+ in the first packet sent to the primary router. During this time
+ the backup router must still route all packets it is receiving
+ from server connections.
+
+ 6. The primary router receives the packet and send the packet
+ SILC_PACKET_RESUME_ROUTER with type value 4 to all connected servers
+ including the backup router. It also sends the packet with type
+ value 4 to its primary router, and to the router that is using
+ it as its primary router. The Session ID value in these packets
+ SHOULD be zero (0).
+
+ 7. Any server and router that receives the SILC_PACKET_RESUME_ROUTER
+ packet with type value 4 must switch their primary route to the new
+ primary router and remove the route for the backup router, since
+ it is no longer the primary router of the cell. They must also
+ update their local database to understand that the clients are
+ not originated from the backup router but from the locally connected
+ servers. After that they MUST announce their channels, channel
+ users, modes etc. to the primary router. They MUST NOT use the
+
+
+
+Riikonen [Page 38]
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+Internet Draft 15 January 2007
+
+
+ backup router connection after this and the connection is considered
+ to be a passive connection. The implementation SHOULD be able
+ to disable the connection without closing the actual link.
+
+ After this protocol is executed the backup router is now again a normal
+ server in the cell that has the backup link to the primary router. The
+ primary router feeds the router specific data again to the backup router.
+ All server connections to the backup router are considered passive
+ connections.
+
+ When the primary router of the cell comes back online and connects
+ to its remote primary router, the remote primary router MUST send the
+ SILC_PACKET_RESUME_ROUTER packet with type value 20 indicating that the
+ connection is not allowed since the router has been replaced by an
+ backup router in the cell. The session ID value in this packet SHOULD be
+ zero (0). When the primary router receives this packet it MUST NOT use
+ the connection as active connection but must understand that it cannot
+ act as primary router in the cell, until the backup resuming protocol has
+ been executed.
+
+ The following type values has been defined for SILC_PACKET_RESUME_ROUTER
+ packet:
+
+ 1 SILC_SERVER_BACKUP_START
+ 2 SILC_SERVER_BACKUP_START_CONNECTED
+ 3 SILC_SERVER_BACKUP_START_ENDING
+ 4 SILC_SERVER_BACKUP_START_RESUMED
+ 20 SILC_SERVER_BACKUP_START_REPLACED
+ 21 SILC_SERVER_BACKUP_START_USE
+
+ If any other value is found in the type field the packet MUST be
+ discarded. The SILC_PACKET_RESUME_ROUTER packet and its payload
+ is defined in [SILC2].
+
+
+4 SILC Procedures
+
+ This section describes various SILC procedures such as how the
+ connections are created and registered, how channels are created and
+ so on. The references [SILC2], [SILC3] and [SILC4] permeate this
+ section's definitions.
+
+
+4.1 Creating Client Connection
+
+ This section describes the procedure when a client connects to SILC
+ server. When client connects to server the server MUST perform IP
+ address lookup and reverse IP address lookup to assure that the origin
+
+
+
+Riikonen [Page 39]
+\f
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+
+
+ host really is who it claims to be. Client, a host, connecting to server
+ SHOULD have both valid IP address and fully qualified domain name (FQDN).
+
+ After that the client and server performs SILC Key Exchange protocol
+ which will provide the key material used later in the communication.
+ The key exchange protocol MUST be completed successfully before the
+ connection registration may continue. The SILC Key Exchange protocol
+ is described in [SILC3].
+
+ Typical server implementation would keep a list of connections that it
+ allows to connect to the server. The implementation would check, for
+ example, the connecting client's IP address from the connection list
+ before the SILC Key Exchange protocol has been started. The reason for
+ this is that if the host is not allowed to connect to the server there
+ is no reason to perform the key exchange protocol.
+
+ After successful key exchange protocol the client and server perform
+ connection authentication protocol. The purpose of the protocol is to
+ authenticate the client connecting to the server. Flexible
+ implementation could also accept the client to connect to the server
+ without explicit authentication. However, if authentication is
+ desired for a specific client it may be based on passphrase or
+ public key authentication. If authentication fails the connection
+ MUST be terminated. The connection authentication protocol is described
+ in [SILC3].
+
+ After successful key exchange and authentication protocol the client
+ MUST register itself by sending SILC_PACKET_NEW_CLIENT packet to the
+ server. This packet includes various information about the client
+ that the server uses to register the client. Server registers the
+ client and sends SILC_PACKET_NEW_ID to the client which includes the
+ created Client ID that the client MUST start using after that. After
+ that all SILC packets from the client MUST have the Client ID as the
+ Source ID in the SILC Packet Header, described in [SILC2].
+
+ Client MUST also get the server's Server ID that is to be used as
+ Destination ID in the SILC Packet Header when communicating with
+ the server (for example when sending commands to the server). The
+ ID may be resolved in two ways. Client can take the ID from an
+ previously received packet from server that MUST include the ID,
+ or to send SILC_COMMAND_INFO command and receive the Server ID as
+ command reply.
+
+ Server MAY choose not to use the information received in the
+ SILC_PACKET_NEW_CLIENT packet. For example, if public key or
+ certificate were used in the authentication, server MAY use that
+ information rather than what it received from client. This is a suitable
+ way to get the true information about client if it is available.
+
+
+
+Riikonen [Page 40]
+\f
+Internet Draft 15 January 2007
+
+
+ The nickname of client is initially set to the username sent in the
+ SILC_PACKET_NEW_CLIENT packet. User may set the nickname to something
+ more desirable by sending SILC_COMMAND_NICK command. However, this is
+ not required as part of registration process.
+
+ Server MUST also distribute the information about newly registered
+ client to its router (or if the server is router, to all routers in
+ the SILC network). More information about this in [SILC2].
+
+ Router server MUST also check whether some client in the local cell
+ is watching for the nickname this new client has, and send the
+ SILC_NOTIFY_TYPE_WATCH to the watcher.
+
+
+4.2 Creating Server Connection
+
+ This section describes the procedure when server connects to its
+ router (or when router connects to other router, the cases are
+ equivalent). The procedure is very much alike to when a client
+ connects to the server thus it is not repeated here.
+
+ One difference is that server MUST perform connection authentication
+ protocol with proper authentication. A proper authentication is based
+ on passphrase authentication or public key authentication based on
+ digital signatures.
+
+ After server and router have successfully performed the key exchange
+ and connection authentication protocol, the server MUST register itself
+ to the router by sending SILC_PACKET_NEW_SERVER packet. This packet
+ includes the server's Server ID that it has created by itself and
+ other relevant information about the server. The router receiving the
+ ID MUST verify that the IP address in the Server ID is same as the
+ server's real IP address.
+
+ After router has received the SILC_PACKET_NEW_SERVER packet it
+ distributes the information about newly registered server to all routers
+ in the SILC network. More information about this is in [SILC2].
+
+ As the client needed to resolve the destination ID this MUST be done by
+ the server that connected to the router, as well. The way to resolve it
+ is to get the ID from previously received packet. The server MAY also
+ use SILC_COMMAND_INFO command to resolve the ID. Server MUST also start
+ using its own Server ID as Source ID in SILC Packet Header and the
+ router's Server ID as Destination when communicating with the router.
+
+
+
+
+
+
+
+Riikonen [Page 41]
+\f
+Internet Draft 15 January 2007
+
+
+4.2.1 Announcing Clients, Channels and Servers
+
+ After server or router has connected to the remote router, and it already
+ has connected clients and channels it MUST announce them to the router.
+ If the server is router server, also all the local servers in the cell
+ MUST be announced.
+
+ All clients are announced by compiling a list of ID Payloads into the
+ SILC_PACKET_NEW_ID packet. All channels are announced by compiling a
+ list of Channel Payloads into the SILC_PACKET_NEW_CHANNEL packet.
+ Channels' mode, founder public key, channel public keys, and other
+ channel mode specific data is announced by sending the
+ SILC_NOTIFY_TYPE_CMODE_CHANGE notify list.
+
+ The channel public keys that are announced are compiled in Argument
+ List Payload where the argument type is 0x03, and each argument is
+ Public Key Payload containing one public key or certificate.
+
+ Also, the channel users on the channels must be announced by compiling
+ a list of Notify Payloads with the SILC_NOTIFY_TYPE_JOIN notify type
+ into the SILC_PACKET_NOTIFY packet. The users' modes on the channel
+ must also be announced by compiling list of Notify Payloads with the
+ SILC_NOTIFY_TYPE_CUMODE_CHANGE notify type into the SILC_PACKET_NOTIFY
+ packet.
+
+ The router MUST also announce the local servers by compiling list of
+ ID Payloads into the SILC_PACKET_NEW_ID packet.
+
+ Also, clients' modes (user modes in SILC) MUST be announced. This is
+ done by compiling a list of Notify Payloads with SILC_NOTIFY_UMODE_CHANGE
+ notify type into the SILC_PACKET_NOTIFY packet. Also, channels' topics
+ MUST be announced by compiling a list of Notify Payloads with the
+ SILC_NOTIFY_TOPIC_SET notify type into the SILC_PACKET_NOTIFY packet.
+ Also, channel's invite and ban lists MUST be announced by compiling list
+ of Notify Payloads with the SILC_NOTIFY_TYPE_INVITE and
+ SILC_NOTIFY_TYPE_BAN notify types, respectively, into the
+ SILC_PACKET_NOTIFY packet.
+
+ The router which receives these lists MUST process them and broadcast
+ the packets to its primary router. When processing the announced channels
+ and channel users the router MUST check whether a channel exists already
+ with the same name. If channel exists with the same name it MUST check
+ whether the Channel ID is different. If the Channel ID is different the
+ router MUST send the notify type SILC_NOTIFY_TYPE_CHANNEL_CHANGE to the
+ server to force the channel ID change to the ID the router has. If the
+ mode of the channel is different the router MUST send the notify type
+ SILC_NOTIFY_TYPE_CMODE_CHANGE to the server to force the mode change
+ to the mode that the router has.
+
+
+
+Riikonen [Page 42]
+\f
+Internet Draft 15 January 2007
+
+
+ The router MUST also generate new channel key and distribute it to the
+ channel. The key MUST NOT be generated if the SILC_CMODE_PRIVKEY mode
+ is set.
+
+ If the channel has a channel founder already on the router, the router
+ MUST send the notify type SILC_NOTIFY_TYPE_CUMODE_CHANGE to the server
+ to force the mode change for the channel founder on the server. The
+ channel founder privileges MUST be removed on the server.
+
+ If the channel public keys are already set on the on router, the router
+ MUST ignore the received channel public key list and send the notify
+ type SILC_NOTIFY_TYPE_CUMODE_CHANGE to the server which includes the
+ channel public key list that is on router. The server MUST change the
+ list to the one it receives from router.
+
+ The router processing the channels MUST also compile a list of
+ Notify Payloads with the SILC_NOTIFY_TYPE_JOIN notify type into the
+ SILC_PACKET_NOTIFY and send the packet to the server. This way the
+ server (or router) will receive the clients on the channel that
+ the router has.
+
+
+4.3 Joining to a Channel
+
+ This section describes the procedure when client joins to a channel.
+ Client joins to channel by sending command SILC_COMMAND_JOIN to the
+ server. If the receiver receiving join command is normal server the
+ server MUST check its local list whether this channel already exists
+ locally. This would indicate that some client connected to the server
+ has already joined to the channel. If this is the case, the client is
+ joined to the channel, new channel key is created and information about
+ newly joined channel is sent to the router. The router is informed
+ by sending SILC_NOTIFY_TYPE_JOIN notify type. The notify type MUST
+ also be sent to the local clients on the channel. The new channel key
+ is also sent to the router and to local clients on the channel.
+
+ If the channel does not exist in the local list the client's command
+ MUST be sent to the router which will then perform the actual joining
+ procedure. When server receives the reply to the command from the
+ router it MUST be sent to the client which sent the command originally.
+ Server will also receive the channel key from the server that it MUST
+ send to the client which originally requested the join command. The
+ server MUST also save the channel key.
+
+ If the receiver of the join command is router it MUST first check its
+ local list whether anyone in the cell has already joined to the channel.
+ If this is the case, the client is joined to the channel and reply is
+ sent to the client. If the command was sent by server the command reply
+
+
+
+Riikonen [Page 43]
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+Internet Draft 15 January 2007
+
+
+ is sent to the server which sent it. Then the router MUST also create
+ new channel key and distribute it to all clients on the channel and
+ all servers that have clients on the channel. Router MUST also send
+ the SILC_NOTIFY_TYPE_JOIN notify type to local clients on the channel
+ and to local servers that have clients on the channel.
+
+ If the channel does not exist on the router's local list it MUST
+ check the global list whether the channel exists at all. If it does
+ the client is joined to the channel as described previously. If
+ the channel does not exist the channel is created and the client
+ is joined to the channel. The channel key is also created and
+ distributed as previously described. The client joining to the created
+ channel is made automatically channel founder and both channel founder
+ and channel operator privileges are set for the client.
+
+ If the router created the channel in the process, information about the
+ new channel MUST be broadcast to all routers. This is done by
+ broadcasting SILC_PACKET_NEW_CHANNEL packet to the router's primary
+ route. When the router joins the client to the channel it MUST also
+ send information about newly joined client to all routers in the SILC
+ network. This is done by broadcasting the SILC_NOTIFY_TYPE_JOIN notify
+ type to the router's primary route.
+
+ It is important to note that new channel key is created always when
+ new client joins to channel, whether the channel has existed previously
+ or not. This way the new client on the channel is not able to decrypt
+ any of the old traffic on the channel. Client which receives the reply to
+ the join command MUST start using the received Channel ID in the channel
+ message communication thereafter. Client also receives the key for the
+ channel in the command reply. Note that the channel key is never
+ generated or distributed if the SILC_CMODE_PRIVKEY mode is set.
+
+
+4.4 Channel Key Generation
+
+ Channel keys are created by router which creates the channel by taking
+ enough randomness from cryptographically strong random number generator.
+ The key is generated always when channel is created, when new client
+ joins a channel and after the key has expired. Key could expire for
+ example in an hour.
+
+ The key MUST also be re-generated whenever some client leaves a channel.
+ In this case the key is created from scratch by taking enough randomness
+ from the random number generator. After that the key is distributed to
+ all clients on the channel. However, channel keys are cell specific thus
+ the key is created only on the cell where the client, which left the
+ channel, exists. While the server or router is creating the new channel
+ key, no other client may join to the channel. Messages that are sent
+
+
+
+Riikonen [Page 44]
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+Internet Draft 15 January 2007
+
+
+ while creating the new key are still processed with the old key. After
+ server has sent the SILC_PACKET_CHANNEL_KEY packet client MUST start
+ using the new key. If server creates the new key the server MUST also
+ send the new key to its router. See [SILC2] for more information about
+ how channel messages must be encrypted and decrypted when router is
+ processing them.
+
+ If the key changes very often due to joining traffic on the channel it
+ is RECOMMENDED that client implementation would cache some of the old
+ channel keys for short period of time so that it is able to decrypt all
+ channel messages it receives. It is possible that on a heavy traffic
+ channel a message encrypted with channel key that was just changed
+ is received by client after the new key was set into use. This is
+ possible because not all clients may receive the new key at the same
+ time, and may still be sending messages encrypted with the old key.
+
+ When client receives the SILC_PACKET_CHANNEL_KEY packet with the
+ Channel Key Payload it MUST process the key data to create encryption
+ and decryption key, and to create the MAC key that is used to compute
+ the MACs of the channel messages. The processing is as follows:
+
+ channel_key = raw key data
+ MAC key = hash(raw key data)
+
+ The raw key data is the key data received in the Channel Key Payload.
+ It is used for both encryption and decryption. The hash() is the hash
+ function used with the HMAC of the channel. Note that the server also
+ MUST save the channel key.
+
+
+4.5 Private Message Sending and Reception
+
+ Private messages are sent point to point. Client explicitly destine
+ a private message to specific client that is delivered to only to that
+ client. No other client may receive the private message. The receiver
+ of the private message is destined in the SILC Packet Header as in any
+ other packet as well. The Source ID in the SILC Packet Header MUST be
+ the ID of the sender of the message.
+
+ If the sender of a private message does not know the receiver's Client
+ ID, it MUST resolve it from server. There are two ways to resolve the
+ client ID from server; it is RECOMMENDED that client implementations
+ send SILC_COMMAND_IDENTIFY command to receive the Client ID. Client
+ MAY also send SILC_COMMAND_WHOIS command to receive the Client ID.
+ If the sender has received earlier a private message from the receiver
+ it should have cached the Client ID from the SILC Packet Header.
+
+ If server receives a private message packet which includes invalid
+
+
+
+Riikonen [Page 45]
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+Internet Draft 15 January 2007
+
+
+ destination Client ID the server MUST send SILC_NOTIFY_TYPE_ERROR
+ notify to the client with error status indicating that such Client ID
+ does not exist.
+
+ See [SILC2] for description of private message encryption and decryption
+ process.
+
+
+4.6 Private Message Key Generation
+
+ Private message MAY be protected with a key generated by the client.
+ One way to generate private message key is to use static or pre-shared
+ keys in the client implementation. Client that wants to indicate other
+ client on the network that a private message key should be set, the
+ client MAY send SILC_PACKET_PRIVATE_MESSAGE_KEY packet to indicate this.
+ The actual key material has to be transferred outside the SILC network,
+ or it has to be pre-shared key. The client receiving this packet knows
+ that the sender wishes to use private message key in private message
+ communication. In case of static or pre-shared keys the IV used in
+ the encryption SHOULD be chosen randomly. Sending the
+ SILC_PACKET_PRIVATE_MESSAGE_KEY is not mandatory, and clients may
+ naturally agree to use a key without sending the packet.
+
+ Another choice to use private message keys is to negotiate fresh key
+ material by performing the Key Agreement. The SILC_PACKET_KEY_AGREEMENT
+ packet MAY be used to negotiate the fresh key material. In this case
+ the resulting key material is used to secure the private messages.
+ Also, the IV used in encryption is used as defined in [SILC3], unless
+ otherwise stated by the encryption mode used. By performing Key
+ Agreement the clients can also negotiate the cipher and HMAC to be used
+ in the private message encryption and to negotiate additional security
+ parameters. The actual Key Agreement [SILC2] is performed by executing
+ the SILC Key Exchange protocol [SILC3], peer to peer. Because of NAT
+ devices in the network, it might be impossible to perform the Key
+ Agreement. In this case using static or pre-shared key and sending the
+ SILC_PACKET_PRIVATE_MESSAGE_KEY to indicate the use of a private message
+ key is a working alternative.
+
+ If the key is pre-shared key or other key material not generated by
+ Key Agreement, then the key material SHOULD be processed as defined
+ in [SILC3]. In the processing, however, the HASH, as defined in [SILC3]
+ MUST be ignored. After processing the key material it is employed as
+ defined in [SILC3]. If the SILC_PACKET_PRIVATE_MESSAGE_KEY was sent,
+ then it defines the cipher and HMAC to be used. The hash algorithm to be
+ used in the key material processing is the one that HMAC algorithm is
+ defined to use. If the SILC_PACKET_PRIVATE_MESSAGE_KEY was not sent at
+ all, then the hash algorithm to be used SHOULD be SHA1. In this case
+ also, implementations SHOULD use the SILC protocol's mandatory cipher
+
+
+
+Riikonen [Page 46]
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+Internet Draft 15 January 2007
+
+
+ and HMAC in private message encryption.
+
+
+4.7 Channel Message Sending and Reception
+
+ Channel messages are delivered to a group of users. The group forms a
+ channel and all clients on the channel receives messages sent to the
+ channel. The Source ID in the SILC Packet Header MUST be the ID
+ of the sender of the message.
+
+ Channel messages are destined to a channel by specifying the Channel ID
+ as Destination ID in the SILC Packet Header. The server MUST then
+ distribute the message to all clients, except to the original sender,
+ on the channel by sending the channel message destined explicitly to a
+ client on the channel. However, the Destination ID MUST still remain
+ as the Channel ID.
+
+ If server receives a channel message packet which includes invalid
+ destination Channel ID the server MUST send SILC_NOTIFY_TYPE_ERROR
+ notify to the sender with error status indicating that such Channel ID
+ does not exist.
+
+ See the [SILC2] for description of channel message routing for router
+ servers, and channel message encryption and decryption process.
+
+
+4.8 Session Key Regeneration
+
+ Session keys MUST be regenerated periodically, say, once in an hour.
+ The re-key process is started by sending SILC_PACKET_REKEY packet to
+ other end, to indicate that re-key must be performed. The initiator
+ of the connection SHOULD initiate the re-key.
+
+ If perfect forward secrecy (PFS) flag was selected in the SILC Key
+ Exchange protocol [SILC3] the re-key MUST cause new key exchange with
+ SKE protocol. In this case the protocol is secured with the old key
+ and the protocol results to new key material. See [SILC3] for more
+ information. After the SILC_PACKET_REKEY packet is sent the sender
+ will perform the SKE protocol.
+
+ If PFS flag was set the resulted key material is processed as described
+ in the section Processing the Key Material in [SILC3]. The difference
+ with re-key in the processing is that the initial data for the hash
+ function is just the resulted key material and not the HASH as it
+ is not computed at all with re-key. Other than that, the key processing
+ it equivalent to normal SKE negotiation.
+
+ If PFS flag was not set, which is the default case, then re-key is done
+
+
+
+Riikonen [Page 47]
+\f
+Internet Draft 15 January 2007
+
+
+ without executing SKE protocol. In this case, the new key is created by
+ providing the current sending encryption key to the SKE protocol's key
+ processing function. The process is described in the section Processing
+ the Key Material in [SILC3]. The difference in the processing is that
+ the initial data for the hash function is the current sending encryption
+ key and not the SKE's KEY and HASH values. Other than that, the key
+ processing is equivalent to normal SKE negotiation.
+
+ After both parties have regenerated the session key, both MUST send
+ SILC_PACKET_REKEY_DONE packet to each other. These packets are still
+ secured with the old key. After these packets, the subsequent packets
+ MUST be protected with the new key. Note that, in case SKE was performed
+ again the SILC_PACKET_SUCCESS is not sent. The SILC_PACKET_REKEY_DONE
+ is sent in its stead.
+
+
+4.9 Command Sending and Reception
+
+ Client usually sends the commands in the SILC network. In this case
+ the client simply sends the command packet to server and the server
+ processes it and replies with command reply packet. See the [SILC4]
+ for detailed description of all commands.
+
+ However, if the server is not able to process the command, it is sent to
+ the server's router. This is case for example with commands such as
+ SILC_COMMAND_JOIN and SILC_COMMAND_WHOIS commands. However, there are
+ other commands as well [SILC4]. For example, if client sends the WHOIS
+ command requesting specific information about some client the server must
+ send the WHOIS command to router so that all clients in SILC network are
+ searched. The router, on the other hand, sends the WHOIS command further
+ to receive the exact information about the requested client. The WHOIS
+ command travels all the way to the server which owns the client and it
+ replies with command reply packet. Finally, the server which sent the
+ command receives the command reply and it must be able to determine which
+ client sent the original command. The server then sends command reply to
+ the client. Implementations should have some kind of cache to handle, for
+ example, WHOIS information. Servers and routers along the route could all
+ cache the information for faster referencing in the future.
+
+ The commands sent by server may be sent hop by hop until someone is able
+ to process the command. However, it is preferred to destine the command
+ as precisely as it is possible. In this case, other routers en route
+ MUST route the command packet by checking the true sender and true
+ destination of the packet. However, servers and routers MUST NOT route
+ command reply packets to clients coming from other servers. Client
+ MUST NOT accept command reply packet originated from anyone else but
+ from its own server.
+
+
+
+
+Riikonen [Page 48]
+\f
+Internet Draft 15 January 2007
+
+
+4.10 Closing Connection
+
+ When remote client connection is closed the server MUST send the notify
+ type SILC_NOTIFY_TYPE_SIGNOFF to its primary router and to all channels
+ the client was joined. The server MUST also save the client's information
+ for a period of time for history purposes.
+
+ When remote server or router connection is closed the server or router
+ MUST also remove all the clients that was behind the server or router
+ from the SILC Network. The server or router MUST also send the notify
+ type SILC_NOTIFY_TYPE_SERVER_SIGNOFF to its primary router and to all
+ local clients that are joined on the same channels with the remote
+ server's or router's clients.
+
+ Router server MUST also check whether some client in the local cell
+ is watching for the nickname this client has, and send the
+ SILC_NOTIFY_TYPE_WATCH to the watcher, unless the client which left
+ the network has the SILC_UMODE_REJECT_WATCHING user mode set.
+
+
+4.11 Detaching and Resuming a Session
+
+ SILC protocol provides a possibility for a client to detach itself from
+ the network without actually signing off from the network. The client
+ connection to the server is closed but the client remains as valid client
+ in the network. The client may then later resume its session back from
+ any server in the network.
+
+ When client wishes to detach from the network it MUST send the
+ SILC_COMMAND_DETACH command to its server. The server then MUST set
+ SILC_UMODE_DETACHED mode to the client and send SILC_NOTIFY_UMODE_CHANGE
+ notify to its primary router, which then MUST broadcast it further
+ to other routers in the network. This user mode indicates that the
+ client is detached from the network. Implementations MUST NOT use
+ the SILC_UMODE_DETACHED flag to determine whether a packet can be sent
+ to the client. All packets MUST still be sent to the client even if
+ client is detached from the network. Only the server that originally
+ had the active client connection is able to make the decision after it
+ notices that the network connection is not active. In this case the
+ default case is to discard the packet.
+
+ The SILC_UMODE_DETACHED flag cannot be set by client itself directly
+ with SILC_COMMAND_UMODE command, but only implicitly by sending the
+ SILC_COMMAND_DETACH command. The flag also cannot be unset by the
+ client, server or router with SILC_COMMAND_UMODE command, but only
+ implicitly by sending and receiving the SILC_PACKET_RESUME_CLIENT
+ packet.
+
+
+
+
+Riikonen [Page 49]
+\f
+Internet Draft 15 January 2007
+
+
+ When the client wishes to resume its session in the SILC Network it
+ connects to a server in the network, which MAY also be a different
+ from the original server, and performs normal procedures regarding
+ creating a connection as described in section 4.1. After the SKE
+ and the Connection Authentication protocols has been successfully
+ completed the client MUST NOT send SILC_PACKET_NEW_CLIENT packet, but
+ MUST send SILC_PACKET_RESUME_CLIENT packet. This packet is used to
+ perform the resuming procedure. The packet MUST include the detached
+ client's Client ID, which the client must know. It also includes
+ Authentication Payload which includes signature computed with the
+ client's private key. The signature is computed as defined in the
+ section 3.9.1. Thus, the authentication method MUST be based in
+ public key authentication.
+
+ When server receive the SILC_PACKET_RESUME_CLIENT packet it MUST
+ do the following: Server checks that the Client ID is valid client
+ and that it has the SILC_UMODE_DETACHED mode set. Then it verifies
+ the Authentication Payload with the detached client's public key.
+ If it does not have the public key it retrieves it by sending
+ SILC_COMMAND_GETKEY command to the server that has the public key from
+ the original client connection. The server MUST NOT use the public
+ key received in the SKE protocol for this connection. If the
+ signature is valid the server unsets the SILC_UMODE_DETACHED flag,
+ and sends the SILC_PACKET_RESUME_CLIENT packet to its primary router.
+ The routers MUST broadcast the packet and unset the SILC_UMODE_DETACHED
+ flag when the packet is received. If the server is router server it
+ also MUST send the SILC_PACKET_RESUME_CLIENT packet to the original
+ server whom owned the detached client.
+
+ The servers and routers that receives the SILC_PACKET_RESUME_CLIENT
+ packet MUST know whether the packet already has been received for
+ the client. It is a protocol error to attempt to resume the client
+ session from more than one server. The implementations could set
+ internal flag that indicates that the client is resumed. If router
+ receive SILC_PACKET_RESUME_CLIENT packet for client that is already
+ resumed the client MUST be killed from the network. This would
+ indicate that the client is attempting to resume the session more
+ than once which is a protocol error. In this case the router sends
+ SILC_NOTIFY_TYPE_KILLED to the client. All routers that detect
+ the same situation MUST also send the notify for the client.
+
+ The servers and routers that receive the SILC_PACKET_RESUME_CLIENT
+ must also understand that the client may not be found behind the
+ same server that it originally came from. They must update their
+ caches according to this. The server that now owns the client session
+ MUST check whether the Client ID of the resumed client is based
+ on the server's Server ID. If it is not it creates a new Client
+ ID and send SILC_NOTIFY_TYPE_NICK_CHANGE to the network. It MUST
+
+
+
+Riikonen [Page 50]
+\f
+Internet Draft 15 January 2007
+
+
+ also send the channel keys of all channels that the client has
+ joined to the client since it does not have them. Whether the
+ Client ID was changed or not the server MUST send SILC_PACKET_NEW_ID
+ packet to the client. Only after this is the client resumed back
+ to the network and may start sending packets and messages.
+
+ It is also possible that the server did not know about the global
+ channels before the client resumed. In this case it joins the client
+ to the channels, generates new channel keys and distributes the keys
+ to the channels as described in section 4.4.
+
+ It is an implementation issue for how long servers keep detached client
+ sessions. It is RECOMMENDED that the detached sessions would be
+ persistent as long as the server is running.
+
+
+
+4.12 UDP/IP Connections
+
+ SILC protocol allows the use of UDP/IP instead of TCP/IP. There may be
+ many reasons to use UDP, such as video and audio conferencing might
+ be more efficient with UDP.
+
+ When UDP/IP is used, in the SILC Key Exchange protocol the IV Included
+ flag MUST be set and the first 16-bits of the Cookie field in the Key
+ Exchange Start Payload MUST include the port that the other end will use
+ as the SILC session port. The port is in MSB first order. Both initiator
+ and responder will set the port they are going to use and all packets
+ after the SKE has been completed with the SILC_PACKET_SUCCESS packet MUST
+ be sent to the specified port. Initiator will send them to the port
+ responder specified and vice versa. When verifying the cookie for
+ modifications the first two bytes are to be ignored in case IV Included
+ flag has been set.
+
+ The default SILC port or port where the SILC server is listenning for
+ incoming packets is used only during initial key exchange protocol. After
+ SKE has been completed all packets are sent to the specified ports,
+ including connection authentication packets and rekey packets even when
+ PFS is used in rekey.
+
+ Changing the ports during SILC session is possible only by first detaching
+ from the server (with client-server connections) and then performing the
+ SILC Key Exchange protocol from the beginning and resuming the detached
+ session.
+
+ Since the UDP is unreliable transport the SKE packets may not arrive to
+ the recipient. Implementation should support retransmission of SKE
+ packets by using exponential backoff algorithm. Also other SILC packets
+
+
+
+Riikonen [Page 51]
+\f
+Internet Draft 15 January 2007
+
+
+ such as messages may drop en route. With message packets only way to
+ assure reliable delivery is to use message acking and retransmit the
+ message by using for example exponential backoff algorithm. With SKE
+ packets the initial timeout value should be no more than 1000
+ milliseconds. With message packets the initial timeout value should be
+ around 5000 milliseconds.
+
+
+5 Security Considerations
+
+ Security is central to the design of this protocol, and these security
+ considerations permeate the specification. Common security considerations
+ such as keeping private keys truly private and using adequate lengths for
+ symmetric and asymmetric keys must be followed in order to maintain the
+ security of this protocol.
+
+ Special attention must also be paid to the servers and routers that are
+ running the SILC service. The SILC protocol's security depends greatly
+ on the security and the integrity of the servers and administrators that
+ are running the service. It is recommended that some form of registration
+ is required by the server and router administrator prior to acceptance to
+ the SILC Network. Even though the SILC protocol is secure in a network
+ of mutual distrust between clients, servers, routers and administrators
+ of the servers, the client should be able to trust the servers they are
+ using if they wish to do so.
+
+ It however must be noted that if the client requires absolute security
+ by not trusting any of the servers or routers in the SILC Network, it can
+ be accomplished by negotiating private secret keys outside the SILC
+ Network, either using SKE or some other key exchange protocol, or to use
+ some other external means for distributing the keys. This applies for
+ all messages, private messages and channel messages.
+
+ It is important to note that SILC, like any other security protocol, is
+ not a foolproof system; the SILC servers and routers could very well be
+ compromised. However, to provide an acceptable level of security and
+ usability for end users, the protocol uses many times session keys or
+ other keys generated by the servers to secure the messages. This is an
+ intentional design feature to allow ease of use for end users. This way
+ the network is still usable, and remains encrypted even if the external
+ means of distributing the keys is not working. The implementation,
+ however, may like to not follow this design feature, and may always
+ negotiate the keys outside SILC network. This is an acceptable solution
+ and many times recommended. The implementation still must be able to
+ work with the server generated keys.
+
+ If this is unacceptable for the client or end user, the private keys
+ negotiated outside the SILC Network should always be used. In the end
+
+
+
+Riikonen [Page 52]
+\f
+Internet Draft 15 January 2007
+
+
+ it is the implementor's choice whether to negotiate private keys by
+ default or whether to use the keys generated by the servers.
+
+ It is also recommended that router operators in the SILC Network would
+ form a joint forum to discuss the router and SILC Network management
+ issues. Also, router operators along with the cell's server operators
+ should have a forum to discuss the cell management issues.
+
+
+6 References
+
+ [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
+ January 2007.
+
+ [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
+ Protocols", Internet Draft, January 2007.
+
+ [SILC4] Riikonen, P., "SILC Commands", Internet Draft, January 2007.
+
+ [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
+ RFC 1459, May 1993.
+
+ [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
+ April 2000.
+
+ [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
+ 2811, April 2000.
+
+ [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
+ 2812, April 2000.
+
+ [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
+ 2813, April 2000.
+
+ [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
+ Internet Draft.
+
+ [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
+ November 1998.
+
+ [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
+ September 1999.
+
+ [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
+ Infrastructure, Certificate and CRL Profile", RFC 2459,
+ January 1999.
+
+ [Schneier] Schneier, B., "Applied Cryptography Second Edition",
+
+
+
+Riikonen [Page 53]
+\f
+Internet Draft 15 January 2007
+
+
+ John Wiley & Sons, New York, NY, 1996.
+
+ [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
+ CRC Press 1997.
+
+ [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
+ RFC 2412, November 1998.
+
+ [ISAKMP] Maughan D., et al, "Internet Security Association and
+ Key Management Protocol (ISAKMP)", RFC 2408, November
+ 1998.
+
+ [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
+ (IKE)", RFC 2409, November 1998.
+
+ [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
+ Authentication", RFC 2104, February 1997.
+
+ [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
+ Specifications, Version 2.0", RFC 2437, October 1998.
+
+ [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 3629, November 2003.
+
+ [RFC1321] Rivest R., "The MD5 Message-Digest Algorithm", RFC 1321,
+ April 1992.
+
+ [RFC3174] Eastlake, F., et al., "US Secure Hash Algorithm 1 (SHA1)",
+ RFC 3174, September 2001.
+
+ [PKCS7] Kalinski, B., "PKCS #7: Cryptographic Message Syntax,
+ Version 1.5", RFC 2315, March 1998.
+
+ [RFC2253] Wahl, M., et al., "Lightweight Directory Access Protocol
+ (v3): UTF-8 String Representation of Distinguished Names",
+ RFC 2253, December 1997.
+
+ [RFC3454] Hoffman, P., et al., "Preparation of Internationalized
+ Strings ("stringprep")", RFC 3454, December 2002.
+
+ [SHA256] Eastlake 3rd, D., et al., "US Secure Hash Algorithms (SHA
+ and HMAC-SHA)", RFC 4634, July 2006.
+
+
+
+
+
+
+Riikonen [Page 54]
+\f
+Internet Draft 15 January 2007
+
+
+7 Author's Address
+
+ Pekka Riikonen
+ Helsinki
+ Finland
+
+ EMail: priikone@iki.fi
+
+
+Appendix A
+
+ This appendix defines the stringprep [RFC3454] profile for string
+ identifiers in SILC protocol. Compliant implementation MUST use this
+ profile to prepare the identifier strings in the SILC protocol. The
+ profile defines the following as required by [RFC3454].
+
+ - Intended applicability of the profile: the following identifiers in
+ the SILC Protocol; nicknames, usernames, server names, hostnames,
+ service names, algorithm names and other security property names [SILC3],
+ and SILC Public Key name.
+
+ - The character repertoire that is the input and output to
+ stringprep: Unicode 3.2 with the list of unassigned code points
+ being the Table A.1, as defined in [RFC3454].
+
+ - The mapping tables used: the following tables are used, in order,
+ as defined in [RFC3454].
+
+ Table B.1
+ Table B.2
+
+ The mandatory case folding is done using the Table B.2 which includes
+ the characters for the normalization form KC.
+
+ - The Unicode normalization used: the Unicode normalization form
+ KC is used, as defined in [RFC3454].
+
+ - The prohibited characters as output: the following tables are used
+ to prohibit characters, as defined in [RFC3454];
+
+ Table C.1.1
+ Table C.1.2
+ Table C.2.1
+ Table C.2.2
+ Table C.3
+ Table C.4
+ Table C.5
+ Table C.6
+
+
+
+Riikonen [Page 55]
+\f
+Internet Draft 15 January 2007
+
+
+ Table C.7
+ Table C.8
+ Table C.9
+
+ - Additional prohibited characters as output: in addition, the following
+ tables are used to prohibit characters, as defined in this document;
+
+ Appendix C
+ Appendix D
+
+ - The bidirectional string testing used: bidirectional string testing
+ is ignored in this profile.
+
+ This profile is to be maintained in the IANA registry for stringprep
+ profiles. The name of this profile is "silc-identifier-prep" and this
+ document defines the profile. This document defines the first version of
+ this profile.
+
+
+Appendix B
+
+ This appendix defines the stringprep [RFC3454] profile for channel name
+ strings in SILC protocol. Compliant implementation MUST use this profile
+ to prepare the channel name strings in the SILC protocol. The profile
+ defines the following as required by [RFC3454].
+
+ - Intended applicability of the profile: channel names.
+
+ - The character repertoire that is the input and output to
+ stringprep: Unicode 3.2 with the list of unassigned code points
+ being the Table A.1, as defined in [RFC3454].
+
+ - The mapping tables used: the following tables are used, in order,
+ as defined in [RFC3454].
+
+ Table B.1
+ Table B.2
+
+ The mandatory case folding is done using the Table B.2 which includes
+ the characters for the normalization form KC.
+
+ - The Unicode normalization used: the Unicode normalization form
+ KC is used, as defined in [RFC3454].
+
+ - The prohibited characters as output: the following tables are used
+ to prohibit characters, as defined in [RFC3454];
+
+ Table C.1.1
+
+
+
+Riikonen [Page 56]
+\f
+Internet Draft 15 January 2007
+
+
+ Table C.1.2
+ Table C.2.1
+ Table C.2.2
+ Table C.3
+ Table C.4
+ Table C.5
+ Table C.6
+ Table C.7
+ Table C.8
+ Table C.9
+
+ - Additional prohibited characters as output: in addition, the following
+ tables are used to prohibit characters, as defined in this document;
+
+ Appendix D
+
+ - The bidirectional string testing used: bidirectional string testing
+ is ignored in this profile.
+
+ This profile is to be maintained in the IANA registry for stringprep
+ profiles. The name of this profile is "silc-identifier-ch-prep" and this
+ document defines the profile. This document defines the first version of
+ this profile.
+
+
+Appendix C
+
+ This appendix defines additional prohibited characters in the identifier
+ strings as defined in the stringprep profile in Appendix A.
+
+ Reserved US-ASCII characters
+ 0021 002A 002C 003F 0040
+
+
+Appendix D
+
+ This appendix defines additional prohibited characters in the identifier
+ strings as defined in the stringprep profile in Appendix A and Appendix B.
+ Note that the prohibited character tables listed in the Appendix A and
+ Appendix B may include some of the same characters listed in this
+ appendix as well.
+
+ Symbol characters and other symbol like characters
+ 00A2-00A9 00AC 00AE 00AF 00B0 00B1 00B4 00B6 00B8 00D7 00F7
+ 02C2-02C5 02D2-02FF 0374 0375 0384 0385 03F6 0482 060E 060F
+ 06E9 06FD 06FE 09F2 09F3 09FA 0AF1 0B70 0BF3-0BFA 0E3F
+ 0F01-0F03 0F13-0F17 0F1A-0F1F 0F34 0F36 0F38 0FBE 0FBF
+ 0FC0-0FC5 0FC7-0FCF 17DB 1940 19E0-19FF 1FBD 1FBF-1FC1
+
+
+
+Riikonen [Page 57]
+\f
+Internet Draft 15 January 2007
+
+
+ 1FCD-1FCF 1FDD-1FDF 1FED-1FEF 1FFD 1FFE 2044 2052 207A-207C
+ 208A-208C 20A0-20B1 2100-214F 2150-218F 2190-21FF 2200-22FF
+ 2300-23FF 2400-243F 2440-245F 2460-24FF 2500-257F 2580-259F
+ 25A0-25FF 2600-26FF 2700-27BF 27C0-27EF 27F0-27FF 2800-28FF
+ 2900-297F 2980-29FF 2A00-2AFF 2B00-2BFF 2E9A 2EF4-2EFF
+ 2FF0-2FFF 303B-303D 3040 3095-3098 309F-30A0 30FF-3104
+ 312D-3130 318F 31B8-31FF 321D-321F 3244-325F 327C-327E
+ 32B1-32BF 32CC-32CF 32FF 3377-337A 33DE-33DF 33FF 4DB6-4DFF
+ 9FA6-9FFF A48D-A48F A4A2-A4A3 A4B4 A4C1 A4C5 A4C7-ABFF
+ D7A4-D7FF FA2E-FAFF FFE0-FFEE FFFC 10000-1007F 10080-100FF
+ 10100-1013F 1D000-1D0FF 1D100-1D1FF 1D300-1D35F 1D400-1D7FF
+
+ Other characters
+ E0100-E01EF
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Riikonen [Page 58]
+\f
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>SILC - Secure Internet Live Conferencing</title>
- <meta name="description" content="SILC - Secure Internet Live Conferencing">
+ <meta name="description" content="SILC - Secure Internet Live Conferencing, modern secure conferencing and chat protocol">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="css/normalize.css">
<footer>
<nav>
-<!--
<a href="info.html">INFO</a>
--->
<a href="client.html">CLIENT</a>
<a href="server.html">SERVER</a>
<a href="dev.html">DEVELOPMENT</a>
<center><a href="/"><img src="img/silc.svg" height=64 alt="SILC logo"></a></center>
</header>
- <div id="container2">Download SILC Client</div>
+ <div id="container2">Secure Internet Live Conferencing</div>
- <!-- Download -->
<center>
+ <div style="width:85%">
+ SILC protocol is a modern conferencing and chat protocol designed with
+ high security as its main feature.
+ <div class="list">
+ <ul>
+ <li>Fully encrypted and authenticated transport</li>
+ <li>End-to-end encrypted and authenticated private messages</li>
+ <li>Encrypted and authenticated channel and group messages</li>
+ <li>Secure video and audio conferencing, image and sound messagse</li>
+ <li>Authenticated Diffie-Hellman key exchange and Perfect Forward Secrecy</li>
+ <li>Off-the-record or On-the-record conversations with or without digital signatures</li>
+ <li>Secure file transfer</li>
+ <li>And every other feature you can expect from a modern conferencing and chat protocol...</li>
+ <li><a href="docs/protocol">See all the details in SILC protocol specifications</a></li>
+ </ul>
+ </div>
+
+ </div>
</center>
<footer>
<footer>
<nav>
-<!--
<a href="info.html">INFO</a>
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<a href="server.html">SERVER</a>
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