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+.pl 10.0i
+.po 0
+.ll 7.2i
+.lt 7.2i
+.nr LL 7.2i
+.nr LT 7.2i
+.ds LF Riikonen
+.ds RF FORMFEED[Page %]
+.ds CF
+.ds LH Internet Draft
+.ds RH XXX
+.ds CH
+.na
+.hy 0
+.in 0
+.nf
+Network Working Group P. Riikonen
+Internet-Draft
+draft-riikonen-silc-pp-04.txt XXX
+Expires: XXX
+
+.in 3
+
+.ce 2
+SILC Packet Protocol
+<draft-riikonen-silc-pp-04.txt>
+
+.ti 0
+Status of this Memo
+
+This document is an Internet-Draft and is in full conformance with
+all provisions of Section 10 of RFC 2026. 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/ietf/1id-abstracts.txt
+
+The list of Internet-Draft Shadow Directories can be accessed at
+http://www.ietf.org/shadow.html
+
+The distribution of this memo is unlimited.
+
+
+.ti 0
+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 Internet Draft [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.
+
+
+
+
+
+
+
+
+
+.ti 0
+Table of Contents
+
+.nf
+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 ......................................... 7
+ 2.3.1 SILC Packet Payloads ................................ 16
+ 2.3.2 Generic payloads .................................... 16
+ 2.3.2.1 ID Payload .................................. 16
+ 2.3.2.2 Argument Payload ............................ 17
+ 2.3.2.3 Channel Payload ............................. 18
+ 2.3.2.4 Public Key Payload .......................... 19
+ 2.3.3 Disconnect Payload .................................. 19
+ 2.3.4 Success Payload ..................................... 19
+ 2.3.5 Failure Payload ..................................... 20
+ 2.3.6 Reject Payload ...................................... 21
+ 2.3.7 Notify Payload ...................................... 22
+ 2.3.8 Error Payload ....................................... 21
+ 2.3.9 Channel Message Payload ............................. 28
+ 2.3.10 Channel Key Payload ................................ 31
+ 2.3.11 Private Message Payload ............................ 33
+ 2.3.12 Private Message Key Payload ........................ 34
+ 2.3.13 Command Payload .................................... 36
+ 2.3.14 Command Reply Payload .............................. 37
+ 2.3.15 Connection Auth Request Payload .................... 37
+ 2.3.16 New ID Payload ..................................... 38
+ 2.3.17 New Client Payload ................................. 39
+ 2.3.18 New Server Payload ................................. 40
+ 2.3.19 New Channel Payload ................................ 41
+ 2.3.20 Key Agreement Payload .............................. 42
+ 2.3.21 Cell Routers Payload ............................... 43
+ 2.4 SILC ID Types ............................................. 44
+ 2.5 Packet Encryption And Decryption .......................... 44
+ 2.5.1 Normal Packet Encryption And Decryption ............. 45
+ 2.5.2 Channel Message Encryption And Decryption ........... 45
+ 2.5.3 Private Message Encryption And Decryption ........... 46
+ 2.6 Packet MAC Generation ..................................... 47
+ 2.7 Packet Padding Generation ................................. 47
+ 2.8 Packet Compression ........................................ 48
+ 2.9 Packet Sending ............................................ 48
+ 2.10 Packet Reception ......................................... 49
+ 2.11 Packet Routing ........................................... 49
+ 2.12 Packet Broadcasting ...................................... 50
+3 Security Considerations ....................................... 50
+4 References .................................................... 50
+5 Author's Address .............................................. 52
+
+.ti 0
+List of Figures
+
+.nf
+Figure 1: Typical SILC Packet
+Figure 2: SILC Packet Header
+Figure 3: ID Payload
+Figure 4: Argument Payload
+Figure 5: Channel Payload
+Figure 6: Public Key Payload
+Figure 7: Disconnect Payload
+Figure 8: Success Payload
+Figure 9: Failure Payload
+Figure 10: Reject Payload
+Figure 11: Notify Payload
+Figure 12: Error Payload
+Figure 13: Channel Message Payload
+Figure 14: Channel Key Payload
+Figure 15: Private Message 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: Cell Routers Payload
+
+
+.ti 0
+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 Internet Draft [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 basis of SILC protocol relies in the SILC packets and it is with
+out a doubt the most important part of the protocol. It is also probably
+the most complicated part of the protocol. Packets are used all the
+time in the SILC network to send messages, commands and other information.
+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 of the packet and destination of the
+packet.
+
+
+.ti 0
+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].
+
+
+.ti 0
+2 SILC Packet Protocol
+
+.ti 0
+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.
+
+
+.in 5
+.nf
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+| n bytes | 1 - n bytes | n bytes | n bytes
+| SILC Header | Padding | Data Payload | MAC
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+.in 3
+
+.ce
+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 and first two (2) bytes of the
+header (thus first two bytes of the packet) are not encrypted. The
+first two (2) bytes are the length of the packet which is not encrypted.
+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 16 bytes. The padding is always
+encrypted.
+
+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. The MAC is always computed from the packet
+before the encryption is applied to the packet. If compression is used
+in the packet the MAC is computed after the compression has been
+applied. The compression, on the other hand, is always applied before
+encryption.
+
+All fields in all packet payloads are always in MSB (most significant
+byte first) order.
+
+
+.ti 0
+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. (*) indicates
+that this field is never encrypted. Other fields are always encrypted.
+
+.in 5
+.nf
+ 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 |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Source ID Length | Destination ID Length |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Src ID Type | |
++-+-+-+-+-+-+-+-+ +
+| |
+~ Source ID ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Dst ID Type | |
++-+-+-+-+-+-+-+-+ +
+| |
+~ Destination ID ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 2: SILC Packet Header
+
+
+.in 6
+o Payload Length (2 bytes) - Is the length of the packet
+ not including the padding of the packet. This field must
+ not be encrypted but must always be authenticated.
+
+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 must include private
+ message that is encrypted using private key set by
+ client. Servers does not know anything about this
+ key and this causes that the private message is
+ not handled by the server at all, it is just
+ passed 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 cannot
+ send broadcast packet and normal server cannot send
+ broadcast packet. 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.
+
+.in 3
+
+
+
+
+o Packet Type (1 byte) - Is 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 Source ID Length (2 bytes) - Indicates the length of the
+ Source ID field in the header, not including this or any
+ other fields.
+
+o Destination ID Length (2 bytes) - 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
+ 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.
+
+
+.ti 0
+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, as a one
+byte, 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 of these packet
+types.
+
+The below list of the SILC Packet types includes reference to the packet
+payload as well. Packet payloads are the actual packet, that is, the data
+that the packet consists of. 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
+router to send 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 has not 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. If the packet is allowed to be sent to
+indirectly connected entity it is mentioned separately in the packet
+description (unless it is obvious as in private and channel message
+packets). Other packets MUST NOT be sent or accepted, if sent, to
+indirectly connected entities.
+
+List of SILC Packet types are defined as follows.
+
+.in 1
+ 0 SILC_PACKET_NONE
+
+ This type is reserved and it is never sent.
+
+
+ 1 SILC_PACKET_DISCONNECT
+
+ This packet is sent to disconnect the remote end. Reason of
+ the disconnection is sent inside the packet payload. Client
+ usually does not send this packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.3 Disconnect Payload
+
+
+ 2 SILC_PACKET_SUCCESS
+
+ This packet is sent upon successful execution of some protocol.
+ The status of the success is sent in the packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.4 Success Payload
+
+
+ 3 SILC_PACKET_FAILURE
+
+ This packet is sent upon failure of some protocol. The status
+ of the failure is sent in the packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.5 Failure Payload
+
+
+ 4 SILC_PACKET_REJECT
+
+ This packet MAY be sent upon rejection of some protocol.
+ The status of the rejection is sent in the packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.6 Reject Payload
+
+
+ 5 SILC_PACKET_NOTIFY
+
+ This packet is used to send notify message, usually from
+ server to client, although it MAY be sent from server to another
+ server as well. Client MUST NOT send this packet. Server MAY
+ send this packet to channel as well when the packet is
+ distributed to all clients on the channel.
+
+ 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
+ to entity that is indirectly connected to the sender.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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. Channel Keys are distributed by
+ SILC_PACKET_CHANNEL_KEY packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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. Each channel has their own independent keys that
+ is used to protect the traffic on the channel. Only server
+ may send this packet. This packet MAY be sent to entity
+ that is indirectly connected to the sender.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
+ agree the key with the remote client. Pre-shared key MAY be
+ used as well if both of the client knows it, however, it needs
+ to be agreed outside SILC. See more of this in [SILC1].
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.11 Private Message
+ Payload
+
+
+ 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
+
+ This packet is used to agree about a key to be used to protect
+ the private messages between two clients. If this is not sent
+ the normal session key is used to protect the private messages
+ inside SILC network. Agreeing to use specific key to protect
+ private messages adds security, as no server between the two
+ clients will be able to decrypt the private message. However,
+ servers inside SILC network are considered to be trusted, thus
+ using normal session key to protect private messages does not
+ degrade security. Whether to agree to use specific keys by
+ default or to use normal session keys by default, is
+ implementation specific issue. See more of this in [SILC1].
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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 MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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].
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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
+
+ This packet is used as part of the SILC Key Exchange Protocol.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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 the 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 MUST respond with the same
+ packet including the mandatory authentication method.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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].
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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 ID's from server to
+ router and from router to all routers in the SILC network.
+ This is used when for example new client is registered to
+ SILC network. The newly created ID's 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.
+
+ 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.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ 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.
+
+ 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
+ [SILC1] for more information. This packet does not have
+ a payload.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+
+ 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 MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+
+ 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.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+
+ 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.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.20 Key Agreement Payload
+
+
+ 26 SILC_PACKET_CELL_ROUTERS
+
+ This packet is used by primary router in the cell to notify its
+ primary router what other routers (backup routers) exist in the
+ cell. In case of failure of the primary router in the cell the
+ first router in the list will act as primary router of the cell.
+ This packet MAY be sent at anytime after connection has been
+ registered to the primary router. The client MUST NOT send this
+ packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.21 Cell Routers Payload
+
+
+ 27 - 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.
+.in 3
+
+
+.ti 0
+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
+encrypted, as they reside in the data area of the packet which is
+always encrypted.
+
+Payloads described in this section are common payloads that MUST be
+accepted anytime during SILC session. Most of the payloads may only
+be sent with specific packet type which is defined in the description
+of the payload.
+
+There are a lot of other payloads in the 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].
+
+
+.ti 0
+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 payloads.
+
+
+.ti 0
+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's.
+
+
+
+
+
+
+
+
+
+
+
+
+The following diagram represents the ID Payload.
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 3: ID Payload
+
+
+.in 6
+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.
+.in 3
+
+
+.ti 0
+2.3.2.2 Argument Payload
+
+Argument Payload is used to set arguments for any packet payload that
+needs and supports arguments, such as commands. Number of arguments
+associated with a packet MUST be indicated by the packet payload which
+needs 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.
+
+The following diagram represents the Argument Payload.
+
+.in 5
+.nf
+ 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 | Argument Type | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Argument Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 4: Argument Payload
+
+
+.in 6
+o Payload Length (2 bytes) - Length of the argument payload data
+ area not including the length of any other fields in the
+ payload.
+
+o Argument Type (1 byte) - Indicates the type of the argument.
+ Every argument may have a specific type that MUST be defined
+ by the packet payload needing the argument. For example
+ every command specify a number for each argument that maybe
+ 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).
+
+o Argument Data (variable length) - Argument data.
+.in 3
+
+
+.ti 0
+2.3.2.3 Channel Payload
+
+Generic Channel Payload may be used to send information about channel,
+its name, the Channel ID and a mode.
+
+The following diagram represents the Channel Payload.
+
+
+.in 5
+.nf
+ 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 |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 5: New Channel Payload
+
+
+.in 6
+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 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 the 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.
+.in 3
+
+
+.ti 0
+2.3.2.4 Public Key Payload
+
+Generic Public Key Payload may be used to send different types of
+public keys and certificates.
+
+The following diagram represents the Public Key Payload.
+
+
+.in 5
+.nf
+ 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) ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 6: Public Key Payload
+
+
+.in 6
+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. See the [SILC3] for defined public key types.
+
+o Public Key (or certificate) (variable length) - The
+ public key or certificate.
+.in 3
+
+
+.ti 0
+2.3.3 Disconnect Payload
+
+Disconnect payload is sent upon disconnection. The payload is simple;
+reason of disconnection is sent to the disconnected party.
+
+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.
+
+
+.in 5
+.nf
+ 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
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Disconnect Message ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 7: Disconnect Payload
+
+
+
+
+.in 6
+o Disconnect Message (variable length) - Human readable
+ reason of the disconnection.
+.in 3
+
+
+.ti 0
+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.
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 8: Success Payload
+
+
+.in 6
+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
+ Packet Header.
+.in 3
+
+
+
+.ti 0
+2.3.5 Failure Payload
+
+This is opposite of Success Payload. Indication of failure of
+some protocol is sent in the payload.
+
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 9: Failure Payload
+
+
+.in 6
+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.
+.in 3
+
+
+.ti 0
+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.
+
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 10: Reject Payload
+
+
+.in 6
+o Reject Indication (variable length) - Indication of
+ the rejection. This maybe for example some flag that
+ 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.
+.in 3
+
+
+.ti 0
+2.3.7 Notify Payload
+
+Notify payload is used to send notify messages. The payload is usually
+sent from server to client, however, server MAY send it to another
+server as well. This payload MAY also be sent to a channel. Client
+MUST NOT send this payload. The receiver of this payload MAY ignore
+the contents of the payload, however, notify message SHOULD be audited.
+
+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.
+
+.in 5
+.nf
+ 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 |
++-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 11: Notify Payload
+
+
+.in 6
+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 (2 bytes) - Indicates the number of Argument
+ Payloads associated to this payload. Notify types may define
+ arguments to be send along the notify message.
+.in 3
+
+The following list of currently defined notify types. The format for
+notify arguments is same as in SILC commands described in [SILC4].
+Also, all ID's sent in arguments are sent inside ID Payload.
+
+.in 6
+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 between routers and if an client was invited, to the
+ client as well. 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) [<adding client>]
+ (5) [<removing client>]
+
+ 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 <adding
+ client> and the <removing client> indicates the added or removed
+ client from the channel's invite list. The format of the <adding
+ client> and the <removing client> is defined in the [SILC4] with
+ SILC_COMMAND_INVITE command.
+
+ The <adding client> and <removing client> MUST NOT be sent when
+ the packet is destined to a client.
+
+
+2 SILC_NOTIFY_TYPE_JOIN
+
+ Sent when client has joined to 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.
+
+ 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 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.
+
+ 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 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.
+
+ 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.
+
+
+5 SILC_NOTIFY_TYPE_TOPIC_SET
+
+ Sent when topic is set/changed on a channel. This type must be
+ sent only to the clients which is joined on the channel which
+ topic was set or changed.
+
+ Max Arguments: 2
+ Arguments: (1) <Client ID> (2) <topic>
+
+ The <Client ID> is the client which set or changed the <topic>.
+
+
+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.
+
+ Max Arguments: 2
+ Arguments: (1) <Old Client ID> (2) <New Client ID>
+
+ 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.
+
+
+7 SILC_NOTIFY_TYPE_CMODE_CHANGE
+
+ Sent when channel mode has changed. This type MUST be sent only
+ to the clients which is joined on the channel which mode was
+ changed.
+
+ Max Arguments: 4
+ Arguments: (1) <ID Payload> (2) <mode mask>
+ (3) [<cipher>] (4) <[hmac>]
+
+ 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.
+
+
+8 SILC_NOTIFY_TYPE_CUMODE_CHANGE
+
+ Sent when user mode on channel has changed. This type MUST be
+ sent only to the clients which is joined on the channel where
+ the target client is on.
+
+ Max Arguments: 3
+ Arguments: (1) <ID Payload> (2) <mode mask>
+ (3) <Target Client ID>
+
+ 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.
+
+
+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.
+
+
+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 is
+ joined on the channel.
+
+ 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.
+
+
+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.
+
+ Max Arguments: 2000
+ Arguments: (1) <Server ID> (n) [<Client ID> [...]
+
+ The <Server ID> is the server's ID. The rest of the arguments
+ are the Client ID's of the client's 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.
+
+
+12 SILC_NOTIFY_TYPE_KICKED
+
+ Sent when a client has been kicked from a channel. This is
+ sent also to the client which was kicked from the channel.
+ The client which was kicked from the channel MUST be removed
+ from the channel. This notify type is always 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: 2
+ Arguments: (1) <Client ID> (2) [<comment>]
+
+ The <Client ID> is the client which was kicked from the channel.
+ The kicker may have set the <comment> to indicate the reason for
+ the kicking.
+
+
+13 SILC_NOTIFY_TYPE_KILLED
+
+ Sent when a client has been killed from the network. This is sent
+ also to the client which was killed from the network. The client
+ which was killed from the network MUST be removed from the network.
+ This notify type is destined directly to the client which was
+ killed and to channel if the client is on any 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: 2
+ Arguments: (1) <Client ID> (2) [<comment>]
+
+ The <Client ID> is the client which was killed from the network.
+ The killer may have set the <comment> to indicate the reason for
+ the killing.
+
+
+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 type is
+ sent only between routers as broadcast packet.
+
+ Max Arguments: 3
+ Arguments: (1) <Channel ID> (2) [<adding client>]
+ (3) [<removing client>]
+
+ The <Channel ID> is the channel which ban list was changed. The
+ <adding client> is used to indicate that a ban was added and the
+ <removing client> is used to indicate that a ban was removed from
+ the ban list. The format of the <adding client> and the
+ <removing client> is defined in the [SILC4] with SILC_COMMAND_BAN
+ command.
+
+.in 3
+
+Notify types starting from 16384 are reserved for private notify
+message types.
+
+
+.ti 0
+2.3.8 Error Payload
+
+Error payload is sent upon error. 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
+totally 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.
+
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 12: Error Payload
+
+
+.in 6
+o Error Message (variable length) - Human readable error
+ message.
+.in 3
+
+
+.ti 0
+2.3.9 Channel Message Payload
+
+Channel messages are the most common messages sent in the SILC.
+Channel Message Payload is used to send message to channels. These
+messages can only be sent if client has joined to some channel.
+Even though this packet is the most 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 padding SHOULD be random data. 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
+to make it multiple by eight (8) or multiple by the block size
+of the cipher, which ever is larger.
+
+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 payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
+It MUST NOT be sent in any other packet type. The following diagram
+represents the Channel Message Payload.
+
+(*) indicates that the field is not encrypted.
+
+
+.in 5
+.nf
+ 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
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Flags | Message Length |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Message Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Padding Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Padding ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ MAC ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Initial Vector * ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 13: Channel Message Payload
+
+
+.in 6
+o Flags (2 bytes) - Includes the flags of the channel
+ messages. The flags can indicate a reason or purpose
+ for the channel message. Note that the Private Message
+ Payload use these same flags for the same purpose. The
+ following 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
+ of this flag.
+
+ 0x0040 - 0x0200 RESERVED
+
+ Reserved for future flags
+
+ 0x0400 - 0x8000 PRIVATE RANGE
+
+ Private range for free use.
+
+o Message Length (2 bytes) - Indicates the length of the
+ the Message Data field in the payload, not including any
+ other field.
+
+o Message Data (variable length) - The actual message to
+ the channel.
+
+o Padding Length (2 bytes) - Indicates the length of the
+ Padding field in the payload, not including any other
+ field.
+
+o Padding (variable length) - The padding that MUST be
+ applied because this payload is encrypted separately from
+ other parts of the packet.
+
+o MAC (variable length) - The MAC computed from the
+ Message Length, Message Data, Padding Length and Padding
+ fields. This protects the integrity of the plaintext
+ channel message. The receiver can verify from the MAC
+ whether the message decrypted correctly. Also, if more than
+ one private key has been set for the channel, the receiver
+ can verify which of the keys decrypted the message
+ correctly. Note that, this field is encrypted and MUST
+ be added to the padding calculation.
+
+o Initial Vector (variable length) - The initial vector
+ that has been used in packet encryption. It needs to be
+ used in the packet decryption as well. What this field
+ includes is implementation issue. However, it is
+ RECOMMENDED that it would be random data or, perhaps,
+ a timestamp. It is NOT RECOMMENDED to use zero (0) as an
+ initial vector. This field is not encrypted. This field
+ is not included into the padding calculation. Length
+ of this field equals the cipher's block size. This field
+ is, however, authenticated.
+.in 3
+
+
+.ti 0
+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 starts 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.
+
+The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
+It MUST NOT be sent in any other packet type. The following diagram
+represents the Channel Key Payload.
+
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 14: Channel Key Payload
+
+
+
+.in 6
+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 this key is meant for.
+
+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
+ Channel Key field in the payload, not including any other
+ field.
+
+o Channel Key (variable length) - The actual channel key
+ material.
+.in 3
+
+
+.ti 0
+2.3.11 Private Message Payload
+
+Private Message Payload is used to send private message between
+two clients (or users for that matter). The messages are sent only
+to the specified user and no other user inside SILC network is
+able to see the message. The message is protected by the session
+key established by the SILC Key Exchange Protocol. However,
+it is also possible to agree to use a private key to protect
+just the private messages. See section 2.3.11 Private Message
+Key Payload for detailed description of how to agree to use
+specific key.
+
+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 private key is used to protect the message, servers between
+the sender and the receiver needs not to decrypt/re-encrypt the
+packet. Section Client To Client in [SILC1] gives example of this
+scheme as well.
+
+The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
+packet. It MUST NOT be sent in any other packet type. The following
+diagram represents the Private Message Payload.
+
+
+.in 5
+.nf
+ 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
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Flags | Message Data Length |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Message Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Padding ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 15: Private Message Payload
+
+
+.in 6
+o Flags (2 bytes) - This field includes the flags of the
+ private message. They can indicate a different reason or
+ purpose for the private message. See the section 2.3.9
+ Channel Message Payload for defined flags. Note that
+ the Channel Message Payload use the same flags for the
+ same purpose.
+
+o Message Data Length (2 bytes) - Indicates the length of the
+ Message Data field, not includes any other field.
+
+o Message Data (variable length) - The actual message to
+ the client. Rest of the packet is reserved for the message
+ data.
+
+o Padding (variable length) - This field is present only
+ when the private message payload is encrypted with private
+ message key. In this case the padding is applied to make
+ the payload multiple by eight (8), or by the block size of
+ the cipher, which ever is larger. When encrypted with
+ normal session keys, this field MUST NOT be included.
+.in 3
+
+
+.ti 0
+2.3.12 Private Message Key Payload
+
+This payload is used to send key from client to another client that
+is going to be used to protect the private messages between these
+two clients. If this payload is not sent normal session key
+established by the SILC Key Exchange Protocol is used to protect
+the private messages.
+
+This payload may only be sent by client to another client. Server
+MUST NOT send this payload at any time. After sending this payload
+the sender of private messages must set the Private Message Key
+flag into 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.
+
+
+.in 5
+.nf
+ 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
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Private Message Key Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Private Message Key ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Cipher Name Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Cipher Name ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 16: Private Message Key Payload
+
+
+
+
+.in 6
+o Private Message Key Length (2 bytes) - Indicates the length
+ of the Private Message Key field in the payload, not including
+ any other field.
+
+o Private Message Key (variable length) - The actual private
+ message key material.
+
+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.
+.in 3
+
+
+
+.ti 0
+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.
+
+
+.in 5
+.nf
+ 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 |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 17: Command Payload
+
+
+.in 6
+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
+ used in the field. Value zero (0) in this field means that
+ no specific value is set.
+.in 3
+
+See [SILC4] for detailed description of different SILC commands,
+their arguments and their reply messages.
+
+
+
+
+.ti 0
+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 upper section for the Command 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.
+
+
+.ti 0
+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 MUST 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.
+
+
+.in 5
+.nf
+ 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 |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 18: Connection Auth Request Payload
+
+
+.in 6
+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.
+.in 3
+
+
+.ti 0
+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 uses this payload to inform
+other routers about new server in the SILC network. However, every
+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.
+
+However, 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.
+
+Thus, this payload is very important and used every time when some
+new entity is registered to the SILC network. Client MUST NOT send this
+payload. Both client and server (and router) MAY receive this payload.
+
+The packet uses generic ID Payload as New ID Payload. See section
+2.3.2.1 for generic ID Payload.
+
+
+.ti 0
+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 username sent in this payload.
+However, client should call NICK command after sending this payload to
+set the real nickname of the user which is then used to create new
+client ID.
+
+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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+.in 5
+.nf
+ 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 | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Real Name ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 19: New Client Payload
+
+
+.in 6
+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.
+.in 3
+
+
+.ti 0
+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.
+
+
+
+
+
+.in 5
+.nf
+ 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 | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Server Name ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 20: New Server Payload
+
+
+.in 6
+o Server ID Length (2 bytes) - Length of the Server ID Data
+ field.
+
+o Server ID Data (variable length) - The actual Server ID
+ data.
+
+o Server Name Length (2 bytes) - Length of the server name
+ field.
+
+o Server Name (variable length) - The server name.
+.in 3
+
+
+.ti 0
+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.
+
+The packet uses 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.
+
+
+
+
+.ti 0
+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 key agreement
+is performed outside the SILC network. The server and router MUST NOT
+send this payload.
+
+The sender MAY tell the receiver of this payload the hostname and the
+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.
+
+The payload may only be sent with SILC_PACKET_KEY_AGREEMENT packet.
+It MUST NOT be sent in any other packet type. The following diagram
+represents the Key Agreement Payload.
+
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Port |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 21: Key Agreement Payload
+
+
+.in 6
+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. 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 Port (4 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 32 bit MSB first order value.
+.in 3
+
+
+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] 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.
+
+
+.ti 0
+2.3.21 Cell Routers Payload
+
+Cell Routers payload is used by router to notify its primary router what
+other routers exist in the cell. The other routers are considered to be
+backup routers and one of them will come active only in the case of
+failure of the primary router. Normal server MAY send this packet if it
+is acting as backup router. Client MUST NOT send this packet. To send
+more than one backup router set the List flag and assemble the payloads
+as list.
+
+The payload may only be sent with SILC_PACKET_CELL_ROUTERS packet. It
+MUST NOT be sent in any other packet type. The Following diagram
+represents the Cell Routers Payload.
+
+
+.in 5
+.nf
+ 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Port |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Server ID Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Server ID ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 22: Cell Routers Payload
+
+
+.in 6
+o Hostname Length (2 bytes) - Indicates the length of the Hostname
+ field.
+
+o Hostname (variable length) - The hostname or IP address of
+ the backup router.
+
+o Port (4 bytes) - The port of the backup router it currently uses.
+ This is a 32 bit MSB first order value.
+
+o Server ID Length (2 bytes) - Indicates the length of the Server
+ ID field.
+
+o Server ID (variable length) - Consists of the Server ID of the
+ backup router.
+.in 3
+
+
+.ti 0
+2.4 SILC ID Types
+
+ID's are extensively used in the SILC network to associate different
+entities. The following ID's has been defined to be used in the SILC
+network.
+
+.in 6
+0 No ID
+
+ When ever specific ID cannot be used this is used.
+
+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].
+.in 3
+
+
+.ti 0
+2.5 Packet Encryption And Decryption
+
+SILC packets are encrypted almost entirely. Only small part of SILC
+header is not encrypted as described in section 5.2 SILC Packet Header.
+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.
+
+
+.ti 0
+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 also 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.
+
+Also, note that two bytes of the SILC Packet header are not encrypted
+thus it must be noticed in the decryption process by starting the
+decryption from the second byte of the header. This sets some rules
+to padding generation as well, see the section 2.7 Packet Padding
+Generation.
+
+With out a doubt, this sort of decryption processing causes some
+overhead to packet decryption, but never the less, is required.
+
+
+.ti 0
+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, who ever that might
+be. 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 even 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. 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 above. This
+different processing of channel messages with router to router
+connection is because channel keys are cell specific. All cells has
+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.
+
+
+.ti 0
+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.
+
+The true receiver of the private message, client, that is, is able
+to decrypt the private message as it shares the key with the sender
+of the message.
+
+
+.ti 0
+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, and from the original contents of the packet. The MAC is
+always computed before the packet is encrypted, although after it is
+compressed if compression is used.
+
+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.
+
+If the packet is special packet MAC is computed from the entire packet
+but part of the packet may be encrypted before the MAC is computed.
+This is case, for example, with channel messages where the message data
+is encrypted with key that server may not now. In this case the MAC
+has been computed from the encrypted data.
+
+See [SILC1] for defined and allowed MAC algorithms.
+
+
+.ti 0
+2.7 Packet Padding Generation
+
+Padding is needed in the packet because the packet is encrypted. It
+MUST always 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
+are calculated as follows:
+
+.in 6
+padding length = 16 - ((packet length - 2) mod 16)
+.in 3
+
+The 16 is the maximum padding allowed in SILC packet. Two (2) is
+subtracted from the true length of the packet because two (2) bytes
+is not encrypted in SILC Packet Header, see section 2.2 SILC Packet
+Header. Those two bytes that are not encrypted MUST NOT be calculated
+to the padding length.
+
+For special packets the padding calculation MAY be 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. In this case, as well, two (2) is subtracted from the
+length.
+
+The padding MUST be random data, preferably, generated by
+cryptographically strong random number generator.
+
+
+.ti 0
+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
+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 MUST NOT decompress the packet.
+
+
+.ti 0
+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 compute the MAC of the packet.
+
+Then sender MUST encrypt the packet as has been described in above
+sections according whether the packet is normal packet or special
+packet. The computed MAC MUST NOT be encrypted.
+
+
+.ti 0
+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.
+
+
+.ti 0
+2.11 Packet Routing
+
+Routers are the primary entities in the SILC network that takes care
+of packet routing. However, normal servers routes packets as well, for
+example, when they are routing 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).
+
+For server which receives a packet to be routed to its locally connected
+client the server MUST check whether the particular packet type is
+allowed to be routed to the client. Not all packets may be sent by
+some odd entity to client 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. The section mentions the packets
+that may be sent to indirectly connected entities. It is clear that
+server cannot send, for example, disconnect packet to client that is not
+directly connected to the server.
+
+
+.ti 0
+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.
+
+
+.ti 0
+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.
+
+
+.ti 0
+4 References
+
+[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, April 2001.
+
+[SILC3] Riikonen, P., "SILC Key Exchange and Authentication
+ Protocols", Internet Draft, April 2001.
+
+[SILC4] Riikonen, P., "SILC Commands", Internet Draft, April 2001.
+
+[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.
+
+[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.
+
+
+.ti 0
+5 Author's Address
+
+.nf
+Pekka Riikonen
+Snellmanninkatu 34 A 15
+70100 Kuopio
+Finland
+
+EMail: priikone@silcnet.org
+
+This Internet-Draft expires XXX
projects / silc.git / blobdiff