o Do not allocate new buffer for every packet. Use preallocated
buffer and reallocate only if necessary.
- o Compression routines are missing. The protocol supports packet
- compression thus it must be implemented. SILC Comp API must be
- defined. zlib package is already included into the lib dir (in CVS,
- not in distribution), but it is not used yet, and it requires some
- tweaking on the Makefiles (we want static lib not shared).
-
o All payload parsing (decoding) functions should take unsigned char *
and uint32 as data and data length as arguments. Now some of the
routines do already that but most of the routines use SilcBuffer.
o silc_id_render supports only IPv4 based ID's in the file
lib/silcutil/silcutil.c.
- o Add builtin SOCKS and HTTP Proxy support, well the SOCKS at least.
- SILC currently supports SOCKS4 and SOCKS5 but it needs to be compiled
- in separately.
-
TODO/Bugs in native WIN32 support (libraries)
=============================================
TODO After 1.0
==============
+ o Compression routines are missing. The protocol supports packet
+ compression thus it must be implemented. SILC Comp API must be
+ defined. zlib package is already included into the lib dir (in CVS,
+ not in distribution), but it is not used yet, and it requires some
+ tweaking on the Makefiles (we want static lib not shared).
+
+ o Add builtin SOCKS and HTTP Proxy support, well the SOCKS at least.
+ SILC currently supports SOCKS4 and SOCKS5 but it needs to be compiled
+ in separately.
+
o X.509 certificate support. SILC protocol supports certificates and
it would be great to have support for them. This is a big task as
support has to be made for ASN.1 as well. I've looked into OpenSSL
--- /dev/null
+.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-commands-03.txt XXX
+Expires: XXX
+
+.in 3
+
+.ce 2
+SILC Commands
+<draft-riikonen-silc-commands-03.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 the commands used in the Secure Internet Live
+Conferencing (SILC) protocol, specified in the Secure Internet Live
+Conferencing, Protocol Specification Internet Draft [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.
+
+
+
+
+
+
+
+
+.ti 0
+Table of Contents
+
+.nf
+1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 2
+2 SILC Commands ................................................. 2
+ 2.1 SILC Commands Syntax ...................................... 2
+ 2.2 SILC Commands List ........................................ 4
+ 2.3 SILC Command Status Types ................................. 33
+ 2.3.1 SILC Command Status Payload ......................... 33
+ 2.3.2 SILC Command Status List ............................ 33
+3 Security Considerations ....................................... 38
+4 References .................................................... 38
+5 Author's Address .............................................. 40
+
+
+.ti 0
+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 Internet Draft [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.
+
+
+.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 Commands
+
+.ti 0
+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
+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.
+
+
+
+.in 6
+Example: Arguments: (1) <nickname> (2) <username@host>
+.in 3
+
+
+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:
+.in 6
+
+EXAMPLE_COMMAND
+
+.in 8
+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:
+
+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_TOO_MANY_TARGETS
+ 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 Types.
+
+.in 3
+Every command that has some kind of 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.
+
+
+.ti 0
+2.2 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.
+
+.in 0
+ 0 SILC_COMMAND_NONE
+
+ None. This is reserved command and MUST NOT be sent.
+
+
+ 1 SILC_COMMAND_WHOIS
+
+ Max Arguments: 3328
+ Arguments: (1) [<nickname>[@<server>]] (2) [<count>]
+ (3) [<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
+ int string format.
+
+ 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>. One of the arguments MUST be given.
+ 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.
+
+ 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 specific nickname request.
+
+ The WHOIS request MUST be always sent to the router by 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. 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: 9
+ 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>]
+
+
+ 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 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 may return the list of channel the client has joined.
+ In this case the list is list of Channel Payloads. The Mode Mask
+ in the Channel Payload (see [SILC2] and section 2.3.2.3 for the
+ Channel Payload) is the client's mode on the channel. The list
+ is encoded by adding the Channel Payloads one after the other.
+
+ The server may also send 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 posession of
+ the corresponding private key. Server can do this during the
+ SILC Key Exchange protocol. The <fingerprint> is SHA1 digest.
+
+ 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 in string format.
+
+ 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
+ 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: 3328
+ 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, server 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 in string format.
+
+ It is also possible to search the entity by its ID. If the
+ <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 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.
+
+ 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.
+
+ 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. Nickname MUST NOT include any spaces (` '), non-printable
+ characters, commas (`,') and any wildcard characters. Note that
+ nicknames in SILC are case-sensitive which must be taken into
+ account when searching clients by 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_PACKET_REPLACE_ID to its primary route to replace the old
+ Client ID with the new one.
+
+ Reply messages to the command:
+
+ Max Arguments: 2
+ Arguments: (1) <Status Payload> (2) <New ID Payload>
+
+ This command is replied 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].
+
+ Status messages:
+
+ SILC_STATUS_OK
+ SILC_STATUS_ERR_WILDCARDS
+ 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
+
+
+ 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) [<adding client>] (4) [<removing client>]
+
+ This command is used to invite other clients to join to the
+ channel. The <Client ID> argument is the target client's ID that
+ is being invited. 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 <adding client> and <removing client> can be used to add to
+ and remove from the invite list. The format of the <adding client>
+ and <removing client> is as follows:
+
+ [<nickname>[@<server>]!][<username>]@[<hostname>]
+
+ When adding to or removing from the invite list the server MUST
+ send the notify type SILC_NOTIFY_TYPE_INVITE to its primary router
+ and MUST NOT send it to the client which was added to the list.
+ 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. The wildcards MAY be used with this command. If adding or
+ removing more than one client then the lists are an comma (`,')
+ separated.
+
+ Note that the <Client ID> provided MUST be resolved into correct
+ nickname and host name and add to the invite list before sending
+ the notify packet.
+
+ 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.
+
+ 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. The <invite list> may be omitted if the list was not
+ altered.
+
+ 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
+
+
+ 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: 2
+ Arguments: (1) <Client ID> (2) [<comment>]
+
+ This command is used by SILC operators to remove a client from
+ SILC network. 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.
+
+ 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
+ directly to the client which was killed.
+
+ 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_WILDCARDS
+ 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_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_CONNECT
+
+ Max Arguments: 2
+ Arguments: (1) <remote server/router> (2) [<port>]
+
+ This command is used by operators to force a server to try to
+ establish a new connection to remote server or router. The
+ Operator MUST specify the server/router to be connected by
+ setting <remote server> argument. The port is 32 bit MSB value.
+
+ 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_WILDCARDS
+ SILC_STATUS_ERR_NOT_REGISTERED
+ SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
+ SILC_STATUS_ERR_TOO_MANY_PARAMS
+ SILC_STATUS_ERR_NO_SERVER_PRIV
+ SILC_STATUS_ERR_NO_ROUTER_PRIV
+
+
+ 12 SILC_COMMAND_PING
+
+ 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 or certificate
+ authentication data (data signed with private key). The public
+ key that server will use to verify the signature found in the
+ payload should be verified. It is recommended that the public
+ key is saved locally in the server and server would not use
+ any public keys received during the SKE.
+
+ After changing the mode the 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
+
+
+ 14 SILC_COMMAND_JOIN
+
+ Max Arguments: 5
+ Arguments: (1) <channel> (2) <Client ID>
+ (3) [<passphrase>] (4) [<cipher>]
+ (5) [<hmac>]
+
+ 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.
+
+ The name of the <channel> MUST NOT include any spaces (` '),
+ non-printable characters, commas (`,') or any wildcard characters.
+
+ 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 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 MUST NOT match
+ any active bans.
+
+ o The correct passphrase MUST be provided if passphrase
+ is set to the channel.
+
+ o The user count limit, if set, MUST NOT be reached.
+
+ Reply messages to the command:
+
+ Max Arguments: 14
+ 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>
+
+ 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). If ban mask
+ and/or invite list is set they are sent as well.
+
+ 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.
+
+ 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
+
+
+ 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:
+
+ 0x0000 SILC_UMODE_NONE
+
+ No specific mode for client. This is the initial
+ setting when new client is created. The client is
+ normal client now.
+
+
+ 0x0001 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.
+
+
+ 0x0002 SILC_UMODE_ROUTER_OPERATOR
+
+ Marks the user as router (SILC) operator. Client
+ MUST NOT 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.
+
+
+ 0x0004 SILC_UMODE_GONE
+
+ Marks that the user is not currently present in the
+ SILC Network. Client MAY set and unset this mode.
+
+ 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.
+
+
+ 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: 7
+ Arguments: (1) <Channel ID> (2) <channel mode mask>
+ (3) [<user limit>] (4) [<passphrase>]
+ (5) [<cipher>] (6) [<hmac>]
+ (7) [<auth payload>]
+
+ 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 poses 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:
+
+ 0x0000 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.
+
+
+ 0x0001 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,
+ 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.
+
+ Typical implementation would use [+|-]p on user interface
+ to set/unset this mode.
+
+
+ 0x0002 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.
+
+ Typical implementation would use [+|-]s on user interface
+ to set/unset this mode.
+
+
+ 0x0004 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 is RECOMMENDED to 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.
+
+ Typical implementation would use [+|-]k on user interface
+ to set/unset this mode.
+
+
+ 0x0008 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.
+
+ Typical implementation would use [+|-]i on user interface
+ to set/unset this mode.
+
+
+ 0x0010 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.
+
+ Typical implementation would use [+|-]t on user interface
+ to set/unset this mode.
+
+
+ 0x0020 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.
+
+ Typical implementation would use [+|-]l on user interface
+ to set/unset this mode.
+
+
+ 0x0040 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.
+
+ Typical implementation would use [+|-]a on user interface
+ to set/unset this mode.
+
+
+ 0x0080 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.
+
+ Typical implementation would use [+|-]c on user interface
+ to set/unset this mode.
+
+
+ 0x0100 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.
+
+ Typical implementation would use [+|-]h on user interface
+ to set/unset this mode.
+
+
+ 0x0200 SILC_CMODE_FOUNDER_AUTH
+
+ 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 authentication method and authentication
+ data to be used in the authentication. The server MUST
+ NOT accept NONE authentication method. Also, if the
+ method is public key authentication the server MUST NOT
+ save the authentication data from the payload as the
+ data is different on all authentications. In this case the
+ server only saves the authentication method. However,
+ server MUST verify the sent authentication payload and
+ set the mode only if the verification was successful.
+
+ Note that this mode is effective only in the current server.
+ The client MUST connect to the same server later to be able
+ to regain the channel founder rights. The server MUST save
+ the public key of the channel founder and use that to identify
+ the client which is claiming the channel founder rights.
+ The rights may be claimed by the SILC_CUMODE_FOUNDER
+ channel user mode using SILC_COMMAND_CUMODE command. The
+ set authentication data remains valid as long as the channel
+ exists or until the founder unsets this mode.
+
+ Typical implementation would use [+|-]f on user interface
+ to set/unset this mode.
+
+ 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
+ to the server's primary router.
+
+ Reply messages to the command:
+
+ Max Arguments: 3
+ Arguments: (1) <Status Payload> (2) <Channel ID>
+ (3) <channel mode mask>
+
+ This command replies with the changed channel mode mask that
+ client MUST keep locally.
+
+ 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_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
+ as the target client and poses 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:
+
+ 0x0000 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.
+
+
+ 0x0001 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 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.
+
+
+ 0x0002 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.
+
+ 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
+ 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_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 channel key MUST also be re-generated after kicking, unless
+ the SILC_CMODE_PRIVKEY mode is set.
+
+ 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_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) [<adding client>]
+ (3) [<removing client>]
+
+ 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 <adding client> and <removing client> are used to add to and
+ remove from the ban list. The format of the <adding client> and
+ the <removing client> is of following format:
+
+ [<nickname>[@<server>]!][<username>]@[<hostname>]
+
+ 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 adding or removing
+ from than one clients then the lists are an comma (`,') separated.
+
+ 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
+
+
+ 21 SILC_COMMAND_CLOSE
+
+ Max Arguments: 2
+ Arguments: (1) <remote server/router> (2) [<port>]
+
+ This command is used only by operator to close connection to a
+ remote site.
+
+ 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_NO_SUCH_SERVER
+ SILC_STATUS_ERR_NO_SERVER_PRIV
+ SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+
+
+ 22 SILC_COMMAND_SHUTDOWN
+
+ Max Arguments: 0
+ Arguments: None
+
+ This command is used only by operator to shutdown the server.
+ All connections to the server will be closed and the server is
+ shutdown.
+
+ 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_REGISTERED
+ SILC_STATUS_ERR_NO_SERVER_PRIV
+
+
+ 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
+ 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:
+
+ Max Arguments: 1
+ Arguments: (1) <Status Payload>
+
+ This command replies only with Status 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_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 user names and send a comma (`,') separated list of user names
+ on the channel. Server or router MAY resolve the names by sending
+ SILC_COMMAND_WHOIS or SILC_COMMAND_IDENTIFY commands.
+
+ If the requested channel is a private or secret channel, this
+ command MUST NOT send the list of users, as private and secret
+ channels cannot be seen by outside. In this case the returned
+ name list MAY include a indication that the server could not
+ resolve the names of the users on the channel. Also, in this case
+ Client ID's or client modes are not sent either.
+
+ 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.
+
+ 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 - 199
+
+ 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.
+.in 3
+
+
+.ti 0
+2.3 SILC Command Status Types
+
+.ti 0
+2.3.1 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 of length. The following diagram
+represents the Command Status Payload (field is always in MSB order).
+
+
+.in 21
+.nf
+ 1
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Status Message |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 6: SILC Command Status Payload
+
+
+.in 6
+o Status Message (2 bytes) - Indicates the status message.
+ All Status messages are described in the next section.
+.in 3
+
+
+.ti 0
+2.3.2 SILC Command Status List
+
+Command Status messages are returned in the command reply messages
+to indicate whether the command were executed without errors. If error
+has occurred the status indicates which error occurred. Status payload
+only sends numeric reply about the status. Receiver of the payload must
+convert the numeric values into human readable error messages. The
+list of status messages below has an example human readable error
+messages that client may display for the user.
+
+List of all defined command status messages following.
+
+.in 0
+ 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.
+
+ 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL
+
+ "No such channel". Requested channel name does not exist.
+
+ 12 SILC_STATUS_ERR_NO_SUCH_SERVER
+
+ "No such server". Requested server name does not exist.
+
+ 13 SILC_STATUS_ERR_TOO_MANY_TARGETS
+
+ "Duplicate recipients. No message delivered". Message were
+ tried to be sent to recipient which has several occurrences in
+ the recipient list.
+
+ 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.
+
+ 21 SILC_STATUS_ERR_BAD_CHANNEL_ID
+
+ "Bad Channel ID". Channel ID provided were erroneous.
+
+ 22 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
+
+ "No such Client ID". Client ID provided does not exist.
+
+ 23 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
+
+ "No such Channel ID". Channel ID provided does not exist.
+
+ 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.
+
+ 26 SILC_STATUS_ERR_USER_NOT_ON_CHANNEL
+
+ "They are not on channel". The requested target client is not
+ on requested channel.
+
+ 27 SILC_STATUS_ERR_USER_ON_CHANNEL
+
+ "User already on channel". User were invited on channel they
+ already are on.
+
+ 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.
+
+ 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.
+
+ 34 SILC_STATUS_ERR_CHANNEL_IS_FULL
+
+ "Cannot join channel. Channel is full". The channel is full
+ and client cannot be joined to it.
+
+ 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.
+
+ 36 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
+
+ "Cannot join channel. You have been banned". The client has
+ been banned from the channel.
+
+ 37 SILC_STATUS_ERR_UNKNOWN_MODE
+
+ "Unknown mode". Mode provided by the client were unknown to
+ the server.
+
+ 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.
+
+ 40 SILC_STATUS_ERR_NO_CHANNEL_FOPRIV
+
+ "Permission denied. You are not channel founder". Command may
+ be executed only by channel operator.
+
+ 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.
+
+ 47 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
+
+ "No such Server ID". Server ID provided does not exist.
+
+.in 3
+
+
+.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.
+
+[SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
+ April 2001.
+
+[SILC3] Riikonen, P., "SILC Key Exchange and Authentication
+ Protocols", 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
+
--- /dev/null
+.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-ke-auth-05.txt XXX
+Expires: XXX
+
+.in 3
+
+.ce 2
+SILC Key Exchange and Authentication Protocols
+<draft-riikonen-silc-ke-auth-05.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 two protocols used in the Secure Internet Live
+Conferencing (SILC) protocol, specified in the Secure Internet Live
+Conferencing, Protocol Specification internet-draft [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. SKE uses best parts
+of the SSH2 Key Exchange protocol, Station-To-Station (STS) protocol
+and the OAKLEY Key Determination protocol [OAKLEY].
+
+The SILC Connection Authentication protocol provides user level
+authentication used when creating connections in SILC network. The
+protocol is transparent to the authentication data which means that it
+can be used to authenticate the user with, for example, passphrase
+(pre-shared-secret) or public key (and certificate).
+
+
+
+.ti 0
+Table of Contents
+
+.nf
+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 ................................ 8
+ 2.2 Key Exchange Procedure .................................... 10
+ 2.3 Processing the Key Material ............................... 12
+ 2.4 SILC Key Exchange Groups .................................. 13
+ 2.4.1 diffie-hellman-group1 ............................... 14
+ 2.4.2 diffie-hellman-group2 ............................... 14
+ 2.5 Key Exchange Status Types ................................. 15
+3 SILC Connection Authentication Protocol ....................... 16
+ 3.1 Connection Auth Payload ................................... 18
+ 3.2 Connection Authentication Types ........................... 19
+ 3.2.1 Passphrase Authentication ........................... 19
+ 3.2.2 Public Key Authentication ........................... 19
+ 3.3 Connection Authentication Status Types .................... 20
+4 Security Considerations ....................................... 20
+5 References .................................................... 20
+6 Author's Address .............................................. 22
+
+
+.ti 0
+List of Figures
+
+.nf
+Figure 1: Key Exchange Start Payload
+Figure 2: Key Exchange Payload
+Figure 3: Connection Auth Payload
+
+
+.ti 0
+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 Internet-Draft [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. SKE uses best parts
+of the SSH2 Key Exchange protocol, Station-To-Station (STS) protocol
+and the OAKLEY Key Determination protocol.
+
+The SILC Connection Authentication protocol provides user level
+authentication used when creating connections in SILC network. The
+protocol is transparent to the authentication data which means that it
+can be used to authenticate the user with, for example, pass phrase
+(pre-shared- secret) or public key (and certificate).
+
+The basis of secure SILC session requires strong and secure key exchange
+protocol and authentication. The authentication protocol is entirely
+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 refers constantly to other SILC protocol specification
+Internet Drafts that are a must read for those who wants to understand
+the function of these protocols. The most important references are
+the Secure Internet Live Conferencing, Protocol Specification [SILC1]
+and the SILC Packet Protocol [SILC2] Internet Drafts.
+
+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.
+
+
+.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 Key Exchange Protocol
+
+SILC Key Exchange Protocol (SKE) is used to exchange shared secret
+between connecting entities. The result of this protocol is a key
+material used to secure the communication channel. The protocol uses
+Diffie-Hellman key exchange algorithm and its functionality is derived
+from several key exchange protocols. SKE uses best parts of the SSH2
+Key Exchange protocol, Station-To-Station (STS) protocol and the OAKLEY
+Key Determination protocol. The protocol does not claim any conformance
+to any of these protocols, they were merely used as a reference when
+designing this protocol.
+
+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 like commands, command replies and other
+communication between two entities. If connection is server to router
+connection, the keys are used to protect all traffic between those
+servers. In client connections usually all the packets are protected
+with this key except channel messages; channels has their own keys and
+they are not exchanged with this protocol.
+
+The Diffie-Hellman implementation used in the SILC SHOULD be compliant
+to the PKCS #3.
+
+
+.ti 0
+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 start of
+all packets. The same is done with these payloads as well. All the
+fields in the payloads are always in MSB (most significant byte first)
+order. Following descriptions of these payloads.
+
+
+.ti 0
+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 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 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 spaces (` ').
+
+
+.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
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| 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 ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Compression Alg Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Compression Algorithms ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 1: Key Exchange Start Payload
+
+
+
+.in 6
+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.
+
+ No Reply 0x01
+
+ If set the receiver of the payload does not reply to
+ the packet.
+
+ 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.
+ 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
+ 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.
+
+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 of the version
+ string format.
+
+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.
+
+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.
+
+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.
+
+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.
+
+o HMAC Length (2 bytes) - The length of the HMAC list, not
+ including any other field.
+
+o HMACs (variable length) - The list of HMACs. The HMAC's
+ are used to compute the Message Authentication Codes (MAC)
+ of the SILC packets.
+
+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.
+.in 3
+
+
+.ti 0
+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 public key authentication (it
+is based on passphrase) then the Mutual Authentication flag SHOULD be
+enabled. This way the connecting entity has to provide proof of
+posession of the private key for the public key it will provide in
+SILC Key Exchange 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.
+
+
+.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) ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Public Data Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Public Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Signature Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Signature Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 2: Key Exchange 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. 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
+ SSH 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.
+
+o Public Key (or certificate) (variable length) - The
+ public key or certificate.
+
+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. See section 2.2 Key Exchange
+ Procedure for detailed description how this field is
+ computed. This value is binary encoded.
+
+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
+ MUST always provide this field.
+.in 3
+
+
+.ti 0
+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,
+ 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(Key Exchange Start Payload | public key
+ (or certificate) | e). 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(Key Exchange Start Payload data | 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).
+
+ 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 will start using the new keys.
+
+
+.ti 0
+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:
+
+.in 6
+Sending Initial Vector (IV) = hash(0 | KEY | HASH)
+Receiving Initial Vector (IV) = hash(1 | KEY | HASH)
+Sending Encryption Key = hash(2 | KEY | HASH)
+Receiving Encryption Key = hash(3 | KEY | HASH)
+Sending HMAC Key = hash(4 | KEY | HASH)
+Receiving HMAC Key = hash(5 | KEY | HASH)
+.in 3
+
+
+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
+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:
+
+.in 6
+K1 = hash(2 | KEY | HASH)
+K2 = hash(KEY | HASH | K1)
+K3 = hash(KEY | HASH | K1 | K2) ...
+
+Sending Encryption Key = K1 | K2 | K3 ...
+
+
+K1 = hash(3 | KEY | HASH)
+K2 = hash(KEY | HASH | K1)
+K3 = hash(KEY | HASH | K1 | K2) ...
+
+Receiving Encryption Key = K1 | K2 | K3 ...
+.in 3
+
+
+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.
+
+This same procedure is used in the SILC in some other circumstances
+as well. Any changes to this procedure is mentioned separately when
+this procedure is needed. See the [SILC1] and the [SILC2] for these
+circumstances.
+
+
+.ti 0
+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).
+
+
+.ti 0
+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 decimal value is
+
+.in 6
+179769313486231590770839156793787453197860296048756011706444
+423684197180216158519368947833795864925541502180565485980503
+646440548199239100050792877003355816639229553136239076508735
+759914822574862575007425302077447712589550957937778424442426
+617334727629299387668709205606050270810842907692932019128194
+467627007
+.in 3
+
+Its hexadecimal value is
+
+.in 6
+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
+.in 3
+
+
+The generator used with this prime is g = 2. The group order q is
+(p - 1) / 2.
+
+This group was taken from the OAKLEY specification.
+
+
+.ti 0
+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 decimal value is
+
+.in 6
+241031242692103258855207602219756607485695054850245994265411
+694195810883168261222889009385826134161467322714147790401219
+650364895705058263194273070680500922306273474534107340669624
+601458936165977404102716924945320037872943417032584377865919
+814376319377685986952408894019557734611984354530154704374720
+774996976375008430892633929555996888245787241299381012913029
+459299994792636526405928464720973038494721168143446471443848
+8520940127459844288859336526896320919633919
+.in 3
+
+Its hexadecimal value is
+
+.in 6
+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
+.in 3
+
+The generator used with this prime is g = 2. The group order q is
+(p - 1) / 2.
+
+This group was taken from the OAKLEY specification.
+
+
+.ti 0
+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:
+
+.in 6
+0 SILC_SKE_STATUS_OK
+
+ Protocol were executed successfully.
+
+
+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.
+
+11 SILC_SKE_STATUS_INVALID_COOKIE
+
+ The cookie in the Key Exchange Start Payload was malformed,
+ because responder modified the cookie.
+.in 3
+
+
+.ti 0
+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 connection this
+is. The type defines whether this is client, server or router
+connection. Server uses this information to create the ID for the
+connection.
+
+After the authentication protocol has been successfully completed
+SILC_PACKET_NEW_ID must be sent to the connecting client by the server.
+See the [SILC1] for the details of the connecting procedure.
+
+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 everything checks out fine 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 at all. However, in this case the protocol still MUST be
+executed; the authentication data just is empty indicating no
+authentication is required.
+
+If authentication method is passphrase the authentication data is
+plaintext passphrase. As the payload is entirely encrypted it is safe
+to have plaintext passphrase. See the section 3.2.1 Passphrase
+Authentication for more information.
+
+If authentication method is public key authentication the authentication
+data is a signature of the hash value of hash HASH plus 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.
+
+The connecting client of this protocol MUST wait after successful execution
+of this protocol for the SILC_PACKET_NEW_ID packet where it will receive
+the ID it will be using in the SILC network. The connecting client cannot
+start normal SILC session (sending messages or commands) until it has
+received its ID. The ID's are always created by the server except
+for server to router connection where servers create their own ID's.
+
+
+.ti 0
+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.
+
+
+.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 | Connection Type |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Authentication Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 3: Connection Auth Payload
+
+
+.in 6
+o Payload Length (2 bytes) - Length of the entire Connection
+ 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.
+.in 3
+
+
+
+
+.ti 0
+3.2 Connection Authentication Types
+
+SILC supports two authentication types to be used in the connection
+authentication protocol; passphrase or public key based authentication.
+The following sections defines the authentication methods. See [SILC2]
+for defined numerical authentication method types.
+
+
+.ti 0
+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.
+
+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.
+
+
+.ti 0
+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
+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.
+
+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.
+
+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.
+
+
+.ti 0
+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.
+
+
+1 SILC_AUTH_FAILED
+
+ Authentication failed.
+
+
+.ti 0
+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.
+
+
+.ti 0
+5 References
+
+[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
+ Protocol Specification", Internet Draft, April 2001.
+
+[SILC2] Riikonen, P., "SILC Packet Protocol", 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
+6 Author's Address
+
+.nf
+Pekka Riikonen
+Snellmanninkatu 34 A 15
+70100 Kuopio
+Finland
+
+EMail: priikone@silcnet.org
+
+This Internet-Draft expires XXX
--- /dev/null
+.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-05.txt XXX
+Expires: XXX
+
+.in 3
+
+.ce 2
+SILC Packet Protocol
+<draft-riikonen-silc-pp-05.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 .................................. 17
+ 2.3.2.2 Argument Payload ............................ 18
+ 2.3.2.3 Channel Payload ............................. 18
+ 2.3.2.4 Public Key Payload .......................... 19
+ 2.3.3 Disconnect Payload .................................. 20
+ 2.3.4 Success Payload ..................................... 21
+ 2.3.5 Failure Payload ..................................... 21
+ 2.3.6 Reject Payload ...................................... 22
+ 2.3.7 Notify Payload ...................................... 22
+ 2.3.8 Error Payload ....................................... 28
+ 2.3.9 Channel Message Payload ............................. 29
+ 2.3.10 Channel Key Payload ................................ 32
+ 2.3.11 Private Message Payload ............................ 34
+ 2.3.12 Private Message Key Payload ........................ 35
+ 2.3.13 Command Payload .................................... 37
+ 2.3.14 Command Reply Payload .............................. 38
+ 2.3.15 Connection Auth Request Payload .................... 38
+ 2.3.16 New ID Payload ..................................... 39
+ 2.3.17 New Client Payload ................................. 40
+ 2.3.18 New Server Payload ................................. 41
+ 2.3.19 New Channel Payload ................................ 42
+ 2.3.20 Key Agreement Payload .............................. 43
+ 2.3.21 Resume Router Payload .............................. 44
+ 2.3.22 File Transfer Payload .............................. 44
+ 2.4 SILC ID Types ............................................. 46
+ 2.5 Packet Encryption And Decryption .......................... 46
+ 2.5.1 Normal Packet Encryption And Decryption ............. 46
+ 2.5.2 Channel Message Encryption And Decryption ........... 47
+ 2.5.3 Private Message Encryption And Decryption ........... 48
+ 2.6 Packet MAC Generation ..................................... 48
+ 2.7 Packet Padding Generation ................................. 49
+ 2.8 Packet Compression ........................................ 50
+ 2.9 Packet Sending ............................................ 50
+ 2.10 Packet Reception ......................................... 51
+ 2.11 Packet Routing ........................................... 51
+ 2.12 Packet Broadcasting ...................................... 52
+3 Security Considerations ....................................... 53
+4 References .................................................... 53
+5 Author's Address .............................................. 54
+
+.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: Resume Router Payload
+Figure 23: File Transfer 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. 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.
+
+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. See more details in the section 2.6 Packet MAC Generation.
+
+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.
+
+.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 |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Pad Length | RESERVED | Source ID Len | Dest ID Len |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| 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.
+
+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 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
+ 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_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
+ stream is always protected with the SILC packet.
+
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
+ Payload of the packet: See section 2.3.22 File Transfer Payload
+
+
+ 28 - 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.
+
+.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. 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 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. 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 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.
+
+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.
+
+
+.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 Resume Router Payload
+
+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.
+
+
+.in 5
+.nf
+ 1
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Type | Session ID |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 22: Resume Router Payload
+
+
+.in 6
+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.
+.in 3
+
+
+.ti 0
+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 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
+
+.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
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Type | |
++-+-+-+-+-+-+-+-+ +
+| |
+~ Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 23: File Transfer Payload
+
+
+.in 6
+o Type (1 byte) - Indicates the type of the file transfer
+ protocol. The following file transfer protocols has been
+ defined:
+
+ 1 SSH 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.
+.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
+
+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.
+
+
+.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.
+
+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 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.
+
+
+.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, from packet sequence number, 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.
+
+Hence, packet's MAC generation is as follows:
+
+ mac = MAC(key, sequence number | 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. Note
+that the sequence number is incremented only 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 first encrypted packet.
+
+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
+may be calculated as follows:
+
+.in 6
+padding length = 16 - (packet_length mod block_size)
+.in 3
+
+The `block_size' is the block size of the cipher. The maximum padding
+length is 128 bytes, and minimum is 1 byte. The above algorithm calculates
+the padding to the next block size, and always returns the padding
+length between 1 - 16 bytes. However, implementations may add padding
+up to 128 bytes. For example packets that include a passphrase or a
+password for authentication purposes SHOULD pad the packet up to the
+maximum padding length.
+
+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.
+
+
+.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).
+
+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, preferrably
+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 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.
+
+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 counter clock-wise direction,
+or if it cannot be used then always 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.
+
+
+.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.
+
+[SFTP] Ylonen T., and Lehtinen S., "Secure Shell File Transfer
+ Protocol", Internet Draft, March 2001.
+
+.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
--- /dev/null
+.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-spec-05.txt XXX
+Expires: XXX
+
+.in 3
+
+.ce 3
+Secure Internet Live Conferencing (SILC),
+Protocol Specification
+<draft-riikonen-silc-spec-05.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 Secure Internet Live Conferencing (SILC)
+protocol which provides secure conferencing services over insecure
+network channel. SILC is IRC [IRC] like protocol, however, it is
+not equivalent to IRC and does not support IRC. Strong cryptographic
+methods are used to protect SILC packets inside the SILC network.
+Three other Internet Drafts relates very closely to this memo;
+SILC Packet Protocol [SILC2], SILC Key Exchange and Authentication
+Protocols [SILC3] and SILC Commands [SILC4].
+
+
+
+
+
+
+.ti 0
+Table of Contents
+
+.nf
+1 Introduction .................................................. 3
+ 1.1 Requirements Terminology .................................. 4
+2 SILC Concepts ................................................. 4
+ 2.1 SILC Network Topology ..................................... 4
+ 2.2 Communication Inside a Cell ............................... 5
+ 2.3 Communication in the Network .............................. 6
+ 2.4 Channel Communication ..................................... 7
+ 2.5 Router Connections ........................................ 7
+3 SILC Specification ............................................ 8
+ 3.1 Client .................................................... 8
+ 3.1.1 Client ID ........................................... 9
+ 3.2 Server .................................................... 10
+ 3.2.1 Server's Local ID List .............................. 10
+ 3.2.2 Server ID ........................................... 11
+ 3.2.3 SILC Server Ports ................................... 12
+ 3.3 Router .................................................... 12
+ 3.3.1 Router's Local ID List .............................. 12
+ 3.3.2 Router's Global ID List ............................. 13
+ 3.3.3 Router's Server ID .................................. 14
+ 3.4 Channels .................................................. 14
+ 3.4.1 Channel ID .......................................... 16
+ 3.5 Operators ................................................. 16
+ 3.6 SILC Commands ............................................. 16
+ 3.7 SILC Packets .............................................. 17
+ 3.8 Packet Encryption ......................................... 17
+ 3.8.1 Determination of the Source and the Destination ..... 17
+ 3.8.2 Client To Client .................................... 18
+ 3.8.3 Client To Channel ................................... 19
+ 3.8.4 Server To Server .................................... 20
+ 3.9 Key Exchange And Authentication ........................... 20
+ 3.9.1 Authentication Payload .............................. 20
+ 3.10 Algorithms ............................................... 22
+ 3.10.1 Ciphers ............................................ 22
+ 3.10.2 Public Key Algorithms .............................. 23
+ 3.10.3 Hash Functions ..................................... 24
+ 3.10.4 MAC Algorithms ..................................... 24
+ 3.10.5 Compression Algorithms ............................. 25
+ 3.11 SILC Public Key .......................................... 25
+ 3.12 SILC Version Detection ................................... 27
+ 3.13 Backup Routers ........................................... 28
+ 3.13.1 Switching to Backup Router ......................... 29
+ 3.13.2 Resuming Primary Router ............................ 30
+ 3.13.3 Discussion on Backup Router Scheme ................. 32
+4 SILC Procedures ............................................... 33
+ 4.1 Creating Client Connection ................................ 33
+ 4.2 Creating Server Connection ................................ 34
+ 4.2.1 Announcing Clients, Channels and Servers ............ 35
+ 4.3 Joining to a Channel ...................................... 36
+ 4.4 Channel Key Generation .................................... 37
+ 4.5 Private Message Sending and Reception ..................... 38
+ 4.6 Private Message Key Generation ............................ 38
+ 4.7 Channel Message Sending and Reception ..................... 39
+ 4.8 Session Key Regeneration .................................. 39
+ 4.9 Command Sending and Reception ............................. 40
+ 4.10 Closing Connection ....................................... 41
+5 Security Considerations ....................................... 41
+6 References .................................................... 42
+7 Author's Address .............................................. 44
+
+
+
+.ti 0
+List of Figures
+
+.nf
+Figure 1: SILC Network Topology
+Figure 2: Communication Inside cell
+Figure 3: Communication Between Cells
+Figure 4: Router Connections
+Figure 5: SILC Public Key
+
+
+.ti 0
+1. Introduction
+
+This document describes a Secure Internet Live Conferencing (SILC)
+protocol which provides secure conferencing services over insecure
+network channel. SILC is IRC [IRC] like protocol, however, it is
+not equivalent to IRC and does not support IRC.
+
+Strong cryptographic methods are used to protect SILC packets inside
+the SILC network. Three other Internet Drafts 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 security of SILC protocol, and for any security protocol for that
+matter, is 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 TCP/IP network
+protocol, although it could be made to work on other network protocols
+with only minor changes. However, it is recommended that TCP/IP
+protocol is used under SILC protocol. Typical implementation would
+be made in client-server model.
+
+
+.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 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 routers and servers 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.
+
+
+.ti 0
+2.1 SILC Network Topology
+
+SILC network is a cellular network as opposed to tree style network
+topology. 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 routers.
+
+A difference between normal server and router server is that routers
+knows everything about everything in the network. They also do the
+actual routing of the messages to the correct receiver. Normal servers
+knows only about local information and nothing about global information.
+This makes the network faster as there are less servers that needs to
+keep global information up to date at all time.
+
+This, on the other hand, leads to 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.
+
+.in 8
+.nf
+ ---- ---- ---- ---- ---- ----
+ | 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.
+.in 3
+
+.ce
+Figure 1: SILC Network Topology
+
+
+A cell is formed when a server or servers connect to one router. In
+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 normal SILC
+server; clients may connect to it the same way as to normal SILC
+server. 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.
+
+There are many issues in this network topology that needs to be careful
+about. Issues like 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.
+
+
+.ti 0
+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:
+
+
+.in 25
+.nf
+1 --- S1 S4 --- 5
+ S/R
+ 2 -- S2 S3
+ / |
+ 4 3
+.in 3
+
+
+.ce
+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
+ 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.
+
+
+.ti 0
+2.3 Communication in the Network
+
+If the message is destined to server that does not belong to local cell
+the message is routed to the router server to which the destination
+server 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.
+
+
+.in 16
+.nf
+1 --- S1 S4 --- 5 S2 --- 1
+ S/R - - - - - - - - S/R
+ 2 -- S2 S3 S1
+ / | \\
+ 4 3 2
+
+ Cell 1. Cell 2.
+.in 3
+
+
+.ce
+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.
+
+
+.ti 0
+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.
+
+
+.ti 0
+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:
+
+
+.in 16
+.nf
+ S/R1 - > - > - > - > - > - > - S/R2
+ \\ /
+ ^ v
+ \\ - < - < - S/R3 - < - < - /
+.in 3
+
+
+.ce
+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. 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
+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 cause interesting
+routing problems. The [SILC2] discusses the routing of packets in this
+sort of network in more detail.
+
+
+.ti 0
+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.
+
+
+.ti 0
+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 nickname selected by the user. User uses logical nicknames
+in communication which are then mapped to the corresponding Client ID.
+Client ID's are low level identifications and must 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 causes the server names or client's host names
+to be used along with the nicknames 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. The maximum length of nickname is 128 characters.
+
+
+.ti 0
+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 ID's,
+and ID's based on IPv6 addresses extends this to 2^224 different Client
+ID's. Collisions are not expected to happen. The Client ID is defined
+as follows.
+
+
+
+.in 6
+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 to the client has 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 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.
+
+.in 3
+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 problems if it would occur. Nicknames are usually logical and
+it is unlikely to have two distinct logical nicknames produce same
+truncated hash value.
+
+
+.ti 0
+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.
+
+
+.ti 0
+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 ID's, 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 don't have to worry about global clients. Server is also responsible
+of creating the Client ID's for their clients.
+
+Normal server also keeps information about locally created channels and
+their Channel ID's.
+
+
+Hence, local list for normal server includes:
+
+.in 6
+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
+ 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 ID's on channel
+ o Client ID modes on channel
+ o Channel key
+.in 3
+
+
+.ti 0
+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 ID's also provide
+information for Client ID's, see section 3.1.1 Client ID. Server ID is
+defined as follows.
+
+.in 6
+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.
+
+.in 3
+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.
+
+
+.ti 0
+3.2.3 SILC Server Ports
+
+The following ports has been assigned by IANA for the SILC protocol:
+
+.in 10
+silc 706/tcp SILC
+silc 706/udp SILC
+.in 3
+
+
+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.
+
+
+.ti 0
+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
+is also a normal server thus clients may connect to it as it would be
+just normal SILC server.
+
+However, router servers has a lot of important tasks that normal servers
+do not have. Router server knows everything about everything in the SILC.
+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. And, this
+is what they must do.
+
+
+.ti 0
+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:
+
+.in 6
+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
+
+
+channel list - All channels in the cell
+ o Channel ID
+ o Client ID's on channel
+ o Client ID modes on channel
+ o Channel key
+.in 3
+
+
+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.
+
+
+.ti 0
+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 ID's, all created channels
+and their Channel ID's and all servers and routers on SILC and their
+Server ID's. 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:
+
+.in 6
+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 ID's on channel
+ o Client ID modes on channel
+.in 3
+
+
+
+.ti 0
+3.3.3 Router's Server ID
+
+Router's Server ID's are equivalent to normal Server ID's. As routers
+are normal servers as well same types of ID's applies for routers as well.
+Thus, see section 3.2.2 Server ID.
+
+
+.ti 0
+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 name of 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. The Channel name is a string of
+maximum length of 256 characters. Channel names MUST NOT contain any
+spaces (` '), any non-printable ASCII characters, commas (`,') and
+wildcard characters.
+
+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.
+
+.in 6
+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 administrate the
+ 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.
+.in 3
+
+
+.ti 0
+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.
+
+.in 6
+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
+
+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
+
+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 router knows
+ 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 - To further randomize the Channel ID. This makes
+ sure that there are no collisions. This also means that
+ in a cell there can be 2^16 channels.
+.in 3
+
+
+.ti 0
+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
+channel, to gain access to the contents of a 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 everyone else except they are able to administrate
+their server or router.
+
+
+.ti 0
+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. However, server MUST NOT send commands
+to client and there are some commands that server must not send.
+
+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 miss-used 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 miss-use of commands.
+
+SILC commands are described in [SILC4].
+
+
+.ti 0
+3.7 SILC Packets
+
+Packets are naturally the most important part of the protocol and the
+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 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.
+
+
+.ti 0
+3.8 Packet Encryption
+
+All packets passed in SILC network MUST be encrypted. This section
+defines 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 has their own 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 has 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 before hand to be able to talk on the
+channel. In this case, no server or router know the key for 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 route. However, every packet passed
+from router to other router, including packets for channels, are
+encrypted with the shared session key. Every router connection has
+their own session keys.
+
+
+.ti 0
+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 who is next 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 ID's attached to the header. The ID's 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 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. However, the header and the packet may be encrypted
+with same key. This is the case, for example, with command packets.
+
+
+.ti 0
+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
+ 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 has established 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 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.
+
+o Router determines the destination of the packet and sends the
+ packet to the server.
+
+o Server determines the client to which the packet is destined
+ to and sends the packet to the client.
+
+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 packet.
+
+The process for clients on same server is much simpler as there are
+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.
+
+
+.ti 0
+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.
+
+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 the packet.
+
+
+.ti 0
+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].
+
+
+.ti 0
+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 router connects 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, usually clients are accepted
+to connect to server without explicit authentication. Servers are
+required use authentication protocol when connecting. The authentication
+may be based on passphrase (pre-shared-secret) or public key. The
+connection authentication protocol is described in detail in [SILC3].
+
+
+.ti 0
+3.9.1 Authentication Payload
+
+Authentication payload is used separately from the SKE and the Connection
+Authentication protocol. It is used during the session to authenticate
+with the remote. For example, the client can authenticate itself to the
+server to become server operator. In this case, Authentication Payload is
+used.
+
+The format of the Authentication Payload is as follows:
+
+
+.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 | Authentication Method |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Public Data Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Public Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Authentication Data Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Authentication Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 5: Authentication Payload
+
+
+.in 6
+o Payload Length (2 bytes) - Length of the entire payload.
+
+o Authentication Method (2) - 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
+ this field MAY include a 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.
+
+o Authentication Data (variable length) - Authentication
+ method dependent authentication data.
+.in 3
+
+
+If the authentication method is password based, the Authentication
+Data field includes the plaintext password. It is safe to send
+plaintext password 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 password based
+authentication. This way it is not possible to approximate the length
+of the password 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. 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 is raw ID data. 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. In this case also, the entire
+payload is encrypted.
+
+
+.ti 0
+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.
+
+
+.ti 0
+3.10.1 Ciphers
+
+Cipher is the encryption algorithm that is used to protect the data
+in the SILC packets. See [SILC2] of 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:
+
+.in 6
+aes-256-cbc AES in CBC mode, 256 bit key (REQUIRED)
+aes-192-cbc AES in CBC mode, 192 bit key (OPTIONAL)
+aes-128-cbc AES in CBC mode, 128 bit key (OPTIONAL)
+twofish-256-cbc Twofish in CBC mode, 256 bit key (OPTIONAL)
+twofish-192-cbc Twofish in CBC mode, 192 bit key (OPTIONAL)
+twofish-128-cbc Twofish in CBC mode, 128 bit key (OPTIONAL)
+blowfish-128-cbc Blowfish in CBC mode, 128 bit key (OPTIONAL)
+cast-256-cbc CAST-256 in CBC mode, 256 bit key (OPTIONAL)
+cast-192-cbc CAST-256 in CBC mode, 192 bit key (OPTIONAL)
+cast-128-cbc CAST-256 in CBC mode, 128 bit key (OPTIONAL)
+rc6-256-cbc RC6 in CBC mode, 256 bit key (OPTIONAL)
+rc6-192-cbc RC6 in CBC mode, 192 bit key (OPTIONAL)
+rc6-128-cbc RC6 in CBC mode, 128 bit key (OPTIONAL)
+mars-256-cbc Mars in CBC mode, 256 bit key (OPTIONAL)
+mars-192-cbc Mars in CBC mode, 192 bit key (OPTIONAL)
+mars-128-cbc Mars in CBC mode, 128 bit key (OPTIONAL)
+none No encryption (OPTIONAL)
+.in 3
+
+
+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 algorithms except in special
+debugging mode.
+
+Additional ciphers MAY be defined to be used in SILC by using the
+same name format as above.
+
+
+.ti 0
+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:
+
+.in 6
+rsa RSA (REQUIRED)
+dss DSS (OPTIONAL)
+.in 3
+
+DSS is described in [Menezes]. The RSA MUST be implemented according
+PKCS #1 [PKCS1]. The mandatory PKCS #1 implementation in SILC MUST be
+compliant to either PKCS #1 version 1.5 or newer with the following
+notes: The signature encoding is always in same format as the encryption
+encoding regardless of the PKCS #1 version. The signature with appendix
+(with hash algorithm OID in the data) MUST NOT be used in the SILC. The
+rationale for this is that there is no binding between the PKCS #1 OIDs
+and the hash algorithms used in the SILC protocol. Hence, the encoding
+is always in PKCS #1 version 1.5 format.
+
+Additional public key algorithms MAY be defined to be used in SILC.
+
+
+.ti 0
+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:
+
+.in 6
+sha1 SHA-1, length = 20 (REQUIRED)
+md5 MD5, length = 16 (OPTIONAL)
+.in 3
+
+
+.ti 0
+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.
+
+The following MAC algorithms are defined in SILC protocol:
+
+.in 6
+hmac-sha1-96 HMAC-SHA1, length = 12 (REQUIRED)
+hmac-md5-96 HMAC-MD5, length = 12 (OPTIONAL)
+hmac-sha1 HMAC-SHA1, length = 20 (OPTIONAL)
+hmac-md5 HMAC-MD5, length = 16 (OPTIONAL)
+none No MAC (OPTIONAL)
+.in 3
+
+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] and hash algorithms that
+are used as part of the HMACs are described in [Scheneir] and in
+[Menezes]
+
+Additional MAC algorithms MAY be defined to be used in SILC.
+
+
+
+
+.ti 0
+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:
+
+.in 6
+none No compression (REQUIRED)
+zlib GNU ZLIB (LZ77) compression (OPTIONAL)
+.in 3
+
+Additional compression algorithms MAY be defined to be used in SILC.
+
+
+.ti 0
+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:
+
+
+.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 |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Algorithm Name Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Algorithm Name ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| Identifier Length | |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
+| |
+~ Identifier ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |
+~ Public Data ~
+| |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+.in 3
+
+.ce
+Figure 5: SILC Public Key
+
+
+.in 6
+o Public Key Length (4 bytes) - Indicates the full length
+ of the 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 is of the following
+ format:
+
+ UN User name
+ HN Host name or IP address
+ RN Real name
+ E EMail address
+ O Organization
+ C Country
+
+
+ Examples of an identifier:
+
+ `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi'
+
+ `UN=sam, HN=dummy.fi, RN=Sammy Sam, O=Company XYZ, C=Finland'
+
+ 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 written as `\\,',
+ for example, `O=Company XYZ\\, Inc.'.
+
+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.
+.in 3
+
+All fields in the public key are in MSB (most significant byte first)
+order.
+
+
+.ti 0
+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:
+
+.in 6
+SILC-<protocol version>-<software version>
+.in 3
+
+The version strings are of the following format:
+
+.in 6
+protocol version = <major>.<minor>
+software version = <major>[.<minor>[.<build>]]
+.in 3
+
+Protocol version MAY provide both major and minor version. Currently
+implementations MUST set the protocol version and accept the protocol
+version as SILC-1.0-<software version>. If new protocol version causes
+in compatibilities with older version the the <minor> versio number MUST
+be incremented. The <major> is incremented if new protocol version is
+fully incompatible.
+
+Software version MAY provide major, minor and build version. The
+software version MAY be freely set and accepted.
+
+
+Thus, the version string could be, for example:
+
+.in 6
+SILC-1.0-1.2
+.in 3
+
+
+.ti 0
+3.13 Backup Routers
+
+Backup routers may exist in the cell in addition of the primary router.
+However, they must not be active routers and 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 may one of the backup routers become
+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.
+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 actual router server when it feeds the data to
+it.
+
+In addition of having direct connection to the primary router of the
+cell, the backup router must also have connection to the same router
+the primary router of the cell is connected. However, it must not be
+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 as being 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 orignal primary
+router becomes unresponsive.
+
+All of the parties of this protocol knows which one is the backup router
+of the cell from their local configuration. Each of the entity 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. The announcements
+assures 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 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 active server in the cell. Backup router
+may be a spare server in the cell that does not accept normal client
+connections at all. It may be reserved purely for the backup purposes.
+These, however, are cell management issues.
+
+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.
+
+
+.ti 0
+3.13.1 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 orignated 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.
+
+The servers connected to the backup router must announce their clients,
+channels, channel users, channel user modes and channel modes 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 have
+and distribute the new ones to the primary route.
+
+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 informations to the backup
+router. Both must process only the ones they do not know about. If
+any of the announced modes does not match then they are enforced in
+normal manner defined later in this specification.
+
+
+.ti 0
+3.13.2 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 reassume
+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 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.
+
+ 2. Backup router sends SILC_PACKET_RESUME_ROUTER packet with type
+ value 2 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 2 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 or 2 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 3 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 3 before
+ it continues with the protocol. It knows from the session ID values
+ set in the packet when it have received all packets. The session
+ value should be different in all packets it have send earlier.
+ After the packets is received the backup router sends the
+ SILC_PACKET_RESUME_ROUTER packet with type value 4 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 first packet sent to the primary router. During this time
+ the backup router should still route all packets it is receiving
+ from server connections.
+
+ 6. The primary router receives the packet and send the
+ SILC_PACKET_RESUME_ROUTER with type value 5 to all connected servers
+ including the backup router. It also sends the packet with type
+ value 6 to its primary router, and to the router that is using
+ it as its primary router. The Session ID value in this packet
+ SHOULD be zero (0).
+
+ 7. Any server and router that receives the SILC_PACKET_RESUME_ROUTER
+ with type value 5 or 6 must switch their primary route to the
+ new primary router and remove the route for the backup router, since
+ it is not anymore 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
+ backup router connection after this and the connection is considered
+ to be passive connection. The implementations SHOULD be able
+ to disable the connection without closing the actual link.
+
+After this protocol is executed the backup router is now again 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 in the backup router are considered passive
+connections.
+
+When the primary router of the cell comes back online and connects
+to its primary router, the remote primary router must send the
+SILC_PACKET_RESUME_ROUTER with type value 20 indicating that the
+connection is not allowed since the router has been replaced by an
+backup router. The session ID value in this packet SHOULD be zero (0).
+When the router receives this packet it must not use the connection
+as active connection but to understand that it cannot act as primary
+router in the cell. It must wait that the backup router connects to
+it, and the backup resuming protocol is executed.
+
+The following type values has been defined for SILC_PACKET_RESUME_ROUTER
+packet:
+
+ 1 SILC_SERVER_BACKUP_START
+ 2 SILC_SERVER_BACKUP_START_GLOBAL
+ 3 SILC_SERVER_BACKUP_START_CONNECTED
+ 4 SILC_SERVER_BACKUP_START_ENDING
+ 5 SILC_SERVER_BACKUP_START_RESUMED
+ 6 SILC_SERVER_BACKUP_START_GLOBAL
+ 20 SILC_SERVER_BACKUP_START_REPLACED
+
+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].
+
+
+.ti 0
+3.13.3 Discussion on Backup Router Scheme
+
+It is clear that this backup router support is not able to handle all
+possible situations arrising in unreliable network environment. This
+scheme for example does not handle situation when the router actually
+does not go offline but the network link goes down temporarily. It would
+require some intelligence to figure out when it is best time to switch
+to the backup router. To make it even more complicated it is possible
+that the backup router may have not lost the network link to the primary
+router.
+
+Other possible situation is when the network link is lost temporarily
+between two primary routers in the SILC network. Unless the routers
+notice the link going down they cannot perhaps find alternative routes.
+Worst situation is when the link goes down only for a short period of
+time, thus causing lag. Should the routers or servers find alternative
+routes if they cannot get response from the router during the lag?
+When alternative routes are being found it must be careful not to
+mess up existing primary routes between routers in the network.
+
+It is suggested that the current backup router scheme is only temporary
+solution and existing backup router protocols are studied further. It
+is also suggested that the backup router specification will be separated
+from this SILC specification Internet-Draft and additional specification
+is written on the subject.
+
+
+.ti 0
+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 section describes the procedures only generally as details
+are described in [SILC2] and [SILC3].
+
+
+.ti 0
+4.1 Creating Client Connection
+
+This section describes the procedure when 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 host really is
+who it claims to be. Client, 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. 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 performs
+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
+registers itself by sending SILC_PACKET_NEW_CLIENT packet to the
+server. This packet includes various information about the client
+that the server uses to create the client. Server creates 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 those
+informations rather than what it received from client. This is suitable
+way to get the true information about client if it is available.
+
+The nickname of client is initially set to the username sent in the
+SILC_PACKET_NEW_CLIENT packet. User should set the nickname to more
+suitable 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].
+
+
+.ti 0
+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 when 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 or public key authentication.
+
+After server and router has successfully performed the key exchange
+and connection authentication protocol, the server 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.
+
+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 in [SILC2].
+
+As 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.
+
+
+.ti 0
+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. 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 the
+SILC_NOTIFY_UMODE_CHANGE nofity type into the SILC_PACKET_NOTIFY packet.
+
+Also, channel's 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.
+
+The router which receives these lists MUST process them and broadcast
+the packets to its primary route.
+
+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.
+
+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 channel founder 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.
+
+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.
+
+
+.ti 0
+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 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
+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 has 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 has 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 is set for the client.
+
+If the router created the channel in the process, information about the
+new channel MUST be broadcasted 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 if the SILC_CMODE_PRIVKEY mode is set.
+
+
+.ti 0
+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
+while creating the new key are still processed with the old key. After
+server has sent the SILC_PACKET_CHANNEL_KEY packet MUST client start
+using the new key. If server creates the new key the server MUST also
+send the new key to its router. See [SILC2] on more information about
+how channel messages must be encrypted and decrypted when router is
+processing them.
+
+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 HMAC key that is used to compute
+the MACs of the channel messages. The processing is as follows:
+
+ channel_key = raw key data
+ HMAC key = hash(raw key data)
+
+The raw key data is the key data received in the Channel Key Payload.
+The hash() function is the hash function used in the HMAC of the channel.
+Note that the server MUST also save the channel key.
+
+
+.ti 0
+4.5 Private Message Sending and Reception
+
+Private messages are sent point to point. Client explicitly destines
+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 any
+other packet as well.
+
+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.
+
+See [SILC2] for description of private message encryption and decryption
+process.
+
+
+.ti 0
+4.6 Private Message Key Generation
+
+Private message MAY be protected by the key generated by the client.
+The key may be generated and sent to the other client by sending packet
+SILC_PACKET_PRIVATE_MESSAGE_KEY which travels through the network
+and is secured by session keys. After that the private message key
+is used in the private message communication between those clients.
+
+Other choice is to entirely use keys that are not sent through
+the SILC network at all. This significantly adds security. This key
+would be pre-shared-key that is known by both of the clients. Both
+agree about using the key and starts sending packets that indicate
+that the private message is secured using private message key.
+
+The key material used as private message key is implementation issue.
+However, SILC_PACKET_KEY_AGREEMENT packet MAY be used to negotiate
+the key material. If the key is normal pre-shared-key or randomly
+generated key, and the SILC_PACKET_KEY_AGREEMENT was not used, then
+the key material SHOULD be processed as defined in the [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], however, the HMAC key material MUST be discarded.
+
+If the key is pre-shared-key or randomly generated the implementations
+should use the SILC protocol's mandatory cipher as the cipher. If the
+SKE was used to negotiate key material the cipher was negotiated as well.
+
+.ti 0
+4.7 Channel Message Sending and Reception
+
+Channel messages are delivered to group of users. The group forms a
+channel and all clients on the channel receives messages sent to the
+channel.
+
+Channel messages are destined to channel by specifying the Channel ID
+as Destination ID in the SILC Packet Header. The server MUST then
+distribute the message to all clients on the channel by sending the
+channel message destined explicitly to a client on the channel.
+
+See the [SILC2] for description of channel messege routing for router
+servers.
+
+See [SILC2] for description of channel message encryption and decryption
+process.
+
+
+.ti 0
+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
+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 has 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.
+
+
+.ti 0
+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.
+
+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. 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 server. Client
+MUST NOT accept command reply packet originated from anyone else but
+from its own server.
+
+
+.ti 0
+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.
+
+
+.ti 0
+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 on 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 acceptance to
+the SILC Network. Even though, the SILC protocol is secure in a network
+of mutual distrust between clients, servers, routers and adminstrators
+of the servers, the client should be able to trust the servers they are
+using if they whish 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 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 full proof system and cannot secure from insecure environment; the
+SILC servers and routers could very well be compromised. However, to
+provide acceptable level of security and usability for end user the
+protocol use many times session keys or other keys generated by the
+servers to secure the messages. This is intentional design feature to
+allow ease of use for end user. 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 always negotiate the keys outside SILC
+network. This is 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
+negotiatied outside the SILC Network should always be used. In the end
+it is always 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.
+
+
+.ti 0
+6 References
+
+[SILC2] Riikonen, P., "SILC Packet Protocol", 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
+7 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 / commitdiff