+++ /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 13 September 2000
-.ds CH
-.na
-.hy 0
-.in 0
-.nf
-Network Working Group P. Riikonen
-Internet-Draft
-draft-riikonen-silc-spec-00.txt 13 September 2000
-Expires: 13 May 2001
-
-.in 3
-
-.ce 3
-Secure Internet Live Conferencing (SILC),
-Protocol Specification
-<draft-riikonen-silc-spec-00.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 SILC network. Two
-other Internet Drafts relates very closely to this memo; SILC Packet
-Protocol [SILC2] and SILC Key Exchange and Authentication Protocols
-[SILC3].
-
-
-
-
-
-
-
-
-.ti 0
-Table of Contents
-
-.nf
-1 Introduction .................................................. 3
-2 SILC Concepts ................................................. 3
- 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
-3 SILC Specification ............................................ 7
- 3.1 Client .................................................... 7
- 3.1.1 Client ID ........................................... 8
- 3.2 Server .................................................... 9
- 3.2.1 Server's Local ID List .............................. 9
- 3.2.2 Server ID ........................................... 10
- 3.2.3 SILC Server Ports ................................... 11
- 3.3 Router .................................................... 11
- 3.3.1 Router's Local ID List .............................. 11
- 3.3.2 Router's Global ID List ............................. 12
- 3.3.3 Router's Server ID .................................. 13
- 3.4 Channels .................................................. 13
- 3.4.1 Channel ID .......................................... 14
- 3.5 Operators ................................................. 14
- 3.6 SILC Commands ............................................. 15
- 3.7 SILC Packets .............................................. 15
- 3.8 Packet Encryption ......................................... 16
- 3.8.1 Determination of the Source and the Destination ..... 16
- 3.8.2 Client To Client .................................... 17
- 3.8.3 Client To Channel ................................... 18
- 3.8.4 Server To Server .................................... 19
- 3.9 Key Exchange And Authentication ........................... 19
- 3.10 Algorithms ............................................... 19
- 3.10.1 Ciphers ............................................ 19
- 3.10.2 Public Key Algorithms .............................. 20
- 3.10.3 MAC Algorithms ..................................... 20
- 3.10.4 Compression Algorithms ............................. 21
- 3.11 SILC Public Key .......................................... 21
- 3.12 SILC Version Detection ................................... 24
-4 SILC Procedures ............................................... 24
- 4.1 Creating Client Connection ................................ 24
- 4.2 Creating Server Connection ................................ 25
- 4.3 Joining to a Channel ...................................... 26
- 4.4 Channel Key Generation .................................... 27
- 4.5 Private Message Sending and Reception ..................... 27
- 4.6 Private Message Key Generation ............................ 28
- 4.7 Channel Message Sending and Reception ..................... 29
- 4.8 Session Key Regeneration .................................. 29
- 4.9 Command Sending and Reception ............................. 29
-5 SILC Commands ................................................. 30
- 5.1 SILC Commands Syntax ...................................... 30
- 5.2 SILC Commands List ........................................ 32
- 5.3 SILC Command Status Types ................................. 53
- 5.3.1 SILC Command Status Payload ......................... 53
- 5.3.2 SILC Command Status List ............................ 54
-6 Security Considerations ....................................... 59
-7 References .................................................... 59
-8 Author's Address .............................................. 60
-
-
-.ti 0
-List of Figures
-
-.nf
-Figure 1: SILC Network Topology
-Figure 2: Communication Inside cell
-Figure 3: Communication Between Cells
-Figure 4: SILC Public Key
-Figure 5: SILC Command Status Payload
-
-
-.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
-SILC network. Two other Internet Drafts relates very closely to this
-memo; SILC Packet Protocol [SILC2] and SILC Key Exchange and
-Authentication Protocols [SILC3].
-
-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
-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 centrum on the cell and servers are connected to the router.
-
-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
-servers. 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 will 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. Client who 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. 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. message sent 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 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. 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. message sent
- 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 client point of view is
-when clients are connected directly to the routers and the messages
-are delivered from one router to the other router.
-
-
-.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 who are
-joined to the channel. Also, router distributes the message to its
-local clients on the channel.
-
-
-.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 hostname 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 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. Another difference is that there are no limit of the length
-of the nickname in the SILC.
-
-
-.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.
-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 ServerID IP address (bits 1-32)
- 8 bit Random number
-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 - Random number to further randomize the
- Client ID. 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 focuses on the normal server and router server is described
-in the section 3.3 Router.
-
-Normal servers may 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 may not connect to other
-cell's router except in situations where its cell's router is unavailable.
-
-Servers and routers in the SILC network are considered to be trusted.
-With out a doubt, servers that are set to work on ports above 1023 are
-not considered to be trusted. Also, the service provider acts important
-role in the server's trustworthy.
-
-
-.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 hostnames 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
-
-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.
-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
-
-o IP address of the server - This is the real IP address of
- the server.
-
-o Port - This is the port the server is binded 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 resposible of
-distributing it to the router.
-
-
-.ti 0
-3.2.3 SILC Server Ports
-
-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 keep
-information about user's nickname, username and hostname and real name
-since these are not needed by the router. 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 hostnames or user's real names. Router does not 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. Server ID's for routers are always
-created by the remote router where the router is connected to.
-
-
-.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 leaves 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 that unifies each channel. However, channel names are still
-unique and no two global channels with same name may exist. Channel name
-is a string which begins with `#' character. There is no limit on the
-length of the channel name. Channel names may 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. Following operators on channel exist on 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. 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 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
-
-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 may not send command
-to client and there are some commands that server must not send. Server
-is also able to send the forwarded command packets. For example,
-SILC_COMMAND_JOIN is always forwarded packet. See [SILC2] for more
-about packet forwarding.
-
-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,
-however, choose not to accept the command reply, but there are some
-command replies that the client should accept. Example of a such
-command reply is reply to SILC_COMMAND_CMODE command that the server
-uses to distribute the channel mode on all clients on the channel
-when the mode has changed.
-
-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. This should be sufficient to prevent the miss-use
-of commands.
-
-SILC commands are described in section 5 SILC Commands.
-
-
-.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. 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 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 knows 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 is always 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 does 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 case, for example, with command packets.
-
-
-.ti 0
-3.8.2 Client To Client
-
-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
-3.10 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.
-
-
-
-
-
-
-Following ciphers are defined in SILC protocol:
-
-.in 6
-blowfish-cbc Blowfish in CBC mode (mandatory)
-twofish-cbc Twofish in CBC mode (optional)
-rc6-cbc RC6 in CBC mode (optional)
-rc5-cbc RC5 in CBC mode (optional)
-mars-cbc Mars in CBC mode (optional)
-none No encryption (optional)
-.in 3
-
-
-All algorithms must use minimum of 128 bit key, by default. Several
-algorithms, however, supports longer keys and it is recommended to use
-longer keys if they are available.
-
-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].
-
-Following public key algorithms are defined in SILC protocol:
-
-.in 6
-rsa RSA (mandatory)
-dss DSS (optional)
-.in 3
-
-Both of the algorithms are described in [Scheneir] and [Menezes].
-
-Additional public key algorithms may be defined to be used in SILC.
-
-
-.ti 0
-3.10.3 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.
-
-
-
-
-
-Following MAC algorithms are defined in SILC protocol:
-
-.in 6
-hmac-sha1 HMAC-SHA1, length = 20 (mandatory)
-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
-3.10.4 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.
-
-Following compression algorithms are defined:
-
-.in 6
-none No compression (mandatory)
-zlib GBU 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 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 4: 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 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 intiator and responder. The
-version identifier is of following format:
-
-.in 6
-SILC-<protocol version>-<software version>
-.in 3
-
-The version strings are of 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-<sotware version>.
-
-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
-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 descibres 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 must have
-both valid IP address and fully qualified domain name (FQDN).
-
-After that 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 a 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 descibres 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. 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. 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.
-
-If the server has already connected clients and locally created
-channels the server must distribute these informations to the router.
-The distribution is done by sending packet SILC_PACKET_NEW_CHANNEL.
-See [SILC2] for more information on this.
-
-
-.ti 0
-4.3 Joining to a Channel
-
-This section describes the procedure when client joins to a channel.
-Client may join 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 client, new channel key is created and information about
-newly joined channel is sent to the router. The new channel key is
-also distributed to the router and to all clients on the channel.
-
-If the channel does not exist in the local list the command must be
-fowarded 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 distributed to the client who sent the command
-originally. Server will also receive the channel key from the server
-that it must distribute to the client who 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 who 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.
-
-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.
-
-When the router joins the client to the channel it must send
-information about newly joined client to all routers in the SILC
-network. Also, if the channel was created in the process, information
-about newly created channel must also be distributed to all routers.
-The distribution of newly created channel is done by sending packet
-SILC_PACKET_NEW_CHANNEL.
-
-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 who receives the reply to the join command must start using
-the received Channel ID in the channel message communication thereafter.
-However, client must not start communicating on the channel before
-it has received the packet SILC_PACKET_CHANNEL_KEY.
-
-If client wants to know the other clients currently on the channel
-the client must send SILC_COMMAND_NAMES command to receive a list of
-channel users. Server implementation, however, may send command reply
-packet to SILC_COMMAND_NAMES command after client has joined to the
-channel even if the client has not sent the command.
-
-
-.ti 0
-4.4 Channel Key Generation
-
-Channel keys are created by router who 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, who leaved 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.
-
-
-.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 ipmlementations
-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.
-
-Receiver of a private message should not explicitly trust the nickname
-that it receives in the Private Message Payload, described in [SILC2].
-Implementations could resolve the nickname from server, as described
-previously, and compare the received Client ID and the SILC Packet
-Header's Client ID. The nickname in the payload is merely provided
-to be displayed for end user.
-
-See [SILC2] for describtion of private message encryption and decryption
-process.
-
-
-.ti 0
-4.6 Private Message Key Generation
-
-Private message may be protected by key generated by 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.
-See more information about how this works technically in [SILC2].
-
-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. This
-is the technical aspect mentioned previously that is described
-in [SILC2].
-
-If the private message keys are not set to be used, which is the
-case by default in SILC, the private messages are secured by using
-normal session keys established by SILC Key Exchange protocol.
-
-
-
-
-.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 [SILC2] for describtion of channel message encryption and decryption
-process.
-
-
-.ti 0
-4.8 Session Key Regeneration
-
-Session keys should be regenerated peridiocally, 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.
-
-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 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
-hashing the old key with hash function selected earlier in the SKE
-protocol. If the digest length of the hash function is too short for the
-key, then the key is distributed as described in section Processing the
-Key Material in [SILC3]. After both parties has regenerated the session
-key, both send SILC_PACKET_REKEY_DONE packet to each other. These packets
-are still secured with the old key. After these packets, following
-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 usually
-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
-to further to receive the exact information about the requested client.
-The WHOIS command travels all the way to the server who owns the client
-and it replies with command reply packet. Finally, the server who
-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
-5 SILC Commands
-
-.ti 0
-5.1 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 succefully or
-whether there was an error. If error occured 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, regardles 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 5.3 SILC Command Status Types.
-.in 3
-
-
-.ti 0
-5.2 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: 3
- Arguments: (1) <nickname>[@<server>] (2) [<Client ID>]
- (3) [<count>]
-
- Whois command is used to query various information about specific
- user. The user maybe 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 maybe 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.
-
- It is also possible to search the user by Client ID. If <Client ID>
- is provided server must use it as the search value instead of
- the <nickname>.
-
- To prevent miss-use of this service wildcards in the nickname
- or in the servername 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 forwarded to router by server
- so that all users are searched. However, the server still must
- search its locally connected clients. The server must send
- this command to the server who owns the requested client. That
- server must reply to the command.
-
- Reply messages to the command:
-
- Max Arguments: 7
- Arguments: (1) <Status Payload> (2) <Client ID>
- (3) <nickname>[@<server>] (4) <username@host>
- (5) <real name> (6) [<channel list>]
- (7) [<idle time>]
-
- 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 servername, username and hostnamea and users 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.
-
- 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
-
-
- 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 maybe 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 maybe
- 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.
-
- To prevent miss-use of this service wildcards in the nickname
- or in the servername are not permitted. The WHOWAS requests must
- be based on specific nickname request.
-
- The WHOWAS request must be always forwarded to 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: 3
- Arguments: (1) <Status Payload> (2) <nickname>[@<server>]
- (3) <username@host>
-
- 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 username and hostname.
- 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: 2
- Arguments: (1) <nickname>[@<server>] (2) [<count>]
-
- Identify. Identify command is almost analogous to WHOIS command,
- except that it does not return as much information. Only relevant
- information such as Client ID is returned. This is usually used
- to get the Client ID of a client used in the communication with
- the client.
-
- The query may find multiple matching users as there are no unique
- nicknames in the SILC. The <count> option maybe 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.
-
- To prevent miss-use of this service wildcards in the nickname
- or in the servername are not permitted. It is not allowed
- to request all users on some server. The IDENTIFY requests must
- be based on specific nickname request.
-
- Implementations may not want to give interface access to this
- command as it is hardly a command that would be used a end user.
- However, it must be implemented as it is used with private message
- sending.
-
- The IDENTIFY must be always forwarded to 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) <Client ID>
- (3) [<nickname>[@<server>]] (4) [<username@host>]
-
- 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 Client ID of the nickname and if more
- information is available it may reply with nickname and username
- and hostname. 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_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. There is no limit of the length of the nickname in SILC.
- Nickname must not include any spaces (` '), non-printable
- characters, commas (`,') and any wildcard characters. Note:
- nicknames in SILC are case-sensitive which must be taken into
- account when searching clients by nickname.
-
- 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: 2
- Arguments: (1) [<Channel ID>] [<server>]
-
- The list command is used to list channels and their topics on
- 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.
-
- If the <server> argument is specified the specified server's
- channels are listed. In this case the command must be sent to
- the server who owns the channel that was requested.
-
- Reply messages to the command:
-
- Max Arguments: 4
- Arguments: (1) <Status Payload> (2) <Channel ID>
- (3) <channel> (4) <topic>
-
- 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> includes
- "*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
- SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
- SILC_STATUS_ERR_NO_SUCH_SERVER
-
-
- 6 SILC_COMMAND_TOPIC
-
- Max Arguments: 2
- Arguments: (1) <Channel ID> (2) [<server>]]
-
- 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.
-
- Reply messages to the command:
-
- Max Arguments: 2
- Arguments: (1) <Status Payload> (2) [<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: 2
- Arguments: (1) <Client ID> (2) <Channel ID>
-
- 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. This command must fail if the requested channel does
- not exist, the requested client 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: 2
- 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_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
-
-
- 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.
-
- 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
-
-
-
-
-
- 10 SILC_COMMAND_INFO
-
- Max Arguments: 1
- Arguments: (1) [<server>]
-
- 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.
-
- Reply messages to the command:
-
- Max Arguments: 3
- Arguments: (1) <Status Payload> (2) <Server ID>
- (3) <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
-
-
- 11 SILC_COMMAND_CONNECT
-
- Max Arguments: 2
- Arguments: (1) <Server ID>
- (2) [<remote server/router>[:<port>]]
-
- This command is used by operators to force a server to try to
- establish a new connection to another router (if the connecting
- server is normal server) or server (if the conneceting server is
- router server). Operator may specify the server/router to be
- connected by setting <remote server> argument.
-
- 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_SERVER_ID
- 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 data>
-
- 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 data> is the data that the
- client is authenticated against. It may be passphrase prompted
- for user on client's screen or it may be public key
- authentication data (data signed with private key), or
- certificate.
-
- 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_BAD_PASSWORD
- SILC_STATUS_ERR_AUTH_FAILED
-
-
- 14 SILC_COMMAND_JOIN
-
- Max Arguments: 3
- Arguments: (1) <channel> (2) [<passphrase>]
- (3) [<cipher>]
-
- 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 forwarded
- to router who 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.
-
- 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 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/hostname 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: 5
- Arguments: (1) <Status Payload> (2) <channel>
- (3) <Channel ID> (4) <channel mode mask>
- (5) [<topic>]
-
- This command replies with the channel name requested by the
- client, channel ID of the channel and topic of the channel
- if it exists. 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).
-
- Client must not start transmitting to the channel even after
- server has replied to this command. Client is permitted to
- start transmitting on channel after server has sent packet
- SILC_PACKET_CHANNEL_KEY to the client.
-
- 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 a server.
-
- Reply messages to the command:
-
- Max Arguments: 2
- Arguments: (1) <Status Payload> (2) [<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 may 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.
-
- 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 cannot
- 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
- cannot 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.
-
- 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 is required 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_UNKNOWN_MODE
- SILC_STATUS_ERR_NO_RECIPIENT
- SILC_STATUS_ERR_NO_CLIENT_ID
-
-
- 17 SILC_COMMAND_CMODE
-
- Max Arguments: 8
- Arguments: (1) <Channel ID> (2) <channel mode mask>
- (3) [<user limit>] (4) [<passphrase>]
- (5) [<ban mask>] (6) [<invite list>]
- (7) [<Client ID>] (8) [<cipher>[:<key len>]]
-
- 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.
-
- 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 indicatioin 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). This specification does not define how the private
- channel key is set as it is entirely local setting on
- client end.
-
- 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_BAN
-
- Ban mask has been set to the channel. The ban mask
- may be used to ban specific clients to join the channel.
- The <ban mask> argument is the set ban mask. When
- unsetting a ban mask the mask must be provided as
- argument. Channel founder and channel operator may
- set/unset this mode. Channel founder may not be
- added to the ban list.
-
- Typical implementation would use [+|-]b on user interface
- to set/unset this mode.
-
-
- 0x0100 SILC_CMODE_INVITE
-
- Invite list has been set to the channel. The invite list
- can be used to mark the clients that is able to join
- channel without being invited when the channel is set to
- be invite-only channel. The <invite list> argument is the
- set invite mask. When unsetting entry from the invite list
- the entry must be provided as argument. Channel founder and
- channel operator may set/unset this mode.
-
- Typical implementation would use [+|-]I on user interface
- to set/unset this mode.
-
-
- 0x0200 SILC_CMODE_OPERATOR
-
- Sets channel operator privileges on the channel for a
- client on the channel. The <Client ID> argument is the
- target client on the channel. Channel founder and
- channel operator may set/unset (promote/demote) this
- mode.
-
- Typical implementation would use [+|-]o on user interface
- to set/unset this mode.
-
-
- 0x0400 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. If <key len> argument is specified with
- <cipher> argument the new key is generated of <key len>
- length.
-
- Typical implementation would use [+|-]c 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 distributes the changed channel mode mask to
- all clients on the channel by sending SILC_COMMAND_CMODE command
- reply packet.
-
-
- Reply messages to the command:
-
- Max Arguments: 2
- Arguments: (1) <Status Payload> (2) <channel mode mask>
-
- This command replies with the changed channel mode mask that
- client is required to keep locally. The same mask is also
- sent to all clients on channel by sending additional command
- reply to them.
-
- 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_CLIENT_ID
-
-
-
-
- 18 SILC_COMMAND_KICK
-
- Max Arguments: 3
- Arguments: (1) <channel> (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.
-
- 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
-
-
- 19 SILC_COMMAND_RESTART
-
- Max Arguments: 0
- Arguments: None
-
- This command may only be used by server operator to force a
- server to restart itself.
-
- 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
-
-
- 20 SILC_COMMAND_CLOSE
-
- Max Arguments: 1
- Arguments: (1) <Server ID>
-
- This command is used only by operator to close connection to a
- remote site. The <Server ID> argument is the ID of the remote
- site and must be valid.
-
- 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
-
-
- 21 SILC_COMMAND_DIE
-
- 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
-
-
- 22 SILC_COMMAND_SILCOPER
-
- Max Arguments: 2
- Arguments: (1) <username> (2) <authentication data>
-
- This command is used by normal client to obtain router operator
- privileges (also known as SILC operator) on some router. Note
- that router operator has router privileges that supersedes the
- server operator privileges.
-
- The <username> is the username set in the server configurations
- as operator. The <authentication data> is the data that the
- client is authenticated against. It may be passphrase prompted
- for user on client's screen or it may be public key
- authentication data (data signed with private key), or
- certificate.
-
- 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.
-
- 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_BAD_PASSWORD
- SILC_STATUS_ERR_AUTH_FAILED
-
-
- 23 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. After a client has leaved the channel the server
- must create new key for the channel and distribute to all clients
- still currently on the channel.
-
- 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
-
-
- 24 SILC_COMMAND_NAMES
-
- Max Arguments: 1
- Arguments: (1) <Channel ID>
-
- This command is used to list user names currently on the requested
- channel; argument <Channel ID>. 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 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.
-
- Reply messages to the command:
-
- Max Arguments: 3
- Arguments: (1) <Status Payload> (2) <Channel ID>
- (3) <name list> (4) <Client ID list>
-
- This command replies with the Channel ID of the requested channel,
- comma separated list of users on the channel and Client ID list
- of the users on the list. The Client ID list has Client ID's
- of all users in the list. First Client ID in the list must be
- the Client ID of the first user in <name list>. The Client ID
- List is formed by adding Client ID's each after each. Note that
- the Client ID list is binary data.
-
- 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
-
-
- 25 - 254
-
- Currently undefined commands.
-
-
- 255 SILC_COMMAND_MAX
-
- Reserved command. This must not be sent.
-.in 3
-
-
-.ti 0
-5.3 SILC Command Status Types
-
-.ti 0
-5.3.1 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. 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 5: 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
-5.3.2 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 occured the status tells which error occured. 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_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
- beloning to this list after this one.
-
- 3 - 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
- client user is not currently on.
-
- 26 SILC_STATUS_ERR_USER_ON_CHANNEL
-
- "User already on channel". User were invited on channel they
- already are on.
-
- 27 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.
-
- 28 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
-
- "Not enough parameters". Command requires more parameters
- than provided.
-
- 29 SILC_STATUS_ERR_TOO_MANY_PARAMS
-
- "Too many parameters". Too many parameters were provided
- for the command.
-
- 30 SILC_STATUS_ERR_PERM_DENIED
-
- "Your host is not among the privileged". The client tried to
- register on server that does not allow this host to connect.
-
- 31 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.
-
-
-
- 32 SILC_STATUS_ERR_BAD_PASSWORD
-
- "Cannot join channel. Incorrect password". Password provided for
- channel were not accepted.
-
- 33 SILC_STATUS_ERR_CHANNEL_IS_FULL
-
- "Cannot join channel. Channel is full". The channel is full
- and client cannot be joined to it.
-
- 34 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.
-
- 35 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
-
- "Cannot join channel. You have been banned". The client has
- been banned from the channel.
-
- 36 SILC_STATUS_ERR_UNKNOWN_MODE
-
- "Unknown mode". Mode provided by the client were unknown to
- the server.
-
- 37 SILC_STATUS_ERR_NOT_YOU
-
- "Cannot change mode for other users". User tried to change
- someone else's mode.
-
- 38 SILC_STATUS_ERR_NO_CHANNEL_PRIV
-
- "Permission denied. You are not channel operator". Command may
- be executed only by channel operator.
-
- 39 SILC_STATUS_ERR_NO_SERVER_PRIV
-
- "Permission denied. You are not server operator". Command may
- be executed only by server operator.
-
- 40 SILC_STATUS_ERR_NO_ROUTER_PRIV
-
- "Permission denied. You are not SILC operator". Command may be
- executed only by router (SILC) operator.
-
- 41 SILC_STATUS_ERR_BAD_NICKNAME
-
- "Bad nickname". Nickname requested contained illegal characters
- or were malformed.
-
- 42 SILC_STATUS_ERR_BAD_CHANNEL
-
- "Bad channel name". Channel requested contained illegal characters
- or were malformed.
-
- 43 SILC_STATUS_ERR_AUTH_FAILED
-
- "Authentication failed". The authentication data sent as
- argument were wrong and thus authentication failed.
-.in 3
-
-
-.ti 0
-6 Security Considerations
-
-Security is central to the design of this protocol, and these security
-considerations permeate the specification.
-
-
-
-
-
-.ti 0
-7 References
-
-[SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
- June 2000.
-
-[SILC3] Riikonen, P., "SILC Key Exchange and Authentication
- Protocols", Internet Draft, June 2000.
-
-[IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
- RFC 1459, May 1993.
-
-[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 Exhange
- (IKE)", RFC 2409, November 1998.
-
-[HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
- Authentication", RFC 2104, February 1997.
-
-
-
-.ti 0
-8 Author's Address
-
-.nf
-Pekka Riikonen
-Kasarmikatu 11 A4
-70110 Kuopio
-Finland
-
-EMail: priikone@poseidon.pspt.fi
-
-This Internet-Draft expires 13 May 2001
projects / crypto.git / blobdiff