Network Working Group P. Riikonen Internet-Draft draft-riikonen-silc-spec-00.txt 28 June 2000 Expires: 28 Jan 2001 Secure Internet Live Conferencing (SILC), Protocol Specification <draft-riikonen-silc-spec-00.txt> 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. 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]. Riikonen [Page 1]
Internet Draft 28 June 2000 Table of Contents 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 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 Riikonen [Page 2]
Internet Draft 28 June 2000 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 List of Figures 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 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. Riikonen [Page 3]
Internet Draft 28 June 2000 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. 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. Riikonen [Page 4]
Internet Draft 28 June 2000 ---- ---- ---- ---- ---- ---- | S8 | S5 | S4 | | S7 | S5 | S6 | ----- ---- ----- ----- ---- ----- | S7 | S/R1 | S2 | --- | S8 | S/R2 | S4 | ---- ------ ---- ---- ------ ---- | S6 | S3 | S1 | | S1 | S3 | S2 | ---- ---- ---- ---- ---- ---- ---- ---- | S3 | S1 | Cell 1. \ Cell 2. | \____ ----- ----- | | | S4 | S/R4 | ---- ---- ---- ---- ---- ---- ---- ------ | S7 | S4 | S2 | | S1 | S3 | S2 | | S2 | S5 | ----- ---- ----- ----- ---- ----- ---- ---- | S6 | S/R3 | S1 | --- | S4 | S/R5 | S5 | Cell 4. ---- ------ ---- ---- ------ ---- | S8 | S5 | S3 | | S6 | S7 | S8 | ... etc ... ---- ---- ---- ---- ---- ---- Cell 3. Cell 5. Figure 1: SILC Network Topology A cell is formed when a server or servers connect to one router. In 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. 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 Riikonen [Page 5]
Internet Draft 28 June 2000 scenario. 1 --- S1 S4 --- 5 S/R 2 -- S2 S3 / | 4 3 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. 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. 1 --- S1 S4 --- 5 S2 --- 1 S/R - - - - - - - - S/R 2 -- S2 S3 S1 / | \ 4 3 2 Cell 1. Cell 2. Figure 3: Communication Between Cells Riikonen [Page 6]
Internet Draft 28 June 2000 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. 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. 3. SILC Specification This section describes the SILC protocol. However, [SILC2] and [SILC3] describes other important protocols that are part of this SILC specification and must be read. 3.1 Client A client is a piece of software connecting to SILC server. SILC client cannot be SILC server. Purpose of clients is to provide the user interface of the SILC services for end user. Clients are distinguished from other clients by unique Client ID. Client ID is a 128 bit ID that is used in the communication in the SILC network. The client ID is based on the 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. Riikonen [Page 7]
Internet Draft 28 June 2000 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. 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. 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 unify 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. 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 Riikonen [Page 8]
Internet Draft 28 June 2000 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. 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. 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. Riikonen [Page 9]
Internet Draft 28 June 2000 Hence, local list for normal server includes: server list - Router connection o Server name o Server IP address o Server ID o Sending key o Receiving key o Public key client list - All clients in server o Nickname o Username@host o Real name 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 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. 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 unify the Server ID. Collisions are not expected to happen in any conditions. The Server ID Riikonen [Page 10]
Internet Draft 28 June 2000 is always created by the server itself and server is resposible of distributing it to the router. 3.2.3 SILC Server Ports SILC uses currently TCP port 334 on SILC network. However, this is not official port assigned for SILC. Official port has been requested by the IANA. If there are needs to create new SILC networks in the future the port numbers must be officially assigned by the IANA. Most convenience case would be to assign port numbers upwards from 334. Server on network above privileged ports (>1023) should not be trusted as they could have been set up by untrusted party. 3.3 Router Router server in SILC network is responsible for keeping the cell together and routing messages to other servers and to other routers. Router server 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. 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. Riikonen [Page 11]
Internet Draft 28 June 2000 Hence, local list for router includes: server list - All servers in the cell o Server name o Server ID o Router's Server ID o Sending key o Receiving key client list - All clients in the cell o Client ID 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 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. 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: server list - All servers in SILC o Server name o Server ID o Router's Server ID Riikonen [Page 12]
Internet Draft 28 June 2000 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 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. 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. 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. Riikonen [Page 13]
Internet Draft 28 June 2000 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. 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. 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 unify the Channel ID. This makes sure that there are no collisions. This also means that in a cell there can be 2^16 channels. 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 Riikonen [Page 14]
Internet Draft 28 June 2000 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. 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. 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. 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. Riikonen [Page 15]
Internet Draft 28 June 2000 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. 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 Riikonen [Page 16]
Internet Draft 28 June 2000 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. 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. Riikonen [Page 17]
Internet Draft 28 June 2000 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. 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. Riikonen [Page 18]
Internet Draft 28 June 2000 o All clients receiving the packet decrypts the packet. 3.8.4 Server To Server Server to server packet delivery and encryption is described in above examples. Router to router packet delivery is analogous to server to server. However, some packets, such as channel packets, are processed differently. These cases are described later in this document and more in detail in [SILC2]. 3.9 Key Exchange And Authentication Key exchange is done always when for example client connects to server but also when server and router and router and 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]. 3.10 Algorithms This section defines all the allowed algorithms that can be used in the SILC protocol. This includes mandatory cipher, mandatory public key algorithm and MAC algorithms. 3.10.1 Ciphers Cipher is the encryption algorithm that is used to protect the data in the SILC packets. See [SILC2] 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. Riikonen [Page 19]
Internet Draft 28 June 2000 Following ciphers are defined in SILC protocol: 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) 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. 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: rsa RSA (mandatory) dss DSS (optional) Both of the algorithms are described in [Scheneir] and [Menezes]. Additional public key algorithms may be defined to be used in SILC. 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. Riikonen [Page 20]
Internet Draft 28 June 2000 Following MAC algorithms are defined in SILC protocol: hmac-sha1 HMAC-SHA1, length = 20 (mandatory) hmac-md5 HMAC-MD5, length = 16 (optional) none No MAC (optional) The none MAC is not recommended to be used as the packet is not authenticated when MAC is not computed. It is recommended that no client or server would accept none MAC except in special debugging mode. The HMAC algorithm is described in [HMAC] 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. 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: none No compression (mandatory) zlib GBU ZLIB (LZ77) compression (optional) Additional compression algorithms may be defined to be used in SILC. 3.11 SILC Public Key This section defines the type and format of the SILC public key. All implementations must support this public key type. See [SILC3] for other optional public key and certificate types allowed in SILC protocol. Public keys in SILC may be used to authenticate entities and to perform other tasks related to public key cryptography. The format of the SILC Public Key is as follows: Riikonen [Page 21]
Internet Draft 28 June 2000 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Public Key Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm Name Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | ~ Algorithm Name ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | ~ Identifier ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Public Data ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: SILC Public Key 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 Riikonen [Page 22]
Internet Draft 28 June 2000 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. All fields in the public key are in MSB (most significant byte first) order. Riikonen [Page 23]
Internet Draft 28 June 2000 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]. 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]. Riikonen [Page 24]
Internet Draft 28 June 2000 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]. 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 Riikonen [Page 25]
Internet Draft 28 June 2000 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. 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 sent to the router which will then perform the actual joining procedure. When server receives the reply to the command from the router it must be 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 Riikonen [Page 26]
Internet Draft 28 June 2000 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. 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. 4.5 Private Message Sending and Reception Private messages are sent point to point. Client explicitly destines Riikonen [Page 27]
Internet Draft 28 June 2000 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. 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. Riikonen [Page 28]
Internet Draft 28 June 2000 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. 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. 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 Riikonen [Page 29]
Internet Draft 28 June 2000 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. 5 SILC Commands 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. Riikonen [Page 30]
Internet Draft 28 June 2000 Example: Arguments: (1) <nickname> (2) <username@host> Every command replies with Status Payload. This payload tells the sender of the command whether the command was completed 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: EXAMPLE_COMMAND Max Arguments: 3 Arguments: (1) <nickname>[@<server>] (2) <message> (3) [<count>] The command has maximum of 3 arguments. However, only first and second arguments are mandatory. First argument <nickname> is mandatory but may have optional <nickname@server> format as well. Second argument is mandatory <message> argument. Third argument is optional <count> argument. The numbers in parentheses are the argument specific numbers that specify the type of the argument in Command Argument Payload. The receiver always knows that, say, argument number two (2) is <message> argument, 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. Riikonen [Page 31]
Internet Draft 28 June 2000 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. 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. 0 SILC_COMMAND_NONE None. This is reserved command and must not be sent. 2 SILC_COMMAND_WHOIS Max Arguments: 2 Arguments: (1) <nickname>[@<server>] (2) [<count>] Whois. 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. 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 Riikonen [Page 32]
Internet Draft 28 June 2000 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 3 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 Riikonen [Page 33]
Internet Draft 28 June 2000 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 4 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. Riikonen [Page 34]
Internet Draft 28 June 2000 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 commands 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 Riikonen [Page 35]
Internet Draft 28 June 2000 5 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 6 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. Riikonen [Page 36]
Internet Draft 28 June 2000 Reply messages to the command: Max Arguments: 3 Arguments: (1) <Status Payload> (2) <channel> (3) <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 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 7 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. Riikonen [Page 37]
Internet Draft 28 June 2000 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 8 SILC_COMMAND_INVITE Max Arguments: 2 Arguments: (1) <Client ID> (2) <channel> This command is used to invite other clients to join to the channel. There is no requirement that the channel the target client is being invited to must exist or be a valid channel. The <Client ID> argument is the target client's ID that is being invited. 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_ON_CHANNEL SILC_STATUS_ERR_WILDCARDS SILC_STATUS_ERR_NOT_REGISTERED SILC_STATUS_ERR_NOT_ENOUGH_PARAMS SILC_STATUS_ERR_NO_SUCH_CLIENT_ID SILC_STATUS_ERR_TOO_MANY_PARAMS SILC_STATUS_ERR_NO_RECIPIENT SILC_STATUS_ERR_USER_ON_CHANNEL SILC_STATUS_ERR_NO_CLIENT_ID Riikonen [Page 38]
Internet Draft 28 June 2000 9 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. 10 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 Riikonen [Page 39]
Internet Draft 28 June 2000 11 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_TOO_MANY_PARAMS SILC_STATUS_ERR_NO_SUCH_SERVER_ID SILC_STATUS_ERR_NO_SUCH_SERVER 12 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. Riikonen [Page 40]
Internet Draft 28 June 2000 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 13 SILC_COMMAND_PING Max Arguments: 1 Arguments: (1) <Server ID> This command is used by clients to test the communication channel to its server if client suspects that the communication is not working correctly. The <Server ID> is the ID of the server the client 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_SUCH_SERVER_ID SILC_STATUS_ERR_NOT_REGISTERED 14 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 Riikonen [Page 41]
Internet Draft 28 June 2000 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 15 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 on the server receiving the join request. 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 Riikonen [Page 42]
Internet Draft 28 June 2000 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 Riikonen [Page 43]
Internet Draft 28 June 2000 16 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 17 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 Riikonen [Page 44]
Internet Draft 28 June 2000 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 18 SILC_COMMAND_CMODE Max Arguments: 6 Arguments: (1) <Channel ID> (2) <channel mode mask> (3) [<user limit>] (4) [<passphrase>] (5) [<Client ID>] (6) [<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 Riikonen [Page 45]
Internet Draft 28 June 2000 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, Riikonen [Page 46]
Internet Draft 28 June 2000 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 Riikonen [Page 47]
Internet Draft 28 June 2000 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_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. Riikonen [Page 48]
Internet Draft 28 June 2000 0x0200 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 Riikonen [Page 49]
Internet Draft 28 June 2000 19 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 20 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. Riikonen [Page 50]
Internet Draft 28 June 2000 Status messages: SILC_STATUS_OK SILC_STATUS_ERR_NOT_REGISTERED SILC_STATUS_ERR_NO_SERVER_PRIV 21 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 22 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: Riikonen [Page 51]
Internet Draft 28 June 2000 Max Arguments: 1 Arguments: (1) <Status Payload> This command replies only with Status Payload. Status messages: SILC_STATUS_OK SILC_STATUS_ERR_NOT_REGISTERED SILC_STATUS_ERR_NO_SERVER_PRIV 23 SILC_COMMAND_SILCOPER Max Arguments: 2 Arguments: (1) <username> (2) <authentication 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 Riikonen [Page 52]
Internet Draft 28 June 2000 SILC_STATUS_ERR_BAD_PASSWORD SILC_STATUS_ERR_AUTH_FAILED 24 SILC_COMMAND_LEAVE Max Arguments: 1 Arguments: (1) <Channel ID> This command is used by client to leave a channel the client is joined to. 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 25 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. Riikonen [Page 53]
Internet Draft 28 June 2000 Reply messages to the command: Max Arguments: 2 Arguments: (1) <Status Payload> (2) <name list> This command replies with the comma separated list of users on the channel. Status messages: SILC_STATUS_OK SILC_STATUS_ERR_NOT_REGISTERED SILC_STATUS_ERR_NOT_ENOUGH_PARAMS SILC_STATUS_ERR_TOO_MANY_PARAMS SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID SILC_STATUS_ERR_BAD_CHANNEL_ID SILC_STATUS_ERR_NO_CHANNEL_ID SILC_STATUS_ERR_NOT_ON_CHANNEL 26 - 254 Currently undefined commands. 255 SILC_COMMAND_MAX Reserved command. This must not be sent. 5.3 SILC Command Status Types 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). 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status Message | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: SILC Command Status Payload Riikonen [Page 54]
Internet Draft 28 June 2000 o Status Message (2 bytes) - Indicates the status message. All Status messages are described in the next section. 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. 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. Riikonen [Page 55]
Internet Draft 28 June 2000 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_BAD_CLIENT_ID "Bad Client ID". Client ID provided were erroneous. 20 SILC_STATUS_ERR_BAD_CHANNEL_ID "Bad Channel ID". Channel ID provided were erroneous. 21 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID "No such Client ID". Client ID provided does not exist. Riikonen [Page 56]
Internet Draft 28 June 2000 22 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID "No such Channel ID". Channel ID provided does not exist. 23 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. 24 SILC_STATUS_ERR_NOT_ON_CHANNEL "You are not on that channel". The command were specified for client user is not currently on. 25 SILC_STATUS_ERR_USER_ON_CHANNEL "User already on channel". User were invited on channel they already are on. 26 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. 27 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS "Not enough parameters". Command requires more parameters than provided. 28 SILC_STATUS_ERR_TOO_MANY_PARAMS "Too many parameters". Too many parameters were provided for the command. 29 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. 30 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. Riikonen [Page 57]
Internet Draft 28 June 2000 31 SILC_STATUS_ERR_BAD_PASSWORD "Cannot join channel. Incorrect password". Password provided for channel were not accepted. 32 SILC_STATUS_ERR_CHANNEL_IS_FULL "Cannot join channel. Channel is full". The channel is full and client cannot be joined to it. 33 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. 34 SILC_STATUS_ERR_BANNED_FROM_CHANNEL "Cannot join channel. You have been banned". The client has been banned from the channel. 35 SILC_STATUS_ERR_UNKNOWN_MODE "Unknown mode". Mode provided by the client were unknown to the server. 36 SILC_STATUS_ERR_NOT_YOU "Cannot change mode for other users". User tried to change someone else's mode. 37 SILC_STATUS_ERR_NO_CHANNEL_PRIV "Permission denied. You are not channel operator". Command may be executed only by channel operator. 38 SILC_STATUS_ERR_NO_SERVER_PRIV "Permission denied. You are not server operator". Command may be executed only by server operator. 39 SILC_STATUS_ERR_NO_ROUTER_PRIV "Permission denied. You are not SILC operator". Command may be executed only by router (SILC) operator. 40 SILC_STATUS_ERR_BAD_NICKNAME "Bad nickname". Nickname requested contained illegal characters Riikonen [Page 58]
Internet Draft 28 June 2000 or were malformed. 41 SILC_STATUS_ERR_BAD_CHANNEL "Bad channel name". Channel requested contained illegal characters or were malformed. 42 SILC_STATUS_ERR_AUTH_FAILED "Authentication failed". The authentication data sent as argument were wrong and thus authentication failed. 6 Security Considerations Security is central to the design of this protocol, and these security considerations permeate the specification. 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. Riikonen [Page 59]
Internet Draft 28 June 2000 [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. 8 Author's Address Pekka Riikonen Kasarmikatu 11 A4 70110 Kuopio Finland EMail: priikone@poseidon.pspt.fi This Internet-Draft expires 28 Jan 2001 Riikonen [Page 60]
