X-Git-Url: http://git.silcnet.org/gitweb/?p=website.git;a=blobdiff_plain;f=docs%2Fprotocol%2Fdraft-riikonen-silc-pp-09.txt;fp=docs%2Fprotocol%2Fdraft-riikonen-silc-pp-09.txt;h=b9499aebcf9148ccee70c463b25394d1d6195122;hp=0000000000000000000000000000000000000000;hb=4deb84ef17e789147fa9f7f35a302c5a38999817;hpb=4c0f02a06b6cd767a24041e0d37e95945e294623 diff --git a/docs/protocol/draft-riikonen-silc-pp-09.txt b/docs/protocol/draft-riikonen-silc-pp-09.txt new file mode 100644 index 0000000..b9499ae --- /dev/null +++ b/docs/protocol/draft-riikonen-silc-pp-09.txt @@ -0,0 +1,3307 @@ + + + + + + +Network Working Group P. Riikonen +Internet-Draft +draft-riikonen-silc-pp-09.txt 15 January 2007 +Expires: 15 July 2007 + + + SILC Packet Protocol + + +Status of this Draft + + By submitting this Internet-Draft, each author represents that any + applicable patent or other IPR claims of which he or she is aware + have been or will be disclosed, and any of which he or she becomes + aware will be disclosed, in accordance with Section 6 of BCP 79. + + Internet-Drafts are working documents of the Internet Engineering + Task Force (IETF), its areas, and its working groups. Note that + other groups may also distribute working documents as Internet- + Drafts. Internet-Drafts are draft documents valid for a maximum of + six months and may be updated, replaced, or obsoleted by other + documents at any time. It is inappropriate to use Internet-Drafts as + reference material or to cite them other than as "work in progress". + + The list of current Internet-Drafts can be accessed at + http://www.ietf.org/1id-abstracts.html + The list of Internet-Draft Shadow Directories can be accessed at + http://www.ietf.org/shadow.html. + + + +Abstract + + This memo describes a Packet Protocol used in the Secure Internet Live + Conferencing (SILC) protocol, specified in the Secure Internet Live + Conferencing, Protocol Specification [SILC1]. This protocol describes + the packet types and packet payloads which defines the contents of the + packets. The protocol provides secure binary packet protocol that + assures that the contents of the packets are secured and authenticated. + + + + + + + + + + + + +Riikonen [Page 1] + +Internet Draft 15 January 2007 + + +Table of Contents + + 1 Introduction .................................................. 3 + 1.1 Requirements Terminology .................................. 4 + 2 SILC Packet Protocol .......................................... 4 + 2.1 SILC Packet ............................................... 4 + 2.2 SILC Packet Header ........................................ 5 + 2.3 SILC Packet Types ......................................... 8 + 2.3.1 SILC Packet Payloads ................................ 15 + 2.3.2 Generic payloads .................................... 16 + 2.3.2.1 ID Payload .................................. 16 + 2.3.2.2 Argument Payload ............................ 17 + 2.3.2.3 Argument List Payload ....................... 17 + 2.3.2.4 Channel Payload ............................. 18 + 2.3.2.5 Public Key Payload .......................... 19 + 2.3.2.6 Message Payload ............................. 20 + 2.3.3 Disconnect Payload .................................. 23 + 2.3.4 Success Payload ..................................... 24 + 2.3.5 Failure Payload ..................................... 25 + 2.3.6 Reject Payload ...................................... 25 + 2.3.7 Notify Payload ...................................... 26 + 2.3.8 Error Payload ....................................... 35 + 2.3.9 Channel Message Payload ............................. 35 + 2.3.10 Channel Key Payload ................................ 36 + 2.3.11 Private Message Payload ............................ 38 + 2.3.12 Private Message Key Payload ........................ 38 + 2.3.13 Command Payload .................................... 40 + 2.3.14 Command Reply Payload .............................. 41 + 2.3.15 Connection Auth Request Payload .................... 41 + 2.3.16 New ID Payload ..................................... 42 + 2.3.17 New Client Payload ................................. 43 + 2.3.18 New Server Payload ................................. 44 + 2.3.19 New Channel Payload ................................ 45 + 2.3.20 Key Agreement Payload .............................. 45 + 2.3.21 Resume Router Payload .............................. 47 + 2.3.22 File Transfer Payload .............................. 47 + 2.3.23 Resume Client Payload .............................. 48 + 2.3.24 Acknowledgement Payload ............................ 50 + 2.4 SILC ID Types ............................................. 50 + 2.5 Packet Encryption And Decryption .......................... 51 + 2.5.1 Normal Packet Encryption And Decryption ............. 51 + 2.5.2 Channel Message Encryption And Decryption ........... 52 + 2.5.3 Private Message Encryption And Decryption ........... 53 + 2.6 Packet MAC Generation ..................................... 53 + 2.7 Packet Padding Generation ................................. 54 + 2.8 Packet Compression ........................................ 54 + 2.9 Packet Sending ............................................ 55 + 2.10 Packet Reception ......................................... 55 + + + +Riikonen [Page 2] + +Internet Draft 15 January 2007 + + + 2.11 Packet Routing ........................................... 55 + 2.12 Packet Broadcasting ...................................... 57 + 3 Security Considerations ....................................... 57 + 4 References .................................................... 57 + 5 Author's Address .............................................. 59 + 6 Full Copyright Statement ...................................... 59 + +List of Figures + + Figure 1: Typical SILC Packet + Figure 2: SILC Packet Header + Figure 3: ID Payload + Figure 4: Argument Payload + Figure 5: Argument List Payload + Figure 6: Channel Payload + Figure 7: Public Key Payload + Figure 8: Message Payload + Figure 9: Disconnect Payload + Figure 10: Success Payload + Figure 11: Failure Payload + Figure 12: Reject Payload + Figure 13: Notify Payload + Figure 14: Error Payload + Figure 15: Channel Key Payload + Figure 16: Private Message Key Payload + Figure 17: Command Payload + Figure 18: Connection Auth Request Payload + Figure 19: New Client Payload + Figure 20: New Server Payload + Figure 21: Key Agreement Payload + Figure 22: Resume Router Payload + Figure 23: File Transfer Payload + Figure 24: Resume Client Payload + + +1. Introduction + + This document describes a Packet Protocol used in the Secure Internet + Live Conferencing (SILC) protocol specified in the Secure Internet Live + Conferencing, Protocol Specification [SILC1]. This protocol describes + the packet types and packet payloads which defines the contents of the + packets. The protocol provides secure binary packet protocol that + assures that the contents of the packets are secured and authenticated. + The packet protocol is designed to be compact to avoid unnecessary + overhead as much as possible. This makes the SILC suitable also in + environment of low bandwidth requirements such as mobile networks. All + packet payloads can also be compressed to further reduce the size of + the packets. + + + +Riikonen [Page 3] + +Internet Draft 15 January 2007 + + + All packets in SILC network are always encrypted and their integrity + is assured by computed MACs. The protocol defines several packet types + and packet payloads. Each packet type usually has a specific packet + payload that actually defines the contents of the packet. Each packet + also includes a default SILC Packet Header that provides sufficient + information about the origin and the destination of the packet. + + +1.1 Requirements Terminology + + The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED, + MAY, and OPTIONAL, when they appear in this document, are to be + interpreted as described in [RFC2119]. + + +2 SILC Packet Protocol + +2.1 SILC Packet + + SILC packets deliver messages from sender to receiver securely by + encrypting important fields of the packet. The packet consists of + default SILC Packet Header, Padding, Packet Payload data, and, packet + MAC. + + The following diagram illustrates typical SILC packet. + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + | n bytes | 1 - n bytes | n bytes | n bytes + | SILC Header | Padding | Data Payload | MAC + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + Figure 1: Typical SILC Packet + + + SILC Header is always the first part of the packet and its purpose + is to provide information about the packet. It provides for example + the packet type, origin of the packet and the destination of the packet. + The header is variable in length. See the following section for + description of SILC Packet header. Packets without SILC header or + with malformed SILC header MUST be dropped. + + Padding follows the packet header. The purpose of the padding is to + make the packet multiple by eight (8) or by the block size of the + cipher used in the encryption, which ever is larger. The maximum + length of padding is currently 128 bytes. The padding is always + encrypted. The padding is applied always, even if the packet is + not encrypted. See the section 2.7 Padding Generation for more + detailed information. + + + +Riikonen [Page 4] + +Internet Draft 15 January 2007 + + + Data payload area follows padding and it is the actual data of the + packet. The packet data is the packet payloads defined in this + protocol. The data payload area is always encrypted. + + The last part of SILC packet is the packet MAC that assures the + integrity of the packet. See the section 2.6 Packet MAC Generation + for more information. If compression is used the compression is + always applied before encryption. + + All fields in all packet payloads are always in MSB (most significant + byte first) order. + + +2.2 SILC Packet Header + + The SILC packet header is applied to all SILC packets and it is + variable in length. The purpose of SILC Packet header is to provide + detailed information about the packet. The receiver of the packet + uses the packet header to parse the packet and gain other relevant + parameters of the packet. + + The following diagram represents the SILC packet header. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Payload Length | Flags | Packet Type | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Pad Length | RESERVED | Source ID Len | Dest ID Len | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Src ID Type | | + +-+-+-+-+-+-+-+-+ + + | | + ~ Source ID ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Dst ID Type | | + +-+-+-+-+-+-+-+-+ + + | | + ~ Destination ID ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 2: SILC Packet Header + + o Payload Length (2 bytes) - Indicates the length of the + packet not including the padding of the packet. + + + + +Riikonen [Page 5] + +Internet Draft 15 January 2007 + + + o Flags (1 byte) - Indicates flags to be used in packet + processing. Several flags may be set by ORing the flags + together. + + The following flags are reserved for this field: + + + No flags 0x00 + + In this case the field is ignored. + + + Private Message Key 0x01 + + Indicates that the packet data MUST include private + message that is encrypted using private key set by + client. Servers does not know this key and cannot + decrypt the payload, but simply passes it along. See + section 2.5.3 Private Message Encryption And Decryption + for more information. + + + List 0x02 + + Indicates that the packet consists of list of + packet payloads indicated by the Packet Type field. + The payloads are added one after the other. Note that + there are packet types that must not be used as + list. Parsing of list packet is done by calculating + the length of each payload and parsing them one by + one. + + + Broadcast 0x04 + + Marks the packet to be broadcasted. Client and normal + server cannot send broadcast packets. Only router server + may send broadcast packet. The router receiving of packet + with this flag set MUST send (broadcast) the packet to + its primary route. If router has several router connections + the packet may be sent only to the primary route. See + section 2.12 Packet Broadcasting for description of + packet broadcasting. + + + Compressed 0x08 + + Marks that the payload of the packet is compressed. + + + +Riikonen [Page 6] + +Internet Draft 15 January 2007 + + + The sender of the packet marks this flag when it + compresses the payload, and any server or router + en route to the recipient MUST NOT unset this flag. + See section 2.8 Packet Compression for description of + packet compressing. + + + Acknowledgement 0x10 + + Marks that the packet needs to be acknowledged by the + recipient. The ACK packet MUST NOT have this flag set. + The acknowledgement packet is SILC_PACKET_ACK packet. + If the packet is not acknowledged the packet may be + retransmitted. This flag is especially useful when + using UDP/IP and SHOULD NOT be used with TCP/IP. The + flag MUST NOT be used with message packets. The + SILC_MESSAGE_FLAG_ACK can be used instead. Broadcast + packets MUST NOT set this flag. Retransmission + may use for example exponential backoff algorithm. + + + o Packet Type (1 byte) - Indicates the type of the packet. + Receiver uses this field to parse the packet. See section + 2.3 SILC Packets for list of defined packet types. + + o Pad Length (1 byte) - Indicates the length of the padding + applied after the SILC Packet header. Maximum length for + padding is 128 bytes. + + o RESERVED (1 byte) - Reserved field and must include a + zero (0) value. + + o Source ID Length (1 byte) - Indicates the length of the + Source ID field in the header, not including this or any + other fields. + + o Destination ID Length (1 byte) - Indicates the length of the + Destination ID field in the header, not including this or + any other fields. + + o Src ID Type (1 byte) - Indicates the type of ID in the + Source ID field. See section 2.4 SILC ID Types for + defined ID types. + + o Source ID (variable length) - The actual source ID that + indicates which is the original sender of the packet. + + o Dst ID Type (1 byte) - Indicates the type of ID in the + + + +Riikonen [Page 7] + +Internet Draft 15 January 2007 + + + Destination ID field. See section 2.4 SILC ID Types for + defined ID types. + + o Destination ID (variable length) - The actual destination + ID that indicates which is the end receiver of the packet. + + + +2.3 SILC Packet Types + + SILC packet types defines the contents of the packet and it is used by + the receiver to parse the packet. The packet type is 8 bits in length. + The range for the packet types are from 0 - 255, where 0 is never sent and + 255 is currently reserved for future extensions and MUST NOT be defined to + any other purpose. Every SILC specification compliant implementation + SHOULD support all the following packet types. + + The below list of the SILC Packet types includes reference to the packet + payload as well. Packet payloads are the actual packet data area. Each + packet type defines packet payload which usually may only be sent with + the specific packet type. + + Most of the packets are packets that must be destined directly to entity + that is connected to the sender. It is not allowed, for example, for a + router to send SILC_PACKET_DISCONNECT packet to client that is not + directly connected to the router. However, there are some special packet + types that may be destined to some entity that the sender does not have + direct connection with. These packets are for example private message + packets, channel message packets, command packets and some other packets + that may be broadcasted in the SILC network. The following packet + desription list will define it separately if a packet is allowed to be + sent to indirectly connected entity. Other packets MUST NOT be sent or + accepted, if sent, to indirectly connected entities. + + Some packets MAY be sent as lists by adding the List flag to the Packet + Header and constructing multiple packet payloads one after the other. + When this is allowed it is separately defined in the following list. + Other packets MUST NOT be sent as list and the List flag MUST NOT be set. + + + List of SILC Packet types are defined as follows. + + 0 SILC_PACKET_NONE + + This type is reserved and it is never sent. + + + 1 SILC_PACKET_DISCONNECT + + + +Riikonen [Page 8] + +Internet Draft 15 January 2007 + + + This packet is sent to disconnect the remote end. Reason of + the disconnection is sent inside the packet payload. + + Payload of the packet: See section 2.3.3 Disconnect Payload + + + 2 SILC_PACKET_SUCCESS + + This packet is sent upon successful execution of a protocol. + The status of the success is sent in the packet payload. + + Payload of the packet: See section 2.3.4 Success Payload + + + 3 SILC_PACKET_FAILURE + + This packet is sent upon failure of a protocol. The status + of the failure is sent in the packet payload. + + Payload of the packet: See section 2.3.5 Failure Payload + + + 4 SILC_PACKET_REJECT + + This packet MAY be sent upon rejection of a protocol. The + status of the rejection is sent in the packet payload. + + Payload of the packet: See section 2.3.6 Reject Payload + + + 5 SILC_PACKET_NOTIFY + + This packet is used to send notify message. The packet is + usually sent between server and client, but also between + server and router. Client MUST NOT send this packet. Server + MAY destine this packet to channel as well when the packet is + distributed to all clients on the channel. This packet MAY + be sent as list. + + Payload of the packet: See section 2.3.7 Notify Payload. + + + 6 SILC_PACKET_ERROR + + This packet is sent when an error occurs. Server MAY + send this packet. Client MUST NOT send this packet. The + client MAY entirely ignore the packet, however, server is + most likely to take action anyway. This packet MAY be sent + + + +Riikonen [Page 9] + +Internet Draft 15 January 2007 + + + to entity that is indirectly connected to the sender. + + Payload of the packet: See section 2.3.8 Error Payload. + + + 7 SILC_PACKET_CHANNEL_MESSAGE + + This packet is used to send messages to channels. The packet + includes Channel ID of the channel and the actual message to + the channel. Messages sent to the channel are always protected + by channel specific keys. This packet MAY be sent to entity + that is indirectly connected to the sender. + + Payload of the packet: See section 2.3.9 Channel Message + Payload + + + 8 SILC_PACKET_CHANNEL_KEY + + This packet is used to distribute new key for particular + channel when server generates it. Each channel has their own + independent keys that is used to protect the traffic on the + channel. It is also possible to use channel private keys that + are not server generated. In this case this packet is not used. + Client MUST NOT send this packet. This packet MAY be sent to + entity that is indirectly connected to the sender. + + Payload of the packet: See section 2.3.10 Channel Key Payload + + + 9 SILC_PACKET_PRIVATE_MESSAGE + + This packet is used to send private messages from client + to another client. By default, private messages are protected + by session keys established by normal key exchange protocol. + However, it is possible to use specific key to protect private + messages. See [SILC1] for private message key generation. + This packet MAY be sent to entity that is indirectly connected + to the sender. + + Payload of the packet: See section 2.3.11 Private Message + Payload + + + 10 SILC_PACKET_PRIVATE_MESSAGE_KEY + + This packet is OPTIONAL and sender of the packet can indicate + that a private message key should be used in private message + + + +Riikonen [Page 10] + +Internet Draft 15 January 2007 + + + communication. The actual key material is not sent in this + packet but must be either static or pre-shared key. The + receiver of the packet is considered to be the responder + when processing the static or pre-shared key material as + defined in [SILC1] and [SILC3] for private message keys. + This packet MAY be sent to entity that is indirectly connected + to the sender. + + Payload of the packet: See section 2.3.12 Private Message + Key Payload + + + 11 SILC_PACKET_COMMAND + + This packet is used to send commands from client to server. + Server MAY send this packet to other servers as well. All + commands are listed in their own section SILC Command Types + in [SILC4]. The contents of this packet is command specific. + This packet MAY be sent to entity that is indirectly connected + to the sender. + + Payload of the packet: See section 2.3.13 Command Payload + + + 12 SILC_PACKET_COMMAND_REPLY + + This packet is sent as reply to the SILC_PACKET_COMMAND packet. + The contents of this packet is command specific. This packet + MAY be sent to entity that is indirectly connected to the + sender. This packet MAY be sent as list. + + Payload of the packet: See section 2.3.14 Command Reply + Payload and section 2.3.13 Command + Payload + + + 13 SILC_PACKET_KEY_EXCHANGE + + This packet is used to start SILC Key Exchange Protocol, + described in detail in [SILC3]. + + Payload of the packet: Payload of this packet is described + in the section SILC Key Exchange + Protocol and its sub sections in + [SILC3]. + + + 14 SILC_PACKET_KEY_EXCHANGE_1 + + + +Riikonen [Page 11] + +Internet Draft 15 January 2007 + + + This packet is used as part of the SILC Key Exchange Protocol. + + Payload of the packet: Payload of this packet is described + in the section SILC Key Exchange + Protocol and its sub sections in + [SILC3]. + + + 15 SILC_PACKET_KEY_EXCHANGE_2 + + This packet is used as part of the SILC Key Exchange Protocol. + + Payload of the packet: Payload of this packet is described + in the section SILC Key Exchange + Protocol and its sub sections in + [SILC3]. + + + 16 SILC_PACKET_CONNECTION_AUTH_REQUEST + + This packet is used to request an authentication method to + be used in the SILC Connection Authentication Protocol. If + initiator of the protocol does not know the mandatory + authentication method this packet MAY be used to determine it. + The party receiving this payload SHOULD respond with the same + packet including the mandatory authentication method. + + Payload of the packet: See section 2.3.15 Connection Auth + Request Payload + + + 17 SILC_PACKET_CONNECTION_AUTH + + This packet is used to start and perform the SILC Connection + Authentication Protocol. This protocol is used to authenticate + the connecting party. The protocol is described in detail in + [SILC3]. + + Payload of the packet: Payload of this packet is described + in the section SILC Authentication + Protocol and it sub sections in [SILC]. + + + 18 SILC_PACKET_NEW_ID + + This packet is used to distribute new IDs from server to + router and from router to all other routers in SILC network. + This is used when for example new client is registered to + + + +Riikonen [Page 12] + +Internet Draft 15 January 2007 + + + SILC network. The newly created IDs of these operations are + distributed by this packet. Only server may send this packet, + however, client MUST be able to receive this packet. This + packet MAY be sent to entity that is indirectly connected + to the sender. This packet MAY be sent as list. + + Payload of the packet: See section 2.3.16 New ID Payload + + + 19 SILC_PACKET_NEW_CLIENT + + This packet is used by client to register itself to the + SILC network. This is sent after key exchange and + authentication protocols has been completed. Client sends + various information about itself in this packet to the server. + + Payload of the packet: See section 2.3.17 New Client Payload + + + 20 SILC_PACKET_NEW_SERVER + + This packet is used by server to register itself to the + SILC network. This is sent after key exchange and + authentication protocols has been completed. Server sends + this to the router it connected to, or, if router was + connecting, to the connected router. Server sends its + Server ID and other information in this packet. The client + MUST NOT send or receive this packet. + + Payload of the packet: See section 2.3.18 New Server Payload + + + 21 SILC_PACKET_NEW_CHANNEL + + This packet is used to notify routers about newly created + channel. Channels are always created by the router and it MUST + notify other routers about the created channel. Router sends + this packet to its primary route. Client MUST NOT send this + packet. This packet MAY be sent to entity that is indirectly + connected to the sender. This packet MAY be sent as list. + + Payload of the packet: See section 2.3.19 New Channel Payload + + + 22 SILC_PACKET_REKEY + + This packet is used to indicate that re-key must be performed + for session keys. See section Session Key Regeneration in + + + +Riikonen [Page 13] + +Internet Draft 15 January 2007 + + + [SILC1] for more information. This packet does not have + a payload. + + + 23 SILC_PACKET_REKEY_DONE + + This packet is used to indicate that re-key is performed and + new keys must be used hereafter. This packet does not have a + payload. + + + 24 SILC_PACKET_HEARTBEAT + + This packet is used by clients, servers and routers to keep the + connection alive. It is RECOMMENDED that all servers implement + keepalive actions and perform it to both direction in a link. + This packet does not have a payload. + + + 25 SILC_PACKET_KEY_AGREEMENT + + This packet is used by clients to request key negotiation + between another client in the SILC network. If the negotiation + is started it is performed using the SKE protocol. The result of + the negotiation, the secret key material, can be used for + example as private message key. The server and router MUST NOT + send this packet. + + Payload of the packet: See section 2.3.20 Key Agreement Payload + + + 26 SILC_PACKET_RESUME_ROUTER + + This packet is used during backup router protocol when the + original primary router of the cell comes back online and wishes + to resume the position as being the primary router of the cell. + + Payload of the packet: See section 2.3.21 Resume Router Payload + + + 27 SILC_PACKET_FTP + + This packet is used to perform an file transfer protocol in the + SILC session with some entity in the network. The packet is + multi purpose. The packet is used to tell other entity in the + network that the sender wishes to perform an file transfer + protocol. The packet is also used to actually tunnel the + file transfer protocol stream. The file transfer protocol + + + +Riikonen [Page 14] + +Internet Draft 15 January 2007 + + + stream is always protected with the SILC binary packet protocol. + + Payload of the packet: See section 2.3.22 File Transfer Payload + + + 28 SILC_PACKET_RESUME_CLIENT + + This packet is used to resume a client back to the network + after it has been detached. A client is able to detach from + the network but the client is still valid client in the network. + The client may then later resume its session back by sending + this packet to a server. Routers also use this packet to notify + other routers in the network that the detached client has resumed. + + Payload of the packet: See section 2.3.23 Resume Client Payload + + + 29 SILC_PACKET_ACK + + This packet is used to acknowledge a packet that had the + Acknowledgement packet flag set. + + Payload of the packet: See section 2.3.24 Acknowledgement + Payload + + + 30 - 199 + + Currently undefined commands. + + + 200 - 254 + + These packet types are reserved for private use and they will + not be defined by this document. + + + 255 SILC_PACKET_MAX + + This type is reserved for future extensions and currently it + MUST NOT be sent. + + +2.3.1 SILC Packet Payloads + + All payloads resides in the main data area of the SILC packet. However + all payloads MUST be at the start of the data area after the SILC + packet header and padding. All fields in the packet payload are always + + + +Riikonen [Page 15] + +Internet Draft 15 January 2007 + + + encrypted, as they reside in the data area of the packet which is + always encrypted. Most of the payloads may only be sent with specific + packet type which is defined in the description of the payload. + + There are some other payloads in SILC as well. However, they are not + common in the sense that they could be sent at any time. These payloads + are not described in this section. These are payloads such as SILC + Key Exchange payloads and so on. These are described in [SILC1], + [SILC3] and [SILC4]. + + +2.3.2 Generic payloads + + This section describes generic payloads that are not associated to any + specific packet type. They can be used for example inside some other + packet payload. + + +2.3.2.1 ID Payload + + This payload can be used to send an ID. ID's are variable in length + thus this payload provides a way to send variable length ID. + + The following diagram represents the ID Payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ID Type | ID Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ ID Data ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 3: ID Payload + + + o ID Type (2 bytes) - Indicates the type of the ID. See + section 2.4 SILC ID Types for list of defined ID types. + + o ID Length (2 bytes) - Length of the ID Data area not + including the length of any other fields in the payload. + + o ID Data (variable length) - The actual ID data. The encoding + of the ID data is defined in section 2.4 SILC ID Types. + + + + + +Riikonen [Page 16] + +Internet Draft 15 January 2007 + + +2.3.2.2 Argument Payload + + Argument Payload is used to set arguments for any packet payload that + need and support arguments, such as commands. Number of arguments + associated with a packet MUST be indicated by the packet payload which + need the arguments. Argument Payloads MUST always reside right after + the packet payload needing the arguments. Incorrect amount of argument + payloads MUST cause rejection of the packet. + + The following diagram represents the Argument Payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Data Length | Argument Type | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Argument Data ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 4: Argument Payload + + + o Data Length (2 bytes) - Length of the Argument Data field + not including the length of any other field in the payload. + + o Argument Type (1 byte) - Indicates the type of the argument. + Every argument can have a specific type that are defined + by the packet payload needing the argument. For example + every command specify a number for each argument that may be + associated with the command. By using this number the receiver + of the packet knows what type of argument this is. If there is + no specific argument type this field is set to zero (0) value. + + o Argument Data (variable length) - Argument data. + + +2.3.2.3 Argument List Payload + + Argument List Payload is a list of Argument Payloads appended one + after the other. The number of arguments is indicated in the + payload. + + The following diagram represents the Argument List Payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + + + +Riikonen [Page 17] + +Internet Draft 15 January 2007 + + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Argument Nums | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Argument Payloads ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 5: Argument List Payload + + + o Argument Nums (2 bytes) - Indicates the number of Argument + Payloads. If zero (0) value is found in this field no + arguments are present. + + o Argument Payloads (variable length) - The Argument Payloads + appended one after the other. The payloads can be decoded + since the length of the payload is indicated in each of + the Argument Payload. + + + + + +2.3.2.4 Channel Payload + + Generic Channel Payload may be used to send information about a channel, + its name, the Channel ID and a mode. + + The following diagram represents the Channel Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Channel Name Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Channel Name ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Channel ID Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Channel ID ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Mode Mask | + + + +Riikonen [Page 18] + +Internet Draft 15 January 2007 + + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 6: New Channel Payload + + + o Channel Name Length (2 bytes) - Length of the Channel Name + field. + + o Channel Name (variable length) - The name of the channel. + + o Channel ID Length (2 bytes) - Length of the Channel ID field. + + o Channel ID (variable length) - The encoded Channel ID. + + o Mode Mask (4 bytes) - A mode. This can be the mode of the + channel but it can also be the mode of a client on the + channel. The contents of this field is dependent of the + usage of this payload. The usage is defined separately + when this payload is used. This is a 32 bit MSB first value. + + + + + + +2.3.2.5 Public Key Payload + + Generic Public Key Payload may be used to send different type of + public keys and certificates. + + The following diagram represents the Public Key Payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Public Key Length | Public Key Type | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Public Key (or certificate) ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 7: Public Key Payload + + + o Public Key Length (2 bytes) - The length of the Public Key + (or certificate) field, not including any other field. + + + + +Riikonen [Page 19] + +Internet Draft 15 January 2007 + + + o Public Key Type (2 bytes) - The public key (or certificate) + type. This field indicates the type of the public key in + the packet. See the [SILC3] for defined public key types. + + o Public Key (or certificate) (variable length) - The + encoded public key or certificate data. + + +2.3.2.6 Message Payload + + Generic Message Payload can be used to send messages in SILC. It + is used to send channel messages and private messages. + + The following diagram represents the Message Payload. + + (*) indicates that the field is not encrypted. + + + + + + + + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Message Flags | Message Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Message Data ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Padding Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Padding ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Initialization Vector * ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ MAC * ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + +Riikonen [Page 20] + +Internet Draft 15 January 2007 + + + Figure 8: Message Payload + + + o Message Flags (2 bytes) - Includes the Message Flags of the + message. The flags can indicate a reason or a purpose for + the message. The following Message Flags are defined: + + 0x0000 SILC_MESSAGE_FLAG_NONE + + No specific flags set. + + 0x0001 SILC_MESSAGE_FLAG_AUTOREPLY + + This message is an automatic reply to an earlier + received message. + + 0x0002 SILC_MESSAGE_FLAG_NOREPLY + + There should not be reply messages to this + message. + + 0x0004 SILC_MESSAGE_FLAG_ACTION + + The sender is performing an action and the message + is the indication of the action. + + 0x0008 SILC_MESSAGE_FLAG_NOTICE + + The message is for example an informational notice + type message. + + 0x0010 SILC_MESSAGE_FLAG_REQUEST + + This is a generic request flag to send request + messages. A separate document should define any + payloads associated to this flag. + + 0x0020 SILC_MESSAGE_FLAG_SIGNED + + This flag indicates that the message is signed + with sender's private key and thus can be verified + by the receiver using the sender's public key. A + separate document should define the detailed procedure + of the signing process and any associated payloads + for this flag. + + 0x0040 SILC_MESSAGE_FLAG_REPLY + + + + +Riikonen [Page 21] + +Internet Draft 15 January 2007 + + + This is a generic reply flag to send a reply to + previously received request. A separate document + should define any payloads associated to this flag. + + 0x0080 SILC_MESSAGE_FLAG_DATA + + This is a generic data flag, indicating that the + message includes some data which can be interpreted + in a specific way. Using this flag any kind of data + can be delivered inside message payload. A separate + document should define how this flag is interpreted + and define any associated payloads. + + 0x0100 SILC_MESSAGE_FLAG_UTF8 + + This flag indicates that the message is UTF-8 encoded + textual message. When sending text messages in SILC + this flag SHOULD be used. When this flag is used the + text sent as message MUST be UTF-8 encoded. + + 0x0200 SILC_MESSAGE_FLAG_ACK + + This flag indicates the sender requires the recpipient + to acknowledge the received message. This same flag + is used in the acknowledgement. A separate document + should define how the acknowledgement is performed. + + 0x0400 - 0x1000 RESERVED + + Reserved for future flags. + + 0x2000 - 0x8000 PRIVATE RANGE + + Private range for free use. + + o Message Length (2 bytes) - Indicates the length of the + Message Data field in the payload, not including any + other field. + + o Message Data (variable length) - The actual message data. + + o Padding Length (2 bytes) - Indicates the length of the + Padding field in the payload, not including any other + field. + + o Padding (variable length) - If this payload is used as + channel messages, the padding MUST be applied because + this payload is encrypted separately from other parts + + + +Riikonen [Page 22] + +Internet Draft 15 January 2007 + + + of the packet. If this payload is used as private + messages, the padding is present only when the payload + is encrypted with private message key. If encrypted + with session keys this field MUST NOT be present and the + Padding Length field includes a zero (0) value. The + padding SHOULD be random data. + + o Initialization Vector (variable length) - This field MUST + be present when this payload is used as channel messages. + The IV SHOULD be random data for each channel message. + + When encrypting private messages with session keys this + field MUST NOT be present. For private messages this field + is present only when encrypting with a static private + message key (pre-shared key). If randomly generated key + material is used this field MUST NOT be present. Also, + If Key Agreement (SKE) was used to negotiate fresh key + material for private message key this field MUST NOT be + present. See the section 4.6 in [SILC1] for more + information about IVs when encrypting private messages. + + This field includes the initialization vector used in message + encryption. It need to be used in the packet decryption + as well. Contents of this field depends on the encryption + algorithm and encryption mode. This field is not encrypted, + is not included in padding calculation and its length + equals to cipher's block size. This field is authenticated + by the message MAC. + + o MAC (variable length) - The MAC computed from the + Message Flags, Message Length, Message Data, Padding Length, + Padding and Initialization Vector fields in that order. + The MAC is computed after the payload is encrypted. This + is so called Encrypt-Then-MAC order; first encrypt, then + compute MAC from ciphertext. The MAC protects the integrity + of the Message Payload. Also, when used as channel messages + it is possible to have multiple private channel keys set, + and receiver can use the MAC to verify which of the keys + must be used in decryption. This field is not present + when encrypting private messages with session key. This + field is not encrypted. This field is authenticated by + the SILC packet MAC. + + +2.3.3 Disconnect Payload + + Disconnect payload is sent upon disconnection. Reason of the + disconnection is sent to the disconnected party in the payload. + + + +Riikonen [Page 23] + +Internet Draft 15 January 2007 + + + The payload may only be sent with SILC_PACKET_DISCONNECT packet. It + MUST NOT be sent in any other packet type. The following diagram + represents the Disconnect Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Status | | + +-+-+-+-+-+-+-+-+ + + | | + ~ Disconnect Message ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 9: Disconnect Payload + + o Status (1 byte) - Indicates the Status Type, defined in [SILC3] + for the reason of disconnection. + + o Disconnect Message (variable length) - Human readable UTF-8 + encoded string indicating reason of the disconnection. This + field MAY be omitted. + + +2.3.4 Success Payload + + Success payload is sent when some protocol execution is successfully + completed. The payload is simple; indication of the success is sent. + This may be any data, including binary or human readable data, and + it is protocol dependent. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Success Indication ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 10: Success Payload + + + o Success Indication (variable length) - Indication of + the success. This may be for example some flag that + indicates the protocol and the success status or human + readable success message. The true length of this + payload is available by calculating it from the SILC + + + +Riikonen [Page 24] + +Internet Draft 15 January 2007 + + + Packet Header. + + +2.3.5 Failure Payload + + This is opposite of Success Payload. Indication of failure of + some protocol is sent in the payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Failure Indication ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 11: Failure Payload + + + o Failure Indication (variable length) - Indication of + the failure. This may be for example some flag that + indicates the protocol and the failure status or human + readable failure message. The true length of this + payload is available by calculating it from the SILC + Packet Header. + + +2.3.6 Reject Payload + + This payload is sent when some protocol is rejected to be executed. + Other operations MAY send this as well that was rejected. The + indication of the rejection is sent in the payload. The indication + may be binary or human readable data and is protocol dependent. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Reject Indication ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 12: Reject Payload + + + o Reject Indication (variable length) - Indication of + the rejection. This maybe for example some flag that + + + +Riikonen [Page 25] + +Internet Draft 15 January 2007 + + + indicates the protocol and the rejection status or human + readable rejection message. The true length of this + payload is available by calculating it from the SILC + Packet Header. + + + +2.3.7 Notify Payload + + Notify payload is used to send notify messages. The payload is usually + sent from server to client and from server to router. It is also used + by routers to notify other routers in the network. This payload MAY also + be sent to a channel. Client MUST NOT send this payload. When this + packet is received by client it SHOULD process it. Servers and routers + MUST process notify packets. + + The payload may only be sent with SILC_PACKET_NOTIFY packet. It MUST + NOT be sent in any other packet type. The following diagram represents + the Notify Payload. + + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Notify Type | Payload Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Argument Nums | + +-+-+-+-+-+-+-+-+ + + Figure 13: Notify Payload + + + o Notify Type (2 bytes) - Indicates the type of the notify + message. + + o Payload Length (2 bytes) - Length of the entire Notify Payload + including any associated Argument Payloads. + + o Argument Nums (1 byte) - Indicates the number of Argument + Payloads associated to this payload. Notify types may define + arguments to be sent along the notify message. + + Following the list of currently defined notify types. The format for + notify arguments is same as in SILC commands described in [SILC4]. + Note that all IDs sent in arguments are sent inside ID Payload. Also + note that all strings sent as arguments MUST be UTF-8 [RFC3629] encoded, + unless otherwise defined. Also note that all public keys or + + + +Riikonen [Page 26] + +Internet Draft 15 January 2007 + + + certificates sent inside arguments are actually Public Key Payloads. + + + 0 SILC_NOTIFY_TYPE_NONE + + If no specific notify type apply for the notify message this type + MAY be used. + + Max Arguments: 1 + Arguments: (1) + + The is implementation specific free text string. + Receiver MAY ignore this message. + + + 1 SILC_NOTIFY_TYPE_INVITE + + Sent when an client is invited to a channel. This is also sent + when the invite list of the channel is changed. This notify type + is sent to local servers on the channel, but MUST NOT be sent + to clients on the channel. Router MUST broadcast this to its + primary router and to local servers on the channel. When a client + was directly invited to the channel this is also sent to that + client. In this case the packet is destined to the client. + + Max Arguments: 5 + Arguments: (1) (2) + (3) [] (4) [] + (5) [] + + The is the channel. The is the name + of the channel and is provided because the client which receives + this notify packet may not have a way to resolve the name of the + channel from the . The is the + Client ID which invited the client to the channel. The + is an argument of size of 1 byte where 0x00 means + adding a client to invite list, and 0x01 means deleting a client + from invite list. The , if present, indicates the + information to be added to or removed from the invite list. + The format is defined in [SILC4] with + SILC_COMMAND_INVITE command. When this notify is destined to + a client the and MUST NOT be sent. + When is used to announce information during server + connecting phase the argument type MUST be 0x03. See section + 4.2.1 in [SILC1] for more information. + + + 2 SILC_NOTIFY_TYPE_JOIN + + + +Riikonen [Page 27] + +Internet Draft 15 January 2007 + + + Sent when client has joined to a channel. The server MUST + distribute this type to the local clients on the channel and then + send it to its primary router. Note that, when router is joining + the client on behalf of normal server then router MUST send this + notify type locally and globally. The router or server receiving + the packet distributes this type to the local clients on the + channel and broadcast it to the network. This notify is sent + also to the client that joined the channel. + + Max Arguments: 2 + Arguments: (1) [] (2) + + The is the client that joined to the channel + indicated by the . + + + 3 SILC_NOTIFY_TYPE_LEAVE + + Sent when client has left a channel. The server must distribute + this type to the local clients on the channel and then send it + to its primary router. The router or server receiving the + packet distributes this type to the local clients on the channel + and broadcast it to the network. This notify MUST NOT be sent to + the leaving client. + + Max Arguments: 1 + Arguments: (1) + + The is the client which left the channel. + + + 4 SILC_NOTIFY_TYPE_SIGNOFF + + Sent when client signoff from SILC network. The server MUST + distribute this type to the local clients on the channel and + then send it to its primary router. The router or server + receiving the packet distributes this type to the local clients + on the channel and broadcast it to the network. This notify + MUST NOT be sent to the quitting client. The Destination ID + in the packet may be any ID depending to who it is destined. + + Max Arguments: 2 + Arguments: (1) (2) + + The is the client which left SILC network. The + is free text string indicating the reason of the + signoff. + + + + +Riikonen [Page 28] + +Internet Draft 15 January 2007 + + + 5 SILC_NOTIFY_TYPE_TOPIC_SET + + Sent when topic is set/changed on a channel. This type may be + sent only to the clients which are joined on the channel which + topic was just set or changed. The packet is destined to the + channel. + + Max Arguments: 2 + Arguments: (1) (2) + + The is the ID of the entity who set the topic. + It usually is Client ID but it can be Server ID and Channel ID + as well. + + + 6 SILC_NOTIFY_TYPE_NICK_CHANGE + + Sent when client changes nick on a channel. The server MUST + distribute this type only to the local clients on the channel + and then send it to its primary router. The router or server + receiving the packet distributes this type to the local clients + on the channel and broadcast it to the network. This packet is + destined directly to the sent entity. This MUST be sent to those + clients that are joined on same channels as the client that + changed the nickname. This notify MUST NOT be sent multiple + times to the same recipient. This notify MUST be sent also to + the client that changed the nickname. + + Max Arguments: 3 + Arguments: (1) (2) + (3) + + The is the old ID of the client which changed + the nickname. The is the new ID generated by + the change of the nickname. The is the new nickname. + Note that it is possible to send this notify even if the + nickname has not changed, but client ID was changed. + + + 7 SILC_NOTIFY_TYPE_CMODE_CHANGE + + Sent when channel mode has changed. This type MUST be sent only + to the clients which are joined on the channel which mode was + changed. This packet is destined to the channel. + + Max Arguments: 8 + Arguments: (1) (2) + (3) [] (4) <[hmac>] + + + +Riikonen [Page 29] + +Internet Draft 15 January 2007 + + + (5) [] (6) [] + (7) [] (8) [] + + The is the ID (usually Client ID but it can be + Server ID as well when the router is enforcing channel mode + change) of the entity which changed the mode. The + is the new mode mask of the channel. The client can safely + ignore the argument since the SILC_PACKET_CHANNEL_KEY + packet will force the new channel key change anyway. The + argument is important since the client is responsible of setting + the new HMAC and the hmac key into use. The is + the passphrase of the channel, if it was now set. The argument is sent when the founder mode on the + channel was set. All routers and servers that receive the packet + MUST save the founder's public key so that the founder can + reclaim the channel founder rights back for the channel on any + server in the network. The argument is present when + the user limit was set or changed on the channel. + + The is an Argument List Payload and it is used + to add and/or remove channel public keys from the channel. Also, + when announcing channel information between servers and routers + during connecting phase this argument includes the list of channel + public keys. To add a public key to channel public key list the + SILC_CMODE_CHANNEL_AUTH mode is set and the argument type is 0x00, + and the argument is the public key. To remove a public key from + the channel public key list the argument type is 0x01, and the + argument is the public key to be removed. If the mode + SILC_CMODE_CHANNEL_AUTH is unset (and was set earlier) all public + keys are removed at once. Implementation MAY add and remove + multiple public keys at the same time by including multiple + arguments to the Argument List Payload where each + argument is one Public Key Payload. When is used + to announce information during server connecting phase the + argument type MUST be 0x03. See section 4.2.1 in [SILC1] for + more information. + + + 8 SILC_NOTIFY_TYPE_CUMODE_CHANGE + + Sent when user mode on channel has changed. This type MUST be + sent only to the clients which are joined on the channel where + the target client is on. This packet is destined to the channel. + + Max Arguments: 4 + Arguments: (1) (2) + (3) (4) [] + + + + +Riikonen [Page 30] + +Internet Draft 15 January 2007 + + + The is the ID (usually Client ID but it can be + Server ID as well when the router is enforcing user's mode + change) of the entity which changed the mode. The + is the new mode mask of the channel. The + is the client which mode was changed. The + is the public key of the channel founder and may be sent only + when first time setting the channel founder mode using the + SILC_COMMAND_CUMODE command, and when sending this notify. + + + 9 SILC_NOTIFY_TYPE_MOTD + + Sent when Message of the Day (motd) is sent to a client. + + Max Arguments: 1 + Arguments: (1) + + The is the Message of the Day. This notify MAY be + ignored and is OPTIONAL. + + + 10 SILC_NOTIFY_TYPE_CHANNEL_CHANGE + + Sent when channel's ID has changed for a reason or another. + This is sent by normal server to the client. This can also be + sent by router to other server to force the Channel ID change. + The Channel ID MUST be changed to use the new one. When sent + to clients, this type MUST be sent only to the clients which are + joined on the channel. This packet is destined to the sent + entity. + + Max Arguments: 2 + Arguments: (1) (2) + + The is the channel's old ID and the is the new one that MUST replace the old one. + Server which receives this from router MUST re-announce the + channel to the router by sending SILC_PACKET_NEW_CHANNEL packet + with the new Channel ID. + + + 11 SILC_NOTIFY_TYPE_SERVER_SIGNOFF + + Sent when server quits SILC network. Those clients from this + server that are on channels must be removed from the channel. + This packet is destined to the sent entity. + + Max Arguments: 256 + + + +Riikonen [Page 31] + +Internet Draft 15 January 2007 + + + Arguments: (1) (n) [] [...] + + The is the server's ID. The rest of the arguments + are the Client IDs of the clients which are coming from this + server and are thus quitting the SILC network also. If the + maximum number of arguments are reached another + SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify packet MUST be sent. + When this notify packet is sent between routers the Client ID's + MAY be omitted. Server receiving the Client ID's in the payload + may use them directly to remove the client. + + + 12 SILC_NOTIFY_TYPE_KICKED + + Sent when a client has been kicked from a channel. This MUST + also be sent to the client which was kicked from the channel. + The client which was kicked from the channel MUST be removed + from the channel. The client MUST also be removed from channel's + invite list if it is explicitly added in the list. This packet + is destined to the channel. The router or server receiving the + packet distributes this type to the local clients on the channel + and broadcast it to the network. + + Max Arguments: 3 + Arguments: (1) (2) [] + (3) + + The is the client which was kicked from the channel. + The kicker may have set the string to indicate the + reason for the kicking. The is the kicker. + + + 13 SILC_NOTIFY_TYPE_KILLED + + Sent when a client has been killed from the network. This MUST + also be sent to the client which was killed from the network. + This notify MUST be sent to those clients which are joined on + same channels as the killed client. The client which was killed + MUST be removed from the network. This packet is destined + directly to the sent entity. The router or server receiving + the packet distributes this type to the local clients on the + channel and broadcast it to the network. The client MUST also + be removed from joined channels invite list if it is explicitly + added in the lists. This notify MUST NOT be sent multiple + times to same recipient. + + Max Arguments: 3 + Arguments: (1) (2) [] + + + +Riikonen [Page 32] + +Internet Draft 15 January 2007 + + + (3) + + The is the client which was killed from the network. + The killer may have set the string to indicate the + reason for the killing. The is the killer, which + may be client but also router server. + + + 14 SILC_NOTIFY_TYPE_UMODE_CHANGE + + Sent when user's mode in the SILC changes. This type is sent + only between routers as broadcast packet. + + Max Arguments: 2 + Arguments: (1) (2) + + The is the client which mode was changed. The + is the new mode mask. + + + 15 SILC_NOTIFY_TYPE_BAN + + Sent when the ban list of the channel is changed. This notify + type is sent to local servers on the channel, but MUST NOT be + sent to clients on the channel. Router MUST broadcast this to + its primary router and to local servers on the channel. + + Max Arguments: 3 + Arguments: (1) (2) [] + (3) [] + + The is the channel which ban list was changed. + The is an argument of size of 1 byte where 0x00 means + adding a client to ban list, and 0x01 means deleting a client + from ban list. The indicates the information to be + added to or removed from the ban list. The format + format is defined in [SILC4] with SILC_COMMAND_BAN command. + When is used to announce information during server + connecting phase the argument type MUST be 0x03. See section + 4.2.1 in [SILC1] for more information. + + + 16 SILC_NOTIFY_TYPE_ERROR + + Sent when an error occurs during processing some SILC procedure. + This is not used when error occurs during command processing, see + [SILC4] for more information about commands and command replies. + This type is sent directly to the sender of the packet whose + + + +Riikonen [Page 33] + +Internet Draft 15 January 2007 + + + packet caused the error. See [SILC1] for definition when this + type can be sent. + + Max Arguments: 256 + Arguments: (1) (n) [...] + + The is the error type defined in [SILC4]. Note + that same types are also used with command replies to indicate + the status of a command. Both commands and this notify type + share same status types. Rest of the arguments are status type + dependent and are specified with those status types that can be + sent currently inside this notify type in [SILC4]. The is size of 1 byte. + + + 17 SILC_NOTIFY_TYPE_WATCH + + Sent to indicate change in a watched user. Client can set + nicknames to be watched with SILC_COMMAND_WATCH command, and + receive notifications when they login to network, signoff from + the network or their user mode is changed. This notify type + is used to deliver these notifications. The notify type is + sent directly to the watching client. + + Max Arguments: 5 + Arguments: (1) (2) [] + (3) (4) [] + (5) [] + + The is the user's Client ID which is being watched, + and the is its nickname. If the client just + changed the nickname, then is the new nickname, but + the is the old client ID. The is the + user's current user mode. The can be same as the + Notify Payload's Notify Type, and is 16 bit MSB first order + value. If provided it may indicate the notify that occurred + for the client. If client logged in to the network the + MUST NOT be present. The MAY be + present, and it is the public key of the client being watched. + + Notify types starting from 16384 are reserved for private notify + message types. + + Router server which receives SILC_NOTIFY_TYPE_SIGNOFF, + SILC_NOTIFY_TYPE_SERVER_SIGNOFF, SILC_NOTIFY_TYPE_KILLED, + SILC_NOTIFY_TYPE_NICK_CHANGE and SILC_NOTIFY_TYPE_UMODE_CHANGE + MUST check whether someone in the local cell is watching the nickname + the client has, and send the SILC_NOTIFY_TYPE_WATCH notify to the + + + +Riikonen [Page 34] + +Internet Draft 15 January 2007 + + + watcher, unless the watched client in case has the user mode + SILC_UMODE_REJECT_WATCHING set. If the watcher client and the client + that was watched is same the notify SHOULD NOT be sent. + + +2.3.8 Error Payload + + Error payload is sent upon error in protocol. Error may occur in + various conditions when server sends this packet. Client MUST NOT + send this payload but MUST be able to accept it. However, client + MAY ignore the contents of the packet as server is going to take + action on the error anyway. However, it is recommended that the + client takes error packet seriously. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Error Message ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 14: Error Payload + + + o Error Message (variable length) - Human readable error + message. + + +2.3.9 Channel Message Payload + + Channel Message Payload is used to send message to channels, a group + of users. These messages can only be sent if client has joined to + some channel. Even though this packet is very common in SILC it + is still special packet. Some special handling on sending and + reception of channel message is required. + + Padding MUST be applied into this payload since the payload is + encrypted separately from other parts of the packet with the + channel specific key. Hence the requirement of the padding. + The packet MUST be made multiple by eight (8) or by the block + size of the cipher, which ever is larger. + + The SILC header in this packet is encrypted with the session key + of the next receiver of the packet. Nothing else is encrypted + with that key. Thus, the actual packet and padding to be + encrypted with the session key is SILC Header plus padding to it. + + + +Riikonen [Page 35] + +Internet Draft 15 January 2007 + + + Receiver of the the channel message packet is able to determine + the channel the message is destined to by checking the Destination + ID from the SILC Packet header which tells the destination channel. + The original sender of the packet is also determined by checking + the source ID from the header which tells the client which sent + the message. The Destination ID MUST be Channel ID in the SILC + Packet header. + + This packet use generic Message Payload as Channel Message Payload. + See section 2.3.2.6 for generic Message Payload. + + +2.3.10 Channel Key Payload + + All traffic in channels are protected by channel specific keys. + Channel Key Payload is used to distribute channel keys to all + clients on the particular channel. Channel keys are sent when + the channel is created, when new user joins to the channel and + whenever a user has left a channel. Server creates the new + channel key and distributes it to the clients by encrypting this + payload with the session key shared between the server and + the client. After that, client MUST start using the key received + in this payload to protect the traffic on the channel. + + The client which is joining to the channel receives its key in the + SILC_COMMAND_JOIN command reply message thus it is not necessary to + send this payload to the entity which sent the SILC_COMMAND_JOIN + command. + + Channel keys are cell specific thus every router in the cell have + to create a channel key and distribute it if any client in the + cell has joined to a channel. Channel traffic between cell's + are not encrypted using channel keys, they are encrypted using + normal session keys between two routers. Inside a cell, all + channel traffic is encrypted with the specified channel key. + Channel key SHOULD expire periodically, say, in one hour, in + which case new channel key is created and distributed. + + Note that, this packet is not used if SILC_CMODE_PRIVKEY mode is set + on channel. This means that channel uses channel private keys which + are not server generated. For this reason server cannot send this + packet as it does not know the key. + + The destination ID in the packet SHOULD be the entity to whom the + packet is sent. Using Channel ID as destination ID is not + necessary as the Channel ID is included in the Channel Key Payload. + + The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet. + + + +Riikonen [Page 36] + +Internet Draft 15 January 2007 + + + It MUST NOT be sent in any other packet type. The following diagram + represents the Channel Key Payload. + + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Channel ID Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Channel ID ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Cipher Name Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Cipher Name ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Channel Key Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Channel Key ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 15: Channel Key Payload + + + + o Channel ID Length (2 bytes) - Indicates the length of the + Channel ID field in the payload, not including any other + field. + + o Channel ID (variable length) - The Channel ID of the + channel. + + o Cipher Name Length (2 bytes) - Indicates the length of the + Cipher name field in the payload, not including any other + field. + + o Cipher Name (variable length) - Name of the cipher used + in the protection of channel traffic. This name is + initially decided by the creator of the channel but it + may change during the life time of the channel as well. + + o Channel Key Length (2 bytes) - Indicates the length of the + + + +Riikonen [Page 37] + +Internet Draft 15 January 2007 + + + Channel Key field in the payload, not including any other + field. + + o Channel Key (variable length) - The actual channel key + material. See [SILC1] on how to start using the key. + + +2.3.11 Private Message Payload + + Private Message Payload is used to send private message between + two clients. The messages are sent only to the specified user + and no other user inside SILC network is able to see the message. + + The message can be protected by the session key established by the + SILC Key Exchange Protocol. However, it is also possible to agree + to use a private message key to protect just the private messages. + It is for example possible to perform Key Agreement between two + clients. See section 2.3.20 Key Agreement Payload how to perform + key agreement. It is also possible to use static or pre-shared keys + to protect private messages. See the 2.3.12 Private Message Key + Payload and [SILC1] section 4.6 for detailed description for private + message key generation. + + If normal session key is used to protect the message, every server + between the sender client and the receiving client MUST decrypt the + packet and always re-encrypt it with the session key of the next + receiver of the packet. See section Client To Client in [SILC1]. + + When the private message key is used, and the Private Message Key + flag was set in the SILC Packet header no server or router en route + is able to decrypt or re-encrypt the packet. In this case only the + SILC Packet header is processed by the servers and routers en route. + Section Client To Client in [SILC1] gives example of this scheme. + + This packet use generic Message Payload as Private Message Payload. + See section 2.3.2.6 for generic Message Payload. + + +2.3.12 Private Message Key Payload + + This payload is OPTIONAL and can be used to indicate that a static + or pre-shared key should be used in the private message communication + to protect the messages. The actual key material has to be sent + outside the SILC network, or it has to be a static or pre-shared key. + The sender of this packet is considered to be the initiator and the + receiver the responder when processing the raw key material as + described in the section 4.6 in [SILC1] and in the section 2.3 in + [SILC3]. + + + +Riikonen [Page 38] + +Internet Draft 15 January 2007 + + + Note that it is also possible to use static or pre-shared keys in + client implementations without sending this packet. Clients may + naturally agree to use a key without sending any kind of indication + to each other. The key may be for example a long-living static key + that the clients has agreed to use at all times. Note that it is + also possible to agree to use private message key by performing + a Key Agreement. See the section 2.3.20 Key Agreement Payload. + + This payload may only be sent by client to another client. Server + MUST NOT send this payload. After sending this payload and setting the + key into use this payload the sender of private messages MUST set the + Private Message Key flag into the SILC Packet Header. + + The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY + packet. It MUST NOT be sent in any other packet type. The following + diagram represents the Private Message Key Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Cipher Name Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Cipher Name ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | HMAC Name Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ HMAC Name ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 16: Private Message Key Payload + + + + o Cipher Name Length (2 bytes) - Indicates the length of the + Cipher Name field in the payload, not including any other + field. + + o Cipher Name (variable length) - Name of the cipher to use + in the private message encryption. If this field does not + exist then the default cipher of the SILC protocol is used. + See the [SILC1] for defined ciphers. + + o HMAC Name Length (2 bytes) - Indicates the length of the + + + +Riikonen [Page 39] + +Internet Draft 15 January 2007 + + + HMAC Name field in the payload, not including any other + field. + + o HMAC Name (variable length) - Name of the HMAC to use + in the private message MAC computation. If this field does + not exist then the default HMAC of the SILC protocol is used. + See the [SILC1] for defined HMACs. + + +2.3.13 Command Payload + + Command Payload is used to send SILC commands from client to server. + Also server MAY send commands to other servers. The following diagram + represents the Command Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Payload Length | SILC Command | Arguments Num | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Command Identifier | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 17: Command Payload + + + o Payload Length (2 bytes) - Length of the entire command + payload including any command argument payloads associated + with this payload. + + o SILC Command (1 byte) - Indicates the SILC command. This MUST + be set to non-zero value. If zero (0) value is found in this + field the packet MUST be discarded. + + o Arguments Num (1 byte) - Indicates the number of arguments + associated with the command. If there are no arguments this + field is set to zero (0). The arguments MUST follow the + Command Payload. See section 2.3.2.2 for definition of the + Argument Payload. + + o Command Identifier (2 bytes) - Identifies this command at the + sender's end. The entity which replies to this command MUST + set the value found from this field into the Command Payload + used to send the reply to the sender. This way the sender + can identify which command reply belongs to which originally + sent command. What this field includes is implementation + issue but it is RECOMMENDED that wrapping counter value is + + + +Riikonen [Page 40] + +Internet Draft 15 January 2007 + + + used in the field. + + See [SILC4] for detailed description of different SILC commands, + their arguments and their reply messages. + + +2.3.14 Command Reply Payload + + Command Reply Payload is used to send replies to the commands. The + Command Reply Payload is identical to the Command Payload thus see + the 2.3.13 section for the payload specification. + + The entity which sends the reply packet MUST set the Command Identifier + field in the reply packet's Command Payload to the value it received + in the original command packet. + + See SILC Commands in [SILC4] for detailed description of different + SILC commands, their arguments and their reply messages. + + +2.3.15 Connection Auth Request Payload + + Client MAY send this payload to server to request the authentication + method that must be used in authentication protocol. If client knows + this information beforehand this payload is not necessary to be sent. + Server performing authentication with another server MAY also send + this payload to request the authentication method. If the connecting + server already knows this information this payload is not necessary + to be sent. + + Server receiving this request SHOULD reply with same payload sending + the mandatory authentication method. Algorithms that may be required + to be used by the authentication method are the ones already + established by the SILC Key Exchange protocol. See section Key + Exchange Start Payload in [SILC3] for detailed information. + + The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST + packet. It MUST NOT be sent in any other packet type. The following + diagram represents the Connection Auth Request Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Connection Type | Authentication Method | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 18: Connection Auth Request Payload + + + +Riikonen [Page 41] + +Internet Draft 15 January 2007 + + + o Connection Type (2 bytes) - Indicates the type of the + connection. The following connection types are defined: + + + 1 Client connection + 2 Server connection + 3 Router connection + + If any other type is found in this field the packet MUST be + discarded and the authentication MUST be failed. + + o Authentication Method (2 bytes) - Indicates the authentication + method to be used in the authentication protocol. The following + authentication methods are defined: + + 0 NONE (mandatory) + 1 password (mandatory) + 2 public key (mandatory) + + If any other type is found in this field the packet MUST be + discarded and the authentication MUST be failed. If this + payload is sent as request to receive the mandatory + authentication method this field MUST be set to zero (0), + indicating that receiver should send the mandatory + authentication method. The receiver sending this payload + to the requesting party, MAY also set this field to zero (0) + to indicate that authentication is not required. In this + case authentication protocol still MUST be started but + server is most likely to respond with SILC_PACKET_SUCCESS + immediately. + + +2.3.16 New ID Payload + + New ID Payload is a multipurpose payload. It is used to send newly + created ID's from clients and servers. When client connects to server + and registers itself to the server by sending SILC_PACKET_NEW_CLIENT + packet, server replies with this packet by sending the created ID for + the client. Server always creates the ID for the client. + + This payload is also used when server tells its router that new client + has registered to the SILC network. In this case the server sends + the Client ID of the client to the router. Similarly when router + distributes information to other routers about the client in the SILC + network this payload is used. + + Also, when server connects to router, router use this payload to inform + other routers about new server in the SILC network. However, every + + + +Riikonen [Page 42] + +Internet Draft 15 January 2007 + + + server (or router) creates their own ID's thus the ID distributed by + this payload is not created by the distributor in this case. Servers + create their own ID's. Server registers itself to the network by + sending SILC_PACKET_NEW_SERVER to the router it connected to. The case + is same when router connects to another router. + + This payload MUST NOT be used to send information about new channels. + New channels are always distributed by sending the dedicated + SILC_PACKET_NEW_CHANNEL packet. Client MUST NOT send this payload. + Both client and server (and router) MAY receive this payload. + + The packet use generic ID Payload as New ID Payload. See section + 2.3.2.1 for generic ID Payload. + + +2.3.17 New Client Payload + + When client is connected to the server, keys has been exchanged and + connection has been authenticated, client MUST register itself to the + server. Client's first packet after key exchange and authentication + protocols MUST be SILC_PACKET_NEW_CLIENT. This payload tells server all + the relevant information about the connected user. Server creates a new + client ID for the client when received this payload and sends it to the + client in New ID Payload. + + This payload sends username and real name of the user on the remote host + which is connected to the SILC server with SILC client. The server + creates the client ID according the information sent in this payload. + The nickname of the user becomes the nickname sent in this payload. + + The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It + MUST NOT be sent in any other packet type. The following diagram + represents the New Client Payload. + + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Username Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Username ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Real Name Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + + + +Riikonen [Page 43] + +Internet Draft 15 January 2007 + + + ~ Real Name ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 19: New Client Payload + + + o Username Length (2 bytes) - Length of the Username field. + + o Username (variable length) - The username of the user on + the host where connecting to the SILC server. + + o Real Name Length (2 bytes) - Length of the Real Name field. + + o Real Name (variable length) - The real name of the user + on the host where connecting to the SILC server. + + +2.3.18 New Server Payload + + This payload is sent by server when it has completed successfully both + key exchange and connection authentication protocols. The server + MUST register itself to the SILC Network by sending this payload. + The first packet after these key exchange and authentication protocols + is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID + of the server that it has created by itself. It also includes a + name of the server that is associated to the Server ID. + + The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It + MUST NOT be sent in any other packet type. The following diagram + represents the New Server Payload. + + + + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Server ID Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Server ID Data ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Server Name Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + + + +Riikonen [Page 44] + +Internet Draft 15 January 2007 + + + ~ Server Name ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 20: New Server Payload + + + o Server ID Length (2 bytes) - Length of the Server ID Data + field. + + o Server ID Data (variable length) - The encoded Server ID + data. + + o Server Name Length (2 bytes) - Length of the server name + field. + + o Server Name (variable length) - The server name string. + + +2.3.19 New Channel Payload + + Information about newly created channel is broadcasted to all routers + in the SILC network by sending this packet payload. Channels are + created by router of the cell. Server never creates channels unless + it is a standalone server and it does not have router connection, + in this case server acts as router. Normal server send JOIN command + to the router (after it has received JOIN command from client) which + then processes the command and creates the channel. Client MUST NOT + send this packet. Server MAY send this packet to a router when it is + announcing its existing channels to the router after it has connected + to the router. + + The packet use generic Channel Payload as New Channel Payload. See + section 2.3.2.3 for generic Channel Payload. The Mode Mask field in the + Channel Payload is the mode of the channel. + + +2.3.20 Key Agreement Payload + + This payload is used by clients to request key negotiation between + another client in the SILC Network. The key agreement protocol used + is the SKE protocol. The result of the protocol, the secret key + material, can be used for example as private message key between the + two clients. This significantly adds security as the clients agree + about the key without any server interaction. The protocol is executed + peer to peer. The server and router MUST NOT send this payload. + + The sender MAY tell the receiver of this payload the hostname and the + + + +Riikonen [Page 45] + +Internet Draft 15 January 2007 + + + port where the SKE protocol is running in the sender's end. The + receiver MAY then initiate the SKE negotiation with the sender. The + sender MAY also optionally not to include the hostname and the port + of its SKE protocol. In this case the receiver MAY reply to the + request by sending the same payload filled with the receiver's hostname + and the port where the SKE protocol is running. The sender MAY then + initiate the SKE negotiation with the receiver. + + This payload may be sent with SILC_PACKET_KEY_AGREEMENT and + SILC_PACKET_FTP packet types. It MUST NOT be sent in any other packet + types. The following diagram represents the Key Agreement Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Hostname Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Hostname ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Protocol | Port | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 21: Key Agreement Payload + + + o Hostname Length (2 bytes) - Indicates the length of the + Hostname field. + + o Hostname (variable length) - The hostname or IP address where + the SKE protocol is running, as UTF-8 encoded string. The sender + MAY fill this field when sending the payload. If the receiver + sends this payload as reply to the request it MUST fill this field. + + o Protocol (2 bytes) - The internet protocol used for the key + agreement connection. Possible values are 0 for TCP and 1 for + UDP. Other values are unsupported. This is a 16 bit MSB first + order value. If Hostname field is not present, the value in + this field is ignored. + + o Port (2 bytes) - The port where the SKE protocol is bound. + The sender MAY fill this field when sending the payload. If + the receiver sends this payload as reply to the request it + MUST fill this field. This is a 16 bit MSB first order value. + + + + + +Riikonen [Page 46] + +Internet Draft 15 January 2007 + + + After the key material has been received from the SKE protocol it is + processed as the [SILC3] describes. If the key material is used as + channel private key then the Sending Encryption Key, as defined in + [SILC3] is used as the channel private key. Other key material must + be discarded. The [SILC1] in section 4.6 defines the way to use the + key material if it is intended to be used as private message keys. + Any other use for the key material is undefined. + + +2.3.21 Resume Router Payload + + See the [SILC1] for Resume Router protocol where this payload is + used. The payload may only be sent with SILC_PACKET_RESUME_ROUTER + packet. It MUST NOT be sent in any other packet type. The following + diagram represents the Resume Router Payload. + + + 1 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Type | Session ID | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 22: Resume Router Payload + + + o Type (1 byte) - Indicates the type of the backup resume + protocol packet. The type values are defined in [SILC1]. + + o Session ID (1 bytes) - Indicates the session ID for the + backup resume protocol. The sender of the packet sets this + value and the receiver MUST set the same value in subsequent + reply packet. + + + + +2.3.22 File Transfer Payload + + File Transfer Payload is used to perform file transfer protocol between + two entities in the network. The actual file transfer protocol is always + encapsulated inside the SILC Packet. The actual data stream is also sent + peer to peer outside SILC network. + + When an entity, usually a client wishes to perform file transfer protocol + with another client in the network, they perform Key Agreement protocol + as described in the section 2.3.20 Key Agreement Payload and in [SILC3], + inside File Transfer Payload. After the Key Agreement protocol has been + + + +Riikonen [Page 47] + +Internet Draft 15 January 2007 + + + performed the subsequent packets in the data stream will be protected + using the new key material. The actual file transfer protocol is also + initialized in this stage. All file transfer protocol packets are always + encapsulated in the File Transfer Payload and protected with the + negotiated key material. + + The payload may only be sent with SILC_PACKET_FTP packet. It MUST NOT + be sent in any other packet type. The following diagram represents the + File Transfer Payload. + + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Type | | + +-+-+-+-+-+-+-+-+ + + | | + ~ Data ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 23: File Transfer Payload + + + o Type (1 byte) - Indicates the type of the file transfer + protocol. The following file transfer protocols has been + defined: + + 1 Secure File Transfer Protocol (SFTP) (mandatory) + + If zero (0) value or any unsupported file transfer protocol + type is found in this field the packet MUST be discarded. + The currently mandatory file transfer protocol is SFTP. + The SFTP protocol is defined in [SFTP]. + + o Data (variable length) - Arbitrary file transfer data. The + contents and encoding of this field is dependent of the usage + of this payload and the type of the file transfer protocol. + When this payload is used to perform the Key Agreement + protocol, this field include the Key Agreement Payload, + as defined in the section 2.3.20 Key Agreement Payload. + When this payload is used to send the actual file transfer + protocol data, the encoding is defined in the corresponding + file transfer protocol. + + +2.3.23 Resume Client Payload + + + + +Riikonen [Page 48] + +Internet Draft 15 January 2007 + + + This payload is used by client to resume its detached session in the + SILC Network. A client is able to detach itself from the network by + sending SILC_COMMAND_DETACH command to its server. The network + connection to the client is lost but the client remains as valid + client in the network. The client is able to resume the session back + by sending this packet and including the old Client ID, and an + Authentication Payload [SILC1] which the server use to verify with + the detached client's public key. This also implies that the + mandatory authentication method is public key authentication. + + Server or router that receives this from the client also sends this, + without the Authentication Payload, to routers in the network so that + they know the detached client has resumed. Refer to the [SILC1] for + detailed description how the detaching and resuming procedure is + performed. + + The payload may only be sent with SILC_PACKET_RESUME_CLIENT packet. It + MUST NOT be sent in any other packet type. The following diagram + represents the Resume Client Payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Client ID Length | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + ~ Client ID ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + ~ Authentication Payload ~ + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 24: Resume Client Payload + + + o Client ID Length (1 byte) - The length of the Client ID + field not including any other field. + + o Client ID (variable length) - The detached client's Client + ID. The client that sends this payload must know the Client + ID. + + o Authentication Payload (variable length) - The authentication + payload that the server will verify with the detached client's + public key. If the server doesn't know the public key, it must + retrieve it for example with SILC_COMMAND_GETKEY command. + + + +Riikonen [Page 49] + +Internet Draft 15 January 2007 + + +2.3.24 Acknowledgement Payload + + This payload is used to acknowledge a packet that had the Acknowledgement + packet flag set. The payload includes the sequence number of the packet + that had the flag set, which the recipient can use to identify that the + packet was acknowledged. + + The payload may only be sent with SILC_PACKET_ACK packet. It + MUST NOT be sent in any other packet type. The following diagram + represents the Acknowledgement Payload. + + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Packet Sequence Number | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 24: Resume Client Payload + + + o Packet Sequence Number (4 bytes) - The packet sequence number + of the packet that had the Acknowledgement flag set. + + +2.4 SILC ID Types + + ID's are used in the SILC network to associate different entities. + The following ID's has been defined to be used in the SILC network. + + 0 No ID + + This is used when other ID type is available at the time. + + 1 Server ID + + Server ID to associate servers. See the format of + this ID in [SILC1]. + + 2 Client ID + + Client ID to associate clients. See the format of + this ID in [SILC1]. + + 3 Channel ID + + Channel ID to associate channels. See the format of + this ID in [SILC1]. + + + + +Riikonen [Page 50] + +Internet Draft 15 January 2007 + + + When encoding different IDs into the ID Payload, all fields are always + in MSB first order. The IP address, port, and/or the random number + are encoded in the MSB first order. + + +2.5 Packet Encryption And Decryption + + SILC packets are encrypted almost entirely. Only the MAC at the end + of the packet is never encrypted. The SILC Packet header is the first + part of a packet to be encrypted and it is always encrypted with the + key of the next receiver of the packet. The data payload area of the + packet is always entirely encrypted and it is usually encrypted with + the next receiver's key. However, there are some special packet types + and packet payloads that require special encryption process. These + special cases are described in the next sections. First is described + the normal packet encryption process. + + + +2.5.1 Normal Packet Encryption And Decryption + + Normal SILC packets are encrypted with the session key of the next + receiver of the packet. The entire SILC Packet header and the packet + data payload is is encrypted with the same key. Padding of the packet + is also encrypted always with the session key, also in special cases. + Computed MAC of the packet MUST NOT be encrypted. + + Decryption process in these cases are straightforward. The receiver + of the packet MUST first decrypt the SILC Packet header, or some parts + of it, usually first 16 bytes of it. Then the receiver checks the + packet type from the decrypted part of the header and can determine + how the rest of the packet must be decrypted. If the packet type is + any of the special cases described in the following sections the packet + decryption is special. If the packet type is not among those special + packet types rest of the packet can be decrypted with the same key. + At this point the receiver is also able to determine the length of the + packet. + + With out a doubt, this sort of decryption processing causes some + overhead to packet decryption, but never the less, is required. + + The MAC of the packet is also verified at this point. The MAC is + computed from the ciphertext of the packet so it can be verified + at this stage. The length of the packet need to be known to be able + to verify the MAC from the ciphertext so the first 16 bytes need to + be decrypted to determine the packet length. However, the MAC MUST + be verified from the entire ciphertext. + + + + +Riikonen [Page 51] + +Internet Draft 15 January 2007 + + +2.5.2 Channel Message Encryption And Decryption + + Channel Messages (Channel Message Payload) are always encrypted with + the channel specific key. However, the SILC Packet header is not + encrypted with that key. As in normal case, the header is encrypted + with the key of the next receiver of the packet. Note that, in this + case the encrypted data area is not touched at all; it MUST NOT be + re-encrypted with the session key. + + Receiver of a channel message, who ever that is, is REQUIRED to decrypt + the SILC Packet header to be able to recognize the packet to be as + channel message. This is same procedure as for normal SILC packets. + As the receiver founds the packet to be channel message, rest of the + packet processing is special. Rest of the SILC Packet header is + decrypted with the same session key along with the padding of the + packet. After that the packet is protected with the channel specific + key and thus can be decrypted only if the receiver is the client on + the channel. See section 2.7 Packet Padding Generation for more + information about padding on special packets. + + If the receiver of the channel message is router which is routing the + message to another router then it MUST decrypt the Channel Message + payload too. Between routers (that is, between cells) channel messages + are protected with session keys shared between the routers. This + causes another special packet processing for channel messages. If + the channel message is received from another router then the entire + packet, including Channel Message payload, MUST be encrypted with the + session key shared between the routers. In this case the packet + decryption process is as with normal SILC packets. Hence, if the + router is sending channel message to another router the Channel + Message payload MUST have been decrypted and MUST be re-encrypted + with the session key shared between the another router. In this + case the packet encryption is as with any normal SILC packet. + + It must be noted that this is only when the channel messages are sent + from router to another router. In all other cases the channel + message encryption and decryption is as described before. This + different processing of channel messages with router to router + connection is because channel keys are cell specific. All cells have + their own channel keys thus the channel message traveling from one + cell to another MUST be protected as it would be any normal SILC + packet. + + If the SILC_CMODE_PRIVKEY channel mode has been set for the channel + then the router cannot decrypt the packet as it does not know the + private key. In this case the entire packet MUST be encrypted with + the session key and sent to the router. The router receiving the + packet MUST check the channel mode and decrypt the packet accordingly. + + + +Riikonen [Page 52] + +Internet Draft 15 January 2007 + + +2.5.3 Private Message Encryption And Decryption + + By default, private message in SILC are protected by session keys. + In this case the private message encryption and decryption process is + equivalent to normal packet encryption and decryption. + + However, private messages MAY be protected with private message key + which causes the packet to be special packet. The procedure in this + case is very much alike to channel packets. The actual private message + is encrypted with the private message key and other parts of the + packet is encrypted with the session key. See 2.7 Packet Padding + Generation for more information about padding on special packets. + + The difference from channel message processing is that server or router + en route never decrypts the actual private message, as it does not + have the key to do that. Thus, when sending packets between router + the processing is same as in any other case as well; the packet's header + and padding is protected by the session key and the data area is not + touched and is not re-encrypted. + + The true receiver of the private message is able to decrypt the private + message as it shares the key with the sender of the message. + + +2.6 Packet MAC Generation + + Data integrity of a packet is protected by including a message + authentication code (MAC) at the end of the packet. The MAC is computed + from shared secret MAC key, that is established by the SILC Key Exchange + protocol, from packet sequence number, and from the encrypted packet + data. The MAC is always computed after packet is encrypted. This is + so called Encrypt-Then-MAC order; packet is first encrypted, then MAC + is computed from the encrypted data. + + The MAC is computed from entire packet. Every bit of data in the packet, + including SILC Packet Header is used in the MAC computing. This way + the entire packet becomes authenticated. + + Hence, packet's MAC generation is as follows: + + mac = MAC(key, sequence number | Encrypted SILC packet) + + The MAC key is negotiated during the SKE protocol. The sequence number + is a 32 bit MSB first value starting from zero for first packet and + increasing for subsequent packets, finally wrapping after 2^32 packets. + The value is never reset, not even after rekey has been performed. + However, rekey MUST be performed before the sequence number wraps + and repeats from zero. Note that the sequence number is incremented only + + + +Riikonen [Page 53] + +Internet Draft 15 January 2007 + + + when MAC is computed for a packet. If packet is not encrypted and MAC is + not computed then the sequence number is not incremented. Hence, the + sequence number is zero for the very first encrypted packet. + + See [SILC1] for defined and allowed MAC algorithms. + + +2.7 Packet Padding Generation + + Padding is needed in the packet because the packet is encrypted. It + always MUST be multiple by eight (8) or multiple by the block size + of the cipher, which ever is larger. The padding is always encrypted. + + For normal packets the padding is added after the SILC Packet Header + and between the Data Payload area. The padding for normal packets + may be calculated as follows: + + padding_length = 16 - (packet_length mod block_size) + if (padding_length < 8) + padding_length += block_size + + The `block_size' is the block size of the cipher. The maximum padding + length is 128 bytes, and minimum is 8 bytes. For example, packets that + include a passphrase or a password for authentication purposes SHOULD + pad the packet up to the maximum padding length. The maximum padding + is calculated as follows: + + padding_length = 128 - (packet_length mod block_size) + + For special packets the padding calculation is different as special + packets may be encrypted differently. In these cases the encrypted + data area MUST already be multiple by the block size thus in this case + the padding is calculated only for SILC Packet Header, not for any + other area of the packet. The same algorithm works in this case as + well, except that the `packet length' is now the SILC Packet Header + length. + + The padding MUST be random data, preferably, generated by + cryptographically strong random number generator for each packet + separately. + + +2.8 Packet Compression + + SILC Packets MAY be compressed. In this case the data payload area + is compressed and all other areas of the packet MUST remain as they + are. After compression is performed for the data area, the length + field of Packet Header MUST be set to the compressed length of the + + + +Riikonen [Page 54] + +Internet Draft 15 January 2007 + + + data. + + The compression MUST always be applied before encryption. When + the packet is received and decrypted the data area MUST be decompressed. + Note that the true sender of the packet MUST apply the compression and + the true receiver of the packet MUST apply the decompression. Any + server or router en route SHOULD NOT decompress the packet. + + +2.9 Packet Sending + + The sender of the packet MUST assemble the SILC Packet Header with + correct values. It MUST set the Source ID of the header as its own + ID, unless it is forwarding the packet. It MUST also set the Destination + ID of the header to the true destination. If the destination is client + it will be Client ID, if it is server it will be Server ID and if it is + channel it will be Channel ID. + + If the sender wants to compress the packet it MUST apply the + compression now. Sender MUST also compute the padding as described + in above sections. Then sender MUST encrypt the packet as has been + described in above sections according whether the packet is normal + packet or special packet. Then sender MUST compute the MAC of the + packet. The computed MAC MUST NOT be encrypted. + + +2.10 Packet Reception + + On packet reception the receiver MUST check that all fields in the + SILC Packet Header are valid. It MUST check the flags of the + header and act accordingly. It MUST also check the MAC of the packet + and if it is to be failed the packet MUST be discarded. Also if the + header of the packet includes any bad fields the packet MUST be + discarded. + + See above sections on the decryption process of the received packet. + + The receiver MUST also check that the ID's in the header are valid + ID's. Unsupported ID types or malformed ID's MUST cause packet + rejection. The padding on the reception is always ignored. + + The receiver MUST also check the packet type and start parsing the + packet according to the type. However, note the above sections on + special packet types and their parsing. + + +2.11 Packet Routing + + + + +Riikonen [Page 55] + +Internet Draft 15 January 2007 + + + Routers are the primary entities in the SILC network that takes care + of packet routing. Normal servers performs packet forwarding, for + example, when they are forwarding channel message to the local clients. + Routing is quite simple as every packet tells the true origin and the + true destination of the packet. + + It is still RECOMMENDED for routers that has several routing connections + to create route cache for those destinations that has faster route than + the router's primary route. This information is available for the router + when other router connects to the router. The connecting party then + sends all of its locally connected clients, servers and channels. These + informations helps to create the route cache. Also, when new channels + are created to a cell its information is broadcasted to all routers + in the network. Channel ID's are based on router's ID thus it is easy + to create route cache based on these informations. If faster route for + destination does not exist in router's route cache the packet MUST be + routed to the primary route (default route). + + However, there are some issues when routing channel messages to group + of users. Routers are responsible of routing the channel message to + other routers, local servers and local clients as well. Routers MUST + send the channel message to only one router in the network, preferably + to the shortest route to reach the channel users. The message can be + routed into either upstream or downstream. After the message is sent + to a router in the network it MUST NOT be sent to any other router in + either same route or other route. The message MUST NOT be routed to + the router it came from. + + When routing for example private messages they should be routed to the + shortest route always to reach the destination client as fast as possible. + + For server which receives a packet to be forwarded to an entity that is + indirectly connected to the sender, the server MUST check whether that + particular packet type is allowed to be sent to that destination. Not + all packets may be sent by some odd entity to for example a local client, + or to some remote server or router, that is indirectly connected to the + sender. See section 2.3 SILC Packet Types and paragraph about indirectly + connected entities and sending packets to them. That section defines the + packets that may be sent to indirectly connected entities. When a server + or a router receives a packet that may be sent to indirectly connected + entity and it is destined to other entity except that server, it MUST + route it further either to shortest route or to the primary route to reach + that destination. + + Routers form a ring in the SILC network. However, routers may have other + direct connections to other routers in the network too. This can cause + interesting routing problems in the network. Since the network is a ring, + the packets usually should be routed into clock-wise direction, or if it + + + +Riikonen [Page 56] + +Internet Draft 15 January 2007 + + + cannot be used then always counter clock-wise (primary route) direction. + Problems may arise when a faster direct route exists and router is routing + a channel message. Currently channel messages must be routed either + in upstream or downstream, they cannot be routed to other direct routes. + The SILC protocol should have a shortest path discovery protocol, and some + existing routing protocol, that can handle a ring network with other + direct routes inside the ring (so called hybrid ring-mesh topology), + MAY be defined to be used with the SILC protocol. Additional + specifications MAY be written on the subject to permeate this + specification. + + +2.12 Packet Broadcasting + + SILC packets MAY be broadcasted in SILC network. However, only router + server may send or receive broadcast packets. Client and normal server + MUST NOT send broadcast packets and they MUST ignore broadcast packets + if they receive them. Broadcast packets are sent by setting Broadcast + flag to the SILC packet header. + + Broadcasting packets means that the packet is sent to all routers in + the SILC network, except to the router that sent the packet. The router + receiving broadcast packet MUST send the packet to its primary route. + The fact that SILC routers may have several router connections can + cause problems, such as race conditions inside the SILC network, if + care is not taken when broadcasting packets. Router MUST NOT send + the broadcast packet to any other route except to its primary route. + + If the primary route of the router is the original sender of the packet + the packet MUST NOT be sent to the primary route. This may happen + if router has several router connections and some other router uses + the router as its primary route. + + Routers use broadcast packets to broadcast for example information + about newly registered clients, servers, channels etc. so that all the + routers may keep these informations up to date. + + +3 Security Considerations + + Security is central to the design of this protocol, and these security + considerations permeate the specification. Common security considerations + such as keeping private keys truly private and using adequate lengths for + symmetric and asymmetric keys must be followed in order to maintain the + security of this protocol. + + +4 References + + + +Riikonen [Page 57] + +Internet Draft 15 January 2007 + + + [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC), + Protocol Specification", Internet Draft, January 2007. + + [SILC3] Riikonen, P., "SILC Key Exchange and Authentication + Protocols", Internet Draft, January 2007. + + [SILC4] Riikonen, P., "SILC Commands", Internet Draft, January 2007. + + [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol", + RFC 1459, May 1993. + + [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810, + April 2000. + + [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC + 2811, April 2000. + + [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC + 2812, April 2000. + + [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC + 2813, April 2000. + + [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol", + Internet Draft. + + [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440, + November 1998. + + [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693, + September 1999. + + [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key + Infrastructure, Certificate and CRL Profile", RFC 2459, + January 1999. + + [Schneier] Schneier, B., "Applied Cryptography Second Edition", + John Wiley & Sons, New York, NY, 1996. + + [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography", + CRC Press 1997. + + [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol", + RFC 2412, November 1998. + + [ISAKMP] Maughan D., et al, "Internet Security Association and + Key Management Protocol (ISAKMP)", RFC 2408, November + 1998. + + + +Riikonen [Page 58] + +Internet Draft 15 January 2007 + + + [IKE] Harkins D., and Carrel D., "The Internet Key Exchange + (IKE)", RFC 2409, November 1998. + + [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message + Authentication", RFC 2104, February 1997. + + [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography + Specifications, Version 2.0", RFC 2437, October 1998. + + [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [SFTP] Ylonen T., and Lehtinen S., "Secure Shell File Transfer + Protocol", Internet Draft, March 2001. + + [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO + 10646", RFC 3629, November 2003. + + +5 Author's Address + + Pekka Riikonen + Helsinki + Finland + + EMail: priikone@iki.fi + + +6 Full Copyright Statement + + Copyright (C) The Internet Society (2007). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + + + + + + + + +Riikonen [Page 59] +