+++ /dev/null
-.pl 10.0i
-.po 0
-.ll 7.2i
-.lt 7.2i
-.nr LL 7.2i
-.nr LT 7.2i
-.ds LF Riikonen
-.ds RF FORMFEED[Page %]
-.ds CF
-.ds LH Internet Draft
-.ds RH 13 September 2000
-.ds CH
-.na
-.hy 0
-.in 0
-.nf
-Network Working Group P. Riikonen
-Internet-Draft
-draft-riikonen-silc-pp-00.txt 13 September 2000
-Expires: 13 May 2001
-
-.in 3
-
-.ce 2
-SILC Packet Protocol
-<draft-riikonen-silc-pp-00.txt>
-
-.ti 0
-Status of this Memo
-
-This document is an Internet-Draft and is in full conformance with
-all provisions of Section 10 of RFC 2026. Internet-Drafts are
-working documents of the Internet Engineering Task Force (IETF), its
-areas, and its working groups. Note that other groups may also
-distribute working documents as Internet-Drafts.
-
-Internet-Drafts are draft documents valid for a maximum of six months
-and may be updated, replaced, or obsoleted by other documents at any
-time. It is inappropriate to use Internet-Drafts as reference
-material or to cite them other than as "work in progress."
-
-The list of current Internet-Drafts can be accessed at
-http://www.ietf.org/ietf/1id-abstracts.txt
-
-The list of Internet-Draft Shadow Directories can be accessed at
-http://www.ietf.org/shadow.html
-
-The distribution of this memo is unlimited.
-
-
-.ti 0
-Abstract
-
-This memo describes a Packet Protocol used in the Secure Internet Live
-Conferencing (SILC) protocol specified in the Secure Internet Live
-Conferencing, Protocol Specification Internet Draft [SILC1]. This
-protocol describes the packet types and packet payloads which defines
-the contents of the packets. The protocol provides secure binary packet
-protocol that assures that the contents of the packets are secured and
-authenticated.
-
-
-
-
-
-
-
-
-
-.ti 0
-Table of Contents
-
-.nf
-1 Introduction .................................................. 3
-2 SILC Packet Protocol .......................................... 4
- 2.1 SILC Packet ............................................... 4
- 2.2 SILC Packet Header ........................................ 5
- 2.3 SILC Packet Types ......................................... 7
- 2.3.1 SILC Packet Payloads ................................ 15
- 2.3.2 Disconnect Payload .................................. 15
- 2.3.3 Success Payload ..................................... 16
- 2.3.4 Failure Payload ..................................... 16
- 2.3.5 Reject Payload ...................................... 17
- 2.3.6 Notify Payload ...................................... 17
- 2.3.7 Error Payload ....................................... 18
- 2.3.8 Channel Message Payload ............................. 19
- 2.3.9 Channel Key Payload ................................. 20
- 2.3.10 Private Message Payload ............................ 23
- 2.3.11 Private Message Key Payload ........................ 24
- 2.3.12 Command Payload .................................... 25
- 2.3.12.1 Command Argument Payload .................. 25
- 2.3.13 Command Reply Payload .............................. 26
- 2.3.14 Connection Auth Request Payload .................... 27
- 2.3.15 New ID Payload ..................................... 28
- 2.3.16 New ID List Payload ................................ 29
- 2.3.17 New Client Payload ................................. 29
- 2.3.18 New Server Payload ................................. 31
- 2.3.19 New Channel Payload ................................ 31
- 2.3.20 New Channel User Payload ........................... 32
- 2.3.21 New Channel List Payload ........................... 33
- 2.3.22 New Channel User List Payload ...................... 34
- 2.3.23 Replace ID Payload ................................. 34
- 2.3.24 Remove ID Payload .................................. 35
- 2.4 SILC ID Types ............................................. 36
- 2.5 Packet Encryption And Decryption .......................... 37
- 2.5.1 Normal Packet Encryption And Decryption ............. 37
- 2.5.2 Channel Message Encryption And Decryption ........... 37
- 2.5.3 Private Message Encryption And Decryption ........... 38
- 2.6 Packet MAC Generation ..................................... 39
- 2.7 Packet Padding Generation ................................. 39
- 2.8 Packet Compression ........................................ 40
- 2.9 Packet Sending ............................................ 40
- 2.10 Packet Reception ......................................... 41
- 2.11 Packet Routing ........................................... 42
- 2.12 Packet Forwarding ........................................
- 2.13 Packet Broadcasting ...................................... 41
- 2.14 Packet Tunneling ......................................... 42
-3 Security Considerations ....................................... 43
-4 References .................................................... 43
-5 Author's Address .............................................. 44
-
-.ti 0
-List of Figures
-
-.nf
-Figure 1: Typical SILC Packet
-Figure 2: SILC Packet Header
-Figure 3: Disconnect Payload
-Figure 4: Success Payload
-Figure 5: Failure Payload
-Figure 6: Reject Payload
-Figure 7: Notify Payload
-Figure 8: Error Payload
-Figure 9: Channel Message Payload
-Figure 10: Channel Key Payload
-Figure 11: Private Message Payload
-Figure 12: Private Message Key Payload
-Figure 13: Command Payload
-Figure 14: Command Argument Payload
-Figure 15: Connection Auth Request Payload
-Figure 16: New ID Payload
-Figure 17: New Client Payload
-Figure 18: New Server Payload
-Figure 19: New Channel Payload
-Figure 20: New Channel User Payload
-Figure 21: Replace ID Payload
-Figure 22: Remove ID Payload
-Figure 23: Remove Channel User Payload
-
-
-.ti 0
-1. Introduction
-
-This document describes a Packet Protocol used in the Secure Internet
-Live Conferencing (SILC) protocol specified in the Secure Internet Live
-Conferencing, Protocol Specification Internet Draft [SILC1]. This
-protocol describes the packet types and packet payloads which defines
-the contents of the packets. The protocol provides secure binary packet
-protocol that assures that the contents of the packets are secured and
-authenticated.
-
-The basis of SILC protocol relies in the SILC packets and it is with
-out a doubt the most important part of the protocol. It is also probably
-the most complicated part of the protocol. Packets are used all the
-time in the SILC network to send messages, commands and other information.
-All packets in SILC network are always encrypted and their integrity
-is assured by computed MACs. The protocol defines several packet types
-and packet payloads. Each packet type usually has a specific packet
-payload that actually defines the contents of the packet. Each packet
-also includes a default SILC Packet Header that provides sufficient
-information about the origin of the packet and destination of the
-packet.
-
-
-.ti 0
-2 SILC Packet Protocol
-
-.ti 0
-2.1 SILC Packet
-
-SILC packets deliver messages from sender to receiver securely by
-encrypting important fields of the packet. The packet consists of
-default SILC Packet Header, Padding, Packet Payload data, and, packet
-MAC.
-
-The following diagram illustrates typical SILC packet.
-
-
-.in 5
-.nf
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-| n bytes | 1 - n bytes | n bytes | n bytes
-| SILC Header | Padding | Data Payload | MAC
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-.in 3
-
-.ce
-Figure 1: Typical SILC Packet
-
-
-SILC Header is always the first part of the packet and its purpose
-is to provide information about the packet. It provides for example
-the packet type, origin of the packet and the destination of the packet.
-The header is variable in length and first two (2) bytes of the
-header (thus first two bytes of the packet) are not encrypted. The
-first two (2) bytes are the length of the packet which is not encrypted.
-See following section for description of SILC Packet header. Packets
-without SILC header or with malformed SILC header must be dropped.
-
-Padding follows the packet header. The purpose of the padding is to
-make the packet multiple by eight (8) or by the block size of the
-cipher used in the encryption, which ever is larger. The maximum
-length of padding is currently 16 bytes. The padding is always
-encrypted.
-
-Data payload area follows padding and it is the actual data of the
-packet. The packet data is the packet payloads defined in this
-protocol. The data payload area is always encrypted.
-
-The last part of SILC packet is the packet MAC that assures the
-integrity of the packet. The MAC is always computed from the packet
-before the encryption is applied to the packet. If compression is used
-in the packet the MAC is computed after the compression has been
-applied. The compression, on the other hand, is always applied before
-encryption.
-
-All fields in all packet payloads are always in MSB (most significant
-byte first) order.
-
-
-.ti 0
-2.2 SILC Packet Header
-
-The default 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.
-
-Following diagram represents the default SILC header format.
-(*) indicates that this field is never encrypted. Other fields are
-always encrypted.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Payload Length * | Flags | Packet Type |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Source ID Length | Destination ID Length |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Src ID Type | |
-+-+-+-+-+-+-+-+-+ +
-| |
-~ Source ID ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Dst ID Type | |
-+-+-+-+-+-+-+-+-+ +
-| |
-~ Destination ID ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 2: SILC Packet Header
-
-
-.in 6
-o Payload Length (2 bytes) - Is the length of the packet
- not including the padding of the packet. This field must
- not be encrypted but must always be authenticated.
-
-o Flags (1 byte) - Indicates flags to be used in packet
- processing. Several flags may be set by ORing the flags
- together.
-
- Following flags are reserved for this field:
-
-
-
-
- No flags 0x00
-
- In this case the field is ignored.
-
-
- Private Message Key 0x01
-
- Indicates that the packet must include private
- message that is encrypted using private key set by
- client. Servers does not know anything about this
- key and this causes that the private message is
- not handled by the server at all, it is just
- passed along. See section 2.5.3 Private Message
- Encryption And Decryption for more information.
-
-
- Forwarded 0x02
-
- Marks the packet to be forwarded. Some specific
- packet types may be forwarded. Receiver of packet
- with this flag set must not forward the packet any
- further. See section 2.12 Packet Forwarding for
- desribtion of packet forwarding.
-
-
- Broadcast 0x04
-
- Marks the packet to be broadcasted. Client cannot
- send broadcast packet and normal server cannot send
- broadcast packet. Only router server may send broadcast
- packet. The router receiving of packet with this flag
- set must send (broadcast) the packet to its primary
- route. If router has several router connections the
- packet may be sent only to the primary route. See
- section 2.13 Packet Broadcasting for description of
- packet broadcasting.
-
-
- Tunneled 0x08
-
- Marks that the packet is tunneled. Tunneling means
- that extra SILC Packet Header has been applied to the
- original packet. The outer header has this flag
- set. See section 2.14 Packet Tunneling for more
- information.
-.in 3
-
-
-
-o Packet Type (1 byte) - Is the type of the packet. Receiver
- uses this field to parse the packet. See section 2.3
- SILC Packets for list of defined packet types.
-
-o Source ID Length (2 bytes) - Indicates the length of the
- Source ID field in the header, not including this or any
- other fields.
-
-
-
-o Destination ID Length (2 bytes) - Indicates the length of the
- Destination ID field in the header, not including this or
- any other fields.
-
-o Src ID Type (1 byte) - Indicates the type of ID in the
- Source ID field. See section 2.4 SILC ID Types for
- defined ID types.
-
-o Source ID (variable length) - The actual source ID that
- indicates who is the original sender of the packet.
-
-o Dst ID Type (1 byte) - Indicates the type of ID in the
- Destination ID field. See section 2.4 SILC ID Types for
- defined ID types.
-
-o Destination ID (variable length) - The actual source ID that
- indicates who is the end receiver of the packet.
-
-
-.ti 0
-2.3 SILC Packet Types
-
-SILC packet types defines the contents of the packet and it is used by
-the receiver to parse the packet. The packet type is 8 bits, as a one
-byte, in length. The range for the packet types are from 0 - 255,
-where 0 is never sent and 255 is currently reserved for future
-extensions and must not be defined to any other purpose. Every SILC
-specification compliant implementation should support all of these packet
-types.
-
-The below list of the SILC Packet types includes reference to the packet
-payload as well. Packet payloads are the actual packet, that is, the data
-that the packet consists of. Each packet type defines packet payload
-which usually may only be sent with the specific packet type.
-
-Most of the packets are packets that must be destined directly to entity
-that is connected to the sender. It is not allowed, for example, for
-router to send disconnect packet to client that is not directly connected
-to the router. However, there are some special packet types that may
-be destined to some entity that the sender has not direct connection
-with. These packets are for example private message packets, channel
-message packets, command packets and some other packets that may be
-broadcasted in the SILC network. If the packet is allowed to be sent to
-indirectly connected entity it is mentioned separately in the packet
-description (unless it is obvious as in private and channel message
-packets). Other packets must not be sent or accepted, if sent, to
-indirectly connected entities.
-
-List of SILC Packet types are defined as follows.
-
-.in 1
- 0 SILC_PACKET_NONE
-
- This type is reserved and it is never sent.
-
-
- 1 SILC_PACKET_DISCONNECT
-
- This packet is sent to disconnect the remote end. Reason of
- the disconnection is sent inside the packet payload. Client
- usually does not send this packet.
-
- Payload of the packet: See section 2.3.2 Disconnect Payload
-
-
- 2 SILC_PACKET_SUCCESS
-
- This packet is sent upon successful execution of some protocol.
- The status of the success is sent in the packet.
-
- Payload of the packet: See section 2.3.3 Success Payload
-
-
- 3 SILC_PACKET_FAILURE
-
- This packet is sent upon failure of some protocol. The status
- of the failure is sent in the packet.
-
- Payload of the packet: See section 2.3.4 Failure Payload
-
-
- 4 SILC_PACKET_REJECT
-
- This packet may be sent upon rejection of some protocol.
- The status of the rejection is sent in the packet.
-
- Payload of the packet: See section 2.3.5 Reject Payload
-
-
- 5 SILC_PACKET_NOTIFY
-
- This packet is used to send notify message, usually from
- server to client, although it may be sent from server to another
- server as well. Client never sends this packet. Server may
- send this packet to channel as well when the packet is
- distributed to all clients on the channel. Receiver of this
- packet may ignore the packet if it chooses so. However, it
- should not be ignored.
-
- Payload of the packet: See section 2.3.6 Notify Payload.
-
-
- 6 SILC_PACKET_ERROR
-
- This packet is sent when an error occurs. Server may
- send this packet. Client never sends this packet. The
- client may entirely ignore the packet, however, server is
- most likely to take action anyway. This packet may be sent
- to entity that is indirectly connected to the sender.
-
- Payload of the packet: See section 2.3.7 Error Payload.
-
-
- 7 SILC_PACKET_CHANNEL_MESSAGE
-
- This packet is used to send messages to channels. The packet
- includes Channel ID of the channel and the actual message to
- the channel. Messages sent to the channel are always protected
- by channel specific keys. Channel Keys are distributed by
- SILC_PACKET_CHANNEL_KEY packet.
-
- When client sends this packet the destination ID in the SILC
- header must be the Channel ID of the channel the message is
- destined to. If server sends this packet to a client the
- destination ID in the SILC header must be the Client ID of
- the client receiving the packet.
-
- If server sends this packet to router or if router sends this
- packet to server or another router the destination ID in the
- SILC header must be the Channel ID of the channel. Server
- (including router) distributes this packet only to its local
- clients who are joined to the channel. Servers and routers
- also determines who are on the channel and when this packet
- needs to be sent, as described in section Client To Client
- in [SILC1].
-
- Payload of the packet: See section 2.3.8 Channel Message
- Payload
-
-
- 8 SILC_PACKET_CHANNEL_KEY
-
- This packet is used to distribute new key for particular
- channel. Each channel has their own independent keys that
- is used to protect the traffic on the channel. Only server
- may send this packet. This packet may be sent to entity
- that is indirectly connected to the sender.
-
- Payload of the packet: See section 2.3.9 Channel Key Payload
-
-
- 9 SILC_PACKET_PRIVATE_MESSAGE
-
- This packet is used to send private messages from client
- to another client. By default, private messages are protected
- by session keys established by normal key exchange protocol.
- However, it is possible to use specific key to protect private
- messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
- agree the key with the remote client. Pre-shared key may be
- used as well if both of the client knows it, however, it needs
- to be agreed outside SILC. See more of this in [SILC1].
-
- Payload of the packet: See section 2.3.10 Private Message
- Payload
-
-
- 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
-
- This packet is used to agree about a key to be used to protect
- the private messages between two clients. If this is not sent
- the normal session key is used to protect the private messages
- inside SILC network. Agreeing to use specific key to protect
- private messages adds security, as no server between the two
- clients will be able to decrypt the private message. However,
- servers inside SILC network are considered to be trusted, thus
- using normal session key to protect private messages does not
- degree security. Whether to agree to use specific keys by
- default or to use normal session keys by default, is
- implementation specific issue. See more of this in [SILC1].
-
- Payload of the packet: See section 2.3.11 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 [SILC1]. 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 2.3.12 Command Payload
-
-
- 12 SILC_PACKET_COMMAND_REPLY
-
- This packet is send as reply to the SILC_PACKET_COMMAND packet.
- The contents of this packet is command specific. This packet
- maybe sent to entity that is indirectly connected to the sender.
-
- Payload of the packet: See section 2.3.13 Command Reply
- Payload and section 2.3.12 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
-
- 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 the authentication method to
- be used in the SILC Connection Authentication Protocol. If
- initiator of the protocol does not know the mandatory
- authentication method this packet is used to determine it.
-
- The party receiving this payload must respond with the same
- packet including the mandatory authentication method.
-
- Payload of the packet: See section 2.3.14 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 ID's from server to
- router and from router to all routers in the SILC network.
- This is used when for example new client is registered to
- SILC network. The newly created ID's of these operations are
- distributed by this packet. Only server may send this packet,
- however, client must be able to receive this packet.
-
- Payload of the packet: See section 2.3.15 New ID Payload
-
-
- 19 SILC_PACKET_NEW_ID_LIST
-
- This packet is used to distribute list of new ID's from
- server to routers. This is equivalent to previous packet
- type except that it may include several ID's. Client must
- not send this packet.
-
- Payload of the packet: See section 2.3.16 New ID List
- Payload
-
-
- 20 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.
-
- Payload of the packet: See section 2.3.17 New Client Payload
-
-
- 21 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.
- Client must not send or receive this packet.
-
- Payload of the packet: See section 2.3.18 New Server Payload
-
-
- 22 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 maybe sent to entity that is indirectly
- connected to the sender.
-
- Payload of the packet: See section 2.3.19 New Channel Payload
-
-
- 23 SILC_PACKET_NEW_CHANNEL_USER
-
- This packet is used to notify routers about new user on channel.
- The packet is sent after user has joined to the channel. Server
- may send this packet to its router and router may send this to
- its primary router. Client must not send this packet. This
- packet maybe sent to entity that is indirectly connected to the
- sender.
-
- Payload of the packet: See section 2.3.20 New Channel User
- Payload
-
-
- 24 SILC_PACKET_NEW_CHANNEL_LIST
-
- This packet is used to distribute list of created channels
- from server to routers. This is equivalent to the packet
- SILC_PACKET_NEW_CHANNEL except that it may include several
- payloads. Client must not send this packet.
-
- Payload of the packet: See section 2.3.21 New Channel List
- Payload
-
-
- 25 SILC_PACKET_NEW_CHANNEL_USER_LIST
-
- This packet is used to distribute list of users on specific
- channel from server to routers. This is equivalent to the
- packet SILC_PACKET_NEW_CHANNEL_USER except that it may
- include several payloads. Client must not send this packet.
-
- Payload of the packet: See section 2.3.22 New Channel User
- List Payload
-
-
- 26 SILC_PACKET_REPLACE_ID
-
- This packet is used to replace old ID with new ID sent in
- the packet payload. For example, when client changes its
- nickname new ID is created and this packet can be used to
- distribute the new ID and the old ID is removed when it is
- send in the packet. Client cannot send or receive this
- packet. This packet maybe sent to entity that is indirectly
- connected to the sender.
-
- Payload of the packet: See section 2.3.23 Replace ID Payload
-
-
- 27 SILC_PACKET_REMOVE_ID
-
- This packet is used to removed ID. For example, when client
- exits SILC network its ID is removed. Client must not send
- this packet. This packet maybe sent to entity that is
- indirectly connected to the sender.
-
- Payload of the packet: See section 2.3.24 Remove ID Payload
-
-
- 28 SILC_PACKET_REMOVE_CHANNEL_USER
-
- This packet is used to remove user from a channel. This is
- used by router to notify other routers in the network that a
- client has leaved a channel. This packet maybe sent to entity
- that is indirectly connected to the sender.
-
- Payload of the packet: See section 2.3.25 Remove Channel User
- Payload
-
-
- 29 SILC_PACKET_REKEY
-
- This packet is used to indicate that re-key must be performed
- for session keys. See section Session Key Regeneration in
- [SILC1] for more information. This packet does not have
- a payload.
-
-
- 30 SILC_PACKET_REKEY_DONE
-
- This packet is used to indicate that re-key is performed and
- new keys must be used hereafter. This is sent only if re-key
- was done without PFS option. If PFS is set, this is not sent
- as SILC Key Exchange protocol is executed. This packet does
- not have a payload.
-
-
- 31 - 254
-
- Currently undefined commands.
-
-
- 255 SILC_PACKET_MAX
-
- This type is reserved for future extensions and currently it
- is not sent.
-.in 3
-
-
-.ti 0
-2.3.1 SILC Packet Payloads
-
-All payloads resides in the main data area of the SILC packet. However
-all payloads must be at the start of the data area after the default
-SILC packet header and padding. All fields in the packet payload are
-always encrypted, as, they reside in the data area of the packet which
-is always encrypted.
-
-Payloads described in this section are common payloads that must be
-accepted anytime during SILC session. Most of the payloads may only
-be sent with specific packet type which is defined in the description
-of the payload.
-
-There are a lot of other payloads in the SILC as well. However, they
-are not common in the sense that they could be sent at any time.
-These payloads are not described in this section. These are payloads
-such as SILC Key Exchange payloads and so on. These are described
-in [SILC1] and [SILC3].
-
-
-.ti 0
-2.3.2 Disconnect Payload
-
-Disconnect payload is sent upon disconnection. The payload is simple;
-reason of disconnection is sent to the disconnected party.
-
-The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
-must not be sent in any other packet type. Following diagram represents
-the Disconnect Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Disconnect Message ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 3: Disconnect Payload
-
-
-
-
-.in 6
-o Disconnect Message (variable length) - Human readable
- reason of the disconnection.
-.in 3
-
-
-.ti 0
-2.3.3 Success Payload
-
-Success payload is sent when some protocol execution is successfully
-completed. The payload is simple; indication of the success is sent.
-This maybe any data, including binary or human readable data.
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Success Indication ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 4: Success Payload
-
-
-.in 6
-o Success Indication (variable length) - Indication of
- the success. This maybe for example some flag that
- indicates the protocol and the success status or human
- readable success message. The true length of this
- payload is available by calculating it from the SILC
- Packet Header.
-.in 3
-
-
-.ti 0
-2.3.4 Failure Payload
-
-This is opposite of Success Payload. Indication of failure of
-some protocol is sent in the payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Failure Indication ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 5: Failure Payload
-
-
-.in 6
-o Failure Indication (variable length) - Indication of
- the failure. This maybe for example some flag that
- indicates the protocol and the failure status or human
- readable failure message. The true length of this
- payload is available by calculating it from the SILC
- Packet Header.
-.in 3
-
-
-.ti 0
-2.3.5 Reject Payload
-
-This payload is sent when some protocol is rejected to be executed.
-Other operations may send this as well that was rejected. The
-indication of the rejection is sent in the payload. The indication
-may be binary or human readable data.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Reject Indication ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 6: Reject Payload
-
-
-.in 6
-o Reject Indication (variable length) - Indication of
- the rejection. This maybe for example some flag that
- indicates the protocol and the rejection status or human
- readable rejection message. The true length of this
- payload is available by calculating it from the SILC
- Packet Header.
-.in 3
-
-
-
-
-
-.ti 0
-2.3.6 Notify Payload
-
-Notify payload is used to send notify messages. The payload is usually
-sent from server to client, however, server may send it to another
-server as well. Client must not send this payload. The receiver of
-this payload may totally ignore the contents of the payload, however,
-notify message should be noted and possibly logged.
-
-The payload may only be sent with SILC_PACKET_NOTIFY packet. It must
-not be sent in any other packet type. Following diagram represents the
-Notify Payload.
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Notify Type | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Notify Message ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 7: Notify Payload
-
-
-.in 6
-o Notify Type (2 bytes) - Indicates the type of the notify
- message.
-
-o Notify Message (variable length) - Human readable notify
- message.
-.in 3
-
-
-.ti 0
-2.3.7 Error Payload
-
-Error payload is sent upon error. Error may occur in various
-conditions when server sends this packet. Client may not send this
-payload but must be able to accept it. However, client may
-totally ignore the contents of the packet as server is going to
-take action on the error anyway. However, it is recommended
-that the client takes error packet seriously.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Error Message ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 8: Error Payload
-
-
-.in 6
-o Error Message (variable length) - Human readable error
- message.
-.in 3
-
-
-.ti 0
-2.3.8 Channel Message Payload
-
-Channel messages are the most common messages sent in the SILC.
-Channel Message Payload is used to send message to channels. These
-messages can only be sent if client has joined to some channel.
-Even though this packet is the most common in SILC it is still
-special packet. Some special handling on sending and reception
-of channel message is required.
-
-Padding must be applied into this payload since the payload is
-encrypted separately from other parts of the packet with the
-channel specific key. Hence the requirement of the padding.
-The padding should be random data. The packet must be made
-multiple by eight (8) or by the block size of the cipher, which
-ever is larger.
-
-The SILC header in this packet is encrypted with the session key
-of the next receiver of the packet. Nothing else is encrypted
-with that key. Thus, the actual packet and padding to be
-encrypted with the session key is SILC Header plus padding to it
-to make it multiple by eight (8) or multiple by the block size
-of the cipher, which ever is larger.
-
-Receiver of the the channel message packet is able to determine
-the channel the message is destined to by checking the destination
-ID from the SILC Packet header which tells the destination channel.
-The original sender of the packet is also determined by checking
-the source ID from the header which tells the client who sent
-the message.
-
-The payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
-It must not be sent in any other packet type. Following diagram
-represents the Channel Message Payload.
-
-(*) indicates that the field is not encrypted.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Nickname Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Nickname ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Message Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Message Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Padding Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Padding ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Initial Vector * ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 9: Channel Message Payload
-
-
-.in 6
-o Nickname Length (2 bytes) - Indicates the length of the
- Nickname field, not including any other field.
-
-o Nickname (variable length) - Nickname of the sender of the
- channel message. This should not be trusted as a definite
- sender of the channel message. The SILC Packet Header in
- the packet indicates the true sender of the packet and
- client should verify that the nickname sent here belongs
- to the Client ID in the SILC Packet Header. This nickname
- is merely provided to be displayed by the client.
-
- If server is sending this packet this field is not included
- and zero (0) length must be set to the Nickname Length field.
-
-o Message Length (2 bytes) - Indicates the length of the
- the Message Data field in the payload, not including any
- other field.
-
-
-o Message Data (variable length) - The actual message to
- the channel.
-
-o Padding Length (2 bytes) - Indicates the length of the
- Padding field in the payload, not including any other
- field.
-
-o Padding (variable length) - The padding that must be
- applied because this payload is encrypted separately from
- other parts of the packet.
-
-o Initial Vector (variable length) - The initial vector
- that has been used in packet encryption. It needs to be
- used in the packet decryption as well. What this field
- includes is implementation issue. However, it is
- recommended that it would be random data or, perhaps,
- a timestamp. It is not recommended to use zero (0) as
- initial vector. This field is not encrypted. This field
- is not included into the padding calculation. Length
- of this field equals the cipher's block size. This field
- is, however, authenticated.
-.in 3
-
-
-.ti 0
-2.3.9 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 leaves a channel. Server creates the new
-channel key and distributes it to the clients by encrypting this
-payload with the session key shared between the server and
-the client. After that, client starts using the key received
-in this payload to protect the traffic on the channel.
-
-Channel keys are cell specific thus every router in 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 peridiocally, say, in one hour, in
-which case new channel key is created and distributed.
-
-The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
-It must not be sent in any other packet type. Following diagram
-represents the Channel Key Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Channel ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Channel ID ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Cipher Name Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Cipher Name ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Channel Key Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Channel Key ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 10: Channel Key Payload
-
-
-
-.in 6
-o Channel ID Length (2 bytes) - Indicates the length of the
- Channel ID field in the payload, not including any other
- field.
-
-o Channel ID (variable length) - The Channel ID of the
- channel this key is meant for.
-
-o Cipher Name Length (2 bytes) - Indicates the length of the
- Cipher name field in the payload, not including any other
- field.
-
-o Cipher Name (variable length) - Name of the cipher used
- in the protection of channel traffic. This name is
- initially decided by the creator of the channel but it
- may change during the life time of the channel as well.
-
-o Channel Key Length (2 bytes) - Indicates the length of the
- Channel Key field in the payload, not including any other
- field.
-
-o Channel Key (variable length) - The actual channel key
- material. This key is used as such as key material for
- encryption function.
-.in 3
-
-
-.ti 0
-2.3.10 Private Message Payload
-
-Private Message Payload is used to send private message between
-two clients (or users for that matter). The messages are sent only
-to the specified user and no other user inside SILC network is
-able to see the message. The message is protected by the session
-key established by the SILC Key Exchange Protocol. However,
-it is also possible to agree to use specific keys to protect
-just the private messages. See section 2.3.11 Private Message
-Key Payload for detailed description of how to agree to use
-specific key.
-
-If normal session key is used to protect the message, every
-server between the sender client and the receiving client needs
-to 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 specific key is used to protect the message, servers between
-the sender and the receiver needs not to decrypt/re-encrypt the
-packet. Section 4.8.2 Client To Client in [SILC1] gives example of
-this scheme as well.
-
-The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
-packet. It must not be sent in any other packet type. Following
-diagram represents the Private Message Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Nickname Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Nickname ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Message Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 11: Private Message Payload
-
-
-.in 6
-o Nickname Length (2 bytes) - Indicates the length of the
- Nickname field, not including any other field.
-
-o Nickname (variable length) - Nickname of the sender of the
- private message. This should not be trusted as a definite
- sender of the private message. The SILC Packet Header in
- the packet indicates the true sender of the packet and
- client should verify that the nickname sent here belongs
- to the Client ID in the SILC Packet Header. This nickname
- is merely provided to be displayed by the client.
-
-o Message Data (variable length) - The actual message to
- the client. Rest of the packet is reserved for the message
- data.
-.in 3
-
-
-.ti 0
-2.3.11 Private Message Key Payload
-
-This payload is used to send key from client to another client that
-is going to be used to protect the private messages between these
-two clients. If this payload is not sent normal session key
-established by the SILC Key Exchange Protocol is used to protect
-the private messages.
-
-This payload may only be sent by client to another client. Server
-must not send this payload at any time. After sending this payload
-the sender of private messages must set the Private Message Key
-flag into SILC Packet Header.
-
-The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
-packet. It must not be sent in any other packet type. Following
-diagram represents the Private Message Key Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Private Message Key Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Private Message Key ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 12: Private Message Key Payload
-
-
-
-
-.in 6
-o Private Message Key Length (2 bytes) - Indicates the length
- of the Private Message Key field in the payload, not including
- any other field.
-
-o Private Message Key (variable length) - The actual private
- message key material. This key is used as such as key material
- for encryption function.
-.in 3
-
-
-.ti 0
-2.3.12 Command Payload
-
-Command Payload is used to send SILC commands from client to server.
-Also server may send commands to other servers. Following diagram
-represents the Command Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Payload Length | SILC Command | Arguments Num |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Command Unifier |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 13: Command Payload
-
-
-.in 6
-o Payload Length (2 bytes) - Length of the entire command
- payload including any command argument payloads associated
- with this payload.
-
-o SILC Command (1 byte) - SILC Command identifier. 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.
-
-o Command Unifier (2 bytes) - Unifies this command at the
- sender's end. The entity who replies to this command must
- set the value found from this field into the Command Payload
- used to send the reply to the sender. This way the sender
- can identify which command reply belongs to which originally
- sent command. What this field includes is implementation
- issue but it is recommended that wrapping counter value is
- used in the field.
-.in 3
-
-See [SILC1] for detailed description of different SILC commands,
-their arguments and their reply messages.
-
-
-.ti 0
-2.3.12.1 Command Argument Payload
-
-Command Argument Payload is used to set arguments for SILC commands.
-Number of arguments associated with a command are indicated by the
-Command Payload in the Arguments Num field. Command argument
-payloads may only be used with a command payload and they must
-always reside right after the command payload. Incorrect amount of
-argument payloads must cause rejection of the packet. Following
-diagram represents the Command Argument Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Argument Num | Argument Type | Payload Length |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Argument Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 14: Command Argument Payload
-
-
-.in 6
-o Argument Num (1 byte) - Indicates the number of this argument.
- For first argument this is set to 1, for second argument this
- is set to 2, and so forth. If incorrect value is found
- in this field the packet must be discarded. Value is
- incorrect if it is zero (0) or, for example, a third argument
- does not include value 3.
-
-o Argument Type (1 byte) - Indicates the type of the argument.
- Every command specify a number for each argument that maybe
- associated with the command. By using this number the receiver
- of the packet knows what type of argument this is. The numbers
- are command specific and has been defined in section SILC
- Commands in [SILC1]. This field makes it possible to send
- arguments in free order as this field is used to identify
- the specific type of the argument.
-
-o Payload Length (2 bytes) - Length of the argument payload data
- area not including the length of any other fields in the
- payload.
-
-o Argument Data (variable length) - Argument data.
-.in 3
-
-
-.ti 0
-2.3.13 Command Reply Payload
-
-Command Reply Payload is used to send replies to the commands. The
-Command Reply Payload is identical to the Command Payload thus see the
-upper sections for Command Payload and for Command Argument Payload
-specifications. Command Reply message uses the Command Argument Payload
-as well.
-
-The entity who sends the reply packet must set the Command Unifier
-field in the reply packet's Command Payload to the value it received
-in the original command packet.
-
-See SILC Commands in [SILC1] for detailed description of different
-SILC commands, their arguments and their reply messages.
-
-
-.ti 0
-2.3.14 Connection Auth Request Payload
-
-Client may send this payload to server to request the authentication
-method that must be used in authentication protocol. If client knows
-this information beforehand this payload is not necessary to be sent.
-Server performing authentication with another server may also send
-this payload to request the authentication method. If the connecting
-server already knows this information this payload is not necessary
-to be sent.
-
-Server receiving this request must reply with same payload sending
-the mandatory authentication method. Algorithms that may be required
-to be used by the authentication method are the ones already
-established by the SILC Key Exchange protocol. See section Key
-Exchange Start Payload in [SILC3] for detailed information.
-
-The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
-packet. It must not be sent in any other packet type. Following
-diagram represents the Connection Auth Request Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Connection Type | Authentication Method |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 15: Connection Auth Request Payload
-
-
-.in 6
-o Connection Type (2 bytes) - Indicates the type of the ID.
- 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. Following
- authentication methods are defined:
-
-
-
- 0 NONE (mandatory)
- 1 password (mandatory)
- 2 public key (mandatory)
-
- If any other type is found in this field the packet must be
- discarded and the authentication must be failed. If this
- payload is sent as request to receive the mandatory
- authentication method this field must be set to zero (0),
- indicating that receiver should send the mandatory
- authentication method. The receiver sending this payload
- to the requesting party, may also set this field to zero (0)
- to indicate that authentication is not required. In this
- case authentication protocol still must be started but
- server is most likely to respond with SILC_PACKET_SUCCESS
- immediately.
-.in 3
-
-
-.ti 0
-2.3.15 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. Similiary when router
-distributes information to other routers about the client in the SILC
-network this payload is used.
-
-Also, when server connects to router, router uses this payload to inform
-other routers about new server in the SILC network. However, every
-server (or router) creates their own ID's thus the ID distributed by
-this payload is not created by the distributor in this case. Servers
-create their own ID's. Server registers itself to the network by sending
-SILC_PACKET_NEW_SERVER to the router it connected to. The case is same
-when router connects to another router.
-
-Hence, this payload is very important and used every time when some
-new entity is registered to the SILC network. Client never sends this
-payload. Both client and server (and router) may receive this payload.
-
-The payload may only be sent with SILC_PACKET_NEW_ID packet. It must
-not be sent in any other packet type. Following diagram represents the
-New ID Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| ID Type | ID Length |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 16: New ID Payload
-
-
-.in 6
-o ID Type (2 bytes) - Indicates the type of the ID. See
- section 2.4 SILC ID Types for list of defined ID types.
-
-o ID Length (2 bytes) - Length of the ID Data area not
- including the length of any other fields in the payload.
-
-o ID Data (variable length) - The actual ID data.
-.in 3
-
-
-
-.ti 0
-2.3.16 New ID List Payload
-
-New ID List Payload is used to distribute list of ID's usually from
-server to router but also from router to other routers in the network.
-This payload is used, for example, when server is connected to router
-and the server wants to distribute all of its locally connected clients
-and locally created channels to the router. It is convenient in this
-case to use this payload instead of sending all the information one
-by one using New ID Payload.
-
-There is no specific payload for this packet type. The packet type
-uses same payload as described in previous section. To form a list
-several payloads is put in the packet each after each. The payload
-is variable in length but can be calculated by calculating the ID
-Type field, Length field and the ID Data fields together. This forms
-one New ID Payload in the list.
-
-The list of payloads may only be sent with SILC_PACKET_NEW_ID_LIST
-packet. They must not be sent in any other packet type.
-
-
-.ti 0
-2.3.17 New Client Payload
-
-When client is connected to the server, keys has been exchanged and
-connection has been authenticated client must register itself to the
-server. Clients first packet after key exchange and authentication
-protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
-the relevant information about the connected user. Server creates a new
-client ID for the client when received this payload and sends it to the
-client in New ID Payload.
-
-This payload sends username and real name of the user on the remote host
-which is connected to the SILC server with SILC client. The server
-creates the client ID according the information sent in this payload.
-The nickname of the user becomes the username sent in this payload.
-However, client should call NICK command after sending this payload to
-set the real nickname of the user which is then used to create new
-client ID.
-
-The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
-must not be sent in any other packet type. Following diagram represents
-the New Client Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Username Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Username ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Real Name Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Real Name ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 17: New Client Payload
-
-
-.in 6
-o Username Length (2 bytes) - Length of the username.
-
-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.
-
-o Real Name (variable length) - The real name of the user
- on the host where connecting to the SILC server.
-.in 3
-
-
-.ti 0
-2.3.18 New Server Payload
-
-This payload is sent by server when it has completed successfully both
-key exchange and connection authentication protocols. The server
-uses this payload to register itself to the SILC network. 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. Following diagram represents
-the New Server Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Server ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Server ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Server Name Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Server Name ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 18: New Server Payload
-
-
-.in 6
-o Server ID Length (2 bytes) - Length of the ID Data area not
- including the length of any other fields in the payload.
-
-o Server ID Data (variable length) - The actual Server ID
- data.
-
-o Server Name Length (2 bytes) - Length of the server name.
-
-o Server Name (variable length) - The server name.
-.in 3
-
-
-.ti 0
-2.3.19 New Channel Payload
-
-Information about newly created channel is broadcasted to all routers
-in the SILC network by sending this packet payload. Channels are
-created by router of the cell. Server never creates channels unless
-it is a standalone server and it does not have router connection,
-in this case server acts as router. Normal server forwards JOIN command
-to the router (after it has received JOIN command from client) which
-then processes the command and creates the channel. Client never sends
-this packet.
-
-The payload may only be sent with SILC_PACKET_NEW_CHANNEL packet.
-It must not be sent in any other packet type. Following diagram
-represents the New Channel Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Channel Name Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Channel Name ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Channel ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Channel ID ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 19: New Channel Payload
-
-
-
-.in 6
-o Channel Name Length (2 bytes) - Length of the channel name.
-
-o Channel Name (variable length) - The name of the created
- channel.
-
-o Channel ID Length (2 bytes) - Length of the Channel ID.
-
-o Channel ID (variable length) - The created Channel ID.
-.in 3
-
-
-.ti 0
-2.3.20 New Channel User Payload
-
-When client (user) joins to a channel, server must notify routers
-about the new user on the channel. Normal server sends this packet
-payload to its router which then broadcasts the packet further.
-Router sends this packet always to its primary router. Client must
-not send this packet payload. The mode of the user is NONE after
-user has joined to the channel.
-
-The payload may only be sent with SILC_PACKET_NEW_CHANNEL_USER
-packet. It must not be sent in any other packet type. Following
-diagram represents the New Channel User Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Channel ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Channel ID ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Client ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Client ID ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 20: New Channel User Payload
-
-
-.in 6
-o Channel ID Length (2 bytes) - Length of the Channel ID.
-
-o Channel ID (variable length) - The Channel ID of the channel
- to which the client has joined.
-
-o Client ID Length (2 bytes) - Length of the Client ID.
-
-o Client ID (variable length) - The Client ID of the client
- who has joined the channel.
-.in 3
-
-
-.ti 0
-2.3.21 New Channel List Payload
-
-This payload is used to distribute list of new channels from server
-to routers. It might convenient to send list of new channels when
-existing server connects to router, instead of sending them one
-by one.
-
-There is no specific payload for this packet type. The packet type
-uses same payload as described in 2.3.19 New Channel Payload. To form
-a list several payloads is put in the packet each after each. The
-payload is variable in length but can be calculated by calculating
-the length of the fields together. This forms one New Channel Payload
-in the list.
-
-The list of payloads may only be sent with SILC_PACKET_NEW_CHANNEL_LIST
-packet. They must not be sent in any other packet type.
-
-
-.ti 0
-2.3.22 New Channel User List Payload
-
-This payload is used to distribute list of channel users on specific
-channel from server to routers. It might convenient to send list of
-channel users when existing server connects to router, instead of
-sending them one by one.
-
-There is no specific payload for this packet type. The packet type
-uses same payload as described in 2.3.20 New Channel User Payload.
-To form a list several payloads is put in the packet each after each.
-The payload is variable in length but can be calculated by calculating
-the length of the fields together. This forms one New Channel User
-Payload in the list.
-
-The list of payloads may only be sent with packet
-SILC_PACKET_NEW_CHANNEL_USER_LIST. They must not be sent in any other
-packet type.
-
-
-.ti 0
-2.3.23 Replace ID Payload
-
-This payload is used to replace old ID with new ID sent in the payload.
-When ID changes for some entity and the new ID is wanted to replace the
-old one this payload must be used. Client cannot send or receive this
-payload. Normal server and router server may send and receive this
-payload. After this packet has been sent the old ID must not be used
-anymore.
-
-The payload may only be sent with SILC_PACKET_REPLACE_ID packet. It must
-not be sent in any other packet type. Following diagram represents the
-Replace Payload Payload.
-
-
-
-
-
-
-
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Old ID Type | Old ID Length |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ Old ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| New ID Type | New ID Length |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ New ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 21: Replace ID Payload
-
-
-.in 6
-o Old ID Type (2 bytes) - Indicates the type of the old ID. See
- section 2.4 SILC ID Types for list of defined ID types.
-
-o Old ID Length (2 bytes) - Length of the old ID Data area not
- including the length of any other fields in the payload.
-
-o Old ID Data (variable length) - The actual old ID data.
-
-o New ID Type (2 bytes) - Indicates the type of the new ID. See
- section 2.4 SILC ID Types for list of defined ID types.
-
-o New ID Length (2 bytes) - Length of the new ID Data area not
- including the length of any other fields in the payload.
-
-o New ID Data (variable length) - The actual new ID data.
-.in 3
-
-
-.ti 0
-2.3.24 Remove ID Payload
-
-Remove ID payload is used to remove ID from SILC network. This is used
-for example when client exits SILC network. The server must in this
-case send this payload to notify that this ID is not valid anymore.
-After this has been send the old ID must not be used anymore. Client
-must not send this payload.
-
-The payload may only be sent with SILC_PACKET_REMOVE_ID packet. It must
-not be sent in any other packet type. Following diagram represents the
-Remove Payload Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| ID Type | ID Length |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| |
-~ ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 22: Remove ID Payload
-
-
-.in 6
-o ID Type (2 bytes) - Indicates the type of the ID to be
- removed. 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 to be removed.
-.in 3
-
-
-.ti 0
-2.3.25 Remove Channel User Payload
-
-Remove Channel User payload is used to remove a user from a channel network
-wide. This is used by routers to notify other routers that a user has
-leaved a channel. As routers keep information about users on channels a
-user leaving channel must be removed from all routers. Normal server may
-send this payload as well. Client must not send this payload.
-
-The payload may only be sent with SILC_PACKET_REMOVE_CHANNEL USER packet.
-It must not be sent in any other packet type. Following diagram
-represents the Remove Payload Payload.
-
-
-.in 5
-.nf
- 1 2 3
- 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Client ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Client ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Channel ID Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
-~ Channel ID Data ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-.in 3
-
-.ce
-Figure 23: Remove Channel User Payload
-
-
-.in 6
-o Client ID Length (2 bytes) - Length of the Client ID Data area
- not including the length of any other fields in the payload.
-
-o Client ID Data (variable length) - The Client ID of the user
- that has left the channel.
-
-o Channel ID Length (2 bytes) - Length of the Channel ID Data area
- not including the length of any other fields in the payload.
-
-o Channel ID Data (variable length) - The Channel ID of the channel
- the user has left.
-.in 3
-
-
-.ti 0
-2.4 SILC ID Types
-
-ID's are extensively used in the SILC network to associate different
-entities. Following ID's has been defined to be used in the SILC
-network.
-
-.in 6
-0 No ID
-
- When ever specific ID cannot be used this is used.
-
-1 Server ID
-
- Server ID to associate servers. See the format of
- this ID in [SILC1].
-
-2 Client ID
-
- Client ID to associate clients. See the format of
- this ID in [SILC1].
-
-3 Channel ID
-
- Channel ID to associate channels. See the format of
- this ID in [SILC1].
-.in 3
-
-
-.ti 0
-2.5 Packet Encryption And Decryption
-
-SILC packets are encrypted almost entirely. Only small part of SILC
-header is not encrypted as described in section 5.2 SILC Packet Header.
-The SILC Packet header is the first part of a packet to be encrypted
-and it is always encrypted with the key of the next receiver of the
-packet. The data payload area of the packet is always entirely
-encrypted and it is usually encrypted with the next receiver's key.
-However, there are some special packet types and packet payloads
-that require special encryption process. These special cases are
-described in the next sections. First is described the normal packet
-encryption process.
-
-
-.ti 0
-2.5.1 Normal Packet Encryption And Decryption
-
-Normal SILC packets are encrypted with the session key of the next
-receiver of the packet. The entire SILC Packet header and the packet
-data payload is is also encrypted with the same key. Padding of the
-packet is also encrypted always with the session key, also in special
-cases. Computed MAC of the packet must not be encrypted.
-
-Decryption process in these cases are straightforward. The receiver
-of the packet must first decrypt the SILC Packet header, or some parts
-of it, usually first 16 bytes of it. Then the receiver checks the
-packet type from the decrypted part of the header and can determine
-how the rest of the packet must be decrypted. If the packet type is
-any of the special cases described in following sections the packet
-decryption is special. If the packet type is not among those special
-packet types rest of the packet may be decrypted with the same key.
-
-Also, note that two bytes of the SILC Packet header are not encrypted
-thus it must be noticed in the decryption process by starting the
-decryption from the second byte of the header. This sets some rules
-to padding generation as well, see the section 2.7 Packet Padding
-Generation.
-
-With out a doubt, this sort of decryption processing causes some
-overhead to packet decryption, but never the less, is required.
-
-
-.ti 0
-2.5.2 Channel Message Encryption And Decryption
-
-Channel Messages (Channel Message Payload) are always encrypted with
-the channel specific key. However, the SILC Packet header is not
-encrypted with that key. As in normal case, the header is encrypted
-with the key of the next receiver of the packet, who ever that might
-be. Note that in this case the encrypted data area is not touched
-at all; it must not be re-encrypted with the session key.
-
-Receiver of a channel message, who ever that is, is required to decrypt
-the SILC Packet header to be able to even recognize the packet to be as
-channel message. This is same procedure as for normal SILC packets.
-As the receiver founds the packet to be channel message, rest of the
-packet processing is special. Rest of the SILC Packet header is
-decrypted with the same session key along with the padding of the
-packet. After that the packet is protected with the channel specific
-key and hence 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 who is routing the
-message to another router then it must decrypt the Channel Message
-payload. Between routers (that is, between cells) channel messages
-are protected with session keys shared between the routers. This
-causes another special packet processing for channel messages. If
-the channel message is received from another router then the entire
-packet, including Channel Message payload, is encrypted with the
-session key shared between the routers. In this case the packet
-decryption process is as with normal SILC packets. Hence, if the
-router is sending channel message to another router the Channel
-Message payload must have been decrypted and must be re-encrypted
-with the session key shared between the another router. In this
-case the packet encryption is as with any normal SILC packet.
-
-It must be noted that this is only when the channel messages are sent
-from router to another router. In all other cases the channel
-message encryption and decryption is as described above. This
-different processing of channel messages with router to router
-connection is because channel keys are cell specific. All cells has
-their own channel keys thus the channel message traveling from one
-cell to another must be protected as it would be any normal SILC
-packet.
-
-
-.ti 0
-2.5.3 Private Message Encryption And Decryption
-
-By default, private message in SILC are protected by session keys.
-In this case the private message encryption and decryption process is
-equivalent to normal packet encryption and decryption.
-
-However, private messages can be protected with private message key
-which causes the packet to be special packet. The procedure in this
-case is very much alike to channel packets. The actual private message
-is encrypted with the private message key and other parts of the
-packet is encrypted with the session key. See 2.7 Packet Padding
-Generation for more information about padding on special packets.
-
-The difference from channel message processing is that server or router
-en route never decrypts the actual private message, as it does not
-have the key to do that. Thus, when sending packets between router
-the processing is same as in any other case as well; the packet's header
-and padding is protected by the session key and the data area is not
-touched.
-
-The true receiver of the private message, client, that is, is able
-to decrypt the private message as it shares the key with the sender
-of the message.
-
-
-.ti 0
-2.6 Packet MAC Generation
-
-Data integrity of a packet is protected by including a message
-authentication code (MAC) at the end of the packet. The MAC is computed
-from shared secret MAC key, that is established by the SILC Key Exchange
-protocol, and from the original contents of the packet. The MAC is
-always computed before the packet is encrypted, although after it is
-compressed if compression is used.
-
-The MAC is computed from entire packet. Every bit of data in the packet,
-including SILC Packet Header is used in the MAC computing. This way
-the entire packet becomes authenticated.
-
-If the packet is special packet MAC is computed from the entire packet
-but part of the packet may be encrypted before the MAC is computed.
-This is case, for example, with channel messages where the message data
-is encrypted with key that server may not now. In this case the MAC
-has been computed from the encrypted data.
-
-See [SILC1] for defined and allowed MAC algorithms.
-
-
-.ti 0
-2.7 Packet Padding Generation
-
-Padding is needed in the packet because the packet is encrypted. It
-must always be multiple by eight (8) or multiple by the size of the
-cipher's block size, which ever is larger. The padding is always
-encrypted.
-
-For normal packets the padding is added after the SILC Packet Header
-and between the Data Payload area. The padding for normal packets
-are calculated as follows:
-
-.in 6
-padding length = 16 - ((packet length - 2) % 16)
-.in 3
-
-The 16 is the maximum padding allowed in SILC packet. Two (2) is
-subtracted from the true length of the packet because two (2) bytes
-is not encrypted in SILC Packet Header, see section 2.2 SILC Packet
-Header. Those two bytes that are not encrypted must not be calculated
-to the padding length.
-
-For special packets the padding calculation may be different as special
-packets may be encrypted differently. In these cases the encrypted
-data area must already be multiple by the block size thus in this case
-the padding is calculated only for SILC Packet Header, not for any
-other area of the packet. The same algorithm works in this case as
-well, except that the `packet length' is now the SILC Packet Header
-length. In this case, as well, two (2) is subtracted from the
-length.
-
-The padding must be random data, preferably, generated by
-cryptographically strong random number generator.
-
-
-.ti 0
-2.8 Packet Compression
-
-SILC Packets may be compressed. In this case the data payload area
-is compressed and all other areas of the packet must remain as they
-are. After compression is performed for the data area, the length
-field of Packet Header must be set to the compressed length of the
-data.
-
-The compression must always be applied before encryption. When
-the packet is received and decrypted the data area must be decompressed.
-Note that the true sender of the packet must apply the compression and
-the true receiver of the packet must apply the decompression. Any
-server or router en route must not decompress the packet.
-
-
-.ti 0
-2.9 Packet Sending
-
-The sender of the packet must assemble the SILC Packet Header with
-correct values. It must set the Source ID of the header as its own
-ID, unless it is forwarding the packet. It must also set the Destination
-ID of the header to the true destination. If the destination is client
-it will be Client ID, if it is server it will be Server ID and if it is
-channel it will be Channel ID.
-
-If the sender wants to compress the packet it must apply the
-compression now. Sender must also compute the padding as described
-in above sections. Then sender must compute the MAC of the packet.
-
-Then sender encrypts the packet as has been described in above
-sections according whether the packet is normal packet or special
-packet. The computed MAC must not be encrypted.
-
-
-.ti 0
-2.10 Packet Reception
-
-On packet reception the receiver must check that all fields in the
-SILC Packet Header are valid sain. It must check the flags of the
-header and act accordingly. It must also check the MAC of the packet
-and if it is to be failed the packet must be discarded. Also if the
-header of the packet includes any bad fields the packet must be
-discarded.
-
-See above sections on the decryption process of the received packet.
-
-The receiver must also check that the ID's in the header are valid
-ID's. Unsupported ID types or malformed ID's must cause packet
-rejection. The padding on the reception is always ignored.
-
-The receiver must also check the packet type and start parsing the
-packet according to the type. However, note the above sections on
-special packet types and their parsing.
-
-
-.ti 0
-2.11 Packet Routing
-
-Routers are the primary entities in the SILC network that takes care
-of packet routing. However, normal servers routes packets as well, for
-example, when they are routing channel message to the local clients.
-Routing is quite simple as every packet tells the true origin and the
-true destination of the packet.
-
-It is still recommended for routers that has several routing connections
-to create route cache for those destinations that has faster route than
-the router's primary route. This information is available for the router
-when other router connects to the router. The connecting party then
-sends all of its locally connected clients, server and channels. These
-informations helps to create the route cache. Also, when new channels
-are created to a cell its information is broadcasted to all routers
-in the network. Channel ID's are based on router's ID thus it is easy
-to create route cache based on these informations. If faster route for
-destination does not exist in router's route cache the packet must be
-routed to the primary route (default route).
-
-For server who receives a packet to be routed to its locally connected
-client the server must check whether the particular packet type is
-allowed to be routed to the client. Not all packets may be sent by
-some odd entity to client that is indirectly connected to the sender.
-See section 2.3 SILC Packet Types and paragraph about indirectly connected
-entities and sending packets to them. The section mentions the packets
-that may be sent to indirectly connected entities. It is clear that some
-server cannot send, for example, disconnect packet to client that is not
-directly connected to the server.
-
-
-.ti 0
-2.12 Packet Forwarding
-
-Currently SILC command packets may be forwarded from one entity to another.
-Any other packet currently cannot be forwarded but support for more packet
-types may be added if needed. Forwarding is usually used by server to
-forward some command request coming from client to the router as the server
-may be incapable to handle the request. Forwarding may be only one hop
-long; the receiver of the packet with Forwarded flag set in the SILC
-Packet header must not forward the packet any further.
-
-The normal scenario is that client sends JOIN command to the server which
-is not able to create the channel as there are no local clients on the
-channel. Channels are created always by the router of the cell thus the
-packet must be forwarded to the router. The server forwards the original
-packet coming from client to the router after it has set the Forwarded
-flag to the SILC Packet header.
-
-Router receiving the packet knows that the packet has to be processed
-specially by checking the flags and the Forwarded flag in the SILC Packet
-header. After router has joined the client to the channel (and perhaps
-created a new channel) it sends normal command reply packet to the
-client. However, as the router doesn't have direct connection to the
-client the packet is sent through the server. Server detects that
-the command reply packet is destined to the client and sends it to
-the client.
-
-
-.ti 0
-2.13 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 may
-cause problems, such as race conditions inside the SILC network, if
-care is not taken when broadcasting packets. Router must not send
-the broadcast packet to any other route except to its primary route.
-
-If the primary route of the router is the original sender of the packet
-the packet must not be sent to the primary route. This may happen
-if router has several router connections and some other router uses
-the router as its primary route.
-
-Routers use broadcast packets to broadcast for example information
-about newly registered clients, servers, channels etc. so that all the
-routers may keep these informations up to date.
-
-
-.ti 0
-2.14 Packet Tunneling
-
-Tunneling is a feature that is available in SILC protocol. Tunneling
-means that extra SILC Packet Header is applied to the original packet
-and thus hiding the original packet entirely. There can be some
-interesting applications using tunneling, such as, using ID's based on
-private network IP addresses inside in the tunneled packet. This can
-open many interesting features relating to connecting to private network
-from the Internet with SILC and many more. However, this feature is
-optional currently in SILC as there does not exist thorough analysis of
-this feature. It is with out a doubt that there will be many more
-applications that has not yet been discovered. Thus, it is left
-to Internet Community to investigate the use of tunneling in SILC
-protocol. This document is updated according those investigations
-and additional documents on the issue may be written.
-
-
-.ti 0
-3 Security Considerations
-
-Security is central to the design of this protocol, and these security
-considerations permeate the specification.
-
-
-.ti 0
-4 References
-
-[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
- Protocol Specification", Internet Draft, June 2000.
-
-[SILC3] Riikonen, P., "SILC Key Exchange and Authentication
- Protocols", Internet Draft, June 2000.
-
-[IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
- RFC 1459, May 1993.
-
-[SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
- Internet Draft.
-
-[PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
- November 1998.
-
-[SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
- September 1999.
-
-[PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
- Infrastructure, Certificate and CRL Profile", RFC 2459,
- January 1999.
-
-[Schneier] Schneier, B., "Applied Cryptography Second Edition",
- John Wiley & Sons, New York, NY, 1996.
-
-[Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
- CRC Press 1997.
-
-[OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
- RFC 2412, November 1998.
-
-[ISAKMP] Maughan D., et al, "Internet Security Association and
- Key Management Protocol (ISAKMP)", RFC 2408, November
- 1998.
-
-[IKE] Harkins D., and Carrel D., "The Internet Key Exhange
- (IKE)", RFC 2409, November 1998.
-
-[HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
- Authentication", RFC 2104, February 1997.
-
-
-.ti 0
-5 Author's Address
-
-.nf
-Pekka Riikonen
-Kasarmikatu 11 A4
-70110 Kuopio
-Finland
-
-EMail: priikone@poseidon.pspt.fi
-
-This Internet-Draft expires 13 May 2001
projects / crypto.git / blobdiff