From a26f05148fd68ac6fec166a82664d22f7c505c0a Mon Sep 17 00:00:00 2001 From: Pekka Riikonen Date: Fri, 29 Sep 2000 07:10:06 +0000 Subject: [PATCH] Created. --- doc/draft-riikonen-silc-ke-auth-01.nroff | 1055 ++++++++ doc/draft-riikonen-silc-pp-01.nroff | 2470 +++++++++++++++++ doc/draft-riikonen-silc-spec-01.nroff | 3094 ++++++++++++++++++++++ lib/silccore/silcnotify.h | 36 + 4 files changed, 6655 insertions(+) create mode 100644 doc/draft-riikonen-silc-ke-auth-01.nroff create mode 100644 doc/draft-riikonen-silc-pp-01.nroff create mode 100644 doc/draft-riikonen-silc-spec-01.nroff create mode 100644 lib/silccore/silcnotify.h diff --git a/doc/draft-riikonen-silc-ke-auth-01.nroff b/doc/draft-riikonen-silc-ke-auth-01.nroff new file mode 100644 index 00000000..f385571a --- /dev/null +++ b/doc/draft-riikonen-silc-ke-auth-01.nroff @@ -0,0 +1,1055 @@ +.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-ke-auth-01.txt 13 September 2000 +Expires: 13 May 2001 + +.in 3 + +.ce 2 +SILC Key Exchange and Authentication Protocols + + +.ti 0 +Status of this Memo + +This document is an Internet-Draft and is in full conformance with +all provisions of Section 10 of RFC 2026. Internet-Drafts are +working documents of the Internet Engineering Task Force (IETF), its +areas, and its working groups. Note that other groups may also +distribute working documents as Internet-Drafts. + +Internet-Drafts are draft documents valid for a maximum of six months +and may be updated, replaced, or obsoleted by other documents at any +time. It is inappropriate to use Internet-Drafts as reference +material or to cite them other than as "work in progress." + +The list of current Internet-Drafts can be accessed at +http://www.ietf.org/ietf/1id-abstracts.txt + +The list of Internet-Draft Shadow Directories can be accessed at +http://www.ietf.org/shadow.html + +The distribution of this memo is unlimited. + + +.ti 0 +Abstract + +This memo describes two protocols used in the Secure Internet Live +Conferencing (SILC) protocol specified in the Secure Internet Live +Conferencing, Protocol Specification internet-draft [SILC1]. The +SILC Key Exchange (SKE) protocol provides secure key exchange between +two parties resulting into shared secret key material. The protocol +is based on Diffie Hellman key exchange algorithm and its functionality +is derived from several key exchange protocols. SKE uses best parts +of the SSH2 Key Exchange protocol, Station-To-Station (STS) protocol +and the OAKLEY Key Determination protocol [OAKLEY]. + +The SILC Connection Authentication protocol provides user level +authentication used when creating connections in SILC network. The +protocol is transparent to the authentication data which means that it +can be used to authenticate the user with, for example, passphrase +(pre-shared- secret) or public key (and certificate). + + + +.ti 0 +Table of Contents + +.nf +1 Introduction .................................................. 2 +2 SILC Key Exchange Protocol .................................... 3 + 2.1 Key Exchange Payloads ..................................... 3 + 2.1.1 Key Exchange Start Payload .......................... 4 + 2.1.2 Key Exchange 1 Payload .............................. 7 + 2.1.3 Key Exchange 2 Payload .............................. 9 + 2.2 Key Exchange Procedure .................................... 10 + 2.3 Processing the Key Material ............................... 12 + 2.4 SILC Key Exchange Groups .................................. 13 + 2.4.1 diffie-hellman-group1 ............................... 13 + 2.4.2 diffie-hellman-group2 ............................... 14 + 2.5 Key Exchange Status Types ................................. 14 +3 SILC Connection Authentication Protocol ....................... 16 + 3.1 Connection Auth Payload ................................... 17 + 3.2 Connection Authentication Types ........................... 18 + 3.2.1 Passphrase Authentication ........................... 18 + 3.2.2 Public Key Authentication ........................... 18 + 3.3 Connection Authentication Status Types .................... 19 +4 Security Considerations ....................................... 19 +5 References .................................................... 19 +6 Author's Address .............................................. 20 + + +.ti 0 +List of Figures + +.nf +Figure 1: Key Exchange Start Payload +Figure 2: Key Exchange 1 Payload +Figure 3: Key Exchange 2 Payload +Figure 4: Connection Auth Payload + + +.ti 0 +1 Introduction + +This memo describes two protocols used in the Secure Internet Live +Conferencing (SILC) protocol specified in the Secure Internet Live +Conferencing, Protocol Specification internet-draft [SILC1]. The +SILC Key Exchange (SKE) protocol provides secure key exchange between +two parties resulting into shared secret key material. The protocol +is based on Diffie Hellman key exchange algorithm and its functionality +is derived from several key exchange protocols. SKE uses best parts +of the SSH2 Key Exchange protocol, Station-To-Station (STS) protocol +and the OAKLEY Key Determination protocol. + +The SILC Connection Authentication protocol provides user level +authentication used when creating connections in SILC network. The +protocol is transparent to the authentication data which means that it +can be used to authenticate the user with, for example, passphrase +(pre-shared- secret) or public key (and certificate). + +The basis of secure SILC session requires strong and secure key exchange +protocol and authentication. The authentication protocol is entirely +secured and no authentication data is ever sent in the network without +encrypting and authenticating it first. Thus, authentication protocol +may be used only after the key exchange protocol has been successfully +completed. + +This document refers constantly to other SILC protocol specification +Internet Drafts that are a must read for those who wants to understand +the function of these protocols. The most important references are +the Secure Internet Live Conferencing, Protocol Specification [SILC1] +and SILC Packet Protocol [SILC2] Internet Drafts. + +The protocol is intended to be used with the SILC protocol thus it +does not define own framework that could be used. The framework is +provided by the SILC protocol. + + +.ti 0 +2 SILC Key Exchange Protocol + +SILC Key Exchange Protocol (SKE) is used to exchange shared secret +between connecting entities. The result of this protocol is a key +material used to secure the communication channel. The protocol uses +Diffie-Hellman key exchange algorithm and its functionality is derived +from several key exchange protocols. SKE uses best parts of the SSH2 +Key Exchange protocol, Station-To-Station (STS) protocol and the OAKLEY +Key Determination protocol. The protocol does not claim any conformance +to any of these protocols, they were merely used as a reference when +designing this protocol. + +The purpose of SILC Key Exchange protocol is to create session keys to +be used in current SILC session. The keys are valid only for some period +of time (usually an hour) or at most until the session ends. These keys +are used to protect packets like commands, command replies and other +communication between two entities. If connection is server to server +connection, the keys are used to protect all traffic between those +servers. In client connections usually all the packets are protected +with this key except channel messages; channels has their own keys and +they are not exchanged with this protocol. + + +.ti 0 +2.1 Key Exchange Payloads + +During the key exchange procedure public data is sent between initiator +and responder. This data is later used in the key exchange procedure. +There are several payloads used in the key exchange. As for all SILC +packets, SILC Packet Header, described in [SILC2], is at the start of all +packets, the same is done with these payloads as well. All fields in +all payloads are always in MSB (most significant byte first) order. +Following descriptions of these payloads. + + +.ti 0 +2.1.1 Key Exchange Start Payload + +Key exchange between two entities always begins with a +SILC_PACKET_KEY_EXCHANGE packet containing Key Exchange Start Payload. +When performing key exchange between client and server, the client sends +Key Exchange Start Payload to server filled with all security properties +that the client supports. Server then checks if it supports the security +properties. + +It then sends a Key Exchange Start Payload to client filled with security +properties it selected from the payload client originally sent. The +payload sent by server must include only one chosen property per list. + +When performing key exchange between server and server, the server who +is contacting sends the Key Exchange Start Payload with security property +list it supports to the other server. The contacted party then chooses +the preferred properties same way as previously described. It then +replies with the properties it wanted same way as previously described. + +The Key Exchange Start Payload is used to tell connecting entities what +security properties and algorithms should be used in the communication. +If perfect forward secrecy (PFS) is not desired (PFS is undefined by +default) Key Exchange Start Payload is sent only once per session, thus, +for example, re-keying will not cause sending of a new payload. If PFS +is desired, re-keying will always cause new key exchange thus causes +sending of a new Key Exchange Start Payload. + +When performing first key exchange this payload is never encrypted, as +there are no existing keys to encrypt it with. If performing re-keying +(PFS was selected) this payload is encrypted with the existing key and +encryption algorithm. + +Cookie is also send in this payload. Cookie is used to uniform the +payload so that none of the key exchange parties cannot determine this +payload before hand. The cookie must be returned to the original sender +by the responder. + +Following diagram represents the Key Exchange Start Payload. The lists +mentioned below are always comma (`,') separated and the list must +not include spaces (` '). + + + + + + + +.in 5 +.nf + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| RESERVED | Flags | Payload Length | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| | ++ + +| | ++ Cookie + +| | ++ + +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Version String Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Version String ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Key Exchange Grp Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Key Exchange Groups ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| PKCS Alg Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ PKCS Algorithms ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Encryption Alg Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Encryption Algorithms ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Hash Alg Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Hash Algorithms ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Compression Alg Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Compression Algorithms ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +.in 3 + +.ce +Figure 1: Key Exchange Start Payload + + + +.in 6 +o RESERVED (1 byte) - Reserved field. Sender fills this with + zeroes (0). + +o Flags (1 byte) - Indicates flags to be used in the key + exchange. Several flags can be set at once by ORing the + flags together. Following flags are reserved for this field. + + No flags 0x00 + + In this case the field is ignored. + + No Reply 0x01 + + If set the receiver of the payload does not reply to + the packet. + + PFS 0x02 + + Perfect Forward Secrecy (PFS) to be used in the + key exchange protocol. If not set, re-keying + is performed using the old key. When PFS is used, + re-keying and creating new keys for any particular + purpose will cause new key exchange. + + Rest of the flags are reserved for the future and + must not be set. + +o Payload Length (2 bytes) - Length of the entire Key Exchange + Start payload, not including any other field. + +o Cookie (16 bytes) - Cookie that uniforms this payload so + that each of the party cannot determine the payload before + hand. + +o Version String Length (2 bytes) - The length of the Version + String field, not including any other field. + +o Version String (variable length) - Indicates the version of + the sender of this payload. Initiator sets this when sending + the payload and responder sets this when it replies by sending + this payload. See [SILC1] for definition of the version + string format. + +o Key Exchange Grp Length (2 bytes) - The length of the + key exchange group list, not including any other field. + +o Key Exchange Group (variable length) - The list of + key exchange groups. See the section 2.1.2 SILC Key Exchange + Groups for definitions of these groups. + +o PKCS Alg Length (2 bytes) - The length of the PKCS algorithms + list, not including any other field. + +o PKCS Algorithms (variable length) - The list of PKCS + algorithms. + +o Encryption Alg Length (2 bytes) - The length of the encryption + algorithms list, not including any other field. + +o Encryption Algorithms (variable length) - The list of + encryption algorithms. + +o Hash Alg Length (2 bytes) - The length of the Hash algorithms + list, not including any other field. + +o Hash Algorithms (variable length) - The list of Hash algorithms. + +o Compression Alg Length (2 bytes) - The length of the + compression algorithms list, not including any other field. + +o Compression Algorithms (variable length) - The list of + compression algorithms. +.in 3 + + +.ti 0 +2.1.2 Key Exchange 1 Payload + +Key Exchange 1 Payload is used to deliver computed public data from +initiator to responder. This data is used to compute the shared secret, +later by all parties. Key Exchange 1 Payload is only sent after the +SILC_PACKET_KEY_EXCHANGE packet and the Key Exchange Start Payload has +been processed by all the parties. + +This payload sends the initiator's public key to the responder. Responder +may need the public key in which case it should be checked to be trusted +by the responder. + +The payload may only be sent with SILC_PACKET_KEY_EXCHANGE_1 packet. +It must not be sent in any other packet type. Following diagram +represent the Key Exchange 1 Payload. + + + + + + + + + + + + + + + + +.in 5 +.nf + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Public Key Length | Public Key Type | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| | +~ Public Key of the Host (or certificate) ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Public Data Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Public Data (e = g ^ x mod p) ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +.in 3 + +.ce +Figure 2: Key Exchange 1 Payload + + +.in 6 +o Public Key Length (2 bytes) - The length of the Public Key + (or certificate) field, not including any other field. + +o Public Key Type (2 bytes) - The public key (or certificate) + type. This field indicates the type of the public key in + the packet. Following types are defined: + + 1 SILC style public key (mandatory) + 2 SSH2 style public key (optional) + 3 X.509 Version 3 certificate (optional) + 4 OpenPGP certificate (optional) + 5 SPKI certificate (optional) + + The only required type to support is type number 1. See + [SILC1] for the SILC public key specification. See + SSH public key specification in [SSH-TRANS]. See X.509v3 + certificate specification in [PKIX-Part1]. See OpenPGP + certificate specification in [PGP]. See SPKI certificate + specification in [SPKI]. If this field includes zero (0) + or unsupported type number the protocol must be aborted + sending SILC_PACKET_FAILURE message. + +o Public Data Length (2 bytes) - The length of the public + data computed by the responder, not including any other + field. + +o Public Data (variable length) - The public data to be + sent to the responder. See section 2.2 Key Exchange + Procedure for detailed description how this field is + computed. This value is binary encoded. +.in 3 + + +.ti 0 +2.1.3 Key Exchange 2 Payload + +Key Exchange 2 Payload is used to deliver public key, computed public +data and signature from responder to initiator. Initiator uses these +public parts of the key exchange protocol to compute the shared secret. + +The payload may only be sent with SILC_PACKET_KEY_EXCHANGE_2 packet. +It must not be sent in any other packet type. Following diagram +represent the Key Exchange 2 Payload. + + + +.in 5 +.nf + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Public Key Length | Public Key Type | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| | +~ Public Key of the Host (or certificate) ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Public Data Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Public Data (f = g ^ y mod p) ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Signature Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Signature Data ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +.in 3 + +.ce +Figure 3: Key Exchange 2 Payload + + + +.in 6 +o Public Key Length (2 bytes) - The length of the Public Key + (or certificate) field, not including any other field. + +o Public Key Type (2 bytes) - The public key (or certificate) + type. This field indicates the type of the public key in + the packet. See previous sections for defined public key + types. + +o Public Key of the host (variable length) - The public + key of the sender (or its certificate). This is verified + by the receiver of the packet. The type of this field + is indicated by previous Public Key Type field. + +o Public Data Length (2 bytes) - The length of the public + data computed by the responder, not including any other + field. + +o Public Data (variable length) - The public data computed + by the responder. See section 2.2 Key Exchange Procedure + for detailed description how this field is computed. This + value is binary encoded. + +o Signature Length (2 bytes) - The length of the signature, + not including any other field. + +o Signature Data (variable length) - The signature signed + by the responder. The receiver of this signature must + verify it. The verification is done using the public + key received in this same payload. See section 2.2 + Key Exchange Procedure for detailed description how + to produce the signature. + + +.ti 0 +2.2 Key Exchange Procedure + +The key exchange begins by sending SILC_PACKET_KEY_EXCHANGE packet with +Key Exchange Start Payload to select the security properties to be used +in the key exchange and later in the communication. + +After Key Exchange Start Payload has been processed by both of the +parties the protocol proceeds as follows: + + +Setup: p is a large and public safe prime. This is one of the + Diffie Hellman groups. q is order of subgroup (largest + prime factor of p). g is a generator and is defined + along with the Diffie Hellman group. + + 1. Initiator generates a random number x, where 1 < x < q, + and computes e = g ^ x mod p. The result e is then + encoded into Key Exchange 1 Payload and sent + to the responder. + + + 2. Responder generates a random number y, where 1 < y < q, + and computes f = g ^ y mod p. It then computes the + shared secret KEY = e ^ y mod p, and, a hash value + HASH = hash(Key Exchange Start Payload data | Host public + key (or certificate) | e | f | KEY). It then signs + the HASH value with its private key resulting a signature + SIGN. + + It then encodes its public key (or certificate), f and + SIGN into Key Exchange 2 Payload and sends it to the + initiator. + + + 3. Initiator verifies that the public key provided in + the payload is authentic, or if certificates are used + it verifies the certificate. Initiator may accept + the public key without verifying it, however, doing + so may result to insecure key exchange (accepting the + public key without verifying may be desirable for + practical reasons on many environments. For long term + use this is never desirable, in which case certificates + would be the preferred method to use). + + Initiator then computes the shared secret KEY = + f ^ x mod p, and, a hash value HASH in the same way as + responder did in phase 2. It then verifies the + signature SIGN from the payload with the hash value + HASH using the received public key. + + +If any of these phases is to fail SILC_PACKET_FAILURE is sent to +indicate that the key exchange protocol failed. Any other packets must +not be sent or accepted during the key exchange except the +SILC_PACKET_KEY_EXCHANGE_*, SILC_PACKET_DISCONNECT, SILC_PACKET_FAILURE +and/or SILC_PACKET_SUCCESS packets. + +The result of this protocol is a shared secret key material KEY and +a hash value HASH. The key material itself is not fit to be used as +a key, it needs to be processed further to derive the actual keys to be +used. The key material is also used to produce other security parameters +later used in the communication. See section 2.3 Processing the Key +Material for detailed description how to process the key material. + +After the keys are processed the protocol is ended by sending the +SILC_PACKET_SUCCESS packet. Both entities send this packet to +each other. After this both parties will start using the new keys. + + + +.ti 0 +2.3 Processing the Key Material + +Key Exchange protocol produces secret shared key material KEY. This +key material is used to derive the actual keys used in the encryption +of the communication channel. The key material is also used to derive +other security parameters used in the communication. Key Exchange +protocol produces a hash value HASH as well. This is used in the key +deriving process as a session identifier. + +Keys are derived from the key material as follows: + +.in 6 +Sending Initial Vector (IV) = hash(0 | KEY | HASH) +Receiving Initial Vector (IV) = hash(1 | KEY | HASH) +Sending Encryption Key = hash(2 | KEY | HASH) +Receiving Encryption Key = hash(3 | KEY | HASH) +HMAC Key = hash(4 | KEY | HASH) +.in 3 + + +The Initial Vector (IV) is used in the encryption when doing for +example CBC mode. As many bytes as needed are taken from the start of +the hash output for IV. Sending IV is for sending key and receiving IV +is for receiving key. For receiving party, the receiving IV is actually +sender's sending IV, and, the sending IV is actually sender's receiving +IV. Initiator uses IV's as they are (sending IV for sending and +receiving IV for receiving). + +The Encryption Keys are derived as well from the hash(). If the hash() +output is too short for the encryption algorithm more key material is +produced in following manner: + +.in 6 +K1 = hash(2 | KEY | HASH) +K2 = hash(KEY | K1) +K3 = hash(KEY | K1 | K2) ... + +Sending Encryption Key = K1 | K2 | K3 ... + + +K1 = hash(3 | KEY | HASH) +K2 = hash(KEY | K1) +K3 = hash(KEY | K1 | K2) ... + +Receiving Encryption Key = K1 | K2 | K3 ... +.in 3 + + +The key is distributed by hashing the previous hash with the original +key material. The final key is a concatenation of the hash values. +For Receiving Encryption Key the procedure is equivalent. Sending key +is used only for encrypting data to be sent. The receiving key is used +only to decrypt received data. For receiving party, the receive key is +actually sender's sending key, and, the sending key is actually sender's +receiving key. Initiator uses generated keys as they are (sending key +for sending and receiving key for sending). + +The HMAC key is used to create MAC values to packets in the communication +channel. As many bytes as needed are taken from the start of the hash +output. + +These procedures are performed by all parties of the key exchange +protocol. This must be done before the protocol has been ended by +sending the SILC_PACKET_SUCCESS packet. + + +.ti 0 +2.4 SILC Key Exchange Groups + +Following groups may be used in the SILC Key Exchange protocol. The +first group diffie-hellman-group1 is mandatory, other groups maybe +negotiated to be used in the connection with Key Exchange Start Payload +and SILC_PACKET_KEY_EXCHANGE packet. However, the first group must be +proposed in the Key Exchange Start Payload regardless of any other +requested group (however, it doesn't have to be the first on the list). + + +.ti 0 +2.4.1 diffie-hellman-group1 + +The length of this group is 1024 bits. This is mandatory group. +The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }. + +Its decimal value is + +.in 6 +179769313486231590770839156793787453197860296048756011706444 +423684197180216158519368947833795864925541502180565485980503 +646440548199239100050792877003355816639229553136239076508735 +759914822574862575007425302077447712589550957937778424442426 +617334727629299387668709205606050270810842907692932019128194 +467627007 +.in 3 + +Its hexadecimal value is + +.in 6 +FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 +29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD +EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 +E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED +EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381 +FFFFFFFF FFFFFFFF +.in 3 + + +The generator used with this prime is g = 2. The group order q is +(p - 1) / 2. + +This group was taken from the OAKLEY specification. + + +.ti 0 +2.4.2 diffie-hellman-group2 + +The length of this group is 1536 bits. This is optional group. +The prime is 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }. + +Its decimal value is + +.in 6 +241031242692103258855207602219756607485695054850245994265411 +694195810883168261222889009385826134161467322714147790401219 +650364895705058263194273070680500922306273474534107340669624 +601458936165977404102716924945320037872943417032584377865919 +814376319377685986952408894019557734611984354530154704374720 +774996976375008430892633929555996888245787241299381012913029 +459299994792636526405928464720973038494721168143446471443848 +8520940127459844288859336526896320919633919 +.in 3 + +Its hexadecimal value is + +.in 6 +FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 +29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD +EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 +E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED +EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D +C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F +83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D +670C354E 4ABC9804 F1746C08 CA237327 FFFFFFFF FFFFFFFF +.in 3 + +The generator used with this prime is g = 2. The group order q is +(p - 1) / 2. + +This group was taken from the OAKLEY specification. + + +.ti 0 +2.5 Key Exchange Status Types + +This section defines all key exchange protocol status types that may be +returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets to +indicate the status of the protocol. Implementations may map the +status types to human readable error message. All types except the +SILC_SKE_STATUS_OK type must be sent in SILC_PACKET_FAILURE packet. +Following status types are defined: + +.in 6 +0 SILC_SKE_STATUS_OK + + Protocol were exeucted succesfully. + + +1 SILC_SKE_STATUS_ERROR + + Unknown error occured. No specific error type is defined. + + +2 SILC_SKE_STATUS_BAD_PAYLOAD + + Provided KE payload were malformed or included bad fields. + + +3 SILC_SKE_STATUS_UNSUPPORTED_GROUP + + None of the provided groups were supported. + + +4 SILC_SKE_STATUS_UNSUPPORTED_CIPHER + + None of the provided ciphers were supported. + + +5 SILC_SKE_STATUS_UNSUPPORTED_PKCS + + None of the provided public key algorithms were supported. + + +6 SILC_SKE_STATUS_UNSUPPORTED_HASH_FUNCTION + + None of the provided hash functions were supported. + + +7 SILC_SKE_STATUS_UNSUPPORTED_PUBLIC_KEY + + Provided public key type is not supported. + + +8 SILC_SKE_STATUS_INCORRECT_SIGNATURE + + Provided signature was incorrect. +.in 3 + + + + + +.ti 0 +3 SILC Connection Authentication Protocol + +Purpose of Connection Authentication protocol is to authenticate the +connecting party with server. Usually connecting party is client but +server may connect to server as well. Its other purpose is to provide +information for the server about which type of connection this is. +The type defines whether this is client, server or router connection. +Server uses this information to create the ID for the connection. After +the authentication protocol has been successfully completed +SILC_PACKET_NEW_ID must be sent to the connecting party by the server. +See section New ID Payload in [SILC2] for detailed description for this +packet's payload. + +Server must verify the authentication data received and if it is to fail +the authentication must be failed by sending SILC_PACKET_FAILURE packet. +If everything checks out fine the protocol is ended by server by sending +SILC_PACKET_SUCCESS packet. + +The protocol is executed after the SILC Key Exchange protocol. It must +not be executed in any other time. As it is performed after key exchange +protocol all traffic in the connection authentication protocol is +encrypted with the exchanged keys. + +The protocol is started by the connecting party by sending +SILC_PACKET_CONNECTION_AUTH packet with Connection Auth Payload, +described in the next section. This payload must include the +authentication data. Authentication data is set according +authentication method that must be known by both parties. If connecting +party does not know what is the mandatory authentication method it must +request it from the server by sending SILC_PACKET_CONNECTION_AUTH_REQUEST +packet. This packet is not part of this protocol and is described in +section Connection Auth Request Payload in [SILC2]. However, if +connecting party already knows the mandatory authentication method +sending the request is not necessary. + +See [SILC1] and section Connection Auth Request Payload in [SILC2] also +for the list of different authentication methods. Authentication method +may also be NONE, in which case the server does not require +authentication at all. However, in this case the protocol still must be +executed; the authentication data just is empty indicating no +authentication is required. + +If authentication method is passphrase the authentication data is +plaintext passphrase. As the payload is entirely encrypted it is safe +to have plaintext passphrase. 3.2.1 Passphrase Authentication for +more information. + + +If authentication method is public key authentication the authentication +data is signature of the hash value HASH plus Key Exchange Start Payload, +established by the SILC Key Exchange protocol. This signature must then +be verified by the server. See section 3.2.2 Public Key Authentication +for more information. + +The connecting party of this protocol must wait after successful execution +of this protocol for the SILC_PACKET_NEW_ID packet where it will receive +the ID it will be using in the SILC network. Connecting party cannot +start normal SILC session (sending messages or commands) until it has +received its ID. The ID's are always created by the server except +for server to server connection where servers create their own ID's. + + + +.ti 0 +3.1 Connection Auth Payload + +Client sends this payload to authenticate itself to the server. Server +connecting to another server also sends this payload. Server receiving +this payload must verify all the data in it and if something is to fail +the authentication must be failed by sending SILC_PACKET_FAILURE packet. + +The payload may only be sent with SILC_PACKET_CONNECTION_AUTH packet. +It must not be sent in any other packet type. Following diagram +represent the Connection Auth Payload. + + +.in 5 +.nf + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Payload Length | Connection Type | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| | +~ Authentication Data ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +.in 3 + +.ce +Figure 4: Connection Auth Payload + + +.in 6 +o Payload Length (2 bytes) - Length of the entire Connection + Auth Payload. + +o Connection Type (2 bytes) - Indicates the type of the + connection. See section Connection Auth Request Payload + in [SILC2] for the list of connection types. This field must + include valid connection type or the packet must be discarded + and authentication must be failed. + +o Authentication Data (variable length) - The actual + authentication data. Contents of this depends on the + authentication method known by both parties. If no + authentication is required this field does not exist. +.in 3 + + +.ti 0 +3.2 Connection Authentication Types + +SILC supports two authentication types to be used in the connection +authentication protocol; passphrase or public key based authentication. +Following sections defines the authentication methods. See [SILC2] +for defined numerical authentication method types. + + +.ti 0 +3.2.1 Passphrase Authentication + +Passphrase authentication or pre-shared-key base authentication is +simply an authentication where the party that wants to authenticate +itself to the other end sends the passphrase that is required by +the other end, for example server. + +If the passphrase matches with the one in the server's end the +authentication is successful. Otherwise SILC_PACKET_FAILURE must be +sent to the sender and the protocol execution fails. + +This is required authentication method to be supported by all SILC +implementations. + + +.ti 0 +3.2.2 Public Key Authentication + +Public key authentication may be used if passphrase based authentication +is not desired. The public key authentication works by sending a +signature as authentication data to the other end, say, server. The +server must then verify the signature by the public key of the sender, +which the server has received earlier in SKE protocol. + +The signature is computed using the private key of the sender by signing +the HASH value provided by the SKE protocol previously, and the Key +Exchange Start Payload from SKE protocol that was sent to the server. +The server must verify the data, thus it must keep the HASH and the +Key Exchange Start Payload saved during SKE and authentication protocols. + +If the verified signature matches the sent signature, the authentication +were successful and SILC_PACKET_SUCCESS is sent. If it failed the protocol +execution is stopped and SILC_PACKET_FAILURE is sent. + +This is required authentication method to be supported by all SILC +implementations. + + +.ti 0 +3.3 Connection Authentication Status Types + +This section defines all connection authentication status types that +may be returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets +to indicate the status of the protocol. Implementations may map the +status types to human readable error message. All types except the +SILC_AUTH_STATUS_OK type must be sent in SILC_PACKET_FAILURE packet. +Following status types are defined: + +0 SILC_AUTH_OK + + Protocol was executed succesfully. + + +1 SILC_AUTH_FAILED + + Authentication failed. + + +.ti 0 +4 Security Considerations + +Security is central to the design of this protocol, and these security +considerations permeate the specification. + + +.ti 0 +5 References + +[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC), + Protocol Specification", Internet Draft, June 2000. + +[SILC2] Riikonen, P., "SILC Packet Protocol", 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 +6 Author's Address + +.nf +Pekka Riikonen +Kasarmikatu 11 A4 +70110 Kuopio +Finland + +EMail: priikone@poseidon.pspt.fi + +This Internet-Draft expires 13 May 2001 + diff --git a/doc/draft-riikonen-silc-pp-01.nroff b/doc/draft-riikonen-silc-pp-01.nroff new file mode 100644 index 00000000..94ab7596 --- /dev/null +++ b/doc/draft-riikonen-silc-pp-01.nroff @@ -0,0 +1,2470 @@ +.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-01.txt 13 September 2000 +Expires: 13 May 2001 + +.in 3 + +.ce 2 +SILC Packet Protocol + + +.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 + +Following notify types has been defined: + +.in 6 +0 SILC_NOTIFY_TYPE_NONE + + If no specific notify type apply for the notify + message this type may be used. + +1 SILC_NOTIFY_TYPE_INVITE + + Sent when receiver has been invited to a channel. + +2 SILC_NOTIFY_TYPE_JOIN + + Sent when client has joined to a channel. + +3 SILC_NOTIFY_TYPE_LEAVE + + Sent when client has left a channel. + +4 SILC_NOTIFY_TYPE_SIGNOFF + + Sent when client signoffs from SILC network. +.in 3 + +Notify types starting from 16384 are reserved for private notify +message types. + + +.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 diff --git a/doc/draft-riikonen-silc-spec-01.nroff b/doc/draft-riikonen-silc-spec-01.nroff new file mode 100644 index 00000000..d4d38566 --- /dev/null +++ b/doc/draft-riikonen-silc-spec-01.nroff @@ -0,0 +1,3094 @@ +.pl 10.0i +.po 0 +.ll 7.2i +.lt 7.2i +.nr LL 7.2i +.nr LT 7.2i +.ds LF Riikonen +.ds RF FORMFEED[Page %] +.ds CF +.ds LH Internet Draft +.ds RH 13 September 2000 +.ds CH +.na +.hy 0 +.in 0 +.nf +Network Working Group P. Riikonen +Internet-Draft +draft-riikonen-silc-spec-01.txt 13 September 2000 +Expires: 13 May 2001 + +.in 3 + +.ce 3 +Secure Internet Live Conferencing (SILC), +Protocol Specification + + +.ti 0 +Status of this Memo + +This document is an Internet-Draft and is in full conformance with +all provisions of Section 10 of RFC 2026. Internet-Drafts are +working documents of the Internet Engineering Task Force (IETF), its +areas, and its working groups. Note that other groups may also +distribute working documents as Internet-Drafts. + +Internet-Drafts are draft documents valid for a maximum of six months +and may be updated, replaced, or obsoleted by other documents at any +time. It is inappropriate to use Internet-Drafts as reference +material or to cite them other than as "work in progress." + +The list of current Internet-Drafts can be accessed at +http://www.ietf.org/ietf/1id-abstracts.txt + +The list of Internet-Draft Shadow Directories can be accessed at +http://www.ietf.org/shadow.html + +The distribution of this memo is unlimited. + + +.ti 0 +Abstract + +This memo describes a Secure Internet Live Conferencing (SILC) +protocol which provides secure conferencing services over insecure +network channel. SILC is IRC [IRC] like protocol, however, it is +not equivalent to IRC and does not support IRC. Strong cryptographic +methods are used to protect SILC packets inside SILC network. Two +other Internet Drafts relates very closely to this memo; SILC Packet +Protocol [SILC2] and SILC Key Exchange and Authentication Protocols +[SILC3]. + + + + + + + + +.ti 0 +Table of Contents + +.nf +1 Introduction .................................................. 3 +2 SILC Concepts ................................................. 3 + 2.1 SILC Network Topology ..................................... 4 + 2.2 Communication Inside a Cell ............................... 5 + 2.3 Communication in the Network .............................. 6 + 2.4 Channel Communication ..................................... 7 +3 SILC Specification ............................................ 7 + 3.1 Client .................................................... 7 + 3.1.1 Client ID ........................................... 8 + 3.2 Server .................................................... 9 + 3.2.1 Server's Local ID List .............................. 9 + 3.2.2 Server ID ........................................... 10 + 3.2.3 SILC Server Ports ................................... 11 + 3.3 Router .................................................... 11 + 3.3.1 Router's Local ID List .............................. 11 + 3.3.2 Router's Global ID List ............................. 12 + 3.3.3 Router's Server ID .................................. 13 + 3.4 Channels .................................................. 13 + 3.4.1 Channel ID .......................................... 14 + 3.5 Operators ................................................. 14 + 3.6 SILC Commands ............................................. 15 + 3.7 SILC Packets .............................................. 15 + 3.8 Packet Encryption ......................................... 16 + 3.8.1 Determination of the Source and the Destination ..... 16 + 3.8.2 Client To Client .................................... 17 + 3.8.3 Client To Channel ................................... 18 + 3.8.4 Server To Server .................................... 19 + 3.9 Key Exchange And Authentication ........................... 19 + 3.10 Algorithms ............................................... 19 + 3.10.1 Ciphers ............................................ 19 + 3.10.2 Public Key Algorithms .............................. 20 + 3.10.3 MAC Algorithms ..................................... 20 + 3.10.4 Compression Algorithms ............................. 21 + 3.11 SILC Public Key .......................................... 21 + 3.12 SILC Version Detection ................................... 24 +4 SILC Procedures ............................................... 24 + 4.1 Creating Client Connection ................................ 24 + 4.2 Creating Server Connection ................................ 25 + 4.3 Joining to a Channel ...................................... 26 + 4.4 Channel Key Generation .................................... 27 + 4.5 Private Message Sending and Reception ..................... 27 + 4.6 Private Message Key Generation ............................ 28 + 4.7 Channel Message Sending and Reception ..................... 29 + 4.8 Session Key Regeneration .................................. 29 + 4.9 Command Sending and Reception ............................. 29 +5 SILC Commands ................................................. 30 + 5.1 SILC Commands Syntax ...................................... 30 + 5.2 SILC Commands List ........................................ 32 + 5.3 SILC Command Status Types ................................. 53 + 5.3.1 SILC Command Status Payload ......................... 53 + 5.3.2 SILC Command Status List ............................ 54 +6 Security Considerations ....................................... 59 +7 References .................................................... 59 +8 Author's Address .............................................. 60 + + +.ti 0 +List of Figures + +.nf +Figure 1: SILC Network Topology +Figure 2: Communication Inside cell +Figure 3: Communication Between Cells +Figure 4: SILC Public Key +Figure 5: SILC Command Status Payload + + +.ti 0 +1. Introduction + +This document describes a Secure Internet Live Conferencing (SILC) +protocol which provides secure conferencing services over insecure +network channel. SILC is IRC [IRC] like protocol, however, it is +not equivalent to IRC and does not support IRC. + +Strong cryptographic methods are used to protect SILC packets inside +SILC network. Two other Internet Drafts relates very closely to this +memo; SILC Packet Protocol [SILC2] and SILC Key Exchange and +Authentication Protocols [SILC3]. + +The protocol uses extensively packets as conferencing protocol +requires message and command sending. The SILC Packet Protocol is +described in [SILC2] and should be read to fully comprehend this +document and protocol. [SILC2] also describes the packet encryption +and decryption in detail. + +The security of SILC protocol and for any security protocol for that +matter is based on strong and secure key exchange protocol. The SILC +Key Exchange protocol is described in [SILC3] along with connection +authentication protocol and should be read to fully comprehend this +document and protocol. + +The SILC protocol has been developed to work on TCP/IP network +protocol, although it could be made to work on other network protocols +with only minor changes. However, it is recommended that TCP/IP +protocol is used under SILC protocol. Typical implementation would +be made in client-server model. + + +.ti 0 +2. SILC Concepts + +This section describes various SILC protocol concepts that forms the +actual protocol, and in the end, the actual SILC network. The mission +of the protocol is to deliver messages from clients to other clients +through routers and servers in secure manner. The messages may also +be delivered from one client to many clients forming a group, also +known as a channel. + +This section does not focus to security issues, instead basic network +concepts are introduced to make the topology of the SILC network +clear. + + +.ti 0 +2.1 SILC Network Topology + +SILC network is a cellular network as opposed to tree style network +topology. The rationale for this is to have servers that can perform +specific kind of tasks what other servers cannot perform. This leads +to two kinds of servers; normal SILC servers and SILC routers. + +A difference between normal server and router server is that routers +knows everything about everything in the network. They also do the +actual routing of the messages to the correct receiver. Normal servers +knows only about local information and nothing about global information. +This makes the network faster as there are less servers that needs to +keep global information up to date at all time. + +This, on the other hand, leads to cellular like network, where routers +are in the centrum on the cell and servers are connected to the router. + +Following diagram represents SILC network topology. + + + + + + + + + + + + + + + + + +.in 8 +.nf + ---- ---- ---- ---- ---- ---- + | S8 | S5 | S4 | | S7 | S5 | S6 | + ----- ---- ----- ----- ---- ----- +| S7 | S/R1 | S2 | --- | S8 | S/R2 | S4 | + ---- ------ ---- ---- ------ ---- + | S6 | S3 | S1 | | S1 | S3 | S2 | ---- ---- + ---- ---- ---- ---- ---- ---- | S3 | S1 | + Cell 1. \\ Cell 2. | \\____ ----- ----- + | | | S4 | S/R4 | + ---- ---- ---- ---- ---- ---- ---- ------ + | S7 | S4 | S2 | | S1 | S3 | S2 | | S2 | S5 | + ----- ---- ----- ----- ---- ----- ---- ---- + | S6 | S/R3 | S1 | --- | S4 | S/R5 | S5 | Cell 4. + ---- ------ ---- ---- ------ ---- + | S8 | S5 | S3 | | S6 | S7 | S8 | ... etc ... + ---- ---- ---- ---- ---- ---- + Cell 3. Cell 5. +.in 3 + +.ce +Figure 1: SILC Network Topology + + +A cell is formed when a server or servers connect to one router. In +SILC network normal server cannot directly connect to other normal +server. Normal server may only connect to SILC router which then +routes the messages to the other servers in the cell. Router servers +on the other hand may connect to other routers to form the actual SILC +network, as seen in above figure. However, router is also normal SILC +server; clients may connect to it the same way as to normal SILC +servers. Normal server also cannot have active connections to more +than one router. Normal server cannot be connected to two different +cells. Router servers, on the other hand, may have as many router to +router connections as needed. + +There are many issues in this network topology that needs to be careful +about. Issues like the size of the cells, the number of the routers in +the SILC network and the capacity requirements of the routers. These +issues should be discussed in the Internet Community and additional +documents on the issue will be written. + + +.ti 0 +2.2 Communication Inside a Cell + +It is always guaranteed that inside a cell message is delivered to the +recipient with at most two server hops. Client who is connected to +server in the cell and is talking on channel to other client connected +to other server in the same cell, will have its messages delivered from +its local server first to the router of the cell, and from the router +to the other server in the cell. Following diagram represents this +scenario. + + +.in 25 +.nf +1 --- S1 S4 --- 5 + S/R + 2 -- S2 S3 + / | + 4 3 +.in 3 + + +.ce +Figure 2: Communication Inside cell + + +Example: Client 1. connected to Server 1. message sent to + Client 4. connected to Server 2. travels from Server 1. + first to Router which routes the message to Server 2. + which then sends it to the Client 4. All the other + servers in the cell will not see the routed message. + + +If client is connected directly to the router, as router is also normal +SILC server, the messages inside the cell are always delivered only with +one server hop. If clients communicating with each other are connected +to the same server, no router interaction is needed. This is the optimal +situation of message delivery in the SILC network. + + +.ti 0 +2.3 Communication in the Network + +If the message is destined to server that does not belong to local cell +the message is routed to the router server to which the destination +server belongs, if the local router is connected to destination router. +If there is no direct connection to the destination router, the local +router routes the message to its primary route. Following diagram +represents message sending between cells. + + +.in 16 +.nf +1 --- S1 S4 --- 5 S2 --- 1 + S/R - - - - - - - - S/R + 2 -- S2 S3 S1 + / | \\ + 4 3 2 + + Cell 1. Cell 2. +.in 3 + + +.ce +Figure 3: Communication Between Cells + + +Example: Client 5. connected to Server 4. in Cell 1. message sent + to Client 2. connected to Server 1. in Cell 2. travels + from Server 4. to Router which routes the message to + Router in Cell 2, which then routes the message to + Server 1. All the other servers and routers in the + network will not see the routed message. + + +The optimal case of message delivery from client point of view is +when clients are connected directly to the routers and the messages +are delivered from one router to the other router. + + +.ti 0 +2.4 Channel Communication + +Messages may be sent to group of clients as well. Sending messages to +many clients works the same way as sending messages point to point, from +message delivery point of view. Security issues are another matter +which are not discussed in this section. + +Router server handles the message routing to multiple recipients. If +any recipient is not in the same cell as the sender the messages are +routed further. + +Server distributes the channel message to its local clients who are +joined to the channel. Also, router distributes the message to its +local clients on the channel. + + +.ti 0 +3. SILC Specification + +This section describes the SILC protocol. However, [SILC2] and +[SILC3] describes other important protocols that are part of this SILC +specification and must be read. + + +.ti 0 +3.1 Client + +A client is a piece of software connecting to SILC server. SILC client +cannot be SILC server. Purpose of clients is to provide the user +interface of the SILC services for end user. Clients are distinguished +from other clients by unique Client ID. Client ID is a 128 bit ID that +is used in the communication in the SILC network. The client ID is +based on the nickname selected by the user. User uses logical nicknames +in communication which are then mapped to the corresponding Client ID. +Client ID's are low level identifications and must not be seen by the +end user. + +Clients provide other information about the end user as well. Information +such as the nickname of the user, username and the hostname of the end +user and user's real name. See section 3.2 Server for information of +the requirements of keeping this information. + +The nickname selected by the user is not unique in the SILC network. +There can be 2^8 same nicknames for one IP address. As for comparison to +IRC [IRC] where nicknames are unique this is a fundamental difference +between SILC and IRC. This causes the server names to be used along +with the nicknames to identify specific users when sending messages. +This feature of SILC makes IRC style nickname-wars obsolete as no one +owns their nickname; there can always be someone else with the same +nickname. Another difference is that there are no limit of the length +of the nickname in the SILC. + + +.ti 0 +3.1.1 Client ID + +Client ID is used to identify users in the SILC network. The Client ID +is unique to the extent that there can be 2^128 different Client ID's. +Collisions are not expected to happen. The Client ID is defined as +follows. + +.in 6 +128 bit Client ID based on IPv4 addresses: + +32 bit ServerID IP address (bits 1-32) + 8 bit Random number +88 bit Truncated MD5 hash value of the nickname + +o Server ID IP address - Indicates the server where this + client is coming from. The IP address hence equals the + server IP address where to the client has connected. + +o Random number - Random number to further randomize the + Client ID. This makes it possible to have 2^8 same + nicknames from the same server IP address. + +o MD5 hash - MD5 hash value of the nickname is truncated + taking 88 bits from the start of the hash value. This + hash value is used to search the user's Client ID from + the ID lists. + +.in 3 +Collisions could occur when more than 2^8 clients using same nickname +from the same server IP address is connected to the SILC network. +Server must be able to handle this situation by refusing to accept +anymore of that nickname. + +Another possible collision may happen with the truncated hash value of +the nickname. It could be possible to have same truncated hash value for +two different nicknames. However, this is not expected to happen nor +cause any problems if it would occur. Nicknames are usually logical and +it is unlikely to have two distinct logical nicknames produce same +truncated hash value. + + +.ti 0 +3.2 Server + +Servers are the most important parts of the SILC network. They form the +basis of the SILC, providing a point to which clients may connect to. +There are two kinds of servers in SILC; normal servers and router servers. +This section focuses on the normal server and router server is described +in the section 3.3 Router. + +Normal servers may not directly connect to other normal server. Normal +servers may only directly connect to router server. If the message sent +by the client is destined outside the local server it is always sent to +the router server for further routing. Server may only have one active +connection to router on same port. Normal server may not connect to other +cell's router except in situations where its cell's router is unavailable. + +Servers and routers in the SILC network are considered to be trusted. +With out a doubt, servers that are set to work on ports above 1023 are +not considered to be trusted. Also, the service provider acts important +role in the server's trustworthy. + + +.ti 0 +3.2.1 Server's Local ID List + +Normal server keeps various information about the clients and their end +users connected to it. Every normal server must keep list of all locally +connected clients, Client ID's, nicknames, usernames and hostnames and +user's real name. Normal servers only keeps local information and it +does not keep any global information. Hence, normal servers knows only +about their locally connected clients. This makes servers efficient as +they don't have to worry about global clients. Server is also responsible +of creating the Client ID's for their clients. + +Normal server also keeps information about locally created channels and +their Channel ID's. + + + + + + + + +Hence, local list for normal server includes: + +.in 6 +server list - Router connection + o Server name + o Server IP address + o Server ID + o Sending key + o Receiving key + o Public key + +client list - All clients in server + o Nickname + o Username@host + o Real name + o Client ID + o Sending key + o Receiving key + +channel list - All channels in server + o Channel name + o Channel ID + o Client ID's on channel + o Client ID modes on channel + o Channel key +.in 3 + + + +.ti 0 +3.2.2 Server ID + +Servers are distinguished from other servers by unique 64 bit Server ID. +The Server ID is used in the SILC to route messages to correct servers. +Server ID's also provide information for Client ID's, see section 3.1.1 +Client ID. Server ID is defined as follows. + +.in 6 +64 bit Server ID based on IPv4 addresses: + +32 bit IP address of the server +16 bit Port +16 bit Random number + +o IP address of the server - This is the real IP address of + the server. + +o Port - This is the port the server is binded to. + +o Random number - This is used to further randomize the Server ID. + +.in 3 +Collisions are not expected to happen in any conditions. The Server ID +is always created by the server itself and server is resposible of +distributing it to the router. + + +.ti 0 +3.2.3 SILC Server Ports + +Following ports has been assigned by IANA for the SILC protocol: + +.in 10 +silc 706/tcp SILC +silc 706/udp SILC +.in 3 + +If there are needs to create new SILC networks in the future the port +numbers must be officially assigned by the IANA. + +Server on network above privileged ports (>1023) should not be trusted +as they could have been set up by untrusted party. + + +.ti 0 +3.3 Router + +Router server in SILC network is responsible for keeping the cell together +and routing messages to other servers and to other routers. Router server +is also a normal server thus clients may connect to it as it would be +just normal SILC server. + +However, router servers has a lot of important tasks that normal servers +do not have. Router server knows everything about everything in the SILC. +They know all clients currently on SILC, all servers and routers and all +channels in SILC. Routers are the only servers in SILC that care about +global information and keeping them up to date at all time. And, this +is what they must do. + + +.ti 0 +3.3.1 Router's Local ID List + +Router server as well must keep local list of connected clients and +locally created channels. However, this list is extended to include all +the informations of the entire cell, not just the server itself as for +normal servers. + +However, on router this list is a lot smaller since routers do not keep +information about user's nickname, username and hostname and real name +since these are not needed by the router. Router keeps only information +that it needs. + + + + + +Hence, local list for router includes: + +.in 6 +server list - All servers in the cell + o Server name + o Server ID + o Router's Server ID + o Sending key + o Receiving key + +client list - All clients in the cell + o Client ID + +channel list - All channels in the cell + o Channel ID + o Client ID's on channel + o Client ID modes on channel + o Channel key +.in 3 + + +Note that locally connected clients and other information include all the +same information as defined in section section 3.2.1 Server's Local ID +List. + + +.ti 0 +3.3.2 Router's Global ID List + +Router server must also keep global list. Normal servers do not have +global list as they know only about local information. Global list +includes all the clients on SILC, their Client ID's, all created channels +and their Channel ID's and all servers and routers on SILC and their +Server ID's. That is said, global list is for global information and the +list must not include the local information already on the router's local +list. + +Note that the global list does not include information like nicknames, +usernames and hostnames or user's real names. Router does not keep +these informations as they are not needed by the router. This +information is available from the client's server which maybe queried +when needed. + +Hence, global list includes: + +.in 6 +server list - All servers in SILC + o Server name + o Server ID + o Router's Server ID + + +client list - All clients in SILC + o Client ID + +channel list - All channels in SILC + o Channel ID + o Client ID's on channel + o Client ID modes on channel +.in 3 + + +.ti 0 +3.3.3 Router's Server ID + +Router's Server ID's are equivalent to normal Server ID's. As routers +are normal servers as well same types of ID's applies for routers as well. +Thus, see section 3.2.2 Server ID. Server ID's for routers are always +created by the remote router where the router is connected to. + + +.ti 0 +3.4 Channels + +A channel is a named group of one or more clients which will all receive +messages addressed to that channel. The channel is created when first +client requests JOIN command to the channel, and the channel ceases to +exist when the last client leaves it. When channel exists, any client +can reference it using the name of the channel. + +Channel names are unique although the real uniqueness comes from 64 bit +Channel ID that unifies each channel. However, channel names are still +unique and no two global channels with same name may exist. Channel name +is a string which begins with `#' character. There is no limit on the +length of the channel name. Channel names may not contain any spaces +(` '), any non-printable ASCII characters, commas (`,') and wildcard +characters. + +Channels can have operators that can administrate the channel and +operate all of its modes. Following operators on channel exist on SILC +network. + +.in 6 +o Channel founder - When channel is created the joining client becomes + channel founder. Channel founder is channel operator with some more + privileges. Basically, channel founder can fully operate the channel + and all of its modes. The privileges are limited only to the particular + channel. There can be only one channel founder per channel. Channel + founder supersedes channel operator's privileges. + + Channel founder privileges cannot be removed by any other operator on + channel. When channel founder leaves the channel there is no channel + founder on the channel. Channel founder also cannot be removed by + force from the channel. + +o Channel operator - When client joins to channel that has not existed + previously it will become automatically channel operator (and channel + founder discussed above). Channel operator is able administrate the + channel, set some modes on channel, remove a badly behaving client from + the channel and promote other clients to become channel operator. + The privileges are limited only to the particular channel. + + Normal channel user may be promoted (opped) to channel operator + gaining channel operator privileges. Channel founder or other channel + operator may also demote (deop) channel operator to normal channel + user. +.in 3 + + +.ti 0 +3.4.1 Channel ID + +Channels are distinguished from other channels by unique Channel ID. +The Channel ID is a 64 bit ID and collisions are not expected to happen +in any conditions. Channel names are just for logical use of channels. +The Channel ID is created by the server where the channel is created. +The Channel ID is defined as follows. + +.in 6 +64 bit Channel ID based on IPv4 addresses: + +32 bit Router's Server ID IP address (bits 1-32) +16 bit Router's Server ID port (bits 33-48) +16 bit Random number + +o Router's Server ID IP address - Indicates the IP address of + the router of the cell where this channel is created. This is + taken from the router's Server ID. This way SILC router knows + where this channel resides in the SILC network. + +o Router's Server ID port - Indicates the port of the channel on + the server. This is taken from the router's Server ID. + +o Random number - To further randomize the Channel ID. This makes + sure that there are no collisions. This also means that + in a cell there can be 2^16 channels. +.in 3 + + +.ti 0 +3.5 Operators + +Operators are normal users with extra privileges to their server or +router. Usually these people are SILC server and router administrators +that take care of their own server and clients on them. The purpose of +operators is to administrate the SILC server or router. However, even +an operator with highest privileges is not able to enter invite-only +channel, to gain access to the contents of a encrypted and authenticated +packets traveling in the SILC network or to gain channel operator +privileges on public channels without being promoted. They have the +same privileges as everyone else except they are able to administrate +their server or router. + + +.ti 0 +3.6 SILC Commands + +Commands are very important part on SILC network especially for client +which uses commands to operate on the SILC network. Commands are used +to set nickname, join to channel, change modes and many other things. + +Client usually sends the commands and server replies by sending a reply +packet to the command. Server may also send commands usually to serve +the original client's request. However, server may not send command +to client and there are some commands that server must not send. Server +is also able to send the forwarded command packets. For example, +SILC_COMMAND_JOIN is always forwarded packet. See [SILC2] for more +about packet forwarding. + +Note that the command reply is usually sent only after client has sent +the command request but server is allowed to send command reply packet +to client even if client has not requested the command. Client may, +however, choose not to accept the command reply, but there are some +command replies that the client should accept. Example of a such +command reply is reply to SILC_COMMAND_CMODE command that the server +uses to distribute the channel mode on all clients on the channel +when the mode has changed. + +It is expected that some of the commands may be miss-used by clients +resulting various problems on the server side. Every implementation +should assure that commands may not be executed more than once, say, +in two (2) seconds. This should be sufficient to prevent the miss-use +of commands. + +SILC commands are described in section 5 SILC Commands. + + +.ti 0 +3.7 SILC Packets + +Packets are naturally the most important part of the protocol and the +packets are what actually makes the protocol. Packets in SILC network +are always encrypted using, usually, the shared secret session key +or some other key, for example, channel key, when encrypting channel +messages. The SILC Packet Protocol is a wide protocol and is described +in [SILC2]. This document does not define or describe details of +SILC packets. + + + + +.ti 0 +3.8 Packet Encryption + +All packets passed in SILC network must be encrypted. This section +defines how packets must be encrypted in the SILC network. The detailed +description of the actual encryption process of the packets are +described in [SILC2]. + +Client and its server shares secret symmetric session key which is +established by the SILC Key Exchange Protocol, described in [SILC3]. +Every packet sent from client to server, with exception of packets for +channels, are encrypted with this session key. + +Channels has their own key that are shared by every client on the channel. +However, the channel keys are cell specific thus one cell does not know +the channel key of the other cell, even if that key is for same channel. +Channel key is also known by the routers and all servers that has clients +on the channel. However, channels may have channel private keys that +are entirely local setting for client. All clients on the channel must +know the channel private key before hand to be able to talk on the +channel. In this case, no server or router knows the key for channel. + +Server shares secret symmetric session key with router which is +established by the SILC Key Exchange Protocol. Every packet passed from +server to router, with exception of packets for channels, are encrypted +with the shared session key. Same way, router server shares secret +symmetric key with its primary route. However, every packet passed +from router to other router, including packets for channels, are +encrypted with the shared session key. Every router connection has +their own session keys. + + +.ti 0 +3.8.1 Determination of the Source and the Destination + +The source and the destination of the packet needs to be determined +to be able to route the packets to correct receiver. This information +is available in the SILC Packet Header which is included in all packets +sent in SILC network. The SILC Packet Header is described in [SILC2]. + +The header is always encrypted with the session key who is next receiver +of the packet along the route. The receiver of the packet, for example +a router along the route, is able to determine the sender and the +destination of the packet by decrypting the SILC Packet Header and +checking the ID's attached to the header. The ID's in the header will +tell to where the packet needs to be sent and where it is coming from. + +The header in the packet does not change during the routing of the +packet. The original sender, for example client, assembles the packet +and the packet header and server or router between the sender and the +receiver must not change the packet header. + +Note that the packet and the packet header may be encrypted with +different keys. For example, packets to channels are encrypted with +the channel key, however, the header is encrypted with the session key +as described above. However, the header and the packet may be encrypted +with same key. This is case, for example, with command packets. + + +.ti 0 +3.8.2 Client To Client + +Process of message delivery and encryption from client to another +client is as follows. + +Example: Private message from client to another client on different + servers. Clients do not share private message delivery + keys; normal session keys are used. + +o Client 1. sends encrypted packet to its server. The packet is + encrypted with the session key shared between client and its + server. + +o Server determines the destination of the packet and decrypts + the packet. Server encrypts the packet with session key shared + between the server and its router, and sends the packet to the + router. + +o Router determines the destination of the packet and decrypts + the packet. Router encrypts the packet with session key + shared between the router and the destination server, and sends + the packet to the server. + +o Server determines the client to which the packet is destined + to and decrypts the packet. Server encrypts the packet with + session key shared between the server and the destination client, + and sends the packet to the client. + +o Client 2. decrypts the packet. + + +Example: Private message from client to another client on different + servers. Clients has established secret shared private + message delivery key with each other and that is used in + the message encryption. + +o Client 1. sends encrypted packet to its server. The packet is + encrypted with the private message delivery key shared between + clients. + +o Server determines the destination of the packet and sends the + packet to the router. + +o Router determines the destination of the packet and sends the + packet to the server. + +o Server determines the client to which the packet is destined + to and sends the packet to the client. + +o Client 2. decrypts the packet with the secret shared key. + + +If clients share secret key with each other the private message +delivery is much simpler since servers and routers between the +clients do not need to decrypt and re-encrypt the packet. + +The process for clients on same server is much simpler as there are +no need to send the packet to the router. The process for clients +on different cells is same as above except that the packet is routed +outside the cell. The router of the destination cell routes the +packet to the destination same way as described above. + + +.ti 0 +3.8.3 Client To Channel + +Process of message delivery from client on channel to all the clients +on the channel. + +Example: Channel of four users; two on same server, other two on + different cells. Client sends message to the channel. + +o Client 1. encrypts the packet with channel key and sends the + packet to its server. + +o Server determines local clients on the channel and sends the + packet to the Client on the same server. Server then sends + the packet to its router for further routing. + +o Router determines local clients on the channel, if found + sends packet to the local clients. Router determines global + clients on the channel and sends the packet to its primary + router or fastest route. + +o (Other router(s) do the same thing and sends the packet to + the server(s)) + +o Server determines local clients on the channel and sends the + packet to the client. + +o All clients receiving the packet decrypts the packet. + + +.ti 0 +3.8.4 Server To Server + +Server to server packet delivery and encryption is described in above +examples. Router to router packet delivery is analogous to server to +server. However, some packets, such as channel packets, are processed +differently. These cases are described later in this document and +more in detail in [SILC2]. + + +.ti 0 +3.9 Key Exchange And Authentication + +Key exchange is done always when for example client connects to server +but also when server and router and router and router connects to each +other. The purpose of key exchange protocol is to provide secure key +material to be used in the communication. The key material is used to +derive various security parameters used to secure SILC packets. The +SILC Key Exchange protocol is described in detail in [SILC3]. + +Authentication is done after key exchange protocol has been successfully +completed. The purpose of authentication is to authenticate for example +client connecting to the server. However, Usually clients are accepted +to connect to server without explicit authentication. Servers are +required use authentication protocol when connecting. The authentication +may be based on passphrase (pre-shared-secret) or public key. The +connection authentication protocol is described in detail in [SILC3]. + + +.ti 0 +3.10 Algorithms + +This section defines all the allowed algorithms that can be used in +the SILC protocol. This includes mandatory cipher, mandatory public +key algorithm and MAC algorithms. + + +.ti 0 +3.10.1 Ciphers + +Cipher is the encryption algorithm that is used to protect the data +in the SILC packets. See [SILC2] of the actual encryption process and +definition of how it must be done. SILC has a mandatory algorithm that +must be supported in order to be compliant with this protocol. + + + + + + +Following ciphers are defined in SILC protocol: + +.in 6 +blowfish-cbc Blowfish in CBC mode (mandatory) +twofish-cbc Twofish in CBC mode (optional) +rc6-cbc RC6 in CBC mode (optional) +rc5-cbc RC5 in CBC mode (optional) +mars-cbc Mars in CBC mode (optional) +none No encryption (optional) +.in 3 + + +All algorithms must use minimum of 128 bit key, by default. Several +algorithms, however, supports longer keys and it is recommended to use +longer keys if they are available. + +Algorithm none does not perform any encryption process at all and +thus is not recommended to be used. It is recommended that no client +or server implementation would accept none algorithms except in special +debugging mode. + +Additional ciphers may be defined to be used in SILC by using the +same name format as above. + + +.ti 0 +3.10.2 Public Key Algorithms + +Public keys are used in SILC to authenticate entities in SILC network +and to perform other tasks related to public key cryptography. The +public keys are also used in the SILC Key Exchange protocol [SILC3]. + +Following public key algorithms are defined in SILC protocol: + +.in 6 +rsa RSA (mandatory) +dss DSS (optional) +.in 3 + +Both of the algorithms are described in [Scheneir] and [Menezes]. + +Additional public key algorithms may be defined to be used in SILC. + + +.ti 0 +3.10.3 MAC Algorithms + +Data integrity is protected by computing a message authentication code +(MAC) of the packet data. See [SILC2] for details how to compute the +MAC. + + + + + +Following MAC algorithms are defined in SILC protocol: + +.in 6 +hmac-sha1 HMAC-SHA1, length = 20 (mandatory) +hmac-md5 HMAC-MD5, length = 16 (optional) +none No MAC (optional) +.in 3 + +The none MAC is not recommended to be used as the packet is not +authenticated when MAC is not computed. It is recommended that no +client or server would accept none MAC except in special debugging +mode. + +The HMAC algorithm is described in [HMAC] and hash algorithms that +are used as part of the HMACs are described in [Scheneir] and in +[Menezes] + +Additional MAC algorithms may be defined to be used in SILC. + + +.ti 0 +3.10.4 Compression Algorithms + +SILC protocol supports compression that may be applied to unencrypted +data. It is recommended to use compression on slow links as it may +significantly speed up the data transmission. By default, SILC does not +use compression which is the mode that must be supported by all SILC +implementations. + +Following compression algorithms are defined: + +.in 6 +none No compression (mandatory) +zlib GBU ZLIB (LZ77) compression (optional) +.in 3 + +Additional compression algorithms may be defined to be used in SILC. + + +.ti 0 +3.11 SILC Public Key + +This section defines the type and format of the SILC public key. All +implementations must support this public key type. See [SILC3] for +other optional public key and certificate types allowed in SILC +protocol. Public keys in SILC may be used to authenticate entities +and to perform other tasks related to public key cryptography. + +The format of the SILC Public Key is as follows: + + + + + + + +.in 5 +.nf + 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Public Key Length | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Algorithm Name Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Algorithm Name ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Identifier Length | | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +| | +~ Identifier ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| | +~ Public Data ~ +| | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +.in 3 + +.ce +Figure 4: SILC Public Key + + +.in 6 +o Public Key Length (4 bytes) - Indicates the full length + of the public key, not including this field. + +o Algorithm Name Length (2 bytes) - Indicates the length + of the Algorithm Length field, not including this field. + +o Algorithm name (variable length) - Indicates the name + of the public key algorithm that the key is. See the + section 3.10.2 Public Key Algorithms for defined names. + +o Identifier Length (2 bytes) - Indicates the length of + the Identifier field, not including this field. + +o Identifier (variable length) - Indicates the identifier + of the public key. This data can be used to identify + the owner of the key. The identifier is of following + format: + + UN User name + HN Host name or IP address + RN Real name + E EMail address + O Organization + C Country + + + Examples of an identifier: + + `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi' + + `UN=sam, HN=dummy.fi, RN=Sammy Sam, O=Company XYZ, C=Finland' + + At least user name (UN) and host name (HN) must be provided as + identifier. The fields are separated by commas (`,'). If + comma is in the identifier string it must be written as `\\,', + for example, `O=Company XYZ\\, Inc.'. + +o Public Data (variable length) - Includes the actual + public data of the public key. + + The format of this field for RSA algorithm is + as follows: + + 4 bytes Length of e + variable length e + 4 bytes Length of n + variable length n + + + The format of this field for DSS algorithm is + as follows: + + 4 bytes Length of p + variable length p + 4 bytes Length of q + variable length q + 4 bytes Length of g + variable length g + 4 bytes Length of y + variable length y + + The variable length fields are multiple precession + integers encoded as strings in both examples. + + Other algorithms must define their own type of this + field if they are used. +.in 3 + +All fields in the public key are in MSB (most significant byte first) +order. + + +.ti 0 +3.12 SILC Version Detection + +The version detection of both client and server is performed at the +connection phase while executing the SILC Key Exchange protocol. The +version identifier is exchanged between intiator and responder. The +version identifier is of following format: + +.in 6 +SILC-- +.in 3 + +The version strings are of following format: + +.in 6 +protocol version = . +software version = [.[.]] +.in 3 + +Protocol version may provide both major and minor version. Currently +implementations must set the protocol version and accept the protocol +version as SILC-1.0-. + +Software version may provide major, minor and build version. The +software version may be freely set and accepted. + +Thus, the version string could be, for example: + +.in 6 +SILC-1.0-1.2 +.in 3 + + +.ti 0 +4 SILC Procedures + +This section describes various SILC procedures such as how the +connections are created and registered, how channels are created and +so on. The section describes the procedures only generally as details +are described in [SILC2] and [SILC3]. + + +.ti 0 +4.1 Creating Client Connection + +This section descibres the procedure when client connects to SILC server. +When client connects to server the server must perform IP address lookup +and reverse IP address lookup to assure that the origin host really is +who it claims to be. Client, host, connecting to server must have +both valid IP address and fully qualified domain name (FQDN). + +After that client and server performs SILC Key Exchange protocol which +will provide the key material used later in the communication. The +key exchange protocol must be completed successfully before the connection +registration may continue. The SILC Key Exchange protocol is described +in [SILC3]. + +Typical server implementation would keep a list of connections that it +allows to connect to the server. The implementation would check, for +example, the connecting client's IP address from the connection list +before the SILC Key Exchange protocol has been started. Reason for +this is that if the host is not allowed to connect to the server there +is no reason to perform a key exchange protocol. + +After successful key exchange protocol the client and server performs +connection authentication protocol. The purpose of the protocol is to +authenticate the client connecting to the server. Flexible +implementation could also accept the client to connect to the server +without explicit authentication. However, if authentication is +desired for a specific client it may be based on passphrase or +public key authentication. If authentication fails the connection +must be terminated. The connection authentication protocol is described +in [SILC3]. + +After successful key exchange and authentication protocol the client +registers itself by sending SILC_PACKET_NEW_CLIENT packet to the +server. This packet includes various information about the client +that the server uses to create the client. Server creates the client +and sends SILC_PACKET_NEW_ID to the client which includes the created +Client ID that the client must start using after that. After that +all SILC packets from the client must have the Client ID as the +Source ID in the SILC Packet Header, described in [SILC2]. + +Client must also get the server's Server ID that is to be used as +Destination ID in the SILC Packet Header when communicating with +the server (for example when sending commands to the server). The +ID may be resolved in two ways. Client can take the ID from an +previously received packet from server that must include the ID, +or to send SILC_COMMAND_INFO command and receive the Server ID as +command reply. + +Server may choose not to use the information received in the +SILC_PACKET_NEW_CLIENT packet. For example, if public key or +certificate were used in the authentication, server may use those +informations rather than what it received from client. This is suitable +way to get the true information about client if it is available. + +The nickname of client is initially set to the username sent in the +SILC_PACKET_NEW_CLIENT packet. User should set the nickname to more +suitable by sending SILC_COMMAND_NICK command. However, this is not +required as part of registration process. + +Server must also distribute the information about newly registered +client to its router (or if the server is router, to all routers in +the SILC network). More information about this in [SILC2]. + + +.ti 0 +4.2 Creating Server Connection + +This section descibres the procedure when server connects to its +router (or when router connects to other router, the cases are +equivalent). The procedure is very much alike when client connects +to the server thus it is not repeated here. + +One difference is that server must perform connection authentication +protocol with proper authentication. Proper authentication is based +on passphrase or public key authentication. + +After server and router has successfully performed the key exchange +and connection authentication protocol, the server register itself +to the router by sending SILC_PACKET_NEW_SERVER packet. This packet +includes the server's Server ID that it has created by itself and +other relevant information about the server. + +After router has received the SILC_PACKET_NEW_SERVER packet it +distributes the information about newly registered server to all routers +in the SILC network. More information about this in [SILC2]. + +As client needed to resolve the destination ID this must be done by the +server that connected to the router, as well. The way to resolve it is +to get the ID from previously received packet. Server must also start +using its own Server ID as Source ID in SILC Packet Header and the +router's Server ID as Destination when communicating with the router. + +If the server has already connected clients and locally created +channels the server must distribute these informations to the router. +The distribution is done by sending packet SILC_PACKET_NEW_CHANNEL. +See [SILC2] for more information on this. + + +.ti 0 +4.3 Joining to a Channel + +This section describes the procedure when client joins to a channel. +Client may join to channel by sending command SILC_COMMAND_JOIN to the +server. If the receiver receiving join command is normal server the +server must check its local list whether this channel already exists +locally. This would indicate that some client connected to the server +has already joined to the channel. If this is case the client is +joined to the client, new channel key is created and information about +newly joined channel is sent to the router. The new channel key is +also distributed to the router and to all clients on the channel. + +If the channel does not exist in the local list the command must be +fowarded to the router which will then perform the actual joining +procedure. When server receives the reply to the command from the +router it must be distributed to the client who sent the command +originally. Server will also receive the channel key from the server +that it must distribute to the client who originally requested the +join command. The server must also save the channel key. + +If the receiver of the join command is router it must first check its +local list whether anyone in the cell has already joined to the channel. +If this is the case the client is joined to the channel and reply is +sent to the client. If the command was sent by server the command reply +is sent to the server who sent it. Then the router must also create +new channel key and distribute it to all clients on the channel and +all servers that has clients on the channel. + +If the channel does not exist on the router's local list it must +check the global list whether the channel exists at all. If it does +the client is joined to the channel as described previously. If +the channel does not exist the channel is created and the client +is joined to the channel. The channel key is also created and +distributed as previously described. The client joining to the created +channel is made automatically channel founder and both channel founder +and channel operator privileges is set for the client. + +When the router joins the client to the channel it must send +information about newly joined client to all routers in the SILC +network. Also, if the channel was created in the process, information +about newly created channel must also be distributed to all routers. +The distribution of newly created channel is done by sending packet +SILC_PACKET_NEW_CHANNEL. + +It is important to note that new channel key is created always when +new client joins to channel, whether the channel has existed previously +or not. This way the new client on the channel is not able to decrypt +any of the old traffic on the channel. + +Client who receives the reply to the join command must start using +the received Channel ID in the channel message communication thereafter. +However, client must not start communicating on the channel before +it has received the packet SILC_PACKET_CHANNEL_KEY. + +If client wants to know the other clients currently on the channel +the client must send SILC_COMMAND_NAMES command to receive a list of +channel users. Server implementation, however, may send command reply +packet to SILC_COMMAND_NAMES command after client has joined to the +channel even if the client has not sent the command. + + +.ti 0 +4.4 Channel Key Generation + +Channel keys are created by router who creates the channel by taking +enough randomness from cryptographically strong random number generator. +The key is generated always when channel is created, when new client +joins a channel and after the key has expired. Key could expire for +example in an hour. + +The key must also be re-generated whenever some client leaves a channel. +In this case the key is created from scratch by taking enough randomness +from the random number generator. After that the key is distributed to +all clients on the channel. However, channel keys are cell specific thus +the key is created only on the cell where the client, who leaved the +channel, exists. While the server or router is creating the new channel +key, no other client may join to the channel. Messages that are sent +while creating the new key are still processed with the old key. After +server has sent the SILC_PACKET_CHANNEL_KEY packet must client start +using the new key. If server creates the new key the server must also +send the new key to its router. See [SILC2] on more information about +how channel messages must be encrypted and decrypted when router is +processing them. + + +.ti 0 +4.5 Private Message Sending and Reception + +Private messages are sent point to point. Client explicitly destines +a private message to specific client that is delivered to only to that +client. No other client may receive the private message. The receiver +of the private message is destined in the SILC Packet Header as any +other packet as well. + +If the sender of a private message does not know the receiver's Client +ID, it must resolve it from server. There are two ways to resolve the +client ID from server; it is recommended that client ipmlementations +send SILC_COMMAND_IDENTIFY command to receive the Client ID. Client +may also send SILC_COMMAND_WHOIS command to receive the Client ID. +If the sender has received earlier a private message from the receiver +it should have cached the Client ID from the SILC Packet Header. + +Receiver of a private message should not explicitly trust the nickname +that it receives in the Private Message Payload, described in [SILC2]. +Implementations could resolve the nickname from server, as described +previously, and compare the received Client ID and the SILC Packet +Header's Client ID. The nickname in the payload is merely provided +to be displayed for end user. + +See [SILC2] for describtion of private message encryption and decryption +process. + + +.ti 0 +4.6 Private Message Key Generation + +Private message may be protected by key generated by client. The key +may be generated and sent to the other client by sending packet +SILC_PACKET_PRIVATE_MESSAGE_KEY which travels through the network +and is secured by session keys. After that the private message key +is used in the private message communication between those clients. +See more information about how this works technically in [SILC2]. + +Other choice is to entirely use keys that are not sent through +the SILC network at all. This significantly adds security. This key +would be pre-shared-key that is known by both of the clients. Both +agree about using the key and starts sending packets that indicate +that the private message is secured using private message key. This +is the technical aspect mentioned previously that is described +in [SILC2]. + +If the private message keys are not set to be used, which is the +case by default in SILC, the private messages are secured by using +normal session keys established by SILC Key Exchange protocol. + + + + +.ti 0 +4.7 Channel Message Sending and Reception + +Channel messages are delivered to group of users. The group forms a +channel and all clients on the channel receives messages sent to the +channel. + +Channel messages are destined to channel by specifying the Channel ID +as Destination ID in the SILC Packet Header. The server must then +distribute the message to all clients on the channel by sending the +channel message destined explicitly to a client on the channel. + +See [SILC2] for describtion of channel message encryption and decryption +process. + + +.ti 0 +4.8 Session Key Regeneration + +Session keys should be regenerated peridiocally, say, once in an hour. +The re-key process is started by sending SILC_PACKET_REKEY packet to +other end, to indicate that re-key must be performed. + +If perfect forward secrecy (PFS) flag was selected in the SILC Key +Exchange protocol [SILC3] the re-key must cause new key exchange with +SKE protocol. In this case the protocol is secured with the old key +and the protocol results to new key material. See [SILC3] for more +information. After the SILC_PACKET_REKEY packet is sent the sender +will perform the SKE protocol. + +If PFS flag was not set, which is the default case, then re-key is done +without executing SKE protocol. In this case, the new key is created by +hashing the old key with hash function selected earlier in the SKE +protocol. If the digest length of the hash function is too short for the +key, then the key is distributed as described in section Processing the +Key Material in [SILC3]. After both parties has regenerated the session +key, both send SILC_PACKET_REKEY_DONE packet to each other. These packets +are still secured with the old key. After these packets, following +packets must be protected with the new key. + + +.ti 0 +4.9 Command Sending and Reception + +Client usually sends the commands in the SILC network. In this case +the client simply sends the command packet to server and the server +processes it and replies with command reply packet. + +However, if the server is not able to process the command, it is usually +sent to the server's router. This is case for example with commands such +as, SILC_COMMAND_JOIN and SILC_COMMAND_WHOIS commands. However, there +are other commands as well. For example, if client sends the WHOIS +command requesting specific information about some client the server must +send the WHOIS command to router so that all clients in SILC network +are searched. The router, on the other hand, sends the WHOIS command +to further to receive the exact information about the requested client. +The WHOIS command travels all the way to the server who owns the client +and it replies with command reply packet. Finally, the server who +sent the command receives the command reply and it must be able to +determine which client sent the original command. The server then +sends command reply to the client. Implementations should have some +kind of cache to handle, for example, WHOIS information. Servers +and routers along the route could all cache the information for faster +referencing in the future. + +The commands sent by server may be sent hop by hop until someone is able +to process the command. However, it is preferred to destine the command +as precisely as it is possible. In this case, other routers en route +must route the command packet by checking the true sender and true +destination of the packet. However, servers and routers must not route +command reply packets to clients coming from other server. Client +must not accept command reply packet originated from anyone else but +from its own server. + + +.ti 0 +5 SILC Commands + +.ti 0 +5.1 SILC Commands Syntax + +This section briefly describes the syntax of the command notions +in this document. Every field in command is separated from each +other by whitespaces (` ') indicating that each field is independent +argument and each argument must have own Command Argument Payload. +The number of maximum arguments are defined with each command +separately. The Command Argument Payload is described in [SILC2]. + +Every command defines specific number for each argument. Currently, +they are defined in ascending order; first argument has number one +(1), second has number two (2) and so on. This number is set into the +Argument Type field in the Command Argument Payload. This makes it +possible to send the arguments in free order as the number must be +used to identify the type of the argument. This makes is it also +possible to have multiple optional arguments in commands and in +command replies. The number of argument is marked in parentheses +before the actual argument. + + + + + +.in 6 +Example: Arguments: (1) (2) +.in 3 + + +Every command replies with Status Payload. This payload tells the +sender of the command whether the command was completed succefully or +whether there was an error. If error occured the payload includes the +error type. In the next section the Status Payload is not described +as it is common to all commands and has been described here. Commands +may reply with other arguments as well. These arguments are command +specific and are described in the next section. + +Example command: +.in 6 + +EXAMPLE_COMMAND + +.in 8 +Max Arguments: 3 + Arguments: (1) [@] (2) + (3) [] + +The command has maximum of 3 arguments. However, only first +and second arguments are mandatory. + +First argument is mandatory but may have optional + format as well. Second argument is mandatory + argument. Third argument is optional argument. + +The numbers in parentheses are the argument specific numbers +that specify the type of the argument in Command Argument Payload. +The receiver always knows that, say, argument number two (2) is + argument, regardles of the ordering of the arguments in +the Command Payload. + +Reply messages to the command: + +Max Arguments: 4 + Arguments: (1) (2) [] + (3) (4) [] + +This command may reply with maximum of 4 arguments. However, +only the first and third arguments are mandatory. The numbers +in the parentheses have the same meaning as in the upper +command sending specification. + +Every command reply with , it is mandatory +argument for all command replies and for this reason it is not +described in the command reply descriptions. + + + +Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_TOO_MANY_TARGETS + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_NO_SUCH_NICK + +Every command reply also defines set of status message that it +may return inside the . All status messages +are defined in the section 5.3 SILC Command Status Types. +.in 3 + + +.ti 0 +5.2 SILC Commands List + +This section lists all SILC commands, however, it is expected that a +implementation and especially client implementation has many more +commands that has only local affect. These commands are official +SILC commands that has both client and server sides and cannot be +characterized as local commands. + +List of all defined commands in SILC follows. + +.in 0 + 0 SILC_COMMAND_NONE + + None. This is reserved command and must not be sent. + + + 1 SILC_COMMAND_WHOIS + + Max Arguments: 3 + Arguments: (1) [@] (2) [] + (3) [] + + Whois command is used to query various information about specific + user. The user maybe requested by their nickname and server name. + The query may find multiple matching users as there are no unique + nicknames in the SILC. The option maybe given to narrow + down the number of accepted results. If this is not defined there + are no limit of accepted results. The query may also be narrowed + down by defining the server name of the nickname. + + It is also possible to search the user by Client ID. If + is provided server must use it as the search value instead of + the . + + To prevent miss-use of this service wildcards in the nickname + or in the servername are not permitted. It is not allowed + to request all users on some server. The WHOIS requests must + be based on specific nickname request. + + The WHOIS request must be always forwarded to router by server + so that all users are searched. However, the server still must + search its locally connected clients. The server must send + this command to the server who owns the requested client. That + server must reply to the command. + + Reply messages to the command: + + Max Arguments: 7 + Arguments: (1) (2) + (3) [@] (4) + (5) (6) [] + (7) [] + + This command may reply with several command reply messages to + form a list of results. In this case the status payload will + include STATUS_LIST_START status in the first reply and + STATUS_LIST_END in the last reply to indicate the end of the + list. If there are only one reply the status is set to normal + STATUS_OK. + + The command replies include the Client ID of the nickname, + nickname and servername, username and hostnamea and users real + name. Client should process these replies only after the last + reply has been received with the STATUS_LIST_END status. If the + option were defined in the query there will be only + many replies from the server. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_LIST_START + SILC_STATUS_LIST_END + SILC_STATUS_ERR_NO_SUCH_NICK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + + + 2 SILC_COMMAND_WHOWAS + + Max Arguments: 2 + Arguments: (1) [@] (2) [] + + Whowas. This command is used to query history information about + specific user. The user maybe requested by their nickname and + server name. The query may find multiple matching users as there + are no unique nicknames in the SILC. The option maybe + given to narrow down the number of accepted results. If this + is not defined there are no limit of accepted results. The query + may also be narrowed down by defining the server name of the + nickname. + + To prevent miss-use of this service wildcards in the nickname + or in the servername are not permitted. The WHOWAS requests must + be based on specific nickname request. + + The WHOWAS request must be always forwarded to router by server + so that all users are searched. However, the server still must + search its locally connected clients. + + Reply messages to the command: + + Max Arguments: 3 + Arguments: (1) (2) [@] + (3) + + This command may reply with several command reply messages to form + a list of results. In this case the status payload will include + STATUS_LIST_START status in the first reply and STATUS_LIST_END in + the last reply to indicate the end of the list. If there are only + one reply the status is set to normal STATUS_OK. + + The command replies with nickname and username and hostname. + Every server must keep history for some period of time of its + locally connected clients. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_LIST_START + SILC_STATUS_LIST_END + SILC_STATUS_ERR_NO_SUCH_NICK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + + + 3 SILC_COMMAND_IDENTIFY + + Max Arguments: 2 + Arguments: (1) [@] (2) [] + + Identify. Identify command is almost analogous to WHOIS command, + except that it does not return as much information. Only relevant + information such as Client ID is returned. This is usually used + to get the Client ID of a client used in the communication with + the client. + + The query may find multiple matching users as there are no unique + nicknames in the SILC. The option maybe given to narrow + down the number of accepted results. If this is not defined there + are no limit of accepted results. The query may also be narrowed + down by defining the server name of the nickname. + + To prevent miss-use of this service wildcards in the nickname + or in the servername are not permitted. It is not allowed + to request all users on some server. The IDENTIFY requests must + be based on specific nickname request. + + Implementations may not want to give interface access to this + command as it is hardly a command that would be used a end user. + However, it must be implemented as it is used with private message + sending. + + The IDENTIFY must be always forwarded to router by server so that + all users are searched. However, server must still search its + locally connected clients. + + Reply messages to the command: + + Max Arguments: 4 + Arguments: (1) (2) + (3) [[@]] (4) [] + + This command may reply with several command reply messages to form + a list of results. In this case the status payload will include + STATUS_LIST_START status in the first reply and STATUS_LIST_END in + the last reply to indicate the end of the list. If there are only + one reply the status is set to normal STATUS_OK. + + The command replies with Client ID of the nickname and if more + information is available it may reply with nickname and username + and hostname. If the option were defined in the query + there will be only many replies from the server. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_LIST_START + SILC_STATUS_LIST_END + SILC_STATUS_ERR_NO_SUCH_NICK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + + + 4 SILC_COMMAND_NICK + + Max Arguments: 1 + Arguments: (1) + + Set/change nickname. This command is used to set nickname for + user. There is no limit of the length of the nickname in SILC. + Nickname must not include any spaces (` '), non-printable + characters, commas (`,') and any wildcard characters. Note: + nicknames in SILC are case-sensitive which must be taken into + account when searching clients by nickname. + + Reply messages to the command: + + Max Arguments: 2 + Arguments: (1) (2) + + This command is replied always with New ID Payload that is + generated by the server every time user changes their nickname. + Client receiving this payload must start using the received + Client ID as its current valid Client ID. The New ID Payload + is described in [SILC2]. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NICKNAME_IN_USE + SILC_STATUS_ERR_BAD_NICKNAME + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + + + 5 SILC_COMMAND_LIST + + Max Arguments: 2 + Arguments: (1) [] [] + + The list command is used to list channels and their topics on + current server. If the parameter is used, only the + status of that channel is displayed. Secret channels are not + listed at all. Private channels are listed with status indicating + that the channel is private. + + If the argument is specified the specified server's + channels are listed. In this case the command must be sent to + the server who owns the channel that was requested. + + Reply messages to the command: + + Max Arguments: 4 + Arguments: (1) (2) + (3) (4) + + This command may reply with several command reply messages to form + a list of results. In this case the status payload will include + STATUS_LIST_START status in the first reply and STATUS_LIST_END in + the last reply to indicate the end of the list. If there are only + one reply the status is set to normal STATUS_OK. + + This command replies with Channel ID, name and the topic of the + channel. If the channel is private channel the includes + "*private*" string. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_LIST_START + SILC_STATUS_LIST_END + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_CHANNEL + SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + SILC_STATUS_ERR_NO_SUCH_SERVER + + + 6 SILC_COMMAND_TOPIC + + Max Arguments: 2 + Arguments: (1) (2) []] + + This command is used to change or view the topic of a channel. + The topic for channel is returned if there is no + given. If the parameter is present, the topic + for that channel will be changed, if the channel modes permit + this action. + + Reply messages to the command: + + Max Arguments: 2 + Arguments: (1) (2) [] + + The command may reply with the topic of the channel if it is + set. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ON_CHANNEL + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_NO_SUCH_CHANNEL + SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + SILC_STATUS_ERR_NO_CHANNEL_ID + SILC_STATUS_ERR_BAD_CHANNEL_ID + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_CHANNEL_PRIV + + + 7 SILC_COMMAND_INVITE + + Max Arguments: 2 + Arguments: (1) (2) + + This command is used to invite other clients to join to the + channel. The argument is the target client's ID that + is being invited. The is the Channel ID of the + requested channel. The sender of this command must be on the + channel. This command must fail if the requested channel does + not exist, the requested client is already on the channel or if + the channel is invite only channel and the caller of this command + does not have at least channel operator privileges. + + Reply messages to the command: + + Max Arguments: 2 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_CLIENT_ID + SILC_STATUS_ERR_NO_CLIENT_ID + SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + SILC_STATUS_ERR_NO_CHANNEL_ID + SILC_STATUS_ERR_NOT_ON_CHANNEL + SILC_STATUS_ERR_USER_ON_CHANNEL + + + 8 SILC_COMMAND_QUIT + + Max Arguments: 1 + Arguments: (1) [] + + This command is used by client to end SILC session. The server + must close the connection to a client which sends this command. + if is given it will be sent to other clients on + channel if the client is on channel when quitting. + + Reply messages to the command: + + This command does not reply anything. + + + 9 SILC_COMMAND_KILL + + Max Arguments: 2 + Arguments: (1) (2) [] + + This command is used by SILC operators to remove a client from + SILC network. The removing has temporary effects and client may + reconnect to SILC network. The is the client to be + removed from SILC. The argument may be provided to + give to the removed client some information why it was removed + from the network. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_CLIENT_ID + SILC_STATUS_ERR_NO_CLIENT_ID + + + + + + 10 SILC_COMMAND_INFO + + Max Arguments: 1 + Arguments: (1) [] + + This command is used to fetch various information about a server. + If argument is specified the command must be sent to + the requested server. + + Reply messages to the command: + + Max Arguments: 3 + Arguments: (1) (2) + (3) + + This command replies with the Server ID of the server and a + string which tells the information about the server. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_SERVER + + + 11 SILC_COMMAND_CONNECT + + Max Arguments: 2 + Arguments: (1) + (2) [[:]] + + This command is used by operators to force a server to try to + establish a new connection to another router (if the connecting + server is normal server) or server (if the conneceting server is + router server). Operator may specify the server/router to be + connected by setting argument. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_SERVER_ID + SILC_STATUS_ERR_NO_SERVER_PRIV + SILC_STATUS_ERR_NO_ROUTER_PRIV + + + 12 SILC_COMMAND_PING + + Max Arguments: 1 + Arguments: (1) + + This command is used by client and server to test the communication + channel to its server if one suspects that the communication is not + working correctly. The is the ID of the server the + sender is connected to. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. Server returns + SILC_STATUS_OK in Status Payload if pinging was successful. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SERVER_ID + SILC_STATUS_ERR_NO_SUCH_SERVER + SILC_STATUS_ERR_NOT_REGISTERED + + + 13 SILC_COMMAND_OPER + + Max Arguments: 2 + Arguments: (1) (2) + + This command is used by normal client to obtain server operator + privileges on some server or router. Note that router operator + has router privileges that supersedes the server operator + privileges and this does not obtain those privileges. Client + must use SILCOPER command to obtain router level privileges. + + The is the username set in the server configurations + as operator. The is the data that the + client is authenticated against. It may be passphrase prompted + for user on client's screen or it may be public key + authentication data (data signed with private key), or + certificate. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_BAD_PASSWORD + SILC_STATUS_ERR_AUTH_FAILED + + + 14 SILC_COMMAND_JOIN + + Max Arguments: 3 + Arguments: (1) (2) [] + (3) [] + + Join to channel/create new channel. This command is used to + join to a channel. If the channel does not exist the channel is + created. If server is normal server this command must be forwarded + to router who will create the channel. The channel may be protected + with passphrase. If this is the case the passphrase must be sent + along the join command. + + The name of the must not include any spaces (` '), + non-printable characters, commas (`,') or any wildcard characters. + + Cipher to be used to secure the traffic on the channel may be + requested by sending the name of the requested . This + is used only if the channel does not exist and is created. If + the channel already exists the cipher set previously for the + channel will be used to secure the traffic. + + The server must check whether the user is allowed to join to + the requested channel. Various modes set to the channel affect + the ability of the user to join the channel. These conditions + are: + + o The user must be invited to the channel if the channel + is invite-only channel. + + o The Client ID/nickname/username/hostname must not match + any active bans. + + o The correct passphrase must be provided if passphrase + is set to the channel. + + o The user count limit, if set, must not be reached. + + Reply messages to the command: + + Max Arguments: 5 + Arguments: (1) (2) + (3) (4) + (5) [] + + This command replies with the channel name requested by the + client, channel ID of the channel and topic of the channel + if it exists. It also replies with the channel mode mask + which tells all the modes set on the channel. If the + channel is created the mode mask is zero (0). + + Client must not start transmitting to the channel even after + server has replied to this command. Client is permitted to + start transmitting on channel after server has sent packet + SILC_PACKET_CHANNEL_KEY to the client. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_WILDCARDS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_BAD_PASSWORD + SILC_STATUS_ERR_CHANNEL_IS_FULL + SILC_STATUS_ERR_NOT_INVITED + SILC_STATUS_ERR_BANNED_FROM_CHANNEL + SILC_STATUS_ERR_BAD_CHANNEL + SILC_STATUS_ERR_USER_ON_CHANNEL + + + 15 SILC_COMMAND_MOTD + + Max Arguments: 1 + Arguments: (1) + + This command is used to query the Message of the Day of a server. + + Reply messages to the command: + + Max Arguments: 2 + Arguments: (1) (2) [] + + This command replies with the motd message if it exists. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NO_SUCH_SERVER + + + 16 SILC_COMMAND_UMODE + + Max Arguments: 2 + Arguments: (1) (2) + + This command is used by client to set/unset modes for itself. + However, there are some modes that the client may not set itself, + but they will be set by server. However, client may unset any + mode. Modes may be masked together ORing them thus having + several modes set. Client must keep its client mode mask + locally so that the mode setting/unsetting would work without + problems. Client may change only its own modes. + + Following client modes are defined: + + 0x0000 SILC_UMODE_NONE + + No specific mode for client. This is the initial + setting when new client is created. The client is + normal client now. + + + 0x0001 SILC_UMODE_SERVER_OPERATOR + + Marks the user as server operator. Client cannot + set this mode itself. Server sets this mode to the + client when client attains the server operator + privileges by SILC_COMMAND_OPER command. Client + may unset the mode itself. + + + 0x0002 SILC_UMODE_ROUTER_OPERATOR + + Marks the user as router (SILC) operator. Client + cannot this mode itself. Router sets this mode to + the client when client attains the router operator + privileges by SILC_COMMAND_SILCOPER command. Client + may unset the mode itself. + + Reply messages to the command: + + Max Arguments: 2 + Arguments: (1) (2) + + This command replies with the changed client mode mask that + the client is required to keep locally. + + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NO_SUCH_CLIENT_ID + SILC_STATUS_ERR_BAD_CLIENT_ID + SILC_STATUS_ERR_NOT_YOU + SILC_STATUS_ERR_UNKNOWN_MODE + SILC_STATUS_ERR_NO_RECIPIENT + SILC_STATUS_ERR_NO_CLIENT_ID + + + 17 SILC_COMMAND_CMODE + + Max Arguments: 8 + Arguments: (1) (2) + (3) [] (4) [] + (5) [] (6) [] + (7) [] (8) [[:]] + + This command is used by client to set or change channel flags on + a channel. Channel has several modes that set various properties + of a channel. Modes may be masked together by ORing them thus + having several modes set. The is the ID of the + target channel. The client changing channel mode must be on + the same channel and poses sufficient privileges to be able to + change the mode. + + Following channel modes are defined: + + 0x0000 SILC_CMODE_NONE + + No specific mode on channel. This is the default when + channel is created. This means that channel is just plain + normal channel. + + + 0x0001 SILC_CMODE_PRIVATE + + Channel is private channel. Private channels are shown + in the channel list listed with SILC_COMMAND_LIST command + with indicatioin that the channel is private. Also, + client on private channel will no be detected to be on + the channel as the channel is not shown in the client's + currently joined channel list. Channel founder and + channel operator may set/unset this mode. + + Typical implementation would use [+|-]p on user interface + to set/unset this mode. + + + 0x0002 SILC_CMODE_SECRET + + Channel is secret channel. Secret channels are not shown + in the list listed with SILC_COMMAND_LIST command. Secret + channels can be considered to be invisible channels. + Channel founder and channel operator may set/unset this + mode. + + Typical implementation would use [+|-]s on user interface + to set/unset this mode. + + + 0x0004 SILC_CMODE_PRIVKEY + + Channel uses private channel key to protect the traffic + on the channel. When this mode is set the client will be + responsible to set the key it wants to use to encrypt and + decrypt the traffic on channel. Server generated channel + keys are not used at all. This mode provides additional + security as clients on channel may agree to use private + channel key that even servers do not know. Naturally, + this requires that every client on the channel knows + the key before hand (it is considered to be pre-shared- + key). This specification does not define how the private + channel key is set as it is entirely local setting on + client end. + + As it is local setting it is possible to have several + private channel keys on one channel. In this case several + clients can talk on same channel but only those clients + that share the key with the message sender will be able + to hear the talking. Client should not display those + message for the end user that it is not able to decrypt + when this mode is set. + + Only channel founder may set/unset this mode. If this + mode is unset the server will distribute new channel + key to all clients on the channel which will be used + thereafter. + + Typical implementation would use [+|-]k on user interface + to set/unset this mode. + + + 0x0008 SILC_CMODE_INVITE + + Channel is invite only channel. Client may join to this + channel only if it is invited to the channel. Channel + founder and channel operator may set/unset this mode. + + Typical implementation would use [+|-]i on user interface + to set/unset this mode. + + + 0x0010 SILC_CMODE_TOPIC + + The topic of the channel may only be set by client that + is channel founder or channel operator. Normal clients + on channel will not be able to set topic when this mode + is set. Channel founder and channel operator may set/ + unset this mode. + + Typical implementation would use [+|-]t on user interface + to set/unset this mode. + + + 0x0020 SILC_CMODE_ULIMIT + + User limit has been set to the channel. New clients + may not join to the channel when the limit set is + reached. Channel founder and channel operator may set/ + unset the limit. The argument is the + number of limited users. + + Typical implementation would use [+|-]l on user interface + to set/unset this mode. + + + 0x0040 SILC_CMODE_PASSPHRASE + + Passphrase has been set to the channel. Client may + join to the channel only if it is able to provide the + correct passphrase. Setting passphrases to channel + is entirely safe as all commands are protected in the + SILC network. Only channel founder may set/unset + the passphrase. The argument is the + set passphrase. + + Typical implementation would use [+|-]a on user interface + to set/unset this mode. + + + 0x0080 SILC_CMODE_BAN + + Ban mask has been set to the channel. The ban mask + may be used to ban specific clients to join the channel. + The argument is the set ban mask. When + unsetting a ban mask the mask must be provided as + argument. Channel founder and channel operator may + set/unset this mode. Channel founder may not be + added to the ban list. + + Typical implementation would use [+|-]b on user interface + to set/unset this mode. + + + 0x0100 SILC_CMODE_INVITE + + Invite list has been set to the channel. The invite list + can be used to mark the clients that is able to join + channel without being invited when the channel is set to + be invite-only channel. The argument is the + set invite mask. When unsetting entry from the invite list + the entry must be provided as argument. Channel founder and + channel operator may set/unset this mode. + + Typical implementation would use [+|-]I on user interface + to set/unset this mode. + + + 0x0200 SILC_CMODE_OPERATOR + + Sets channel operator privileges on the channel for a + client on the channel. The argument is the + target client on the channel. Channel founder and + channel operator may set/unset (promote/demote) this + mode. + + Typical implementation would use [+|-]o on user interface + to set/unset this mode. + + + 0x0400 SILC_CMODE_CIPHER + + Sets specific cipher to be used to protect channel + traffic. The argument is the requested cipher. + When set or unset the server must re-generate new + channel key. If argument is specified with + argument the new key is generated of + length. + + Typical implementation would use [+|-]c on user interface + to set/unset this mode. + + + To make the mode system work, client must keep the channel mode + mask locally so that the mode setting and unsetting would work + without problems. The client receives the initial channel mode + mask when it joins to the channel. When the mode changes on + channel the server distributes the changed channel mode mask to + all clients on the channel by sending SILC_COMMAND_CMODE command + reply packet. + + + Reply messages to the command: + + Max Arguments: 2 + Arguments: (1) (2) + + This command replies with the changed channel mode mask that + client is required to keep locally. The same mask is also + sent to all clients on channel by sending additional command + reply to them. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ON_CHANNEL + SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + SILC_STATUS_ERR_BAD_CHANNEL_ID + SILC_STATUS_ERR_NO_CHANNEL_ID + SILC_STATUS_ERR_NO_CHANNEL_PRIV + SILC_STATUS_ERR_UNKNOWN_MODE + SILC_STATUS_ERR_NO_CLIENT_ID + + + + + 18 SILC_COMMAND_KICK + + Max Arguments: 3 + Arguments: (1) (2) + (3) [] + + This command is used by channel operators to remove a client from + channel. The argument is the channel the client to be + removed is on currently. Note that the "kicker" must be on the same + channel. If is provided it will be sent to the removed + client. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NO_SUCH_CHANNEL + SILC_STATUS_ERR_NO_SUCH_CLIENT_ID + SILC_STATUS_ERR_NO_CHANNEL_PRIV + SILC_STATUS_ERR_NO_CLIENT_ID + + + 19 SILC_COMMAND_RESTART + + Max Arguments: 0 + Arguments: None + + This command may only be used by server operator to force a + server to restart itself. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NO_SERVER_PRIV + + + 20 SILC_COMMAND_CLOSE + + Max Arguments: 1 + Arguments: (1) + + This command is used only by operator to close connection to a + remote site. The argument is the ID of the remote + site and must be valid. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NO_SUCH_SERVER + SILC_STATUS_ERR_NO_SERVER_PRIV + SILC_STATUS_ERR_NO_SUCH_SERVER_ID + + + 21 SILC_COMMAND_DIE + + Max Arguments: 0 + Arguments: None + + This command is used only by operator to shutdown the server. + All connections to the server will be closed and the server is + shutdown. + + Reply messages to the command: + + + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NO_SERVER_PRIV + + + 22 SILC_COMMAND_SILCOPER + + Max Arguments: 2 + Arguments: (1) (2) + + This command is used by normal client to obtain router operator + privileges (also known as SILC operator) on some router. Note + that router operator has router privileges that supersedes the + server operator privileges. + + The is the username set in the server configurations + as operator. The is the data that the + client is authenticated against. It may be passphrase prompted + for user on client's screen or it may be public key + authentication data (data signed with private key), or + certificate. + + Difference between router operator and server operator is that + router operator is able to handle cell level properties while + server operator (even on router server) is able to handle only + local properties, such as, local connections and normal server + administration. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_BAD_PASSWORD + SILC_STATUS_ERR_AUTH_FAILED + + + 23 SILC_COMMAND_LEAVE + + Max Arguments: 1 + Arguments: (1) + + This command is used by client to leave a channel the client is + joined to. After a client has leaved the channel the server + must create new key for the channel and distribute to all clients + still currently on the channel. + + Reply messages to the command: + + Max Arguments: 1 + Arguments: (1) + + This command replies only with Status Payload. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + SILC_STATUS_ERR_BAD_CHANNEL_ID + SILC_STATUS_ERR_NO_CHANNEL_ID + + + 24 SILC_COMMAND_NAMES + + Max Arguments: 1 + Arguments: (1) + + This command is used to list user names currently on the requested + channel; argument . The server must resolve the + user names and send a comma (`,') separated list of user names + on the channel. Server or router may resolve the names by sending + SILC_COMMAND_WHOIS commands. + + If the requested channel is a private or secret channel, this + command must not send the list of users, as private and secret + channels cannot be seen by outside. In this case the returned + name list may include a indication that the server could not + resolve the names of the users on the channel. + + Reply messages to the command: + + Max Arguments: 3 + Arguments: (1) (2) + (3) (4) + + This command replies with the Channel ID of the requested channel, + comma separated list of users on the channel and Client ID list + of the users on the list. The Client ID list has Client ID's + of all users in the list. First Client ID in the list must be + the Client ID of the first user in . The Client ID + List is formed by adding Client ID's each after each. Note that + the Client ID list is binary data. + + Status messages: + + SILC_STATUS_OK + SILC_STATUS_ERR_NOT_REGISTERED + SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + SILC_STATUS_ERR_TOO_MANY_PARAMS + SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + SILC_STATUS_ERR_BAD_CHANNEL_ID + SILC_STATUS_ERR_NO_CHANNEL_ID + SILC_STATUS_ERR_NOT_ON_CHANNEL + + + 25 - 254 + + Currently undefined commands. + + + 255 SILC_COMMAND_MAX + + Reserved command. This must not be sent. +.in 3 + + +.ti 0 +5.3 SILC Command Status Types + +.ti 0 +5.3.1 SILC Command Status Payload + +Command Status Payload is sent in command reply messages to indicate +the status of the command. The payload is one of argument in the +command thus this is the data area in Command Argument Payload described +in [SILC2]. The payload is only 2 bytes of length. Following diagram +represents the Command Status Payload (field is always in MSB order). + + +.in 21 +.nf + 1 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| Status Message | ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +.in 3 + +.ce +Figure 5: SILC Command Status Payload + + +.in 6 +o Status Message (2 bytes) - Indicates the status message. + All Status messages are described in the next section. +.in 3 + + +.ti 0 +5.3.2 SILC Command Status List + +Command Status messages are returned in the command reply messages +to indicate whether the command were executed without errors. If error +has occured the status tells which error occured. Status payload only +sends numeric reply about the status. Receiver of the payload must +convert the numeric values into human readable error messages. The +list of status messages below has an example human readable error +messages that client may display for the user. + +List of all defined command status messages following. + +.in 0 + Generic status messages: + + 0 SILC_STATUS_OK + + Ok status. Everything went Ok. The status payload maybe + safely ignored in this case. + + 1 SILC_STATUS_LIST_START + + Start of the list. There will be several command replies and + this reply is the start of the list. + + 2 SILC_STATUS_LIST_END + + End of the list. There were several command replies and this + reply is the last of the list. There won't be other replies + beloning to this list after this one. + + 3 - 9 + + Currently undefined and has been reserved for the future. + + + Error status message: + + 10 SILC_STATUS_ERR_NO_SUCH_NICK + + "No such nickname". Requested nickname does not exist. + + 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL + + "No such channel". Requested channel name does not exist. + + 12 SILC_STATUS_ERR_NO_SUCH_SERVER + + "No such server". Requested server name does not exist. + + 13 SILC_STATUS_ERR_TOO_MANY_TARGETS + + "Duplicate recipients. No message delivered". Message were + tried to be sent to recipient which has several occurrences in + the recipient list. + + 14 SILC_STATUS_ERR_NO_RECIPIENT + + "No recipient given". Command required recipient which was + not provided. + + 15 SILC_STATUS_ERR_UNKNOWN_COMMAND + + "Unknown command". Command sent to server is unknown by the + server. + + 16 SILC_STATUS_ERR_WILDCARDS + + "Wildcards cannot be used". Wildcards were provided but they + weren't permitted. + + 17 SILC_STATUS_ERR_NO_CLIENT_ID + + "No Client ID given". Client ID were expected as command + parameter but were not found. + + 18 SILC_STATUS_ERR_NO_CHANNEL_ID + + "No Channel ID given". Channel ID were expected as command + parameter but were not found. + + 19 SILC_STATUS_ERR_NO_SERVER_ID + + "No Serve ID given". Server ID were expected as command + parameter but were not found. + + 20 SILC_STATUS_ERR_BAD_CLIENT_ID + + "Bad Client ID". Client ID provided were erroneous. + + 21 SILC_STATUS_ERR_BAD_CHANNEL_ID + + "Bad Channel ID". Channel ID provided were erroneous. + + 22 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID + + "No such Client ID". Client ID provided does not exist. + + + 23 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID + + "No such Channel ID". Channel ID provided does not exist. + + 24 SILC_STATUS_ERR_NICKNAME_IN_USE + + "Nickname already exists". Nickname created could not be + registered because number of same nicknames were already set to + maximum. This is not expected to happen in real life but is + possible to occur. + + 25 SILC_STATUS_ERR_NOT_ON_CHANNEL + + "You are not on that channel". The command were specified for + client user is not currently on. + + 26 SILC_STATUS_ERR_USER_ON_CHANNEL + + "User already on channel". User were invited on channel they + already are on. + + 27 SILC_STATUS_ERR_NOT_REGISTERED + + "You have not registered". User executed command that requires + the client to be registered on the server before it may be + executed. + + 28 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS + + "Not enough parameters". Command requires more parameters + than provided. + + 29 SILC_STATUS_ERR_TOO_MANY_PARAMS + + "Too many parameters". Too many parameters were provided + for the command. + + 30 SILC_STATUS_ERR_PERM_DENIED + + "Your host is not among the privileged". The client tried to + register on server that does not allow this host to connect. + + 31 SILC_STATUS_ERR_BANNED_FROM_SERVER + + "You are banned from this server". The client tried to register + on server that has explicitly denied this host to connect. + + + + 32 SILC_STATUS_ERR_BAD_PASSWORD + + "Cannot join channel. Incorrect password". Password provided for + channel were not accepted. + + 33 SILC_STATUS_ERR_CHANNEL_IS_FULL + + "Cannot join channel. Channel is full". The channel is full + and client cannot be joined to it. + + 34 SILC_STATUS_ERR_NOT_INVITED + + "Cannot join channel. You have not been invited". The channel + is invite only channel and client has not been invited. + + 35 SILC_STATUS_ERR_BANNED_FROM_CHANNEL + + "Cannot join channel. You have been banned". The client has + been banned from the channel. + + 36 SILC_STATUS_ERR_UNKNOWN_MODE + + "Unknown mode". Mode provided by the client were unknown to + the server. + + 37 SILC_STATUS_ERR_NOT_YOU + + "Cannot change mode for other users". User tried to change + someone else's mode. + + 38 SILC_STATUS_ERR_NO_CHANNEL_PRIV + + "Permission denied. You are not channel operator". Command may + be executed only by channel operator. + + 39 SILC_STATUS_ERR_NO_SERVER_PRIV + + "Permission denied. You are not server operator". Command may + be executed only by server operator. + + 40 SILC_STATUS_ERR_NO_ROUTER_PRIV + + "Permission denied. You are not SILC operator". Command may be + executed only by router (SILC) operator. + + 41 SILC_STATUS_ERR_BAD_NICKNAME + + "Bad nickname". Nickname requested contained illegal characters + or were malformed. + + 42 SILC_STATUS_ERR_BAD_CHANNEL + + "Bad channel name". Channel requested contained illegal characters + or were malformed. + + 43 SILC_STATUS_ERR_AUTH_FAILED + + "Authentication failed". The authentication data sent as + argument were wrong and thus authentication failed. +.in 3 + + +.ti 0 +6 Security Considerations + +Security is central to the design of this protocol, and these security +considerations permeate the specification. + + + + + +.ti 0 +7 References + +[SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft, + June 2000. + +[SILC3] Riikonen, P., "SILC Key Exchange and Authentication + Protocols", Internet Draft, June 2000. + +[IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol", + RFC 1459, May 1993. + +[SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol", + Internet Draft. + +[PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440, + November 1998. + +[SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693, + September 1999. + +[PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key + Infrastructure, Certificate and CRL Profile", RFC 2459, + January 1999. + +[Schneier] Schneier, B., "Applied Cryptography Second Edition", + John Wiley & Sons, New York, NY, 1996. + +[Menezes] Menezes, A., et al, "Handbook of Applied Cryptography", + CRC Press 1997. + +[OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol", + RFC 2412, November 1998. + +[ISAKMP] Maughan D., et al, "Internet Security Association and + Key Management Protocol (ISAKMP)", RFC 2408, November + 1998. + +[IKE] Harkins D., and Carrel D., "The Internet Key Exhange + (IKE)", RFC 2409, November 1998. + +[HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message + Authentication", RFC 2104, February 1997. + + + +.ti 0 +8 Author's Address + +.nf +Pekka Riikonen +Kasarmikatu 11 A4 +70110 Kuopio +Finland + +EMail: priikone@poseidon.pspt.fi + +This Internet-Draft expires 13 May 2001 diff --git a/lib/silccore/silcnotify.h b/lib/silccore/silcnotify.h new file mode 100644 index 00000000..42fe9b12 --- /dev/null +++ b/lib/silccore/silcnotify.h @@ -0,0 +1,36 @@ +/* + + silcnotify.h + + Author: Pekka Riikonen + + Copyright (C) 1997 - 2000 Pekka Riikonen + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + +*/ + +#ifndef SILCNOTIFY_H +#define SILCNOTIFY_H + +/* Type definition of notify type */ +typedef unsigned short SilcNotifyType; + +/* SILC notify types. Server may send these notify types to client to + notify of some action. Server also sends human readable notify message + to the client which client may ignore. */ +#define SILC_NOTIFY_TYPE_NONE 0 /* no specific type */ +#define SILC_NOTIFY_TYPE_INVITE 1 /* "invites you to channel" */ +#define SILC_NOTIFY_TYPE_JOIN 2 /* "has joined channel" */ +#define SILC_NOTIFY_TYPE_LEAVE 3 /* "has left channel" */ +#define SILC_NOTIFY_TYPE_SIGNOFF 4 /* "signoff" */ + +#endif -- 2.43.0