~mdw / tripe / blame
| Commit | Line | Data |
|---|---|---|
| 165db1a8 | 1 | /* -*-c-*- |
| 165db1a8 | 2 | * |
| 3 | * Protocol definition for TrIPE | |
| 4 | * | |
| 5 | * (c) 2003 Straylight/Edgeware | |
| 6 | */ | |
| 7 | ||
| e04c2d50 | 8 | /*----- Licensing notice --------------------------------------------------* |
| 165db1a8 | 9 | * |
| 10 | * This file is part of Trivial IP Encryption (TrIPE). | |
| 11 | * | |
| 11ad66c2 MW |
12 | * TrIPE is free software: you can redistribute it and/or modify it under |
| 13 | * the terms of the GNU General Public License as published by the Free | |
| 14 | * Software Foundation; either version 3 of the License, or (at your | |
| 15 | * option) any later version. | |
| e04c2d50 | 16 | * |
| 11ad66c2 MW |
17 | * TrIPE is distributed in the hope that it will be useful, but WITHOUT |
| 18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 19 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 20 | * for more details. | |
| e04c2d50 | 21 | * |
| 165db1a8 | 22 | * You should have received a copy of the GNU General Public License |
| 11ad66c2 | 23 | * along with TrIPE. If not, see <https://www.gnu.org/licenses/>. |
| 165db1a8 | 24 | */ |
| 25 | ||
| 165db1a8 | 26 | #ifndef TRIPE_PROTOCOL_H |
| 27 | #define TRIPE_PROTOCOL_H | |
| 28 | ||
| 29 | /*----- TrIPE protocol ----------------------------------------------------*/ | |
| 30 | ||
| 165efde7 MW |
31 | #define TRIPE_PORT 4070 /* Assigned by IANA */ |
| 32 | ||
| 165db1a8 | 33 | /* --- TrIPE message format --- * |
| 34 | * | |
| 35 | * A packet begins with a single-byte message type. The top four bits are a | |
| 36 | * category code used to send the message to the right general place in the | |
| 37 | * code; the bottom bits identify the actual message type. | |
| 38 | */ | |
| 39 | ||
| 40 | #define MSG_CATMASK 0xf0 | |
| 41 | #define MSG_TYPEMASK 0x0f | |
| 42 | ||
| 43 | /* --- Encrypted message packets --- * | |
| 44 | * | |
| 45 | * Messages of category @MSG_PACKET@ contain encrypted network packets. The | |
| 46 | * message content is a symmetric-encrypted block (see below). Reception of | |
| 47 | * a packet encrypted under a new key implicitly permits that key to be used | |
| 48 | * to send further packets. | |
| 49 | * | |
| 50 | * The only packet type accepted is zero. | |
| 51 | * | |
| 52 | * Packets may be encrypted under any live keyset, but should use the most | |
| 53 | * recent one. | |
| 54 | */ | |
| 55 | ||
| 56 | #define MSG_PACKET 0x00 | |
| 57 | ||
| 58 | /* --- Key exchange packets --- */ | |
| 59 | ||
| 60 | #define MSG_KEYEXCH 0x10 | |
| 61 | ||
| 62 | #define KX_PRECHAL 0u | |
| de7bd20b MW |
63 | #define KX_CHAL 1u |
| 64 | #define KX_REPLY 2u | |
| 65 | #define KX_SWITCH 3u | |
| 66 | #define KX_SWITCHOK 4u | |
| 8362ac1c MW |
67 | #define KX_TOKENRQ 5u |
| 68 | #define KX_TOKEN 6u | |
| 69 | #define KX_KNOCK 7u | |
| 70 | #define KX_NMSG 8u | |
| 165db1a8 | 71 | |
| 0ba8de86 | 72 | /* --- Miscellaneous packets --- */ |
| 73 | ||
| 74 | #define MSG_MISC 0x20 | |
| 75 | ||
| 76 | #define MISC_NOP 0u /* Do nothing; ignore me */ | |
| 77 | #define MISC_PING 1u /* Transport-level ping */ | |
| 78 | #define MISC_PONG 2u /* Transport-level ping response */ | |
| 79 | #define MISC_EPING 3u /* Encrypted ping */ | |
| 80 | #define MISC_EPONG 4u /* Encrypted ping response */ | |
| 37941236 | 81 | #define MISC_GREET 5u /* A greeting from a NATed peer */ |
| 067aa5f0 | 82 | #define MISC_BYE 6u /* Departure notification */ |
| 0ba8de86 | 83 | |
| 165db1a8 | 84 | /* --- Symmetric encryption and keysets --- * |
| 85 | * | |
| 86 | * Packets consist of an 80-bit MAC, a 32-bit sequence number, and the | |
| 87 | * encrypted payload. | |
| 88 | * | |
| 89 | * The plaintext is encrypted using Blowfish in CBC mode with ciphertext | |
| 0ba8de86 | 90 | * stealing (as described in [Schneier]). The initialization vector is |
| 165db1a8 | 91 | * selected randomly, and prepended to the actual ciphertext. |
| 92 | * | |
| 93 | * The MAC is computed using the HMAC construction with RIPEMD160 over the | |
| 94 | * sequence number and the ciphertext (with IV); the first 80 bits of the | |
| 95 | * output are used. (This is the minimum allowed by the draft FIPS for HMAC, | |
| 96 | * and the recommended truncation.) | |
| 97 | * | |
| 98 | * A keyset consists of | |
| 99 | * | |
| 100 | * * an integrity (MAC) key; | |
| 101 | * * a confidentiality (encryption) key; and | |
| 102 | * * a sequence numbering space | |
| 103 | * | |
| 104 | * in each direction. The packets sent by a host encrypted under a | |
| 105 | * particular keyset are assigned consecutive sequence numbers starting from | |
| 106 | * zero. The receiving host must ensure that it only accepts each packet at | |
| 107 | * most once. It should maintain a window of sequence numbers: packets with | |
| 108 | * numbers beyond the end of the window are accepted and cause the window to | |
| 109 | * be advanced; packets with numbers before the start of the window are | |
| 110 | * rejected; packets with numbers which appear within the window are accepted | |
| 111 | * only if the number has not been seen before. | |
| 112 | * | |
| 113 | * When a host sends a @KX_SWITCH@ or @KX_SWITCHOK@ message, it installs the | |
| 114 | * newly-negotiated keyset in a `listen-only' state: it may not send a packet | |
| 115 | * encrypted under the keyset until either it has received a @KX_SWITCH@ or | |
| 116 | * @KX_SWITCHOK@ message, or a @MSG_PACKET@ encrypted under the keyset, from | |
| 117 | * its peer. | |
| 118 | */ | |
| 119 | ||
| 120 | /*----- That's all, folks -------------------------------------------------*/ | |
| 121 | ||
| 122 | #endif |