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165db1a8 | 1 | /* -*-c-*- |
2 | * | |
165db1a8 | 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 | |
67 | #define KX_NMSG 5u | |
165db1a8 | 68 | |
0ba8de86 | 69 | /* --- Miscellaneous packets --- */ |
70 | ||
71 | #define MSG_MISC 0x20 | |
72 | ||
73 | #define MISC_NOP 0u /* Do nothing; ignore me */ | |
74 | #define MISC_PING 1u /* Transport-level ping */ | |
75 | #define MISC_PONG 2u /* Transport-level ping response */ | |
76 | #define MISC_EPING 3u /* Encrypted ping */ | |
77 | #define MISC_EPONG 4u /* Encrypted ping response */ | |
37941236 | 78 | #define MISC_GREET 5u /* A greeting from a NATed peer */ |
0ba8de86 | 79 | |
165db1a8 | 80 | /* --- Symmetric encryption and keysets --- * |
81 | * | |
82 | * Packets consist of an 80-bit MAC, a 32-bit sequence number, and the | |
83 | * encrypted payload. | |
84 | * | |
85 | * The plaintext is encrypted using Blowfish in CBC mode with ciphertext | |
0ba8de86 | 86 | * stealing (as described in [Schneier]). The initialization vector is |
165db1a8 | 87 | * selected randomly, and prepended to the actual ciphertext. |
88 | * | |
89 | * The MAC is computed using the HMAC construction with RIPEMD160 over the | |
90 | * sequence number and the ciphertext (with IV); the first 80 bits of the | |
91 | * output are used. (This is the minimum allowed by the draft FIPS for HMAC, | |
92 | * and the recommended truncation.) | |
93 | * | |
94 | * A keyset consists of | |
95 | * | |
96 | * * an integrity (MAC) key; | |
97 | * * a confidentiality (encryption) key; and | |
98 | * * a sequence numbering space | |
99 | * | |
100 | * in each direction. The packets sent by a host encrypted under a | |
101 | * particular keyset are assigned consecutive sequence numbers starting from | |
102 | * zero. The receiving host must ensure that it only accepts each packet at | |
103 | * most once. It should maintain a window of sequence numbers: packets with | |
104 | * numbers beyond the end of the window are accepted and cause the window to | |
105 | * be advanced; packets with numbers before the start of the window are | |
106 | * rejected; packets with numbers which appear within the window are accepted | |
107 | * only if the number has not been seen before. | |
108 | * | |
109 | * When a host sends a @KX_SWITCH@ or @KX_SWITCHOK@ message, it installs the | |
110 | * newly-negotiated keyset in a `listen-only' state: it may not send a packet | |
111 | * encrypted under the keyset until either it has received a @KX_SWITCH@ or | |
112 | * @KX_SWITCHOK@ message, or a @MSG_PACKET@ encrypted under the keyset, from | |
113 | * its peer. | |
114 | */ | |
115 | ||
116 | /*----- That's all, folks -------------------------------------------------*/ | |
117 | ||
118 | #endif |