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keys/tripe-keys.in, keys/tripe-keys.conf.5.in: Allow setting attributes.
[tripe] / common / protocol.h
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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 *
12 * TrIPE is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
e04c2d50 16 *
165db1a8 17 * TrIPE is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
e04c2d50 21 *
165db1a8 22 * You should have received a copy of the GNU General Public License
23 * along with TrIPE; if not, write to the Free Software Foundation,
24 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
25 */
26
165db1a8 27#ifndef TRIPE_PROTOCOL_H
28#define TRIPE_PROTOCOL_H
29
30/*----- TrIPE protocol ----------------------------------------------------*/
31
165efde7
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32#define TRIPE_PORT 4070 /* Assigned by IANA */
33
165db1a8 34/* --- TrIPE message format --- *
35 *
36 * A packet begins with a single-byte message type. The top four bits are a
37 * category code used to send the message to the right general place in the
38 * code; the bottom bits identify the actual message type.
39 */
40
41#define MSG_CATMASK 0xf0
42#define MSG_TYPEMASK 0x0f
43
44/* --- Encrypted message packets --- *
45 *
46 * Messages of category @MSG_PACKET@ contain encrypted network packets. The
47 * message content is a symmetric-encrypted block (see below). Reception of
48 * a packet encrypted under a new key implicitly permits that key to be used
49 * to send further packets.
50 *
51 * The only packet type accepted is zero.
52 *
53 * Packets may be encrypted under any live keyset, but should use the most
54 * recent one.
55 */
56
57#define MSG_PACKET 0x00
58
59/* --- Key exchange packets --- */
60
61#define MSG_KEYEXCH 0x10
62
63#define KX_PRECHAL 0u
de7bd20b
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64#define KX_CHAL 1u
65#define KX_REPLY 2u
66#define KX_SWITCH 3u
67#define KX_SWITCHOK 4u
68#define KX_NMSG 5u
165db1a8 69
0ba8de86 70/* --- Miscellaneous packets --- */
71
72#define MSG_MISC 0x20
73
74#define MISC_NOP 0u /* Do nothing; ignore me */
75#define MISC_PING 1u /* Transport-level ping */
76#define MISC_PONG 2u /* Transport-level ping response */
77#define MISC_EPING 3u /* Encrypted ping */
78#define MISC_EPONG 4u /* Encrypted ping response */
37941236 79#define MISC_GREET 5u /* A greeting from a NATed peer */
0ba8de86 80
165db1a8 81/* --- Symmetric encryption and keysets --- *
82 *
83 * Packets consist of an 80-bit MAC, a 32-bit sequence number, and the
84 * encrypted payload.
85 *
86 * The plaintext is encrypted using Blowfish in CBC mode with ciphertext
0ba8de86 87 * stealing (as described in [Schneier]). The initialization vector is
165db1a8 88 * selected randomly, and prepended to the actual ciphertext.
89 *
90 * The MAC is computed using the HMAC construction with RIPEMD160 over the
91 * sequence number and the ciphertext (with IV); the first 80 bits of the
92 * output are used. (This is the minimum allowed by the draft FIPS for HMAC,
93 * and the recommended truncation.)
94 *
95 * A keyset consists of
96 *
97 * * an integrity (MAC) key;
98 * * a confidentiality (encryption) key; and
99 * * a sequence numbering space
100 *
101 * in each direction. The packets sent by a host encrypted under a
102 * particular keyset are assigned consecutive sequence numbers starting from
103 * zero. The receiving host must ensure that it only accepts each packet at
104 * most once. It should maintain a window of sequence numbers: packets with
105 * numbers beyond the end of the window are accepted and cause the window to
106 * be advanced; packets with numbers before the start of the window are
107 * rejected; packets with numbers which appear within the window are accepted
108 * only if the number has not been seen before.
109 *
110 * When a host sends a @KX_SWITCH@ or @KX_SWITCHOK@ message, it installs the
111 * newly-negotiated keyset in a `listen-only' state: it may not send a packet
112 * encrypted under the keyset until either it has received a @KX_SWITCH@ or
113 * @KX_SWITCHOK@ message, or a @MSG_PACKET@ encrypted under the keyset, from
114 * its peer.
115 */
116
117/*----- That's all, folks -------------------------------------------------*/
118
119#endif