1 /* $OpenBSD: tcp_subr.c,v 1.98 2007/06/25 12:17:43 markus Exp $ */
2 /* $NetBSD: tcp_rndiss.c,v 1.4 2011/12/17 20:05:39 tls Exp $ */
3
4 /*
5 * Copyright (c) 1982, 1986, 1988, 1990, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995
33 *
34 * NRL grants permission for redistribution and use in source and binary
35 * forms, with or without modification, of the software and documentation
36 * created at NRL provided that the following conditions are met:
37 *
38 * 1. Redistributions of source code must retain the above copyright
39 * notice, this list of conditions and the following disclaimer.
40 * 2. Redistributions in binary form must reproduce the above copyright
41 * notice, this list of conditions and the following disclaimer in the
42 * documentation and/or other materials provided with the distribution.
43 * 3. All advertising materials mentioning features or use of this software
44 * must display the following acknowledgements:
45 * This product includes software developed by the University of
46 * California, Berkeley and its contributors.
47 * This product includes software developed at the Information
48 * Technology Division, US Naval Research Laboratory.
49 * 4. Neither the name of the NRL nor the names of its contributors
50 * may be used to endorse or promote products derived from this software
51 * without specific prior written permission.
52 *
53 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
54 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
55 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
56 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
57 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
58 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
59 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
60 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
61 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
62 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
63 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
64 *
65 * The views and conclusions contained in the software and documentation
66 * are those of the authors and should not be interpreted as representing
67 * official policies, either expressed or implied, of the US Naval
68 * Research Laboratory (NRL).
69 */
70
71 #include <sys/cdefs.h>
72 __KERNEL_RCSID(0, "$NetBSD: tcp_rndiss.c,v 1.4 2011/12/17 20:05:39 tls Exp $");
73
74 #include <sys/param.h>
75 #include <sys/cprng.h>
76
77 #include <netinet/tcp.h>
78 #include <netinet/tcp_seq.h>
79 #include <netinet/tcp_rndiss.h>
80
81 #define TCP_RNDISS_ROUNDS 16
82 #define TCP_RNDISS_OUT 7200
83 #define TCP_RNDISS_MAX 30000
84
85 u_int8_t tcp_rndiss_sbox[128];
86 u_int16_t tcp_rndiss_msb;
87 u_int16_t tcp_rndiss_cnt;
88 long tcp_rndiss_reseed;
89
90 u_int16_t
tcp_rndiss_encrypt(u_int16_t val)91 tcp_rndiss_encrypt(u_int16_t val)
92 {
93 u_int16_t sum = 0, i;
94
95 for (i = 0; i < TCP_RNDISS_ROUNDS; i++) {
96 sum += 0x79b9;
97 val ^= ((u_int16_t)tcp_rndiss_sbox[(val^sum) & 0x7f]) << 7;
98 val = ((val & 0xff) << 7) | (val >> 8);
99 }
100
101 return val;
102 }
103
104 void
tcp_rndiss_init(void)105 tcp_rndiss_init(void)
106 {
107 cprng_strong(kern_cprng, tcp_rndiss_sbox, sizeof(tcp_rndiss_sbox), 0);
108
109 tcp_rndiss_reseed = time_second + TCP_RNDISS_OUT;
110 tcp_rndiss_msb = tcp_rndiss_msb == 0x8000 ? 0 : 0x8000;
111 tcp_rndiss_cnt = 0;
112 }
113
114 tcp_seq
tcp_rndiss_next(void)115 tcp_rndiss_next(void)
116 {
117 if (tcp_rndiss_cnt >= TCP_RNDISS_MAX ||
118 time_second > tcp_rndiss_reseed)
119 tcp_rndiss_init();
120
121 /* (arc4random() & 0x7fff) ensures a 32768 byte gap between ISS */
122 return ((tcp_rndiss_encrypt(tcp_rndiss_cnt++) | tcp_rndiss_msb) <<16) |
123 (cprng_fast32() & 0x7fff);
124 }
125