bsd-arc4random.c revision 162853 
1/*
2 * Copyright (c) 1999,2000,2004 Damien Miller <djm@mindrot.org>
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16
17#include "includes.h"
18
19#include <sys/types.h>
20
21#include <string.h>
22#include <stdarg.h>
23
24#include "log.h"
25
26#ifndef HAVE_ARC4RANDOM
27
28#include <openssl/rand.h>
29#include <openssl/rc4.h>
30#include <openssl/err.h>
31
32/* Size of key to use */
33#define SEED_SIZE 20
34
35/* Number of bytes to reseed after */
36#define REKEY_BYTES	(1 << 24)
37
38static int rc4_ready = 0;
39static RC4_KEY rc4;
40
41unsigned int
42arc4random(void)
43{
44	unsigned int r = 0;
45	static int first_time = 1;
46
47	if (rc4_ready <= 0) {
48		if (first_time)
49			seed_rng();
50		first_time = 0;
51		arc4random_stir();
52	}
53
54	RC4(&rc4, sizeof(r), (unsigned char *)&r, (unsigned char *)&r);
55
56	rc4_ready -= sizeof(r);
57
58	return(r);
59}
60
61void
62arc4random_stir(void)
63{
64	unsigned char rand_buf[SEED_SIZE];
65	int i;
66
67	memset(&rc4, 0, sizeof(rc4));
68	if (RAND_bytes(rand_buf, sizeof(rand_buf)) <= 0)
69		fatal("Couldn't obtain random bytes (error %ld)",
70		    ERR_get_error());
71	RC4_set_key(&rc4, sizeof(rand_buf), rand_buf);
72
73	/*
74	 * Discard early keystream, as per recommendations in:
75	 * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
76	 */
77	for(i = 0; i <= 256; i += sizeof(rand_buf))
78		RC4(&rc4, sizeof(rand_buf), rand_buf, rand_buf);
79
80	memset(rand_buf, 0, sizeof(rand_buf));
81
82	rc4_ready = REKEY_BYTES;
83}
84#endif /* !HAVE_ARC4RANDOM */
85