bsd-arc4random.c revision 124208 
1/*
2 * Copyright (c) 1999-2000 Damien Miller.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26#include "log.h"
27
28RCSID("$Id: bsd-arc4random.c,v 1.7 2003/05/18 14:13:38 djm Exp $");
29
30#ifndef HAVE_ARC4RANDOM
31
32#include <openssl/rand.h>
33#include <openssl/rc4.h>
34#include <openssl/err.h>
35
36/* Size of key to use */
37#define SEED_SIZE 20
38
39/* Number of bytes to reseed after */
40#define REKEY_BYTES	(1 << 24)
41
42static int rc4_ready = 0;
43static RC4_KEY rc4;
44
45unsigned int arc4random(void)
46{
47	unsigned int r = 0;
48	static int first_time = 1;
49
50	if (rc4_ready <= 0) {
51		if (first_time)
52			seed_rng();
53		first_time = 0;
54		arc4random_stir();
55	}
56
57	RC4(&rc4, sizeof(r), (unsigned char *)&r, (unsigned char *)&r);
58
59	rc4_ready -= sizeof(r);
60
61	return(r);
62}
63
64void arc4random_stir(void)
65{
66	unsigned char rand_buf[SEED_SIZE];
67
68	memset(&rc4, 0, sizeof(rc4));
69	if (RAND_bytes(rand_buf, sizeof(rand_buf)) <= 0)
70		fatal("Couldn't obtain random bytes (error %ld)",
71		    ERR_get_error());
72	RC4_set_key(&rc4, sizeof(rand_buf), rand_buf);
73	RC4(&rc4, sizeof(rand_buf), rand_buf, rand_buf);
74	memset(rand_buf, 0, sizeof(rand_buf));
75
76	rc4_ready = REKEY_BYTES;
77}
78#endif /* !HAVE_ARC4RANDOM */
79