random.c revision 356345 
1/*
2 * util/random.c - thread safe random generator, which is reasonably secure.
3 *
4 * Copyright (c) 2007, NLnet Labs. All rights reserved.
5 *
6 * This software is open source.
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 *
12 * Redistributions of source code must retain the above copyright notice,
13 * this list of conditions and the following disclaimer.
14 *
15 * Redistributions in binary form must reproduce the above copyright notice,
16 * this list of conditions and the following disclaimer in the documentation
17 * and/or other materials provided with the distribution.
18 *
19 * Neither the name of the NLNET LABS nor the names of its contributors may
20 * be used to endorse or promote products derived from this software without
21 * specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
26 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
27 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
29 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
30 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
31 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
32 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
33 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35
36/**
37 * \file
38 * Thread safe random functions. Similar to arc4random() with an explicit
39 * initialisation routine.
40 *
41 * The code in this file is based on arc4random from
42 * openssh-4.0p1/openbsd-compat/bsd-arc4random.c
43 * That code is also BSD licensed. Here is their statement:
44 *
45 * Copyright (c) 1996, David Mazieres <dm@uun.org>
46 * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
47 *
48 * Permission to use, copy, modify, and distribute this software for any
49 * purpose with or without fee is hereby granted, provided that the above
50 * copyright notice and this permission notice appear in all copies.
51 *
52 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
53 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
54 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
55 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
56 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
57 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
58 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
59 */
60#include "config.h"
61#include "util/random.h"
62#include "util/log.h"
63#include <time.h>
64
65#ifdef HAVE_NSS
66/* nspr4 */
67#include "prerror.h"
68/* nss3 */
69#include "secport.h"
70#include "pk11pub.h"
71#elif defined(HAVE_NETTLE)
72#include "yarrow.h"
73#endif
74
75/**
76 * Max random value.  Similar to RAND_MAX, but more portable
77 * (mingw uses only 15 bits random).
78 */
79#define MAX_VALUE 0x7fffffff
80
81#if defined(HAVE_SSL)
82struct ub_randstate*
83ub_initstate(struct ub_randstate* ATTR_UNUSED(from))
84{
85	struct ub_randstate* s = (struct ub_randstate*)malloc(1);
86	if(!s) {
87		log_err("malloc failure in random init");
88		return NULL;
89	}
90	return s;
91}
92
93long int
94ub_random(struct ub_randstate* ATTR_UNUSED(s))
95{
96	/* This relies on MAX_VALUE being 0x7fffffff. */
97	return (long)arc4random() & MAX_VALUE;
98}
99
100long int
101ub_random_max(struct ub_randstate* state, long int x)
102{
103	(void)state;
104	/* on OpenBSD, this does not need _seed(), or _stir() calls */
105	return (long)arc4random_uniform((uint32_t)x);
106}
107
108#elif defined(HAVE_NSS)
109
110/* not much to remember for NSS since we use its pk11_random, placeholder */
111struct ub_randstate {
112	int ready;
113};
114
115struct ub_randstate* ub_initstate(struct ub_randstate* ATTR_UNUSED(from))
116{
117	struct ub_randstate* s = (struct ub_randstate*)calloc(1, sizeof(*s));
118	if(!s) {
119		log_err("malloc failure in random init");
120		return NULL;
121	}
122	return s;
123}
124
125long int ub_random(struct ub_randstate* ATTR_UNUSED(state))
126{
127	long int x;
128	/* random 31 bit value. */
129	SECStatus s = PK11_GenerateRandom((unsigned char*)&x, (int)sizeof(x));
130	if(s != SECSuccess) {
131		/* unbound needs secure randomness for randomized
132		 * ID bits and port numbers in packets to upstream servers */
133		fatal_exit("PK11_GenerateRandom error: %s",
134			PORT_ErrorToString(PORT_GetError()));
135	}
136	return x & MAX_VALUE;
137}
138
139#elif defined(HAVE_NETTLE)
140
141/**
142 * libnettle implements a Yarrow-256 generator (SHA256 + AES),
143 * and we have to ensure it is seeded before use.
144 */
145struct ub_randstate {
146	struct yarrow256_ctx ctx;
147	int seeded;
148};
149
150struct ub_randstate* ub_initstate(struct ub_randstate* ATTR_UNUSED(from))
151{
152	struct ub_randstate* s = (struct ub_randstate*)calloc(1, sizeof(*s));
153	uint8_t buf[YARROW256_SEED_FILE_SIZE];
154	if(!s) {
155		log_err("malloc failure in random init");
156		return NULL;
157	}
158	/* Setup Yarrow context */
159	yarrow256_init(&s->ctx, 0, NULL);
160
161	if(getentropy(buf, sizeof(buf)) != -1) {
162		/* got entropy */
163		yarrow256_seed(&s->ctx, YARROW256_SEED_FILE_SIZE, buf);
164		s->seeded = yarrow256_is_seeded(&s->ctx);
165	} else {
166		log_err("nettle random(yarrow) cannot initialize, "
167			"getentropy failed: %s", strerror(errno));
168		free(s);
169		return NULL;
170	}
171
172	return s;
173}
174
175long int ub_random(struct ub_randstate* s)
176{
177	/* random 31 bit value. */
178	long int x = 0;
179	if (!s || !s->seeded) {
180		log_err("Couldn't generate randomness, Yarrow-256 generator not yet seeded");
181	} else {
182		yarrow256_random(&s->ctx, sizeof(x), (uint8_t *)&x);
183	}
184	return x & MAX_VALUE;
185}
186#endif /* HAVE_SSL or HAVE_NSS or HAVE_NETTLE */
187
188
189#if defined(HAVE_NSS) || defined(HAVE_NETTLE)
190long int
191ub_random_max(struct ub_randstate* state, long int x)
192{
193	/* make sure we fetch in a range that is divisible by x. ignore
194	 * values from d .. MAX_VALUE, instead draw a new number */
195	long int d = MAX_VALUE - (MAX_VALUE % x); /* d is divisible by x */
196	long int v = ub_random(state);
197	while(d <= v)
198		v = ub_random(state);
199	return (v % x);
200}
201#endif /* HAVE_NSS or HAVE_NETTLE */
202
203void
204ub_randfree(struct ub_randstate* s)
205{
206	free(s);
207	/* user app must do RAND_cleanup(); */
208}
209