random.c revision 302408 
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)
82void
83ub_systemseed(unsigned int ATTR_UNUSED(seed))
84{
85	/* arc4random_uniform does not need seeds, it gets kernel entropy */
86}
87
88struct ub_randstate*
89ub_initstate(unsigned int ATTR_UNUSED(seed),
90	struct ub_randstate* ATTR_UNUSED(from))
91{
92	struct ub_randstate* s = (struct ub_randstate*)malloc(1);
93	if(!s) {
94		log_err("malloc failure in random init");
95		return NULL;
96	}
97	return s;
98}
99
100long int
101ub_random(struct ub_randstate* ATTR_UNUSED(s))
102{
103	/* This relies on MAX_VALUE being 0x7fffffff. */
104	return (long)arc4random() & MAX_VALUE;
105}
106
107long int
108ub_random_max(struct ub_randstate* state, long int x)
109{
110	(void)state;
111	/* on OpenBSD, this does not need _seed(), or _stir() calls */
112	return (long)arc4random_uniform((uint32_t)x);
113}
114
115#elif defined(HAVE_NSS)
116
117/* not much to remember for NSS since we use its pk11_random, placeholder */
118struct ub_randstate {
119	int ready;
120};
121
122void ub_systemseed(unsigned int ATTR_UNUSED(seed))
123{
124}
125
126struct ub_randstate* ub_initstate(unsigned int ATTR_UNUSED(seed),
127	struct ub_randstate* ATTR_UNUSED(from))
128{
129	struct ub_randstate* s = (struct ub_randstate*)calloc(1, sizeof(*s));
130	if(!s) {
131		log_err("malloc failure in random init");
132		return NULL;
133	}
134	return s;
135}
136
137long int ub_random(struct ub_randstate* ATTR_UNUSED(state))
138{
139	long int x;
140	/* random 31 bit value. */
141	SECStatus s = PK11_GenerateRandom((unsigned char*)&x, (int)sizeof(x));
142	if(s != SECSuccess) {
143		log_err("PK11_GenerateRandom error: %s",
144			PORT_ErrorToString(PORT_GetError()));
145	}
146	return x & MAX_VALUE;
147}
148
149#elif defined(HAVE_NETTLE)
150
151/**
152 * libnettle implements a Yarrow-256 generator (SHA256 + AES),
153 * and we have to ensure it is seeded before use.
154 */
155struct ub_randstate {
156	struct yarrow256_ctx ctx;
157	int seeded;
158};
159
160void ub_systemseed(unsigned int ATTR_UNUSED(seed))
161{
162/**
163 * We seed on init and not here, as we need the ctx to re-seed.
164 * This also means that re-seeding is not supported.
165 */
166	log_err("Re-seeding not supported, generator untouched");
167}
168
169struct ub_randstate* ub_initstate(unsigned int seed,
170	struct ub_randstate* ATTR_UNUSED(from))
171{
172	struct ub_randstate* s = (struct ub_randstate*)calloc(1, sizeof(*s));
173	uint8_t buf[YARROW256_SEED_FILE_SIZE];
174	if(!s) {
175		log_err("malloc failure in random init");
176		return NULL;
177	}
178	/* Setup Yarrow context */
179	yarrow256_init(&s->ctx, 0, NULL);
180
181	if(getentropy(buf, sizeof(buf)) != -1) {
182		/* got entropy */
183		yarrow256_seed(&s->ctx, YARROW256_SEED_FILE_SIZE, buf);
184		s->seeded = yarrow256_is_seeded(&s->ctx);
185	} else {
186		/* Stretch the uint32 input seed and feed it to Yarrow */
187		uint32_t v = seed;
188		size_t i;
189		for(i=0; i < (YARROW256_SEED_FILE_SIZE/sizeof(seed)); i++) {
190			memmove(buf+i*sizeof(seed), &v, sizeof(seed));
191			v = v*seed + (uint32_t)i;
192		}
193		yarrow256_seed(&s->ctx, YARROW256_SEED_FILE_SIZE, buf);
194		s->seeded = yarrow256_is_seeded(&s->ctx);
195	}
196
197	return s;
198}
199
200long int ub_random(struct ub_randstate* s)
201{
202	/* random 31 bit value. */
203	long int x = 0;
204	if (!s || !s->seeded) {
205		log_err("Couldn't generate randomness, Yarrow-256 generator not yet seeded");
206	} else {
207		yarrow256_random(&s->ctx, sizeof(x), (uint8_t *)&x);
208	}
209	return x & MAX_VALUE;
210}
211#endif /* HAVE_SSL or HAVE_NSS or HAVE_NETTLE */
212
213
214#if defined(HAVE_NSS) || defined(HAVE_NETTLE)
215long int
216ub_random_max(struct ub_randstate* state, long int x)
217{
218	/* make sure we fetch in a range that is divisible by x. ignore
219	 * values from d .. MAX_VALUE, instead draw a new number */
220	long int d = MAX_VALUE - (MAX_VALUE % x); /* d is divisible by x */
221	long int v = ub_random(state);
222	while(d <= v)
223		v = ub_random(state);
224	return (v % x);
225}
226#endif /* HAVE_NSS or HAVE_NETTLE */
227
228void
229ub_randfree(struct ub_randstate* s)
230{
231	free(s);
232	/* user app must do RAND_cleanup(); */
233}
234