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) 82 void 83 ub_systemseed(unsigned int ATTR_UNUSED(seed)) 84 { 85 /* arc4random_uniform does not need seeds, it gets kernel entropy */ 86 } 87 88 struct ub_randstate* 89 ub_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 } 99 100 long int 101 ub_random(struct ub_randstate* ATTR_UNUSED(s)) 102 { 103 /* This relies on MAX_VALUE being 0x7fffffff. */ 104 return (long)arc4random() & MAX_VALUE; 105 } 106 107 long int 108 ub_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 */ 118 struct ub_randstate { 119 int ready; 120 }; 121 122 void ub_systemseed(unsigned int ATTR_UNUSED(seed)) 123 { 124 } 125 126 struct 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 } 136 137 long 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 */ 155 struct ub_randstate { 156 struct yarrow256_ctx ctx; 157 int seeded; 158 }; 159 160 void 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 } 168 169 struct 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 } 199 200 long 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) 215 long int 216 ub_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 */ 227 228 void 229 ub_randfree(struct ub_randstate* s) 230 { 231 if(s) 232 free(s); 233 /* user app must do RAND_cleanup(); */ 234 } 235