crypto/libressl/crypto/bn/bn_rand.c

   1 /* $OpenBSD: bn_rand.c,v 1.17 2015/02/19 06:10:29 jsing Exp $ */
   2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58 /* ====================================================================
  59  * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.
  60  *
  61  * Redistribution and use in source and binary forms, with or without
  62  * modification, are permitted provided that the following conditions
  63  * are met:
  64  *
  65  * 1. Redistributions of source code must retain the above copyright
  66  *    notice, this list of conditions and the following disclaimer.
  67  *
  68  * 2. Redistributions in binary form must reproduce the above copyright
  69  *    notice, this list of conditions and the following disclaimer in
  70  *    the documentation and/or other materials provided with the
  71  *    distribution.
  72  *
  73  * 3. All advertising materials mentioning features or use of this
  74  *    software must display the following acknowledgment:
  75  *    "This product includes software developed by the OpenSSL Project
  76  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  77  *
  78  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  79  *    endorse or promote products derived from this software without
  80  *    prior written permission. For written permission, please contact
  81  *    openssl-core@openssl.org.
  82  *
  83  * 5. Products derived from this software may not be called "OpenSSL"
  84  *    nor may "OpenSSL" appear in their names without prior written
  85  *    permission of the OpenSSL Project.
  86  *
  87  * 6. Redistributions of any form whatsoever must retain the following
  88  *    acknowledgment:
  89  *    "This product includes software developed by the OpenSSL Project
  90  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  91  *
  92  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  93  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  94  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  95  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  96  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  97  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  98  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  99  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 100  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 101  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 102  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 103  * OF THE POSSIBILITY OF SUCH DAMAGE.
 104  * ====================================================================
 105  *
 106  * This product includes cryptographic software written by Eric Young
 107  * (eay@cryptsoft.com).  This product includes software written by Tim
 108  * Hudson (tjh@cryptsoft.com).
 109  *
 110  */
 111
 112 #include <stdio.h>
 113 #include <stdlib.h>
 114 #include <string.h>
 115 #include <time.h>
 116
 117 #include <openssl/err.h>
 118
 119 #include "bn_lcl.h"
 120
 121 static int
 122 bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
 123 {
 124         unsigned char *buf = NULL;
 125         int ret = 0, bit, bytes, mask;
 126
 127         if (rnd == NULL) {
 128                 BNerr(BN_F_BNRAND, ERR_R_PASSED_NULL_PARAMETER);
 129                 return (0);
 130         }
 131
 132         if (bits == 0) {
 133                 BN_zero(rnd);
 134                 return (1);
 135         }
 136
 137         bytes = (bits + 7) / 8;
 138         bit = (bits - 1) % 8;
 139         mask = 0xff << (bit + 1);
 140
 141         buf = malloc(bytes);
 142         if (buf == NULL) {
 143                 BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
 144                 goto err;
 145         }
 146
 147         /* make a random number and set the top and bottom bits */
 148         arc4random_buf(buf, bytes);
 149
 150 #if 1
 151         if (pseudorand == 2) {
 152                 /* generate patterns that are more likely to trigger BN
 153                    library bugs */
 154                 int i;
 155                 unsigned char c;
 156
 157                 for (i = 0; i < bytes; i++) {
 158                         arc4random_buf(&c, 1);
 159                         if (c >= 128 && i > 0)
 160                                 buf[i] = buf[i - 1];
 161                         else if (c < 42)
 162                                 buf[i] = 0;
 163                         else if (c < 84)
 164                                 buf[i] = 255;
 165                 }
 166         }
 167 #endif
 168
 169         if (top != -1) {
 170                 if (top) {
 171                         if (bit == 0) {
 172                                 buf[0] = 1;
 173                                 buf[1] |= 0x80;
 174                         } else {
 175                                 buf[0] |= (3 << (bit - 1));
 176                         }
 177                 } else {
 178                         buf[0] |= (1 << bit);
 179                 }
 180         }
 181         buf[0] &= ~mask;
 182         if (bottom) /* set bottom bit if requested */
 183                 buf[bytes - 1] |= 1;
 184         if (BN_bin2bn(buf, bytes, rnd) == NULL)
 185                 goto err;
 186         ret = 1;
 187
 188 err:
 189         if (buf != NULL) {
 190                 explicit_bzero(buf, bytes);
 191                 free(buf);
 192         }
 193         bn_check_top(rnd);
 194         return (ret);
 195 }
 196
 197 int
 198 BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
 199 {
 200         return bnrand(0, rnd, bits, top, bottom);
 201 }
 202
 203 int
 204 BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
 205 {
 206         return bnrand(1, rnd, bits, top, bottom);
 207 }
 208
 209 #if 1
 210 int
 211 BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
 212 {
 213         return bnrand(2, rnd, bits, top, bottom);
 214 }
 215 #endif
 216
 217
 218 /* random number r:  0 <= r < range */
 219 static int
 220 bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
 221 {
 222         int (*bn_rand)(BIGNUM *, int, int, int) = pseudo ? BN_pseudo_rand : BN_rand;
 223         int n;
 224         int count = 100;
 225
 226         if (range->neg || BN_is_zero(range)) {
 227                 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
 228                 return 0;
 229         }
 230
 231         n = BN_num_bits(range); /* n > 0 */
 232
 233         /* BN_is_bit_set(range, n - 1) always holds */
 234
 235         if (n == 1)
 236                 BN_zero(r);
 237         else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
 238                 /* range = 100..._2,
 239                  * so  3*range (= 11..._2)  is exactly one bit longer than  range */
 240                 do {
 241                         if (!bn_rand(r, n + 1, -1, 0))
 242                                 return 0;
 243                         /* If  r < 3*range,  use  r := r MOD range
 244                          * (which is either  r, r - range,  or  r - 2*range).
 245                          * Otherwise, iterate once more.
 246                          * Since  3*range = 11..._2, each iteration succeeds with
 247                          * probability >= .75. */
 248                         if (BN_cmp(r, range) >= 0) {
 249                                 if (!BN_sub(r, r, range))
 250                                         return 0;
 251                                 if (BN_cmp(r, range) >= 0)
 252                                         if (!BN_sub(r, r, range))
 253                                                 return 0;
 254                         }
 255
 256                         if (!--count) {
 257                                 BNerr(BN_F_BN_RAND_RANGE,
 258                                     BN_R_TOO_MANY_ITERATIONS);
 259                                 return 0;
 260                         }
 261
 262                 } while (BN_cmp(r, range) >= 0);
 263         } else {
 264                 do {
 265                         /* range = 11..._2  or  range = 101..._2 */
 266                         if (!bn_rand(r, n, -1, 0))
 267                                 return 0;
 268
 269                         if (!--count) {
 270                                 BNerr(BN_F_BN_RAND_RANGE,
 271                                     BN_R_TOO_MANY_ITERATIONS);
 272                                 return 0;
 273                         }
 274                 } while (BN_cmp(r, range) >= 0);
 275         }
 276
 277         bn_check_top(r);
 278         return 1;
 279 }
 280
 281 int
 282 BN_rand_range(BIGNUM *r, const BIGNUM *range)
 283 {
 284         return bn_rand_range(0, r, range);
 285 }
 286
 287 int
 288 BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
 289 {
 290         return bn_rand_range(1, r, range);
 291 }