crypto/bn/bn_rand.c

   1 /* crypto/bn/bn_rand.c */
   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 #define OPENSSL_FIPSAPI
 113
 114 #include <stdio.h>
 115 #include <time.h>
 116 #include "cryptlib.h"
 117 #include "bn_lcl.h"
 118 #include <openssl/rand.h>
 119 #include <openssl/sha.h>
 120
 121 static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
 122         {
 123         unsigned char *buf=NULL;
 124         int ret=0,bit,bytes,mask;
 125         time_t tim;
 126
 127         if (bits == 0)
 128                 {
 129                 BN_zero(rnd);
 130                 return 1;
 131                 }
 132
 133         bytes=(bits+7)/8;
 134         bit=(bits-1)%8;
 135         mask=0xff<<(bit+1);
 136
 137         buf=(unsigned char *)OPENSSL_malloc(bytes);
 138         if (buf == NULL)
 139                 {
 140                 BNerr(BN_F_BNRAND,ERR_R_MALLOC_FAILURE);
 141                 goto err;
 142                 }
 143
 144         /* make a random number and set the top and bottom bits */
 145         time(&tim);
 146         RAND_add(&tim,sizeof(tim),0.0);
 147
 148         if (pseudorand)
 149                 {
 150                 if (RAND_pseudo_bytes(buf, bytes) == -1)
 151                         goto err;
 152                 }
 153         else
 154                 {
 155                 if (RAND_bytes(buf, bytes) <= 0)
 156                         goto err;
 157                 }
 158
 159 #if 1
 160         if (pseudorand == 2)
 161                 {
 162                 /* generate patterns that are more likely to trigger BN
 163                    library bugs */
 164                 int i;
 165                 unsigned char c;
 166
 167                 for (i = 0; i < bytes; i++)
 168                         {
 169                         RAND_pseudo_bytes(&c, 1);
 170                         if (c >= 128 && i > 0)
 171                                 buf[i] = buf[i-1];
 172                         else if (c < 42)
 173                                 buf[i] = 0;
 174                         else if (c < 84)
 175                                 buf[i] = 255;
 176                         }
 177                 }
 178 #endif
 179
 180         if (top != -1)
 181                 {
 182                 if (top)
 183                         {
 184                         if (bit == 0)
 185                                 {
 186                                 buf[0]=1;
 187                                 buf[1]|=0x80;
 188                                 }
 189                         else
 190                                 {
 191                                 buf[0]|=(3<<(bit-1));
 192                                 }
 193                         }
 194                 else
 195                         {
 196                         buf[0]|=(1<<bit);
 197                         }
 198                 }
 199         buf[0] &= ~mask;
 200         if (bottom) /* set bottom bit if requested */
 201                 buf[bytes-1]|=1;
 202         if (!BN_bin2bn(buf,bytes,rnd)) goto err;
 203         ret=1;
 204 err:
 205         if (buf != NULL)
 206                 {
 207                 OPENSSL_cleanse(buf,bytes);
 208                 OPENSSL_free(buf);
 209                 }
 210         bn_check_top(rnd);
 211         return(ret);
 212         }
 213
 214 int     BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
 215         {
 216         return bnrand(0, rnd, bits, top, bottom);
 217         }
 218
 219 int     BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
 220         {
 221         return bnrand(1, rnd, bits, top, bottom);
 222         }
 223
 224 #if 1
 225 int     BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
 226         {
 227         return bnrand(2, rnd, bits, top, bottom);
 228         }
 229 #endif
 230
 231
 232 /* random number r:  0 <= r < range */
 233 static int bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
 234         {
 235         int (*bn_rand)(BIGNUM *, int, int, int) = pseudo ? BN_pseudo_rand : BN_rand;
 236         int n;
 237         int count = 100;
 238
 239         if (range->neg || BN_is_zero(range))
 240                 {
 241                 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
 242                 return 0;
 243                 }
 244
 245         n = BN_num_bits(range); /* n > 0 */
 246
 247         /* BN_is_bit_set(range, n - 1) always holds */
 248
 249         if (n == 1)
 250                 BN_zero(r);
 251 #ifdef OPENSSL_FIPS
 252         /* FIPS 186-3 is picky about how random numbers for keys etc are
 253          * generated. So we just use the second case which is equivalent to
 254          * "Generation by Testing Candidates" mentioned in B.1.2 et al.
 255          */
 256         else if (!FIPS_module_mode() && !BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3))
 257 #else
 258         else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3))
 259 #endif
 260                 {
 261                 /* range = 100..._2,
 262                  * so  3*range (= 11..._2)  is exactly one bit longer than  range */
 263                 do
 264                         {
 265                         if (!bn_rand(r, n + 1, -1, 0)) return 0;
 266                         /* If  r < 3*range,  use  r := r MOD range
 267                          * (which is either  r, r - range,  or  r - 2*range).
 268                          * Otherwise, iterate once more.
 269                          * Since  3*range = 11..._2, each iteration succeeds with
 270                          * probability >= .75. */
 271                         if (BN_cmp(r ,range) >= 0)
 272                                 {
 273                                 if (!BN_sub(r, r, range)) return 0;
 274                                 if (BN_cmp(r, range) >= 0)
 275                                         if (!BN_sub(r, r, range)) return 0;
 276                                 }
 277
 278                         if (!--count)
 279                                 {
 280                                 BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
 281                                 return 0;
 282                                 }
 283
 284                         }
 285                 while (BN_cmp(r, range) >= 0);
 286                 }
 287         else
 288                 {
 289                 do
 290                         {
 291                         /* range = 11..._2  or  range = 101..._2 */
 292                         if (!bn_rand(r, n, -1, 0)) return 0;
 293
 294                         if (!--count)
 295                                 {
 296                                 BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
 297                                 return 0;
 298                                 }
 299                         }
 300                 while (BN_cmp(r, range) >= 0);
 301                 }
 302
 303         bn_check_top(r);
 304         return 1;
 305         }
 306
 307
 308 int     BN_rand_range(BIGNUM *r, const BIGNUM *range)
 309         {
 310         return bn_rand_range(0, r, range);
 311         }
 312
 313 int     BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
 314         {
 315         return bn_rand_range(1, r, range);
 316         }
 317
 318 #ifndef OPENSSL_NO_SHA512
 319 /* BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
 320  * BN_rand_range, it also includes the contents of |priv| and |message| in the
 321  * generation so that an RNG failure isn't fatal as long as |priv| remains
 322  * secret. This is intended for use in DSA and ECDSA where an RNG weakness
 323  * leads directly to private key exposure unless this function is used. */
 324 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range, const BIGNUM* priv,
 325                           const unsigned char *message, size_t message_len,
 326                           BN_CTX *ctx)
 327         {
 328         SHA512_CTX sha;
 329         /* We use 512 bits of random data per iteration to
 330          * ensure that we have at least |range| bits of randomness. */
 331         unsigned char random_bytes[64];
 332         unsigned char digest[SHA512_DIGEST_LENGTH];
 333         unsigned done, todo;
 334         /* We generate |range|+8 bytes of random output. */
 335         const unsigned num_k_bytes = BN_num_bytes(range) + 8;
 336         unsigned char private_bytes[96];
 337         unsigned char *k_bytes;
 338         int ret = 0;
 339
 340         k_bytes = OPENSSL_malloc(num_k_bytes);
 341         if (!k_bytes)
 342                 goto err;
 343
 344         /* We copy |priv| into a local buffer to avoid exposing its length. */
 345         todo = sizeof(priv->d[0])*priv->top;
 346         if (todo > sizeof(private_bytes))
 347                 {
 348                 /* No reasonable DSA or ECDSA key should have a private key
 349                  * this large and we don't handle this case in order to avoid
 350                  * leaking the length of the private key. */
 351                 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
 352                 goto err;
 353                 }
 354         memcpy(private_bytes, priv->d, todo);
 355         memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
 356
 357         for (done = 0; done < num_k_bytes;) {
 358                 if (RAND_bytes(random_bytes, sizeof(random_bytes)) != 1)
 359                         goto err;
 360                 SHA512_Init(&sha);
 361                 SHA512_Update(&sha, &done, sizeof(done));
 362                 SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
 363                 SHA512_Update(&sha, message, message_len);
 364                 SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
 365                 SHA512_Final(digest, &sha);
 366
 367                 todo = num_k_bytes - done;
 368                 if (todo > SHA512_DIGEST_LENGTH)
 369                         todo = SHA512_DIGEST_LENGTH;
 370                 memcpy(k_bytes + done, digest, todo);
 371                 done += todo;
 372         }
 373
 374         if (!BN_bin2bn(k_bytes, num_k_bytes, out))
 375                 goto err;
 376         if (BN_mod(out, out, range, ctx) != 1)
 377                 goto err;
 378         ret = 1;
 379
 380 err:
 381         if (k_bytes)
 382                 OPENSSL_free(k_bytes);
 383         return ret;
 384         }
 385 #endif  /* OPENSSL_NO_SHA512 */