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