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 #include <stdio.h>
  60 #include <time.h>
  61 #include "cryptlib.h"
  62 #include "bn_lcl.h"
  63 #include <openssl/rand.h>
  64
  65 static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
  66         {
  67         unsigned char *buf=NULL;
  68         int ret=0,bit,bytes,mask;
  69         time_t tim;
  70
  71         if (bits == 0)
  72                 {
  73                 BN_zero(rnd);
  74                 return 1;
  75                 }
  76
  77         bytes=(bits+7)/8;
  78         bit=(bits-1)%8;
  79         mask=0xff<<bit;
  80
  81         buf=(unsigned char *)OPENSSL_malloc(bytes);
  82         if (buf == NULL)
  83                 {
  84                 BNerr(BN_F_BN_RAND,ERR_R_MALLOC_FAILURE);
  85                 goto err;
  86                 }
  87
  88         /* make a random number and set the top and bottom bits */
  89         time(&tim);
  90         RAND_add(&tim,sizeof(tim),0);
  91
  92         if (pseudorand)
  93                 {
  94                 if (RAND_pseudo_bytes(buf, bytes) == -1)
  95                         goto err;
  96                 }
  97         else
  98                 {
  99                 if (RAND_bytes(buf, bytes) <= 0)
 100                         goto err;
 101                 }
 102
 103 #if 1
 104         if (pseudorand == 2)
 105                 {
 106                 /* generate patterns that are more likely to trigger BN
 107                    library bugs */
 108                 int i;
 109                 unsigned char c;
 110
 111                 for (i = 0; i < bytes; i++)
 112                         {
 113                         RAND_pseudo_bytes(&c, 1);
 114                         if (c >= 128 && i > 0)
 115                                 buf[i] = buf[i-1];
 116                         else if (c < 42)
 117                                 buf[i] = 0;
 118                         else if (c < 84)
 119                                 buf[i] = 255;
 120                         }
 121                 }
 122 #endif
 123
 124         if (top)
 125                 {
 126                 if (bit == 0)
 127                         {
 128                         buf[0]=1;
 129                         buf[1]|=0x80;
 130                         }
 131                 else
 132                         {
 133                         buf[0]|=(3<<(bit-1));
 134                         buf[0]&= ~(mask<<1);
 135                         }
 136                 }
 137         else
 138                 {
 139                 buf[0]|=(1<<bit);
 140                 buf[0]&= ~(mask<<1);
 141                 }
 142         if (bottom) /* set bottom bits to whatever odd is */
 143                 buf[bytes-1]|=1;
 144         if (!BN_bin2bn(buf,bytes,rnd)) goto err;
 145         ret=1;
 146 err:
 147         if (buf != NULL)
 148                 {
 149                 memset(buf,0,bytes);
 150                 OPENSSL_free(buf);
 151                 }
 152         return(ret);
 153         }
 154
 155 int     BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
 156         {
 157         return bnrand(0, rnd, bits, top, bottom);
 158         }
 159
 160 int     BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
 161         {
 162         return bnrand(1, rnd, bits, top, bottom);
 163         }
 164
 165 #if 1
 166 int     BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
 167         {
 168         return bnrand(2, rnd, bits, top, bottom);
 169         }
 170 #endif
 171
 172 /* random number r: min <= r < min+range */
 173 int     BN_rand_range(BIGNUM *r, BIGNUM *min, BIGNUM *range)
 174         {
 175         int n;
 176
 177         if (range->neg || BN_is_zero(range))
 178                 {
 179                 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
 180                 return 0;
 181                 }
 182
 183         n = BN_num_bits(range); /* n > 0 */
 184
 185         if (n == 1)
 186                 {
 187                 if (!BN_zero(r)) return 0;
 188                 }
 189         else if (BN_is_bit_set(range, n - 2))
 190                 {
 191                 do
 192                         {
 193                         /* range = 11..._2, so each iteration succeeds with probability > .75 */
 194                         if (!BN_rand(r, n, 0, 0)) return 0;
 195                         }
 196                 while (BN_cmp(r, range) >= 0);
 197                 }
 198         else
 199                 {
 200                 /* range = 10..._2,
 201                  * so  3*range (= 11..._2)  is exactly one bit longer than  range */
 202                 do
 203                         {
 204                         if (!BN_rand(r, n + 1, 0, 0)) return 0;
 205                         /* If  r < 3*range,  use  r := r MOD range
 206                          * (which is either  r, r - range,  or  r - 2*range).
 207                          * Otherwise, iterate once more.
 208                          * Since  3*range = 11..._2, each iteration succeeds with
 209                          * probability > .75. */
 210                         if (BN_cmp(r ,range) >= 0)
 211                                 {
 212                                 if (!BN_sub(r, r, range)) return 0;
 213                                 if (BN_cmp(r, range) >= 0)
 214                                         if (!BN_sub(r, r, range)) return 0;
 215                                 }
 216                         }
 217                 while (BN_cmp(r, range) >= 0);
 218                 }
 219
 220         if (min != NULL)
 221                 {
 222                 if (!BN_add(r, r, min)) return 0;
 223                 }
 224
 225         return 1;
 226         }