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bn_rand.c

/* crypto/bn/bn_rand.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */
/* ====================================================================
 * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include <stdio.h>
#include <time.h>
#include "cryptlib.h"
#include "bn_lcl.h"
#include <openssl/rand.h>

static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
      {
      unsigned char *buf=NULL;
      int ret=0,bit,bytes,mask;
      time_t tim;

      if (bits == 0)
            {
            BN_zero(rnd);
            return 1;
            }

      bytes=(bits+7)/8;
      bit=(bits-1)%8;
      mask=0xff<<(bit+1);

      buf=(unsigned char *)OPENSSL_malloc(bytes);
      if (buf == NULL)
            {
            BNerr(BN_F_BNRAND,ERR_R_MALLOC_FAILURE);
            goto err;
            }

      /* make a random number and set the top and bottom bits */
      time(&tim);
      RAND_add(&tim,sizeof(tim),0.0);

      if (pseudorand)
            {
            if (RAND_pseudo_bytes(buf, bytes) == -1)
                  goto err;
            }
      else
            {
            if (RAND_bytes(buf, bytes) <= 0)
                  goto err;
            }

#if 1
      if (pseudorand == 2)
            {
            /* generate patterns that are more likely to trigger BN
               library bugs */
            int i;
            unsigned char c;

            for (i = 0; i < bytes; i++)
                  {
                  RAND_pseudo_bytes(&c, 1);
                  if (c >= 128 && i > 0)
                        buf[i] = buf[i-1];
                  else if (c < 42)
                        buf[i] = 0;
                  else if (c < 84)
                        buf[i] = 255;
                  }
            }
#endif

      if (top != -1)
            {
            if (top)
                  {
                  if (bit == 0)
                        {
                        buf[0]=1;
                        buf[1]|=0x80;
                        }
                  else
                        {
                        buf[0]|=(3<<(bit-1));
                        }
                  }
            else
                  {
                  buf[0]|=(1<<bit);
                  }
            }
      buf[0] &= ~mask;
      if (bottom) /* set bottom bit if requested */
            buf[bytes-1]|=1;
      if (!BN_bin2bn(buf,bytes,rnd)) goto err;
      ret=1;
err:
      if (buf != NULL)
            {
            OPENSSL_cleanse(buf,bytes);
            OPENSSL_free(buf);
            }
      bn_check_top(rnd);
      return(ret);
      }

int     BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
      {
      return bnrand(0, rnd, bits, top, bottom);
      }

int     BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
      {
      return bnrand(1, rnd, bits, top, bottom);
      }

#if 1
int     BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
      {
      return bnrand(2, rnd, bits, top, bottom);
      }
#endif


/* random number r:  0 <= r < range */
static int bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
      {
      int (*bn_rand)(BIGNUM *, int, int, int) = pseudo ? BN_pseudo_rand : BN_rand;
      int n;
      int count = 100;

      if (range->neg || BN_is_zero(range))
            {
            BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
            return 0;
            }

      n = BN_num_bits(range); /* n > 0 */

      /* BN_is_bit_set(range, n - 1) always holds */

      if (n == 1)
            BN_zero(r);
      else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3))
            {
            /* range = 100..._2,
             * so  3*range (= 11..._2)  is exactly one bit longer than  range */
            do
                  {
                  if (!bn_rand(r, n + 1, -1, 0)) return 0;
                  /* If  r < 3*range,  use  r := r MOD range
                   * (which is either  r, r - range,  or  r - 2*range).
                   * Otherwise, iterate once more.
                   * Since  3*range = 11..._2, each iteration succeeds with
                   * probability >= .75. */
                  if (BN_cmp(r ,range) >= 0)
                        {
                        if (!BN_sub(r, r, range)) return 0;
                        if (BN_cmp(r, range) >= 0)
                              if (!BN_sub(r, r, range)) return 0;
                        }

                  if (!--count)
                        {
                        BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
                        return 0;
                        }
                  
                  }
            while (BN_cmp(r, range) >= 0);
            }
      else
            {
            do
                  {
                  /* range = 11..._2  or  range = 101..._2 */
                  if (!bn_rand(r, n, -1, 0)) return 0;

                  if (!--count)
                        {
                        BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
                        return 0;
                        }
                  }
            while (BN_cmp(r, range) >= 0);
            }

      bn_check_top(r);
      return 1;
      }


int   BN_rand_range(BIGNUM *r, const BIGNUM *range)
      {
      return bn_rand_range(0, r, range);
      }

int   BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
      {
      return bn_rand_range(1, r, range);
      }

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