/* $OpenBSD: bn_rand.c,v 1.25 2021/08/31 11:19:19 tb Exp $ */

/* 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 <stdlib.h>

#include <string.h>

#include <time.h>

#include <openssl/err.h>

#include "bn_lcl.h"

static int

bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)

{

  unsigned char *buf = NULL;

  int ret = 0, bit, bytes, mask;

  if (rnd == NULL) {

    BNerror(ERR_R_PASSED_NULL_PARAMETER);

    return (0);

  }

  if (bits < 0 || (bits == 1 && top > 0)) {

    BNerror(BN_R_BITS_TOO_SMALL);

    return (0);

  }

  if (bits == 0) {

    BN_zero(rnd);

    return (1);

  }

  bytes = (bits + 7) / 8;

  bit = (bits - 1) % 8;

  mask = 0xff << (bit + 1);

  buf = malloc(bytes);

  if (buf == NULL) {

    BNerror(ERR_R_MALLOC_FAILURE);

    goto err;

  }

  /* make a random number and set the top and bottom bits */

  arc4random_buf(buf, bytes);

#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++) {

      arc4random_buf(&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 > 0) {

    if (bit == 0) {

      buf[0] = 1;

      buf[1] |= 0x80;

    } else {

      buf[0] |= (3 << (bit - 1));

    }

  }

  if (top == 0)

    buf[0] |= (1 << bit);

  buf[0] &= ~mask;

  if (bottom) /* set bottom bit if requested */

    buf[bytes - 1] |= 1;

  if (BN_bin2bn(buf, bytes, rnd) == NULL)

    goto err;

  ret = 1;

err:

  freezero(buf, bytes);

  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)) {

    BNerror(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) {

        BNerror(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) {

        BNerror(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_rand_interval(BIGNUM *rnd, const BIGNUM *lower_inc, const BIGNUM *upper_exc)

{

  BIGNUM *len = NULL;

  int ret = 0;

  if (BN_cmp(lower_inc, upper_exc) >= 0)

    goto err;

  if ((len = BN_new()) == NULL)

    goto err;

  if (!BN_sub(len, upper_exc, lower_inc))

    goto err;

  if (!bn_rand_range(0, rnd, len))

    goto err;

  if (!BN_add(rnd, rnd, lower_inc))

    goto err;

  ret = 1;

 err:

  BN_free(len);

  return ret;

}

int

BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)

{

  return bn_rand_range(1, r, range);

}