text: /* 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 <openssl/bn.h>
  
  #include <limits.h>
  #include <string.h>
  
  #include <openssl/err.h>
  #include <openssl/rand.h>
  #include <openssl/type_check.h>
  
  #include "internal.h"
  #include "../../internal.h"
  #include "../rand/internal.h"
  
  
  int BN_rand(BIGNUM *rnd, int bits, int top, int bottom) {
    if (rnd == NULL) {
      return 0;
    }
  
    if (top != BN_RAND_TOP_ANY && top != BN_RAND_TOP_ONE &&
        top != BN_RAND_TOP_TWO) {
      OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
      return 0;
    }
  
    if (bottom != BN_RAND_BOTTOM_ANY && bottom != BN_RAND_BOTTOM_ODD) {
      OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
      return 0;
    }
  
    if (bits == 0) {
      BN_zero(rnd);
      return 1;
    }
  
    if (bits > INT_MAX - (BN_BITS2 - 1)) {
      OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);
      return 0;
    }
  
    int words = (bits + BN_BITS2 - 1) / BN_BITS2;
    int bit = (bits - 1) % BN_BITS2;
    const BN_ULONG kOne = 1;
    const BN_ULONG kThree = 3;
    BN_ULONG mask = bit < BN_BITS2 - 1 ? (kOne << (bit + 1)) - 1 : BN_MASK2;
    if (!bn_wexpand(rnd, words)) {
      return 0;
    }
  
    // |RAND_bytes| calls within the fipsmodule should be wrapped with state lock
    // functions to avoid updating the service indicator with the DRBG functions.
    FIPS_service_indicator_lock_state();
    RAND_bytes((uint8_t *)rnd->d, words * sizeof(BN_ULONG));
    FIPS_service_indicator_unlock_state();
  
    rnd->d[words - 1] &= mask;
    if (top != BN_RAND_TOP_ANY) {
      if (top == BN_RAND_TOP_TWO && bits > 1) {
        if (bit == 0) {
          rnd->d[words - 1] |= 1;
          rnd->d[words - 2] |= kOne << (BN_BITS2 - 1);
        } else {
          rnd->d[words - 1] |= kThree << (bit - 1);
        }
      } else {
        rnd->d[words - 1] |= kOne << bit;
      }
    }
    if (bottom == BN_RAND_BOTTOM_ODD) {
      rnd->d[0] |= 1;
    }
  
    rnd->neg = 0;
    rnd->width = words;
    return 1;
  }
  
  int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom) {
    return BN_rand(rnd, bits, top, bottom);
  }
  
  // bn_less_than_word_mask returns a mask of all ones if the number represented
  // by |len| words at |a| is less than |b| and zero otherwise. It performs this
  // computation in time independent of the value of |a|. |b| is assumed public.
  static crypto_word_t bn_less_than_word_mask(const BN_ULONG *a, size_t len,
                                              BN_ULONG b) {
    if (b == 0) {
      return CONSTTIME_FALSE_W;
    }
    if (len == 0) {
      return CONSTTIME_TRUE_W;
    }
  
    // |a| < |b| iff a[1..len-1] are all zero and a[0] < b.
    OPENSSL_STATIC_ASSERT(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
                          crypto_word_t_is_too_small)
    crypto_word_t mask = 0;
    for (size_t i = 1; i < len; i++) {
      mask |= a[i];
    }
    // |mask| is now zero iff a[1..len-1] are all zero.
    mask = constant_time_is_zero_w(mask);
    mask &= constant_time_lt_w(a[0], b);
    return mask;
  }
  
  int bn_in_range_words(const BN_ULONG *a, BN_ULONG min_inclusive,
                        const BN_ULONG *max_exclusive, size_t len) {
    crypto_word_t mask = ~bn_less_than_word_mask(a, len, min_inclusive);
    return mask & bn_less_than_words(a, max_exclusive, len);
  }
  
  static int bn_range_to_mask(size_t *out_words, BN_ULONG *out_mask,
                              size_t min_inclusive, const BN_ULONG *max_exclusive,
                              size_t len) {
    // The magnitude of |max_exclusive| is assumed public.
    size_t words = len;
    while (words > 0 && max_exclusive[words - 1] == 0) {
      words--;
    }
    if (words == 0 ||
        (words == 1 && max_exclusive[0] <= min_inclusive)) {
      OPENSSL_PUT_ERROR(BN, BN_R_INVALID_RANGE);
      return 0;
    }
    BN_ULONG mask = max_exclusive[words - 1];
    // This sets all bits in |mask| below the most significant bit.
    mask |= mask >> 1;
    mask |= mask >> 2;
    mask |= mask >> 4;
    mask |= mask >> 8;
    mask |= mask >> 16;
  #if defined(OPENSSL_64_BIT)
    mask |= mask >> 32;
  #endif
  
    *out_words = words;
    *out_mask = mask;
    return 1;
  }
  
  int bn_rand_range_words(BN_ULONG *out, BN_ULONG min_inclusive,
                          const BN_ULONG *max_exclusive, size_t len,
                          const uint8_t additional_data[32]) {
    // This function implements the equivalent of steps 4 through 7 of FIPS 186-4
    // appendices B.4.2 and B.5.2. When called in those contexts, |max_exclusive|
    // is n and |min_inclusive| is one.
  
    // |RAND_bytes| calls within the fipsmodule should be wrapped with state lock
    // functions to avoid updating the service indicator with the DRBG functions.
    FIPS_service_indicator_lock_state();
    int ret = 0;
  
    // Compute the bit length of |max_exclusive| (step 1), in terms of a number of
    // |words| worth of entropy to fill and a mask of bits to clear in the top
    // word.
    size_t words;
    BN_ULONG mask;
    if (!bn_range_to_mask(&words, &mask, min_inclusive, max_exclusive, len)) {
      goto end;
    }
  
    // Fill any unused words with zero.
    OPENSSL_memset(out + words, 0, (len - words) * sizeof(BN_ULONG));
  
    unsigned count = 100;
    do {
      if (!--count) {
        OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_ITERATIONS);
        goto end;
      }
  
      // Steps 4 and 5. Use |words| and |mask| together to obtain a string of N
      // bits, where N is the bit length of |max_exclusive|.
      RAND_bytes_with_additional_data((uint8_t *)out, words * sizeof(BN_ULONG),
                                      additional_data);
      out[words - 1] &= mask;
  
      // If out >= max_exclusive or out < min_inclusive, retry. This implements
      // the equivalent of steps 6 and 7 without leaking the value of |out|.
    } while (!bn_in_range_words(out, min_inclusive, max_exclusive, words));
  
    ret = 1;
  
  end:
    FIPS_service_indicator_unlock_state();
    return ret;
  }
  
  int BN_rand_range_ex(BIGNUM *r, BN_ULONG min_inclusive,
                       const BIGNUM *max_exclusive) {
    static const uint8_t kDefaultAdditionalData[32] = {0};
    if (!bn_wexpand(r, max_exclusive->width) ||
        !bn_rand_range_words(r->d, min_inclusive, max_exclusive->d,
                             max_exclusive->width, kDefaultAdditionalData)) {
      return 0;
    }
  
    r->neg = 0;
    r->width = max_exclusive->width;
    return 1;
  }
  
  int bn_rand_secret_range(BIGNUM *r, int *out_is_uniform, BN_ULONG min_inclusive,
                           const BIGNUM *max_exclusive) {
    // |RAND_bytes| calls within the fipsmodule should be wrapped with state lock
    // functions to avoid updating the service indicator with the DRBG functions.
    FIPS_service_indicator_lock_state();
    int ret = 0;
  
    size_t words;
    BN_ULONG mask;
    if (!bn_range_to_mask(&words, &mask, min_inclusive, max_exclusive->d,
                          max_exclusive->width) ||
        !bn_wexpand(r, words)) {
      goto end;
    }
  
    assert(words > 0);
    assert(mask != 0);
    // The range must be large enough for bit tricks to fix invalid values.
    if (words == 1 && min_inclusive > mask >> 1) {
      OPENSSL_PUT_ERROR(BN, BN_R_INVALID_RANGE);
      goto end;
    }
  
    // Select a uniform random number with num_bits(max_exclusive) bits.
    RAND_bytes((uint8_t *)r->d, words * sizeof(BN_ULONG));
    r->d[words - 1] &= mask;
  
    // Check, in constant-time, if the value is in range.
    *out_is_uniform =
        bn_in_range_words(r->d, min_inclusive, max_exclusive->d, words);
    crypto_word_t in_range = *out_is_uniform;
    in_range = 0 - in_range;
  
    // If the value is not in range, force it to be in range.
    r->d[0] |= constant_time_select_w(in_range, 0, min_inclusive);
    r->d[words - 1] &= constant_time_select_w(in_range, BN_MASK2, mask >> 1);
    assert(bn_in_range_words(r->d, min_inclusive, max_exclusive->d, words));
  
    r->neg = 0;
    r->width = words;
    ret = 1;
  
  end:
    FIPS_service_indicator_unlock_state();
    return ret;
  }
  
  int BN_rand_range(BIGNUM *r, const BIGNUM *range) {
    return BN_rand_range_ex(r, 0, range);
  }
  
  int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range) {
    return BN_rand_range(r, range);
  }
  