Coverage Report

Created: 2024-11-21 07:03

/src/boringssl/crypto/fipsmodule/bn/random.c.inc
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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 * All rights reserved.
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 *
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 * This package is an SSL implementation written
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 * by Eric Young (eay@cryptsoft.com).
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 * The implementation was written so as to conform with Netscapes SSL.
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 *
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 * This library is free for commercial and non-commercial use as long as
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 * the following conditions are aheared to.  The following conditions
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 * apply to all code found in this distribution, be it the RC4, RSA,
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 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
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 * included with this distribution is covered by the same copyright terms
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 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
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 *
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 * Copyright remains Eric Young's, and as such any Copyright notices in
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 * the code are not to be removed.
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 * If this package is used in a product, Eric Young should be given attribution
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 * as the author of the parts of the library used.
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 * This can be in the form of a textual message at program startup or
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 * in documentation (online or textual) provided with the package.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. All advertising materials mentioning features or use of this software
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 *    must display the following acknowledgement:
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 *    "This product includes cryptographic software written by
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 *     Eric Young (eay@cryptsoft.com)"
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 *    The word 'cryptographic' can be left out if the rouines from the library
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 *    being used are not cryptographic related :-).
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 * 4. If you include any Windows specific code (or a derivative thereof) from
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 *    the apps directory (application code) you must include an acknowledgement:
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 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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 *
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 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 *
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 * The licence and distribution terms for any publically available version or
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 * derivative of this code cannot be changed.  i.e. this code cannot simply be
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 * copied and put under another distribution licence
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 * [including the GNU Public Licence.]
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 */
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/* ====================================================================
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 * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 *
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in
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 *    the documentation and/or other materials provided with the
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 *    distribution.
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 *
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 * 3. All advertising materials mentioning features or use of this
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 *    software must display the following acknowledgment:
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 *    "This product includes software developed by the OpenSSL Project
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 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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 *
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 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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 *    endorse or promote products derived from this software without
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 *    prior written permission. For written permission, please contact
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 *    openssl-core@openssl.org.
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 *
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 * 5. Products derived from this software may not be called "OpenSSL"
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 *    nor may "OpenSSL" appear in their names without prior written
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 *    permission of the OpenSSL Project.
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 *
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 * 6. Redistributions of any form whatsoever must retain the following
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 *    acknowledgment:
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 *    "This product includes software developed by the OpenSSL Project
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 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 * OF THE POSSIBILITY OF SUCH DAMAGE.
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 * ====================================================================
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 *
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 * This product includes cryptographic software written by Eric Young
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 * (eay@cryptsoft.com).  This product includes software written by Tim
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 * Hudson (tjh@cryptsoft.com). */
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#include <openssl/bn.h>
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#include <assert.h>
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#include <limits.h>
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#include <string.h>
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#include <openssl/err.h>
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#include "../../internal.h"
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#include "../bcm_interface.h"
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#include "../service_indicator/internal.h"
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#include "internal.h"
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8
int BN_rand(BIGNUM *rnd, int bits, int top, int bottom) {
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8
  if (rnd == NULL) {
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0
    return 0;
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0
  }
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8
  if (top != BN_RAND_TOP_ANY && top != BN_RAND_TOP_ONE &&
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8
      top != BN_RAND_TOP_TWO) {
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    OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
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    return 0;
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  }
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0
  if (bottom != BN_RAND_BOTTOM_ANY && bottom != BN_RAND_BOTTOM_ODD) {
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0
    OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
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0
    return 0;
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0
  }
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0
  if (bits == 0) {
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0
    BN_zero(rnd);
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0
    return 1;
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0
  }
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0
  if (bits > INT_MAX - (BN_BITS2 - 1)) {
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0
    OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);
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0
    return 0;
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0
  }
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0
  int words = (bits + BN_BITS2 - 1) / BN_BITS2;
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0
  int bit = (bits - 1) % BN_BITS2;
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0
  const BN_ULONG kOne = 1;
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0
  const BN_ULONG kThree = 3;
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0
  BN_ULONG mask = bit < BN_BITS2 - 1 ? (kOne << (bit + 1)) - 1 : BN_MASK2;
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0
  if (!bn_wexpand(rnd, words)) {
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0
    return 0;
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0
  }
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0
  FIPS_service_indicator_lock_state();
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0
  BCM_rand_bytes((uint8_t *)rnd->d, words * sizeof(BN_ULONG));
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0
  FIPS_service_indicator_unlock_state();
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0
  rnd->d[words - 1] &= mask;
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0
  if (top != BN_RAND_TOP_ANY) {
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0
    if (top == BN_RAND_TOP_TWO && bits > 1) {
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0
      if (bit == 0) {
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0
        rnd->d[words - 1] |= 1;
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0
        rnd->d[words - 2] |= kOne << (BN_BITS2 - 1);
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0
      } else {
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0
        rnd->d[words - 1] |= kThree << (bit - 1);
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0
      }
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0
    } else {
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0
      rnd->d[words - 1] |= kOne << bit;
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0
    }
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0
  }
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0
  if (bottom == BN_RAND_BOTTOM_ODD) {
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0
    rnd->d[0] |= 1;
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0
  }
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0
  rnd->neg = 0;
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0
  rnd->width = words;
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0
  return 1;
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0
}
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8
int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom) {
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  return BN_rand(rnd, bits, top, bottom);
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8
}
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// bn_less_than_word_mask returns a mask of all ones if the number represented
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// by |len| words at |a| is less than |b| and zero otherwise. It performs this
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// computation in time independent of the value of |a|. |b| is assumed public.
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static crypto_word_t bn_less_than_word_mask(const BN_ULONG *a, size_t len,
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7.95k
                                            BN_ULONG b) {
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  if (b == 0) {
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    return CONSTTIME_FALSE_W;
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  }
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  if (len == 0) {
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0
    return CONSTTIME_TRUE_W;
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0
  }
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  // |a| < |b| iff a[1..len-1] are all zero and a[0] < b.
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7.93k
  static_assert(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
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7.93k
                "crypto_word_t is too small");
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  crypto_word_t mask = 0;
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  for (size_t i = 1; i < len; i++) {
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    mask |= a[i];
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  }
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  // |mask| is now zero iff a[1..len-1] are all zero.
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  mask = constant_time_is_zero_w(mask);
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  mask &= constant_time_lt_w(a[0], b);
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  return mask;
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}
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int bn_in_range_words(const BN_ULONG *a, BN_ULONG min_inclusive,
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                      const BN_ULONG *max_exclusive, size_t len) {
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  crypto_word_t mask = ~bn_less_than_word_mask(a, len, min_inclusive);
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  return mask & bn_less_than_words(a, max_exclusive, len);
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}
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static int bn_range_to_mask(size_t *out_words, BN_ULONG *out_mask,
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                            size_t min_inclusive, const BN_ULONG *max_exclusive,
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3.99k
                            size_t len) {
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  // The magnitude of |max_exclusive| is assumed public.
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3.99k
  size_t words = len;
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  while (words > 0 && max_exclusive[words - 1] == 0) {
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1
    words--;
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1
  }
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3.99k
  if (words == 0 || (words == 1 && max_exclusive[0] <= min_inclusive)) {
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1
    OPENSSL_PUT_ERROR(BN, BN_R_INVALID_RANGE);
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1
    return 0;
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1
  }
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3.99k
  BN_ULONG mask = max_exclusive[words - 1];
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  // This sets all bits in |mask| below the most significant bit.
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  mask |= mask >> 1;
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  mask |= mask >> 2;
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  mask |= mask >> 4;
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  mask |= mask >> 8;
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3.99k
  mask |= mask >> 16;
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3.99k
#if defined(OPENSSL_64_BIT)
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3.99k
  mask |= mask >> 32;
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3.99k
#endif
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  *out_words = words;
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  *out_mask = mask;
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  return 1;
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}
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int bn_rand_range_words(BN_ULONG *out, BN_ULONG min_inclusive,
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                        const BN_ULONG *max_exclusive, size_t len,
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61
                        const uint8_t additional_data[32]) {
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  // This function implements the equivalent of steps 4 through 7 of FIPS 186-4
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  // appendices B.4.2 and B.5.2. When called in those contexts, |max_exclusive|
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  // is n and |min_inclusive| is one.
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  // Compute the bit length of |max_exclusive| (step 1), in terms of a number of
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  // |words| worth of entropy to fill and a mask of bits to clear in the top
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  // word.
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  size_t words;
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61
  BN_ULONG mask;
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61
  if (!bn_range_to_mask(&words, &mask, min_inclusive, max_exclusive, len)) {
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1
    return 0;
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1
  }
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  // Fill any unused words with zero.
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  OPENSSL_memset(out + words, 0, (len - words) * sizeof(BN_ULONG));
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266
60
  unsigned count = 100;
267
81
  do {
268
81
    if (!--count) {
269
0
      OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_ITERATIONS);
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0
      return 0;
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0
    }
272
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    // Steps 4 and 5. Use |words| and |mask| together to obtain a string of N
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    // bits, where N is the bit length of |max_exclusive|.
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81
    FIPS_service_indicator_lock_state();
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    BCM_rand_bytes_with_additional_data(
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        (uint8_t *)out, words * sizeof(BN_ULONG), additional_data);
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81
    FIPS_service_indicator_unlock_state();
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81
    out[words - 1] &= mask;
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    // If out >= max_exclusive or out < min_inclusive, retry. This implements
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    // the equivalent of steps 6 and 7 without leaking the value of |out|. The
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    // result of this comparison may be treated as public. It only reveals how
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    // many attempts were needed before we found a value in range. This is
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    // independent of the final secret output, and has a distribution that
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    // depends only on |min_inclusive| and |max_exclusive|, both of which are
287
    // public.
288
81
  } while (!constant_time_declassify_int(
289
81
      bn_in_range_words(out, min_inclusive, max_exclusive, words)));
290
60
  return 1;
291
60
}
292
293
int BN_rand_range_ex(BIGNUM *r, BN_ULONG min_inclusive,
294
55
                     const BIGNUM *max_exclusive) {
295
55
  static const uint8_t kDefaultAdditionalData[32] = {0};
296
55
  if (!bn_wexpand(r, max_exclusive->width) ||
297
55
      !bn_rand_range_words(r->d, min_inclusive, max_exclusive->d,
298
55
                           max_exclusive->width, kDefaultAdditionalData)) {
299
1
    return 0;
300
1
  }
301
302
54
  r->neg = 0;
303
54
  r->width = max_exclusive->width;
304
54
  return 1;
305
55
}
306
307
int bn_rand_secret_range(BIGNUM *r, int *out_is_uniform, BN_ULONG min_inclusive,
308
3.93k
                         const BIGNUM *max_exclusive) {
309
3.93k
  size_t words;
310
3.93k
  BN_ULONG mask;
311
3.93k
  if (!bn_range_to_mask(&words, &mask, min_inclusive, max_exclusive->d,
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3.93k
                        max_exclusive->width) ||
313
3.93k
      !bn_wexpand(r, words)) {
314
0
    return 0;
315
0
  }
316
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3.93k
  assert(words > 0);
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3.93k
  assert(mask != 0);
319
  // The range must be large enough for bit tricks to fix invalid values.
320
3.93k
  if (words == 1 && min_inclusive > mask >> 1) {
321
0
    OPENSSL_PUT_ERROR(BN, BN_R_INVALID_RANGE);
322
0
    return 0;
323
0
  }
324
325
  // Select a uniform random number with num_bits(max_exclusive) bits.
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3.93k
  FIPS_service_indicator_lock_state();
327
3.93k
  BCM_rand_bytes((uint8_t *)r->d, words * sizeof(BN_ULONG));
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3.93k
  FIPS_service_indicator_unlock_state();
329
3.93k
  r->d[words - 1] &= mask;
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331
  // Check, in constant-time, if the value is in range.
332
3.93k
  *out_is_uniform =
333
3.93k
      bn_in_range_words(r->d, min_inclusive, max_exclusive->d, words);
334
3.93k
  crypto_word_t in_range = *out_is_uniform;
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3.93k
  in_range = 0 - in_range;
336
337
  // If the value is not in range, force it to be in range.
338
3.93k
  r->d[0] |= constant_time_select_w(in_range, 0, min_inclusive);
339
3.93k
  r->d[words - 1] &= constant_time_select_w(in_range, BN_MASK2, mask >> 1);
340
3.93k
  declassify_assert(
341
3.93k
      bn_in_range_words(r->d, min_inclusive, max_exclusive->d, words));
342
343
3.93k
  r->neg = 0;
344
3.93k
  r->width = (int)words;
345
3.93k
  return 1;
346
3.93k
}
347
348
24
int BN_rand_range(BIGNUM *r, const BIGNUM *range) {
349
24
  return BN_rand_range_ex(r, 0, range);
350
24
}
351
352
9
int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range) {
353
9
  return BN_rand_range(r, range);
354
9
}