ring/crypto/bn/montgomery.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) 1998-2006 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 <GFp/bn.h>

#include <assert.h>
#include <string.h>

#include <GFp/mem.h>
#include <GFp/type_check.h>

#include "internal.h"
#include "../internal.h"


/* Avoid -Wmissing-prototypes warnings. */
int GFp_BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, const BIGNUM *n,
                                const BN_ULONG n0[BN_MONT_CTX_N0_LIMBS]);

OPENSSL_COMPILE_ASSERT(BN_MONT_CTX_N0_LIMBS == 1 || BN_MONT_CTX_N0_LIMBS == 2,
                       BN_MONT_CTX_N0_LIMBS_VALUE_INVALID);
OPENSSL_COMPILE_ASSERT(sizeof(BN_ULONG) * BN_MONT_CTX_N0_LIMBS ==
                       sizeof(uint64_t), BN_MONT_CTX_set_64_bit_mismatch);

int GFp_BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, const BIGNUM *n,
                                const BN_ULONG n0_[BN_MONT_CTX_N0_LIMBS]) {
  assert(ret != r);

  BN_ULONG *ap, *np, *rp, n0, v, carry;
  int nl, max, i;

  nl = n->top;
  if (nl == 0) {
    ret->top = 0;
    return 1;
  }

  max = (2 * nl); /* carry is stored separately */
  if (!GFp_bn_wexpand(r, max)) {
    return 0;
  }

  np = n->d;
  rp = r->d;

  /* clear the top words of T */
  if (max > r->top) {
    memset(&rp[r->top], 0, (max - r->top) * sizeof(BN_ULONG));
  }

  r->top = max;
  n0 = n0_[0];

  for (carry = 0, i = 0; i < nl; i++, rp++) {
    v = GFp_bn_mul_add_words(rp, np, nl, (rp[0] * n0) & BN_MASK2);
    v = (v + carry + rp[nl]) & BN_MASK2;
    carry |= (v != rp[nl]);
    carry &= (v <= rp[nl]);
    rp[nl] = v;
  }

  if (!GFp_bn_wexpand(ret, nl)) {
    return 0;
  }
  ret->top = nl;

  rp = ret->d;
  ap = &(r->d[nl]);

  {
    BN_ULONG *nrp;
    uintptr_t m;

    v = GFp_bn_sub_words(rp, ap, np, nl) - carry;
    /* if subtraction result is real, then trick unconditional memcpy below to
     * perform in-place "refresh" instead of actual copy. */
    m = (0u - (uintptr_t)v);
    nrp = (BN_ULONG *)(((uintptr_t)rp & ~m) | ((uintptr_t)ap & m));

    for (i = 0, nl -= 4; i < nl; i += 4) {
      BN_ULONG t1, t2, t3, t4;

      t1 = nrp[i + 0];
      t2 = nrp[i + 1];
      t3 = nrp[i + 2];
      ap[i + 0] = 0;
      t4 = nrp[i + 3];
      ap[i + 1] = 0;
      rp[i + 0] = t1;
      ap[i + 2] = 0;
      rp[i + 1] = t2;
      ap[i + 3] = 0;
      rp[i + 2] = t3;
      rp[i + 3] = t4;
    }

    for (nl += 4; i < nl; i++) {
      rp[i] = nrp[i], ap[i] = 0;
    }
  }

  GFp_bn_correct_top(r);
  GFp_bn_correct_top(ret);

  return 1;
}

/* Assumes a < n and b < n */
int GFp_BN_mod_mul_mont(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
                        const BIGNUM *n,
                        const BN_ULONG n0[BN_MONT_CTX_N0_LIMBS]) {
  int num = n->top;

  /* GFp_bn_mul_mont requires at least four limbs, at least for x86. */
  if (num < 4) {
    return 0;
  }

  if (a->top == num && b->top == num) {
    if (!GFp_bn_wexpand(r, num)) {
      return 0;
    }
    GFp_bn_mul_mont(r->d, a->d, b->d, n->d, n0, num);
    r->top = num;
    GFp_bn_correct_top(r);
    return 1;
  }

  BIGNUM tmp;
  GFp_BN_init(&tmp);

  int ret = 0;

  if (!GFp_BN_mul_no_alias(&tmp, a, b) ||
      !GFp_BN_from_montgomery_word(r, &tmp, n, n0)) {
    goto err;
  }

  ret = 1;

err:
  GFp_BN_free(&tmp);

  return ret;
}