ring 0.3.0

/* 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 <openssl/err.h>

#include "internal.h"


int BN_mod_inverse_odd(BIGNUM *out, int *out_no_inverse, const BIGNUM *a,
                       const BIGNUM *n) {
  *out_no_inverse = 0;

  if (!BN_is_odd(n)) {
    OPENSSL_PUT_ERROR(BN, BN_R_CALLED_WITH_EVEN_MODULUS);
    return 0;
  }

  if (BN_is_negative(a) || BN_cmp(a, n) >= 0) {
    OPENSSL_PUT_ERROR(BN, BN_R_INPUT_NOT_REDUCED);
    return 0;
  }

  BIGNUM A;
  BN_init(&A);

  BIGNUM B;
  BN_init(&B);

  BIGNUM X;
  BN_init(&X);

  BIGNUM Y;
  BN_init(&Y);

  int ret = 0;
  int sign;

  BIGNUM *R = out;

  BN_zero(&Y);
  if (!BN_one(&X) || BN_copy(&B, a) == NULL || BN_copy(&A, n) == NULL) {
    goto err;
  }
  A.neg = 0;
  sign = -1;
  /* From  B = a mod |n|,  A = |n|  it follows that
   *
   *      0 <= B < A,
   *     -sign*X*a  ==  B   (mod |n|),
   *      sign*Y*a  ==  A   (mod |n|).
   */

  /* Binary inversion algorithm; requires odd modulus. This is faster than the
   * general algorithm if the modulus is sufficiently small (about 400 .. 500
   * bits on 32-bit systems, but much more on 64-bit systems) */
  int shift;

  while (!BN_is_zero(&B)) {
    /*      0 < B < |n|,
     *      0 < A <= |n|,
     * (1) -sign*X*a  ==  B   (mod |n|),
     * (2)  sign*Y*a  ==  A   (mod |n|) */

    /* Now divide  B  by the maximum possible power of two in the integers,
     * and divide  X  by the same value mod |n|.
     * When we're done, (1) still holds. */
    shift = 0;
    while (!BN_is_bit_set(&B, shift)) {
      /* note that 0 < B */
      shift++;

      if (BN_is_odd(&X)) {
        if (!BN_uadd(&X, &X, n)) {
          goto err;
        }
      }
      /* now X is even, so we can easily divide it by two */
      if (!BN_rshift1(&X, &X)) {
        goto err;
      }
    }
    if (shift > 0) {
      if (!BN_rshift(&B, &B, shift)) {
        goto err;
      }
    }

    /* Same for A and Y. Afterwards, (2) still holds. */
    shift = 0;
    while (!BN_is_bit_set(&A, shift)) {
      /* note that 0 < A */
      shift++;

      if (BN_is_odd(&Y)) {
        if (!BN_uadd(&Y, &Y, n)) {
          goto err;
        }
      }
      /* now Y is even */
      if (!BN_rshift1(&Y, &Y)) {
        goto err;
      }
    }
    if (shift > 0) {
      if (!BN_rshift(&A, &A, shift)) {
        goto err;
      }
    }

    /* We still have (1) and (2).
     * Both  A  and  B  are odd.
     * The following computations ensure that
     *
     *     0 <= B < |n|,
     *      0 < A < |n|,
     * (1) -sign*X*a  ==  B   (mod |n|),
     * (2)  sign*Y*a  ==  A   (mod |n|),
     *
     * and that either  A  or  B  is even in the next iteration. */
    if (BN_ucmp(&B, &A) >= 0) {
      /* -sign*(X + Y)*a == B - A  (mod |n|) */
      if (!BN_uadd(&X, &X, &Y)) {
        goto err;
      }
      /* NB: we could use BN_mod_add_quick(X, X, Y, n), but that
       * actually makes the algorithm slower */
      if (!BN_usub(&B, &B, &A)) {
        goto err;
      }
    } else {
      /*  sign*(X + Y)*a == A - B  (mod |n|) */
      if (!BN_uadd(&Y, &Y, &X)) {
        goto err;
      }
      /* as above, BN_mod_add_quick(Y, Y, X, n) would slow things down */
      if (!BN_usub(&A, &A, &B)) {
        goto err;
      }
    }
  }

  if (!BN_is_one(&A)) {
    *out_no_inverse = 1;
    OPENSSL_PUT_ERROR(BN, BN_R_NO_INVERSE);
    goto err;
  }

  /* The while loop (Euclid's algorithm) ends when
   *      A == gcd(a,n);
   * we have
   *       sign*Y*a  ==  A  (mod |n|),
   * where  Y  is non-negative. */

  if (sign < 0) {
    if (!BN_sub(&Y, n, &Y)) {
      goto err;
    }
  }
  /* Now  Y*a  ==  A  (mod |n|).  */

  /* Y*a == 1  (mod |n|) */
  if (!Y.neg && BN_ucmp(&Y, n) < 0) {
    if (!BN_copy(R, &Y)) {
      goto err;
    }
  } else {
    if (!BN_nnmod(R, &Y, n)) {
      goto err;
    }
  }

  ret = 1;

err:
  BN_free(&A);
  BN_free(&B);
  BN_free(&X);
  BN_free(&Y);

  return ret;
}

int BN_mod_inverse_blinded(BIGNUM *out, int *out_no_inverse, const BIGNUM *a,
                           const BN_MONT_CTX *mont, RAND *rng) {
  *out_no_inverse = 0;

  if (BN_is_negative(a) || BN_cmp(a, &mont->N) >= 0) {
    OPENSSL_PUT_ERROR(BN, BN_R_INPUT_NOT_REDUCED);
    return 0;
  }

  int ret = 0;
  BIGNUM blinding_factor;
  BN_init(&blinding_factor);

  if (!BN_rand_range_ex(&blinding_factor, &mont->N, rng) ||
      !BN_mod_mul_mont(out, &blinding_factor, a, mont) ||
      !BN_mod_inverse_odd(out, out_no_inverse, out, &mont->N) ||
      !BN_mod_mul_mont(out, &blinding_factor, out, mont)) {
    OPENSSL_PUT_ERROR(BN, ERR_R_BN_LIB);
    goto err;
  }

  ret = 1;

err:
  BN_free(&blinding_factor);
  return ret;
}