/* ====================================================================

 * 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).

 *

 * 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.] */

#include <openssl/rsa.h>

#include <string.h>

#include <openssl/bn.h>

#include <openssl/mem.h>

#include <openssl/err.h>

#include "internal.h"

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

#define BN_BLINDING_COUNTER 32

struct bn_blinding_st {

  BIGNUM *A;  // The base blinding factor, Montgomery-encoded.

  BIGNUM *Ai;  // The inverse of the blinding factor, Montgomery-encoded.

  unsigned counter;

};

static int bn_blinding_create_param(BN_BLINDING *b, const BIGNUM *e,

                                    const BN_MONT_CTX *mont, BN_CTX *ctx);

BN_BLINDING *BN_BLINDING_new(void) {

  BN_BLINDING *ret = OPENSSL_zalloc(sizeof(BN_BLINDING));

  if (ret == NULL) {

    return NULL;

  }

  ret->A = BN_new();

  if (ret->A == NULL) {

    goto err;

  }

  ret->Ai = BN_new();

  if (ret->Ai == NULL) {

    goto err;

  }

  // The blinding values need to be created before this blinding can be used.

  ret->counter = BN_BLINDING_COUNTER - 1;

  return ret;

err:

  BN_BLINDING_free(ret);

  return NULL;

}

void BN_BLINDING_free(BN_BLINDING *r) {

  if (r == NULL) {

    return;

  }

  BN_free(r->A);

  BN_free(r->Ai);

  OPENSSL_free(r);

}

void BN_BLINDING_invalidate(BN_BLINDING *b) {

  b->counter = BN_BLINDING_COUNTER - 1;

}

static int bn_blinding_update(BN_BLINDING *b, const BIGNUM *e,

                              const BN_MONT_CTX *mont, BN_CTX *ctx) {

  if (++b->counter == BN_BLINDING_COUNTER) {

    // re-create blinding parameters

    if (!bn_blinding_create_param(b, e, mont, ctx)) {

      goto err;

    }

    b->counter = 0;

  } else {

    if (!BN_mod_mul_montgomery(b->A, b->A, b->A, mont, ctx) ||

        !BN_mod_mul_montgomery(b->Ai, b->Ai, b->Ai, mont, ctx)) {

      goto err;

    }

  }

  return 1;

err:

  // |A| and |Ai| may be in an inconsistent state so they both need to be

  // replaced the next time this blinding is used. Note that this is only

  // sufficient because support for |BN_BLINDING_NO_UPDATE| and

  // |BN_BLINDING_NO_RECREATE| was previously dropped.

  b->counter = BN_BLINDING_COUNTER - 1;

  return 0;

}

int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, const BIGNUM *e,

                        const BN_MONT_CTX *mont, BN_CTX *ctx) {

  // |n| is not Montgomery-encoded and |b->A| is. |BN_mod_mul_montgomery|

  // cancels one Montgomery factor, so the resulting value of |n| is unencoded.

  if (!bn_blinding_update(b, e, mont, ctx) ||

      !BN_mod_mul_montgomery(n, n, b->A, mont, ctx)) {

    return 0;

  }

  return 1;

}

int BN_BLINDING_invert(BIGNUM *n, const BN_BLINDING *b, BN_MONT_CTX *mont,

                       BN_CTX *ctx) {

  // |n| is not Montgomery-encoded and |b->A| is. |BN_mod_mul_montgomery|

  // cancels one Montgomery factor, so the resulting value of |n| is unencoded.

  return BN_mod_mul_montgomery(n, n, b->Ai, mont, ctx);

}

static int bn_blinding_create_param(BN_BLINDING *b, const BIGNUM *e,

                                    const BN_MONT_CTX *mont, BN_CTX *ctx) {

  int no_inverse;

  if (!BN_rand_range_ex(b->A, 1, &mont->N) ||

      // Compute |b->A|^-1 in Montgomery form. Note |BN_from_montgomery| +

      // |BN_mod_inverse_blinded| is equivalent to, but more efficient than,

      // |BN_mod_inverse_blinded| + |BN_to_montgomery|.

      //

      // We do not retry if |b->A| has no inverse. Finding a non-invertible

      // value of |b->A| is equivalent to factoring |mont->N|. There is

      // negligible probability of stumbling on one at random.

      !BN_from_montgomery(b->Ai, b->A, mont, ctx) ||

      !BN_mod_inverse_blinded(b->Ai, &no_inverse, b->Ai, mont, ctx) ||

      // TODO(davidben): |BN_mod_exp_mont| internally computes the result in

      // Montgomery form. Save a pair of Montgomery reductions and a

      // multiplication by returning that value directly.

      !BN_mod_exp_mont(b->A, b->A, e, &mont->N, ctx, mont) ||

      !BN_to_montgomery(b->A, b->A, mont, ctx)) {

    OPENSSL_PUT_ERROR(RSA, ERR_R_INTERNAL_ERROR);

    return 0;

  }

  return 1;

}