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

 * Copyright (c) 1998-2005 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/ecdsa.h>

#include <assert.h>

#include <string.h>

#include <openssl/bn.h>

#include <openssl/err.h>

#include <openssl/mem.h>

#include <openssl/sha.h>

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

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

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

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

#include "internal.h"

// digest_to_scalar interprets |digest_len| bytes from |digest| as a scalar for

// ECDSA.

static void digest_to_scalar(const EC_GROUP *group, EC_SCALAR *out,

                             const uint8_t *digest, size_t digest_len) {

  const BIGNUM *order = &group->order;

  size_t num_bits = BN_num_bits(order);

  // Need to truncate digest if it is too long: first truncate whole bytes.

  size_t num_bytes = (num_bits + 7) / 8;

  if (digest_len > num_bytes) {

    digest_len = num_bytes;

  }

  bn_big_endian_to_words(out->words, order->width, digest, digest_len);

  // If it is still too long, truncate remaining bits with a shift.

  if (8 * digest_len > num_bits) {

    bn_rshift_words(out->words, out->words, 8 - (num_bits & 0x7), order->width);

  }

  // |out| now has the same bit width as |order|, but this only bounds by

  // 2*|order|. Subtract the order if out of range.

  //

  // Montgomery multiplication accepts the looser bounds, so this isn't strictly

  // necessary, but it is a cleaner abstraction and has no performance impact.

  BN_ULONG tmp[EC_MAX_WORDS];

  bn_reduce_once_in_place(out->words, 0 /* no carry */, order->d, tmp,

                          order->width);

}

ECDSA_SIG *ECDSA_SIG_new(void) {

  ECDSA_SIG *sig = OPENSSL_malloc(sizeof(ECDSA_SIG));

  if (sig == NULL) {

    return NULL;

  }

  sig->r = BN_new();

  sig->s = BN_new();

  if (sig->r == NULL || sig->s == NULL) {

    ECDSA_SIG_free(sig);

    return NULL;

  }

  return sig;

}

void ECDSA_SIG_free(ECDSA_SIG *sig) {

  if (sig == NULL) {

    return;

  }

  BN_free(sig->r);

  BN_free(sig->s);

  OPENSSL_free(sig);

}

const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig) {

  return sig->r;

}

const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig) {

  return sig->s;

}

void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **out_r,

                    const BIGNUM **out_s) {

  if (out_r != NULL) {

    *out_r = sig->r;

  }

  if (out_s != NULL) {

    *out_s = sig->s;

  }

}

int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s) {

  if (r == NULL || s == NULL) {

    return 0;

  }

  BN_free(sig->r);

  BN_free(sig->s);

  sig->r = r;

  sig->s = s;

  return 1;

}

int ecdsa_do_verify_no_self_test(const uint8_t *digest, size_t digest_len,

                                 const ECDSA_SIG *sig, const EC_KEY *eckey) {

  const EC_GROUP *group = EC_KEY_get0_group(eckey);

  const EC_POINT *pub_key = EC_KEY_get0_public_key(eckey);

  if (group == NULL || pub_key == NULL || sig == NULL) {

    OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_MISSING_PARAMETERS);

    return 0;

  }

  EC_SCALAR r, s, u1, u2, s_inv_mont, m;

  if (BN_is_zero(sig->r) ||

      !ec_bignum_to_scalar(group, &r, sig->r) ||

      BN_is_zero(sig->s) ||

      !ec_bignum_to_scalar(group, &s, sig->s)) {

    OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_BAD_SIGNATURE);

    return 0;

  }

  // s_inv_mont = s^-1 in the Montgomery domain.

  if (!ec_scalar_to_montgomery_inv_vartime(group, &s_inv_mont, &s)) {

    OPENSSL_PUT_ERROR(ECDSA, ERR_R_INTERNAL_ERROR);

    return 0;

  }

  // u1 = m * s^-1 mod order

  // u2 = r * s^-1 mod order

  //

  // |s_inv_mont| is in Montgomery form while |m| and |r| are not, so |u1| and

  // |u2| will be taken out of Montgomery form, as desired.

  digest_to_scalar(group, &m, digest, digest_len);

  ec_scalar_mul_montgomery(group, &u1, &m, &s_inv_mont);

  ec_scalar_mul_montgomery(group, &u2, &r, &s_inv_mont);

  EC_JACOBIAN point;

  if (!ec_point_mul_scalar_public(group, &point, &u1, &pub_key->raw, &u2)) {

    OPENSSL_PUT_ERROR(ECDSA, ERR_R_EC_LIB);

    return 0;

  }

  if (!ec_cmp_x_coordinate(group, &point, &r)) {

    OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_BAD_SIGNATURE);

    return 0;

  }

  return 1;

}

int ECDSA_do_verify(const uint8_t *digest, size_t digest_len,

                    const ECDSA_SIG *sig, const EC_KEY *eckey) {

  boringssl_ensure_ecc_self_test();

  return ecdsa_do_verify_no_self_test(digest, digest_len, sig, eckey);

}

static ECDSA_SIG *ecdsa_sign_impl(const EC_GROUP *group, int *out_retry,

                                  const EC_SCALAR *priv_key, const EC_SCALAR *k,

                                  const uint8_t *digest, size_t digest_len) {

  *out_retry = 0;

  // Check that the size of the group order is FIPS compliant (FIPS 186-4

  // B.5.2).

  const BIGNUM *order = EC_GROUP_get0_order(group);

  if (BN_num_bits(order) < 160) {

    OPENSSL_PUT_ERROR(ECDSA, EC_R_INVALID_GROUP_ORDER);

    return NULL;

  }

  // Compute r, the x-coordinate of k * generator.

  EC_JACOBIAN tmp_point;

  EC_SCALAR r;

  if (!ec_point_mul_scalar_base(group, &tmp_point, k) ||

      !ec_get_x_coordinate_as_scalar(group, &r, &tmp_point)) {

    return NULL;

  }

  if (constant_time_declassify_int(ec_scalar_is_zero(group, &r))) {

    *out_retry = 1;

    return NULL;

  }

  // s = priv_key * r. Note if only one parameter is in the Montgomery domain,

  // |ec_scalar_mod_mul_montgomery| will compute the answer in the normal

  // domain.

  EC_SCALAR s;

  ec_scalar_to_montgomery(group, &s, &r);

  ec_scalar_mul_montgomery(group, &s, priv_key, &s);

  // s = m + priv_key * r.

  EC_SCALAR tmp;

  digest_to_scalar(group, &tmp, digest, digest_len);

  ec_scalar_add(group, &s, &s, &tmp);

  // s = k^-1 * (m + priv_key * r). First, we compute k^-1 in the Montgomery

  // domain. This is |ec_scalar_to_montgomery| followed by

  // |ec_scalar_inv0_montgomery|, but |ec_scalar_inv0_montgomery| followed by

  // |ec_scalar_from_montgomery| is equivalent and slightly more efficient.

  // Then, as above, only one parameter is in the Montgomery domain, so the

  // result is in the normal domain. Finally, note k is non-zero (or computing r

  // would fail), so the inverse must exist.

  ec_scalar_inv0_montgomery(group, &tmp, k);     // tmp = k^-1 R^2

  ec_scalar_from_montgomery(group, &tmp, &tmp);  // tmp = k^-1 R

  ec_scalar_mul_montgomery(group, &s, &s, &tmp);

  if (constant_time_declassify_int(ec_scalar_is_zero(group, &s))) {

    *out_retry = 1;

    return NULL;

  }

  CONSTTIME_DECLASSIFY(r.words, sizeof(r.words));

  CONSTTIME_DECLASSIFY(s.words, sizeof(r.words));

  ECDSA_SIG *ret = ECDSA_SIG_new();

  if (ret == NULL ||  //

      !bn_set_words(ret->r, r.words, order->width) ||

      !bn_set_words(ret->s, s.words, order->width)) {

    ECDSA_SIG_free(ret);

    return NULL;

  }

  return ret;

}

ECDSA_SIG *ecdsa_sign_with_nonce_for_known_answer_test(const uint8_t *digest,

                                                       size_t digest_len,

                                                       const EC_KEY *eckey,

                                                       const uint8_t *nonce,

                                                       size_t nonce_len) {

  if (eckey->ecdsa_meth && eckey->ecdsa_meth->sign) {

    OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_NOT_IMPLEMENTED);

    return NULL;

  }

  const EC_GROUP *group = EC_KEY_get0_group(eckey);

  if (group == NULL || eckey->priv_key == NULL) {

    OPENSSL_PUT_ERROR(ECDSA, ERR_R_PASSED_NULL_PARAMETER);

    return NULL;

  }

  const EC_SCALAR *priv_key = &eckey->priv_key->scalar;

  EC_SCALAR k;

  if (!ec_scalar_from_bytes(group, &k, nonce, nonce_len)) {

    return NULL;

  }

  int retry_ignored;

  return ecdsa_sign_impl(group, &retry_ignored, priv_key, &k, digest,

                         digest_len);

}

// This function is only exported for testing and is not called in production

// code.

ECDSA_SIG *ECDSA_sign_with_nonce_and_leak_private_key_for_testing(

    const uint8_t *digest, size_t digest_len, const EC_KEY *eckey,

    const uint8_t *nonce, size_t nonce_len) {

  boringssl_ensure_ecc_self_test();

  return ecdsa_sign_with_nonce_for_known_answer_test(digest, digest_len, eckey,

                                                     nonce, nonce_len);

}

ECDSA_SIG *ECDSA_do_sign(const uint8_t *digest, size_t digest_len,

                         const EC_KEY *eckey) {

  boringssl_ensure_ecc_self_test();

  if (eckey->ecdsa_meth && eckey->ecdsa_meth->sign) {

    OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_NOT_IMPLEMENTED);

    return NULL;

  }

  const EC_GROUP *group = EC_KEY_get0_group(eckey);

  if (group == NULL || eckey->priv_key == NULL) {

    OPENSSL_PUT_ERROR(ECDSA, ERR_R_PASSED_NULL_PARAMETER);

    return NULL;

  }

  const BIGNUM *order = EC_GROUP_get0_order(group);

  const EC_SCALAR *priv_key = &eckey->priv_key->scalar;

  // Pass a SHA512 hash of the private key and digest as additional data

  // into the RBG. This is a hardening measure against entropy failure.

  static_assert(SHA512_DIGEST_LENGTH >= 32,

                "additional_data is too large for SHA-512");

  FIPS_service_indicator_lock_state();

  SHA512_CTX sha;

  uint8_t additional_data[SHA512_DIGEST_LENGTH];

  SHA512_Init(&sha);

  SHA512_Update(&sha, priv_key->words, order->width * sizeof(BN_ULONG));

  SHA512_Update(&sha, digest, digest_len);

  SHA512_Final(additional_data, &sha);

  // Cap iterations so callers who supply invalid values as custom groups do not

  // infinite loop. This does not impact valid parameters (e.g. those covered by

  // FIPS) because the probability of requiring even one retry is negligible,

  // let alone 32.

  static const int kMaxIterations = 32;

  ECDSA_SIG *ret = NULL;

  int iters = 0;

  for (;;) {

    EC_SCALAR k;

    if (!ec_random_nonzero_scalar(group, &k, additional_data)) {

      ret = NULL;

      goto out;

    }

    // TODO(davidben): Move this inside |ec_random_nonzero_scalar| or lower, so

    // that all scalars we generate are, by default, secret.

    CONSTTIME_SECRET(k.words, sizeof(k.words));

    int retry;

    ret = ecdsa_sign_impl(group, &retry, priv_key, &k, digest, digest_len);

    if (ret != NULL || !retry) {

      goto out;

    }

    iters++;

    if (iters > kMaxIterations) {

      OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_TOO_MANY_ITERATIONS);

      goto out;

    }

  }

out:

  FIPS_service_indicator_unlock_state();

  return ret;

}