/* 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/bn.h>

#include <assert.h>

#include <limits.h>

#include "internal.h"

void bn_big_endian_to_words(BN_ULONG *out, size_t out_len, const uint8_t *in,

                            size_t in_len) {

  // The caller should have sized |out| to fit |in| without truncating. This

  // condition ensures we do not overflow |out|, so use a runtime check.

  BSSL_CHECK(in_len <= out_len * sizeof(BN_ULONG));

  // Load whole words.

  while (in_len >= sizeof(BN_ULONG)) {

    in_len -= sizeof(BN_ULONG);

    out[0] = CRYPTO_load_word_be(in + in_len);

    out++;

    out_len--;

  }

  // Load the last partial word.

  if (in_len != 0) {

    BN_ULONG word = 0;

    for (size_t i = 0; i < in_len; i++) {

      word = (word << 8) | in[i];

    }

    out[0] = word;

    out++;

    out_len--;

  }

  // Fill the remainder with zeros.

  OPENSSL_memset(out, 0, out_len * sizeof(BN_ULONG));

}

BIGNUM *BN_bin2bn(const uint8_t *in, size_t len, BIGNUM *ret) {

  BIGNUM *bn = NULL;

  if (ret == NULL) {

    bn = BN_new();

    if (bn == NULL) {

      return NULL;

    }

    ret = bn;

  }

  if (len == 0) {

    ret->width = 0;

    return ret;

  }

  size_t num_words = ((len - 1) / BN_BYTES) + 1;

  if (!bn_wexpand(ret, num_words)) {

    BN_free(bn);

    return NULL;

  }

  // |bn_wexpand| must check bounds on |num_words| to write it into

  // |ret->dmax|.

  assert(num_words <= INT_MAX);

  ret->width = (int)num_words;

  ret->neg = 0;

  bn_big_endian_to_words(ret->d, ret->width, in, len);

  return ret;

}

BIGNUM *BN_lebin2bn(const uint8_t *in, size_t len, BIGNUM *ret) {

  BIGNUM *bn = NULL;

  if (ret == NULL) {

    bn = BN_new();

    if (bn == NULL) {

      return NULL;

    }

    ret = bn;

  }

  if (len == 0) {

    ret->width = 0;

    ret->neg = 0;

    return ret;

  }

  // Reserve enough space in |ret|.

  size_t num_words = ((len - 1) / BN_BYTES) + 1;

  if (!bn_wexpand(ret, num_words)) {

    BN_free(bn);

    return NULL;

  }

  ret->width = (int)num_words;

  // Make sure the top bytes will be zeroed.

  ret->d[num_words - 1] = 0;

  // We only support little-endian platforms, so we can simply memcpy the

  // internal representation.

  OPENSSL_memcpy(ret->d, in, len);

  return ret;

}

BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret) {

  return BN_lebin2bn(in, len, ret);

}

// fits_in_bytes returns one if the |num_words| words in |words| can be

// represented in |num_bytes| bytes.

static int fits_in_bytes(const BN_ULONG *words, size_t num_words,

                         size_t num_bytes) {

  const uint8_t *bytes = (const uint8_t *)words;

  size_t tot_bytes = num_words * sizeof(BN_ULONG);

  uint8_t mask = 0;

  for (size_t i = num_bytes; i < tot_bytes; i++) {

    mask |= bytes[i];

  }

  return mask == 0;

}

void bn_assert_fits_in_bytes(const BIGNUM *bn, size_t num) {

  const uint8_t *bytes = (const uint8_t *)bn->d;

  size_t tot_bytes = bn->width * sizeof(BN_ULONG);

  if (tot_bytes > num) {

    CONSTTIME_DECLASSIFY(bytes + num, tot_bytes - num);

    for (size_t i = num; i < tot_bytes; i++) {

      assert(bytes[i] == 0);

    }

    (void)bytes;

  }

}

void bn_words_to_big_endian(uint8_t *out, size_t out_len, const BN_ULONG *in,

                            size_t in_len) {

  // The caller should have selected an output length without truncation.

  declassify_assert(fits_in_bytes(in, in_len, out_len));

  // We only support little-endian platforms, so the internal representation is

  // also little-endian as bytes. We can simply copy it in reverse.

  const uint8_t *bytes = (const uint8_t *)in;

  size_t num_bytes = in_len * sizeof(BN_ULONG);

  if (out_len < num_bytes) {

    num_bytes = out_len;

  }

  for (size_t i = 0; i < num_bytes; i++) {

    out[out_len - i - 1] = bytes[i];

  }

  // Pad out the rest of the buffer with zeroes.

  OPENSSL_memset(out, 0, out_len - num_bytes);

}

size_t BN_bn2bin(const BIGNUM *in, uint8_t *out) {

  size_t n = BN_num_bytes(in);

  bn_words_to_big_endian(out, n, in->d, in->width);

  return n;

}

int BN_bn2le_padded(uint8_t *out, size_t len, const BIGNUM *in) {

  if (!fits_in_bytes(in->d, in->width, len)) {

    return 0;

  }

  // We only support little-endian platforms, so we can simply memcpy into the

  // internal representation.

  const uint8_t *bytes = (const uint8_t *)in->d;

  size_t num_bytes = in->width * BN_BYTES;

  if (len < num_bytes) {

    num_bytes = len;

  }

  OPENSSL_memcpy(out, bytes, num_bytes);

  // Pad out the rest of the buffer with zeroes.

  OPENSSL_memset(out + num_bytes, 0, len - num_bytes);

  return 1;

}

int BN_bn2bin_padded(uint8_t *out, size_t len, const BIGNUM *in) {

  if (!fits_in_bytes(in->d, in->width, len)) {

    return 0;

  }

  bn_words_to_big_endian(out, len, in->d, in->width);

  return 1;

}

BN_ULONG BN_get_word(const BIGNUM *bn) {

  switch (bn_minimal_width(bn)) {

    case 0:

      return 0;

    case 1:

      return bn->d[0];

    default:

      return BN_MASK2;

  }

}

int BN_get_u64(const BIGNUM *bn, uint64_t *out) {

  switch (bn_minimal_width(bn)) {

    case 0:

      *out = 0;

      return 1;

    case 1:

      *out = bn->d[0];

      return 1;

#if defined(OPENSSL_32_BIT)

    case 2:

      *out = (uint64_t) bn->d[0] | (((uint64_t) bn->d[1]) << 32);

      return 1;

#endif

    default:

      return 0;

  }

}