// Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <openssl/bn.h>

#include <assert.h>

#include <limits.h>

#include <string.h>

#include <openssl/err.h>

#include <openssl/mem.h>

#include "../delocate.h"

#include "internal.h"

// BN_MAX_WORDS is the maximum number of words allowed in a |BIGNUM|. It is

// sized so byte and bit counts of a |BIGNUM| always fit in |int|, with room to

// spare.

#define BN_MAX_WORDS (INT_MAX / (4 * BN_BITS2))

BIGNUM *BN_new(void) {

  BIGNUM *bn = reinterpret_cast<BIGNUM *>(OPENSSL_malloc(sizeof(BIGNUM)));

  if (bn == NULL) {

    return NULL;

  }

  OPENSSL_memset(bn, 0, sizeof(BIGNUM));

  bn->flags = BN_FLG_MALLOCED;

  return bn;

}

BIGNUM *BN_secure_new(void) { return BN_new(); }

void BN_init(BIGNUM *bn) { OPENSSL_memset(bn, 0, sizeof(BIGNUM)); }

void BN_free(BIGNUM *bn) {

  if (bn == NULL) {

    return;

  }

  if ((bn->flags & BN_FLG_STATIC_DATA) == 0) {

    OPENSSL_free(bn->d);

  }

  if (bn->flags & BN_FLG_MALLOCED) {

    OPENSSL_free(bn);

  } else {

    bn->d = NULL;

  }

}

void BN_clear_free(BIGNUM *bn) { BN_free(bn); }

BIGNUM *BN_dup(const BIGNUM *src) {

  BIGNUM *copy;

  if (src == NULL) {

    return NULL;

  }

  copy = BN_new();

  if (copy == NULL) {

    return NULL;

  }

  if (!BN_copy(copy, src)) {

    BN_free(copy);

    return NULL;

  }

  return copy;

}

BIGNUM *BN_copy(BIGNUM *dest, const BIGNUM *src) {

  if (src == dest) {

    return dest;

  }

  if (!bn_wexpand(dest, src->width)) {

    return NULL;

  }

  OPENSSL_memcpy(dest->d, src->d, sizeof(src->d[0]) * src->width);

  dest->width = src->width;

  dest->neg = src->neg;

  return dest;

}

void BN_clear(BIGNUM *bn) {

  if (bn->d != NULL) {

    OPENSSL_memset(bn->d, 0, bn->dmax * sizeof(bn->d[0]));

  }

  bn->width = 0;

  bn->neg = 0;

}

DEFINE_METHOD_FUNCTION(BIGNUM, BN_value_one) {

  static const BN_ULONG kOneLimbs[1] = {1};

  out->d = (BN_ULONG *)kOneLimbs;

  out->width = 1;

  out->dmax = 1;

  out->neg = 0;

  out->flags = BN_FLG_STATIC_DATA;

}

// BN_num_bits_word returns the minimum number of bits needed to represent the

// value in |l|.

unsigned BN_num_bits_word(BN_ULONG l) {

  // |BN_num_bits| is often called on RSA prime factors. These have public bit

  // lengths, but all bits beyond the high bit are secret, so count bits in

  // constant time.

  BN_ULONG x, mask;

  int bits = (l != 0);

#if BN_BITS2 > 32

  // Look at the upper half of |x|. |x| is at most 64 bits long.

  x = l >> 32;

  // Set |mask| to all ones if |x| (the top 32 bits of |l|) is non-zero and all

  // all zeros otherwise.

  mask = 0u - x;

  mask = (0u - (mask >> (BN_BITS2 - 1)));

  // If |x| is non-zero, the lower half is included in the bit count in full,

  // and we count the upper half. Otherwise, we count the lower half.

  bits += 32 & mask;

  l ^= (x ^ l) & mask;  // |l| is |x| if |mask| and remains |l| otherwise.

#endif

  // The remaining blocks are analogous iterations at lower powers of two.

  x = l >> 16;

  mask = 0u - x;

  mask = (0u - (mask >> (BN_BITS2 - 1)));

  bits += 16 & mask;

  l ^= (x ^ l) & mask;

  x = l >> 8;

  mask = 0u - x;

  mask = (0u - (mask >> (BN_BITS2 - 1)));

  bits += 8 & mask;

  l ^= (x ^ l) & mask;

  x = l >> 4;

  mask = 0u - x;

  mask = (0u - (mask >> (BN_BITS2 - 1)));

  bits += 4 & mask;

  l ^= (x ^ l) & mask;

  x = l >> 2;

  mask = 0u - x;

  mask = (0u - (mask >> (BN_BITS2 - 1)));

  bits += 2 & mask;

  l ^= (x ^ l) & mask;

  x = l >> 1;

  mask = 0u - x;

  mask = (0u - (mask >> (BN_BITS2 - 1)));

  bits += 1 & mask;

  return bits;

}

unsigned BN_num_bits(const BIGNUM *bn) {

  const int width = bn_minimal_width(bn);

  if (width == 0) {

    return 0;

  }

  return (width - 1) * BN_BITS2 + BN_num_bits_word(bn->d[width - 1]);

}

unsigned BN_num_bytes(const BIGNUM *bn) { return (BN_num_bits(bn) + 7) / 8; }

void BN_zero(BIGNUM *bn) { bn->width = bn->neg = 0; }

int BN_one(BIGNUM *bn) { return BN_set_word(bn, 1); }

int BN_set_word(BIGNUM *bn, BN_ULONG value) {

  if (value == 0) {

    BN_zero(bn);

    return 1;

  }

  if (!bn_wexpand(bn, 1)) {

    return 0;

  }

  bn->neg = 0;

  bn->d[0] = value;

  bn->width = 1;

  return 1;

}

int BN_set_u64(BIGNUM *bn, uint64_t value) {

#if BN_BITS2 == 64

  return BN_set_word(bn, value);

#elif BN_BITS2 == 32

  if (value <= BN_MASK2) {

    return BN_set_word(bn, (BN_ULONG)value);

  }

  if (!bn_wexpand(bn, 2)) {

    return 0;

  }

  bn->neg = 0;

  bn->d[0] = (BN_ULONG)value;

  bn->d[1] = (BN_ULONG)(value >> 32);

  bn->width = 2;

  return 1;

#else

#error "BN_BITS2 must be 32 or 64."

#endif

}

int bn_set_words(BIGNUM *bn, const BN_ULONG *words, size_t num) {

  if (!bn_wexpand(bn, num)) {

    return 0;

  }

  OPENSSL_memmove(bn->d, words, num * sizeof(BN_ULONG));

  // |bn_wexpand| verified that |num| isn't too large.

  bn->width = (int)num;

  bn->neg = 0;

  return 1;

}

void bn_set_static_words(BIGNUM *bn, const BN_ULONG *words, size_t num) {

  if ((bn->flags & BN_FLG_STATIC_DATA) == 0) {

    OPENSSL_free(bn->d);

  }

  bn->d = (BN_ULONG *)words;

  assert(num <= BN_MAX_WORDS);

  bn->width = (int)num;

  bn->dmax = (int)num;

  bn->neg = 0;

  bn->flags |= BN_FLG_STATIC_DATA;

}

int bn_fits_in_words(const BIGNUM *bn, size_t num) {

  // All words beyond |num| must be zero.

  BN_ULONG mask = 0;

  for (size_t i = num; i < (size_t)bn->width; i++) {

    mask |= bn->d[i];

  }

  return mask == 0;

}

int bn_copy_words(BN_ULONG *out, size_t num, const BIGNUM *bn) {

  if (bn->neg) {

    OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);

    return 0;

  }

  size_t width = (size_t)bn->width;

  if (width > num) {

    if (!bn_fits_in_words(bn, num)) {

      OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);

      return 0;

    }

    width = num;

  }

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

  OPENSSL_memcpy(out, bn->d, sizeof(BN_ULONG) * width);

  return 1;

}

int BN_is_negative(const BIGNUM *bn) { return bn->neg != 0; }

void BN_set_negative(BIGNUM *bn, int sign) {

  if (sign && !BN_is_zero(bn)) {

    bn->neg = 1;

  } else {

    bn->neg = 0;

  }

}

int bn_wexpand(BIGNUM *bn, size_t words) {

  BN_ULONG *a;

  if (words <= (size_t)bn->dmax) {

    return 1;

  }

  if (words > BN_MAX_WORDS) {

    OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);

    return 0;

  }

  if (bn->flags & BN_FLG_STATIC_DATA) {

    OPENSSL_PUT_ERROR(BN, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);

    return 0;

  }

  a = reinterpret_cast<BN_ULONG *>(OPENSSL_calloc(words, sizeof(BN_ULONG)));

  if (a == NULL) {

    return 0;

  }

  OPENSSL_memcpy(a, bn->d, sizeof(BN_ULONG) * bn->width);

  OPENSSL_free(bn->d);

  bn->d = a;

  bn->dmax = (int)words;

  return 1;

}

int bn_expand(BIGNUM *bn, size_t bits) {

  if (bits + BN_BITS2 - 1 < bits) {

    OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);

    return 0;

  }

  return bn_wexpand(bn, (bits + BN_BITS2 - 1) / BN_BITS2);

}

int bn_resize_words(BIGNUM *bn, size_t words) {

  if ((size_t)bn->width <= words) {

    if (!bn_wexpand(bn, words)) {

      return 0;

    }

    OPENSSL_memset(bn->d + bn->width, 0,

                   (words - bn->width) * sizeof(BN_ULONG));

    bn->width = (int)words;

    return 1;

  }

  // All words beyond the new width must be zero.

  if (!bn_fits_in_words(bn, words)) {

    OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);

    return 0;

  }

  bn->width = (int)words;

  return 1;

}

void bn_select_words(BN_ULONG *r, BN_ULONG mask, const BN_ULONG *a,

                     const BN_ULONG *b, size_t num) {

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

    static_assert(sizeof(BN_ULONG) <= sizeof(crypto_word_t),

                  "crypto_word_t is too small");

    r[i] = constant_time_select_w(mask, a[i], b[i]);

  }

}

int bn_minimal_width(const BIGNUM *bn) {

  int ret = bn->width;

  while (ret > 0 && bn->d[ret - 1] == 0) {

    ret--;

  }

  return ret;

}

void bn_set_minimal_width(BIGNUM *bn) {

  bn->width = bn_minimal_width(bn);

  if (bn->width == 0) {

    bn->neg = 0;

  }

}