| // 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; |
| } |
| } |