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// 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 <contrib/restricted/google/boringssl/include/openssl/bn.h>
#include <assert.h>
#include <contrib/restricted/google/boringssl/include/openssl/mem.h>
#include "internal.h"
#include "../../internal.h"
using namespace bssl;
static int bn_cmp_words_consttime(const BN_ULONG *a, size_t a_len,
const BN_ULONG *b, size_t b_len) {
static_assert(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
"crypto_word_t is too small");
int ret = 0;
// Process the common words in little-endian order.
size_t min = a_len < b_len ? a_len : b_len;
for (size_t i = 0; i < min; i++) {
crypto_word_t eq = constant_time_eq_w(a[i], b[i]);
crypto_word_t lt = constant_time_lt_w(a[i], b[i]);
ret =
constant_time_select_int(eq, ret, constant_time_select_int(lt, -1, 1));
}
// If |a| or |b| has non-zero words beyond |min|, they take precedence.
if (a_len < b_len) {
crypto_word_t mask = 0;
for (size_t i = a_len; i < b_len; i++) {
mask |= b[i];
}
ret = constant_time_select_int(constant_time_is_zero_w(mask), ret, -1);
} else if (b_len < a_len) {
crypto_word_t mask = 0;
for (size_t i = b_len; i < a_len; i++) {
mask |= a[i];
}
ret = constant_time_select_int(constant_time_is_zero_w(mask), ret, 1);
}
return ret;
}
int BN_ucmp(const BIGNUM *a, const BIGNUM *b) {
return bn_cmp_words_consttime(a->d, a->width, b->d, b->width);
}
int BN_cmp(const BIGNUM *a, const BIGNUM *b) {
if ((a == nullptr) || (b == nullptr)) {
if (a != nullptr) {
return -1;
} else if (b != nullptr) {
return 1;
} else {
return 0;
}
}
// We do not attempt to process the sign bit in constant time. Negative
// |BIGNUM|s should never occur in crypto, only calculators.
if (a->neg != b->neg) {
if (a->neg) {
return -1;
}
return 1;
}
int ret = BN_ucmp(a, b);
return a->neg ? -ret : ret;
}
int bssl::bn_less_than_words(const BN_ULONG *a, const BN_ULONG *b, size_t len) {
return bn_cmp_words_consttime(a, len, b, len) < 0;
}
int BN_abs_is_word(const BIGNUM *bn, BN_ULONG w) {
if (bn->width == 0) {
return w == 0;
}
BN_ULONG mask = bn->d[0] ^ w;
for (int i = 1; i < bn->width; i++) {
mask |= bn->d[i];
}
return mask == 0;
}
int BN_cmp_word(const BIGNUM *a, BN_ULONG b) {
BIGNUM b_bn;
BN_init(&b_bn);
b_bn.d = &b;
b_bn.width = b > 0;
b_bn.dmax = 1;
b_bn.flags = BN_FLG_STATIC_DATA;
return BN_cmp(a, &b_bn);
}
int BN_is_zero(const BIGNUM *bn) {
return bn_fits_in_words(bn, 0);
}
int BN_is_one(const BIGNUM *bn) {
return bn->neg == 0 && BN_abs_is_word(bn, 1);
}
int BN_is_word(const BIGNUM *bn, BN_ULONG w) {
return BN_abs_is_word(bn, w) && (w == 0 || bn->neg == 0);
}
int BN_is_odd(const BIGNUM *bn) {
return bn->width > 0 && (bn->d[0] & 1) == 1;
}
int BN_is_pow2(const BIGNUM *bn) {
int width = bn_minimal_width(bn);
if (width == 0 || bn->neg) {
return 0;
}
for (int i = 0; i < width - 1; i++) {
if (bn->d[i] != 0) {
return 0;
}
}
return 0 == (bn->d[width-1] & (bn->d[width-1] - 1));
}
int BN_equal_consttime(const BIGNUM *a, const BIGNUM *b) {
BN_ULONG mask = 0;
// If |a| or |b| has more words than the other, all those words must be zero.
for (int i = a->width; i < b->width; i++) {
mask |= b->d[i];
}
for (int i = b->width; i < a->width; i++) {
mask |= a->d[i];
}
// Common words must match.
int min = a->width < b->width ? a->width : b->width;
for (int i = 0; i < min; i++) {
mask |= (a->d[i] ^ b->d[i]);
}
// The sign bit must match.
mask |= (a->neg ^ b->neg);
return mask == 0;
}
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