ref: 2bbc75bddc6f2a07056ff017108e35f14061041b
dir: /third_party/boringssl/src/crypto/fipsmodule/bn/cmp.c/
/* 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 <openssl/mem.h>
#include <openssl/type_check.h>
#include "internal.h"
#include "../../internal.h"
static int bn_cmp_words_consttime(const BN_ULONG *a, size_t a_len,
const BN_ULONG *b, size_t b_len) {
OPENSSL_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 == NULL) || (b == NULL)) {
if (a != NULL) {
return -1;
} else if (b != NULL) {
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 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;
}