ref: e86bd6a50933e99899d63de755d81b9805827a15
dir: /third_party/boringssl/src/crypto/fipsmodule/bn/add.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 <string.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include "internal.h"
int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
const BIGNUM *tmp;
int a_neg = a->neg, ret;
// a + b a+b
// a + -b a-b
// -a + b b-a
// -a + -b -(a+b)
if (a_neg ^ b->neg) {
// only one is negative
if (a_neg) {
tmp = a;
a = b;
b = tmp;
}
// we are now a - b
if (BN_ucmp(a, b) < 0) {
if (!BN_usub(r, b, a)) {
return 0;
}
r->neg = 1;
} else {
if (!BN_usub(r, a, b)) {
return 0;
}
r->neg = 0;
}
return 1;
}
ret = BN_uadd(r, a, b);
r->neg = a_neg;
return ret;
}
int bn_uadd_consttime(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
// Widths are public, so we normalize to make |a| the larger one.
if (a->width < b->width) {
const BIGNUM *tmp = a;
a = b;
b = tmp;
}
int max = a->width;
int min = b->width;
if (!bn_wexpand(r, max + 1)) {
return 0;
}
r->width = max + 1;
BN_ULONG carry = bn_add_words(r->d, a->d, b->d, min);
for (int i = min; i < max; i++) {
// |r| and |a| may alias, so use a temporary.
BN_ULONG tmp = carry + a->d[i];
carry = tmp < a->d[i];
r->d[i] = tmp;
}
r->d[max] = carry;
return 1;
}
int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
if (!bn_uadd_consttime(r, a, b)) {
return 0;
}
bn_set_minimal_width(r);
return 1;
}
int BN_add_word(BIGNUM *a, BN_ULONG w) {
BN_ULONG l;
int i;
// degenerate case: w is zero
if (!w) {
return 1;
}
// degenerate case: a is zero
if (BN_is_zero(a)) {
return BN_set_word(a, w);
}
// handle 'a' when negative
if (a->neg) {
a->neg = 0;
i = BN_sub_word(a, w);
if (!BN_is_zero(a)) {
a->neg = !(a->neg);
}
return i;
}
for (i = 0; w != 0 && i < a->width; i++) {
a->d[i] = l = a->d[i] + w;
w = (w > l) ? 1 : 0;
}
if (w && i == a->width) {
if (!bn_wexpand(a, a->width + 1)) {
return 0;
}
a->width++;
a->d[i] = w;
}
return 1;
}
int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
int add = 0, neg = 0;
const BIGNUM *tmp;
// a - b a-b
// a - -b a+b
// -a - b -(a+b)
// -a - -b b-a
if (a->neg) {
if (b->neg) {
tmp = a;
a = b;
b = tmp;
} else {
add = 1;
neg = 1;
}
} else {
if (b->neg) {
add = 1;
neg = 0;
}
}
if (add) {
if (!BN_uadd(r, a, b)) {
return 0;
}
r->neg = neg;
return 1;
}
if (BN_ucmp(a, b) < 0) {
if (!BN_usub(r, b, a)) {
return 0;
}
r->neg = 1;
} else {
if (!BN_usub(r, a, b)) {
return 0;
}
r->neg = 0;
}
return 1;
}
int bn_usub_consttime(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
// |b| may have more words than |a| given non-minimal inputs, but all words
// beyond |a->width| must then be zero.
int b_width = b->width;
if (b_width > a->width) {
if (!bn_fits_in_words(b, a->width)) {
OPENSSL_PUT_ERROR(BN, BN_R_ARG2_LT_ARG3);
return 0;
}
b_width = a->width;
}
if (!bn_wexpand(r, a->width)) {
return 0;
}
BN_ULONG borrow = bn_sub_words(r->d, a->d, b->d, b_width);
for (int i = b_width; i < a->width; i++) {
// |r| and |a| may alias, so use a temporary.
BN_ULONG tmp = a->d[i];
r->d[i] = a->d[i] - borrow;
borrow = tmp < r->d[i];
}
if (borrow) {
OPENSSL_PUT_ERROR(BN, BN_R_ARG2_LT_ARG3);
return 0;
}
r->width = a->width;
r->neg = 0;
return 1;
}
int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
if (!bn_usub_consttime(r, a, b)) {
return 0;
}
bn_set_minimal_width(r);
return 1;
}
int BN_sub_word(BIGNUM *a, BN_ULONG w) {
int i;
// degenerate case: w is zero
if (!w) {
return 1;
}
// degenerate case: a is zero
if (BN_is_zero(a)) {
i = BN_set_word(a, w);
if (i != 0) {
BN_set_negative(a, 1);
}
return i;
}
// handle 'a' when negative
if (a->neg) {
a->neg = 0;
i = BN_add_word(a, w);
a->neg = 1;
return i;
}
if ((bn_minimal_width(a) == 1) && (a->d[0] < w)) {
a->d[0] = w - a->d[0];
a->neg = 1;
return 1;
}
i = 0;
for (;;) {
if (a->d[i] >= w) {
a->d[i] -= w;
break;
} else {
a->d[i] -= w;
i++;
w = 1;
}
}
if ((a->d[i] == 0) && (i == (a->width - 1))) {
a->width--;
}
return 1;
}