--- /dev/null
+/* 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;
+}
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