1/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young (eay@cryptsoft.com)"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57#include <openssl/bn.h>
58
59#include <openssl/mem.h>
60#include <openssl/type_check.h>
61
62#include "internal.h"
63#include "../../internal.h"
64
65
66static int bn_cmp_words_consttime(const BN_ULONG *a, size_t a_len,
67 const BN_ULONG *b, size_t b_len) {
68 OPENSSL_STATIC_ASSERT(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
69 "crypto_word_t is too small");
70 int ret = 0;
71 // Process the common words in little-endian order.
72 size_t min = a_len < b_len ? a_len : b_len;
73 for (size_t i = 0; i < min; i++) {
74 crypto_word_t eq = constant_time_eq_w(a[i], b[i]);
75 crypto_word_t lt = constant_time_lt_w(a[i], b[i]);
76 ret =
77 constant_time_select_int(eq, ret, constant_time_select_int(lt, -1, 1));
78 }
79
80 // If |a| or |b| has non-zero words beyond |min|, they take precedence.
81 if (a_len < b_len) {
82 crypto_word_t mask = 0;
83 for (size_t i = a_len; i < b_len; i++) {
84 mask |= b[i];
85 }
86 ret = constant_time_select_int(constant_time_is_zero_w(mask), ret, -1);
87 } else if (b_len < a_len) {
88 crypto_word_t mask = 0;
89 for (size_t i = b_len; i < a_len; i++) {
90 mask |= a[i];
91 }
92 ret = constant_time_select_int(constant_time_is_zero_w(mask), ret, 1);
93 }
94
95 return ret;
96}
97
98int BN_ucmp(const BIGNUM *a, const BIGNUM *b) {
99 return bn_cmp_words_consttime(a->d, a->width, b->d, b->width);
100}
101
102int BN_cmp(const BIGNUM *a, const BIGNUM *b) {
103 if ((a == NULL) || (b == NULL)) {
104 if (a != NULL) {
105 return -1;
106 } else if (b != NULL) {
107 return 1;
108 } else {
109 return 0;
110 }
111 }
112
113 // We do not attempt to process the sign bit in constant time. Negative
114 // |BIGNUM|s should never occur in crypto, only calculators.
115 if (a->neg != b->neg) {
116 if (a->neg) {
117 return -1;
118 }
119 return 1;
120 }
121
122 int ret = BN_ucmp(a, b);
123 return a->neg ? -ret : ret;
124}
125
126int bn_less_than_words(const BN_ULONG *a, const BN_ULONG *b, size_t len) {
127 return bn_cmp_words_consttime(a, len, b, len) < 0;
128}
129
130int BN_abs_is_word(const BIGNUM *bn, BN_ULONG w) {
131 if (bn->width == 0) {
132 return w == 0;
133 }
134 BN_ULONG mask = bn->d[0] ^ w;
135 for (int i = 1; i < bn->width; i++) {
136 mask |= bn->d[i];
137 }
138 return mask == 0;
139}
140
141int BN_cmp_word(const BIGNUM *a, BN_ULONG b) {
142 BIGNUM b_bn;
143 BN_init(&b_bn);
144
145 b_bn.d = &b;
146 b_bn.width = b > 0;
147 b_bn.dmax = 1;
148 b_bn.flags = BN_FLG_STATIC_DATA;
149 return BN_cmp(a, &b_bn);
150}
151
152int BN_is_zero(const BIGNUM *bn) {
153 return bn_fits_in_words(bn, 0);
154}
155
156int BN_is_one(const BIGNUM *bn) {
157 return bn->neg == 0 && BN_abs_is_word(bn, 1);
158}
159
160int BN_is_word(const BIGNUM *bn, BN_ULONG w) {
161 return BN_abs_is_word(bn, w) && (w == 0 || bn->neg == 0);
162}
163
164int BN_is_odd(const BIGNUM *bn) {
165 return bn->width > 0 && (bn->d[0] & 1) == 1;
166}
167
168int BN_is_pow2(const BIGNUM *bn) {
169 int width = bn_minimal_width(bn);
170 if (width == 0 || bn->neg) {
171 return 0;
172 }
173
174 for (int i = 0; i < width - 1; i++) {
175 if (bn->d[i] != 0) {
176 return 0;
177 }
178 }
179
180 return 0 == (bn->d[width-1] & (bn->d[width-1] - 1));
181}
182
183int BN_equal_consttime(const BIGNUM *a, const BIGNUM *b) {
184 BN_ULONG mask = 0;
185 // If |a| or |b| has more words than the other, all those words must be zero.
186 for (int i = a->width; i < b->width; i++) {
187 mask |= b->d[i];
188 }
189 for (int i = b->width; i < a->width; i++) {
190 mask |= a->d[i];
191 }
192 // Common words must match.
193 int min = a->width < b->width ? a->width : b->width;
194 for (int i = 0; i < min; i++) {
195 mask |= (a->d[i] ^ b->d[i]);
196 }
197 // The sign bit must match.
198 mask |= (a->neg ^ b->neg);
199 return mask == 0;
200}
201