1 /* Copyright (C) 1995-1998 Eric Young ([email protected])
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young ([email protected]).
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 ([email protected]).
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 ([email protected])"
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 ([email protected])"
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 <assert.h>
60
61 #include <openssl/mem.h>
62
63 #include "internal.h"
64 #include "../../internal.h"
65
66
bn_cmp_words_consttime(const BN_ULONG * a,size_t a_len,const BN_ULONG * b,size_t b_len)67 static int bn_cmp_words_consttime(const BN_ULONG *a, size_t a_len,
68 const BN_ULONG *b, size_t b_len) {
69 static_assert(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
70 "crypto_word_t is too small");
71 int ret = 0;
72 // Process the common words in little-endian order.
73 size_t min = a_len < b_len ? a_len : b_len;
74 for (size_t i = 0; i < min; i++) {
75 crypto_word_t eq = constant_time_eq_w(a[i], b[i]);
76 crypto_word_t lt = constant_time_lt_w(a[i], b[i]);
77 ret =
78 constant_time_select_int(eq, ret, constant_time_select_int(lt, -1, 1));
79 }
80
81 // If |a| or |b| has non-zero words beyond |min|, they take precedence.
82 if (a_len < b_len) {
83 crypto_word_t mask = 0;
84 for (size_t i = a_len; i < b_len; i++) {
85 mask |= b[i];
86 }
87 ret = constant_time_select_int(constant_time_is_zero_w(mask), ret, -1);
88 } else if (b_len < a_len) {
89 crypto_word_t mask = 0;
90 for (size_t i = b_len; i < a_len; i++) {
91 mask |= a[i];
92 }
93 ret = constant_time_select_int(constant_time_is_zero_w(mask), ret, 1);
94 }
95
96 return ret;
97 }
98
BN_ucmp(const BIGNUM * a,const BIGNUM * b)99 int BN_ucmp(const BIGNUM *a, const BIGNUM *b) {
100 return bn_cmp_words_consttime(a->d, a->width, b->d, b->width);
101 }
102
BN_cmp(const BIGNUM * a,const BIGNUM * b)103 int BN_cmp(const BIGNUM *a, const BIGNUM *b) {
104 if ((a == NULL) || (b == NULL)) {
105 if (a != NULL) {
106 return -1;
107 } else if (b != NULL) {
108 return 1;
109 } else {
110 return 0;
111 }
112 }
113
114 // We do not attempt to process the sign bit in constant time. Negative
115 // |BIGNUM|s should never occur in crypto, only calculators.
116 if (a->neg != b->neg) {
117 if (a->neg) {
118 return -1;
119 }
120 return 1;
121 }
122
123 int ret = BN_ucmp(a, b);
124 return a->neg ? -ret : ret;
125 }
126
bn_less_than_words(const BN_ULONG * a,const BN_ULONG * b,size_t len)127 int bn_less_than_words(const BN_ULONG *a, const BN_ULONG *b, size_t len) {
128 return bn_cmp_words_consttime(a, len, b, len) < 0;
129 }
130
BN_abs_is_word(const BIGNUM * bn,BN_ULONG w)131 int BN_abs_is_word(const BIGNUM *bn, BN_ULONG w) {
132 if (bn->width == 0) {
133 return w == 0;
134 }
135 BN_ULONG mask = bn->d[0] ^ w;
136 for (int i = 1; i < bn->width; i++) {
137 mask |= bn->d[i];
138 }
139 return mask == 0;
140 }
141
BN_cmp_word(const BIGNUM * a,BN_ULONG b)142 int BN_cmp_word(const BIGNUM *a, BN_ULONG b) {
143 BIGNUM b_bn;
144 BN_init(&b_bn);
145
146 b_bn.d = &b;
147 b_bn.width = b > 0;
148 b_bn.dmax = 1;
149 b_bn.flags = BN_FLG_STATIC_DATA;
150 return BN_cmp(a, &b_bn);
151 }
152
BN_is_zero(const BIGNUM * bn)153 int BN_is_zero(const BIGNUM *bn) {
154 return bn_fits_in_words(bn, 0);
155 }
156
BN_is_one(const BIGNUM * bn)157 int BN_is_one(const BIGNUM *bn) {
158 return bn->neg == 0 && BN_abs_is_word(bn, 1);
159 }
160
BN_is_word(const BIGNUM * bn,BN_ULONG w)161 int BN_is_word(const BIGNUM *bn, BN_ULONG w) {
162 return BN_abs_is_word(bn, w) && (w == 0 || bn->neg == 0);
163 }
164
BN_is_odd(const BIGNUM * bn)165 int BN_is_odd(const BIGNUM *bn) {
166 return bn->width > 0 && (bn->d[0] & 1) == 1;
167 }
168
BN_is_pow2(const BIGNUM * bn)169 int BN_is_pow2(const BIGNUM *bn) {
170 int width = bn_minimal_width(bn);
171 if (width == 0 || bn->neg) {
172 return 0;
173 }
174
175 for (int i = 0; i < width - 1; i++) {
176 if (bn->d[i] != 0) {
177 return 0;
178 }
179 }
180
181 return 0 == (bn->d[width-1] & (bn->d[width-1] - 1));
182 }
183
BN_equal_consttime(const BIGNUM * a,const BIGNUM * b)184 int BN_equal_consttime(const BIGNUM *a, const BIGNUM *b) {
185 BN_ULONG mask = 0;
186 // If |a| or |b| has more words than the other, all those words must be zero.
187 for (int i = a->width; i < b->width; i++) {
188 mask |= b->d[i];
189 }
190 for (int i = b->width; i < a->width; i++) {
191 mask |= a->d[i];
192 }
193 // Common words must match.
194 int min = a->width < b->width ? a->width : b->width;
195 for (int i = 0; i < min; i++) {
196 mask |= (a->d[i] ^ b->d[i]);
197 }
198 // The sign bit must match.
199 mask |= (a->neg ^ b->neg);
200 return mask == 0;
201 }
202