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0f113f3e | 1 | /* |
4f22f405 | 2 | * Copyright 1998-2016 The OpenSSL Project Authors. All Rights Reserved. |
0f113f3e | 3 | * |
4f22f405 RS |
4 | * Licensed under the OpenSSL license (the "License"). You may not use |
5 | * this file except in compliance with the License. You can obtain a copy | |
6 | * in the file LICENSE in the source distribution or at | |
7 | * https://www.openssl.org/source/license.html | |
535b9b57 BM |
8 | */ |
9 | ||
b39fc560 | 10 | #include "internal/cryptlib.h" |
535b9b57 BM |
11 | #include "bn_lcl.h" |
12 | ||
5acaa495 | 13 | int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx) |
0f113f3e MC |
14 | { |
15 | /* | |
16 | * like BN_mod, but returns non-negative remainder (i.e., 0 <= r < |d| | |
17 | * always holds) | |
18 | */ | |
19 | ||
20 | if (!(BN_mod(r, m, d, ctx))) | |
21 | return 0; | |
22 | if (!r->neg) | |
23 | return 1; | |
24 | /* now -|d| < r < 0, so we have to set r := r + |d| */ | |
25 | return (d->neg ? BN_sub : BN_add) (r, r, d); | |
535b9b57 BM |
26 | } |
27 | ||
0f113f3e MC |
28 | int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, |
29 | BN_CTX *ctx) | |
30 | { | |
31 | if (!BN_add(r, a, b)) | |
32 | return 0; | |
33 | return BN_nnmod(r, r, m, ctx); | |
34 | } | |
535b9b57 | 35 | |
0f113f3e MC |
36 | /* |
37 | * BN_mod_add variant that may be used if both a and b are non-negative and | |
38 | * less than m | |
39 | */ | |
40 | int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, | |
41 | const BIGNUM *m) | |
42 | { | |
43 | if (!BN_uadd(r, a, b)) | |
44 | return 0; | |
45 | if (BN_ucmp(r, m) >= 0) | |
46 | return BN_usub(r, r, m); | |
47 | return 1; | |
48 | } | |
5acaa495 | 49 | |
0f113f3e MC |
50 | int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, |
51 | BN_CTX *ctx) | |
52 | { | |
53 | if (!BN_sub(r, a, b)) | |
54 | return 0; | |
55 | return BN_nnmod(r, r, m, ctx); | |
56 | } | |
535b9b57 | 57 | |
0f113f3e MC |
58 | /* |
59 | * BN_mod_sub variant that may be used if both a and b are non-negative and | |
60 | * less than m | |
61 | */ | |
62 | int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, | |
63 | const BIGNUM *m) | |
64 | { | |
65 | if (!BN_sub(r, a, b)) | |
66 | return 0; | |
67 | if (r->neg) | |
68 | return BN_add(r, r, m); | |
69 | return 1; | |
70 | } | |
535b9b57 BM |
71 | |
72 | /* slow but works */ | |
5acaa495 | 73 | int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, |
0f113f3e MC |
74 | BN_CTX *ctx) |
75 | { | |
76 | BIGNUM *t; | |
77 | int ret = 0; | |
78 | ||
79 | bn_check_top(a); | |
80 | bn_check_top(b); | |
81 | bn_check_top(m); | |
82 | ||
83 | BN_CTX_start(ctx); | |
84 | if ((t = BN_CTX_get(ctx)) == NULL) | |
85 | goto err; | |
86 | if (a == b) { | |
87 | if (!BN_sqr(t, a, ctx)) | |
88 | goto err; | |
89 | } else { | |
90 | if (!BN_mul(t, a, b, ctx)) | |
91 | goto err; | |
92 | } | |
93 | if (!BN_nnmod(r, t, m, ctx)) | |
94 | goto err; | |
95 | bn_check_top(r); | |
96 | ret = 1; | |
97 | err: | |
98 | BN_CTX_end(ctx); | |
99 | return (ret); | |
100 | } | |
535b9b57 | 101 | |
5acaa495 | 102 | int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) |
0f113f3e MC |
103 | { |
104 | if (!BN_sqr(r, a, ctx)) | |
105 | return 0; | |
106 | /* r->neg == 0, thus we don't need BN_nnmod */ | |
107 | return BN_mod(r, r, m, ctx); | |
108 | } | |
5acaa495 BM |
109 | |
110 | int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) | |
0f113f3e MC |
111 | { |
112 | if (!BN_lshift1(r, a)) | |
113 | return 0; | |
114 | bn_check_top(r); | |
115 | return BN_nnmod(r, r, m, ctx); | |
116 | } | |
5acaa495 | 117 | |
0f113f3e MC |
118 | /* |
119 | * BN_mod_lshift1 variant that may be used if a is non-negative and less than | |
120 | * m | |
121 | */ | |
5acaa495 | 122 | int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m) |
0f113f3e MC |
123 | { |
124 | if (!BN_lshift1(r, a)) | |
125 | return 0; | |
126 | bn_check_top(r); | |
127 | if (BN_cmp(r, m) >= 0) | |
128 | return BN_sub(r, r, m); | |
129 | return 1; | |
130 | } | |
5acaa495 | 131 | |
0f113f3e MC |
132 | int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, |
133 | BN_CTX *ctx) | |
134 | { | |
135 | BIGNUM *abs_m = NULL; | |
136 | int ret; | |
5acaa495 | 137 | |
0f113f3e MC |
138 | if (!BN_nnmod(r, a, m, ctx)) |
139 | return 0; | |
5acaa495 | 140 | |
0f113f3e MC |
141 | if (m->neg) { |
142 | abs_m = BN_dup(m); | |
143 | if (abs_m == NULL) | |
144 | return 0; | |
145 | abs_m->neg = 0; | |
146 | } | |
5acaa495 | 147 | |
0f113f3e MC |
148 | ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m)); |
149 | bn_check_top(r); | |
5acaa495 | 150 | |
23a1d5e9 | 151 | BN_free(abs_m); |
0f113f3e MC |
152 | return ret; |
153 | } | |
5acaa495 | 154 | |
0f113f3e MC |
155 | /* |
156 | * BN_mod_lshift variant that may be used if a is non-negative and less than | |
157 | * m | |
158 | */ | |
5acaa495 | 159 | int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m) |
0f113f3e MC |
160 | { |
161 | if (r != a) { | |
162 | if (BN_copy(r, a) == NULL) | |
163 | return 0; | |
164 | } | |
165 | ||
166 | while (n > 0) { | |
167 | int max_shift; | |
168 | ||
169 | /* 0 < r < m */ | |
170 | max_shift = BN_num_bits(m) - BN_num_bits(r); | |
171 | /* max_shift >= 0 */ | |
172 | ||
173 | if (max_shift < 0) { | |
174 | BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED); | |
175 | return 0; | |
176 | } | |
177 | ||
178 | if (max_shift > n) | |
179 | max_shift = n; | |
180 | ||
181 | if (max_shift) { | |
182 | if (!BN_lshift(r, r, max_shift)) | |
183 | return 0; | |
184 | n -= max_shift; | |
185 | } else { | |
186 | if (!BN_lshift1(r, r)) | |
187 | return 0; | |
188 | --n; | |
189 | } | |
190 | ||
191 | /* BN_num_bits(r) <= BN_num_bits(m) */ | |
192 | ||
193 | if (BN_cmp(r, m) >= 0) { | |
194 | if (!BN_sub(r, r, m)) | |
195 | return 0; | |
196 | } | |
197 | } | |
198 | bn_check_top(r); | |
199 | ||
200 | return 1; | |
201 | } |