]>
Commit | Line | Data |
---|---|---|
4f22f405 | 1 | /* |
da1c088f | 2 | * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved. |
d02b48c6 | 3 | * |
367ace68 | 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use |
4f22f405 RS |
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 | |
d02b48c6 RE |
8 | */ |
9 | ||
b39fc560 | 10 | #include "internal/cryptlib.h" |
706457b7 | 11 | #include "bn_local.h" |
d02b48c6 | 12 | |
6b691a5c | 13 | void BN_RECP_CTX_init(BN_RECP_CTX *recp) |
0f113f3e | 14 | { |
318447bc | 15 | memset(recp, 0, sizeof(*recp)); |
d59c7c81 RS |
16 | bn_init(&(recp->N)); |
17 | bn_init(&(recp->Nr)); | |
0f113f3e | 18 | } |
dfeab068 | 19 | |
6b691a5c | 20 | BN_RECP_CTX *BN_RECP_CTX_new(void) |
0f113f3e MC |
21 | { |
22 | BN_RECP_CTX *ret; | |
dfeab068 | 23 | |
e077455e | 24 | if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) |
26a7d938 | 25 | return NULL; |
dfeab068 | 26 | |
318447bc F |
27 | bn_init(&(ret->N)); |
28 | bn_init(&(ret->Nr)); | |
0f113f3e | 29 | ret->flags = BN_FLG_MALLOCED; |
26a7d938 | 30 | return ret; |
0f113f3e | 31 | } |
dfeab068 | 32 | |
6b691a5c | 33 | void BN_RECP_CTX_free(BN_RECP_CTX *recp) |
0f113f3e | 34 | { |
e6e9170d RS |
35 | if (recp == NULL) |
36 | return; | |
37 | BN_free(&recp->N); | |
38 | BN_free(&recp->Nr); | |
0f113f3e MC |
39 | if (recp->flags & BN_FLG_MALLOCED) |
40 | OPENSSL_free(recp); | |
41 | } | |
dfeab068 | 42 | |
84c15db5 | 43 | int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) |
0f113f3e | 44 | { |
43596b30 | 45 | if (BN_is_zero(d) || !BN_copy(&(recp->N), d)) |
0f113f3e MC |
46 | return 0; |
47 | BN_zero(&(recp->Nr)); | |
48 | recp->num_bits = BN_num_bits(d); | |
49 | recp->shift = 0; | |
208fb891 | 50 | return 1; |
0f113f3e | 51 | } |
dfeab068 | 52 | |
020fc820 | 53 | int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, |
0f113f3e MC |
54 | BN_RECP_CTX *recp, BN_CTX *ctx) |
55 | { | |
56 | int ret = 0; | |
57 | BIGNUM *a; | |
58 | const BIGNUM *ca; | |
59 | ||
60 | BN_CTX_start(ctx); | |
61 | if ((a = BN_CTX_get(ctx)) == NULL) | |
62 | goto err; | |
63 | if (y != NULL) { | |
64 | if (x == y) { | |
65 | if (!BN_sqr(a, x, ctx)) | |
66 | goto err; | |
67 | } else { | |
68 | if (!BN_mul(a, x, y, ctx)) | |
69 | goto err; | |
70 | } | |
71 | ca = a; | |
72 | } else | |
73 | ca = x; /* Just do the mod */ | |
74 | ||
75 | ret = BN_div_recp(NULL, r, ca, recp, ctx); | |
76 | err: | |
77 | BN_CTX_end(ctx); | |
78 | bn_check_top(r); | |
26a7d938 | 79 | return ret; |
0f113f3e | 80 | } |
dfeab068 | 81 | |
020fc820 | 82 | int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, |
0f113f3e MC |
83 | BN_RECP_CTX *recp, BN_CTX *ctx) |
84 | { | |
85 | int i, j, ret = 0; | |
86 | BIGNUM *a, *b, *d, *r; | |
87 | ||
88 | BN_CTX_start(ctx); | |
edea42c6 PY |
89 | d = (dv != NULL) ? dv : BN_CTX_get(ctx); |
90 | r = (rem != NULL) ? rem : BN_CTX_get(ctx); | |
0f113f3e MC |
91 | a = BN_CTX_get(ctx); |
92 | b = BN_CTX_get(ctx); | |
edea42c6 | 93 | if (b == NULL) |
0f113f3e MC |
94 | goto err; |
95 | ||
96 | if (BN_ucmp(m, &(recp->N)) < 0) { | |
97 | BN_zero(d); | |
3f6c7691 AG |
98 | if (!BN_copy(r, m)) { |
99 | BN_CTX_end(ctx); | |
0f113f3e | 100 | return 0; |
3f6c7691 | 101 | } |
0f113f3e | 102 | BN_CTX_end(ctx); |
208fb891 | 103 | return 1; |
0f113f3e MC |
104 | } |
105 | ||
106 | /* | |
107 | * We want the remainder Given input of ABCDEF / ab we need multiply | |
108 | * ABCDEF by 3 digests of the reciprocal of ab | |
109 | */ | |
110 | ||
111 | /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ | |
112 | i = BN_num_bits(m); | |
113 | j = recp->num_bits << 1; | |
114 | if (j > i) | |
115 | i = j; | |
116 | ||
117 | /* Nr := round(2^i / N) */ | |
118 | if (i != recp->shift) | |
119 | recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx); | |
120 | /* BN_reciprocal could have returned -1 for an error */ | |
121 | if (recp->shift == -1) | |
122 | goto err; | |
dfeab068 | 123 | |
e95bbc3c AP |
124 | /*- |
125 | * d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| | |
126 | * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| | |
127 | * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| | |
128 | * = |m/N| | |
129 | */ | |
0f113f3e MC |
130 | if (!BN_rshift(a, m, recp->num_bits)) |
131 | goto err; | |
132 | if (!BN_mul(b, a, &(recp->Nr), ctx)) | |
133 | goto err; | |
134 | if (!BN_rshift(d, b, i - recp->num_bits)) | |
135 | goto err; | |
136 | d->neg = 0; | |
137 | ||
138 | if (!BN_mul(b, &(recp->N), d, ctx)) | |
139 | goto err; | |
140 | if (!BN_usub(r, m, b)) | |
141 | goto err; | |
142 | r->neg = 0; | |
dfeab068 | 143 | |
0f113f3e MC |
144 | j = 0; |
145 | while (BN_ucmp(r, &(recp->N)) >= 0) { | |
146 | if (j++ > 2) { | |
9311d0c4 | 147 | ERR_raise(ERR_LIB_BN, BN_R_BAD_RECIPROCAL); |
0f113f3e MC |
148 | goto err; |
149 | } | |
150 | if (!BN_usub(r, r, &(recp->N))) | |
151 | goto err; | |
152 | if (!BN_add_word(d, 1)) | |
153 | goto err; | |
154 | } | |
d02b48c6 | 155 | |
0f113f3e MC |
156 | r->neg = BN_is_zero(r) ? 0 : m->neg; |
157 | d->neg = m->neg ^ recp->N.neg; | |
158 | ret = 1; | |
159 | err: | |
160 | BN_CTX_end(ctx); | |
161 | bn_check_top(dv); | |
162 | bn_check_top(rem); | |
26a7d938 | 163 | return ret; |
0f113f3e MC |
164 | } |
165 | ||
166 | /* | |
167 | * len is the expected size of the result We actually calculate with an extra | |
168 | * word of precision, so we can do faster division if the remainder is not | |
169 | * required. | |
dfeab068 | 170 | */ |
78a0c1f1 | 171 | /* r := 2^len / m */ |
6343829a | 172 | int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) |
0f113f3e MC |
173 | { |
174 | int ret = -1; | |
175 | BIGNUM *t; | |
176 | ||
177 | BN_CTX_start(ctx); | |
178 | if ((t = BN_CTX_get(ctx)) == NULL) | |
179 | goto err; | |
180 | ||
181 | if (!BN_set_bit(t, len)) | |
182 | goto err; | |
183 | ||
184 | if (!BN_div(r, NULL, t, m, ctx)) | |
185 | goto err; | |
186 | ||
187 | ret = len; | |
188 | err: | |
189 | bn_check_top(r); | |
190 | BN_CTX_end(ctx); | |
26a7d938 | 191 | return ret; |
0f113f3e | 192 | } |