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Commit | Line | Data |
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4f22f405 | 1 | /* |
c4d3c19b | 2 | * Copyright 1995-2018 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 | |
f06080cb F |
24 | if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) { |
25 | BNerr(BN_F_BN_RECP_CTX_NEW, ERR_R_MALLOC_FAILURE); | |
26a7d938 | 26 | return NULL; |
f06080cb | 27 | } |
dfeab068 | 28 | |
318447bc F |
29 | bn_init(&(ret->N)); |
30 | bn_init(&(ret->Nr)); | |
0f113f3e | 31 | ret->flags = BN_FLG_MALLOCED; |
26a7d938 | 32 | return ret; |
0f113f3e | 33 | } |
dfeab068 | 34 | |
6b691a5c | 35 | void BN_RECP_CTX_free(BN_RECP_CTX *recp) |
0f113f3e | 36 | { |
e6e9170d RS |
37 | if (recp == NULL) |
38 | return; | |
39 | BN_free(&recp->N); | |
40 | BN_free(&recp->Nr); | |
0f113f3e MC |
41 | if (recp->flags & BN_FLG_MALLOCED) |
42 | OPENSSL_free(recp); | |
43 | } | |
dfeab068 | 44 | |
84c15db5 | 45 | int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) |
0f113f3e MC |
46 | { |
47 | if (!BN_copy(&(recp->N), d)) | |
48 | return 0; | |
49 | BN_zero(&(recp->Nr)); | |
50 | recp->num_bits = BN_num_bits(d); | |
51 | recp->shift = 0; | |
208fb891 | 52 | return 1; |
0f113f3e | 53 | } |
dfeab068 | 54 | |
020fc820 | 55 | int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, |
0f113f3e MC |
56 | BN_RECP_CTX *recp, BN_CTX *ctx) |
57 | { | |
58 | int ret = 0; | |
59 | BIGNUM *a; | |
60 | const BIGNUM *ca; | |
61 | ||
62 | BN_CTX_start(ctx); | |
63 | if ((a = BN_CTX_get(ctx)) == NULL) | |
64 | goto err; | |
65 | if (y != NULL) { | |
66 | if (x == y) { | |
67 | if (!BN_sqr(a, x, ctx)) | |
68 | goto err; | |
69 | } else { | |
70 | if (!BN_mul(a, x, y, ctx)) | |
71 | goto err; | |
72 | } | |
73 | ca = a; | |
74 | } else | |
75 | ca = x; /* Just do the mod */ | |
76 | ||
77 | ret = BN_div_recp(NULL, r, ca, recp, ctx); | |
78 | err: | |
79 | BN_CTX_end(ctx); | |
80 | bn_check_top(r); | |
26a7d938 | 81 | return ret; |
0f113f3e | 82 | } |
dfeab068 | 83 | |
020fc820 | 84 | int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, |
0f113f3e MC |
85 | BN_RECP_CTX *recp, BN_CTX *ctx) |
86 | { | |
87 | int i, j, ret = 0; | |
88 | BIGNUM *a, *b, *d, *r; | |
89 | ||
90 | BN_CTX_start(ctx); | |
edea42c6 PY |
91 | d = (dv != NULL) ? dv : BN_CTX_get(ctx); |
92 | r = (rem != NULL) ? rem : BN_CTX_get(ctx); | |
0f113f3e MC |
93 | a = BN_CTX_get(ctx); |
94 | b = BN_CTX_get(ctx); | |
edea42c6 | 95 | if (b == NULL) |
0f113f3e MC |
96 | goto err; |
97 | ||
98 | if (BN_ucmp(m, &(recp->N)) < 0) { | |
99 | BN_zero(d); | |
3f6c7691 AG |
100 | if (!BN_copy(r, m)) { |
101 | BN_CTX_end(ctx); | |
0f113f3e | 102 | return 0; |
3f6c7691 | 103 | } |
0f113f3e | 104 | BN_CTX_end(ctx); |
208fb891 | 105 | return 1; |
0f113f3e MC |
106 | } |
107 | ||
108 | /* | |
109 | * We want the remainder Given input of ABCDEF / ab we need multiply | |
110 | * ABCDEF by 3 digests of the reciprocal of ab | |
111 | */ | |
112 | ||
113 | /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ | |
114 | i = BN_num_bits(m); | |
115 | j = recp->num_bits << 1; | |
116 | if (j > i) | |
117 | i = j; | |
118 | ||
119 | /* Nr := round(2^i / N) */ | |
120 | if (i != recp->shift) | |
121 | recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx); | |
122 | /* BN_reciprocal could have returned -1 for an error */ | |
123 | if (recp->shift == -1) | |
124 | goto err; | |
dfeab068 | 125 | |
e95bbc3c AP |
126 | /*- |
127 | * d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| | |
128 | * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| | |
129 | * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| | |
130 | * = |m/N| | |
131 | */ | |
0f113f3e MC |
132 | if (!BN_rshift(a, m, recp->num_bits)) |
133 | goto err; | |
134 | if (!BN_mul(b, a, &(recp->Nr), ctx)) | |
135 | goto err; | |
136 | if (!BN_rshift(d, b, i - recp->num_bits)) | |
137 | goto err; | |
138 | d->neg = 0; | |
139 | ||
140 | if (!BN_mul(b, &(recp->N), d, ctx)) | |
141 | goto err; | |
142 | if (!BN_usub(r, m, b)) | |
143 | goto err; | |
144 | r->neg = 0; | |
dfeab068 | 145 | |
0f113f3e MC |
146 | j = 0; |
147 | while (BN_ucmp(r, &(recp->N)) >= 0) { | |
148 | if (j++ > 2) { | |
149 | BNerr(BN_F_BN_DIV_RECP, BN_R_BAD_RECIPROCAL); | |
150 | goto err; | |
151 | } | |
152 | if (!BN_usub(r, r, &(recp->N))) | |
153 | goto err; | |
154 | if (!BN_add_word(d, 1)) | |
155 | goto err; | |
156 | } | |
d02b48c6 | 157 | |
0f113f3e MC |
158 | r->neg = BN_is_zero(r) ? 0 : m->neg; |
159 | d->neg = m->neg ^ recp->N.neg; | |
160 | ret = 1; | |
161 | err: | |
162 | BN_CTX_end(ctx); | |
163 | bn_check_top(dv); | |
164 | bn_check_top(rem); | |
26a7d938 | 165 | return ret; |
0f113f3e MC |
166 | } |
167 | ||
168 | /* | |
169 | * len is the expected size of the result We actually calculate with an extra | |
170 | * word of precision, so we can do faster division if the remainder is not | |
171 | * required. | |
dfeab068 | 172 | */ |
78a0c1f1 | 173 | /* r := 2^len / m */ |
6343829a | 174 | int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) |
0f113f3e MC |
175 | { |
176 | int ret = -1; | |
177 | BIGNUM *t; | |
178 | ||
179 | BN_CTX_start(ctx); | |
180 | if ((t = BN_CTX_get(ctx)) == NULL) | |
181 | goto err; | |
182 | ||
183 | if (!BN_set_bit(t, len)) | |
184 | goto err; | |
185 | ||
186 | if (!BN_div(r, NULL, t, m, ctx)) | |
187 | goto err; | |
188 | ||
189 | ret = len; | |
190 | err: | |
191 | bn_check_top(r); | |
192 | BN_CTX_end(ctx); | |
26a7d938 | 193 | return ret; |
0f113f3e | 194 | } |