1 /*
2 * Copyright 1998-2023 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (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
8 */
9
10 #include <openssl/opensslconf.h>
11 #include "internal/cryptlib.h"
12 #include "bn_local.h"
13
14 #define BN_BLINDING_COUNTER 32
15
16 struct bn_blinding_st {
17 BIGNUM *A;
18 BIGNUM *Ai;
19 BIGNUM *e;
20 BIGNUM *mod; /* just a reference */
21 CRYPTO_THREAD_ID tid;
22 int counter;
23 unsigned long flags;
24 BN_MONT_CTX *m_ctx;
25 int (*bn_mod_exp) (BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
26 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
27 CRYPTO_RWLOCK *lock;
28 };
29
BN_BLINDING_new(const BIGNUM * A,const BIGNUM * Ai,BIGNUM * mod)30 BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai, BIGNUM *mod)
31 {
32 BN_BLINDING *ret = NULL;
33
34 bn_check_top(mod);
35
36 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL)
37 return NULL;
38
39 ret->lock = CRYPTO_THREAD_lock_new();
40 if (ret->lock == NULL) {
41 ERR_raise(ERR_LIB_BN, ERR_R_CRYPTO_LIB);
42 OPENSSL_free(ret);
43 return NULL;
44 }
45
46 BN_BLINDING_set_current_thread(ret);
47
48 if (A != NULL) {
49 if ((ret->A = BN_dup(A)) == NULL)
50 goto err;
51 }
52
53 if (Ai != NULL) {
54 if ((ret->Ai = BN_dup(Ai)) == NULL)
55 goto err;
56 }
57
58 /* save a copy of mod in the BN_BLINDING structure */
59 if ((ret->mod = BN_dup(mod)) == NULL)
60 goto err;
61
62 if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
63 BN_set_flags(ret->mod, BN_FLG_CONSTTIME);
64
65 /*
66 * Set the counter to the special value -1 to indicate that this is
67 * never-used fresh blinding that does not need updating before first
68 * use.
69 */
70 ret->counter = -1;
71
72 return ret;
73
74 err:
75 BN_BLINDING_free(ret);
76 return NULL;
77 }
78
BN_BLINDING_free(BN_BLINDING * r)79 void BN_BLINDING_free(BN_BLINDING *r)
80 {
81 if (r == NULL)
82 return;
83 BN_free(r->A);
84 BN_free(r->Ai);
85 BN_free(r->e);
86 BN_free(r->mod);
87 CRYPTO_THREAD_lock_free(r->lock);
88 OPENSSL_free(r);
89 }
90
BN_BLINDING_update(BN_BLINDING * b,BN_CTX * ctx)91 int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
92 {
93 int ret = 0;
94
95 if ((b->A == NULL) || (b->Ai == NULL)) {
96 ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
97 goto err;
98 }
99
100 if (b->counter == -1)
101 b->counter = 0;
102
103 if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL &&
104 !(b->flags & BN_BLINDING_NO_RECREATE)) {
105 /* re-create blinding parameters */
106 if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
107 goto err;
108 } else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
109 if (b->m_ctx != NULL) {
110 if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
111 || !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
112 goto err;
113 } else {
114 if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
115 || !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
116 goto err;
117 }
118 }
119
120 ret = 1;
121 err:
122 if (b->counter == BN_BLINDING_COUNTER)
123 b->counter = 0;
124 return ret;
125 }
126
BN_BLINDING_convert(BIGNUM * n,BN_BLINDING * b,BN_CTX * ctx)127 int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
128 {
129 return BN_BLINDING_convert_ex(n, NULL, b, ctx);
130 }
131
BN_BLINDING_convert_ex(BIGNUM * n,BIGNUM * r,BN_BLINDING * b,BN_CTX * ctx)132 int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
133 {
134 int ret = 1;
135
136 bn_check_top(n);
137
138 if ((b->A == NULL) || (b->Ai == NULL)) {
139 ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
140 return 0;
141 }
142
143 if (b->counter == -1)
144 /* Fresh blinding, doesn't need updating. */
145 b->counter = 0;
146 else if (!BN_BLINDING_update(b, ctx))
147 return 0;
148
149 if (r != NULL && (BN_copy(r, b->Ai) == NULL))
150 return 0;
151
152 if (b->m_ctx != NULL)
153 ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
154 else
155 ret = BN_mod_mul(n, n, b->A, b->mod, ctx);
156
157 return ret;
158 }
159
BN_BLINDING_invert(BIGNUM * n,BN_BLINDING * b,BN_CTX * ctx)160 int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
161 {
162 return BN_BLINDING_invert_ex(n, NULL, b, ctx);
163 }
164
BN_BLINDING_invert_ex(BIGNUM * n,const BIGNUM * r,BN_BLINDING * b,BN_CTX * ctx)165 int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
166 BN_CTX *ctx)
167 {
168 int ret;
169
170 bn_check_top(n);
171
172 if (r == NULL && (r = b->Ai) == NULL) {
173 ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
174 return 0;
175 }
176
177 if (b->m_ctx != NULL) {
178 /* ensure that BN_mod_mul_montgomery takes pre-defined path */
179 if (n->dmax >= r->top) {
180 size_t i, rtop = r->top, ntop = n->top;
181 BN_ULONG mask;
182
183 for (i = 0; i < rtop; i++) {
184 mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
185 n->d[i] &= mask;
186 }
187 mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
188 /* always true, if (rtop >= ntop) n->top = r->top; */
189 n->top = (int)(rtop & ~mask) | (ntop & mask);
190 n->flags |= (BN_FLG_FIXED_TOP & ~mask);
191 }
192 ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx);
193 bn_correct_top_consttime(n);
194 } else {
195 ret = BN_mod_mul(n, n, r, b->mod, ctx);
196 }
197
198 bn_check_top(n);
199 return ret;
200 }
201
BN_BLINDING_is_current_thread(BN_BLINDING * b)202 int BN_BLINDING_is_current_thread(BN_BLINDING *b)
203 {
204 return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
205 }
206
BN_BLINDING_set_current_thread(BN_BLINDING * b)207 void BN_BLINDING_set_current_thread(BN_BLINDING *b)
208 {
209 b->tid = CRYPTO_THREAD_get_current_id();
210 }
211
BN_BLINDING_lock(BN_BLINDING * b)212 int BN_BLINDING_lock(BN_BLINDING *b)
213 {
214 return CRYPTO_THREAD_write_lock(b->lock);
215 }
216
BN_BLINDING_unlock(BN_BLINDING * b)217 int BN_BLINDING_unlock(BN_BLINDING *b)
218 {
219 return CRYPTO_THREAD_unlock(b->lock);
220 }
221
BN_BLINDING_get_flags(const BN_BLINDING * b)222 unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
223 {
224 return b->flags;
225 }
226
BN_BLINDING_set_flags(BN_BLINDING * b,unsigned long flags)227 void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
228 {
229 b->flags = flags;
230 }
231
BN_BLINDING_create_param(BN_BLINDING * b,const BIGNUM * e,BIGNUM * m,BN_CTX * ctx,int (* bn_mod_exp)(BIGNUM * r,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx,BN_MONT_CTX * m_ctx),BN_MONT_CTX * m_ctx)232 BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
233 const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
234 int (*bn_mod_exp) (BIGNUM *r,
235 const BIGNUM *a,
236 const BIGNUM *p,
237 const BIGNUM *m,
238 BN_CTX *ctx,
239 BN_MONT_CTX *m_ctx),
240 BN_MONT_CTX *m_ctx)
241 {
242 int retry_counter = 32;
243 BN_BLINDING *ret = NULL;
244
245 if (b == NULL)
246 ret = BN_BLINDING_new(NULL, NULL, m);
247 else
248 ret = b;
249
250 if (ret == NULL)
251 goto err;
252
253 if (ret->A == NULL && (ret->A = BN_new()) == NULL)
254 goto err;
255 if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
256 goto err;
257
258 if (e != NULL) {
259 BN_free(ret->e);
260 ret->e = BN_dup(e);
261 }
262 if (ret->e == NULL)
263 goto err;
264
265 if (bn_mod_exp != NULL)
266 ret->bn_mod_exp = bn_mod_exp;
267 if (m_ctx != NULL)
268 ret->m_ctx = m_ctx;
269
270 do {
271 int rv;
272 if (!BN_priv_rand_range_ex(ret->A, ret->mod, 0, ctx))
273 goto err;
274 if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
275 break;
276
277 /*
278 * this should almost never happen for good RSA keys
279 */
280 if (!rv)
281 goto err;
282
283 if (retry_counter-- == 0) {
284 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
285 goto err;
286 }
287 } while (1);
288
289 if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
290 if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
291 goto err;
292 } else {
293 if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
294 goto err;
295 }
296
297 if (ret->m_ctx != NULL) {
298 if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
299 || !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
300 goto err;
301 }
302
303 return ret;
304 err:
305 if (b == NULL) {
306 BN_BLINDING_free(ret);
307 ret = NULL;
308 }
309
310 return ret;
311 }
312
