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 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
38 return NULL;
39 }
40
41 ret->lock = CRYPTO_THREAD_lock_new();
42 if (ret->lock == NULL) {
43 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
44 OPENSSL_free(ret);
45 return NULL;
46 }
47
48 BN_BLINDING_set_current_thread(ret);
49
50 if (A != NULL) {
51 if ((ret->A = BN_dup(A)) == NULL)
52 goto err;
53 }
54
55 if (Ai != NULL) {
56 if ((ret->Ai = BN_dup(Ai)) == NULL)
57 goto err;
58 }
59
60 /* save a copy of mod in the BN_BLINDING structure */
61 if ((ret->mod = BN_dup(mod)) == NULL)
62 goto err;
63
64 if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
65 BN_set_flags(ret->mod, BN_FLG_CONSTTIME);
66
67 /*
68 * Set the counter to the special value -1 to indicate that this is
69 * never-used fresh blinding that does not need updating before first
70 * use.
71 */
72 ret->counter = -1;
73
74 return ret;
75
76 err:
77 BN_BLINDING_free(ret);
78 return NULL;
79 }
80
BN_BLINDING_free(BN_BLINDING * r)81 void BN_BLINDING_free(BN_BLINDING *r)
82 {
83 if (r == NULL)
84 return;
85 BN_free(r->A);
86 BN_free(r->Ai);
87 BN_free(r->e);
88 BN_free(r->mod);
89 CRYPTO_THREAD_lock_free(r->lock);
90 OPENSSL_free(r);
91 }
92
BN_BLINDING_update(BN_BLINDING * b,BN_CTX * ctx)93 int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
94 {
95 int ret = 0;
96
97 if ((b->A == NULL) || (b->Ai == NULL)) {
98 ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
99 goto err;
100 }
101
102 if (b->counter == -1)
103 b->counter = 0;
104
105 if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL &&
106 !(b->flags & BN_BLINDING_NO_RECREATE)) {
107 /* re-create blinding parameters */
108 if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
109 goto err;
110 } else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
111 if (b->m_ctx != NULL) {
112 if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
113 || !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
114 goto err;
115 } else {
116 if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
117 || !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
118 goto err;
119 }
120 }
121
122 ret = 1;
123 err:
124 if (b->counter == BN_BLINDING_COUNTER)
125 b->counter = 0;
126 return ret;
127 }
128
BN_BLINDING_convert(BIGNUM * n,BN_BLINDING * b,BN_CTX * ctx)129 int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
130 {
131 return BN_BLINDING_convert_ex(n, NULL, b, ctx);
132 }
133
BN_BLINDING_convert_ex(BIGNUM * n,BIGNUM * r,BN_BLINDING * b,BN_CTX * ctx)134 int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
135 {
136 int ret = 1;
137
138 bn_check_top(n);
139
140 if ((b->A == NULL) || (b->Ai == NULL)) {
141 ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
142 return 0;
143 }
144
145 if (b->counter == -1)
146 /* Fresh blinding, doesn't need updating. */
147 b->counter = 0;
148 else if (!BN_BLINDING_update(b, ctx))
149 return 0;
150
151 if (r != NULL && (BN_copy(r, b->Ai) == NULL))
152 return 0;
153
154 if (b->m_ctx != NULL)
155 ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
156 else
157 ret = BN_mod_mul(n, n, b->A, b->mod, ctx);
158
159 return ret;
160 }
161
BN_BLINDING_invert(BIGNUM * n,BN_BLINDING * b,BN_CTX * ctx)162 int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
163 {
164 return BN_BLINDING_invert_ex(n, NULL, b, ctx);
165 }
166
BN_BLINDING_invert_ex(BIGNUM * n,const BIGNUM * r,BN_BLINDING * b,BN_CTX * ctx)167 int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
168 BN_CTX *ctx)
169 {
170 int ret;
171
172 bn_check_top(n);
173
174 if (r == NULL && (r = b->Ai) == NULL) {
175 ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
176 return 0;
177 }
178
179 if (b->m_ctx != NULL) {
180 /* ensure that BN_mod_mul_montgomery takes pre-defined path */
181 if (n->dmax >= r->top) {
182 size_t i, rtop = r->top, ntop = n->top;
183 BN_ULONG mask;
184
185 for (i = 0; i < rtop; i++) {
186 mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
187 n->d[i] &= mask;
188 }
189 mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
190 /* always true, if (rtop >= ntop) n->top = r->top; */
191 n->top = (int)(rtop & ~mask) | (ntop & mask);
192 n->flags |= (BN_FLG_FIXED_TOP & ~mask);
193 }
194 ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx);
195 bn_correct_top_consttime(n);
196 } else {
197 ret = BN_mod_mul(n, n, r, b->mod, ctx);
198 }
199
200 bn_check_top(n);
201 return ret;
202 }
203
BN_BLINDING_is_current_thread(BN_BLINDING * b)204 int BN_BLINDING_is_current_thread(BN_BLINDING *b)
205 {
206 return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
207 }
208
BN_BLINDING_set_current_thread(BN_BLINDING * b)209 void BN_BLINDING_set_current_thread(BN_BLINDING *b)
210 {
211 b->tid = CRYPTO_THREAD_get_current_id();
212 }
213
BN_BLINDING_lock(BN_BLINDING * b)214 int BN_BLINDING_lock(BN_BLINDING *b)
215 {
216 return CRYPTO_THREAD_write_lock(b->lock);
217 }
218
BN_BLINDING_unlock(BN_BLINDING * b)219 int BN_BLINDING_unlock(BN_BLINDING *b)
220 {
221 return CRYPTO_THREAD_unlock(b->lock);
222 }
223
BN_BLINDING_get_flags(const BN_BLINDING * b)224 unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
225 {
226 return b->flags;
227 }
228
BN_BLINDING_set_flags(BN_BLINDING * b,unsigned long flags)229 void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
230 {
231 b->flags = flags;
232 }
233
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)234 BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
235 const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
236 int (*bn_mod_exp) (BIGNUM *r,
237 const BIGNUM *a,
238 const BIGNUM *p,
239 const BIGNUM *m,
240 BN_CTX *ctx,
241 BN_MONT_CTX *m_ctx),
242 BN_MONT_CTX *m_ctx)
243 {
244 int retry_counter = 32;
245 BN_BLINDING *ret = NULL;
246
247 if (b == NULL)
248 ret = BN_BLINDING_new(NULL, NULL, m);
249 else
250 ret = b;
251
252 if (ret == NULL)
253 goto err;
254
255 if (ret->A == NULL && (ret->A = BN_new()) == NULL)
256 goto err;
257 if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
258 goto err;
259
260 if (e != NULL) {
261 BN_free(ret->e);
262 ret->e = BN_dup(e);
263 }
264 if (ret->e == NULL)
265 goto err;
266
267 if (bn_mod_exp != NULL)
268 ret->bn_mod_exp = bn_mod_exp;
269 if (m_ctx != NULL)
270 ret->m_ctx = m_ctx;
271
272 do {
273 int rv;
274 if (!BN_priv_rand_range_ex(ret->A, ret->mod, 0, ctx))
275 goto err;
276 if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
277 break;
278
279 /*
280 * this should almost never happen for good RSA keys
281 */
282 if (!rv)
283 goto err;
284
285 if (retry_counter-- == 0) {
286 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
287 goto err;
288 }
289 } while (1);
290
291 if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
292 if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
293 goto err;
294 } else {
295 if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
296 goto err;
297 }
298
299 if (ret->m_ctx != NULL) {
300 if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
301 || !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
302 goto err;
303 }
304
305 return ret;
306 err:
307 if (b == NULL) {
308 BN_BLINDING_free(ret);
309 ret = NULL;
310 }
311
312 return ret;
313 }
314