1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young (eay@cryptsoft.com)"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.]
56 *
57 * The DSS routines are based on patches supplied by
58 * Steven Schoch <schoch@sheba.arc.nasa.gov>. */
59
60 #include <openssl/dsa.h>
61
62 #include <string.h>
63
64 #include <openssl/bn.h>
65 #include <openssl/dh.h>
66 #include <openssl/digest.h>
67 #include <openssl/engine.h>
68 #include <openssl/err.h>
69 #include <openssl/ex_data.h>
70 #include <openssl/mem.h>
71 #include <openssl/rand.h>
72 #include <openssl/sha.h>
73 #include <openssl/thread.h>
74
75 #include "internal.h"
76 #include "../fipsmodule/bn/internal.h"
77 #include "../internal.h"
78
79
80 // Primality test according to FIPS PUB 186[-1], Appendix 2.1: 50 rounds of
81 // Miller-Rabin.
82 #define DSS_prime_checks 50
83
84 static int dsa_sign_setup(const DSA *dsa, BN_CTX *ctx_in, BIGNUM **out_kinv,
85 BIGNUM **out_r);
86
87 static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT;
88
DSA_new(void)89 DSA *DSA_new(void) {
90 DSA *dsa = OPENSSL_malloc(sizeof(DSA));
91 if (dsa == NULL) {
92 OPENSSL_PUT_ERROR(DSA, ERR_R_MALLOC_FAILURE);
93 return NULL;
94 }
95
96 OPENSSL_memset(dsa, 0, sizeof(DSA));
97
98 dsa->references = 1;
99
100 CRYPTO_MUTEX_init(&dsa->method_mont_lock);
101 CRYPTO_new_ex_data(&dsa->ex_data);
102
103 return dsa;
104 }
105
DSA_free(DSA * dsa)106 void DSA_free(DSA *dsa) {
107 if (dsa == NULL) {
108 return;
109 }
110
111 if (!CRYPTO_refcount_dec_and_test_zero(&dsa->references)) {
112 return;
113 }
114
115 CRYPTO_free_ex_data(&g_ex_data_class, dsa, &dsa->ex_data);
116
117 BN_clear_free(dsa->p);
118 BN_clear_free(dsa->q);
119 BN_clear_free(dsa->g);
120 BN_clear_free(dsa->pub_key);
121 BN_clear_free(dsa->priv_key);
122 BN_MONT_CTX_free(dsa->method_mont_p);
123 BN_MONT_CTX_free(dsa->method_mont_q);
124 CRYPTO_MUTEX_cleanup(&dsa->method_mont_lock);
125 OPENSSL_free(dsa);
126 }
127
DSA_up_ref(DSA * dsa)128 int DSA_up_ref(DSA *dsa) {
129 CRYPTO_refcount_inc(&dsa->references);
130 return 1;
131 }
132
DSA_get0_pub_key(const DSA * dsa)133 const BIGNUM *DSA_get0_pub_key(const DSA *dsa) { return dsa->pub_key; }
134
DSA_get0_priv_key(const DSA * dsa)135 const BIGNUM *DSA_get0_priv_key(const DSA *dsa) { return dsa->priv_key; }
136
DSA_get0_p(const DSA * dsa)137 const BIGNUM *DSA_get0_p(const DSA *dsa) { return dsa->p; }
138
DSA_get0_q(const DSA * dsa)139 const BIGNUM *DSA_get0_q(const DSA *dsa) { return dsa->q; }
140
DSA_get0_g(const DSA * dsa)141 const BIGNUM *DSA_get0_g(const DSA *dsa) { return dsa->g; }
142
DSA_get0_key(const DSA * dsa,const BIGNUM ** out_pub_key,const BIGNUM ** out_priv_key)143 void DSA_get0_key(const DSA *dsa, const BIGNUM **out_pub_key,
144 const BIGNUM **out_priv_key) {
145 if (out_pub_key != NULL) {
146 *out_pub_key = dsa->pub_key;
147 }
148 if (out_priv_key != NULL) {
149 *out_priv_key = dsa->priv_key;
150 }
151 }
152
DSA_get0_pqg(const DSA * dsa,const BIGNUM ** out_p,const BIGNUM ** out_q,const BIGNUM ** out_g)153 void DSA_get0_pqg(const DSA *dsa, const BIGNUM **out_p, const BIGNUM **out_q,
154 const BIGNUM **out_g) {
155 if (out_p != NULL) {
156 *out_p = dsa->p;
157 }
158 if (out_q != NULL) {
159 *out_q = dsa->q;
160 }
161 if (out_g != NULL) {
162 *out_g = dsa->g;
163 }
164 }
165
DSA_set0_key(DSA * dsa,BIGNUM * pub_key,BIGNUM * priv_key)166 int DSA_set0_key(DSA *dsa, BIGNUM *pub_key, BIGNUM *priv_key) {
167 if (dsa->pub_key == NULL && pub_key == NULL) {
168 return 0;
169 }
170
171 if (pub_key != NULL) {
172 BN_free(dsa->pub_key);
173 dsa->pub_key = pub_key;
174 }
175 if (priv_key != NULL) {
176 BN_free(dsa->priv_key);
177 dsa->priv_key = priv_key;
178 }
179
180 return 1;
181 }
182
DSA_set0_pqg(DSA * dsa,BIGNUM * p,BIGNUM * q,BIGNUM * g)183 int DSA_set0_pqg(DSA *dsa, BIGNUM *p, BIGNUM *q, BIGNUM *g) {
184 if ((dsa->p == NULL && p == NULL) ||
185 (dsa->q == NULL && q == NULL) ||
186 (dsa->g == NULL && g == NULL)) {
187 return 0;
188 }
189
190 if (p != NULL) {
191 BN_free(dsa->p);
192 dsa->p = p;
193 }
194 if (q != NULL) {
195 BN_free(dsa->q);
196 dsa->q = q;
197 }
198 if (g != NULL) {
199 BN_free(dsa->g);
200 dsa->g = g;
201 }
202
203 return 1;
204 }
205
DSA_generate_parameters_ex(DSA * dsa,unsigned bits,const uint8_t * seed_in,size_t seed_len,int * out_counter,unsigned long * out_h,BN_GENCB * cb)206 int DSA_generate_parameters_ex(DSA *dsa, unsigned bits, const uint8_t *seed_in,
207 size_t seed_len, int *out_counter,
208 unsigned long *out_h, BN_GENCB *cb) {
209 int ok = 0;
210 unsigned char seed[SHA256_DIGEST_LENGTH];
211 unsigned char md[SHA256_DIGEST_LENGTH];
212 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH];
213 BIGNUM *r0, *W, *X, *c, *test;
214 BIGNUM *g = NULL, *q = NULL, *p = NULL;
215 BN_MONT_CTX *mont = NULL;
216 int k, n = 0, m = 0;
217 unsigned i;
218 int counter = 0;
219 int r = 0;
220 BN_CTX *ctx = NULL;
221 unsigned int h = 2;
222 unsigned qsize;
223 const EVP_MD *evpmd;
224
225 evpmd = (bits >= 2048) ? EVP_sha256() : EVP_sha1();
226 qsize = EVP_MD_size(evpmd);
227
228 if (bits < 512) {
229 bits = 512;
230 }
231
232 bits = (bits + 63) / 64 * 64;
233
234 if (seed_in != NULL) {
235 if (seed_len < (size_t)qsize) {
236 return 0;
237 }
238 if (seed_len > (size_t)qsize) {
239 // Only consume as much seed as is expected.
240 seed_len = qsize;
241 }
242 OPENSSL_memcpy(seed, seed_in, seed_len);
243 }
244
245 ctx = BN_CTX_new();
246 if (ctx == NULL) {
247 goto err;
248 }
249 BN_CTX_start(ctx);
250
251 r0 = BN_CTX_get(ctx);
252 g = BN_CTX_get(ctx);
253 W = BN_CTX_get(ctx);
254 q = BN_CTX_get(ctx);
255 X = BN_CTX_get(ctx);
256 c = BN_CTX_get(ctx);
257 p = BN_CTX_get(ctx);
258 test = BN_CTX_get(ctx);
259
260 if (test == NULL || !BN_lshift(test, BN_value_one(), bits - 1)) {
261 goto err;
262 }
263
264 for (;;) {
265 // Find q.
266 for (;;) {
267 // step 1
268 if (!BN_GENCB_call(cb, BN_GENCB_GENERATED, m++)) {
269 goto err;
270 }
271
272 int use_random_seed = (seed_in == NULL);
273 if (use_random_seed) {
274 if (!RAND_bytes(seed, qsize)) {
275 goto err;
276 }
277 } else {
278 // If we come back through, use random seed next time.
279 seed_in = NULL;
280 }
281 OPENSSL_memcpy(buf, seed, qsize);
282 OPENSSL_memcpy(buf2, seed, qsize);
283 // precompute "SEED + 1" for step 7:
284 for (i = qsize - 1; i < qsize; i--) {
285 buf[i]++;
286 if (buf[i] != 0) {
287 break;
288 }
289 }
290
291 // step 2
292 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL) ||
293 !EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) {
294 goto err;
295 }
296 for (i = 0; i < qsize; i++) {
297 md[i] ^= buf2[i];
298 }
299
300 // step 3
301 md[0] |= 0x80;
302 md[qsize - 1] |= 0x01;
303 if (!BN_bin2bn(md, qsize, q)) {
304 goto err;
305 }
306
307 // step 4
308 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, use_random_seed, cb);
309 if (r > 0) {
310 break;
311 }
312 if (r != 0) {
313 goto err;
314 }
315
316 // do a callback call
317 // step 5
318 }
319
320 if (!BN_GENCB_call(cb, 2, 0) || !BN_GENCB_call(cb, 3, 0)) {
321 goto err;
322 }
323
324 // step 6
325 counter = 0;
326 // "offset = 2"
327
328 n = (bits - 1) / 160;
329
330 for (;;) {
331 if ((counter != 0) && !BN_GENCB_call(cb, BN_GENCB_GENERATED, counter)) {
332 goto err;
333 }
334
335 // step 7
336 BN_zero(W);
337 // now 'buf' contains "SEED + offset - 1"
338 for (k = 0; k <= n; k++) {
339 // obtain "SEED + offset + k" by incrementing:
340 for (i = qsize - 1; i < qsize; i--) {
341 buf[i]++;
342 if (buf[i] != 0) {
343 break;
344 }
345 }
346
347 if (!EVP_Digest(buf, qsize, md, NULL, evpmd, NULL)) {
348 goto err;
349 }
350
351 // step 8
352 if (!BN_bin2bn(md, qsize, r0) ||
353 !BN_lshift(r0, r0, (qsize << 3) * k) ||
354 !BN_add(W, W, r0)) {
355 goto err;
356 }
357 }
358
359 // more of step 8
360 if (!BN_mask_bits(W, bits - 1) ||
361 !BN_copy(X, W) ||
362 !BN_add(X, X, test)) {
363 goto err;
364 }
365
366 // step 9
367 if (!BN_lshift1(r0, q) ||
368 !BN_mod(c, X, r0, ctx) ||
369 !BN_sub(r0, c, BN_value_one()) ||
370 !BN_sub(p, X, r0)) {
371 goto err;
372 }
373
374 // step 10
375 if (BN_cmp(p, test) >= 0) {
376 // step 11
377 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, ctx, 1, cb);
378 if (r > 0) {
379 goto end; // found it
380 }
381 if (r != 0) {
382 goto err;
383 }
384 }
385
386 // step 13
387 counter++;
388 // "offset = offset + n + 1"
389
390 // step 14
391 if (counter >= 4096) {
392 break;
393 }
394 }
395 }
396 end:
397 if (!BN_GENCB_call(cb, 2, 1)) {
398 goto err;
399 }
400
401 // We now need to generate g
402 // Set r0=(p-1)/q
403 if (!BN_sub(test, p, BN_value_one()) ||
404 !BN_div(r0, NULL, test, q, ctx)) {
405 goto err;
406 }
407
408 mont = BN_MONT_CTX_new_for_modulus(p, ctx);
409 if (mont == NULL ||
410 !BN_set_word(test, h)) {
411 goto err;
412 }
413
414 for (;;) {
415 // g=test^r0%p
416 if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont)) {
417 goto err;
418 }
419 if (!BN_is_one(g)) {
420 break;
421 }
422 if (!BN_add(test, test, BN_value_one())) {
423 goto err;
424 }
425 h++;
426 }
427
428 if (!BN_GENCB_call(cb, 3, 1)) {
429 goto err;
430 }
431
432 ok = 1;
433
434 err:
435 if (ok) {
436 BN_free(dsa->p);
437 BN_free(dsa->q);
438 BN_free(dsa->g);
439 dsa->p = BN_dup(p);
440 dsa->q = BN_dup(q);
441 dsa->g = BN_dup(g);
442 if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) {
443 ok = 0;
444 goto err;
445 }
446 if (out_counter != NULL) {
447 *out_counter = counter;
448 }
449 if (out_h != NULL) {
450 *out_h = h;
451 }
452 }
453
454 if (ctx) {
455 BN_CTX_end(ctx);
456 BN_CTX_free(ctx);
457 }
458
459 BN_MONT_CTX_free(mont);
460
461 return ok;
462 }
463
DSAparams_dup(const DSA * dsa)464 DSA *DSAparams_dup(const DSA *dsa) {
465 DSA *ret = DSA_new();
466 if (ret == NULL) {
467 return NULL;
468 }
469 ret->p = BN_dup(dsa->p);
470 ret->q = BN_dup(dsa->q);
471 ret->g = BN_dup(dsa->g);
472 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
473 DSA_free(ret);
474 return NULL;
475 }
476 return ret;
477 }
478
DSA_generate_key(DSA * dsa)479 int DSA_generate_key(DSA *dsa) {
480 int ok = 0;
481 BN_CTX *ctx = NULL;
482 BIGNUM *pub_key = NULL, *priv_key = NULL;
483
484 ctx = BN_CTX_new();
485 if (ctx == NULL) {
486 goto err;
487 }
488
489 priv_key = dsa->priv_key;
490 if (priv_key == NULL) {
491 priv_key = BN_new();
492 if (priv_key == NULL) {
493 goto err;
494 }
495 }
496
497 if (!BN_rand_range_ex(priv_key, 1, dsa->q)) {
498 goto err;
499 }
500
501 pub_key = dsa->pub_key;
502 if (pub_key == NULL) {
503 pub_key = BN_new();
504 if (pub_key == NULL) {
505 goto err;
506 }
507 }
508
509 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, &dsa->method_mont_lock,
510 dsa->p, ctx) ||
511 !BN_mod_exp_mont_consttime(pub_key, dsa->g, priv_key, dsa->p, ctx,
512 dsa->method_mont_p)) {
513 goto err;
514 }
515
516 dsa->priv_key = priv_key;
517 dsa->pub_key = pub_key;
518 ok = 1;
519
520 err:
521 if (dsa->pub_key == NULL) {
522 BN_free(pub_key);
523 }
524 if (dsa->priv_key == NULL) {
525 BN_free(priv_key);
526 }
527 BN_CTX_free(ctx);
528
529 return ok;
530 }
531
DSA_SIG_new(void)532 DSA_SIG *DSA_SIG_new(void) {
533 DSA_SIG *sig;
534 sig = OPENSSL_malloc(sizeof(DSA_SIG));
535 if (!sig) {
536 return NULL;
537 }
538 sig->r = NULL;
539 sig->s = NULL;
540 return sig;
541 }
542
DSA_SIG_free(DSA_SIG * sig)543 void DSA_SIG_free(DSA_SIG *sig) {
544 if (!sig) {
545 return;
546 }
547
548 BN_free(sig->r);
549 BN_free(sig->s);
550 OPENSSL_free(sig);
551 }
552
553 // mod_mul_consttime sets |r| to |a| * |b| modulo |mont->N|, treating |a| and
554 // |b| as secret. This function internally uses Montgomery reduction, but
555 // neither inputs nor outputs are in Montgomery form.
mod_mul_consttime(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BN_MONT_CTX * mont,BN_CTX * ctx)556 static int mod_mul_consttime(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
557 const BN_MONT_CTX *mont, BN_CTX *ctx) {
558 BN_CTX_start(ctx);
559 BIGNUM *tmp = BN_CTX_get(ctx);
560 // |BN_mod_mul_montgomery| removes a factor of R, so we cancel it with a
561 // single |BN_to_montgomery| which adds one factor of R.
562 int ok = tmp != NULL &&
563 BN_to_montgomery(tmp, a, mont, ctx) &&
564 BN_mod_mul_montgomery(r, tmp, b, mont, ctx);
565 BN_CTX_end(ctx);
566 return ok;
567 }
568
DSA_do_sign(const uint8_t * digest,size_t digest_len,const DSA * dsa)569 DSA_SIG *DSA_do_sign(const uint8_t *digest, size_t digest_len, const DSA *dsa) {
570 if (!dsa_check_parameters(dsa)) {
571 return NULL;
572 }
573
574 BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
575 BIGNUM m;
576 BIGNUM xr;
577 BN_CTX *ctx = NULL;
578 DSA_SIG *ret = NULL;
579
580 BN_init(&m);
581 BN_init(&xr);
582 s = BN_new();
583 if (s == NULL) {
584 goto err;
585 }
586 ctx = BN_CTX_new();
587 if (ctx == NULL) {
588 goto err;
589 }
590
591 redo:
592 if (!dsa_sign_setup(dsa, ctx, &kinv, &r)) {
593 goto err;
594 }
595
596 if (digest_len > BN_num_bytes(dsa->q)) {
597 // If the digest length is greater than the size of |dsa->q| use the
598 // BN_num_bits(dsa->q) leftmost bits of the digest, see FIPS 186-3, 4.2.
599 // Note the above check that |dsa->q| is a multiple of 8 bits.
600 digest_len = BN_num_bytes(dsa->q);
601 }
602
603 if (BN_bin2bn(digest, digest_len, &m) == NULL) {
604 goto err;
605 }
606
607 // |m| is bounded by 2^(num_bits(q)), which is slightly looser than q. This
608 // violates |bn_mod_add_consttime| and |mod_mul_consttime|'s preconditions.
609 // (The underlying algorithms could accept looser bounds, but we reduce for
610 // simplicity.)
611 size_t q_width = bn_minimal_width(dsa->q);
612 if (!bn_resize_words(&m, q_width) ||
613 !bn_resize_words(&xr, q_width)) {
614 goto err;
615 }
616 bn_reduce_once_in_place(m.d, 0 /* no carry word */, dsa->q->d,
617 xr.d /* scratch space */, q_width);
618
619 // Compute s = inv(k) (m + xr) mod q. Note |dsa->method_mont_q| is
620 // initialized by |dsa_sign_setup|.
621 if (!mod_mul_consttime(&xr, dsa->priv_key, r, dsa->method_mont_q, ctx) ||
622 !bn_mod_add_consttime(s, &xr, &m, dsa->q, ctx) ||
623 !mod_mul_consttime(s, s, kinv, dsa->method_mont_q, ctx)) {
624 goto err;
625 }
626
627 // Redo if r or s is zero as required by FIPS 186-3: this is
628 // very unlikely.
629 if (BN_is_zero(r) || BN_is_zero(s)) {
630 goto redo;
631 }
632 ret = DSA_SIG_new();
633 if (ret == NULL) {
634 goto err;
635 }
636 ret->r = r;
637 ret->s = s;
638
639 err:
640 if (ret == NULL) {
641 OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
642 BN_free(r);
643 BN_free(s);
644 }
645 BN_CTX_free(ctx);
646 BN_clear_free(&m);
647 BN_clear_free(&xr);
648 BN_clear_free(kinv);
649
650 return ret;
651 }
652
DSA_do_verify(const uint8_t * digest,size_t digest_len,DSA_SIG * sig,const DSA * dsa)653 int DSA_do_verify(const uint8_t *digest, size_t digest_len, DSA_SIG *sig,
654 const DSA *dsa) {
655 int valid;
656 if (!DSA_do_check_signature(&valid, digest, digest_len, sig, dsa)) {
657 return -1;
658 }
659 return valid;
660 }
661
DSA_do_check_signature(int * out_valid,const uint8_t * digest,size_t digest_len,DSA_SIG * sig,const DSA * dsa)662 int DSA_do_check_signature(int *out_valid, const uint8_t *digest,
663 size_t digest_len, DSA_SIG *sig, const DSA *dsa) {
664 *out_valid = 0;
665 if (!dsa_check_parameters(dsa)) {
666 return 0;
667 }
668
669 int ret = 0;
670 BIGNUM u1, u2, t1;
671 BN_init(&u1);
672 BN_init(&u2);
673 BN_init(&t1);
674 BN_CTX *ctx = BN_CTX_new();
675 if (ctx == NULL) {
676 goto err;
677 }
678
679 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
680 BN_ucmp(sig->r, dsa->q) >= 0) {
681 ret = 1;
682 goto err;
683 }
684 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
685 BN_ucmp(sig->s, dsa->q) >= 0) {
686 ret = 1;
687 goto err;
688 }
689
690 // Calculate W = inv(S) mod Q
691 // save W in u2
692 if (BN_mod_inverse(&u2, sig->s, dsa->q, ctx) == NULL) {
693 goto err;
694 }
695
696 // save M in u1
697 unsigned q_bits = BN_num_bits(dsa->q);
698 if (digest_len > (q_bits >> 3)) {
699 // if the digest length is greater than the size of q use the
700 // BN_num_bits(dsa->q) leftmost bits of the digest, see
701 // fips 186-3, 4.2
702 digest_len = (q_bits >> 3);
703 }
704
705 if (BN_bin2bn(digest, digest_len, &u1) == NULL) {
706 goto err;
707 }
708
709 // u1 = M * w mod q
710 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx)) {
711 goto err;
712 }
713
714 // u2 = r * w mod q
715 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx)) {
716 goto err;
717 }
718
719 if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
720 (CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->p,
721 ctx)) {
722 goto err;
723 }
724
725 if (!BN_mod_exp2_mont(&t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx,
726 dsa->method_mont_p)) {
727 goto err;
728 }
729
730 // BN_copy(&u1,&t1);
731 // let u1 = u1 mod q
732 if (!BN_mod(&u1, &t1, dsa->q, ctx)) {
733 goto err;
734 }
735
736 // V is now in u1. If the signature is correct, it will be
737 // equal to R.
738 *out_valid = BN_ucmp(&u1, sig->r) == 0;
739 ret = 1;
740
741 err:
742 if (ret != 1) {
743 OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
744 }
745 BN_CTX_free(ctx);
746 BN_free(&u1);
747 BN_free(&u2);
748 BN_free(&t1);
749
750 return ret;
751 }
752
DSA_sign(int type,const uint8_t * digest,size_t digest_len,uint8_t * out_sig,unsigned int * out_siglen,const DSA * dsa)753 int DSA_sign(int type, const uint8_t *digest, size_t digest_len,
754 uint8_t *out_sig, unsigned int *out_siglen, const DSA *dsa) {
755 DSA_SIG *s;
756
757 s = DSA_do_sign(digest, digest_len, dsa);
758 if (s == NULL) {
759 *out_siglen = 0;
760 return 0;
761 }
762
763 *out_siglen = i2d_DSA_SIG(s, &out_sig);
764 DSA_SIG_free(s);
765 return 1;
766 }
767
DSA_verify(int type,const uint8_t * digest,size_t digest_len,const uint8_t * sig,size_t sig_len,const DSA * dsa)768 int DSA_verify(int type, const uint8_t *digest, size_t digest_len,
769 const uint8_t *sig, size_t sig_len, const DSA *dsa) {
770 int valid;
771 if (!DSA_check_signature(&valid, digest, digest_len, sig, sig_len, dsa)) {
772 return -1;
773 }
774 return valid;
775 }
776
DSA_check_signature(int * out_valid,const uint8_t * digest,size_t digest_len,const uint8_t * sig,size_t sig_len,const DSA * dsa)777 int DSA_check_signature(int *out_valid, const uint8_t *digest,
778 size_t digest_len, const uint8_t *sig, size_t sig_len,
779 const DSA *dsa) {
780 DSA_SIG *s = NULL;
781 int ret = 0;
782 uint8_t *der = NULL;
783
784 s = DSA_SIG_new();
785 if (s == NULL) {
786 goto err;
787 }
788
789 const uint8_t *sigp = sig;
790 if (d2i_DSA_SIG(&s, &sigp, sig_len) == NULL || sigp != sig + sig_len) {
791 goto err;
792 }
793
794 // Ensure that the signature uses DER and doesn't have trailing garbage.
795 int der_len = i2d_DSA_SIG(s, &der);
796 if (der_len < 0 || (size_t)der_len != sig_len ||
797 OPENSSL_memcmp(sig, der, sig_len)) {
798 goto err;
799 }
800
801 ret = DSA_do_check_signature(out_valid, digest, digest_len, s, dsa);
802
803 err:
804 OPENSSL_free(der);
805 DSA_SIG_free(s);
806 return ret;
807 }
808
809 // der_len_len returns the number of bytes needed to represent a length of |len|
810 // in DER.
der_len_len(size_t len)811 static size_t der_len_len(size_t len) {
812 if (len < 0x80) {
813 return 1;
814 }
815 size_t ret = 1;
816 while (len > 0) {
817 ret++;
818 len >>= 8;
819 }
820 return ret;
821 }
822
DSA_size(const DSA * dsa)823 int DSA_size(const DSA *dsa) {
824 size_t order_len = BN_num_bytes(dsa->q);
825 // Compute the maximum length of an |order_len| byte integer. Defensively
826 // assume that the leading 0x00 is included.
827 size_t integer_len = 1 /* tag */ + der_len_len(order_len + 1) + 1 + order_len;
828 if (integer_len < order_len) {
829 return 0;
830 }
831 // A DSA signature is two INTEGERs.
832 size_t value_len = 2 * integer_len;
833 if (value_len < integer_len) {
834 return 0;
835 }
836 // Add the header.
837 size_t ret = 1 /* tag */ + der_len_len(value_len) + value_len;
838 if (ret < value_len) {
839 return 0;
840 }
841 return ret;
842 }
843
dsa_sign_setup(const DSA * dsa,BN_CTX * ctx,BIGNUM ** out_kinv,BIGNUM ** out_r)844 static int dsa_sign_setup(const DSA *dsa, BN_CTX *ctx, BIGNUM **out_kinv,
845 BIGNUM **out_r) {
846 if (!dsa->p || !dsa->q || !dsa->g) {
847 OPENSSL_PUT_ERROR(DSA, DSA_R_MISSING_PARAMETERS);
848 return 0;
849 }
850
851 int ret = 0;
852 BIGNUM k;
853 BN_init(&k);
854 BIGNUM *r = BN_new();
855 BIGNUM *kinv = BN_new();
856 if (r == NULL || kinv == NULL ||
857 // Get random k
858 !BN_rand_range_ex(&k, 1, dsa->q) ||
859 !BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
860 (CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->p,
861 ctx) ||
862 !BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_q,
863 (CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->q,
864 ctx) ||
865 // Compute r = (g^k mod p) mod q
866 !BN_mod_exp_mont_consttime(r, dsa->g, &k, dsa->p, ctx,
867 dsa->method_mont_p) ||
868 // Note |BN_mod| below is not constant-time and may leak information about
869 // |r|. |dsa->p| may be significantly larger than |dsa->q|, so this is not
870 // easily performed in constant-time with Montgomery reduction.
871 //
872 // However, |r| at this point is g^k (mod p). It is almost the value of
873 // |r| revealed in the signature anyway (g^k (mod p) (mod q)), going from
874 // it to |k| would require computing a discrete log.
875 !BN_mod(r, r, dsa->q, ctx) ||
876 // Compute part of 's = inv(k) (m + xr) mod q' using Fermat's Little
877 // Theorem.
878 !bn_mod_inverse_prime(kinv, &k, dsa->q, ctx, dsa->method_mont_q)) {
879 OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
880 goto err;
881 }
882
883 BN_clear_free(*out_kinv);
884 *out_kinv = kinv;
885 kinv = NULL;
886
887 BN_clear_free(*out_r);
888 *out_r = r;
889 r = NULL;
890
891 ret = 1;
892
893 err:
894 BN_clear_free(&k);
895 BN_clear_free(r);
896 BN_clear_free(kinv);
897 return ret;
898 }
899
DSA_get_ex_new_index(long argl,void * argp,CRYPTO_EX_unused * unused,CRYPTO_EX_dup * dup_unused,CRYPTO_EX_free * free_func)900 int DSA_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused,
901 CRYPTO_EX_dup *dup_unused, CRYPTO_EX_free *free_func) {
902 int index;
903 if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp,
904 free_func)) {
905 return -1;
906 }
907 return index;
908 }
909
DSA_set_ex_data(DSA * dsa,int idx,void * arg)910 int DSA_set_ex_data(DSA *dsa, int idx, void *arg) {
911 return CRYPTO_set_ex_data(&dsa->ex_data, idx, arg);
912 }
913
DSA_get_ex_data(const DSA * dsa,int idx)914 void *DSA_get_ex_data(const DSA *dsa, int idx) {
915 return CRYPTO_get_ex_data(&dsa->ex_data, idx);
916 }
917
DSA_dup_DH(const DSA * dsa)918 DH *DSA_dup_DH(const DSA *dsa) {
919 if (dsa == NULL) {
920 return NULL;
921 }
922
923 DH *ret = DH_new();
924 if (ret == NULL) {
925 goto err;
926 }
927 if (dsa->q != NULL) {
928 ret->priv_length = BN_num_bits(dsa->q);
929 if ((ret->q = BN_dup(dsa->q)) == NULL) {
930 goto err;
931 }
932 }
933 if ((dsa->p != NULL && (ret->p = BN_dup(dsa->p)) == NULL) ||
934 (dsa->g != NULL && (ret->g = BN_dup(dsa->g)) == NULL) ||
935 (dsa->pub_key != NULL && (ret->pub_key = BN_dup(dsa->pub_key)) == NULL) ||
936 (dsa->priv_key != NULL &&
937 (ret->priv_key = BN_dup(dsa->priv_key)) == NULL)) {
938 goto err;
939 }
940
941 return ret;
942
943 err:
944 DH_free(ret);
945 return NULL;
946 }
947