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 "../fipsmodule/bn/internal.h"
76 #include "../internal.h"
77
78
79 #define OPENSSL_DSA_MAX_MODULUS_BITS 10000
80
81 // Primality test according to FIPS PUB 186[-1], Appendix 2.1: 50 rounds of
82 // Rabin-Miller
83 #define DSS_prime_checks 50
84
85 static int dsa_sign_setup(const DSA *dsa, BN_CTX *ctx_in, BIGNUM **out_kinv,
86 BIGNUM **out_r);
87
88 static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT;
89
DSA_new(void)90 DSA *DSA_new(void) {
91 DSA *dsa = OPENSSL_malloc(sizeof(DSA));
92 if (dsa == NULL) {
93 OPENSSL_PUT_ERROR(DSA, ERR_R_MALLOC_FAILURE);
94 return NULL;
95 }
96
97 OPENSSL_memset(dsa, 0, sizeof(DSA));
98
99 dsa->references = 1;
100
101 CRYPTO_MUTEX_init(&dsa->method_mont_lock);
102 CRYPTO_new_ex_data(&dsa->ex_data);
103
104 return dsa;
105 }
106
DSA_free(DSA * dsa)107 void DSA_free(DSA *dsa) {
108 if (dsa == NULL) {
109 return;
110 }
111
112 if (!CRYPTO_refcount_dec_and_test_zero(&dsa->references)) {
113 return;
114 }
115
116 CRYPTO_free_ex_data(&g_ex_data_class, dsa, &dsa->ex_data);
117
118 BN_clear_free(dsa->p);
119 BN_clear_free(dsa->q);
120 BN_clear_free(dsa->g);
121 BN_clear_free(dsa->pub_key);
122 BN_clear_free(dsa->priv_key);
123 BN_MONT_CTX_free(dsa->method_mont_p);
124 BN_MONT_CTX_free(dsa->method_mont_q);
125 CRYPTO_MUTEX_cleanup(&dsa->method_mont_lock);
126 OPENSSL_free(dsa);
127 }
128
DSA_up_ref(DSA * dsa)129 int DSA_up_ref(DSA *dsa) {
130 CRYPTO_refcount_inc(&dsa->references);
131 return 1;
132 }
133
DSA_get0_key(const DSA * dsa,const BIGNUM ** out_pub_key,const BIGNUM ** out_priv_key)134 void DSA_get0_key(const DSA *dsa, const BIGNUM **out_pub_key,
135 const BIGNUM **out_priv_key) {
136 if (out_pub_key != NULL) {
137 *out_pub_key = dsa->pub_key;
138 }
139 if (out_priv_key != NULL) {
140 *out_priv_key = dsa->priv_key;
141 }
142 }
143
DSA_get0_pqg(const DSA * dsa,const BIGNUM ** out_p,const BIGNUM ** out_q,const BIGNUM ** out_g)144 void DSA_get0_pqg(const DSA *dsa, const BIGNUM **out_p, const BIGNUM **out_q,
145 const BIGNUM **out_g) {
146 if (out_p != NULL) {
147 *out_p = dsa->p;
148 }
149 if (out_q != NULL) {
150 *out_q = dsa->q;
151 }
152 if (out_g != NULL) {
153 *out_g = dsa->g;
154 }
155 }
156
DSA_set0_key(DSA * dsa,BIGNUM * pub_key,BIGNUM * priv_key)157 int DSA_set0_key(DSA *dsa, BIGNUM *pub_key, BIGNUM *priv_key) {
158 if (dsa->pub_key == NULL && pub_key == NULL) {
159 return 0;
160 }
161
162 if (pub_key != NULL) {
163 BN_free(dsa->pub_key);
164 dsa->pub_key = pub_key;
165 }
166 if (priv_key != NULL) {
167 BN_free(dsa->priv_key);
168 dsa->priv_key = priv_key;
169 }
170
171 return 1;
172 }
173
DSA_set0_pqg(DSA * dsa,BIGNUM * p,BIGNUM * q,BIGNUM * g)174 int DSA_set0_pqg(DSA *dsa, BIGNUM *p, BIGNUM *q, BIGNUM *g) {
175 if ((dsa->p == NULL && p == NULL) ||
176 (dsa->q == NULL && q == NULL) ||
177 (dsa->g == NULL && g == NULL)) {
178 return 0;
179 }
180
181 if (p != NULL) {
182 BN_free(dsa->p);
183 dsa->p = p;
184 }
185 if (q != NULL) {
186 BN_free(dsa->q);
187 dsa->q = q;
188 }
189 if (g != NULL) {
190 BN_free(dsa->g);
191 dsa->g = g;
192 }
193
194 return 1;
195 }
196
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)197 int DSA_generate_parameters_ex(DSA *dsa, unsigned bits, const uint8_t *seed_in,
198 size_t seed_len, int *out_counter,
199 unsigned long *out_h, BN_GENCB *cb) {
200 int ok = 0;
201 unsigned char seed[SHA256_DIGEST_LENGTH];
202 unsigned char md[SHA256_DIGEST_LENGTH];
203 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH];
204 BIGNUM *r0, *W, *X, *c, *test;
205 BIGNUM *g = NULL, *q = NULL, *p = NULL;
206 BN_MONT_CTX *mont = NULL;
207 int k, n = 0, m = 0;
208 unsigned i;
209 int counter = 0;
210 int r = 0;
211 BN_CTX *ctx = NULL;
212 unsigned int h = 2;
213 unsigned qsize;
214 const EVP_MD *evpmd;
215
216 evpmd = (bits >= 2048) ? EVP_sha256() : EVP_sha1();
217 qsize = EVP_MD_size(evpmd);
218
219 if (bits < 512) {
220 bits = 512;
221 }
222
223 bits = (bits + 63) / 64 * 64;
224
225 if (seed_in != NULL) {
226 if (seed_len < (size_t)qsize) {
227 return 0;
228 }
229 if (seed_len > (size_t)qsize) {
230 // Only consume as much seed as is expected.
231 seed_len = qsize;
232 }
233 OPENSSL_memcpy(seed, seed_in, seed_len);
234 }
235
236 ctx = BN_CTX_new();
237 if (ctx == NULL) {
238 goto err;
239 }
240 BN_CTX_start(ctx);
241
242 r0 = BN_CTX_get(ctx);
243 g = BN_CTX_get(ctx);
244 W = BN_CTX_get(ctx);
245 q = BN_CTX_get(ctx);
246 X = BN_CTX_get(ctx);
247 c = BN_CTX_get(ctx);
248 p = BN_CTX_get(ctx);
249 test = BN_CTX_get(ctx);
250
251 if (test == NULL || !BN_lshift(test, BN_value_one(), bits - 1)) {
252 goto err;
253 }
254
255 for (;;) {
256 // Find q.
257 for (;;) {
258 // step 1
259 if (!BN_GENCB_call(cb, 0, m++)) {
260 goto err;
261 }
262
263 int use_random_seed = (seed_in == NULL);
264 if (use_random_seed) {
265 if (!RAND_bytes(seed, qsize)) {
266 goto err;
267 }
268 } else {
269 // If we come back through, use random seed next time.
270 seed_in = NULL;
271 }
272 OPENSSL_memcpy(buf, seed, qsize);
273 OPENSSL_memcpy(buf2, seed, qsize);
274 // precompute "SEED + 1" for step 7:
275 for (i = qsize - 1; i < qsize; i--) {
276 buf[i]++;
277 if (buf[i] != 0) {
278 break;
279 }
280 }
281
282 // step 2
283 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL) ||
284 !EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) {
285 goto err;
286 }
287 for (i = 0; i < qsize; i++) {
288 md[i] ^= buf2[i];
289 }
290
291 // step 3
292 md[0] |= 0x80;
293 md[qsize - 1] |= 0x01;
294 if (!BN_bin2bn(md, qsize, q)) {
295 goto err;
296 }
297
298 // step 4
299 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, use_random_seed, cb);
300 if (r > 0) {
301 break;
302 }
303 if (r != 0) {
304 goto err;
305 }
306
307 // do a callback call
308 // step 5
309 }
310
311 if (!BN_GENCB_call(cb, 2, 0) || !BN_GENCB_call(cb, 3, 0)) {
312 goto err;
313 }
314
315 // step 6
316 counter = 0;
317 // "offset = 2"
318
319 n = (bits - 1) / 160;
320
321 for (;;) {
322 if ((counter != 0) && !BN_GENCB_call(cb, 0, counter)) {
323 goto err;
324 }
325
326 // step 7
327 BN_zero(W);
328 // now 'buf' contains "SEED + offset - 1"
329 for (k = 0; k <= n; k++) {
330 // obtain "SEED + offset + k" by incrementing:
331 for (i = qsize - 1; i < qsize; i--) {
332 buf[i]++;
333 if (buf[i] != 0) {
334 break;
335 }
336 }
337
338 if (!EVP_Digest(buf, qsize, md, NULL, evpmd, NULL)) {
339 goto err;
340 }
341
342 // step 8
343 if (!BN_bin2bn(md, qsize, r0) ||
344 !BN_lshift(r0, r0, (qsize << 3) * k) ||
345 !BN_add(W, W, r0)) {
346 goto err;
347 }
348 }
349
350 // more of step 8
351 if (!BN_mask_bits(W, bits - 1) ||
352 !BN_copy(X, W) ||
353 !BN_add(X, X, test)) {
354 goto err;
355 }
356
357 // step 9
358 if (!BN_lshift1(r0, q) ||
359 !BN_mod(c, X, r0, ctx) ||
360 !BN_sub(r0, c, BN_value_one()) ||
361 !BN_sub(p, X, r0)) {
362 goto err;
363 }
364
365 // step 10
366 if (BN_cmp(p, test) >= 0) {
367 // step 11
368 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, ctx, 1, cb);
369 if (r > 0) {
370 goto end; // found it
371 }
372 if (r != 0) {
373 goto err;
374 }
375 }
376
377 // step 13
378 counter++;
379 // "offset = offset + n + 1"
380
381 // step 14
382 if (counter >= 4096) {
383 break;
384 }
385 }
386 }
387 end:
388 if (!BN_GENCB_call(cb, 2, 1)) {
389 goto err;
390 }
391
392 // We now need to generate g
393 // Set r0=(p-1)/q
394 if (!BN_sub(test, p, BN_value_one()) ||
395 !BN_div(r0, NULL, test, q, ctx)) {
396 goto err;
397 }
398
399 mont = BN_MONT_CTX_new_for_modulus(p, ctx);
400 if (mont == NULL ||
401 !BN_set_word(test, h)) {
402 goto err;
403 }
404
405 for (;;) {
406 // g=test^r0%p
407 if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont)) {
408 goto err;
409 }
410 if (!BN_is_one(g)) {
411 break;
412 }
413 if (!BN_add(test, test, BN_value_one())) {
414 goto err;
415 }
416 h++;
417 }
418
419 if (!BN_GENCB_call(cb, 3, 1)) {
420 goto err;
421 }
422
423 ok = 1;
424
425 err:
426 if (ok) {
427 BN_free(dsa->p);
428 BN_free(dsa->q);
429 BN_free(dsa->g);
430 dsa->p = BN_dup(p);
431 dsa->q = BN_dup(q);
432 dsa->g = BN_dup(g);
433 if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) {
434 ok = 0;
435 goto err;
436 }
437 if (out_counter != NULL) {
438 *out_counter = counter;
439 }
440 if (out_h != NULL) {
441 *out_h = h;
442 }
443 }
444
445 if (ctx) {
446 BN_CTX_end(ctx);
447 BN_CTX_free(ctx);
448 }
449
450 BN_MONT_CTX_free(mont);
451
452 return ok;
453 }
454
DSAparams_dup(const DSA * dsa)455 DSA *DSAparams_dup(const DSA *dsa) {
456 DSA *ret = DSA_new();
457 if (ret == NULL) {
458 return NULL;
459 }
460 ret->p = BN_dup(dsa->p);
461 ret->q = BN_dup(dsa->q);
462 ret->g = BN_dup(dsa->g);
463 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
464 DSA_free(ret);
465 return NULL;
466 }
467 return ret;
468 }
469
DSA_generate_key(DSA * dsa)470 int DSA_generate_key(DSA *dsa) {
471 int ok = 0;
472 BN_CTX *ctx = NULL;
473 BIGNUM *pub_key = NULL, *priv_key = NULL;
474
475 ctx = BN_CTX_new();
476 if (ctx == NULL) {
477 goto err;
478 }
479
480 priv_key = dsa->priv_key;
481 if (priv_key == NULL) {
482 priv_key = BN_new();
483 if (priv_key == NULL) {
484 goto err;
485 }
486 }
487
488 if (!BN_rand_range_ex(priv_key, 1, dsa->q)) {
489 goto err;
490 }
491
492 pub_key = dsa->pub_key;
493 if (pub_key == NULL) {
494 pub_key = BN_new();
495 if (pub_key == NULL) {
496 goto err;
497 }
498 }
499
500 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, &dsa->method_mont_lock,
501 dsa->p, ctx) ||
502 !BN_mod_exp_mont_consttime(pub_key, dsa->g, priv_key, dsa->p, ctx,
503 dsa->method_mont_p)) {
504 goto err;
505 }
506
507 dsa->priv_key = priv_key;
508 dsa->pub_key = pub_key;
509 ok = 1;
510
511 err:
512 if (dsa->pub_key == NULL) {
513 BN_free(pub_key);
514 }
515 if (dsa->priv_key == NULL) {
516 BN_free(priv_key);
517 }
518 BN_CTX_free(ctx);
519
520 return ok;
521 }
522
DSA_SIG_new(void)523 DSA_SIG *DSA_SIG_new(void) {
524 DSA_SIG *sig;
525 sig = OPENSSL_malloc(sizeof(DSA_SIG));
526 if (!sig) {
527 return NULL;
528 }
529 sig->r = NULL;
530 sig->s = NULL;
531 return sig;
532 }
533
DSA_SIG_free(DSA_SIG * sig)534 void DSA_SIG_free(DSA_SIG *sig) {
535 if (!sig) {
536 return;
537 }
538
539 BN_free(sig->r);
540 BN_free(sig->s);
541 OPENSSL_free(sig);
542 }
543
DSA_do_sign(const uint8_t * digest,size_t digest_len,const DSA * dsa)544 DSA_SIG *DSA_do_sign(const uint8_t *digest, size_t digest_len, const DSA *dsa) {
545 BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
546 BIGNUM m;
547 BIGNUM xr;
548 BN_CTX *ctx = NULL;
549 int reason = ERR_R_BN_LIB;
550 DSA_SIG *ret = NULL;
551
552 BN_init(&m);
553 BN_init(&xr);
554
555 if (!dsa->p || !dsa->q || !dsa->g) {
556 reason = DSA_R_MISSING_PARAMETERS;
557 goto err;
558 }
559
560 s = BN_new();
561 if (s == NULL) {
562 goto err;
563 }
564 ctx = BN_CTX_new();
565 if (ctx == NULL) {
566 goto err;
567 }
568
569 redo:
570 if (!dsa_sign_setup(dsa, ctx, &kinv, &r)) {
571 goto err;
572 }
573
574 if (digest_len > BN_num_bytes(dsa->q)) {
575 // if the digest length is greater than the size of q use the
576 // BN_num_bits(dsa->q) leftmost bits of the digest, see
577 // fips 186-3, 4.2
578 digest_len = BN_num_bytes(dsa->q);
579 }
580
581 if (BN_bin2bn(digest, digest_len, &m) == NULL) {
582 goto err;
583 }
584
585 // Compute s = inv(k) (m + xr) mod q
586 if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx)) {
587 goto err; // s = xr
588 }
589 if (!BN_add(s, &xr, &m)) {
590 goto err; // s = m + xr
591 }
592 if (BN_cmp(s, dsa->q) > 0) {
593 if (!BN_sub(s, s, dsa->q)) {
594 goto err;
595 }
596 }
597 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) {
598 goto err;
599 }
600
601 // Redo if r or s is zero as required by FIPS 186-3: this is
602 // very unlikely.
603 if (BN_is_zero(r) || BN_is_zero(s)) {
604 goto redo;
605 }
606 ret = DSA_SIG_new();
607 if (ret == NULL) {
608 goto err;
609 }
610 ret->r = r;
611 ret->s = s;
612
613 err:
614 if (ret == NULL) {
615 OPENSSL_PUT_ERROR(DSA, reason);
616 BN_free(r);
617 BN_free(s);
618 }
619 BN_CTX_free(ctx);
620 BN_clear_free(&m);
621 BN_clear_free(&xr);
622 BN_clear_free(kinv);
623
624 return ret;
625 }
626
DSA_do_verify(const uint8_t * digest,size_t digest_len,DSA_SIG * sig,const DSA * dsa)627 int DSA_do_verify(const uint8_t *digest, size_t digest_len, DSA_SIG *sig,
628 const DSA *dsa) {
629 int valid;
630 if (!DSA_do_check_signature(&valid, digest, digest_len, sig, dsa)) {
631 return -1;
632 }
633 return valid;
634 }
635
DSA_do_check_signature(int * out_valid,const uint8_t * digest,size_t digest_len,DSA_SIG * sig,const DSA * dsa)636 int DSA_do_check_signature(int *out_valid, const uint8_t *digest,
637 size_t digest_len, DSA_SIG *sig, const DSA *dsa) {
638 BN_CTX *ctx;
639 BIGNUM u1, u2, t1;
640 int ret = 0;
641 unsigned i;
642
643 *out_valid = 0;
644
645 if (!dsa->p || !dsa->q || !dsa->g) {
646 OPENSSL_PUT_ERROR(DSA, DSA_R_MISSING_PARAMETERS);
647 return 0;
648 }
649
650 i = BN_num_bits(dsa->q);
651 // fips 186-3 allows only different sizes for q
652 if (i != 160 && i != 224 && i != 256) {
653 OPENSSL_PUT_ERROR(DSA, DSA_R_BAD_Q_VALUE);
654 return 0;
655 }
656
657 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
658 OPENSSL_PUT_ERROR(DSA, DSA_R_MODULUS_TOO_LARGE);
659 return 0;
660 }
661
662 BN_init(&u1);
663 BN_init(&u2);
664 BN_init(&t1);
665
666 ctx = BN_CTX_new();
667 if (ctx == NULL) {
668 goto err;
669 }
670
671 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
672 BN_ucmp(sig->r, dsa->q) >= 0) {
673 ret = 1;
674 goto err;
675 }
676 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
677 BN_ucmp(sig->s, dsa->q) >= 0) {
678 ret = 1;
679 goto err;
680 }
681
682 // Calculate W = inv(S) mod Q
683 // save W in u2
684 if (BN_mod_inverse(&u2, sig->s, dsa->q, ctx) == NULL) {
685 goto err;
686 }
687
688 // save M in u1
689 if (digest_len > (i >> 3)) {
690 // if the digest length is greater than the size of q use the
691 // BN_num_bits(dsa->q) leftmost bits of the digest, see
692 // fips 186-3, 4.2
693 digest_len = (i >> 3);
694 }
695
696 if (BN_bin2bn(digest, digest_len, &u1) == NULL) {
697 goto err;
698 }
699
700 // u1 = M * w mod q
701 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx)) {
702 goto err;
703 }
704
705 // u2 = r * w mod q
706 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx)) {
707 goto err;
708 }
709
710 if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
711 (CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->p,
712 ctx)) {
713 goto err;
714 }
715
716 if (!BN_mod_exp2_mont(&t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx,
717 dsa->method_mont_p)) {
718 goto err;
719 }
720
721 // BN_copy(&u1,&t1);
722 // let u1 = u1 mod q
723 if (!BN_mod(&u1, &t1, dsa->q, ctx)) {
724 goto err;
725 }
726
727 // V is now in u1. If the signature is correct, it will be
728 // equal to R.
729 *out_valid = BN_ucmp(&u1, sig->r) == 0;
730 ret = 1;
731
732 err:
733 if (ret != 1) {
734 OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
735 }
736 BN_CTX_free(ctx);
737 BN_free(&u1);
738 BN_free(&u2);
739 BN_free(&t1);
740
741 return ret;
742 }
743
DSA_sign(int type,const uint8_t * digest,size_t digest_len,uint8_t * out_sig,unsigned int * out_siglen,const DSA * dsa)744 int DSA_sign(int type, const uint8_t *digest, size_t digest_len,
745 uint8_t *out_sig, unsigned int *out_siglen, const DSA *dsa) {
746 DSA_SIG *s;
747
748 s = DSA_do_sign(digest, digest_len, dsa);
749 if (s == NULL) {
750 *out_siglen = 0;
751 return 0;
752 }
753
754 *out_siglen = i2d_DSA_SIG(s, &out_sig);
755 DSA_SIG_free(s);
756 return 1;
757 }
758
DSA_verify(int type,const uint8_t * digest,size_t digest_len,const uint8_t * sig,size_t sig_len,const DSA * dsa)759 int DSA_verify(int type, const uint8_t *digest, size_t digest_len,
760 const uint8_t *sig, size_t sig_len, const DSA *dsa) {
761 int valid;
762 if (!DSA_check_signature(&valid, digest, digest_len, sig, sig_len, dsa)) {
763 return -1;
764 }
765 return valid;
766 }
767
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)768 int DSA_check_signature(int *out_valid, const uint8_t *digest,
769 size_t digest_len, const uint8_t *sig, size_t sig_len,
770 const DSA *dsa) {
771 DSA_SIG *s = NULL;
772 int ret = 0;
773 uint8_t *der = NULL;
774
775 s = DSA_SIG_new();
776 if (s == NULL) {
777 goto err;
778 }
779
780 const uint8_t *sigp = sig;
781 if (d2i_DSA_SIG(&s, &sigp, sig_len) == NULL || sigp != sig + sig_len) {
782 goto err;
783 }
784
785 // Ensure that the signature uses DER and doesn't have trailing garbage.
786 int der_len = i2d_DSA_SIG(s, &der);
787 if (der_len < 0 || (size_t)der_len != sig_len ||
788 OPENSSL_memcmp(sig, der, sig_len)) {
789 goto err;
790 }
791
792 ret = DSA_do_check_signature(out_valid, digest, digest_len, s, dsa);
793
794 err:
795 OPENSSL_free(der);
796 DSA_SIG_free(s);
797 return ret;
798 }
799
800 // der_len_len returns the number of bytes needed to represent a length of |len|
801 // in DER.
der_len_len(size_t len)802 static size_t der_len_len(size_t len) {
803 if (len < 0x80) {
804 return 1;
805 }
806 size_t ret = 1;
807 while (len > 0) {
808 ret++;
809 len >>= 8;
810 }
811 return ret;
812 }
813
DSA_size(const DSA * dsa)814 int DSA_size(const DSA *dsa) {
815 size_t order_len = BN_num_bytes(dsa->q);
816 // Compute the maximum length of an |order_len| byte integer. Defensively
817 // assume that the leading 0x00 is included.
818 size_t integer_len = 1 /* tag */ + der_len_len(order_len + 1) + 1 + order_len;
819 if (integer_len < order_len) {
820 return 0;
821 }
822 // A DSA signature is two INTEGERs.
823 size_t value_len = 2 * integer_len;
824 if (value_len < integer_len) {
825 return 0;
826 }
827 // Add the header.
828 size_t ret = 1 /* tag */ + der_len_len(value_len) + value_len;
829 if (ret < value_len) {
830 return 0;
831 }
832 return ret;
833 }
834
dsa_sign_setup(const DSA * dsa,BN_CTX * ctx_in,BIGNUM ** out_kinv,BIGNUM ** out_r)835 static int dsa_sign_setup(const DSA *dsa, BN_CTX *ctx_in, BIGNUM **out_kinv,
836 BIGNUM **out_r) {
837 BN_CTX *ctx;
838 BIGNUM k, kq, *kinv = NULL, *r = NULL;
839 int ret = 0;
840
841 if (!dsa->p || !dsa->q || !dsa->g) {
842 OPENSSL_PUT_ERROR(DSA, DSA_R_MISSING_PARAMETERS);
843 return 0;
844 }
845
846 BN_init(&k);
847 BN_init(&kq);
848
849 ctx = ctx_in;
850 if (ctx == NULL) {
851 ctx = BN_CTX_new();
852 if (ctx == NULL) {
853 goto err;
854 }
855 }
856
857 r = BN_new();
858 if (r == NULL) {
859 goto err;
860 }
861
862 // Get random k
863 if (!BN_rand_range_ex(&k, 1, dsa->q)) {
864 goto err;
865 }
866
867 if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
868 (CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->p,
869 ctx) ||
870 !BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_q,
871 (CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->q,
872 ctx)) {
873 goto err;
874 }
875
876 // Compute r = (g^k mod p) mod q
877 if (!BN_copy(&kq, &k)) {
878 goto err;
879 }
880
881 // We do not want timing information to leak the length of k,
882 // so we compute g^k using an equivalent exponent of fixed length.
883 //
884 // (This is a kludge that we need because the BN_mod_exp_mont()
885 // does not let us specify the desired timing behaviour.)
886
887 if (!BN_add(&kq, &kq, dsa->q)) {
888 goto err;
889 }
890 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q) && !BN_add(&kq, &kq, dsa->q)) {
891 goto err;
892 }
893
894 if (!BN_mod_exp_mont_consttime(r, dsa->g, &kq, dsa->p, ctx,
895 dsa->method_mont_p)) {
896 goto err;
897 }
898 if (!BN_mod(r, r, dsa->q, ctx)) {
899 goto err;
900 }
901
902 // Compute part of 's = inv(k) (m + xr) mod q' using Fermat's Little
903 // Theorem.
904 kinv = BN_new();
905 if (kinv == NULL ||
906 !bn_mod_inverse_prime(kinv, &k, dsa->q, ctx, dsa->method_mont_q)) {
907 goto err;
908 }
909
910 BN_clear_free(*out_kinv);
911 *out_kinv = kinv;
912 kinv = NULL;
913 BN_clear_free(*out_r);
914 *out_r = r;
915 ret = 1;
916
917 err:
918 if (!ret) {
919 OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
920 if (r != NULL) {
921 BN_clear_free(r);
922 }
923 }
924
925 if (ctx_in == NULL) {
926 BN_CTX_free(ctx);
927 }
928 BN_clear_free(&k);
929 BN_clear_free(&kq);
930 BN_clear_free(kinv);
931 return ret;
932 }
933
DSA_get_ex_new_index(long argl,void * argp,CRYPTO_EX_unused * unused,CRYPTO_EX_dup * dup_unused,CRYPTO_EX_free * free_func)934 int DSA_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused,
935 CRYPTO_EX_dup *dup_unused, CRYPTO_EX_free *free_func) {
936 int index;
937 if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp,
938 free_func)) {
939 return -1;
940 }
941 return index;
942 }
943
DSA_set_ex_data(DSA * dsa,int idx,void * arg)944 int DSA_set_ex_data(DSA *dsa, int idx, void *arg) {
945 return CRYPTO_set_ex_data(&dsa->ex_data, idx, arg);
946 }
947
DSA_get_ex_data(const DSA * dsa,int idx)948 void *DSA_get_ex_data(const DSA *dsa, int idx) {
949 return CRYPTO_get_ex_data(&dsa->ex_data, idx);
950 }
951
DSA_dup_DH(const DSA * dsa)952 DH *DSA_dup_DH(const DSA *dsa) {
953 if (dsa == NULL) {
954 return NULL;
955 }
956
957 DH *ret = DH_new();
958 if (ret == NULL) {
959 goto err;
960 }
961 if (dsa->q != NULL) {
962 ret->priv_length = BN_num_bits(dsa->q);
963 if ((ret->q = BN_dup(dsa->q)) == NULL) {
964 goto err;
965 }
966 }
967 if ((dsa->p != NULL && (ret->p = BN_dup(dsa->p)) == NULL) ||
968 (dsa->g != NULL && (ret->g = BN_dup(dsa->g)) == NULL) ||
969 (dsa->pub_key != NULL && (ret->pub_key = BN_dup(dsa->pub_key)) == NULL) ||
970 (dsa->priv_key != NULL &&
971 (ret->priv_key = BN_dup(dsa->priv_key)) == NULL)) {
972 goto err;
973 }
974
975 return ret;
976
977 err:
978 DH_free(ret);
979 return NULL;
980 }
981