1 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 2 * All rights reserved. 3 * 4 * This package is an SSL implementation written 5 * by Eric Young (eay (at) 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 (at) 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 (at) 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 (at) 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 (at) 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 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 } 106 107 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 } 128 129 int DSA_up_ref(DSA *dsa) { 130 CRYPTO_refcount_inc(&dsa->references); 131 return 1; 132 } 133 134 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 } 143 144 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 } 156 157 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 } 173 174 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 } 196 197 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 } 454 455 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 } 469 470 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 } 522 523 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 } 533 534 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 } 543 544 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 } 626 627 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 } 635 636 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 } 743 744 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 } 758 759 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 } 767 768 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. 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 } 813 814 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 } 834 835 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 } 933 934 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 } 943 944 int DSA_set_ex_data(DSA *dsa, int idx, void *arg) { 945 return CRYPTO_set_ex_data(&dsa->ex_data, idx, arg); 946 } 947 948 void *DSA_get_ex_data(const DSA *dsa, int idx) { 949 return CRYPTO_get_ex_data(&dsa->ex_data, idx); 950 } 951 952 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
