dsa_ossl.c revision 337982
1/* crypto/dsa/dsa_ossl.c */ 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */ 60 61#include <stdio.h> 62#include "cryptlib.h" 63#include <openssl/bn.h> 64#include <openssl/sha.h> 65#include <openssl/dsa.h> 66#include <openssl/rand.h> 67#include <openssl/asn1.h> 68 69static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 70static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, 71 BIGNUM **rp); 72static int dsa_do_verify(const unsigned char *dgst, int dgst_len, 73 DSA_SIG *sig, DSA *dsa); 74static int dsa_init(DSA *dsa); 75static int dsa_finish(DSA *dsa); 76 77static DSA_METHOD openssl_dsa_meth = { 78 "OpenSSL DSA method", 79 dsa_do_sign, 80 dsa_sign_setup, 81 dsa_do_verify, 82 NULL, /* dsa_mod_exp, */ 83 NULL, /* dsa_bn_mod_exp, */ 84 dsa_init, 85 dsa_finish, 86 0, 87 NULL, 88 NULL, 89 NULL 90}; 91 92/*- 93 * These macro wrappers replace attempts to use the dsa_mod_exp() and 94 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 95 * having a the macro work as an expression by bundling an "err_instr". So; 96 * 97 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 98 * dsa->method_mont_p)) goto err; 99 * 100 * can be replaced by; 101 * 102 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 103 * dsa->method_mont_p); 104 */ 105 106#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 107 do { \ 108 int _tmp_res53; \ 109 if ((dsa)->meth->dsa_mod_exp) \ 110 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \ 111 (a2), (p2), (m), (ctx), (in_mont)); \ 112 else \ 113 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \ 114 (m), (ctx), (in_mont)); \ 115 if (!_tmp_res53) err_instr; \ 116 } while(0) 117#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 118 do { \ 119 int _tmp_res53; \ 120 if ((dsa)->meth->bn_mod_exp) \ 121 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \ 122 (m), (ctx), (m_ctx)); \ 123 else \ 124 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \ 125 if (!_tmp_res53) err_instr; \ 126 } while(0) 127 128const DSA_METHOD *DSA_OpenSSL(void) 129{ 130 return &openssl_dsa_meth; 131} 132 133static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 134{ 135 BIGNUM *kinv = NULL, *r = NULL, *s = NULL; 136 BIGNUM *m, *blind, *blindm, *tmp; 137 BN_CTX *ctx = NULL; 138 int reason = ERR_R_BN_LIB; 139 DSA_SIG *ret = NULL; 140 int noredo = 0; 141 142 if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) { 143 reason = DSA_R_MISSING_PARAMETERS; 144 goto err; 145 } 146 147 s = BN_new(); 148 if (s == NULL) 149 goto err; 150 ctx = BN_CTX_new(); 151 if (ctx == NULL) 152 goto err; 153 m = BN_CTX_get(ctx); 154 blind = BN_CTX_get(ctx); 155 blindm = BN_CTX_get(ctx); 156 tmp = BN_CTX_get(ctx); 157 if (tmp == NULL) 158 goto err; 159 160 redo: 161 if ((dsa->kinv == NULL) || (dsa->r == NULL)) { 162 if (!DSA_sign_setup(dsa, ctx, &kinv, &r)) 163 goto err; 164 } else { 165 kinv = dsa->kinv; 166 dsa->kinv = NULL; 167 r = dsa->r; 168 dsa->r = NULL; 169 noredo = 1; 170 } 171 172 if (dlen > BN_num_bytes(dsa->q)) 173 /* 174 * if the digest length is greater than the size of q use the 175 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3, 176 * 4.2 177 */ 178 dlen = BN_num_bytes(dsa->q); 179 if (BN_bin2bn(dgst, dlen, m) == NULL) 180 goto err; 181 182 /* 183 * The normal signature calculation is: 184 * 185 * s := k^-1 * (m + r * priv_key) mod q 186 * 187 * We will blind this to protect against side channel attacks 188 * 189 * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q 190 */ 191 192 /* Generate a blinding value */ 193 do { 194 if (!BN_rand(blind, BN_num_bits(dsa->q) - 1, -1, 0)) 195 goto err; 196 } while (BN_is_zero(blind)); 197 BN_set_flags(blind, BN_FLG_CONSTTIME); 198 BN_set_flags(blindm, BN_FLG_CONSTTIME); 199 BN_set_flags(tmp, BN_FLG_CONSTTIME); 200 201 /* tmp := blind * priv_key * r mod q */ 202 if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->q, ctx)) 203 goto err; 204 if (!BN_mod_mul(tmp, tmp, r, dsa->q, ctx)) 205 goto err; 206 207 /* blindm := blind * m mod q */ 208 if (!BN_mod_mul(blindm, blind, m, dsa->q, ctx)) 209 goto err; 210 211 /* s : = (blind * priv_key * r) + (blind * m) mod q */ 212 if (!BN_mod_add_quick(s, tmp, blindm, dsa->q)) 213 goto err; 214 215 /* s := s * k^-1 mod q */ 216 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) 217 goto err; 218 219 /* s:= s * blind^-1 mod q */ 220 if (BN_mod_inverse(blind, blind, dsa->q, ctx) == NULL) 221 goto err; 222 if (!BN_mod_mul(s, s, blind, dsa->q, ctx)) 223 goto err; 224 225 /* 226 * Redo if r or s is zero as required by FIPS 186-3: this is very 227 * unlikely. 228 */ 229 if (BN_is_zero(r) || BN_is_zero(s)) { 230 if (noredo) { 231 reason = DSA_R_NEED_NEW_SETUP_VALUES; 232 goto err; 233 } 234 goto redo; 235 } 236 ret = DSA_SIG_new(); 237 if (ret == NULL) 238 goto err; 239 ret->r = r; 240 ret->s = s; 241 242 err: 243 if (ret == NULL) { 244 DSAerr(DSA_F_DSA_DO_SIGN, reason); 245 BN_free(r); 246 BN_free(s); 247 } 248 BN_CTX_free(ctx); 249 BN_clear_free(kinv); 250 return ret; 251} 252 253static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, 254 BIGNUM **rp) 255{ 256 BN_CTX *ctx; 257 BIGNUM k, kq, *K, *kinv = NULL, *r = NULL; 258 BIGNUM l, m; 259 int ret = 0; 260 int q_bits; 261 262 if (!dsa->p || !dsa->q || !dsa->g) { 263 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS); 264 return 0; 265 } 266 267 BN_init(&k); 268 BN_init(&kq); 269 BN_init(&l); 270 BN_init(&m); 271 272 if (ctx_in == NULL) { 273 if ((ctx = BN_CTX_new()) == NULL) 274 goto err; 275 } else 276 ctx = ctx_in; 277 278 if ((r = BN_new()) == NULL) 279 goto err; 280 281 /* Preallocate space */ 282 q_bits = BN_num_bits(dsa->q); 283 if (!BN_set_bit(&k, q_bits) 284 || !BN_set_bit(&l, q_bits) 285 || !BN_set_bit(&m, q_bits)) 286 goto err; 287 288 /* Get random k */ 289 do 290 if (!BN_rand_range(&k, dsa->q)) 291 goto err; 292 while (BN_is_zero(&k)); 293 294 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { 295 BN_set_flags(&k, BN_FLG_CONSTTIME); 296 } 297 298 299 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { 300 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 301 CRYPTO_LOCK_DSA, dsa->p, ctx)) 302 goto err; 303 } 304 305 /* Compute r = (g^k mod p) mod q */ 306 307 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { 308 /* 309 * We do not want timing information to leak the length of k, so we 310 * compute G^k using an equivalent scalar of fixed bit-length. 311 * 312 * We unconditionally perform both of these additions to prevent a 313 * small timing information leakage. We then choose the sum that is 314 * one bit longer than the modulus. 315 * 316 * TODO: revisit the BN_copy aiming for a memory access agnostic 317 * conditional copy. 318 */ 319 if (!BN_add(&l, &k, dsa->q) 320 || !BN_add(&m, &l, dsa->q) 321 || !BN_copy(&kq, BN_num_bits(&l) > q_bits ? &l : &m)) 322 goto err; 323 324 BN_set_flags(&kq, BN_FLG_CONSTTIME); 325 326 K = &kq; 327 } else { 328 K = &k; 329 } 330 331 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 332 dsa->method_mont_p); 333 if (!BN_mod(r, r, dsa->q, ctx)) 334 goto err; 335 336 /* Compute part of 's = inv(k) (m + xr) mod q' */ 337 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL) 338 goto err; 339 340 if (*kinvp != NULL) 341 BN_clear_free(*kinvp); 342 *kinvp = kinv; 343 kinv = NULL; 344 if (*rp != NULL) 345 BN_clear_free(*rp); 346 *rp = r; 347 ret = 1; 348 err: 349 if (!ret) { 350 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB); 351 if (r != NULL) 352 BN_clear_free(r); 353 } 354 if (ctx_in == NULL) 355 BN_CTX_free(ctx); 356 BN_clear_free(&k); 357 BN_clear_free(&kq); 358 BN_clear_free(&l); 359 BN_clear_free(&m); 360 return ret; 361} 362 363static int dsa_do_verify(const unsigned char *dgst, int dgst_len, 364 DSA_SIG *sig, DSA *dsa) 365{ 366 BN_CTX *ctx; 367 BIGNUM u1, u2, t1; 368 BN_MONT_CTX *mont = NULL; 369 int ret = -1, i; 370 if (!dsa->p || !dsa->q || !dsa->g) { 371 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS); 372 return -1; 373 } 374 375 i = BN_num_bits(dsa->q); 376 /* fips 186-3 allows only different sizes for q */ 377 if (i != 160 && i != 224 && i != 256) { 378 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE); 379 return -1; 380 } 381 382 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) { 383 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE); 384 return -1; 385 } 386 BN_init(&u1); 387 BN_init(&u2); 388 BN_init(&t1); 389 390 if ((ctx = BN_CTX_new()) == NULL) 391 goto err; 392 393 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 394 BN_ucmp(sig->r, dsa->q) >= 0) { 395 ret = 0; 396 goto err; 397 } 398 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 399 BN_ucmp(sig->s, dsa->q) >= 0) { 400 ret = 0; 401 goto err; 402 } 403 404 /* 405 * Calculate W = inv(S) mod Q save W in u2 406 */ 407 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL) 408 goto err; 409 410 /* save M in u1 */ 411 if (dgst_len > (i >> 3)) 412 /* 413 * if the digest length is greater than the size of q use the 414 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3, 415 * 4.2 416 */ 417 dgst_len = (i >> 3); 418 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL) 419 goto err; 420 421 /* u1 = M * w mod q */ 422 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx)) 423 goto err; 424 425 /* u2 = r * w mod q */ 426 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx)) 427 goto err; 428 429 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { 430 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 431 CRYPTO_LOCK_DSA, dsa->p, ctx); 432 if (!mont) 433 goto err; 434 } 435 436 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, 437 ctx, mont); 438 /* BN_copy(&u1,&t1); */ 439 /* let u1 = u1 mod q */ 440 if (!BN_mod(&u1, &t1, dsa->q, ctx)) 441 goto err; 442 443 /* 444 * V is now in u1. If the signature is correct, it will be equal to R. 445 */ 446 ret = (BN_ucmp(&u1, sig->r) == 0); 447 448 err: 449 if (ret < 0) 450 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB); 451 if (ctx != NULL) 452 BN_CTX_free(ctx); 453 BN_free(&u1); 454 BN_free(&u2); 455 BN_free(&t1); 456 return (ret); 457} 458 459static int dsa_init(DSA *dsa) 460{ 461 dsa->flags |= DSA_FLAG_CACHE_MONT_P; 462 return (1); 463} 464 465static int dsa_finish(DSA *dsa) 466{ 467 if (dsa->method_mont_p) 468 BN_MONT_CTX_free(dsa->method_mont_p); 469 return (1); 470} 471