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 69 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 70 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, 71 BIGNUM **rp); 72 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, 73 DSA_SIG *sig, DSA *dsa); 74 static int dsa_init(DSA *dsa); 75 static int dsa_finish(DSA *dsa); 76 77 static 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) 127 128 const DSA_METHOD *DSA_OpenSSL(void) 129 { 130 return &openssl_dsa_meth; 131 } 132 133 static 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; 137 BIGNUM xr; 138 BN_CTX *ctx = NULL; 139 int reason = ERR_R_BN_LIB; 140 DSA_SIG *ret = NULL; 141 int noredo = 0; 142 143 BN_init(&m); 144 BN_init(&xr); 145 146 if (!dsa->p || !dsa->q || !dsa->g) { 147 reason = DSA_R_MISSING_PARAMETERS; 148 goto err; 149 } 150 151 s = BN_new(); 152 if (s == NULL) 153 goto err; 154 ctx = BN_CTX_new(); 155 if (ctx == NULL) 156 goto err; 157 redo: 158 if ((dsa->kinv == NULL) || (dsa->r == NULL)) { 159 if (!DSA_sign_setup(dsa, ctx, &kinv, &r)) 160 goto err; 161 } else { 162 kinv = dsa->kinv; 163 dsa->kinv = NULL; 164 r = dsa->r; 165 dsa->r = NULL; 166 noredo = 1; 167 } 168 169 if (dlen > BN_num_bytes(dsa->q)) 170 /* 171 * if the digest length is greater than the size of q use the 172 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3, 173 * 4.2 174 */ 175 dlen = BN_num_bytes(dsa->q); 176 if (BN_bin2bn(dgst, dlen, &m) == NULL) 177 goto err; 178 179 /* Compute s = inv(k) (m + xr) mod q */ 180 if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx)) 181 goto err; /* s = xr */ 182 if (!BN_add(s, &xr, &m)) 183 goto err; /* s = m + xr */ 184 if (BN_cmp(s, dsa->q) > 0) 185 if (!BN_sub(s, s, dsa->q)) 186 goto err; 187 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) 188 goto err; 189 190 ret = DSA_SIG_new(); 191 if (ret == NULL) 192 goto err; 193 /* 194 * Redo if r or s is zero as required by FIPS 186-3: this is very 195 * unlikely. 196 */ 197 if (BN_is_zero(r) || BN_is_zero(s)) { 198 if (noredo) { 199 reason = DSA_R_NEED_NEW_SETUP_VALUES; 200 goto err; 201 } 202 goto redo; 203 } 204 ret->r = r; 205 ret->s = s; 206 207 err: 208 if (!ret) { 209 DSAerr(DSA_F_DSA_DO_SIGN, reason); 210 BN_free(r); 211 BN_free(s); 212 } 213 if (ctx != NULL) 214 BN_CTX_free(ctx); 215 BN_clear_free(&m); 216 BN_clear_free(&xr); 217 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 218 BN_clear_free(kinv); 219 return (ret); 220 } 221 222 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, 223 BIGNUM **rp) 224 { 225 BN_CTX *ctx; 226 BIGNUM k, kq, *K, *kinv = NULL, *r = NULL; 227 int ret = 0; 228 229 if (!dsa->p || !dsa->q || !dsa->g) { 230 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS); 231 return 0; 232 } 233 234 BN_init(&k); 235 BN_init(&kq); 236 237 if (ctx_in == NULL) { 238 if ((ctx = BN_CTX_new()) == NULL) 239 goto err; 240 } else 241 ctx = ctx_in; 242 243 if ((r = BN_new()) == NULL) 244 goto err; 245 246 /* Get random k */ 247 do 248 if (!BN_rand_range(&k, dsa->q)) 249 goto err; 250 while (BN_is_zero(&k)) ; 251 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { 252 BN_set_flags(&k, BN_FLG_CONSTTIME); 253 } 254 255 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { 256 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 257 CRYPTO_LOCK_DSA, dsa->p, ctx)) 258 goto err; 259 } 260 261 /* Compute r = (g^k mod p) mod q */ 262 263 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { 264 if (!BN_copy(&kq, &k)) 265 goto err; 266 267 /* 268 * We do not want timing information to leak the length of k, so we 269 * compute g^k using an equivalent exponent of fixed length. (This 270 * is a kludge that we need because the BN_mod_exp_mont() does not 271 * let us specify the desired timing behaviour.) 272 */ 273 274 if (!BN_add(&kq, &kq, dsa->q)) 275 goto err; 276 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) { 277 if (!BN_add(&kq, &kq, dsa->q)) 278 goto err; 279 } 280 281 K = &kq; 282 } else { 283 K = &k; 284 } 285 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 286 dsa->method_mont_p); 287 if (!BN_mod(r, r, dsa->q, ctx)) 288 goto err; 289 290 /* Compute part of 's = inv(k) (m + xr) mod q' */ 291 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL) 292 goto err; 293 294 if (*kinvp != NULL) 295 BN_clear_free(*kinvp); 296 *kinvp = kinv; 297 kinv = NULL; 298 if (*rp != NULL) 299 BN_clear_free(*rp); 300 *rp = r; 301 ret = 1; 302 err: 303 if (!ret) { 304 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB); 305 if (r != NULL) 306 BN_clear_free(r); 307 } 308 if (ctx_in == NULL) 309 BN_CTX_free(ctx); 310 BN_clear_free(&k); 311 BN_clear_free(&kq); 312 return (ret); 313 } 314 315 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, 316 DSA_SIG *sig, DSA *dsa) 317 { 318 BN_CTX *ctx; 319 BIGNUM u1, u2, t1; 320 BN_MONT_CTX *mont = NULL; 321 int ret = -1, i; 322 if (!dsa->p || !dsa->q || !dsa->g) { 323 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS); 324 return -1; 325 } 326 327 i = BN_num_bits(dsa->q); 328 /* fips 186-3 allows only different sizes for q */ 329 if (i != 160 && i != 224 && i != 256) { 330 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE); 331 return -1; 332 } 333 334 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) { 335 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE); 336 return -1; 337 } 338 BN_init(&u1); 339 BN_init(&u2); 340 BN_init(&t1); 341 342 if ((ctx = BN_CTX_new()) == NULL) 343 goto err; 344 345 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 346 BN_ucmp(sig->r, dsa->q) >= 0) { 347 ret = 0; 348 goto err; 349 } 350 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 351 BN_ucmp(sig->s, dsa->q) >= 0) { 352 ret = 0; 353 goto err; 354 } 355 356 /* 357 * Calculate W = inv(S) mod Q save W in u2 358 */ 359 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL) 360 goto err; 361 362 /* save M in u1 */ 363 if (dgst_len > (i >> 3)) 364 /* 365 * if the digest length is greater than the size of q use the 366 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3, 367 * 4.2 368 */ 369 dgst_len = (i >> 3); 370 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL) 371 goto err; 372 373 /* u1 = M * w mod q */ 374 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx)) 375 goto err; 376 377 /* u2 = r * w mod q */ 378 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx)) 379 goto err; 380 381 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { 382 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 383 CRYPTO_LOCK_DSA, dsa->p, ctx); 384 if (!mont) 385 goto err; 386 } 387 388 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, 389 ctx, mont); 390 /* BN_copy(&u1,&t1); */ 391 /* let u1 = u1 mod q */ 392 if (!BN_mod(&u1, &t1, dsa->q, ctx)) 393 goto err; 394 395 /* 396 * V is now in u1. If the signature is correct, it will be equal to R. 397 */ 398 ret = (BN_ucmp(&u1, sig->r) == 0); 399 400 err: 401 /* 402 * XXX: surely this is wrong - if ret is 0, it just didn't verify; there 403 * is no error in BN. Test should be ret == -1 (Ben) 404 */ 405 if (ret != 1) 406 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB); 407 if (ctx != NULL) 408 BN_CTX_free(ctx); 409 BN_free(&u1); 410 BN_free(&u2); 411 BN_free(&t1); 412 return (ret); 413 } 414 415 static int dsa_init(DSA *dsa) 416 { 417 dsa->flags |= DSA_FLAG_CACHE_MONT_P; 418 return (1); 419 } 420 421 static int dsa_finish(DSA *dsa) 422 { 423 if (dsa->method_mont_p) 424 BN_MONT_CTX_free(dsa->method_mont_p); 425 return (1); 426 } 427