1 /* $OpenBSD: dsa_ossl.c,v 1.21 2014/07/12 16:03:37 miod Exp $ */ 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 63 #include <openssl/asn1.h> 64 #include <openssl/bn.h> 65 #include <openssl/dsa.h> 66 #include <openssl/err.h> 67 #include <openssl/rand.h> 68 #include <openssl/sha.h> 69 70 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 71 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, 72 BIGNUM **rp); 73 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 74 DSA *dsa); 75 static int dsa_init(DSA *dsa); 76 static int dsa_finish(DSA *dsa); 77 78 static DSA_METHOD openssl_dsa_meth = { 79 .name = "OpenSSL DSA method", 80 .dsa_do_sign = dsa_do_sign, 81 .dsa_sign_setup = dsa_sign_setup, 82 .dsa_do_verify = dsa_do_verify, 83 .init = dsa_init, 84 .finish = dsa_finish 85 }; 86 87 /* 88 * These macro wrappers replace attempts to use the dsa_mod_exp() and 89 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 90 * having a the macro work as an expression by bundling an "err_instr". So; 91 * 92 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 93 * dsa->method_mont_p)) goto err; 94 * 95 * can be replaced by; 96 * 97 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 98 * dsa->method_mont_p); 99 */ 100 101 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 102 do { \ 103 int _tmp_res53; \ 104 if ((dsa)->meth->dsa_mod_exp) \ 105 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), \ 106 (a1), (p1), (a2), (p2), (m), (ctx), (in_mont)); \ 107 else \ 108 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), \ 109 (p1), (a2), (p2), (m), (ctx), (in_mont)); \ 110 if (!_tmp_res53) \ 111 err_instr; \ 112 } while(0) 113 114 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 115 do { \ 116 int _tmp_res53; \ 117 if ((dsa)->meth->bn_mod_exp) \ 118 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), \ 119 (a), (p), (m), (ctx), (m_ctx)); \ 120 else \ 121 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), \ 122 (ctx), (m_ctx)); \ 123 if (!_tmp_res53) \ 124 err_instr; \ 125 } while(0) 126 127 const DSA_METHOD * 128 DSA_OpenSSL(void) 129 { 130 return &openssl_dsa_meth; 131 } 132 133 static DSA_SIG * 134 dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 135 { 136 BIGNUM *kinv = NULL, *r = NULL, *s = NULL; 137 BIGNUM m; 138 BIGNUM xr; 139 BN_CTX *ctx = NULL; 140 int reason = ERR_R_BN_LIB; 141 DSA_SIG *ret = NULL; 142 int noredo = 0; 143 144 BN_init(&m); 145 BN_init(&xr); 146 147 if (!dsa->p || !dsa->q || !dsa->g) { 148 reason = DSA_R_MISSING_PARAMETERS; 149 goto err; 150 } 151 152 s = BN_new(); 153 if (s == NULL) 154 goto err; 155 ctx = BN_CTX_new(); 156 if (ctx == NULL) 157 goto err; 158 redo: 159 if (dsa->kinv == NULL || dsa->r == NULL) { 160 if (!DSA_sign_setup(dsa, ctx, &kinv, &r)) 161 goto err; 162 } else { 163 kinv = dsa->kinv; 164 dsa->kinv = NULL; 165 r = dsa->r; 166 dsa->r = NULL; 167 noredo = 1; 168 } 169 170 171 /* 172 * If the digest length is greater than the size of q use the 173 * BN_num_bits(dsa->q) leftmost bits of the digest, see 174 * fips 186-3, 4.2 175 */ 176 if (dlen > BN_num_bytes(dsa->q)) 177 dlen = BN_num_bytes(dsa->q); 178 if (BN_bin2bn(dgst,dlen,&m) == NULL) 179 goto err; 180 181 /* Compute s = inv(k) (m + xr) mod q */ 182 if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx)) /* s = xr */ 183 goto err; 184 if (!BN_add(s, &xr, &m)) /* s = m + xr */ 185 goto err; 186 if (BN_cmp(s, dsa->q) > 0) 187 if (!BN_sub(s, s, dsa->q)) 188 goto err; 189 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) 190 goto err; 191 192 ret = DSA_SIG_new(); 193 if (ret == NULL) 194 goto err; 195 /* 196 * Redo if r or s is zero as required by FIPS 186-3: this is 197 * very unlikely. 198 */ 199 if (BN_is_zero(r) || BN_is_zero(s)) { 200 if (noredo) { 201 reason = DSA_R_NEED_NEW_SETUP_VALUES; 202 goto err; 203 } 204 goto redo; 205 } 206 ret->r = r; 207 ret->s = s; 208 209 err: 210 if (!ret) { 211 DSAerr(DSA_F_DSA_DO_SIGN, reason); 212 BN_free(r); 213 BN_free(s); 214 } 215 BN_CTX_free(ctx); 216 BN_clear_free(&m); 217 BN_clear_free(&xr); 218 BN_clear_free(kinv); 219 return ret; 220 } 221 222 static int 223 dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, 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, 269 * so we compute g^k using an equivalent exponent of fixed 270 * length. 271 * 272 * (This is a kludge that we need because the BN_mod_exp_mont() 273 * does not let us specify the desired timing behaviour.) 274 */ 275 276 if (!BN_add(&kq, &kq, dsa->q)) 277 goto err; 278 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) { 279 if (!BN_add(&kq, &kq, dsa->q)) 280 goto err; 281 } 282 283 K = &kq; 284 } else { 285 K = &k; 286 } 287 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 288 dsa->method_mont_p); 289 if (!BN_mod(r,r,dsa->q,ctx)) 290 goto err; 291 292 /* Compute part of 's = inv(k) (m + xr) mod q' */ 293 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL) 294 goto err; 295 296 BN_clear_free(*kinvp); 297 *kinvp = kinv; 298 kinv = 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 BN_clear_free(r); 306 } 307 if (ctx_in == NULL) 308 BN_CTX_free(ctx); 309 BN_clear_free(&k); 310 BN_clear_free(&kq); 311 return ret; 312 } 313 314 static int 315 dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, DSA *dsa) 316 { 317 BN_CTX *ctx; 318 BIGNUM u1, u2, t1; 319 BN_MONT_CTX *mont = NULL; 320 int ret = -1, i; 321 322 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 /* Calculate W = inv(S) mod Q 357 * save W in u2 */ 358 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL) 359 goto err; 360 361 /* save M in u1 */ 362 /* 363 * If the digest length is greater than the size of q use the 364 * BN_num_bits(dsa->q) leftmost bits of the digest, see 365 * fips 186-3, 4.2 366 */ 367 if (dgst_len > (i >> 3)) 368 dgst_len = (i >> 3); 369 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL) 370 goto err; 371 372 /* u1 = M * w mod q */ 373 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx)) 374 goto err; 375 376 /* u2 = r * w mod q */ 377 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx)) 378 goto err; 379 380 381 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 /* V is now in u1. If the signature is correct, it will be 396 * equal to R. */ 397 ret = BN_ucmp(&u1, sig->r) == 0; 398 399 err: 400 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 401 there is no error in BN. Test should be ret == -1 (Ben) */ 402 if (ret != 1) 403 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB); 404 BN_CTX_free(ctx); 405 BN_free(&u1); 406 BN_free(&u2); 407 BN_free(&t1); 408 return ret; 409 } 410 411 static int 412 dsa_init(DSA *dsa) 413 { 414 dsa->flags |= DSA_FLAG_CACHE_MONT_P; 415 return 1; 416 } 417 418 static int 419 dsa_finish(DSA *dsa) 420 { 421 BN_MONT_CTX_free(dsa->method_mont_p); 422 return 1; 423 } 424 425