1 /* $OpenBSD: dsa_ossl.c,v 1.22 2014/10/18 17:20:40 jsing 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/sha.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, DSA_SIG *sig, 73 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 .name = "OpenSSL DSA method", 79 .dsa_do_sign = dsa_do_sign, 80 .dsa_sign_setup = dsa_sign_setup, 81 .dsa_do_verify = dsa_do_verify, 82 .init = dsa_init, 83 .finish = dsa_finish 84 }; 85 86 /* 87 * These macro wrappers replace attempts to use the dsa_mod_exp() and 88 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 89 * having a the macro work as an expression by bundling an "err_instr". So; 90 * 91 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 92 * dsa->method_mont_p)) goto err; 93 * 94 * can be replaced by; 95 * 96 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 97 * dsa->method_mont_p); 98 */ 99 100 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 101 do { \ 102 int _tmp_res53; \ 103 if ((dsa)->meth->dsa_mod_exp) \ 104 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), \ 105 (a1), (p1), (a2), (p2), (m), (ctx), (in_mont)); \ 106 else \ 107 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), \ 108 (p1), (a2), (p2), (m), (ctx), (in_mont)); \ 109 if (!_tmp_res53) \ 110 err_instr; \ 111 } while(0) 112 113 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 114 do { \ 115 int _tmp_res53; \ 116 if ((dsa)->meth->bn_mod_exp) \ 117 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), \ 118 (a), (p), (m), (ctx), (m_ctx)); \ 119 else \ 120 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), \ 121 (ctx), (m_ctx)); \ 122 if (!_tmp_res53) \ 123 err_instr; \ 124 } while(0) 125 126 const DSA_METHOD * 127 DSA_OpenSSL(void) 128 { 129 return &openssl_dsa_meth; 130 } 131 132 static DSA_SIG * 133 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 } 168 169 170 /* 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 173 * fips 186-3, 4.2 174 */ 175 if (dlen > BN_num_bytes(dsa->q)) 176 dlen = BN_num_bytes(dsa->q); 177 if (BN_bin2bn(dgst,dlen,&m) == NULL) 178 goto err; 179 180 /* Compute s = inv(k) (m + xr) mod q */ 181 if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx)) /* s = xr */ 182 goto err; 183 if (!BN_add(s, &xr, &m)) /* s = m + xr */ 184 goto err; 185 if (BN_cmp(s, dsa->q) > 0) 186 if (!BN_sub(s, s, dsa->q)) 187 goto err; 188 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) 189 goto err; 190 191 ret = DSA_SIG_new(); 192 if (ret == NULL) 193 goto err; 194 /* 195 * Redo if r or s is zero as required by FIPS 186-3: this is 196 * very unlikely. 197 */ 198 if (BN_is_zero(r) || BN_is_zero(s)) { 199 if (noredo) { 200 reason = DSA_R_NEED_NEW_SETUP_VALUES; 201 goto err; 202 } 203 goto redo; 204 } 205 ret->r = r; 206 ret->s = s; 207 208 err: 209 if (!ret) { 210 DSAerr(DSA_F_DSA_DO_SIGN, reason); 211 BN_free(r); 212 BN_free(s); 213 } 214 BN_CTX_free(ctx); 215 BN_clear_free(&m); 216 BN_clear_free(&xr); 217 BN_clear_free(kinv); 218 return ret; 219 } 220 221 static int 222 dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 223 { 224 BN_CTX *ctx; 225 BIGNUM k, kq, *K, *kinv = NULL, *r = NULL; 226 int ret = 0; 227 228 if (!dsa->p || !dsa->q || !dsa->g) { 229 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS); 230 return 0; 231 } 232 233 BN_init(&k); 234 BN_init(&kq); 235 236 if (ctx_in == NULL) { 237 if ((ctx = BN_CTX_new()) == NULL) 238 goto err; 239 } else 240 ctx = ctx_in; 241 242 if ((r = BN_new()) == NULL) 243 goto err; 244 245 /* Get random k */ 246 do { 247 if (!BN_rand_range(&k, dsa->q)) 248 goto err; 249 } while (BN_is_zero(&k)); 250 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { 251 BN_set_flags(&k, BN_FLG_CONSTTIME); 252 } 253 254 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { 255 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 256 CRYPTO_LOCK_DSA, dsa->p, ctx)) 257 goto err; 258 } 259 260 /* Compute r = (g^k mod p) mod q */ 261 262 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) { 263 if (!BN_copy(&kq, &k)) 264 goto err; 265 266 /* 267 * We do not want timing information to leak the length of k, 268 * so we compute g^k using an equivalent exponent of fixed 269 * length. 270 * 271 * (This is a kludge that we need because the BN_mod_exp_mont() 272 * does not let us specify the desired timing behaviour.) 273 */ 274 275 if (!BN_add(&kq, &kq, dsa->q)) 276 goto err; 277 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) { 278 if (!BN_add(&kq, &kq, dsa->q)) 279 goto err; 280 } 281 282 K = &kq; 283 } else { 284 K = &k; 285 } 286 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 287 dsa->method_mont_p); 288 if (!BN_mod(r,r,dsa->q,ctx)) 289 goto err; 290 291 /* Compute part of 's = inv(k) (m + xr) mod q' */ 292 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL) 293 goto err; 294 295 BN_clear_free(*kinvp); 296 *kinvp = kinv; 297 kinv = NULL; 298 BN_clear_free(*rp); 299 *rp = r; 300 ret = 1; 301 err: 302 if (!ret) { 303 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB); 304 BN_clear_free(r); 305 } 306 if (ctx_in == NULL) 307 BN_CTX_free(ctx); 308 BN_clear_free(&k); 309 BN_clear_free(&kq); 310 return ret; 311 } 312 313 static int 314 dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, DSA *dsa) 315 { 316 BN_CTX *ctx; 317 BIGNUM u1, u2, t1; 318 BN_MONT_CTX *mont = NULL; 319 int ret = -1, i; 320 321 if (!dsa->p || !dsa->q || !dsa->g) { 322 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS); 323 return -1; 324 } 325 326 i = BN_num_bits(dsa->q); 327 /* fips 186-3 allows only different sizes for q */ 328 if (i != 160 && i != 224 && i != 256) { 329 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE); 330 return -1; 331 } 332 333 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) { 334 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE); 335 return -1; 336 } 337 BN_init(&u1); 338 BN_init(&u2); 339 BN_init(&t1); 340 341 if ((ctx = BN_CTX_new()) == NULL) 342 goto err; 343 344 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 345 BN_ucmp(sig->r, dsa->q) >= 0) { 346 ret = 0; 347 goto err; 348 } 349 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 350 BN_ucmp(sig->s, dsa->q) >= 0) { 351 ret = 0; 352 goto err; 353 } 354 355 /* Calculate W = inv(S) mod Q 356 * save W in u2 */ 357 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL) 358 goto err; 359 360 /* save M in u1 */ 361 /* 362 * If the digest length is greater than the size of q use the 363 * BN_num_bits(dsa->q) leftmost bits of the digest, see 364 * fips 186-3, 4.2 365 */ 366 if (dgst_len > (i >> 3)) 367 dgst_len = (i >> 3); 368 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL) 369 goto err; 370 371 /* u1 = M * w mod q */ 372 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx)) 373 goto err; 374 375 /* u2 = r * w mod q */ 376 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx)) 377 goto err; 378 379 380 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { 381 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 382 CRYPTO_LOCK_DSA, dsa->p, ctx); 383 if (!mont) 384 goto err; 385 } 386 387 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, 388 ctx, mont); 389 /* BN_copy(&u1,&t1); */ 390 /* let u1 = u1 mod q */ 391 if (!BN_mod(&u1, &t1, dsa->q, ctx)) 392 goto err; 393 394 /* V is now in u1. If the signature is correct, it will be 395 * equal to R. */ 396 ret = BN_ucmp(&u1, sig->r) == 0; 397 398 err: 399 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 400 there is no error in BN. Test should be ret == -1 (Ben) */ 401 if (ret != 1) 402 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB); 403 BN_CTX_free(ctx); 404 BN_free(&u1); 405 BN_free(&u2); 406 BN_free(&t1); 407 return ret; 408 } 409 410 static int 411 dsa_init(DSA *dsa) 412 { 413 dsa->flags |= DSA_FLAG_CACHE_MONT_P; 414 return 1; 415 } 416 417 static int 418 dsa_finish(DSA *dsa) 419 { 420 BN_MONT_CTX_free(dsa->method_mont_p); 421 return 1; 422 } 423 424