1 /* crypto/dsa/dsa_ossl.c */ 2 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay (at) 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 (at) 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 (at) 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 (at) 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 (at) 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, 71 BIGNUM **kinvp, BIGNUM **rp, 72 const unsigned char *dgst, int dlen); 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 "OpenSSL DSA method", 80 dsa_do_sign, 81 dsa_sign_setup, 82 dsa_do_verify, 83 NULL, /* dsa_mod_exp, */ 84 NULL, /* dsa_bn_mod_exp, */ 85 dsa_init, 86 dsa_finish, 87 0, 88 NULL, 89 NULL, 90 NULL 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 { 148 reason=DSA_R_MISSING_PARAMETERS; 149 goto err; 150 } 151 152 s=BN_new(); 153 if (s == NULL) goto err; 154 ctx=BN_CTX_new(); 155 if (ctx == NULL) goto err; 156 redo: 157 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 158 { 159 if (!dsa->meth->dsa_sign_setup(dsa,ctx,&kinv,&r,dgst,dlen)) 160 goto err; 161 } 162 else 163 { 164 kinv=dsa->kinv; 165 dsa->kinv=NULL; 166 r=dsa->r; 167 dsa->r=NULL; 168 noredo = 1; 169 } 170 171 172 if (dlen > BN_num_bytes(dsa->q)) 173 /* if the digest length is greater than the size of q use the 174 * BN_num_bits(dsa->q) leftmost bits of the digest, see 175 * fips 186-3, 4.2 */ 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)) goto err;/* s = xr */ 182 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 183 if (BN_cmp(s,dsa->q) > 0) 184 if (!BN_sub(s,s,dsa->q)) goto err; 185 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 186 187 ret=DSA_SIG_new(); 188 if (ret == NULL) goto err; 189 /* Redo if r or s is zero as required by FIPS 186-3: this is 190 * very unlikely. 191 */ 192 if (BN_is_zero(r) || BN_is_zero(s)) 193 { 194 if (noredo) 195 { 196 reason = DSA_R_NEED_NEW_SETUP_VALUES; 197 goto err; 198 } 199 goto redo; 200 } 201 ret->r = r; 202 ret->s = s; 203 204 err: 205 if (!ret) 206 { 207 DSAerr(DSA_F_DSA_DO_SIGN,reason); 208 BN_free(r); 209 BN_free(s); 210 } 211 if (ctx != NULL) BN_CTX_free(ctx); 212 BN_clear_free(&m); 213 BN_clear_free(&xr); 214 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 215 BN_clear_free(kinv); 216 return(ret); 217 } 218 219 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, 220 BIGNUM **kinvp, BIGNUM **rp, 221 const unsigned char *dgst, int dlen) 222 { 223 BN_CTX *ctx; 224 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 225 int ret=0; 226 227 if (!dsa->p || !dsa->q || !dsa->g) 228 { 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 { 238 if ((ctx=BN_CTX_new()) == NULL) goto err; 239 } 240 else 241 ctx=ctx_in; 242 243 if ((r=BN_new()) == NULL) goto err; 244 245 /* Get random k */ 246 do 247 { 248 #ifndef OPENSSL_NO_SHA512 249 if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH) 250 { 251 /* If DSA_FLAG_NONCE_FROM_HASH is set then we calculate k from 252 * SHA512(private_key + H(message) + random). This protects the 253 * private key from a weak PRNG. */ 254 if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst, 255 dlen, ctx)) 256 goto err; 257 } 258 else 259 #endif 260 if (!BN_rand_range(&k, dsa->q)) goto err; 261 } while (BN_is_zero(&k)); 262 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 263 { 264 BN_set_flags(&k, BN_FLG_CONSTTIME); 265 } 266 267 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 268 { 269 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 270 CRYPTO_LOCK_DSA, 271 dsa->p, ctx)) 272 goto err; 273 } 274 275 /* Compute r = (g^k mod p) mod q */ 276 277 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 278 { 279 if (!BN_copy(&kq, &k)) goto err; 280 281 /* We do not want timing information to leak the length of k, 282 * so we compute g^k using an equivalent exponent of fixed length. 283 * 284 * (This is a kludge that we need because the BN_mod_exp_mont() 285 * does not let us specify the desired timing behaviour.) */ 286 287 if (!BN_add(&kq, &kq, dsa->q)) goto err; 288 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 289 { 290 if (!BN_add(&kq, &kq, dsa->q)) goto err; 291 } 292 293 K = &kq; 294 } 295 else 296 { 297 K = &k; 298 } 299 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 300 dsa->method_mont_p); 301 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 302 303 /* Compute part of 's = inv(k) (m + xr) mod q' */ 304 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 305 306 if (*kinvp != NULL) BN_clear_free(*kinvp); 307 *kinvp=kinv; 308 kinv=NULL; 309 if (*rp != NULL) BN_clear_free(*rp); 310 *rp=r; 311 ret=1; 312 err: 313 if (!ret) 314 { 315 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 316 if (r != NULL) 317 BN_clear_free(r); 318 } 319 if (ctx_in == NULL) BN_CTX_free(ctx); 320 BN_clear_free(&k); 321 BN_clear_free(&kq); 322 return(ret); 323 } 324 325 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 326 DSA *dsa) 327 { 328 BN_CTX *ctx; 329 BIGNUM u1,u2,t1; 330 BN_MONT_CTX *mont=NULL; 331 int ret = -1, i; 332 if (!dsa->p || !dsa->q || !dsa->g) 333 { 334 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 335 return -1; 336 } 337 338 i = BN_num_bits(dsa->q); 339 /* fips 186-3 allows only different sizes for q */ 340 if (i != 160 && i != 224 && i != 256) 341 { 342 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 343 return -1; 344 } 345 346 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 347 { 348 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 349 return -1; 350 } 351 BN_init(&u1); 352 BN_init(&u2); 353 BN_init(&t1); 354 355 if ((ctx=BN_CTX_new()) == NULL) goto err; 356 357 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 358 BN_ucmp(sig->r, dsa->q) >= 0) 359 { 360 ret = 0; 361 goto err; 362 } 363 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 364 BN_ucmp(sig->s, dsa->q) >= 0) 365 { 366 ret = 0; 367 goto err; 368 } 369 370 /* Calculate W = inv(S) mod Q 371 * save W in u2 */ 372 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 373 374 /* save M in u1 */ 375 if (dgst_len > (i >> 3)) 376 /* if the digest length is greater than the size of q use the 377 * BN_num_bits(dsa->q) leftmost bits of the digest, see 378 * fips 186-3, 4.2 */ 379 dgst_len = (i >> 3); 380 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 381 382 /* u1 = M * w mod q */ 383 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 384 385 /* u2 = r * w mod q */ 386 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 387 388 389 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 390 { 391 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 392 CRYPTO_LOCK_DSA, dsa->p, ctx); 393 if (!mont) 394 goto err; 395 } 396 397 398 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 399 /* BN_copy(&u1,&t1); */ 400 /* let u1 = u1 mod q */ 401 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 402 403 /* V is now in u1. If the signature is correct, it will be 404 * equal to R. */ 405 ret=(BN_ucmp(&u1, sig->r) == 0); 406 407 err: 408 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 409 there is no error in BN. Test should be ret == -1 (Ben) */ 410 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 411 if (ctx != NULL) BN_CTX_free(ctx); 412 BN_free(&u1); 413 BN_free(&u2); 414 BN_free(&t1); 415 return(ret); 416 } 417 418 static int dsa_init(DSA *dsa) 419 { 420 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 421 return(1); 422 } 423 424 static int dsa_finish(DSA *dsa) 425 { 426 if(dsa->method_mont_p) 427 BN_MONT_CTX_free(dsa->method_mont_p); 428 return(1); 429 } 430 431
