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, BIGNUM **rp); 71 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 72 DSA *dsa); 73 static int dsa_init(DSA *dsa); 74 static int dsa_finish(DSA *dsa); 75 76 static DSA_METHOD openssl_dsa_meth = { 77 "OpenSSL DSA method", 78 dsa_do_sign, 79 dsa_sign_setup, 80 dsa_do_verify, 81 NULL, /* dsa_mod_exp, */ 82 NULL, /* dsa_bn_mod_exp, */ 83 dsa_init, 84 dsa_finish, 85 0, 86 NULL, 87 NULL, 88 NULL 89 }; 90 91 /* These macro wrappers replace attempts to use the dsa_mod_exp() and 92 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 93 * having a the macro work as an expression by bundling an "err_instr". So; 94 * 95 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 96 * dsa->method_mont_p)) goto err; 97 * 98 * can be replaced by; 99 * 100 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 101 * dsa->method_mont_p); 102 */ 103 104 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 105 do { \ 106 int _tmp_res53; \ 107 if((dsa)->meth->dsa_mod_exp) \ 108 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \ 109 (a2), (p2), (m), (ctx), (in_mont)); \ 110 else \ 111 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \ 112 (m), (ctx), (in_mont)); \ 113 if(!_tmp_res53) err_instr; \ 114 } while(0) 115 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 116 do { \ 117 int _tmp_res53; \ 118 if((dsa)->meth->bn_mod_exp) \ 119 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \ 120 (m), (ctx), (m_ctx)); \ 121 else \ 122 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \ 123 if(!_tmp_res53) err_instr; \ 124 } while(0) 125 126 const DSA_METHOD *DSA_OpenSSL(void) 127 { 128 return &openssl_dsa_meth; 129 } 130 131 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 132 { 133 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 134 BIGNUM m; 135 BIGNUM xr; 136 BN_CTX *ctx=NULL; 137 int reason=ERR_R_BN_LIB; 138 DSA_SIG *ret=NULL; 139 140 BN_init(&m); 141 BN_init(&xr); 142 143 if (!dsa->p || !dsa->q || !dsa->g) 144 { 145 reason=DSA_R_MISSING_PARAMETERS; 146 goto err; 147 } 148 149 s=BN_new(); 150 if (s == NULL) goto err; 151 152 /* reject a excessive digest length (currently at most 153 * dsa-with-SHA256 is supported) */ 154 if (dlen > SHA256_DIGEST_LENGTH) 155 { 156 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE; 157 goto err; 158 } 159 160 ctx=BN_CTX_new(); 161 if (ctx == NULL) goto err; 162 163 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 164 { 165 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 166 } 167 else 168 { 169 kinv=dsa->kinv; 170 dsa->kinv=NULL; 171 r=dsa->r; 172 dsa->r=NULL; 173 } 174 175 176 if (dlen > BN_num_bytes(dsa->q)) 177 /* if the digest length is greater than the size of q use the 178 * BN_num_bits(dsa->q) leftmost bits of the digest, see 179 * fips 186-3, 4.2 */ 180 dlen = BN_num_bytes(dsa->q); 181 if (BN_bin2bn(dgst,dlen,&m) == NULL) 182 goto err; 183 184 /* Compute s = inv(k) (m + xr) mod q */ 185 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 186 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 187 if (BN_cmp(s,dsa->q) > 0) 188 BN_sub(s,s,dsa->q); 189 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 190 191 ret=DSA_SIG_new(); 192 if (ret == NULL) goto err; 193 ret->r = r; 194 ret->s = s; 195 196 err: 197 if (!ret) 198 { 199 DSAerr(DSA_F_DSA_DO_SIGN,reason); 200 BN_free(r); 201 BN_free(s); 202 } 203 if (ctx != NULL) BN_CTX_free(ctx); 204 BN_clear_free(&m); 205 BN_clear_free(&xr); 206 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 207 BN_clear_free(kinv); 208 return(ret); 209 } 210 211 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 212 { 213 BN_CTX *ctx; 214 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 215 int ret=0; 216 217 if (!dsa->p || !dsa->q || !dsa->g) 218 { 219 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 220 return 0; 221 } 222 223 BN_init(&k); 224 BN_init(&kq); 225 226 if (ctx_in == NULL) 227 { 228 if ((ctx=BN_CTX_new()) == NULL) goto err; 229 } 230 else 231 ctx=ctx_in; 232 233 if ((r=BN_new()) == NULL) goto err; 234 235 /* Get random k */ 236 do 237 if (!BN_rand_range(&k, dsa->q)) goto err; 238 while (BN_is_zero(&k)); 239 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 240 { 241 BN_set_flags(&k, BN_FLG_CONSTTIME); 242 } 243 244 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 245 { 246 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 247 CRYPTO_LOCK_DSA, 248 dsa->p, ctx)) 249 goto err; 250 } 251 252 /* Compute r = (g^k mod p) mod q */ 253 254 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 255 { 256 if (!BN_copy(&kq, &k)) goto err; 257 258 /* We do not want timing information to leak the length of k, 259 * so we compute g^k using an equivalent exponent of fixed length. 260 * 261 * (This is a kludge that we need because the BN_mod_exp_mont() 262 * does not let us specify the desired timing behaviour.) */ 263 264 if (!BN_add(&kq, &kq, dsa->q)) goto err; 265 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 266 { 267 if (!BN_add(&kq, &kq, dsa->q)) goto err; 268 } 269 270 K = &kq; 271 } 272 else 273 { 274 K = &k; 275 } 276 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 277 dsa->method_mont_p); 278 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 279 280 /* Compute part of 's = inv(k) (m + xr) mod q' */ 281 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 282 283 if (*kinvp != NULL) BN_clear_free(*kinvp); 284 *kinvp=kinv; 285 kinv=NULL; 286 if (*rp != NULL) BN_clear_free(*rp); 287 *rp=r; 288 ret=1; 289 err: 290 if (!ret) 291 { 292 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 293 if (r != NULL) 294 BN_clear_free(r); 295 } 296 if (ctx_in == NULL) BN_CTX_free(ctx); 297 BN_clear_free(&k); 298 BN_clear_free(&kq); 299 return(ret); 300 } 301 302 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 303 DSA *dsa) 304 { 305 BN_CTX *ctx; 306 BIGNUM u1,u2,t1; 307 BN_MONT_CTX *mont=NULL; 308 int ret = -1, i; 309 if (!dsa->p || !dsa->q || !dsa->g) 310 { 311 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 312 return -1; 313 } 314 315 i = BN_num_bits(dsa->q); 316 /* fips 186-3 allows only different sizes for q */ 317 if (i != 160 && i != 224 && i != 256) 318 { 319 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 320 return -1; 321 } 322 323 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 324 { 325 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 326 return -1; 327 } 328 329 /* reject a excessive digest length (currently at most 330 * dsa-with-SHA256 is supported) */ 331 if (dgst_len > SHA256_DIGEST_LENGTH) 332 { 333 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); 334 return -1; 335 } 336 337 BN_init(&u1); 338 BN_init(&u2); 339 BN_init(&t1); 340 341 if ((ctx=BN_CTX_new()) == NULL) goto err; 342 343 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 344 BN_ucmp(sig->r, dsa->q) >= 0) 345 { 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 { 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) goto err; 359 360 /* save M in u1 */ 361 if (dgst_len > (i >> 3)) 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 dgst_len = (i >> 3); 366 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 367 368 /* u1 = M * w mod q */ 369 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 370 371 /* u2 = r * w mod q */ 372 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 373 374 375 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 376 { 377 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 378 CRYPTO_LOCK_DSA, dsa->p, ctx); 379 if (!mont) 380 goto err; 381 } 382 383 384 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 385 /* BN_copy(&u1,&t1); */ 386 /* let u1 = u1 mod q */ 387 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 388 389 /* V is now in u1. If the signature is correct, it will be 390 * equal to R. */ 391 ret=(BN_ucmp(&u1, sig->r) == 0); 392 393 err: 394 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 395 there is no error in BN. Test should be ret == -1 (Ben) */ 396 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 397 if (ctx != NULL) BN_CTX_free(ctx); 398 BN_free(&u1); 399 BN_free(&u2); 400 BN_free(&t1); 401 return(ret); 402 } 403 404 static int dsa_init(DSA *dsa) 405 { 406 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 407 return(1); 408 } 409 410 static int dsa_finish(DSA *dsa) 411 { 412 if(dsa->method_mont_p) 413 BN_MONT_CTX_free(dsa->method_mont_p); 414 return(1); 415 } 416 417