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 .name = "OpenSSL DSA method", 78 .dsa_do_sign = dsa_do_sign, 79 .dsa_sign_setup = dsa_sign_setup, 80 .dsa_do_verify = dsa_do_verify, 81 .init = dsa_init, 82 .finish = dsa_finish 83 }; 84 85 /* These macro wrappers replace attempts to use the dsa_mod_exp() and 86 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 87 * having a the macro work as an expression by bundling an "err_instr". So; 88 * 89 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 90 * dsa->method_mont_p)) goto err; 91 * 92 * can be replaced by; 93 * 94 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 95 * dsa->method_mont_p); 96 */ 97 98 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 99 do { \ 100 int _tmp_res53; \ 101 if((dsa)->meth->dsa_mod_exp) \ 102 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \ 103 (a2), (p2), (m), (ctx), (in_mont)); \ 104 else \ 105 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \ 106 (m), (ctx), (in_mont)); \ 107 if(!_tmp_res53) err_instr; \ 108 } while(0) 109 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 110 do { \ 111 int _tmp_res53; \ 112 if((dsa)->meth->bn_mod_exp) \ 113 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \ 114 (m), (ctx), (m_ctx)); \ 115 else \ 116 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \ 117 if(!_tmp_res53) err_instr; \ 118 } while(0) 119 120 const DSA_METHOD *DSA_OpenSSL(void) 121 { 122 return &openssl_dsa_meth; 123 } 124 125 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 126 { 127 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 128 BIGNUM m; 129 BIGNUM xr; 130 BN_CTX *ctx=NULL; 131 int reason=ERR_R_BN_LIB; 132 DSA_SIG *ret=NULL; 133 int noredo = 0; 134 135 BN_init(&m); 136 BN_init(&xr); 137 138 if (!dsa->p || !dsa->q || !dsa->g) 139 { 140 reason=DSA_R_MISSING_PARAMETERS; 141 goto err; 142 } 143 144 s=BN_new(); 145 if (s == NULL) goto err; 146 ctx=BN_CTX_new(); 147 if (ctx == NULL) goto err; 148 redo: 149 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 150 { 151 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 152 } 153 else 154 { 155 kinv=dsa->kinv; 156 dsa->kinv=NULL; 157 r=dsa->r; 158 dsa->r=NULL; 159 noredo = 1; 160 } 161 162 163 if (dlen > BN_num_bytes(dsa->q)) 164 /* if the digest length is greater than the size of q use the 165 * BN_num_bits(dsa->q) leftmost bits of the digest, see 166 * fips 186-3, 4.2 */ 167 dlen = BN_num_bytes(dsa->q); 168 if (BN_bin2bn(dgst,dlen,&m) == NULL) 169 goto err; 170 171 /* Compute s = inv(k) (m + xr) mod q */ 172 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 173 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 174 if (BN_cmp(s,dsa->q) > 0) 175 if (!BN_sub(s,s,dsa->q)) goto err; 176 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 177 178 ret=DSA_SIG_new(); 179 if (ret == NULL) goto err; 180 /* Redo if r or s is zero as required by FIPS 186-3: this is 181 * very unlikely. 182 */ 183 if (BN_is_zero(r) || BN_is_zero(s)) 184 { 185 if (noredo) 186 { 187 reason = DSA_R_NEED_NEW_SETUP_VALUES; 188 goto err; 189 } 190 goto redo; 191 } 192 ret->r = r; 193 ret->s = s; 194 195 err: 196 if (!ret) 197 { 198 DSAerr(DSA_F_DSA_DO_SIGN,reason); 199 BN_free(r); 200 BN_free(s); 201 } 202 if (ctx != NULL) BN_CTX_free(ctx); 203 BN_clear_free(&m); 204 BN_clear_free(&xr); 205 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 206 BN_clear_free(kinv); 207 return(ret); 208 } 209 210 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 211 { 212 BN_CTX *ctx; 213 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 214 int ret=0; 215 216 if (!dsa->p || !dsa->q || !dsa->g) 217 { 218 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 219 return 0; 220 } 221 222 BN_init(&k); 223 BN_init(&kq); 224 225 if (ctx_in == NULL) 226 { 227 if ((ctx=BN_CTX_new()) == NULL) goto err; 228 } 229 else 230 ctx=ctx_in; 231 232 if ((r=BN_new()) == NULL) goto err; 233 234 /* Get random k */ 235 do 236 if (!BN_rand_range(&k, dsa->q)) goto err; 237 while (BN_is_zero(&k)); 238 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 239 { 240 BN_set_flags(&k, BN_FLG_CONSTTIME); 241 } 242 243 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 244 { 245 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 246 CRYPTO_LOCK_DSA, 247 dsa->p, ctx)) 248 goto err; 249 } 250 251 /* Compute r = (g^k mod p) mod q */ 252 253 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 254 { 255 if (!BN_copy(&kq, &k)) goto err; 256 257 /* We do not want timing information to leak the length of k, 258 * so we compute g^k using an equivalent exponent of fixed length. 259 * 260 * (This is a kludge that we need because the BN_mod_exp_mont() 261 * does not let us specify the desired timing behaviour.) */ 262 263 if (!BN_add(&kq, &kq, dsa->q)) goto err; 264 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 265 { 266 if (!BN_add(&kq, &kq, dsa->q)) goto err; 267 } 268 269 K = &kq; 270 } 271 else 272 { 273 K = &k; 274 } 275 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 276 dsa->method_mont_p); 277 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 278 279 /* Compute part of 's = inv(k) (m + xr) mod q' */ 280 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 281 282 if (*kinvp != NULL) BN_clear_free(*kinvp); 283 *kinvp=kinv; 284 kinv=NULL; 285 if (*rp != NULL) BN_clear_free(*rp); 286 *rp=r; 287 ret=1; 288 err: 289 if (!ret) 290 { 291 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 292 if (r != NULL) 293 BN_clear_free(r); 294 } 295 if (ctx_in == NULL) BN_CTX_free(ctx); 296 BN_clear_free(&k); 297 BN_clear_free(&kq); 298 return(ret); 299 } 300 301 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 302 DSA *dsa) 303 { 304 BN_CTX *ctx; 305 BIGNUM u1,u2,t1; 306 BN_MONT_CTX *mont=NULL; 307 int ret = -1, i; 308 if (!dsa->p || !dsa->q || !dsa->g) 309 { 310 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 311 return -1; 312 } 313 314 i = BN_num_bits(dsa->q); 315 /* fips 186-3 allows only different sizes for q */ 316 if (i != 160 && i != 224 && i != 256) 317 { 318 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 319 return -1; 320 } 321 322 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 323 { 324 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 325 return -1; 326 } 327 BN_init(&u1); 328 BN_init(&u2); 329 BN_init(&t1); 330 331 if ((ctx=BN_CTX_new()) == NULL) goto err; 332 333 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 334 BN_ucmp(sig->r, dsa->q) >= 0) 335 { 336 ret = 0; 337 goto err; 338 } 339 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 340 BN_ucmp(sig->s, dsa->q) >= 0) 341 { 342 ret = 0; 343 goto err; 344 } 345 346 /* Calculate W = inv(S) mod Q 347 * save W in u2 */ 348 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 349 350 /* save M in u1 */ 351 if (dgst_len > (i >> 3)) 352 /* if the digest length is greater than the size of q use the 353 * BN_num_bits(dsa->q) leftmost bits of the digest, see 354 * fips 186-3, 4.2 */ 355 dgst_len = (i >> 3); 356 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 357 358 /* u1 = M * w mod q */ 359 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 360 361 /* u2 = r * w mod q */ 362 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 363 364 365 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 366 { 367 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 368 CRYPTO_LOCK_DSA, dsa->p, ctx); 369 if (!mont) 370 goto err; 371 } 372 373 374 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 375 /* BN_copy(&u1,&t1); */ 376 /* let u1 = u1 mod q */ 377 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 378 379 /* V is now in u1. If the signature is correct, it will be 380 * equal to R. */ 381 ret=(BN_ucmp(&u1, sig->r) == 0); 382 383 err: 384 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 385 there is no error in BN. Test should be ret == -1 (Ben) */ 386 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 387 if (ctx != NULL) BN_CTX_free(ctx); 388 BN_free(&u1); 389 BN_free(&u2); 390 BN_free(&t1); 391 return(ret); 392 } 393 394 static int dsa_init(DSA *dsa) 395 { 396 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 397 return(1); 398 } 399 400 static int dsa_finish(DSA *dsa) 401 { 402 if(dsa->method_mont_p) 403 BN_MONT_CTX_free(dsa->method_mont_p); 404 return(1); 405 } 406 407