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, 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 ctx=BN_CTX_new(); 152 if (ctx == NULL) goto err; 153 154 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 155 { 156 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 157 } 158 else 159 { 160 kinv=dsa->kinv; 161 dsa->kinv=NULL; 162 r=dsa->r; 163 dsa->r=NULL; 164 } 165 166 167 if (dlen > BN_num_bytes(dsa->q)) 168 /* if the digest length is greater than the size of q use the 169 * BN_num_bits(dsa->q) leftmost bits of the digest, see 170 * fips 186-3, 4.2 */ 171 dlen = BN_num_bytes(dsa->q); 172 if (BN_bin2bn(dgst,dlen,&m) == NULL) 173 goto err; 174 175 /* Compute s = inv(k) (m + xr) mod q */ 176 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 177 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 178 if (BN_cmp(s,dsa->q) > 0) 179 if (!BN_sub(s,s,dsa->q)) goto err; 180 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 181 182 ret=DSA_SIG_new(); 183 if (ret == NULL) goto err; 184 ret->r = r; 185 ret->s = s; 186 187 err: 188 if (!ret) 189 { 190 DSAerr(DSA_F_DSA_DO_SIGN,reason); 191 BN_free(r); 192 BN_free(s); 193 } 194 if (ctx != NULL) BN_CTX_free(ctx); 195 BN_clear_free(&m); 196 BN_clear_free(&xr); 197 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 198 BN_clear_free(kinv); 199 return(ret); 200 } 201 202 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 203 { 204 BN_CTX *ctx; 205 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 206 int ret=0; 207 208 if (!dsa->p || !dsa->q || !dsa->g) 209 { 210 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 211 return 0; 212 } 213 214 BN_init(&k); 215 BN_init(&kq); 216 217 if (ctx_in == NULL) 218 { 219 if ((ctx=BN_CTX_new()) == NULL) goto err; 220 } 221 else 222 ctx=ctx_in; 223 224 if ((r=BN_new()) == NULL) goto err; 225 226 /* Get random k */ 227 do 228 if (!BN_rand_range(&k, dsa->q)) goto err; 229 while (BN_is_zero(&k)); 230 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 231 { 232 BN_set_flags(&k, BN_FLG_CONSTTIME); 233 } 234 235 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 236 { 237 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 238 CRYPTO_LOCK_DSA, 239 dsa->p, ctx)) 240 goto err; 241 } 242 243 /* Compute r = (g^k mod p) mod q */ 244 245 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 246 { 247 if (!BN_copy(&kq, &k)) goto err; 248 249 /* We do not want timing information to leak the length of k, 250 * so we compute g^k using an equivalent exponent of fixed length. 251 * 252 * (This is a kludge that we need because the BN_mod_exp_mont() 253 * does not let us specify the desired timing behaviour.) */ 254 255 if (!BN_add(&kq, &kq, dsa->q)) goto err; 256 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 257 { 258 if (!BN_add(&kq, &kq, dsa->q)) goto err; 259 } 260 261 K = &kq; 262 } 263 else 264 { 265 K = &k; 266 } 267 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 268 dsa->method_mont_p); 269 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 270 271 /* Compute part of 's = inv(k) (m + xr) mod q' */ 272 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 273 274 if (*kinvp != NULL) BN_clear_free(*kinvp); 275 *kinvp=kinv; 276 kinv=NULL; 277 if (*rp != NULL) BN_clear_free(*rp); 278 *rp=r; 279 ret=1; 280 err: 281 if (!ret) 282 { 283 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 284 if (r != NULL) 285 BN_clear_free(r); 286 } 287 if (ctx_in == NULL) BN_CTX_free(ctx); 288 BN_clear_free(&k); 289 BN_clear_free(&kq); 290 return(ret); 291 } 292 293 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 294 DSA *dsa) 295 { 296 BN_CTX *ctx; 297 BIGNUM u1,u2,t1; 298 BN_MONT_CTX *mont=NULL; 299 int ret = -1, i; 300 if (!dsa->p || !dsa->q || !dsa->g) 301 { 302 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 303 return -1; 304 } 305 306 i = BN_num_bits(dsa->q); 307 /* fips 186-3 allows only different sizes for q */ 308 if (i != 160 && i != 224 && i != 256) 309 { 310 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 311 return -1; 312 } 313 314 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 315 { 316 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 317 return -1; 318 } 319 BN_init(&u1); 320 BN_init(&u2); 321 BN_init(&t1); 322 323 if ((ctx=BN_CTX_new()) == NULL) goto err; 324 325 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 326 BN_ucmp(sig->r, dsa->q) >= 0) 327 { 328 ret = 0; 329 goto err; 330 } 331 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 332 BN_ucmp(sig->s, dsa->q) >= 0) 333 { 334 ret = 0; 335 goto err; 336 } 337 338 /* Calculate W = inv(S) mod Q 339 * save W in u2 */ 340 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 341 342 /* save M in u1 */ 343 if (dgst_len > (i >> 3)) 344 /* if the digest length is greater than the size of q use the 345 * BN_num_bits(dsa->q) leftmost bits of the digest, see 346 * fips 186-3, 4.2 */ 347 dgst_len = (i >> 3); 348 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 349 350 /* u1 = M * w mod q */ 351 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 352 353 /* u2 = r * w mod q */ 354 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 355 356 357 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 358 { 359 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 360 CRYPTO_LOCK_DSA, dsa->p, ctx); 361 if (!mont) 362 goto err; 363 } 364 365 366 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 367 /* BN_copy(&u1,&t1); */ 368 /* let u1 = u1 mod q */ 369 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 370 371 /* V is now in u1. If the signature is correct, it will be 372 * equal to R. */ 373 ret=(BN_ucmp(&u1, sig->r) == 0); 374 375 err: 376 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 377 there is no error in BN. Test should be ret == -1 (Ben) */ 378 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 379 if (ctx != NULL) BN_CTX_free(ctx); 380 BN_free(&u1); 381 BN_free(&u2); 382 BN_free(&t1); 383 return(ret); 384 } 385 386 static int dsa_init(DSA *dsa) 387 { 388 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 389 return(1); 390 } 391 392 static int dsa_finish(DSA *dsa) 393 { 394 if(dsa->method_mont_p) 395 BN_MONT_CTX_free(dsa->method_mont_p); 396 return(1); 397 } 398 399
