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/dsa.h> 65 #include <openssl/rand.h> 66 #include <openssl/asn1.h> 67 68 #ifndef OPENSSL_FIPS 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 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, 76 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx, 77 BN_MONT_CTX *in_mont); 78 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p, 79 const BIGNUM *m, BN_CTX *ctx, 80 BN_MONT_CTX *m_ctx); 81 82 static DSA_METHOD openssl_dsa_meth = { 83 "OpenSSL DSA method", 84 dsa_do_sign, 85 dsa_sign_setup, 86 dsa_do_verify, 87 dsa_mod_exp, 88 dsa_bn_mod_exp, 89 dsa_init, 90 dsa_finish, 91 0, 92 NULL 93 }; 94 95 const DSA_METHOD *DSA_OpenSSL(void) 96 { 97 return &openssl_dsa_meth; 98 } 99 100 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 101 { 102 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 103 BIGNUM m; 104 BIGNUM xr; 105 BN_CTX *ctx=NULL; 106 int i,reason=ERR_R_BN_LIB; 107 DSA_SIG *ret=NULL; 108 109 BN_init(&m); 110 BN_init(&xr); 111 112 if (!dsa->p || !dsa->q || !dsa->g) 113 { 114 reason=DSA_R_MISSING_PARAMETERS; 115 goto err; 116 } 117 118 s=BN_new(); 119 if (s == NULL) goto err; 120 121 i=BN_num_bytes(dsa->q); /* should be 20 */ 122 if ((dlen > i) || (dlen > 50)) 123 { 124 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE; 125 goto err; 126 } 127 128 ctx=BN_CTX_new(); 129 if (ctx == NULL) goto err; 130 131 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 132 { 133 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 134 } 135 else 136 { 137 kinv=dsa->kinv; 138 dsa->kinv=NULL; 139 r=dsa->r; 140 dsa->r=NULL; 141 } 142 143 if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err; 144 145 /* Compute s = inv(k) (m + xr) mod q */ 146 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 147 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 148 if (BN_cmp(s,dsa->q) > 0) 149 BN_sub(s,s,dsa->q); 150 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 151 152 ret=DSA_SIG_new(); 153 if (ret == NULL) goto err; 154 ret->r = r; 155 ret->s = s; 156 157 err: 158 if (!ret) 159 { 160 DSAerr(DSA_F_DSA_DO_SIGN,reason); 161 BN_free(r); 162 BN_free(s); 163 } 164 if (ctx != NULL) BN_CTX_free(ctx); 165 BN_clear_free(&m); 166 BN_clear_free(&xr); 167 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 168 BN_clear_free(kinv); 169 return(ret); 170 } 171 172 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 173 { 174 BN_CTX *ctx; 175 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 176 int ret=0; 177 178 if (!dsa->p || !dsa->q || !dsa->g) 179 { 180 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 181 return 0; 182 } 183 184 BN_init(&k); 185 BN_init(&kq); 186 187 if (ctx_in == NULL) 188 { 189 if ((ctx=BN_CTX_new()) == NULL) goto err; 190 } 191 else 192 ctx=ctx_in; 193 194 if ((r=BN_new()) == NULL) goto err; 195 196 /* Get random k */ 197 do 198 if (!BN_rand_range(&k, dsa->q)) goto err; 199 while (BN_is_zero(&k)); 200 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 201 { 202 BN_set_flags(&k, BN_FLG_EXP_CONSTTIME); 203 } 204 205 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 206 { 207 if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p, 208 CRYPTO_LOCK_DSA, 209 dsa->p, ctx)) 210 goto err; 211 } 212 213 /* Compute r = (g^k mod p) mod q */ 214 215 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 216 { 217 if (!BN_copy(&kq, &k)) goto err; 218 219 /* We do not want timing information to leak the length of k, 220 * so we compute g^k using an equivalent exponent of fixed length. 221 * 222 * (This is a kludge that we need because the BN_mod_exp_mont() 223 * does not let us specify the desired timing behaviour.) */ 224 225 if (!BN_add(&kq, &kq, dsa->q)) goto err; 226 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 227 { 228 if (!BN_add(&kq, &kq, dsa->q)) goto err; 229 } 230 231 K = &kq; 232 } 233 else 234 { 235 K = &k; 236 } 237 if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,K,dsa->p,ctx, 238 (BN_MONT_CTX *)dsa->method_mont_p)) goto err; 239 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 240 241 /* Compute part of 's = inv(k) (m + xr) mod q' */ 242 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 243 244 if (*kinvp != NULL) BN_clear_free(*kinvp); 245 *kinvp=kinv; 246 kinv=NULL; 247 if (*rp != NULL) BN_clear_free(*rp); 248 *rp=r; 249 ret=1; 250 err: 251 if (!ret) 252 { 253 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 254 if (kinv != NULL) BN_clear_free(kinv); 255 if (r != NULL) BN_clear_free(r); 256 } 257 if (ctx_in == NULL) BN_CTX_free(ctx); 258 if (kinv != NULL) BN_clear_free(kinv); 259 BN_clear_free(&k); 260 BN_clear_free(&kq); 261 return(ret); 262 } 263 264 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 265 DSA *dsa) 266 { 267 BN_CTX *ctx; 268 BIGNUM u1,u2,t1; 269 BN_MONT_CTX *mont=NULL; 270 int ret = -1; 271 if (!dsa->p || !dsa->q || !dsa->g) 272 { 273 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 274 return -1; 275 } 276 277 if (BN_num_bits(dsa->q) != 160) 278 { 279 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 280 return -1; 281 } 282 283 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 284 { 285 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 286 return -1; 287 } 288 289 BN_init(&u1); 290 BN_init(&u2); 291 BN_init(&t1); 292 293 if ((ctx=BN_CTX_new()) == NULL) goto err; 294 295 if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0) 296 { 297 ret = 0; 298 goto err; 299 } 300 if (BN_is_zero(sig->s) || sig->s->neg || BN_ucmp(sig->s, dsa->q) >= 0) 301 { 302 ret = 0; 303 goto err; 304 } 305 306 /* Calculate W = inv(S) mod Q 307 * save W in u2 */ 308 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 309 310 /* save M in u1 */ 311 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 312 313 /* u1 = M * w mod q */ 314 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 315 316 /* u2 = r * w mod q */ 317 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 318 319 320 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 321 { 322 mont = BN_MONT_CTX_set_locked( 323 (BN_MONT_CTX **)&dsa->method_mont_p, 324 CRYPTO_LOCK_DSA, dsa->p, ctx); 325 if (!mont) 326 goto err; 327 } 328 329 #if 0 330 { 331 BIGNUM t2; 332 333 BN_init(&t2); 334 /* v = ( g^u1 * y^u2 mod p ) mod q */ 335 /* let t1 = g ^ u1 mod p */ 336 if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err; 337 /* let t2 = y ^ u2 mod p */ 338 if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err; 339 /* let u1 = t1 * t2 mod p */ 340 if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn; 341 BN_free(&t2); 342 } 343 /* let u1 = u1 mod q */ 344 if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err; 345 #else 346 { 347 if (!dsa->meth->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2, 348 dsa->p,ctx,mont)) goto err; 349 /* BN_copy(&u1,&t1); */ 350 /* let u1 = u1 mod q */ 351 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 352 } 353 #endif 354 /* V is now in u1. If the signature is correct, it will be 355 * equal to R. */ 356 ret=(BN_ucmp(&u1, sig->r) == 0); 357 358 err: 359 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 360 if (ctx != NULL) BN_CTX_free(ctx); 361 BN_free(&u1); 362 BN_free(&u2); 363 BN_free(&t1); 364 return(ret); 365 } 366 367 static int dsa_init(DSA *dsa) 368 { 369 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 370 return(1); 371 } 372 373 static int dsa_finish(DSA *dsa) 374 { 375 if(dsa->method_mont_p) 376 BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p); 377 return(1); 378 } 379 380 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, 381 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx, 382 BN_MONT_CTX *in_mont) 383 { 384 return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont); 385 } 386 387 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p, 388 const BIGNUM *m, BN_CTX *ctx, 389 BN_MONT_CTX *m_ctx) 390 { 391 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 392 } 393 #endif 394