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 70 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 71 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp); 72 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 73 DSA *dsa); 74 static int dsa_init(DSA *dsa); 75 static int dsa_finish(DSA *dsa); 76 77 static DSA_METHOD openssl_dsa_meth = { 78 "OpenSSL DSA method", 79 dsa_do_sign, 80 dsa_sign_setup, 81 dsa_do_verify, 82 NULL, /* dsa_mod_exp, */ 83 NULL, /* dsa_bn_mod_exp, */ 84 dsa_init, 85 dsa_finish, 86 0, 87 NULL, 88 NULL, 89 NULL 90 }; 91 92 /* These macro wrappers replace attempts to use the dsa_mod_exp() and 93 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 94 * having a the macro work as an expression by bundling an "err_instr". So; 95 * 96 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 97 * dsa->method_mont_p)) goto err; 98 * 99 * can be replaced by; 100 * 101 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 102 * dsa->method_mont_p); 103 */ 104 105 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 106 do { \ 107 int _tmp_res53; \ 108 if((dsa)->meth->dsa_mod_exp) \ 109 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \ 110 (a2), (p2), (m), (ctx), (in_mont)); \ 111 else \ 112 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \ 113 (m), (ctx), (in_mont)); \ 114 if(!_tmp_res53) err_instr; \ 115 } while(0) 116 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 117 do { \ 118 int _tmp_res53; \ 119 if((dsa)->meth->bn_mod_exp) \ 120 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \ 121 (m), (ctx), (m_ctx)); \ 122 else \ 123 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \ 124 if(!_tmp_res53) err_instr; \ 125 } while(0) 126 127 const DSA_METHOD *DSA_OpenSSL(void) 128 { 129 return &openssl_dsa_meth; 130 } 131 132 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 133 { 134 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 135 BIGNUM m; 136 BIGNUM xr; 137 BN_CTX *ctx=NULL; 138 int i,reason=ERR_R_BN_LIB; 139 DSA_SIG *ret=NULL; 140 141 BN_init(&m); 142 BN_init(&xr); 143 144 if (!dsa->p || !dsa->q || !dsa->g) 145 { 146 reason=DSA_R_MISSING_PARAMETERS; 147 goto err; 148 } 149 150 s=BN_new(); 151 if (s == NULL) goto err; 152 153 i=BN_num_bytes(dsa->q); /* should be 20 */ 154 if ((dlen > i) || (dlen > 50)) 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 if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err; 176 177 /* Compute s = inv(k) (m + xr) mod q */ 178 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 179 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 180 if (BN_cmp(s,dsa->q) > 0) 181 BN_sub(s,s,dsa->q); 182 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 183 184 ret=DSA_SIG_new(); 185 if (ret == NULL) goto err; 186 ret->r = r; 187 ret->s = s; 188 189 err: 190 if (!ret) 191 { 192 DSAerr(DSA_F_DSA_DO_SIGN,reason); 193 BN_free(r); 194 BN_free(s); 195 } 196 if (ctx != NULL) BN_CTX_free(ctx); 197 BN_clear_free(&m); 198 BN_clear_free(&xr); 199 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 200 BN_clear_free(kinv); 201 return(ret); 202 } 203 204 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 205 { 206 BN_CTX *ctx; 207 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 208 int ret=0; 209 210 if (!dsa->p || !dsa->q || !dsa->g) 211 { 212 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 213 return 0; 214 } 215 216 BN_init(&k); 217 BN_init(&kq); 218 219 if (ctx_in == NULL) 220 { 221 if ((ctx=BN_CTX_new()) == NULL) goto err; 222 } 223 else 224 ctx=ctx_in; 225 226 if ((r=BN_new()) == NULL) goto err; 227 228 /* Get random k */ 229 do 230 if (!BN_rand_range(&k, dsa->q)) goto err; 231 while (BN_is_zero(&k)); 232 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 233 { 234 BN_set_flags(&k, BN_FLG_CONSTTIME); 235 } 236 237 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 238 { 239 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 240 CRYPTO_LOCK_DSA, 241 dsa->p, ctx)) 242 goto err; 243 } 244 245 /* Compute r = (g^k mod p) mod q */ 246 247 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 248 { 249 if (!BN_copy(&kq, &k)) goto err; 250 251 /* We do not want timing information to leak the length of k, 252 * so we compute g^k using an equivalent exponent of fixed length. 253 * 254 * (This is a kludge that we need because the BN_mod_exp_mont() 255 * does not let us specify the desired timing behaviour.) */ 256 257 if (!BN_add(&kq, &kq, dsa->q)) goto err; 258 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 259 { 260 if (!BN_add(&kq, &kq, dsa->q)) goto err; 261 } 262 263 K = &kq; 264 } 265 else 266 { 267 K = &k; 268 } 269 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 270 dsa->method_mont_p); 271 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 272 273 /* Compute part of 's = inv(k) (m + xr) mod q' */ 274 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 275 276 if (*kinvp != NULL) BN_clear_free(*kinvp); 277 *kinvp=kinv; 278 kinv=NULL; 279 if (*rp != NULL) BN_clear_free(*rp); 280 *rp=r; 281 ret=1; 282 err: 283 if (!ret) 284 { 285 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 286 if (kinv != NULL) BN_clear_free(kinv); 287 if (r != NULL) BN_clear_free(r); 288 } 289 if (ctx_in == NULL) BN_CTX_free(ctx); 290 if (kinv != NULL) BN_clear_free(kinv); 291 BN_clear_free(&k); 292 BN_clear_free(&kq); 293 return(ret); 294 } 295 296 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 297 DSA *dsa) 298 { 299 BN_CTX *ctx; 300 BIGNUM u1,u2,t1; 301 BN_MONT_CTX *mont=NULL; 302 int ret = -1; 303 if (!dsa->p || !dsa->q || !dsa->g) 304 { 305 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 306 return -1; 307 } 308 309 if (BN_num_bits(dsa->q) != 160) 310 { 311 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 312 return -1; 313 } 314 315 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 316 { 317 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 318 return -1; 319 } 320 321 BN_init(&u1); 322 BN_init(&u2); 323 BN_init(&t1); 324 325 if ((ctx=BN_CTX_new()) == NULL) goto err; 326 327 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 328 BN_ucmp(sig->r, dsa->q) >= 0) 329 { 330 ret = 0; 331 goto err; 332 } 333 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 334 BN_ucmp(sig->s, dsa->q) >= 0) 335 { 336 ret = 0; 337 goto err; 338 } 339 340 /* Calculate W = inv(S) mod Q 341 * save W in u2 */ 342 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 343 344 /* save M in u1 */ 345 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 346 347 /* u1 = M * w mod q */ 348 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 349 350 /* u2 = r * w mod q */ 351 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 352 353 354 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 355 { 356 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 357 CRYPTO_LOCK_DSA, dsa->p, ctx); 358 if (!mont) 359 goto err; 360 } 361 362 363 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 364 /* BN_copy(&u1,&t1); */ 365 /* let u1 = u1 mod q */ 366 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 367 368 /* V is now in u1. If the signature is correct, it will be 369 * equal to R. */ 370 ret=(BN_ucmp(&u1, sig->r) == 0); 371 372 err: 373 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 374 there is no error in BN. Test should be ret == -1 (Ben) */ 375 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 376 if (ctx != NULL) BN_CTX_free(ctx); 377 BN_free(&u1); 378 BN_free(&u2); 379 BN_free(&t1); 380 return(ret); 381 } 382 383 static int dsa_init(DSA *dsa) 384 { 385 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 386 return(1); 387 } 388 389 static int dsa_finish(DSA *dsa) 390 { 391 if(dsa->method_mont_p) 392 BN_MONT_CTX_free(dsa->method_mont_p); 393 return(1); 394 } 395 396 #endif 397