dsa_ossl.c revision bdfb8ad83da0647e9b9a32792598e8ce7ba3ef4d
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 68static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 69static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp); 70static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 71 DSA *dsa); 72static int dsa_init(DSA *dsa); 73static int dsa_finish(DSA *dsa); 74 75static DSA_METHOD openssl_dsa_meth = { 76"OpenSSL DSA method", 77dsa_do_sign, 78dsa_sign_setup, 79dsa_do_verify, 80NULL, /* dsa_mod_exp, */ 81NULL, /* dsa_bn_mod_exp, */ 82dsa_init, 83dsa_finish, 840, 85NULL, 86NULL, 87NULL 88}; 89 90/* These macro wrappers replace attempts to use the dsa_mod_exp() and 91 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of 92 * having a the macro work as an expression by bundling an "err_instr". So; 93 * 94 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 95 * dsa->method_mont_p)) goto err; 96 * 97 * can be replaced by; 98 * 99 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx, 100 * dsa->method_mont_p); 101 */ 102 103#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \ 104 do { \ 105 int _tmp_res53; \ 106 if((dsa)->meth->dsa_mod_exp) \ 107 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \ 108 (a2), (p2), (m), (ctx), (in_mont)); \ 109 else \ 110 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \ 111 (m), (ctx), (in_mont)); \ 112 if(!_tmp_res53) err_instr; \ 113 } while(0) 114#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \ 115 do { \ 116 int _tmp_res53; \ 117 if((dsa)->meth->bn_mod_exp) \ 118 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \ 119 (m), (ctx), (m_ctx)); \ 120 else \ 121 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \ 122 if(!_tmp_res53) err_instr; \ 123 } while(0) 124 125const DSA_METHOD *DSA_OpenSSL(void) 126{ 127 return &openssl_dsa_meth; 128} 129 130static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 131 { 132 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 133 BIGNUM m; 134 BIGNUM xr; 135 BN_CTX *ctx=NULL; 136 int i,reason=ERR_R_BN_LIB; 137 DSA_SIG *ret=NULL; 138 139 BN_init(&m); 140 BN_init(&xr); 141 142 if (!dsa->p || !dsa->q || !dsa->g) 143 { 144 reason=DSA_R_MISSING_PARAMETERS; 145 goto err; 146 } 147 148 s=BN_new(); 149 if (s == NULL) goto err; 150 151 i=BN_num_bytes(dsa->q); /* should be 20 */ 152 if ((dlen > i) || (dlen > 50)) 153 { 154 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE; 155 goto err; 156 } 157 158 ctx=BN_CTX_new(); 159 if (ctx == NULL) goto err; 160 161 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 162 { 163 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 164 } 165 else 166 { 167 kinv=dsa->kinv; 168 dsa->kinv=NULL; 169 r=dsa->r; 170 dsa->r=NULL; 171 } 172 173 if (BN_bin2bn(dgst,dlen,&m) == NULL) 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 BN_sub(s,s,dsa->q); 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 187err: 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 202static 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; 280err: 281 if (!ret) 282 { 283 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 284 if (kinv != NULL) BN_clear_free(kinv); 285 if (r != NULL) BN_clear_free(r); 286 } 287 if (ctx_in == NULL) BN_CTX_free(ctx); 288 if (kinv != NULL) BN_clear_free(kinv); 289 BN_clear_free(&k); 290 BN_clear_free(&kq); 291 return(ret); 292 } 293 294static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 295 DSA *dsa) 296 { 297 BN_CTX *ctx; 298 BIGNUM u1,u2,t1; 299 BN_MONT_CTX *mont=NULL; 300 int ret = -1; 301 if (!dsa->p || !dsa->q || !dsa->g) 302 { 303 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 304 return -1; 305 } 306 307 if (BN_num_bits(dsa->q) != 160) 308 { 309 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 310 return -1; 311 } 312 313 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 314 { 315 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 316 return -1; 317 } 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 (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 344 345 /* u1 = M * w mod q */ 346 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 347 348 /* u2 = r * w mod q */ 349 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 350 351 352 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 353 { 354 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 355 CRYPTO_LOCK_DSA, dsa->p, ctx); 356 if (!mont) 357 goto err; 358 } 359 360 361 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 362 /* BN_copy(&u1,&t1); */ 363 /* let u1 = u1 mod q */ 364 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 365 366 /* V is now in u1. If the signature is correct, it will be 367 * equal to R. */ 368 ret=(BN_ucmp(&u1, sig->r) == 0); 369 370 err: 371 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 372 there is no error in BN. Test should be ret == -1 (Ben) */ 373 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 374 if (ctx != NULL) BN_CTX_free(ctx); 375 BN_free(&u1); 376 BN_free(&u2); 377 BN_free(&t1); 378 return(ret); 379 } 380 381static int dsa_init(DSA *dsa) 382{ 383 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 384 return(1); 385} 386 387static int dsa_finish(DSA *dsa) 388{ 389 if(dsa->method_mont_p) 390 BN_MONT_CTX_free(dsa->method_mont_p); 391 return(1); 392} 393 394