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 69static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 70static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp); 71static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 72 DSA *dsa); 73static int dsa_init(DSA *dsa); 74static int dsa_finish(DSA *dsa); 75 76static DSA_METHOD openssl_dsa_meth = { 77"OpenSSL DSA method", 78dsa_do_sign, 79dsa_sign_setup, 80dsa_do_verify, 81NULL, /* dsa_mod_exp, */ 82NULL, /* dsa_bn_mod_exp, */ 83dsa_init, 84dsa_finish, 850, 86NULL, 87NULL, 88NULL 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 126const DSA_METHOD *DSA_OpenSSL(void) 127{ 128 return &openssl_dsa_meth; 129} 130 131static 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 int noredo = 0; 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 ctx=BN_CTX_new(); 153 if (ctx == NULL) goto err; 154redo: 155 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 156 { 157 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 158 } 159 else 160 { 161 kinv=dsa->kinv; 162 dsa->kinv=NULL; 163 r=dsa->r; 164 dsa->r=NULL; 165 noredo = 1; 166 } 167 168 169 if (dlen > BN_num_bytes(dsa->q)) 170 /* if the digest length is greater than the size of q use the 171 * BN_num_bits(dsa->q) leftmost bits of the digest, see 172 * fips 186-3, 4.2 */ 173 dlen = BN_num_bytes(dsa->q); 174 if (BN_bin2bn(dgst,dlen,&m) == NULL) 175 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 if (!BN_sub(s,s,dsa->q)) goto err; 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 /* Redo if r or s is zero as required by FIPS 186-3: this is 187 * very unlikely. 188 */ 189 if (BN_is_zero(r) || BN_is_zero(s)) 190 { 191 if (noredo) 192 { 193 reason = DSA_R_NEED_NEW_SETUP_VALUES; 194 goto err; 195 } 196 goto redo; 197 } 198 ret->r = r; 199 ret->s = s; 200 201err: 202 if (!ret) 203 { 204 DSAerr(DSA_F_DSA_DO_SIGN,reason); 205 BN_free(r); 206 BN_free(s); 207 } 208 if (ctx != NULL) BN_CTX_free(ctx); 209 BN_clear_free(&m); 210 BN_clear_free(&xr); 211 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 212 BN_clear_free(kinv); 213 return(ret); 214 } 215 216static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 217 { 218 BN_CTX *ctx; 219 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL; 220 int ret=0; 221 222 if (!dsa->p || !dsa->q || !dsa->g) 223 { 224 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 225 return 0; 226 } 227 228 BN_init(&k); 229 BN_init(&kq); 230 231 if (ctx_in == NULL) 232 { 233 if ((ctx=BN_CTX_new()) == NULL) goto err; 234 } 235 else 236 ctx=ctx_in; 237 238 if ((r=BN_new()) == NULL) goto err; 239 240 /* Get random k */ 241 do 242 if (!BN_rand_range(&k, dsa->q)) goto err; 243 while (BN_is_zero(&k)); 244 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 245 { 246 BN_set_flags(&k, BN_FLG_CONSTTIME); 247 } 248 249 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 250 { 251 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, 252 CRYPTO_LOCK_DSA, 253 dsa->p, ctx)) 254 goto err; 255 } 256 257 /* Compute r = (g^k mod p) mod q */ 258 259 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) 260 { 261 if (!BN_copy(&kq, &k)) goto err; 262 263 /* We do not want timing information to leak the length of k, 264 * so we compute g^k using an equivalent exponent of fixed length. 265 * 266 * (This is a kludge that we need because the BN_mod_exp_mont() 267 * does not let us specify the desired timing behaviour.) */ 268 269 if (!BN_add(&kq, &kq, dsa->q)) goto err; 270 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) 271 { 272 if (!BN_add(&kq, &kq, dsa->q)) goto err; 273 } 274 275 K = &kq; 276 } 277 else 278 { 279 K = &k; 280 } 281 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx, 282 dsa->method_mont_p); 283 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 284 285 /* Compute part of 's = inv(k) (m + xr) mod q' */ 286 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 287 288 if (*kinvp != NULL) BN_clear_free(*kinvp); 289 *kinvp=kinv; 290 kinv=NULL; 291 if (*rp != NULL) BN_clear_free(*rp); 292 *rp=r; 293 ret=1; 294err: 295 if (!ret) 296 { 297 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 298 if (r != NULL) 299 BN_clear_free(r); 300 } 301 if (ctx_in == NULL) BN_CTX_free(ctx); 302 BN_clear_free(&k); 303 BN_clear_free(&kq); 304 return(ret); 305 } 306 307static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 308 DSA *dsa) 309 { 310 BN_CTX *ctx; 311 BIGNUM u1,u2,t1; 312 BN_MONT_CTX *mont=NULL; 313 int ret = -1, i; 314 if (!dsa->p || !dsa->q || !dsa->g) 315 { 316 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 317 return -1; 318 } 319 320 i = BN_num_bits(dsa->q); 321 /* fips 186-3 allows only different sizes for q */ 322 if (i != 160 && i != 224 && i != 256) 323 { 324 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); 325 return -1; 326 } 327 328 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) 329 { 330 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); 331 return -1; 332 } 333 BN_init(&u1); 334 BN_init(&u2); 335 BN_init(&t1); 336 337 if ((ctx=BN_CTX_new()) == NULL) goto err; 338 339 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 340 BN_ucmp(sig->r, dsa->q) >= 0) 341 { 342 ret = 0; 343 goto err; 344 } 345 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || 346 BN_ucmp(sig->s, dsa->q) >= 0) 347 { 348 ret = 0; 349 goto err; 350 } 351 352 /* Calculate W = inv(S) mod Q 353 * save W in u2 */ 354 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 355 356 /* save M in u1 */ 357 if (dgst_len > (i >> 3)) 358 /* if the digest length is greater than the size of q use the 359 * BN_num_bits(dsa->q) leftmost bits of the digest, see 360 * fips 186-3, 4.2 */ 361 dgst_len = (i >> 3); 362 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 363 364 /* u1 = M * w mod q */ 365 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 366 367 /* u2 = r * w mod q */ 368 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 369 370 371 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) 372 { 373 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, 374 CRYPTO_LOCK_DSA, dsa->p, ctx); 375 if (!mont) 376 goto err; 377 } 378 379 380 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); 381 /* BN_copy(&u1,&t1); */ 382 /* let u1 = u1 mod q */ 383 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 384 385 /* V is now in u1. If the signature is correct, it will be 386 * equal to R. */ 387 ret=(BN_ucmp(&u1, sig->r) == 0); 388 389 err: 390 /* XXX: surely this is wrong - if ret is 0, it just didn't verify; 391 there is no error in BN. Test should be ret == -1 (Ben) */ 392 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 393 if (ctx != NULL) BN_CTX_free(ctx); 394 BN_free(&u1); 395 BN_free(&u2); 396 BN_free(&t1); 397 return(ret); 398 } 399 400static int dsa_init(DSA *dsa) 401{ 402 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 403 return(1); 404} 405 406static int dsa_finish(DSA *dsa) 407{ 408 if(dsa->method_mont_p) 409 BN_MONT_CTX_free(dsa->method_mont_p); 410 return(1); 411} 412 413