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 #include <openssl/engine.h> 68 69 int __BN_rand_range(BIGNUM *r, BIGNUM *range); 70 71 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 72 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp); 73 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 74 DSA *dsa); 75 static int dsa_init(DSA *dsa); 76 static int dsa_finish(DSA *dsa); 77 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, 78 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx, 79 BN_MONT_CTX *in_mont); 80 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p, 81 const BIGNUM *m, BN_CTX *ctx, 82 BN_MONT_CTX *m_ctx); 83 84 static DSA_METHOD openssl_dsa_meth = { 85 "OpenSSL DSA method", 86 dsa_do_sign, 87 dsa_sign_setup, 88 dsa_do_verify, 89 dsa_mod_exp, 90 dsa_bn_mod_exp, 91 dsa_init, 92 dsa_finish, 93 0, 94 NULL 95 }; 96 97 DSA_METHOD *DSA_OpenSSL(void) 98 { 99 return &openssl_dsa_meth; 100 } 101 102 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 103 { 104 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 105 BIGNUM m; 106 BIGNUM xr; 107 BN_CTX *ctx=NULL; 108 int i,reason=ERR_R_BN_LIB; 109 DSA_SIG *ret=NULL; 110 111 if (!dsa->p || !dsa->q || !dsa->g) 112 { 113 reason=DSA_R_MISSING_PARAMETERS; 114 goto err; 115 } 116 BN_init(&m); 117 BN_init(&xr); 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,*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 if (ctx_in == NULL) 184 { 185 if ((ctx=BN_CTX_new()) == NULL) goto err; 186 } 187 else 188 ctx=ctx_in; 189 190 BN_init(&k); 191 if ((r=BN_new()) == NULL) goto err; 192 kinv=NULL; 193 194 /* Get random k */ 195 do 196 if (!__BN_rand_range(&k, dsa->q)) goto err; 197 while (BN_is_zero(&k)); 198 199 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) 200 { 201 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL) 202 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p, 203 dsa->p,ctx)) goto err; 204 } 205 206 /* Compute r = (g^k mod p) mod q */ 207 if (!ENGINE_get_DSA(dsa->engine)->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 208 (BN_MONT_CTX *)dsa->method_mont_p)) goto err; 209 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 210 211 /* Compute part of 's = inv(k) (m + xr) mod q' */ 212 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 213 214 if (*kinvp != NULL) BN_clear_free(*kinvp); 215 *kinvp=kinv; 216 kinv=NULL; 217 if (*rp != NULL) BN_clear_free(*rp); 218 *rp=r; 219 ret=1; 220 err: 221 if (!ret) 222 { 223 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 224 if (kinv != NULL) BN_clear_free(kinv); 225 if (r != NULL) BN_clear_free(r); 226 } 227 if (ctx_in == NULL) BN_CTX_free(ctx); 228 if (kinv != NULL) BN_clear_free(kinv); 229 BN_clear_free(&k); 230 return(ret); 231 } 232 233 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 234 DSA *dsa) 235 { 236 BN_CTX *ctx; 237 BIGNUM u1,u2,t1; 238 BN_MONT_CTX *mont=NULL; 239 int ret = -1; 240 241 if ((ctx=BN_CTX_new()) == NULL) goto err; 242 BN_init(&u1); 243 BN_init(&u2); 244 BN_init(&t1); 245 246 if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0) 247 { 248 ret = 0; 249 goto err; 250 } 251 if (BN_is_zero(sig->s) || sig->s->neg || BN_ucmp(sig->s, dsa->q) >= 0) 252 { 253 ret = 0; 254 goto err; 255 } 256 257 /* Calculate W = inv(S) mod Q 258 * save W in u2 */ 259 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 260 261 /* save M in u1 */ 262 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 263 264 /* u1 = M * w mod q */ 265 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 266 267 /* u2 = r * w mod q */ 268 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 269 270 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) 271 { 272 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL) 273 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p, 274 dsa->p,ctx)) goto err; 275 } 276 mont=(BN_MONT_CTX *)dsa->method_mont_p; 277 278 #if 0 279 { 280 BIGNUM t2; 281 282 BN_init(&t2); 283 /* v = ( g^u1 * y^u2 mod p ) mod q */ 284 /* let t1 = g ^ u1 mod p */ 285 if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err; 286 /* let t2 = y ^ u2 mod p */ 287 if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err; 288 /* let u1 = t1 * t2 mod p */ 289 if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn; 290 BN_free(&t2); 291 } 292 /* let u1 = u1 mod q */ 293 if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err; 294 #else 295 { 296 if (!ENGINE_get_DSA(dsa->engine)->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2, 297 dsa->p,ctx,mont)) goto err; 298 /* BN_copy(&u1,&t1); */ 299 /* let u1 = u1 mod q */ 300 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 301 } 302 #endif 303 /* V is now in u1. If the signature is correct, it will be 304 * equal to R. */ 305 ret=(BN_ucmp(&u1, sig->r) == 0); 306 307 err: 308 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 309 if (ctx != NULL) BN_CTX_free(ctx); 310 BN_free(&u1); 311 BN_free(&u2); 312 BN_free(&t1); 313 return(ret); 314 } 315 316 static int dsa_init(DSA *dsa) 317 { 318 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 319 return(1); 320 } 321 322 static int dsa_finish(DSA *dsa) 323 { 324 if(dsa->method_mont_p) 325 BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p); 326 return(1); 327 } 328 329 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, 330 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx, 331 BN_MONT_CTX *in_mont) 332 { 333 return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont); 334 } 335 336 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p, 337 const BIGNUM *m, BN_CTX *ctx, 338 BN_MONT_CTX *m_ctx) 339 { 340 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 341 } 342 343 344 /* random number r: 0 <= r < range */ 345 int __BN_rand_range(BIGNUM *r, BIGNUM *range) 346 { 347 int n; 348 349 if (range->neg || BN_is_zero(range)) 350 { 351 /* BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE); */ 352 return 0; 353 } 354 355 n = BN_num_bits(range); /* n > 0 */ 356 357 if (n == 1) 358 { 359 if (!BN_zero(r)) return 0; 360 } 361 else if (BN_is_bit_set(range, n - 2)) 362 { 363 do 364 { 365 /* range = 11..._2, so each iteration succeeds with probability >= .75 */ 366 if (!BN_rand(r, n, -1, 0)) return 0; 367 } 368 while (BN_cmp(r, range) >= 0); 369 } 370 else 371 { 372 /* range = 10..._2, 373 * so 3*range (= 11..._2) is exactly one bit longer than range */ 374 do 375 { 376 if (!BN_rand(r, n + 1, -1, 0)) return 0; 377 /* If r < 3*range, use r := r MOD range 378 * (which is either r, r - range, or r - 2*range). 379 * Otherwise, iterate once more. 380 * Since 3*range = 11..._2, each iteration succeeds with 381 * probability >= .75. */ 382 if (BN_cmp(r ,range) >= 0) 383 { 384 if (!BN_sub(r, r, range)) return 0; 385 if (BN_cmp(r, range) >= 0) 386 if (!BN_sub(r, r, range)) return 0; 387 } 388 } 389 while (BN_cmp(r, range) >= 0); 390 } 391 392 return 1; 393 } 394