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 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa); 69 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp); 70 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 71 DSA *dsa); 72 static int dsa_init(DSA *dsa); 73 static int dsa_finish(DSA *dsa); 74 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, 75 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx, 76 BN_MONT_CTX *in_mont); 77 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p, 78 const BIGNUM *m, BN_CTX *ctx, 79 BN_MONT_CTX *m_ctx); 80 81 static DSA_METHOD openssl_dsa_meth = { 82 "OpenSSL DSA method", 83 dsa_do_sign, 84 dsa_sign_setup, 85 dsa_do_verify, 86 dsa_mod_exp, 87 dsa_bn_mod_exp, 88 dsa_init, 89 dsa_finish, 90 0, 91 NULL 92 }; 93 94 const DSA_METHOD *DSA_OpenSSL(void) 95 { 96 return &openssl_dsa_meth; 97 } 98 99 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 100 { 101 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 102 BIGNUM m; 103 BIGNUM xr; 104 BN_CTX *ctx=NULL; 105 int i,reason=ERR_R_BN_LIB; 106 DSA_SIG *ret=NULL; 107 108 BN_init(&m); 109 BN_init(&xr); 110 111 if (!dsa->p || !dsa->q || !dsa->g) 112 { 113 reason=DSA_R_MISSING_PARAMETERS; 114 goto err; 115 } 116 117 s=BN_new(); 118 if (s == NULL) goto err; 119 120 i=BN_num_bytes(dsa->q); /* should be 20 */ 121 if ((dlen > i) || (dlen > 50)) 122 { 123 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE; 124 goto err; 125 } 126 127 ctx=BN_CTX_new(); 128 if (ctx == NULL) goto err; 129 130 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 131 { 132 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 133 } 134 else 135 { 136 kinv=dsa->kinv; 137 dsa->kinv=NULL; 138 r=dsa->r; 139 dsa->r=NULL; 140 } 141 142 if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err; 143 144 /* Compute s = inv(k) (m + xr) mod q */ 145 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 146 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 147 if (BN_cmp(s,dsa->q) > 0) 148 BN_sub(s,s,dsa->q); 149 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 150 151 ret=DSA_SIG_new(); 152 if (ret == NULL) goto err; 153 ret->r = r; 154 ret->s = s; 155 156 err: 157 if (!ret) 158 { 159 DSAerr(DSA_F_DSA_DO_SIGN,reason); 160 BN_free(r); 161 BN_free(s); 162 } 163 if (ctx != NULL) BN_CTX_free(ctx); 164 BN_clear_free(&m); 165 BN_clear_free(&xr); 166 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 167 BN_clear_free(kinv); 168 return(ret); 169 } 170 171 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 172 { 173 BN_CTX *ctx; 174 BIGNUM k,*kinv=NULL,*r=NULL; 175 int ret=0; 176 177 if (!dsa->p || !dsa->q || !dsa->g) 178 { 179 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS); 180 return 0; 181 } 182 183 BN_init(&k); 184 185 if (ctx_in == NULL) 186 { 187 if ((ctx=BN_CTX_new()) == NULL) goto err; 188 } 189 else 190 ctx=ctx_in; 191 192 if ((r=BN_new()) == NULL) goto err; 193 kinv=NULL; 194 195 /* Get random k */ 196 do 197 if (!BN_rand_range(&k, dsa->q)) goto err; 198 while (BN_is_zero(&k)); 199 200 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) 201 { 202 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL) 203 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p, 204 dsa->p,ctx)) goto err; 205 } 206 207 /* Compute r = (g^k mod p) mod q */ 208 if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx, 209 (BN_MONT_CTX *)dsa->method_mont_p)) goto err; 210 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 211 212 /* Compute part of 's = inv(k) (m + xr) mod q' */ 213 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 214 215 if (*kinvp != NULL) BN_clear_free(*kinvp); 216 *kinvp=kinv; 217 kinv=NULL; 218 if (*rp != NULL) BN_clear_free(*rp); 219 *rp=r; 220 ret=1; 221 err: 222 if (!ret) 223 { 224 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 225 if (kinv != NULL) BN_clear_free(kinv); 226 if (r != NULL) BN_clear_free(r); 227 } 228 if (ctx_in == NULL) BN_CTX_free(ctx); 229 if (kinv != NULL) BN_clear_free(kinv); 230 BN_clear_free(&k); 231 return(ret); 232 } 233 234 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, 235 DSA *dsa) 236 { 237 BN_CTX *ctx; 238 BIGNUM u1,u2,t1; 239 BN_MONT_CTX *mont=NULL; 240 int ret = -1; 241 if (!dsa->p || !dsa->q || !dsa->g) 242 { 243 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); 244 return -1; 245 } 246 247 BN_init(&u1); 248 BN_init(&u2); 249 BN_init(&t1); 250 251 if ((ctx=BN_CTX_new()) == NULL) goto err; 252 253 if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0) 254 { 255 ret = 0; 256 goto err; 257 } 258 if (BN_is_zero(sig->s) || sig->s->neg || BN_ucmp(sig->s, dsa->q) >= 0) 259 { 260 ret = 0; 261 goto err; 262 } 263 264 /* Calculate W = inv(S) mod Q 265 * save W in u2 */ 266 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err; 267 268 /* save M in u1 */ 269 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; 270 271 /* u1 = M * w mod q */ 272 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; 273 274 /* u2 = r * w mod q */ 275 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; 276 277 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) 278 { 279 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL) 280 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p, 281 dsa->p,ctx)) goto err; 282 } 283 mont=(BN_MONT_CTX *)dsa->method_mont_p; 284 285 #if 0 286 { 287 BIGNUM t2; 288 289 BN_init(&t2); 290 /* v = ( g^u1 * y^u2 mod p ) mod q */ 291 /* let t1 = g ^ u1 mod p */ 292 if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err; 293 /* let t2 = y ^ u2 mod p */ 294 if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err; 295 /* let u1 = t1 * t2 mod p */ 296 if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn; 297 BN_free(&t2); 298 } 299 /* let u1 = u1 mod q */ 300 if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err; 301 #else 302 { 303 if (!dsa->meth->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2, 304 dsa->p,ctx,mont)) goto err; 305 /* BN_copy(&u1,&t1); */ 306 /* let u1 = u1 mod q */ 307 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; 308 } 309 #endif 310 /* V is now in u1. If the signature is correct, it will be 311 * equal to R. */ 312 ret=(BN_ucmp(&u1, sig->r) == 0); 313 314 err: 315 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); 316 if (ctx != NULL) BN_CTX_free(ctx); 317 BN_free(&u1); 318 BN_free(&u2); 319 BN_free(&t1); 320 return(ret); 321 } 322 323 static int dsa_init(DSA *dsa) 324 { 325 dsa->flags|=DSA_FLAG_CACHE_MONT_P; 326 return(1); 327 } 328 329 static int dsa_finish(DSA *dsa) 330 { 331 if(dsa->method_mont_p) 332 BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p); 333 return(1); 334 } 335 336 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, 337 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx, 338 BN_MONT_CTX *in_mont) 339 { 340 return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont); 341 } 342 343 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p, 344 const BIGNUM *m, BN_CTX *ctx, 345 BN_MONT_CTX *m_ctx) 346 { 347 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 348 } 349