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