Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | |
| 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 | |
| 76 | static DSA_METHOD openssl_dsa_meth = { |
| 77 | "OpenSSL DSA method", |
| 78 | dsa_do_sign, |
| 79 | dsa_sign_setup, |
| 80 | dsa_do_verify, |
| 81 | NULL, /* dsa_mod_exp, */ |
| 82 | NULL, /* dsa_bn_mod_exp, */ |
| 83 | dsa_init, |
| 84 | dsa_finish, |
| 85 | 0, |
| 86 | NULL, |
| 87 | NULL, |
| 88 | NULL |
| 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 | |
| 126 | const DSA_METHOD *DSA_OpenSSL(void) |
| 127 | { |
| 128 | return &openssl_dsa_meth; |
| 129 | } |
| 130 | |
| 131 | static 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; |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 139 | |
| 140 | BN_init(&m); |
| 141 | BN_init(&xr); |
| 142 | |
| 143 | if (!dsa->p || !dsa->q || !dsa->g) |
| 144 | { |
| 145 | reason=DSA_R_MISSING_PARAMETERS; |
| 146 | goto err; |
| 147 | } |
| 148 | |
| 149 | s=BN_new(); |
| 150 | if (s == NULL) goto err; |
| 151 | ctx=BN_CTX_new(); |
| 152 | if (ctx == NULL) goto err; |
Alexandre Savard | 7541067 | 2012-08-08 09:50:01 -0400 | [diff] [blame] | 153 | |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 154 | if ((dsa->kinv == NULL) || (dsa->r == NULL)) |
| 155 | { |
| 156 | if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; |
| 157 | } |
| 158 | else |
| 159 | { |
| 160 | kinv=dsa->kinv; |
| 161 | dsa->kinv=NULL; |
| 162 | r=dsa->r; |
| 163 | dsa->r=NULL; |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 164 | } |
| 165 | |
| 166 | |
| 167 | if (dlen > BN_num_bytes(dsa->q)) |
| 168 | /* if the digest length is greater than the size of q use the |
| 169 | * BN_num_bits(dsa->q) leftmost bits of the digest, see |
| 170 | * fips 186-3, 4.2 */ |
| 171 | dlen = BN_num_bytes(dsa->q); |
| 172 | if (BN_bin2bn(dgst,dlen,&m) == NULL) |
| 173 | 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 | if (!BN_sub(s,s,dsa->q)) goto err; |
| 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; |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 184 | ret->r = r; |
| 185 | ret->s = s; |
| 186 | |
| 187 | err: |
| 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 | |
| 202 | static 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; |
| 280 | err: |
| 281 | if (!ret) |
| 282 | { |
| 283 | DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); |
| 284 | if (r != NULL) |
| 285 | BN_clear_free(r); |
| 286 | } |
| 287 | if (ctx_in == NULL) BN_CTX_free(ctx); |
| 288 | BN_clear_free(&k); |
| 289 | BN_clear_free(&kq); |
| 290 | return(ret); |
| 291 | } |
| 292 | |
| 293 | static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, |
| 294 | DSA *dsa) |
| 295 | { |
| 296 | BN_CTX *ctx; |
| 297 | BIGNUM u1,u2,t1; |
| 298 | BN_MONT_CTX *mont=NULL; |
| 299 | int ret = -1, i; |
| 300 | if (!dsa->p || !dsa->q || !dsa->g) |
| 301 | { |
| 302 | DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS); |
| 303 | return -1; |
| 304 | } |
| 305 | |
| 306 | i = BN_num_bits(dsa->q); |
| 307 | /* fips 186-3 allows only different sizes for q */ |
| 308 | if (i != 160 && i != 224 && i != 256) |
| 309 | { |
| 310 | DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE); |
| 311 | return -1; |
| 312 | } |
| 313 | |
| 314 | if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) |
| 315 | { |
| 316 | DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE); |
| 317 | return -1; |
| 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 (dgst_len > (i >> 3)) |
| 344 | /* if the digest length is greater than the size of q use the |
| 345 | * BN_num_bits(dsa->q) leftmost bits of the digest, see |
| 346 | * fips 186-3, 4.2 */ |
| 347 | dgst_len = (i >> 3); |
| 348 | if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err; |
| 349 | |
| 350 | /* u1 = M * w mod q */ |
| 351 | if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err; |
| 352 | |
| 353 | /* u2 = r * w mod q */ |
| 354 | if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err; |
| 355 | |
| 356 | |
| 357 | if (dsa->flags & DSA_FLAG_CACHE_MONT_P) |
| 358 | { |
| 359 | mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p, |
| 360 | CRYPTO_LOCK_DSA, dsa->p, ctx); |
| 361 | if (!mont) |
| 362 | goto err; |
| 363 | } |
| 364 | |
| 365 | |
| 366 | DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont); |
| 367 | /* BN_copy(&u1,&t1); */ |
| 368 | /* let u1 = u1 mod q */ |
| 369 | if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err; |
| 370 | |
| 371 | /* V is now in u1. If the signature is correct, it will be |
| 372 | * equal to R. */ |
| 373 | ret=(BN_ucmp(&u1, sig->r) == 0); |
| 374 | |
| 375 | err: |
| 376 | /* XXX: surely this is wrong - if ret is 0, it just didn't verify; |
| 377 | there is no error in BN. Test should be ret == -1 (Ben) */ |
| 378 | if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB); |
| 379 | if (ctx != NULL) BN_CTX_free(ctx); |
| 380 | BN_free(&u1); |
| 381 | BN_free(&u2); |
| 382 | BN_free(&t1); |
| 383 | return(ret); |
| 384 | } |
| 385 | |
| 386 | static int dsa_init(DSA *dsa) |
| 387 | { |
| 388 | dsa->flags|=DSA_FLAG_CACHE_MONT_P; |
| 389 | return(1); |
| 390 | } |
| 391 | |
| 392 | static int dsa_finish(DSA *dsa) |
| 393 | { |
| 394 | if(dsa->method_mont_p) |
| 395 | BN_MONT_CTX_free(dsa->method_mont_p); |
| 396 | return(1); |
| 397 | } |
| 398 | |