crypto/dsa/dsa_ossl.c

   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 #define OPENSSL_FIPSAPI
  62
  63 #include <stdio.h>
  64 #include "cryptlib.h"
  65 #include <openssl/bn.h>
  66 #include <openssl/sha.h>
  67 #include <openssl/dsa.h>
  68 #include <openssl/rand.h>
  69 #include <openssl/asn1.h>
  70 #ifdef OPENSSL_FIPS
  71 #include <openssl/fips.h>
  72 #endif
  73
  74 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
  75 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
  76 static int dsa_sign_setup_with_digest(DSA *dsa, BN_CTX *ctx_in,
  77                                       BIGNUM **kinvp, BIGNUM **rp,
  78                                       const unsigned char *dgst, int dlen);
  79 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
  80                          DSA *dsa);
  81 static int dsa_init(DSA *dsa);
  82 static int dsa_finish(DSA *dsa);
  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 NULL, /* dsa_mod_exp, */
  90 NULL, /* dsa_bn_mod_exp, */
  91 dsa_init,
  92 dsa_finish,
  93 DSA_FLAG_FIPS_METHOD,
  94 NULL,
  95 NULL,
  96 NULL
  97 };
  98
  99 /* These macro wrappers replace attempts to use the dsa_mod_exp() and
 100  * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
 101  * having a the macro work as an expression by bundling an "err_instr". So;
 102  *
 103  *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
 104  *                 dsa->method_mont_p)) goto err;
 105  *
 106  * can be replaced by;
 107  *
 108  *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
 109  *                 dsa->method_mont_p);
 110  */
 111
 112 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
 113         do { \
 114         int _tmp_res53; \
 115         if((dsa)->meth->dsa_mod_exp) \
 116                 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
 117                                 (a2), (p2), (m), (ctx), (in_mont)); \
 118         else \
 119                 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
 120                                 (m), (ctx), (in_mont)); \
 121         if(!_tmp_res53) err_instr; \
 122         } while(0)
 123 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
 124         do { \
 125         int _tmp_res53; \
 126         if((dsa)->meth->bn_mod_exp) \
 127                 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
 128                                 (m), (ctx), (m_ctx)); \
 129         else \
 130                 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
 131         if(!_tmp_res53) err_instr; \
 132         } while(0)
 133
 134 const DSA_METHOD *DSA_OpenSSL(void)
 135 {
 136         return &openssl_dsa_meth;
 137 }
 138
 139 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 140         {
 141         BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
 142         BIGNUM m;
 143         BIGNUM xr;
 144         BN_CTX *ctx=NULL;
 145         int reason=ERR_R_BN_LIB;
 146         DSA_SIG *ret=NULL;
 147         int noredo = 0;
 148
 149 #ifdef OPENSSL_FIPS
 150         if(FIPS_selftest_failed())
 151             {
 152             FIPSerr(FIPS_F_DSA_DO_SIGN,FIPS_R_FIPS_SELFTEST_FAILED);
 153             return NULL;
 154             }
 155
 156         if (FIPS_module_mode() && !(dsa->flags & DSA_FLAG_NON_FIPS_ALLOW)
 157                 && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
 158                 {
 159                 DSAerr(DSA_F_DSA_DO_SIGN, DSA_R_KEY_SIZE_TOO_SMALL);
 160                 return NULL;
 161                 }
 162         if (!fips_check_dsa_prng(dsa, 0, 0))
 163                 goto err;
 164 #endif
 165
 166         BN_init(&m);
 167         BN_init(&xr);
 168
 169         if (!dsa->p || !dsa->q || !dsa->g)
 170                 {
 171                 reason=DSA_R_MISSING_PARAMETERS;
 172                 goto err;
 173                 }
 174
 175         s=BN_new();
 176         if (s == NULL) goto err;
 177         ctx=BN_CTX_new();
 178         if (ctx == NULL) goto err;
 179 redo:
 180         if ((dsa->kinv == NULL) || (dsa->r == NULL))
 181                 {
 182                 if (!dsa_sign_setup_with_digest(dsa,ctx,&kinv,&r,dgst,dlen))
 183                         goto err;
 184                 }
 185         else
 186                 {
 187                 kinv=dsa->kinv;
 188                 dsa->kinv=NULL;
 189                 r=dsa->r;
 190                 dsa->r=NULL;
 191                 noredo = 1;
 192                 }
 193
 194
 195         if (dlen > BN_num_bytes(dsa->q))
 196                 /* if the digest length is greater than the size of q use the
 197                  * BN_num_bits(dsa->q) leftmost bits of the digest, see
 198                  * fips 186-3, 4.2 */
 199                 dlen = BN_num_bytes(dsa->q);
 200         if (BN_bin2bn(dgst,dlen,&m) == NULL)
 201                 goto err;
 202
 203         /* Compute  s = inv(k) (m + xr) mod q */
 204         if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
 205         if (!BN_add(s, &xr, &m)) goto err;              /* s = m + xr */
 206         if (BN_cmp(s,dsa->q) > 0)
 207                 if (!BN_sub(s,s,dsa->q)) goto err;
 208         if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
 209
 210         ret=DSA_SIG_new();
 211         if (ret == NULL) goto err;
 212         /* Redo if r or s is zero as required by FIPS 186-3: this is
 213          * very unlikely.
 214          */
 215         if (BN_is_zero(r) || BN_is_zero(s))
 216                 {
 217                 if (noredo)
 218                         {
 219                         reason = DSA_R_NEED_NEW_SETUP_VALUES;
 220                         goto err;
 221                         }
 222                 goto redo;
 223                 }
 224         ret->r = r;
 225         ret->s = s;
 226
 227 err:
 228         if (!ret)
 229                 {
 230                 DSAerr(DSA_F_DSA_DO_SIGN,reason);
 231                 BN_free(r);
 232                 BN_free(s);
 233                 }
 234         if (ctx != NULL) BN_CTX_free(ctx);
 235         BN_clear_free(&m);
 236         BN_clear_free(&xr);
 237         if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
 238             BN_clear_free(kinv);
 239         return(ret);
 240         }
 241
 242 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
 243                           BIGNUM **kinvp, BIGNUM **rp) {
 244         return dsa_sign_setup_with_digest(dsa, ctx_in, kinvp, rp, NULL, 0);
 245 }
 246
 247 static int dsa_sign_setup_with_digest(DSA *dsa, BN_CTX *ctx_in,
 248                                       BIGNUM **kinvp, BIGNUM **rp,
 249                                       const unsigned char *dgst, int dlen)
 250         {
 251         BN_CTX *ctx;
 252         BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
 253         int ret=0;
 254
 255         if (!dsa->p || !dsa->q || !dsa->g)
 256                 {
 257                 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
 258                 return 0;
 259                 }
 260
 261         BN_init(&k);
 262         BN_init(&kq);
 263
 264         if (ctx_in == NULL)
 265                 {
 266                 if ((ctx=BN_CTX_new()) == NULL) goto err;
 267                 }
 268         else
 269                 ctx=ctx_in;
 270
 271         if ((r=BN_new()) == NULL) goto err;
 272
 273         /* Get random k */
 274         do
 275                 {
 276 #ifndef OPENSSL_NO_SHA512
 277                 if (dgst != NULL)
 278                         {
 279                         /* We calculate k from SHA512(private_key + H(message)
 280                          * + random). This protects the private key from a weak
 281                          * PRNG. */
 282                         if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst,
 283                                                    dlen, ctx))
 284                                 goto err;
 285                         }
 286                 else
 287 #endif
 288                         if (!BN_rand_range(&k, dsa->q)) goto err;
 289                 } while (BN_is_zero(&k));
 290
 291         if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
 292                 {
 293                 BN_set_flags(&k, BN_FLG_CONSTTIME);
 294                 }
 295
 296         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 297                 {
 298                 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 299                                                 CRYPTO_LOCK_DSA,
 300                                                 dsa->p, ctx))
 301                         goto err;
 302                 }
 303
 304         /* Compute r = (g^k mod p) mod q */
 305
 306         if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
 307                 {
 308                 if (!BN_copy(&kq, &k)) goto err;
 309
 310                 /* We do not want timing information to leak the length of k,
 311                  * so we compute g^k using an equivalent exponent of fixed length.
 312                  *
 313                  * (This is a kludge that we need because the BN_mod_exp_mont()
 314                  * does not let us specify the desired timing behaviour.) */
 315
 316                 if (!BN_add(&kq, &kq, dsa->q)) goto err;
 317                 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
 318                         {
 319                         if (!BN_add(&kq, &kq, dsa->q)) goto err;
 320                         }
 321
 322                 K = &kq;
 323                 }
 324         else
 325                 {
 326                 K = &k;
 327                 }
 328         DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
 329                         dsa->method_mont_p);
 330         if (!BN_mod(r,r,dsa->q,ctx)) goto err;
 331
 332         /* Compute  part of 's = inv(k) (m + xr) mod q' */
 333         if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
 334
 335         if (*kinvp != NULL) BN_clear_free(*kinvp);
 336         *kinvp=kinv;
 337         kinv=NULL;
 338         if (*rp != NULL) BN_clear_free(*rp);
 339         *rp=r;
 340         ret=1;
 341 err:
 342         if (!ret)
 343                 {
 344                 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
 345                 if (r != NULL)
 346                         BN_clear_free(r);
 347                 }
 348         if (ctx_in == NULL) BN_CTX_free(ctx);
 349         BN_clear_free(&k);
 350         BN_clear_free(&kq);
 351         return(ret);
 352         }
 353
 354 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
 355                          DSA *dsa)
 356         {
 357         BN_CTX *ctx;
 358         BIGNUM u1,u2,t1;
 359         BN_MONT_CTX *mont=NULL;
 360         int ret = -1, i;
 361         if (!dsa->p || !dsa->q || !dsa->g)
 362                 {
 363                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
 364                 return -1;
 365                 }
 366
 367         i = BN_num_bits(dsa->q);
 368         /* fips 186-3 allows only different sizes for q */
 369         if (i != 160 && i != 224 && i != 256)
 370                 {
 371                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
 372                 return -1;
 373                 }
 374
 375 #ifdef OPENSSL_FIPS
 376         if(FIPS_selftest_failed())
 377             {
 378             FIPSerr(FIPS_F_DSA_DO_VERIFY,FIPS_R_FIPS_SELFTEST_FAILED);
 379             return -1;
 380             }
 381
 382         if (FIPS_module_mode() && !(dsa->flags & DSA_FLAG_NON_FIPS_ALLOW)
 383                 && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
 384                 {
 385                 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_KEY_SIZE_TOO_SMALL);
 386                 return -1;
 387                 }
 388 #endif
 389
 390         if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
 391                 {
 392                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
 393                 return -1;
 394                 }
 395         BN_init(&u1);
 396         BN_init(&u2);
 397         BN_init(&t1);
 398
 399         if ((ctx=BN_CTX_new()) == NULL) goto err;
 400
 401         if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 402             BN_ucmp(sig->r, dsa->q) >= 0)
 403                 {
 404                 ret = 0;
 405                 goto err;
 406                 }
 407         if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 408             BN_ucmp(sig->s, dsa->q) >= 0)
 409                 {
 410                 ret = 0;
 411                 goto err;
 412                 }
 413
 414         /* Calculate W = inv(S) mod Q
 415          * save W in u2 */
 416         if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
 417
 418         /* save M in u1 */
 419         if (dgst_len > (i >> 3))
 420                 /* if the digest length is greater than the size of q use the
 421                  * BN_num_bits(dsa->q) leftmost bits of the digest, see
 422                  * fips 186-3, 4.2 */
 423                 dgst_len = (i >> 3);
 424         if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
 425
 426         /* u1 = M * w mod q */
 427         if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
 428
 429         /* u2 = r * w mod q */
 430         if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
 431
 432
 433         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 434                 {
 435                 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 436                                         CRYPTO_LOCK_DSA, dsa->p, ctx);
 437                 if (!mont)
 438                         goto err;
 439                 }
 440
 441
 442         DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
 443         /* BN_copy(&u1,&t1); */
 444         /* let u1 = u1 mod q */
 445         if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
 446
 447         /* V is now in u1.  If the signature is correct, it will be
 448          * equal to R. */
 449         ret=(BN_ucmp(&u1, sig->r) == 0);
 450
 451         err:
 452         /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
 453            there is no error in BN. Test should be ret == -1 (Ben) */
 454         if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
 455         if (ctx != NULL) BN_CTX_free(ctx);
 456         BN_free(&u1);
 457         BN_free(&u2);
 458         BN_free(&t1);
 459         return(ret);
 460         }
 461
 462 static int dsa_init(DSA *dsa)
 463 {
 464         dsa->flags|=DSA_FLAG_CACHE_MONT_P;
 465         return(1);
 466 }
 467
 468 static int dsa_finish(DSA *dsa)
 469 {
 470         if(dsa->method_mont_p)
 471                 BN_MONT_CTX_free(dsa->method_mont_p);
 472         return(1);
 473 }
 474