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 #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 i, reason=ERR_R_BN_LIB;
 138         DSA_SIG *ret=NULL;
 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
 152         /* reject a excessive digest length (currently at most
 153          * dsa-with-SHA256 is supported) */
 154         if (dlen > SHA256_DIGEST_LENGTH)
 155                 {
 156                 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
 157                 goto err;
 158                 }
 159
 160         ctx=BN_CTX_new();
 161         if (ctx == NULL) goto err;
 162
 163         if ((dsa->kinv == NULL) || (dsa->r == NULL))
 164                 {
 165                 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
 166                 }
 167         else
 168                 {
 169                 kinv=dsa->kinv;
 170                 dsa->kinv=NULL;
 171                 r=dsa->r;
 172                 dsa->r=NULL;
 173                 }
 174
 175         if (BN_bin2bn(dgst,dlen,&m) == NULL)
 176                 goto err;
 177         i = BN_num_bytes(dsa->q);
 178         if (dlen > i)
 179                 {
 180                 /* if the digest length is greater than the size of q use the
 181                  * BN_num_bits(dsa->q) leftmost bits of the digest, see
 182                  * fips 186-3, 4.2 */
 183                 if (!BN_rshift(&m, &m, (dlen - i) << 3))
 184                         goto err;
 185                 }
 186
 187         /* Compute  s = inv(k) (m + xr) mod q */
 188         if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
 189         if (!BN_add(s, &xr, &m)) goto err;              /* s = m + xr */
 190         if (BN_cmp(s,dsa->q) > 0)
 191                 BN_sub(s,s,dsa->q);
 192         if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
 193
 194         ret=DSA_SIG_new();
 195         if (ret == NULL) goto err;
 196         ret->r = r;
 197         ret->s = s;
 198
 199 err:
 200         if (!ret)
 201                 {
 202                 DSAerr(DSA_F_DSA_DO_SIGN,reason);
 203                 BN_free(r);
 204                 BN_free(s);
 205                 }
 206         if (ctx != NULL) BN_CTX_free(ctx);
 207         BN_clear_free(&m);
 208         BN_clear_free(&xr);
 209         if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
 210             BN_clear_free(kinv);
 211         return(ret);
 212         }
 213
 214 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
 215         {
 216         BN_CTX *ctx;
 217         BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
 218         int ret=0;
 219
 220         if (!dsa->p || !dsa->q || !dsa->g)
 221                 {
 222                 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
 223                 return 0;
 224                 }
 225
 226         BN_init(&k);
 227         BN_init(&kq);
 228
 229         if (ctx_in == NULL)
 230                 {
 231                 if ((ctx=BN_CTX_new()) == NULL) goto err;
 232                 }
 233         else
 234                 ctx=ctx_in;
 235
 236         if ((r=BN_new()) == NULL) goto err;
 237
 238         /* Get random k */
 239         do
 240                 if (!BN_rand_range(&k, dsa->q)) goto err;
 241         while (BN_is_zero(&k));
 242         if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
 243                 {
 244                 BN_set_flags(&k, BN_FLG_EXP_CONSTTIME);
 245                 }
 246
 247         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 248                 {
 249                 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 250                                                 CRYPTO_LOCK_DSA,
 251                                                 dsa->p, ctx))
 252                         goto err;
 253                 }
 254
 255         /* Compute r = (g^k mod p) mod q */
 256
 257         if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
 258                 {
 259                 if (!BN_copy(&kq, &k)) goto err;
 260
 261                 /* We do not want timing information to leak the length of k,
 262                  * so we compute g^k using an equivalent exponent of fixed length.
 263                  *
 264                  * (This is a kludge that we need because the BN_mod_exp_mont()
 265                  * does not let us specify the desired timing behaviour.) */
 266
 267                 if (!BN_add(&kq, &kq, dsa->q)) goto err;
 268                 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
 269                         {
 270                         if (!BN_add(&kq, &kq, dsa->q)) goto err;
 271                         }
 272
 273                 K = &kq;
 274                 }
 275         else
 276                 {
 277                 K = &k;
 278                 }
 279         DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
 280                         dsa->method_mont_p);
 281         if (!BN_mod(r,r,dsa->q,ctx)) goto err;
 282
 283         /* Compute  part of 's = inv(k) (m + xr) mod q' */
 284         if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
 285
 286         if (*kinvp != NULL) BN_clear_free(*kinvp);
 287         *kinvp=kinv;
 288         kinv=NULL;
 289         if (*rp != NULL) BN_clear_free(*rp);
 290         *rp=r;
 291         ret=1;
 292 err:
 293         if (!ret)
 294                 {
 295                 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
 296                 if (r != NULL)
 297                         BN_clear_free(r);
 298                 }
 299         if (ctx_in == NULL) BN_CTX_free(ctx);
 300         BN_clear_free(&k);
 301         BN_clear_free(&kq);
 302         return(ret);
 303         }
 304
 305 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
 306                          DSA *dsa)
 307         {
 308         BN_CTX *ctx;
 309         BIGNUM u1,u2,t1;
 310         BN_MONT_CTX *mont=NULL;
 311         int ret = -1, i, j;
 312         if (!dsa->p || !dsa->q || !dsa->g)
 313                 {
 314                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
 315                 return -1;
 316                 }
 317
 318         i = BN_num_bits(dsa->q);
 319         /* fips 186-3 allows only different sizes for q */
 320         if (i != 160 && i != 224 && i != 256)
 321                 {
 322                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
 323                 return -1;
 324                 }
 325
 326         if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
 327                 {
 328                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
 329                 return -1;
 330                 }
 331
 332         /* reject a excessive digest length (currently at most
 333          * dsa-with-SHA256 is supported) */
 334         if (dgst_len > SHA256_DIGEST_LENGTH)
 335                 {
 336                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
 337                 return -1;
 338                 }
 339
 340         BN_init(&u1);
 341         BN_init(&u2);
 342         BN_init(&t1);
 343
 344         if ((ctx=BN_CTX_new()) == NULL) goto err;
 345
 346         if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 347             BN_ucmp(sig->r, dsa->q) >= 0)
 348                 {
 349                 ret = 0;
 350                 goto err;
 351                 }
 352         if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 353             BN_ucmp(sig->s, dsa->q) >= 0)
 354                 {
 355                 ret = 0;
 356                 goto err;
 357                 }
 358
 359         /* Calculate W = inv(S) mod Q
 360          * save W in u2 */
 361         if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
 362
 363         /* save M in u1 */
 364         if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
 365         j = dgst_len << 3;
 366         if (j > i)
 367                 {
 368                 /* if the digest length is greater than the size of q use the
 369                  * BN_num_bits(dsa->q) leftmost bits of the digest, see
 370                  * fips 186-3, 4.2 */
 371                 if (!BN_rshift(&u1, &u1, j - i))
 372                         goto err;
 373                 }
 374
 375         /* u1 = M * w mod q */
 376         if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
 377
 378         /* u2 = r * w mod q */
 379         if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
 380
 381
 382         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 383                 {
 384                 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 385                                         CRYPTO_LOCK_DSA, dsa->p, ctx);
 386                 if (!mont)
 387                         goto err;
 388                 }
 389
 390
 391         DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
 392         /* BN_copy(&u1,&t1); */
 393         /* let u1 = u1 mod q */
 394         if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
 395
 396         /* V is now in u1.  If the signature is correct, it will be
 397          * equal to R. */
 398         ret=(BN_ucmp(&u1, sig->r) == 0);
 399
 400         err:
 401         /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
 402            there is no error in BN. Test should be ret == -1 (Ben) */
 403         if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
 404         if (ctx != NULL) BN_CTX_free(ctx);
 405         BN_free(&u1);
 406         BN_free(&u2);
 407         BN_free(&t1);
 408         return(ret);
 409         }
 410
 411 static int dsa_init(DSA *dsa)
 412 {
 413         dsa->flags|=DSA_FLAG_CACHE_MONT_P;
 414         return(1);
 415 }
 416
 417 static int dsa_finish(DSA *dsa)
 418 {
 419         if(dsa->method_mont_p)
 420                 BN_MONT_CTX_free(dsa->method_mont_p);
 421         return(1);
 422 }
 423