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/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
  75 static DSA_METHOD openssl_dsa_meth = {
  76 "OpenSSL DSA method",
  77 dsa_do_sign,
  78 dsa_sign_setup,
  79 dsa_do_verify,
  80 NULL, /* dsa_mod_exp, */
  81 NULL, /* dsa_bn_mod_exp, */
  82 dsa_init,
  83 dsa_finish,
  84 0,
  85 NULL,
  86 NULL,
  87 NULL
  88 };
  89
  90 /* These macro wrappers replace attempts to use the dsa_mod_exp() and
  91  * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
  92  * having a the macro work as an expression by bundling an "err_instr". So;
  93  *
  94  *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
  95  *                 dsa->method_mont_p)) goto err;
  96  *
  97  * can be replaced by;
  98  *
  99  *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
 100  *                 dsa->method_mont_p);
 101  */
 102
 103 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
 104         do { \
 105         int _tmp_res53; \
 106         if((dsa)->meth->dsa_mod_exp) \
 107                 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
 108                                 (a2), (p2), (m), (ctx), (in_mont)); \
 109         else \
 110                 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
 111                                 (m), (ctx), (in_mont)); \
 112         if(!_tmp_res53) err_instr; \
 113         } while(0)
 114 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
 115         do { \
 116         int _tmp_res53; \
 117         if((dsa)->meth->bn_mod_exp) \
 118                 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
 119                                 (m), (ctx), (m_ctx)); \
 120         else \
 121                 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
 122         if(!_tmp_res53) err_instr; \
 123         } while(0)
 124
 125 const DSA_METHOD *DSA_OpenSSL(void)
 126 {
 127         return &openssl_dsa_meth;
 128 }
 129
 130 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 131         {
 132         BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
 133         BIGNUM m;
 134         BIGNUM xr;
 135         BN_CTX *ctx=NULL;
 136         int i,reason=ERR_R_BN_LIB;
 137         DSA_SIG *ret=NULL;
 138
 139         BN_init(&m);
 140         BN_init(&xr);
 141
 142         if (!dsa->p || !dsa->q || !dsa->g)
 143                 {
 144                 reason=DSA_R_MISSING_PARAMETERS;
 145                 goto err;
 146                 }
 147
 148         s=BN_new();
 149         if (s == NULL) goto err;
 150
 151         i=BN_num_bytes(dsa->q); /* should be 20 */
 152         if ((dlen > i) || (dlen > 50))
 153                 {
 154                 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
 155                 goto err;
 156                 }
 157
 158         ctx=BN_CTX_new();
 159         if (ctx == NULL) goto err;
 160
 161         if ((dsa->kinv == NULL) || (dsa->r == NULL))
 162                 {
 163                 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
 164                 }
 165         else
 166                 {
 167                 kinv=dsa->kinv;
 168                 dsa->kinv=NULL;
 169                 r=dsa->r;
 170                 dsa->r=NULL;
 171                 }
 172
 173         if (BN_bin2bn(dgst,dlen,&m) == NULL) 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                 BN_sub(s,s,dsa->q);
 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;
 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_EXP_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;
 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         if (BN_num_bits(dsa->q) != 160)
 307                 {
 308                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
 309                 return -1;
 310                 }
 311
 312         if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
 313                 {
 314                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
 315                 return -1;
 316                 }
 317
 318         BN_init(&u1);
 319         BN_init(&u2);
 320         BN_init(&t1);
 321
 322         if ((ctx=BN_CTX_new()) == NULL) goto err;
 323
 324         if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 325             BN_ucmp(sig->r, dsa->q) >= 0)
 326                 {
 327                 ret = 0;
 328                 goto err;
 329                 }
 330         if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 331             BN_ucmp(sig->s, dsa->q) >= 0)
 332                 {
 333                 ret = 0;
 334                 goto err;
 335                 }
 336
 337         /* Calculate W = inv(S) mod Q
 338          * save W in u2 */
 339         if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
 340
 341         /* save M in u1 */
 342         if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
 343
 344         /* u1 = M * w mod q */
 345         if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
 346
 347         /* u2 = r * w mod q */
 348         if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
 349
 350
 351         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 352                 {
 353                 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 354                                         CRYPTO_LOCK_DSA, dsa->p, ctx);
 355                 if (!mont)
 356                         goto err;
 357                 }
 358
 359
 360         DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
 361         /* BN_copy(&u1,&t1); */
 362         /* let u1 = u1 mod q */
 363         if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
 364
 365         /* V is now in u1.  If the signature is correct, it will be
 366          * equal to R. */
 367         ret=(BN_ucmp(&u1, sig->r) == 0);
 368
 369         err:
 370         /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
 371            there is no error in BN. Test should be ret == -1 (Ben) */
 372         if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
 373         if (ctx != NULL) BN_CTX_free(ctx);
 374         BN_free(&u1);
 375         BN_free(&u2);
 376         BN_free(&t1);
 377         return(ret);
 378         }
 379
 380 static int dsa_init(DSA *dsa)
 381 {
 382         dsa->flags|=DSA_FLAG_CACHE_MONT_P;
 383         return(1);
 384 }
 385
 386 static int dsa_finish(DSA *dsa)
 387 {
 388         if(dsa->method_mont_p)
 389                 BN_MONT_CTX_free(dsa->method_mont_p);
 390         return(1);
 391 }
 392