crypto/dsa/dsa_vrf.c

   1 /* crypto/dsa/dsa_vrf.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 "bn.h"
  64 #include "dsa.h"
  65 #include "rand.h"
  66 #include "asn1.h"
  67 #include "asn1_mac.h"
  68
  69 int DSA_do_verify(unsigned char *dgst, int dgst_len, DSA_SIG *sig, DSA *dsa)
  70         {
  71         BN_CTX *ctx;
  72         BIGNUM u1,u2,t1;
  73         BN_MONT_CTX *mont=NULL;
  74         int ret = -1;
  75
  76         if ((ctx=BN_CTX_new()) == NULL) goto err;
  77         BN_init(&u1);
  78         BN_init(&u2);
  79         BN_init(&t1);
  80
  81         /* Calculate W = inv(S) mod Q
  82          * save W in u2 */
  83         if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
  84
  85         /* save M in u1 */
  86         if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
  87
  88         /* u1 = M * w mod q */
  89         if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
  90
  91         /* u2 = r * w mod q */
  92         if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
  93
  94         if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
  95                 {
  96                 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
  97                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
  98                                 dsa->p,ctx)) goto err;
  99                 }
 100         mont=(BN_MONT_CTX *)dsa->method_mont_p;
 101
 102 #if 0
 103         {
 104         BIGNUM t2;
 105
 106         BN_init(&t2);
 107         /* v = ( g^u1 * y^u2 mod p ) mod q */
 108         /* let t1 = g ^ u1 mod p */
 109         if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err;
 110         /* let t2 = y ^ u2 mod p */
 111         if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err;
 112         /* let u1 = t1 * t2 mod p */
 113         if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn;
 114         BN_free(&t2);
 115         }
 116         /* let u1 = u1 mod q */
 117         if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err;
 118 #else
 119         {
 120         if (!BN_mod_exp2_mont(&t1,dsa->g,&u1,dsa->pub_key,&u2,dsa->p,ctx,mont))
 121                 goto err;
 122         /* BN_copy(&u1,&t1); */
 123         /* let u1 = u1 mod q */
 124         if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
 125         }
 126 #endif
 127         /* V is now in u1.  If the signature is correct, it will be
 128          * equal to R. */
 129         ret=(BN_ucmp(&u1, sig->r) == 0);
 130
 131         err:
 132         if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
 133         if (ctx != NULL) BN_CTX_free(ctx);
 134         BN_free(&u1);
 135         BN_free(&u2);
 136         BN_free(&t1);
 137         return(ret);
 138         }
 139
 140 /* data has already been hashed (probably with SHA or SHA-1). */
 141 /* returns
 142  *      1: correct signature
 143  *      0: incorrect signature
 144  *     -1: error
 145  */
 146 int DSA_verify(int type, unsigned char *dgst, int dgst_len,
 147              unsigned char *sigbuf, int siglen, DSA *dsa)
 148         {
 149         DSA_SIG *s;
 150         int ret=-1;
 151
 152         s = DSA_SIG_new();
 153         if (s == NULL) return(ret);
 154         if (d2i_DSA_SIG(&s,&sigbuf,siglen) == NULL) goto err;
 155         ret=DSA_do_verify(dgst,dgst_len,s,dsa);
 156 err:
 157         DSA_SIG_free(s);
 158         return(ret);
 159         }