crypto/dsa/dsa_vrf.c

   1 /* crypto/dsa/dsa_vrf.c */
   2 /* Copyright (C) 1995-1997 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 /* Origional 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 /* data has already been hashed (probably with SHA or SHA-1). */
  70 /* returns
  71  *       1: correct signature
  72  *       0: incorrect signature
  73  *      -1: error
  74  */
  75 int DSA_verify(type,dgst,dgst_len,sigbuf,siglen, dsa)
  76 int type;
  77 unsigned char *dgst;
  78 int dgst_len;
  79 unsigned char *sigbuf;
  80 int siglen;
  81 DSA *dsa;
  82         {
  83         /* The next 3 are used by the M_ASN1 macros */
  84         long length=siglen;
  85         ASN1_CTX c;
  86         unsigned char **pp= &sigbuf;
  87         BN_CTX *ctx;
  88         BIGNUM *r=NULL;
  89         BIGNUM *t1=NULL,*t2=NULL;
  90         BIGNUM *u1=NULL,*u2=NULL;
  91         ASN1_INTEGER *bs=NULL;
  92         int ret = -1;
  93
  94         ctx=BN_CTX_new();
  95         if (ctx == NULL) goto err;
  96
  97         t1=BN_new();
  98         t2=BN_new();
  99         if (t1 == NULL || t2 == NULL) goto err;
 100
 101         M_ASN1_D2I_Init();
 102         M_ASN1_D2I_start_sequence();
 103         M_ASN1_D2I_get(bs,d2i_ASN1_INTEGER);
 104         if ((r=BN_bin2bn(bs->data,bs->length,NULL)) == NULL) goto err_bn;
 105         M_ASN1_D2I_get(bs,d2i_ASN1_INTEGER);
 106         if ((u1=BN_bin2bn(bs->data,bs->length,NULL)) == NULL) goto err_bn;
 107         if (!asn1_Finish(&c)) goto err;
 108
 109         /* Calculate W = inv(S) mod Q
 110          * save W in u2 */
 111         if ((u2=BN_mod_inverse(u1,dsa->q,ctx)) == NULL) goto err_bn;
 112
 113         /* save M in u1 */
 114         if (BN_bin2bn(dgst,dgst_len,u1) == NULL) goto err_bn;
 115
 116         /* u1 = M * w mod q */
 117         if (!BN_mod_mul(u1,u1,u2,dsa->q,ctx)) goto err_bn;
 118
 119         /* u2 = r * w mod q */
 120         if (!BN_mod_mul(u2,r,u2,dsa->q,ctx)) goto err_bn;
 121
 122         /* v = ( g^u1 * y^u2 mod p ) mod q */
 123         /* let t1 = g ^ u1 mod p */
 124         if (!BN_mod_exp(t1,dsa->g,u1,dsa->p,ctx)) goto err_bn;
 125         /* let t2 = y ^ u2 mod p */
 126         if (!BN_mod_exp(t2,dsa->pub_key,u2,dsa->p,ctx)) goto err_bn;
 127         /* let u1 = t1 * t2 mod p */
 128         if (!BN_mod_mul(u1,t1,t2,dsa->p,ctx)) goto err_bn;
 129         /* let u1 = u1 mod q */
 130         if (!BN_mod(u1,u1,dsa->q,ctx)) goto err_bn;
 131         /* V is now in u1.  If the signature is correct, it will be
 132          * equal to R. */
 133         ret=(BN_ucmp(u1, r) == 0);
 134         if (0)
 135                 {
 136 err: /* ASN1 error */
 137                 DSAerr(DSA_F_DSA_VERIFY,c.error);
 138                 }
 139         if (0)
 140                 {
 141 err_bn: /* BN error */
 142                 DSAerr(DSA_F_DSA_VERIFY,ERR_R_BN_LIB);
 143                 }
 144         if (ctx != NULL) BN_CTX_free(ctx);
 145         if (r != NULL) BN_free(r);
 146         if (t1 != NULL) BN_free(t1);
 147         if (t2 != NULL) BN_free(t2);
 148         if (u1 != NULL) BN_free(u1);
 149         if (u2 != NULL) BN_free(u2);
 150         if (bs != NULL) ASN1_BIT_STRING_free(bs);
 151         return(ret);
 152         }