/* crypto/dsa/dsa_vrf.c */
/* Copyright (C) 1995-1997 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
/* Origional version from Steven Schoch */
#include
#include "cryptlib.h"
#include "bn.h"
#include "dsa.h"
#include "rand.h"
#include "asn1.h"
#include "asn1_mac.h"
/* data has already been hashed (probably with SHA or SHA-1). */
/* returns
* 1: correct signature
* 0: incorrect signature
* -1: error
*/
int DSA_verify(type,dgst,dgst_len,sigbuf,siglen, dsa)
int type;
unsigned char *dgst;
int dgst_len;
unsigned char *sigbuf;
int siglen;
DSA *dsa;
{
/* The next 3 are used by the M_ASN1 macros */
long length=siglen;
ASN1_CTX c;
unsigned char **pp= &sigbuf;
BN_CTX *ctx;
BIGNUM *r=NULL;
BIGNUM *t1=NULL,*t2=NULL;
BIGNUM *u1=NULL,*u2=NULL;
ASN1_INTEGER *bs=NULL;
int ret = -1;
ctx=BN_CTX_new();
if (ctx == NULL) goto err;
t1=BN_new();
t2=BN_new();
if (t1 == NULL || t2 == NULL) goto err;
M_ASN1_D2I_Init();
M_ASN1_D2I_start_sequence();
M_ASN1_D2I_get(bs,d2i_ASN1_INTEGER);
if ((r=BN_bin2bn(bs->data,bs->length,NULL)) == NULL) goto err_bn;
M_ASN1_D2I_get(bs,d2i_ASN1_INTEGER);
if ((u1=BN_bin2bn(bs->data,bs->length,NULL)) == NULL) goto err_bn;
if (!asn1_Finish(&c)) goto err;
/* Calculate W = inv(S) mod Q
* save W in u2 */
if ((u2=BN_mod_inverse(u1,dsa->q,ctx)) == NULL) goto err_bn;
/* save M in u1 */
if (BN_bin2bn(dgst,dgst_len,u1) == NULL) goto err_bn;
/* u1 = M * w mod q */
if (!BN_mod_mul(u1,u1,u2,dsa->q,ctx)) goto err_bn;
/* u2 = r * w mod q */
if (!BN_mod_mul(u2,r,u2,dsa->q,ctx)) goto err_bn;
/* v = ( g^u1 * y^u2 mod p ) mod q */
/* let t1 = g ^ u1 mod p */
if (!BN_mod_exp(t1,dsa->g,u1,dsa->p,ctx)) goto err_bn;
/* let t2 = y ^ u2 mod p */
if (!BN_mod_exp(t2,dsa->pub_key,u2,dsa->p,ctx)) goto err_bn;
/* let u1 = t1 * t2 mod p */
if (!BN_mod_mul(u1,t1,t2,dsa->p,ctx)) goto err_bn;
/* let u1 = u1 mod q */
if (!BN_mod(u1,u1,dsa->q,ctx)) goto err_bn;
/* V is now in u1. If the signature is correct, it will be
* equal to R. */
ret=(BN_ucmp(u1, r) == 0);
if (0)
{
err: /* ASN1 error */
DSAerr(DSA_F_DSA_VERIFY,c.error);
}
if (0)
{
err_bn: /* BN error */
DSAerr(DSA_F_DSA_VERIFY,ERR_R_BN_LIB);
}
if (ctx != NULL) BN_CTX_free(ctx);
if (r != NULL) BN_free(r);
if (t1 != NULL) BN_free(t1);
if (t2 != NULL) BN_free(t2);
if (u1 != NULL) BN_free(u1);
if (u2 != NULL) BN_free(u2);
if (bs != NULL) ASN1_BIT_STRING_free(bs);
return(ret);
}