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/**********************************************************************
* gost_sign.c *
* Copyright (c) 2005-2006 Cryptocom LTD *
* This file is distributed under the same license as OpenSSL *
* *
* Implementation of GOST R 34.10-94 signature algorithm *
* for OpenSSL *
* Requires OpenSSL 0.9.9 for compilation *
**********************************************************************/
#include <string.h>
#include <openssl/rand.h>
#include <openssl/bn.h>
#include <openssl/dsa.h>
#include <openssl/evp.h>
#include "gost_params.h"
#include "gost_lcl.h"
#include "e_gost_err.h"
#ifdef DEBUG_SIGN
void dump_signature(const char *message,const unsigned char *buffer,size_t len)
{
size_t i;
fprintf(stderr,"signature %s Length=%d",message,len);
for (i=0; i<len; i++)
{
if (i% 16 ==0) fputc('\n',stderr);
fprintf (stderr," %02x",buffer[i]);
}
fprintf(stderr,"\nEnd of signature\n");
}
void dump_dsa_sig(const char *message, DSA_SIG *sig)
{
fprintf(stderr,"%s\nR=",message);
BN_print_fp(stderr,sig->r);
fprintf(stderr,"\nS=");
BN_print_fp(stderr,sig->s);
fprintf(stderr,"\n");
}
#else
#define dump_signature(a,b,c)
#define dump_dsa_sig(a,b)
#endif
/*
* Computes signature and returns it as DSA_SIG structure
*/
DSA_SIG *gost_do_sign(const unsigned char *dgst,int dlen, DSA *dsa)
{
BIGNUM *k=NULL,*tmp=NULL,*tmp2=NULL;
DSA_SIG *newsig = DSA_SIG_new();
BIGNUM *md = hashsum2bn(dgst);
/* check if H(M) mod q is zero */
BN_CTX *ctx=BN_CTX_new();
BN_CTX_start(ctx);
if (!newsig)
{
GOSTerr(GOST_F_GOST_DO_SIGN,GOST_R_NO_MEMORY);
goto err;
}
tmp=BN_CTX_get(ctx);
k = BN_CTX_get(ctx);
tmp2 = BN_CTX_get(ctx);
BN_mod(tmp,md,dsa->q,ctx);
if (BN_is_zero(tmp))
{
BN_one(md);
}
do
{
do
{
/*Generate random number k less than q*/
BN_rand_range(k,dsa->q);
/* generate r = (a^x mod p) mod q */
BN_mod_exp(tmp,dsa->g, k, dsa->p,ctx);
if (!(newsig->r)) newsig->r=BN_new();
BN_mod(newsig->r,tmp,dsa->q,ctx);
}
while (BN_is_zero(newsig->r));
/* generate s = (xr + k(Hm)) mod q */
BN_mod_mul(tmp,dsa->priv_key,newsig->r,dsa->q,ctx);
BN_mod_mul(tmp2,k,md,dsa->q,ctx);
if (!newsig->s) newsig->s=BN_new();
BN_mod_add(newsig->s,tmp,tmp2,dsa->q,ctx);
}
while (BN_is_zero(newsig->s));
err:
BN_free(md);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return newsig;
}
/*
* Packs signature according to Cryptocom rules
* and frees up DSA_SIG structure
*/
/*
int pack_sign_cc(DSA_SIG *s,int order,unsigned char *sig, size_t *siglen)
{
*siglen = 2*order;
memset(sig,0,*siglen);
store_bignum(s->r, sig,order);
store_bignum(s->s, sig + order,order);
dump_signature("serialized",sig,*siglen);
DSA_SIG_free(s);
return 1;
}
*/
/*
* Packs signature according to Cryptopro rules
* and frees up DSA_SIG structure
*/
int pack_sign_cp(DSA_SIG *s,int order,unsigned char *sig, size_t *siglen)
{
*siglen = 2*order;
memset(sig,0,*siglen);
store_bignum(s->s, sig, order);
store_bignum(s->r, sig+order,order);
dump_signature("serialized",sig,*siglen);
DSA_SIG_free(s);
return 1;
}
/*
* Verifies signature passed as DSA_SIG structure
*
*/
int gost_do_verify(const unsigned char *dgst, int dgst_len,
DSA_SIG *sig, DSA *dsa)
{
BIGNUM *md, *tmp=NULL;
BIGNUM *q2=NULL;
BIGNUM *u=NULL,*v=NULL,*z1=NULL,*z2=NULL;
BIGNUM *tmp2=NULL,*tmp3=NULL;
int ok;
BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
if (BN_cmp(sig->s,dsa->q)>=1||
BN_cmp(sig->r,dsa->q)>=1)
{
GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
return 0;
}
md=hashsum2bn(dgst);
tmp=BN_CTX_get(ctx);
v=BN_CTX_get(ctx);
q2=BN_CTX_get(ctx);
z1=BN_CTX_get(ctx);
z2=BN_CTX_get(ctx);
tmp2=BN_CTX_get(ctx);
tmp3=BN_CTX_get(ctx);
u = BN_CTX_get(ctx);
BN_mod(tmp,md,dsa->q,ctx);
if (BN_is_zero(tmp))
{
BN_one(md);
}
BN_copy(q2,dsa->q);
BN_sub_word(q2,2);
BN_mod_exp(v,md,q2,dsa->q,ctx);
BN_mod_mul(z1,sig->s,v,dsa->q,ctx);
BN_sub(tmp,dsa->q,sig->r);
BN_mod_mul(z2,tmp,v,dsa->p,ctx);
BN_mod_exp(tmp,dsa->g,z1,dsa->p,ctx);
BN_mod_exp(tmp2,dsa->pub_key,z2,dsa->p,ctx);
BN_mod_mul(tmp3,tmp,tmp2,dsa->p,ctx);
BN_mod(u,tmp3,dsa->q,ctx);
ok= BN_cmp(u,sig->r);
BN_free(md);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
if (ok!=0)
{
GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_MISMATCH);
}
return (ok==0);
}
/*
* Computes public keys for GOST R 34.10-94 algorithm
*
*/
int gost94_compute_public(DSA *dsa)
{
/* Now fill algorithm parameters with correct values */
BN_CTX *ctx = BN_CTX_new();
if (!dsa->g)
{
GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC,GOST_R_KEY_IS_NOT_INITALIZED);
return 0;
}
/* Compute public key y = a^x mod p */
dsa->pub_key=BN_new();
BN_mod_exp(dsa->pub_key, dsa->g,dsa->priv_key,dsa->p,ctx);
BN_CTX_free(ctx);
return 1;
}
/*
* Fill GOST 94 params, searching them in R3410_paramset array
* by nid of paramset
*
*/
int fill_GOST94_params(DSA *dsa,int nid)
{
R3410_params *params=R3410_paramset;
while (params->nid!=NID_undef && params->nid !=nid) params++;
if (params->nid == NID_undef)
{
GOSTerr(GOST_F_FILL_GOST94_PARAMS,GOST_R_UNSUPPORTED_PARAMETER_SET);
return 0;
}
#define dump_signature(a,b,c)
if (dsa->p) { BN_free(dsa->p); }
dsa->p=NULL;
BN_dec2bn(&(dsa->p),params->p);
if (dsa->q) { BN_free(dsa->q); }
dsa->q=NULL;
BN_dec2bn(&(dsa->q),params->q);
if (dsa->g) { BN_free(dsa->g); }
dsa->g=NULL;
BN_dec2bn(&(dsa->g),params->a);
return 1;
}
/*
* Generate GOST R 34.10-94 keypair
*
*
*/
int gost_sign_keygen(DSA *dsa)
{
dsa->priv_key = BN_new();
BN_rand_range(dsa->priv_key,dsa->q);
return gost94_compute_public( dsa);
}
/* Unpack signature according to cryptocom rules */
/*
DSA_SIG *unpack_cc_signature(const unsigned char *sig,size_t siglen)
{
DSA_SIG *s;
s = DSA_SIG_new();
if (s == NULL)
{
GOSTerr(GOST_F_UNPACK_CC_SIGNATURE,GOST_R_NO_MEMORY);
return(NULL);
}
s->r = getbnfrombuf(sig, siglen/2);
s->s = getbnfrombuf(sig + siglen/2, siglen/2);
return s;
}
*/
/* Unpack signature according to cryptopro rules */
DSA_SIG *unpack_cp_signature(const unsigned char *sig,size_t siglen)
{
DSA_SIG *s;
s = DSA_SIG_new();
if (s == NULL)
{
GOSTerr(GOST_F_UNPACK_CP_SIGNATURE,GOST_R_NO_MEMORY);
return NULL;
}
s->s = getbnfrombuf(sig , siglen/2);
s->r = getbnfrombuf(sig + siglen/2, siglen/2);
return s;
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