302 lines
7.2 KiB
C
302 lines
7.2 KiB
C
/**********************************************************************
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* gost_sign.c *
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* Copyright (c) 2005-2006 Cryptocom LTD *
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* This file is distributed under the same license as OpenSSL *
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* *
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* Implementation of GOST R 34.10-94 signature algoritgthm *
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* for OpenSSL *
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* Requires OpenSSL 0.9.9 for compilation *
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**********************************************************************/
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#include <string.h>
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#include <openssl/rand.h>
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#include <openssl/bn.h>
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#include <openssl/dsa.h>
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#include <openssl/evp.h>
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#include "sign.h"
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#include "paramset.h"
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#include "tools.h"
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#include "e_gost_err.h"
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#ifdef DEBUG_SIGN
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void dump_signature(const char *message,const unsigned char *buffer,size_t len) {
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size_t i;
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fprintf(stderr,"signature %s Length=%d",message,len);
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for (i=0; i<len; i++) {
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if (i% 16 ==0) fputc('\n',stderr);
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fprintf (stderr," %02x",buffer[i]);
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}
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fprintf(stderr,"\nEnd of signature\n");
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}
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void dump_dsa_sig(const char *message, DSA_SIG *sig) {
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fprintf(stderr,"%s\nR=",message);
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BN_print_fp(stderr,sig->r);
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fprintf(stderr,"\nS=");
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BN_print_fp(stderr,sig->s);
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fprintf(stderr,"\n");
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}
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#else
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#define dump_signature(a,b,c)
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#define dump_dsa_sig(a,b)
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#endif
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/*
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* Computes signature and returns it as DSA_SIG structure
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*/
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DSA_SIG *gost_do_sign(const unsigned char *dgst,int dlen, DSA *dsa)
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{
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BIGNUM *k=NULL,*tmp=NULL,*tmp2=NULL;
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DSA_SIG *newsig = DSA_SIG_new();
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BIGNUM *md = hashsum2bn(dgst);
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/* check if H(M) mod q is zero */
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BN_CTX *ctx=BN_CTX_new();
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BN_CTX_start(ctx);
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if (!newsig)
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{
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GOSTerr(GOST_F_GOST_DO_SIGN,GOST_R_NO_MEMORY);
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goto err;
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}
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tmp=BN_CTX_get(ctx);
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k = BN_CTX_get(ctx);
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tmp2 = BN_CTX_get(ctx);
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BN_mod(tmp,md,dsa->q,ctx);
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if (BN_is_zero(tmp))
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{
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BN_one(md);
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}
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do {
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do {
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/*Generate random number k less than q*/
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BN_rand_range(k,dsa->q);
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/* generate r = (a^x mod p) mod q */
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BN_mod_exp(tmp,dsa->g, k, dsa->p,ctx);
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if (!(newsig->r)) newsig->r=BN_new();
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BN_mod(newsig->r,tmp,dsa->q,ctx);
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} while (BN_is_zero(newsig->r));
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/* generate s = (xr + k(Hm)) mod q */
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BN_mod_mul(tmp,dsa->priv_key,newsig->r,dsa->q,ctx);
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BN_mod_mul(tmp2,k,md,dsa->q,ctx);
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if (!newsig->s) newsig->s=BN_new();
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BN_mod_add(newsig->s,tmp,tmp2,dsa->q,ctx);
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} while (BN_is_zero(newsig->s));
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err:
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BN_free(md);
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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return newsig;
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}
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/*
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* Packs signature according to Cryptocom rules
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* and frees up DSA_SIG structure
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*/
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int pack_sign_cc(DSA_SIG *s,int order,unsigned char *sig, unsigned int *siglen)
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{
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*siglen = 2*order;
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memset(sig,0,*siglen);
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store_bignum(s->r, sig,order);
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store_bignum(s->s, sig + order,order);
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dump_signature("serialized",sig,*siglen);
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DSA_SIG_free(s);
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return 1;
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}
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/*
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* Packs signature according to Cryptopro rules
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* and frees up DSA_SIG structure
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*/
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int pack_sign_cp(DSA_SIG *s,int order,unsigned char *sig, unsigned int *siglen)
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{
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*siglen = 2*order;
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memset(sig,0,*siglen);
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store_bignum(s->s, sig, order);
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store_bignum(s->r, sig+order,order);
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dump_signature("serialized",sig,*siglen);
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DSA_SIG_free(s);
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return 1;
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}
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/*
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* Verifies signature passed as DSA_SIG structure
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*
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*/
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int gost_do_verify(const unsigned char *dgst, int dgst_len,
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DSA_SIG *sig, DSA *dsa)
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{
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BIGNUM *md, *tmp=NULL;
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BIGNUM *q2=NULL;
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BIGNUM *u=NULL,*v=NULL,*z1=NULL,*z2=NULL;
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BIGNUM *tmp2=NULL,*tmp3=NULL;
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int ok;
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BN_CTX *ctx = BN_CTX_new();
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BN_CTX_start(ctx);
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if (BN_cmp(sig->s,dsa->q)>=1||
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BN_cmp(sig->r,dsa->q)>=1)
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{
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GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
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return 0;
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}
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md=hashsum2bn(dgst);
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tmp=BN_CTX_get(ctx);
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v=BN_CTX_get(ctx);
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q2=BN_CTX_get(ctx);
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z1=BN_CTX_get(ctx);
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z2=BN_CTX_get(ctx);
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tmp2=BN_CTX_get(ctx);
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tmp3=BN_CTX_get(ctx);
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u = BN_CTX_get(ctx);
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BN_mod(tmp,md,dsa->q,ctx);
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if (BN_is_zero(tmp)) {
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BN_one(md);
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}
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BN_copy(q2,dsa->q);
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BN_sub_word(q2,2);
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BN_mod_exp(v,md,q2,dsa->q,ctx);
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BN_mod_mul(z1,sig->s,v,dsa->q,ctx);
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BN_sub(tmp,dsa->q,sig->r);
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BN_mod_mul(z2,tmp,v,dsa->p,ctx);
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BN_mod_exp(tmp,dsa->g,z1,dsa->p,ctx);
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BN_mod_exp(tmp2,dsa->pub_key,z2,dsa->p,ctx);
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BN_mod_mul(tmp3,tmp,tmp2,dsa->p,ctx);
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BN_mod(u,tmp3,dsa->q,ctx);
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ok= BN_cmp(u,sig->r);
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BN_free(md);
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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if (ok!=0) {
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GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_MISMATCH);
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}
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return (ok==0);
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}
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/*
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* Computes public keys for GOST R 34.10-94 algorithm
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*
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*/
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int gost94_compute_public(DSA *dsa)
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{
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/* Now fill algorithm parameters with correct values */
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BN_CTX *ctx = BN_CTX_new();
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if (!dsa->g) {
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GOSTerr(GOST_F_GOST_COMPUTE_PUBLIC,GOST_R_KEY_IS_NOT_INITALIZED);
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return 0;
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}
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/* Compute public key y = a^x mod p */
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dsa->pub_key=BN_new();
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BN_mod_exp(dsa->pub_key, dsa->g,dsa->priv_key,dsa->p,ctx);
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BN_CTX_free(ctx);
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return 1;
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}
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/*
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* Fill GOST 94 params, searching them in R3410_paramset array
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* by nid of paramset
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*
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*/
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int fill_GOST94_params(DSA *dsa,int nid) {
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R3410_params *params=R3410_paramset;
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while (params->nid!=NID_undef && params->nid !=nid) params++;
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if (params->nid == NID_undef)
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{
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GOSTerr(GOST_F_FILL_GOST94_PARAMS,GOST_R_UNSUPPORTED_PARAMETER_SET);
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return 0;
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}
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#define dump_signature(a,b,c)
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if (dsa->p) { BN_free(dsa->p); }
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dsa->p=NULL;
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BN_dec2bn(&(dsa->p),params->p);
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if (dsa->q) { BN_free(dsa->q); }
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dsa->q=NULL;
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BN_dec2bn(&(dsa->q),params->q);
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if (dsa->g) { BN_free(dsa->g); }
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dsa->g=NULL;
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BN_dec2bn(&(dsa->g),params->a);
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return 1;
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}
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/*
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* Generate GOST R 34.10-94 keypair
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*
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*
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*/
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int gost_sign_keygen(DSA *dsa)
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{
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dsa->priv_key = BN_new();
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BN_rand_range(dsa->priv_key,dsa->q);
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return gost94_compute_public( dsa);
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}
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/* Unpack signature according to cryptocom rules */
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DSA_SIG *unpack_cc_signature(const unsigned char *sig,size_t siglen)
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{
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DSA_SIG *s;
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s = DSA_SIG_new();
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if (s == NULL) {
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GOSTerr(GOST_F_UNPACK_CC_SIGNATURE,GOST_R_NO_MEMORY);
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return(NULL);
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}
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s->r = getbnfrombuf(sig, siglen/2);
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s->s = getbnfrombuf(sig + siglen/2, siglen/2);
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return s;
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}
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/* Unpack signature according to cryptopro rules */
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DSA_SIG *unpack_cp_signature(const unsigned char *sig,size_t siglen)
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{
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DSA_SIG *s;
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s = DSA_SIG_new();
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if (s == NULL) {
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GOSTerr(GOST_F_UNPACK_CP_SIGNATURE,GOST_R_NO_MEMORY);
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return NULL;
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}
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s->s = getbnfrombuf(sig , siglen/2);
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s->r = getbnfrombuf(sig + siglen/2, siglen/2);
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return s;
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}
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/* Convert little-endian byte array into bignum */
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BIGNUM *hashsum2bn(const unsigned char *dgst)
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{ unsigned char buf[32];
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int i;
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for (i=0;i<32;i++) {
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buf[31-i]=dgst[i];
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}
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return getbnfrombuf(buf,32);
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}
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/* Convert byte buffer to bignum, skipping leading zeros*/
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BIGNUM *getbnfrombuf(const unsigned char *buf,size_t len) {
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while (*buf==0&&len>0) {
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buf++; len--;
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}
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if (len) {
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return BN_bin2bn(buf,len,NULL);
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} else {
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BIGNUM *b=BN_new();
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BN_zero(b);
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return b;
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}
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}
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/* Pack bignum into byte buffer of given size, filling all leading bytes
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* by zeros */
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int store_bignum(BIGNUM *bn, unsigned char *buf,int len) {
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int bytes = BN_num_bytes(bn);
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if (bytes>len) return 0;
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memset(buf,0,len);
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BN_bn2bin(bn,buf+len-bytes);
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return 1;
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}
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