#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rand.h>
#include <openssl/dh.h>
static int generate_key(DH *dh);
static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx,
BN_MONT_CTX *m_ctx);
static int dh_init(DH *dh);
static int dh_finish(DH *dh);
int DH_generate_key(DH *dh)
{
return dh->meth->generate_key(dh);
}
int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
return dh->meth->compute_key(key, pub_key, dh);
}
static DH_METHOD dh_ossl = {
"OpenSSL DH Method",
generate_key,
compute_key,
dh_bn_mod_exp,
dh_init,
dh_finish,
0,
NULL
};
const DH_METHOD *DH_OpenSSL(void)
{
return &dh_ossl;
}
static int generate_key(DH *dh)
{
int ok=0;
int generate_new_key=0;
unsigned l;
BN_CTX *ctx;
BN_MONT_CTX *mont;
BIGNUM *pub_key=NULL,*priv_key=NULL;
ctx = BN_CTX_new();
if (ctx == NULL) goto err;
if (dh->priv_key == NULL)
{
priv_key=BN_new();
if (priv_key == NULL) goto err;
generate_new_key=1;
}
else
priv_key=dh->priv_key;
if (dh->pub_key == NULL)
{
pub_key=BN_new();
if (pub_key == NULL) goto err;
}
else
pub_key=dh->pub_key;
if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
{
if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
dh->p,ctx)) goto err;
}
mont=(BN_MONT_CTX *)dh->method_mont_p;
if (generate_new_key)
{
l = dh->length ? dh->length : BN_num_bits(dh->p)-1;
if (!BN_rand(priv_key, l, 0, 0)) goto err;
}
if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key,dh->p,ctx,mont))
goto err;
dh->pub_key=pub_key;
dh->priv_key=priv_key;
ok=1;
err:
if (ok != 1)
DHerr(DH_F_DH_GENERATE_KEY,ERR_R_BN_LIB);
if ((pub_key != NULL) && (dh->pub_key == NULL)) BN_free(pub_key);
if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
BN_CTX_free(ctx);
return(ok);
}
static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
BN_CTX *ctx;
BN_MONT_CTX *mont;
BIGNUM *tmp;
int ret= -1;
ctx = BN_CTX_new();
if (ctx == NULL) goto err;
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
if (dh->priv_key == NULL)
{
DHerr(DH_F_DH_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
goto err;
}
if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
{
if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
dh->p,ctx)) goto err;
}
mont=(BN_MONT_CTX *)dh->method_mont_p;
if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
{
DHerr(DH_F_DH_COMPUTE_KEY,ERR_R_BN_LIB);
goto err;
}
ret=BN_bn2bin(tmp,key);
err:
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return(ret);
}
static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx,
BN_MONT_CTX *m_ctx)
{
if (a->top == 1)
{
BN_ULONG A = a->d[0];
return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);
}
else
return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx);
}
static int dh_init(DH *dh)
{
dh->flags |= DH_FLAG_CACHE_MONT_P;
return(1);
}
static int dh_finish(DH *dh)
{
if(dh->method_mont_p)
BN_MONT_CTX_free((BN_MONT_CTX *)dh->method_mont_p);
return(1);
}