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/*
* Copyright (c) 2006 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* 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 above 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. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``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 INSTITUTE 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.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <dh.h>
#include <roken.h>
#include "imath/imath.h"
RCSID("$Id$");
static void
BN2mpz(mpz_t *s, const BIGNUM *bn)
{
size_t len;
void *p;
len = BN_num_bytes(bn);
p = malloc(len);
BN_bn2bin(bn, p);
mp_int_read_unsigned(s, p, len);
free(p);
}
static BIGNUM *
mpz2BN(mpz_t *s)
{
size_t size;
BIGNUM *bn;
void *p;
size = mp_int_unsigned_len(s);
p = malloc(size);
if (p == NULL && size != 0)
return NULL;
mp_int_to_unsigned(s, p, size);
bn = BN_bin2bn(p, size, NULL);
free(p);
return bn;
}
/*
*
*/
#define DH_NUM_TRIES 10
static int
dh_generate_key(DH *dh)
{
mpz_t pub, priv_key, g, p;
int have_private_key = (dh->priv_key != NULL);
int codes, times = 0;
mp_result res;
if (dh->p == NULL || dh->g == NULL)
return 0;
while (times++ < DH_NUM_TRIES) {
if (!have_private_key) {
size_t bits = BN_num_bits(dh->p);
if (dh->priv_key)
BN_free(dh->priv_key);
dh->priv_key = BN_new();
if (dh->priv_key == NULL)
return 0;
if (!BN_rand(dh->priv_key, bits - 1, 0, 0)) {
BN_clear_free(dh->priv_key);
dh->priv_key = NULL;
return 0;
}
}
if (dh->pub_key)
BN_free(dh->pub_key);
mp_int_init(&pub);
mp_int_init(&priv_key);
mp_int_init(&g);
mp_int_init(&p);
BN2mpz(&priv_key, dh->priv_key);
BN2mpz(&g, dh->g);
BN2mpz(&p, dh->p);
res = mp_int_exptmod(&g, &priv_key, &p, &pub);
mp_int_clear(&priv_key);
mp_int_clear(&g);
mp_int_clear(&p);
if (res != MP_OK)
continue;
dh->pub_key = mpz2BN(&pub);
mp_int_clear(&pub);
if (dh->pub_key == NULL)
return 0;
if (DH_check_pubkey(dh, dh->pub_key, &codes) && codes == 0)
break;
if (have_private_key)
return 0;
}
if (times >= DH_NUM_TRIES) {
if (!have_private_key && dh->priv_key) {
BN_free(dh->priv_key);
dh->priv_key = NULL;
}
if (dh->pub_key) {
BN_free(dh->pub_key);
dh->pub_key = NULL;
}
return 0;
}
return 1;
}
static int
dh_compute_key(unsigned char *shared, const BIGNUM * pub, DH *dh)
{
mpz_t s, priv_key, p, peer_pub;
size_t size = 0;
mp_result res;
if (dh->pub_key == NULL || dh->g == NULL || dh->priv_key == NULL)
return -1;
mp_int_init(&p);
BN2mpz(&p, dh->p);
mp_int_init(&peer_pub);
BN2mpz(&peer_pub, pub);
/* check if peers pubkey is reasonable */
if (MP_SIGN(&peer_pub) == MP_NEG
|| mp_int_compare(&peer_pub, &p) >= 0
|| mp_int_compare_value(&peer_pub, 1) <= 0)
{
mp_int_clear(&p);
mp_int_clear(&peer_pub);
return -1;
}
mp_int_init(&priv_key);
BN2mpz(&priv_key, dh->priv_key);
mp_int_init(&s);
mp_int_exptmod(&peer_pub, &priv_key, &p, &s);
mp_int_clear(&p);
mp_int_clear(&peer_pub);
mp_int_clear(&priv_key);
size = mp_int_unsigned_len(&s);
res = mp_int_to_unsigned(&s, shared, size);
mp_int_clear(&s);
return (res == MP_OK) ? size : -1;
}
static int
dh_generate_params(DH *dh, int a, int b, BN_GENCB *callback)
{
/* groups should already be known, we don't care about this */
return 0;
}
static int
dh_init(DH *dh)
{
return 1;
}
static int
dh_finish(DH *dh)
{
return 1;
}
/*
*
*/
const DH_METHOD _hc_dh_imath_method = {
"hcrypto imath DH",
dh_generate_key,
dh_compute_key,
NULL,
dh_init,
dh_finish,
0,
NULL,
dh_generate_params
};
/**
* DH implementation using libimath.
*
* @return the DH_METHOD for the DH implementation using libimath.
*
* @ingroup hcrypto_dh
*/
const DH_METHOD *
DH_imath_method(void)
{
return &_hc_dh_imath_method;
}
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