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/*
* Copyright (C) 2008-2010 Tobias Brunner
* Copyright (C) 2008 Martin Willi
* Hochschule fuer Technik Rapperswil
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
#include <openssl/dh.h>
#include "openssl_diffie_hellman.h"
#include <debug.h>
typedef struct private_openssl_diffie_hellman_t private_openssl_diffie_hellman_t;
/**
* Private data of an openssl_diffie_hellman_t object.
*/
struct private_openssl_diffie_hellman_t {
/**
* Public openssl_diffie_hellman_t interface.
*/
openssl_diffie_hellman_t public;
/**
* Diffie Hellman group number.
*/
u_int16_t group;
/**
* Diffie Hellman object
*/
DH *dh;
/**
* Other public value
*/
BIGNUM *pub_key;
/**
* Shared secret
*/
chunk_t shared_secret;
/**
* True if shared secret is computed
*/
bool computed;
};
METHOD(diffie_hellman_t, get_my_public_value, void,
private_openssl_diffie_hellman_t *this, chunk_t *value)
{
*value = chunk_alloc(DH_size(this->dh));
memset(value->ptr, 0, value->len);
BN_bn2bin(this->dh->pub_key,
value->ptr + value->len - BN_num_bytes(this->dh->pub_key));
}
METHOD(diffie_hellman_t, get_shared_secret, status_t,
private_openssl_diffie_hellman_t *this, chunk_t *secret)
{
if (!this->computed)
{
return FAILED;
}
/* shared secret should requires a len according the DH group */
*secret = chunk_alloc(DH_size(this->dh));
memset(secret->ptr, 0, secret->len);
memcpy(secret->ptr + secret->len - this->shared_secret.len,
this->shared_secret.ptr, this->shared_secret.len);
return SUCCESS;
}
METHOD(diffie_hellman_t, set_other_public_value, void,
private_openssl_diffie_hellman_t *this, chunk_t value)
{
int len;
BN_bin2bn(value.ptr, value.len, this->pub_key);
chunk_clear(&this->shared_secret);
this->shared_secret.ptr = malloc(DH_size(this->dh));
memset(this->shared_secret.ptr, 0xFF, this->shared_secret.len);
len = DH_compute_key(this->shared_secret.ptr, this->pub_key, this->dh);
if (len < 0)
{
DBG1(DBG_LIB, "DH shared secret computation failed");
return;
}
this->shared_secret.len = len;
this->computed = TRUE;
}
METHOD(diffie_hellman_t, get_dh_group, diffie_hellman_group_t,
private_openssl_diffie_hellman_t *this)
{
return this->group;
}
/**
* Lookup the modulus in modulo table
*/
static status_t set_modulus(private_openssl_diffie_hellman_t *this)
{
diffie_hellman_params_t *params = diffie_hellman_get_params(this->group);
if (!params)
{
return NOT_FOUND;
}
this->dh->p = BN_bin2bn(params->prime.ptr, params->prime.len, NULL);
this->dh->g = BN_bin2bn(params->generator.ptr, params->generator.len, NULL);
if (params->exp_len != params->prime.len)
{
this->dh->length = params->exp_len * 8;
}
return SUCCESS;
}
METHOD(diffie_hellman_t, destroy, void,
private_openssl_diffie_hellman_t *this)
{
BN_clear_free(this->pub_key);
DH_free(this->dh);
chunk_clear(&this->shared_secret);
free(this);
}
/*
* Described in header.
*/
openssl_diffie_hellman_t *openssl_diffie_hellman_create(diffie_hellman_group_t group)
{
private_openssl_diffie_hellman_t *this;
INIT(this,
.public.dh = {
.get_shared_secret = _get_shared_secret,
.set_other_public_value = _set_other_public_value,
.get_my_public_value = _get_my_public_value,
.get_dh_group = _get_dh_group,
.destroy = _destroy,
},
);
this->dh = DH_new();
if (!this->dh)
{
free(this);
return NULL;
}
this->group = group;
this->computed = FALSE;
this->pub_key = BN_new();
this->shared_secret = chunk_empty;
/* find a modulus according to group */
if (set_modulus(this) != SUCCESS)
{
destroy(this);
return NULL;
}
/* generate my public and private values */
if (!DH_generate_key(this->dh))
{
destroy(this);
return NULL;
}
DBG2(DBG_LIB, "size of DH secret exponent: %d bits",
BN_num_bits(this->dh->priv_key));
return &this->public;
}
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