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/*
* Copyright (C) 2018 Tobias Brunner
* HSR 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/evp.h>
/* basic support for X25519 was added with 1.1.0a, but we require features (e.g.
* to load the keys) that were only added with 1.1.1 */
#if OPENSSL_VERSION_NUMBER >= 0x1010100fL && !defined(OPENSSL_NO_ECDH)
#include "openssl_x_diffie_hellman.h"
#include <utils/debug.h>
typedef struct private_diffie_hellman_t private_diffie_hellman_t;
/**
* Private data
*/
struct private_diffie_hellman_t {
/**
* Public interface.
*/
diffie_hellman_t public;
/**
* Diffie Hellman group number.
*/
diffie_hellman_group_t group;
/**
* Private (public) key
*/
EVP_PKEY *key;
/**
* Shared secret
*/
chunk_t shared_secret;
/**
* True if shared secret is computed
*/
bool computed;
};
/**
* Map a DH group to a key type
*/
static int map_key_type(diffie_hellman_group_t group)
{
switch (group)
{
case CURVE_25519:
return EVP_PKEY_X25519;
case CURVE_448:
return EVP_PKEY_X448;
default:
return 0;
}
}
/**
* Compute the shared secret
*/
static bool compute_shared_key(private_diffie_hellman_t *this, EVP_PKEY *pub,
chunk_t *shared_secret)
{
EVP_PKEY_CTX *ctx;
bool success = FALSE;
ctx = EVP_PKEY_CTX_new(this->key, NULL);
if (!ctx)
{
return FALSE;
}
if (EVP_PKEY_derive_init(ctx) <= 0)
{
goto error;
}
if (EVP_PKEY_derive_set_peer(ctx, pub) <= 0)
{
goto error;
}
if (EVP_PKEY_derive(ctx, NULL, &shared_secret->len) <= 0)
{
goto error;
}
*shared_secret = chunk_alloc(shared_secret->len);
if (EVP_PKEY_derive(ctx, shared_secret->ptr, &shared_secret->len) <= 0)
{
goto error;
}
success = TRUE;
error:
EVP_PKEY_CTX_free(ctx);
return success;
}
METHOD(diffie_hellman_t, set_other_public_value, bool,
private_diffie_hellman_t *this, chunk_t value)
{
EVP_PKEY *pub;
if (!diffie_hellman_verify_value(this->group, value))
{
return FALSE;
}
pub = EVP_PKEY_new_raw_public_key(map_key_type(this->group), NULL,
value.ptr, value.len);
if (!pub)
{
DBG1(DBG_LIB, "%N public value is malformed",
diffie_hellman_group_names, this->group);
return FALSE;
}
chunk_clear(&this->shared_secret);
if (!compute_shared_key(this, pub, &this->shared_secret))
{
DBG1(DBG_LIB, "%N shared secret computation failed",
diffie_hellman_group_names, this->group);
EVP_PKEY_free(pub);
return FALSE;
}
this->computed = TRUE;
EVP_PKEY_free(pub);
return TRUE;
}
METHOD(diffie_hellman_t, get_my_public_value, bool,
private_diffie_hellman_t *this, chunk_t *value)
{
size_t len;
if (!EVP_PKEY_get_raw_public_key(this->key, NULL, &len))
{
return FALSE;
}
*value = chunk_alloc(len);
if (!EVP_PKEY_get_raw_public_key(this->key, value->ptr, &value->len))
{
chunk_free(value);
return FALSE;
}
return TRUE;
}
METHOD(diffie_hellman_t, set_private_value, bool,
private_diffie_hellman_t *this, chunk_t value)
{
EVP_PKEY_free(this->key);
this->key = EVP_PKEY_new_raw_private_key(map_key_type(this->group), NULL,
value.ptr, value.len);
if (!this->key)
{
return FALSE;
}
return TRUE;
}
METHOD(diffie_hellman_t, get_shared_secret, bool,
private_diffie_hellman_t *this, chunk_t *secret)
{
if (!this->computed)
{
return FALSE;
}
*secret = chunk_clone(this->shared_secret);
return TRUE;
}
METHOD(diffie_hellman_t, get_dh_group, diffie_hellman_group_t,
private_diffie_hellman_t *this)
{
return this->group;
}
METHOD(diffie_hellman_t, destroy, void,
private_diffie_hellman_t *this)
{
EVP_PKEY_free(this->key);
chunk_clear(&this->shared_secret);
free(this);
}
/*
* Described in header
*/
diffie_hellman_t *openssl_x_diffie_hellman_create(diffie_hellman_group_t group)
{
private_diffie_hellman_t *this;
EVP_PKEY_CTX *ctx = NULL;
EVP_PKEY *key = NULL;
switch (group)
{
case CURVE_25519:
ctx = EVP_PKEY_CTX_new_id(NID_X25519, NULL);
break;
case CURVE_448:
ctx = EVP_PKEY_CTX_new_id(NID_X448, NULL);
break;
default:
break;
}
if (!ctx ||
EVP_PKEY_keygen_init(ctx) <= 0 ||
EVP_PKEY_keygen(ctx, &key) <= 0)
{
DBG1(DBG_LIB, "generating key for %N failed",
diffie_hellman_group_names, group);
EVP_PKEY_CTX_free(ctx);
return NULL;
}
EVP_PKEY_CTX_free(ctx);
INIT(this,
.public = {
.get_shared_secret = _get_shared_secret,
.set_other_public_value = _set_other_public_value,
.get_my_public_value = _get_my_public_value,
.set_private_value = _set_private_value,
.get_dh_group = _get_dh_group,
.destroy = _destroy,
},
.group = group,
.key = key,
);
return &this->public;
}
#endif /* OPENSSL_NO_ECDH */
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