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/**
* @file psk_authenticator.c
*
* @brief Implementation of psk_authenticator_t.
*
*/
/*
* Copyright (C) 2005-2006 Martin Willi
* Copyright (C) 2005 Jan Hutter
* 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 <string.h>
#include "psk_authenticator.h"
#include <daemon.h>
/**
* Key pad for the AUTH method SHARED_KEY_MESSAGE_INTEGRITY_CODE.
*/
#define IKEV2_KEY_PAD "Key Pad for IKEv2"
#define IKEV2_KEY_PAD_LENGTH 17
typedef struct private_psk_authenticator_t private_psk_authenticator_t;
/**
* Private data of an psk_authenticator_t object.
*/
struct private_psk_authenticator_t {
/**
* Public authenticator_t interface.
*/
psk_authenticator_t public;
/**
* Assigned IKE_SA
*/
ike_sa_t *ike_sa;
};
/**
* Builds the octets to be signed as described in section 2.15 of RFC 4306
*/
chunk_t build_tbs_octets(chunk_t ike_sa_init, chunk_t nonce,
identification_t *id, prf_t *prf)
{
u_int8_t id_header_buf[] = {0x00, 0x00, 0x00, 0x00};
chunk_t id_header = chunk_from_buf(id_header_buf);
chunk_t id_with_header, id_prfd, id_encoding;
id_header_buf[0] = id->get_type(id);
id_encoding = id->get_encoding(id);
id_with_header = chunk_cat("cc", id_header, id_encoding);
prf->allocate_bytes(prf, id_with_header, &id_prfd);
chunk_free(&id_with_header);
return chunk_cat("ccm", ike_sa_init, nonce, id_prfd);
}
/**
* Creates the AUTH data using auth method SHARED_KEY_MESSAGE_INTEGRITY_CODE.
*/
chunk_t build_shared_key_signature(chunk_t ike_sa_init, chunk_t nonce,
chunk_t secret, identification_t *id,
chunk_t skp, prf_t *prf)
{
chunk_t key_pad, key, auth_data, octets;
prf->set_key(prf, skp);
octets = build_tbs_octets(ike_sa_init, nonce, id, prf);
/* AUTH = prf(prf(Shared Secret,"Key Pad for IKEv2"), <msg octets>) */
key_pad.ptr = IKEV2_KEY_PAD;
key_pad.len = IKEV2_KEY_PAD_LENGTH;
prf->set_key(prf, secret);
prf->allocate_bytes(prf, key_pad, &key);
prf->set_key(prf, key);
prf->allocate_bytes(prf, octets, &auth_data);
DBG3(DBG_IKE, "octets = message + nonce + prf(Sk_px, IDx') %B", &octets);
DBG3(DBG_IKE, "secret %B", &secret);
DBG3(DBG_IKE, "keypad %B", &key_pad);
DBG3(DBG_IKE, "prf(secret, keypad) %B", &key);
DBG3(DBG_IKE, "AUTH = prf(prf(secret, keypad), octets) %B", &auth_data);
chunk_free(&octets);
chunk_free(&key);
return auth_data;
}
/**
* Implementation of authenticator_t.verify.
*/
static status_t verify(private_psk_authenticator_t *this, chunk_t ike_sa_init,
chunk_t my_nonce, auth_payload_t *auth_payload)
{
status_t status;
chunk_t auth_data, recv_auth_data, shared_key;
identification_t *my_id, *other_id;
my_id = this->ike_sa->get_my_id(this->ike_sa);
other_id = this->ike_sa->get_other_id(this->ike_sa);
status = charon->credentials->get_shared_key(charon->credentials, my_id,
other_id, &shared_key);
if (status != SUCCESS)
{
DBG1(DBG_IKE, "no shared key found for '%D' - '%D'", my_id, other_id);
return status;
}
auth_data = build_shared_key_signature(ike_sa_init, my_nonce, shared_key,
other_id, this->ike_sa->get_skp_verify(this->ike_sa),
this->ike_sa->get_prf(this->ike_sa));
chunk_free(&shared_key);
recv_auth_data = auth_payload->get_data(auth_payload);
if (auth_data.len != recv_auth_data.len ||
!memeq(auth_data.ptr, recv_auth_data.ptr, auth_data.len))
{
DBG1(DBG_IKE, "PSK MAC verification failed");
chunk_free(&auth_data);
return FAILED;
}
chunk_free(&auth_data);
DBG1(DBG_IKE, "authentication of '%D' with %N successful",
other_id, auth_method_names, AUTH_PSK);
return SUCCESS;
}
/**
* Implementation of authenticator_t.build.
*/
static status_t build(private_psk_authenticator_t *this, chunk_t ike_sa_init,
chunk_t other_nonce, auth_payload_t **auth_payload)
{
chunk_t shared_key;
chunk_t auth_data;
status_t status;
identification_t *my_id, *other_id;
my_id = this->ike_sa->get_my_id(this->ike_sa);
other_id = this->ike_sa->get_other_id(this->ike_sa);
DBG1(DBG_IKE, "authentication of '%D' (myself) with %N",
my_id, auth_method_names, AUTH_PSK);
status = charon->credentials->get_shared_key(charon->credentials, my_id,
other_id, &shared_key);
if (status != SUCCESS)
{
DBG1(DBG_IKE, "no shared key found for '%D' - '%D'", my_id, other_id);
return status;
}
auth_data = build_shared_key_signature(ike_sa_init, other_nonce, shared_key,
my_id, this->ike_sa->get_skp_build(this->ike_sa),
this->ike_sa->get_prf(this->ike_sa));
DBG2(DBG_IKE, "successfully created shared key MAC");
chunk_free(&shared_key);
*auth_payload = auth_payload_create();
(*auth_payload)->set_auth_method(*auth_payload, AUTH_PSK);
(*auth_payload)->set_data(*auth_payload, auth_data);
chunk_free(&auth_data);
return SUCCESS;
}
/**
* Implementation of authenticator_t.destroy.
*/
static void destroy(private_psk_authenticator_t *this)
{
free(this);
}
/*
* Described in header.
*/
psk_authenticator_t *psk_authenticator_create(ike_sa_t *ike_sa)
{
private_psk_authenticator_t *this = malloc_thing(private_psk_authenticator_t);
/* public functions */
this->public.authenticator_interface.verify = (status_t(*)(authenticator_t*,chunk_t,chunk_t,auth_payload_t*))verify;
this->public.authenticator_interface.build = (status_t(*)(authenticator_t*,chunk_t,chunk_t,auth_payload_t**))build;
this->public.authenticator_interface.destroy = (void(*)(authenticator_t*))destroy;
/* private data */
this->ike_sa = ike_sa;
return &this->public;
}
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