/*
 *
 * Copyright (c) 2011-2016 The University of Waikato, Hamilton, New Zealand.
 * All rights reserved.
 *
 * This file is part of libprotoident.
 *
 * This code has been developed by the University of Waikato WAND
 * research group. For further information please see http://www.wand.net.nz/
 *
 * libprotoident is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * libprotoident 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 */

#include <string.h>

#include "libprotoident.h"
#include "proto_manager.h"
#include "proto_common.h"

static bool match_facetime_stun_request(uint32_t payload, uint32_t len) {

        /* Bytes 3 and 4 are the Message Length - the STUN header */
        if ((ntohl(payload) & 0x0000ffff) != len - 20)
                return false;

        if (MATCH(payload, 0x0f, 0xe0, ANY, ANY))
                return true;
        if (MATCH(payload, 0x0f, 0xe1, ANY, ANY))
                return true;
        if (MATCH(payload, 0x0f, 0xe4, ANY, ANY))
                return true;
        return false;

}

static bool match_facetime_stun_response(uint32_t payload, uint32_t len) {

        /* Bytes 3 and 4 are the Message Length - the STUN header */
        if ((ntohl(payload) & 0x0000ffff) != len - 20)
                return false;

        if (MATCH(payload, 0x0e, 0xe0, ANY, ANY))
                return true;
        if (MATCH(payload, 0x0e, 0xe1, ANY, ANY))
                return true;
        if (MATCH(payload, 0x0e, 0xe4, ANY, ANY))
                return true;
        return false;

}

static bool match_skype_stun_request(uint32_t payload, uint32_t len) {

        /* Bytes 3 and 4 are the Message Length - the STUN header */
        if ((ntohl(payload) & 0x0000ffff) != len - 20)
                return false;

        /* These flows start with an Allocate Request */
        if (MATCH(payload, 0x00, 0x03, ANY, ANY))
                return true;

        return false;

}

static bool match_stun_payload(uint32_t payload, uint32_t len) {

        if (len == 0)
                return true;

        /* Bytes 3 and 4 are the Message Length - the STUN header */
        if ((ntohl(payload) & 0x0000ffff) != len - 20)
                return false;

        if (MATCH(payload, 0x00, 0x01, ANY, ANY))
                return true;
        if (MATCH(payload, 0x01, 0x01, ANY, ANY))
                return true;
        if (MATCH(payload, 0x01, 0x11, ANY, ANY))
                return true;
        if (MATCH(payload, 0x00, 0x03, ANY, ANY))
                return true;
        if (MATCH(payload, 0x01, 0x03, ANY, ANY))
                return true;
        if (MATCH(payload, 0x01, 0x13, ANY, ANY))
                return true;

        /* Data Indication message (used by Skype) */
        if (MATCH(payload, 0x01, 0x15, ANY, ANY))
                return true;

        return false;

}


static inline bool match_stun(lpi_data_t *data, lpi_module_t *mod UNUSED) {

	/* This seems to be a special response containing a STUN token
         *
         * Not very well-documented though :(
         */

        if (match_str_either(data, "RSP/"))
                return true;

        if (match_stun_payload(data->payload[0], data->payload_len[0])) {
                if (match_stun_payload(data->payload[1], data->payload_len[1]))
                        return true;
        }

        if (match_facetime_stun_request(data->payload[0], data->payload_len[0]))
        {
                if ((data->payload[0] & 0xff0000) ==
                                (data->payload[1] & 0xff0000) && 
                                match_facetime_stun_response(data->payload[1],
                                        data->payload_len[1])) {
                        return true;
                }
        }

        if (match_facetime_stun_request(data->payload[1], data->payload_len[1]))
        {
                /* Byte 2 must match for both directions */
                if ((data->payload[0] & 0xff0000) ==
                                (data->payload[1] & 0xff0000) && 
                                match_facetime_stun_response(data->payload[0],
                                        data->payload_len[0])) {
                        return true;
                }
        }

	return false;
}

static lpi_module_t lpi_stun = {
	LPI_PROTO_UDP_STUN,
	LPI_CATEGORY_NAT,
	"STUN",
	3,
	match_stun
};

void register_stun(LPIModuleMap *mod_map) {
	register_protocol(&lpi_stun, mod_map);
}