stellar-stellar/decoders/glimpse_detector/libprotoident/udp/lpi_openvpn.cc

/*
 *
 * 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"

/* Thanks to Remy Mudingay for providing traces to identify this protocol */

static inline bool match_openvpn_handshake(uint32_t pl_a, uint32_t pl_b) {


	/* 0x31 and 0x37 are commonly used as the first byte of a UDP
	 * OpenVPN exchange. However, if one end uses 0x31 then the other
	 * must also use 0x31 -- same for 0x37. 
	 */

	if (MATCH(pl_a, 0x31, ANY, ANY, ANY)) {
		if (MATCH(pl_b, 0x31, ANY, ANY, ANY))
			return true;
	}
	
	if (MATCH(pl_a, 0x37, ANY, ANY, ANY)) {
		if (MATCH(pl_b, 0x37, ANY, ANY, ANY))
			return true;
	}

	if (MATCH(pl_a, 0x49, ANY, ANY, ANY)) {
		if (MATCH(pl_b, 0x49, ANY, ANY, ANY))
			return true;
	}

	return false;

}

static inline bool match_tunnelbear_40(uint32_t payload, uint32_t len) {
        if (!MATCH(payload, 0x40, ANY, ANY, ANY))
                return false;
        if (len != 26)
                return false;
        return true;

}

static inline bool match_tunnelbear_38(uint32_t payload, uint32_t len) {
        if (!MATCH(payload, 0x38, ANY, ANY, ANY))
                return false;
        if (len != 14 && len != 126 && len != 128)
                return false;
        return true;

}

static inline bool match_wscribe_40(uint32_t payload, uint32_t len) {
        if (!MATCH(payload, 0x40, ANY, ANY, ANY))
                return false;
        if (len != 98)
                return false;
        return true;

}

static inline bool match_wscribe_38(uint32_t payload, uint32_t len) {
        if (!MATCH(payload, 0x38, ANY, ANY, ANY))
                return false;
        if (len != 86)
                return false;
        return true;

}

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

	if (data->server_port == 53 || data->client_port == 53) {
		return false;
	}

	/* The payload matching alone isn't very strong, so I'm going to
	 * add a port-based condition as well. Default port for OpenVPN
	 * is UDP 1194 */

	if (data->server_port == 1194 || data->client_port == 1194) {
                /* Just match the two-way stuff for now */
                if (match_openvpn_handshake(data->payload[0],
                                data->payload[1]))
                        return true;

         /*add 20201125 for one-way */
                if (data->payload_len[0] == 84 && MATCH(data->payload[0], 0x48, 0x00, ANY, ANY))
                        return true;
                if (data->payload_len[1] == 84 && MATCH(data->payload[1], 0x48, 0x00, ANY, ANY))
                        return true;

                if (((data->payload_len[0] != 0 && data->payload_len[1] == 0) &&
                        (match_tunnelbear_40(data->payload[0], data->payload_len[0]))) ||
                    match_tunnelbear_38(data->payload[0], data->payload_len[0]))
                        return true;

                if (((data->payload_len[1] != 0 && data->payload_len[0] == 0) &&
                        (match_tunnelbear_40(data->payload[0], data->payload_len[0]))) ||
                    match_tunnelbear_38(data->payload[0], data->payload_len[0]))
                        return true;
        }


        /* These are based on traffic seen involving TunnelBear hosts */
        if (match_tunnelbear_40(data->payload[0], data->payload_len[0])) {
                if (match_tunnelbear_38(data->payload[1], data->payload_len[1]))
                        return true;
        }

        if (match_tunnelbear_40(data->payload[1], data->payload_len[1])) {
                if (match_tunnelbear_38(data->payload[0], data->payload_len[0]))
                        return true;
        }


        /* Similar for Windscribe */
        if (data->server_port == 443 || data->client_port == 443) {
                if (match_wscribe_40(data->payload[0], data->payload_len[0])) {
                        if (match_wscribe_38(data->payload[1], data->payload_len[1]))
                                return true;
                }

                if (match_wscribe_40(data->payload[1], data->payload_len[1])) {
                        if (match_wscribe_38(data->payload[0], data->payload_len[0]))
                                return true;
                }
        }

	return false;
}

static lpi_module_t lpi_openvpn_udp = {
	LPI_PROTO_UDP_OPENVPN,
	LPI_CATEGORY_TUNNELLING,
	"OpenVPN_UDP",
	12,
	match_openvpn_udp
};

void register_openvpn_udp(LPIModuleMap *mod_map) {
	register_protocol(&lpi_openvpn_udp, mod_map);
}