CCats/daemon/include/CovertChannel/TCPAppendChannel.hpp

#ifndef TCPAPPENDCHANNEL_H
#define TCPAPPENDCHANNEL_H

#include "CovertChannel.h"

#include "CovertProtocolBidirectional.hpp"

/**
 * @class TCPAppendChannel
 *
 * A CovertChannel which appends data to the TCP payload
 *
 * @param N number of bytes which can be used to transmit data
 * @param PASSIVE true - server only reacts to incoming channel | false - server initiates channel
 */
template <int N, bool PASSIVE> class TCPAppendChannel : public CovertChannel {
public:
	/**
	 * Sets up a CovertChannel.
	 *
	 * Creates a CovertChannel, sets the network interfaces for sniffing and sending and sets the filter.
	 *
	 * @param innerInterface name of the interface of the inner network
	 * @param outerInterface name of the interface of the outer network
	 * @param ownIP IP of this server
	 * @param targetIP IP of the target server
	 * @param targetPort Port of the target server
	 */
	TCPAppendChannel(const std::string &innerInterface, const std::string &outerInterface, const std::string &ownIP, const std::string &targetIP,
	                 const std::string &targetPort)
	    : CovertChannel(innerInterface, outerInterface,
	                    "(not (tcp and " + std::string(PASSIVE ? "src" : "dst") + " host " + targetIP + " and " + std::string(PASSIVE ? "src" : "dst") +
	                        " port " + targetPort + ")) and (not (dst host " + ownIP + "))",
	                    "(not (tcp and " + std::string(PASSIVE ? "dst" : "src") + " host " + targetIP + " and " + std::string(PASSIVE ? "dst" : "src") +
	                        " port " + targetPort + ")) and (not (dst host " + ownIP + "))",
	                    "tcp and " + std::string(PASSIVE ? "src" : "dst") + " host " + targetIP + " and " + std::string(PASSIVE ? "src" : "dst") + " port " +
	                        targetPort,
	                    "tcp and " + std::string(PASSIVE ? "dst" : "src") + " host " + targetIP + " and " + std::string(PASSIVE ? "dst" : "src") + " port " +
	                        targetPort) {}

	/**
	 * Destroys the CovertChannel.
	 */
	virtual ~TCPAppendChannel() {}

	/**
	 * Send a file over the covert channel.
	 *
	 * @param fileName name of the file in the file directory
	 * @return true - file will be sent | false - file was not accepted
	 */
	virtual bool sendFile(const std::string &fileName) {
		if constexpr (PASSIVE) {
			return false;
		} else {
			return protocol.sendFile(fileName);
		}
	}

protected:
	/**
	 * Handler for sniffed packets filterd to forward from the outer network.
	 *
	 * Handles incoming packets and forwards them.
	 *
	 * @param pdu sniffed packet
	 *
	 * @return false = stop loop | true = continue loop
	 */
	virtual bool handleChannelFromOuter(Tins::PDU &pdu) {
		Tins::TCP &tcp = pdu.rfind_pdu<Tins::TCP>();

		// get payload
		Tins::RawPDU *raw = tcp.find_pdu<Tins::RawPDU>();
		if (raw != nullptr) {
			Tins::RawPDU::payload_type &payload = raw->payload();

			// read data from payload
			std::size_t size = payload.size();
			uint8_t *data = &payload.front();
			data += size - N;

			protocol.receive(data);

			// resize payload
			payload.resize(size - N);
		}

		innerSender.send(pdu);

		return true;
	}

	/**
	 * Handler for sniffed packets filterd to forward from the inner network.
	 *
	 * Handles incoming packets and forwards them.
	 *
	 * @param pdu sniffed packet
	 *
	 * @return false = stop loop | true = continue loop
	 */
	virtual bool handleChannelFromInner(Tins::PDU &pdu) {
		Tins::TCP &tcp = pdu.rfind_pdu<Tins::TCP>();

		// get payload
		Tins::RawPDU *raw = tcp.find_pdu<Tins::RawPDU>();
		if (raw != nullptr) {
			Tins::RawPDU::payload_type &payload = raw->payload();

			// resize payload
			std::size_t size = payload.size();
			payload.resize(size + N);

			// write data in payload
			uint8_t *data = &payload.front();
			data += size;

			protocol.send(data);
		}

		outerSender.send(pdu);

		return true;
	}

	/**
	 * protocol used to transmit data
	 */
	CovertProtocolBidirectional<N, PASSIVE> protocol;
};

#endif