A covert channel using inter packet delays. More...

Inheritance diagram for whisper_library::TimingCovertChannel:

Public Member Functions
	TimingCovertChannel (function< void(string)> output, function< void(GenericPacket)> send)
	Constructor. More...

	~TimingCovertChannel ()

CovertChannel *	instance ()

void	sendMessage (string message)

void	receivePacket (GenericPacket &packet)

void	setArguments (string arguments)
	Gives arguments to the channel to configure the delays. More...

void	initialize ()

void	setOutput (function< void(string)> output)
	sets the output method More...

void	setSend (function< void(GenericPacket)> send)
	sets the methode used to send packets

string	name () const
	Returns a string with the name of the covert channel "Timing Covert Channel".

string	info () const
	Returns a string with basic information about the timing covert channel.

string	protocol () const
	Returns the protocol used by this covert channel (udp)

unsigned short	port () const
	Returns the used port (23)

string	id () const

Public Member Functions inherited from whisper_library::CovertChannel
	CovertChannel ()
	Creates a CovertChannel.

virtual	~CovertChannel ()
	Destructor. More...

virtual void	sendMessage (std::string message)=0
	sends a message More...

Private Member Functions
void	calculateTresholds ()

void	startTimeoutTimer ()

void	sendDelays (vector< unsigned int > delays)

Private Attributes
MorseCoder *	m_coder
	MorseCoder is used to encode messages as morse.

function< void(string)>	m_output
	callback function pointer that is used to return received messages as a string

function< void(GenericPacket)>	m_send
	function pointer that is used to send Udp Packets via the socket

chrono::time_point < chrono::system_clock >	m_receive_start
	Marks the time the last packet was received to measure inter-packet delays.

chrono::time_point < chrono::system_clock >	m_timeout_end
	Marks the time point at which the timeout ends. It is increased each time a packet is received.

atomic< bool >	m_timeout_changed
	signals 'startTimeoutTimer' that the timeout end point has changed.

vector< unsigned int >	m_received_delays
	stores the measured delays

atomic< bool >	m_receiving
	indicates, if the channel is currently receiving a message

unsigned int	m_timeout
	timeout in milliseconds after the last received message until the delays are interpreted

unsigned int	m_delay_short
	delay_short is used to encode a short signal (in milliseconds)

unsigned int	m_threshold_delay_short
	threshold between short and long delays

unsigned int	m_delay_long
	delay_long is used to encode a long signal (in milliseconds)

unsigned int	m_threshold_delay_long
	threshold between long and letter delays

unsigned int	m_delay_letter
	delay_letter is used to encode the end of a letter (in milliseconds)

unsigned int	m_threshold_delay_letter
	threshold between letter and space delays

unsigned int	m_delay_space
	delay_space is used to encode space between words (in milliseconds)

mutex	m_mutex_sending
	mutex to prevent different threads from sending simultaneously

Detailed Description

A covert channel using inter packet delays.

The TimingCovertChannel implements a covert channel, that uses inter-packet delays to transmit morse. The receiver measures the delays between incoming packets to decode the message. To use the channel, call 'sendMessage' with your message as a string. Received packets are given to 'receiveMessage' which returns the decoded message after a timeout to the callback function m_output.

Constructor & Destructor Documentation

whisper_library::TimingCovertChannel::TimingCovertChannel	(	function< void(string)>	output,
		function< void(GenericPacket)>	send
	)

inline

Constructor.

Parameters

output	function pointer that is called, when a complete message arrived. Its parameter is this message.
send	function pointer that is called to send a UdpPacket via the socket.

whisper_library::TimingCovertChannel::~TimingCovertChannel ( )

Destructor

Member Function Documentation

void whisper_library::TimingCovertChannel::calculateTresholds ( )

private

Calcules thresholds between the different intervals to compensate for transmitting delays.

string whisper_library::TimingCovertChannel::id ( ) const

virtual

Returns: the ID of the covert channel

Implements whisper_library::CovertChannel.

void whisper_library::TimingCovertChannel::initialize ( )

inlinevirtual

No initialisation needed, empty function

Implements whisper_library::CovertChannel.

CovertChannel * whisper_library::TimingCovertChannel::instance ( )

virtual

Returns: an instance of this covert channel

Implements whisper_library::CovertChannel.

void whisper_library::TimingCovertChannel::receivePacket ( GenericPacket & packet )

virtual

Has to be called when a packet is received, with the packet as the argument. After a timeout the callback m_output is called with the received message.

Parameters

packet packet that was received on network

Implements whisper_library::CovertChannel.

void whisper_library::TimingCovertChannel::sendDelays ( vector< unsigned int > delays )

private

Sends Udp packets using m_send with inter-packet delays given as the argument.

void whisper_library::TimingCovertChannel::sendMessage ( string message )

Sends a message using the timing channel.

Parameters

message Message that is send

void whisper_library::TimingCovertChannel::setArguments ( string arguments )

virtual

Gives arguments to the channel to configure the delays.

Available arguments: -set_timings [short] [long] [letter] [space] [short] [long] [letter] [space] are the delays used for morse encoding in milliseconds

Parameters

arguments string that is parsed for channel arguments

Implements whisper_library::CovertChannel.

void whisper_library::TimingCovertChannel::setOutput ( function< void(string)> output )

virtual

sets the output method

Parameters

output the method the covert channel uses to output the received messages

Implements whisper_library::CovertChannel.

void whisper_library::TimingCovertChannel::startTimeoutTimer ( )

private

Starts the timeout. If m_timeout_changed is false and m_timeout_end is in the past, it calls the callback function m_output.

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation