com.mindbright.terminal

Class TerminalInputChaff

java.lang.Object

com.mindbright.terminal.TerminalInputChaff

All Implemented Interfaces:

TerminalInputListener, java.lang.Runnable

Direct Known Subclasses:

SSH2TerminalAdapterImpl, TelnetTerminalAdapter

public abstract class TerminalInputChaff
extends java.lang.Object
implements TerminalInputListener, java.lang.Runnable

Handles the sending of chaff to disguise the timing of key presses. Scientific research has shown that it may be possible to use keyboard timings to greatly reduce the work needed to perform a brute force password guessing attack. That is one can see the timing between the different keys as the user types them then this gives information about the password. To combat this MindTerm includes a technique called chaffing. When chaffic the client send a steady stream of data with fixed intervals, if there is no typed character to send a fake character is send instead. This kind of assumes an encrypted session since otherwise an attacker who can see timings coudl also see the password.

Chaffing means extra traffic so it should only be enabled when eeded. Fortunately it is often not needed since normally the terminal buffers the typed characters and sends them line-by line. The big exception is when sending passwords when the terminal is in non-echo mode.

Mote that this is not an issue for the initial password exchange in the SSH protocol but only applies when one sends passwords over a terminal session running over the encrypted link.

Constructor Summary

Constructors

Constructor and Description
TerminalInputChaff()

Method Summary

Methods

Modifier and Type	Method and Description
void	dispenseChaff() Kick chaff thread
protected boolean	isChaffActive() Tell if chaffing is active or not
void	run() The thread which actually sends the chaff or real data.
void	sendBreak() Classes derived from this class that are capable of sending a break signal can implement this.
protected abstract void	sendFakeChar() Send a fake character to the server.
protected abstract void	sendTypedChar(int c) Send a real typed character to the server.
void	signalTermTypeChanged(java.lang.String newTermType) This callback is only interesting for local input listeners such as LineReaderTerminal
void	startChaff() Start sending chaff
void	stopChaff() Stop sending chaff
void	typedChar(byte[] b) Receive a character typed by the user, the whole point of chaffing is to disguise the timing of calls to this function.
void	typedChar(char c) Receive a character typed by the user, the whole point of chaffing is to disguise the timing of calls to this function.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.mindbright.terminal.TerminalInputListener

sendBytes, sendBytesDirect, signalWindowChanged

Constructor Detail

TerminalInputChaff

public TerminalInputChaff()

Method Detail

startChaff

public void startChaff()

Start sending chaff

stopChaff

public void stopChaff()

Stop sending chaff

isChaffActive

protected boolean isChaffActive()

Tell if chaffing is active or not

Returns:

true if chaff is being sent

typedChar

public void typedChar(char c)

Receive a character typed by the user, the whole point of chaffing is to disguise the timing of calls to this function.

Specified by:

typedChar in interface TerminalInputListener

Parameters:

c - typed character

typedChar

public void typedChar(byte[] b)

Receive a character typed by the user, the whole point of chaffing is to disguise the timing of calls to this function.

Specified by:

typedChar in interface TerminalInputListener

Parameters:

b - byte array contained the encoded version of the character

signalTermTypeChanged

public void signalTermTypeChanged(java.lang.String newTermType)

This callback is only interesting for local input listeners such as LineReaderTerminal

Specified by:

signalTermTypeChanged in interface TerminalInputListener

Parameters:

newTermType - new terminal type to emulate

sendBreak

public void sendBreak()

Classes derived from this class that are capable of sending a break signal can implement this.

Specified by:

sendBreak in interface TerminalInputListener

run

public void run()

The thread which actually sends the chaff or real data.

Specified by:

run in interface java.lang.Runnable

dispenseChaff

public void dispenseChaff()

Kick chaff thread

sendTypedChar

protected abstract void sendTypedChar(int c)

Send a real typed character to the server.

sendFakeChar

protected abstract void sendFakeChar()

Send a fake character to the server.