MixPlugIn.java

/*******************************************************************************
 * gMix open source project - https://svs.informatik.uni-hamburg.de/gmix/
 * Copyright (C) 2014  SVS
 *
 * This program is free software: you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation, either version 3 of the License, or 
 * (at your option) any later version.
 *  
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License 
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *******************************************************************************/
package userGeneratedContent.testbedPlugIns.layerPlugIns.layer3outputStrategy.cottrellRandomDelay_v0_001;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Timer;
import java.util.TimerTask;

import staticContent.framework.controller.Implementation;
import staticContent.framework.interfaces.Layer3OutputStrategyMix;
import staticContent.framework.message.MixMessage;
import staticContent.framework.message.Reply;
import staticContent.framework.message.Request;
import staticContent.framework.userDatabase.User;


//Cottrell 1995 ("Mixmaster & Remailer Attacks")
//delays incoming messages randomly
public class MixPlugIn extends Implementation implements Layer3OutputStrategyMix {

	private static SecureRandom secureRandom;
	private Timer requestTimer = new Timer();
	private Timer replyTimer = new Timer();
	private int maxDelay;
	
	
	@Override
	public void constructor() {
		try {
			MixPlugIn.secureRandom = SecureRandom.getInstance(settings.getProperty("COTTRELL_RANDOM_DELAY_PRNG_ALGORITHM"));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
			throw new RuntimeException("could not init secureRandom"); 
		}
		this.maxDelay = settings.getPropertyAsInt("COTTRELL_RANDOM_DELAY_MAX_DELAY");
	}
	
	
	@Override
	public void initialize() {
		// no need to do anything
	}

	
	@Override
	public void begin() {
		// no need to do anything
	}

	
	@Override
	public void addRequest(Request request) {
		synchronized (requestTimer) {
			requestTimer.schedule(new SendMessageTask(request), getRandomDelay());
		}
	}

	
	@Override
	public void addReply(Reply reply) {
		synchronized (replyTimer) {
			replyTimer.schedule(new SendMessageTask(reply), getRandomDelay());
		}
	}

	
	private int getRandomDelay() {
		return secureRandom.nextInt(maxDelay+1);
	}
	
	
	private final class SendMessageTask extends TimerTask {

		private Request request;
		private Reply reply;
		private boolean isRequest;
		
		
		protected SendMessageTask(Request request) {
			this.request = request;
			this.isRequest = true;
		}
		
		
		protected SendMessageTask(Reply reply) {
			this.reply = reply;
			this.isRequest = false;
		}
		
		
		@Override 
		public void run() {
			if (isRequest) {
				synchronized (requestTimer) {
					anonNode.putOutRequest(request);
				}
			} else {
				synchronized (replyTimer) {
					anonNode.putOutReply(reply);
				}
			}
			
		}
			
	}

	
	@Override
	public int getMaxSizeOfNextWrite() {
		return super.recodingLayerMix.getMaxSizeOfNextReply();
	}


	@Override
	public int getMaxSizeOfNextRead() {
		return super.recodingLayerMix.getMaxSizeOfNextRequest();
	}


	@Override
	public void write(User user, byte[] data) {
		Reply reply = MixMessage.getInstanceReply(data, user); 
		reply.isFirstReplyHop = true;
		transportLayerMix.addLayer4Header(reply);
		anonNode.forwardToLayer2(reply);
	}
	
}