InterceptingConnectionHandler.java

/*
 * This file is part of the OWASP Proxy, a free intercepting proxy library.
 * Copyright (C) 2008-2010 Rogan Dawes <rogan@dawes.za.net>
 * 
 * This library 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 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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 library; if not, write to:
 * The Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

package org.owasp.proxy.tcp;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.Socket;

import org.owasp.proxy.daemon.TargetedConnectionHandler;

/**
 * This {@link TargetedConnectionHandler} provides a framework for intercepting arbitrary TCP socket-based protocols.
 * 
 * It establishes a connection to the indicated target, then instantiates a pair of threads that read from the accepted
 * socket and the target socket, and notify the {@link StreamInterceptor} provided when data has been read, or the
 * connection terminated.
 * 
 * The basic sequence is as follows:
 * <ul>
 * <li>A pair of threads are created, one reading from the accepted socket, and the other reading from the socket
 * connected to the target.</li>
 * <li>The {@link StreamInterceptor#connected(StreamHandle, StreamHandle)} method is called, passing the
 * {@link StreamHandle}'s responsible for reading from the accepted socket, and from the target (in that order)</li>
 * <li>As each StreamHandle reads from its socket, it calls
 * {@link StreamInterceptor#received(StreamHandle, byte[], int, int)} with the data read. The StreamHandle serves as a
 * key to inform the StreamInterceptor which socket the data relates to.</li>
 * <li>If there is an error reading from the socket, the StreamHandle calls
 * {@link StreamInterceptor#readException(StreamHandle, IOException)}</li>
 * <li>Finally, {@link StreamInterceptor#inputClosed(StreamHandle)} is always called to allow the StreamInterceptor to
 * release any allocated resources.</li>
 * </ul>
 * 
 * Note that it is still possible to write data to the StreamHandle even after the input has been closed, to allow for
 * modification of the last packet sent.
 * 
 * @author rogan
 * 
 */
public class InterceptingConnectionHandler implements TargetedConnectionHandler {

    private StreamInterceptor<InetSocketAddress, InetSocketAddress> interceptor;

    public InterceptingConnectionHandler(
            StreamInterceptor<InetSocketAddress, InetSocketAddress> interceptor) {
        if (interceptor == null)
            throw new IllegalArgumentException("Interceptor may not be null");
        this.interceptor = interceptor;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.owasp.proxy.daemon.TargetedConnectionHandler#handleConnection(java .net.Socket,
     * java.net.InetSocketAddress)
     */
    public void handleConnection(final Socket client, InetSocketAddress target)
            throws IOException {
        InetSocketAddress clientLabel, serverLabel;
        InputStream ci, si;
        OutputStream so, co;
        StreamRelay<InetSocketAddress, InetSocketAddress> sr;

        final Socket server = new Socket(Proxy.NO_PROXY);
        server.connect(target);
        clientLabel = (InetSocketAddress) client.getRemoteSocketAddress();
        ci = client.getInputStream();
        co = client.getOutputStream();
        serverLabel = (InetSocketAddress) server.getRemoteSocketAddress();
        si = server.getInputStream();
        so = server.getOutputStream();
        sr = new StreamRelay<InetSocketAddress, InetSocketAddress>(interceptor,
                clientLabel, ci, co, serverLabel, si, so);
        Runnable cch = new Closer(server);
        Runnable sch = new Closer(client);
        sr.setCloseHandlers(cch, sch);
        sr.run();

    }

    private static class Closer implements Runnable {

        private Socket socket;

        public Closer(Socket socket) {
            this.socket = socket;
        }

        public void run() {
            try {
                if (!socket.isOutputShutdown())
                    socket.shutdownOutput();
            } catch (IOException e) {
                try {
                    if (!socket.isOutputShutdown())
                        socket.close();
                } catch (IOException ignore) {
                }
            }
        }
    }
}