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/**
 * Copyright 2003-2016 SSHTOOLS Limited. All Rights Reserved.
 *
 * For product documentation visit https://www.sshtools.com/
 *
 * This file is part of J2SSH Maverick.
 *
 * J2SSH Maverick 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 3 of the License, or
 * (at your option) any later version.
 *
 * J2SSH Maverick 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 J2SSH Maverick.  If not, see .
 */
package com.sshtools.ssh2;

import java.io.IOException;

import com.sshtools.ssh.SshException;
import com.sshtools.ssh.SshIOException;
import com.sshtools.ssh.SshTransport;
import com.sshtools.ssh.SshTunnel;
import com.sshtools.ssh.message.SshChannelMessage;

/**
 * 
 * @author Lee David Painter
 */
class Ssh2ForwardingChannel extends Ssh2Channel implements SshTunnel {

	public static final String X11_FORWARDING_CHANNEL = "x11";
	public static final String LOCAL_FORWARDING_CHANNEL = "direct-tcpip";
	public static final String REMOTE_FORWARDING_CHANNEL = "forwarded-tcpip";

	protected final static String X11AUTH_PROTO = "MIT-MAGIC-COOKIE-1";
	SshTransport transport;
	String host;
	int port;
	String listeningAddress;
	int listeningPort;
	String originatingHost;
	int originatingPort;

	byte[] buf = new byte[1024];
	boolean hasSpoofedCookie = false;
	int idx = 0;
	int requiredLength = 12; // header len
	int protocolLength;
	int cookieLength;

	/**
	 * @param name
	 * @param windowsize
	 * @param packetsize
	 */
	public Ssh2ForwardingChannel(String name, int remotewindow,
			int remotepacket, String host, int port, String listeningAddress,
			int listeningPort, String originatingHost, int originatingPort,
			SshTransport transport) {
		super(name, remotewindow, remotepacket);
		this.transport = transport;
		this.host = host;
		this.port = port;
		this.listeningAddress = listeningAddress;
		this.listeningPort = listeningPort;
		this.originatingHost = originatingHost;
		this.originatingPort = originatingPort;

	}

	public String getHost() {
		return host;
	}

	public String getConnectedHost() {
		return getHost();
	}

	public int getPort() {
		return port;
	}

	public String getOriginatingHost() {
		return originatingHost;
	}

	public int getOriginatingPort() {
		return originatingPort;
	}

	public String getListeningAddress() {
		return listeningAddress;
	}

	public int getListeningPort() {
		return listeningPort;
	}

	public boolean isLocal() {
		return getName().equals(Ssh2ForwardingChannel.LOCAL_FORWARDING_CHANNEL);
	}

	public boolean isX11() {
		return getName().equals(Ssh2ForwardingChannel.X11_FORWARDING_CHANNEL);
	}

	public SshTransport getTransport() {
		return transport;
	}

	public boolean isLocalEOF() {
		return isLocalEOF;
	}

	public boolean isRemoteEOF() {
		return isRemoteEOF;
	}

	public SshTransport duplicate() throws IOException {
		throw new SshIOException(
				new SshException("SSH tunnels cannot be duplicated!",
						SshException.BAD_API_USAGE));
	}

	public void close() {

		// DEBUG START
		/*
		 * System.out.println(getName() + " id=" + channelid + " rid=" +
		 * remoteid + " CLOSING localwindow=" + localwindow.available() +
		 * " remotewindow=" + remotewindow.available());
		 */
		// DEBUG END
		super.close();
	}

	protected void processStandardData(int len, SshChannelMessage msg)
			throws SshException {

		// System.out.println(getName() + " id=" + channelid + " rid=" +
		// remoteid + " localwindow=" + localwindow.available() +
		// " remotewindow=" + remotewindow.available());

		if (getName().equals(X11_FORWARDING_CHANNEL)) {
			if (!hasSpoofedCookie) {
				int n;

				if (idx < 12) {
					n = readMore(msg);
					len -= n;
					if (requiredLength == 0) {
						if (buf[0] == 0x42) {
							protocolLength = ((buf[6] & 0xff) << 8)
									| (buf[7] & 0xff);
							cookieLength = ((buf[8] & 0xff) << 8)
									| (buf[9] & 0xff);
						} else if (buf[0] == 0x6c) {
							protocolLength = ((buf[7] & 0xff) << 8)
									| (buf[6] & 0xff);
							cookieLength = ((buf[9] & 0xff) << 8)
									| (buf[8] & 0xff);
						} else {
							close();
							throw new SshException(
									"Corrupt X11 authentication packet",
									SshException.CHANNEL_FAILURE);
						}
						requiredLength = (protocolLength + 0x03) & ~0x03;
						requiredLength += (cookieLength + 0x03) & ~0x03;
						if (requiredLength + idx > buf.length) {
							close();
							throw new SshException(
									"Corrupt X11 authentication packet",
									SshException.CHANNEL_FAILURE);
						}
						if (requiredLength == 0) {
							close();
							throw new SshException(
									"X11 authentication cookie not found",
									SshException.CHANNEL_FAILURE);
						}
					}
				}

				// Read payload of authentication packet
				//
				if (len > 0) {
					n = readMore(msg);
					len -= n;
					if (requiredLength == 0) {
						byte[] fakeCookie = connection.getContext()
								.getX11AuthenticationCookie();
						String protoStr = new String(buf, 12, protocolLength);
						byte[] recCookie = new byte[fakeCookie.length];

						protocolLength = ((protocolLength + 0x03) & ~0x03);

						System.arraycopy(buf, 12 + protocolLength, recCookie,
								0, fakeCookie.length);
						if (!X11AUTH_PROTO.equals(protoStr)
								|| !compareCookies(fakeCookie, recCookie,
										fakeCookie.length)) {
							close();
							throw new SshException("Incorrect X11 cookie",
									SshException.CHANNEL_FAILURE);
						}
						byte[] realCookie = connection.getContext()
								.getX11RealCookie();
						if (realCookie.length != cookieLength) {
							throw new SshException("Invalid X11 cookie",
									SshException.CHANNEL_FAILURE);
						}
						System.arraycopy(realCookie, 0, buf,
								12 + protocolLength, realCookie.length);
						hasSpoofedCookie = true;
						super.processStandardData(len, msg);
						buf = null;
					}
				}

				if (!hasSpoofedCookie || len == 0) {
					return;
				}
			}

		}

		super.processStandardData(len, msg);

	}

	private boolean compareCookies(byte[] src, byte[] dst, int len) {
		int i = 0;
		for (; i < len; i++) {
			if (src[i] != dst[i]) {
				break;
			}
		}
		return i == len;
	}

	private int readMore(SshChannelMessage msg) {
		int len = msg.available();
		if (len > requiredLength) {
			msg.read(buf, idx, requiredLength);
			idx += requiredLength;
			len = requiredLength;
			requiredLength = 0;
		} else {
			msg.read(buf, idx, len);
			idx += len;
			requiredLength -= len;
		}
		return len;
	}

}