/*
 * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
 * Please refer to the LICENSE.txt for licensing details.
 */
package ch.ethz.ssh2.channel;

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

import ch.ethz.ssh2.log.Logger;
import ch.ethz.ssh2.util.StringEncoder;

/**
 * RemoteX11AcceptThread.
 *
 * @author Christian Plattner
 * @version $Id: RemoteX11AcceptThread.java 119 2014-04-12 20:30:58Z dkocher@sudo.ch $
 */
public class RemoteX11AcceptThread extends Thread {
    private static final Logger log = Logger.getLogger(RemoteX11AcceptThread.class);

    Channel c;

    String remoteOriginatorAddress;
    int remoteOriginatorPort;

    Socket s;

    public RemoteX11AcceptThread(Channel c, String remoteOriginatorAddress, int remoteOriginatorPort) {
        this.c = c;
        this.remoteOriginatorAddress = remoteOriginatorAddress;
        this.remoteOriginatorPort = remoteOriginatorPort;
    }

    @Override
    public void run() {
        try {
            /* Send Open Confirmation */
            c.cm.sendOpenConfirmation(c);
            /* Read startup packet from client */
            OutputStream remote_os = c.getStdinStream();
            InputStream remote_is = c.getStdoutStream();
            /* The following code is based on the protocol description given in:
             * Scheifler/Gettys,
             * X Windows System: Core and Extension Protocols:
             * X Version 11, Releases 6 and 6.1 ISBN 1-55558-148-X
             * (from the ETH library - after being here for almost ten
             * years one of the few books I borrowed... sad but true =)
             */
            /*
             * Client startup:
             *
             * 1 0X42 MSB first/0x6c lSB first - byteorder
             * 1 - unused
             * 2 card16 - protocol-major-version
             * 2 card16 - protocol-minor-version
             * 2 n - lenght of authorization-protocol-name
             * 2 d - lenght of authorization-protocol-data
             * 2 - unused
             * string8 - authorization-protocol-name
             * p - unused, p=pad(n)
             * string8 - authorization-protocol-data
             * q - unused, q=pad(d)
             *
             * pad(X) = (4 - (X mod 4)) mod 4
             *
             * Server response:
             *
             * 1 (0 failed, 2 authenticate, 1 success)
             * ...
             *
             */
            /* Later on we will simply forward the first 6 header bytes to the "real" X11 server */
            byte[] header = new byte[6];

            if (remote_is.read(header) != 6)
                throw new IOException("Unexpected EOF on X11 startup!");

            if ((header[0] != 0x42) && (header[0] != 0x6c)) // 0x42 MSB first, 0x6C LSB first
                throw new IOException("Unknown endian format in X11 message!");

            /* Yes, I came up with this myself - shall I file an application for a patent? =) */
            int idxMSB = (header[0] == 0x42) ? 0 : 1;
            /* Read authorization data header */
            byte[] auth_buff = new byte[6];

            if (remote_is.read(auth_buff) != 6)
                throw new IOException("Unexpected EOF on X11 startup!");

            int authProtocolNameLength = ((auth_buff[idxMSB] & 0xff) << 8) | (auth_buff[1 - idxMSB] & 0xff);
            int authProtocolDataLength = ((auth_buff[2 + idxMSB] & 0xff) << 8) | (auth_buff[3 - idxMSB] & 0xff);

            if ((authProtocolNameLength > 256) || (authProtocolDataLength > 256))
                throw new IOException("Buggy X11 authorization data");

            int authProtocolNamePadding = ((4 - (authProtocolNameLength % 4)) % 4);
            int authProtocolDataPadding = ((4 - (authProtocolDataLength % 4)) % 4);
            byte[] authProtocolName = new byte[authProtocolNameLength];
            byte[] authProtocolData = new byte[authProtocolDataLength];
            byte[] paddingBuffer = new byte[4];

            if (remote_is.read(authProtocolName) != authProtocolNameLength)
                throw new IOException("Unexpected EOF on X11 startup! (authProtocolName)");

            if (remote_is.read(paddingBuffer, 0, authProtocolNamePadding) != authProtocolNamePadding)
                throw new IOException("Unexpected EOF on X11 startup! (authProtocolNamePadding)");

            if (remote_is.read(authProtocolData) != authProtocolDataLength)
                throw new IOException("Unexpected EOF on X11 startup! (authProtocolData)");

            if (remote_is.read(paddingBuffer, 0, authProtocolDataPadding) != authProtocolDataPadding)
                throw new IOException("Unexpected EOF on X11 startup! (authProtocolDataPadding)");

            if ("MIT-MAGIC-COOKIE-1".equals(StringEncoder.GetString(authProtocolName)) == false)
                throw new IOException("Unknown X11 authorization protocol!");

            if (authProtocolDataLength != 16)
                throw new IOException("Wrong data length for X11 authorization data!");

            StringBuilder tmp = new StringBuilder(32);

            for (int i = 0; i < authProtocolData.length; i++) {
                String digit2 = Integer.toHexString(authProtocolData[i] & 0xff);
                tmp.append((digit2.length() == 2) ? digit2 : "0" + digit2);
            }

            String hexEncodedFakeCookie = tmp.toString();

            /* Order is very important here - it may be that a certain x11 forwarding
             * gets disabled right in the moment when we check and register our connection
             * */

            synchronized (c) {
                /* Please read the comment in Channel.java */
                c.hexX11FakeCookie = hexEncodedFakeCookie;
            }

            /* Now check our fake cookie directory to see if we produced this cookie */
            X11ServerData sd = c.cm.checkX11Cookie(hexEncodedFakeCookie);

            if (sd == null)
                throw new IOException("Invalid X11 cookie received.");

            /* If the session which corresponds to this cookie is closed then we will
             * detect this: the session's close code will close all channels
             * with the session's assigned x11 fake cookie.
             */
            s = new Socket(sd.hostname, sd.port);
            OutputStream x11_os = s.getOutputStream();
            InputStream x11_is = s.getInputStream();
            /* Now we are sending the startup packet to the real X11 server */
            x11_os.write(header);

            if (sd.x11_magic_cookie == null) {
                byte[] emptyAuthData = new byte[6];
                /* empty auth data, hopefully you are connecting to localhost =) */
                x11_os.write(emptyAuthData);
            }
            else {
                if (sd.x11_magic_cookie.length != 16)
                    throw new IOException("The real X11 cookie has an invalid length!");

                /* send X11 cookie specified by client */
                x11_os.write(auth_buff);
                x11_os.write(authProtocolName); /* re-use */
                x11_os.write(paddingBuffer, 0, authProtocolNamePadding);
                x11_os.write(sd.x11_magic_cookie);
                x11_os.write(paddingBuffer, 0, authProtocolDataPadding);
            }

            x11_os.flush();
            /* Start forwarding traffic */
            StreamForwarder r2l = new StreamForwarder(c, null, null, remote_is, x11_os, "RemoteToX11");
            StreamForwarder l2r = new StreamForwarder(c, null, null, x11_is, remote_os, "X11ToRemote");
            /* No need to start two threads, one can be executed in the current thread */
            r2l.setDaemon(true);
            r2l.start();
            l2r.run();

            while (r2l.isAlive()) {
                try {
                    r2l.join();
                }
                catch (InterruptedException ignored) {
                }
            }

            /* If the channel is already closed, then this is a no-op */
            c.cm.closeChannel(c, "EOF on both X11 streams reached.", true);
            s.close();
        }
        catch (IOException e) {
            log.warning("IOException in X11 proxy code: " + e.getMessage());

            try {
                c.cm.closeChannel(c, e, true);
            }
            catch (IOException ignored) {
            }

            try {
                if (s != null)
                    s.close();
            }
            catch (IOException ignored) {
            }
        }
    }
}