--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/trilead/ssh2/channel/RemoteX11AcceptThread.java	Thu May 22 10:41:19 2014 -0700
@@ -0,0 +1,205 @@
+
+package com.trilead.ssh2.channel;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.Socket;
+
+import com.trilead.ssh2.log.Logger;
+
+
+/**
+ * RemoteX11AcceptThread.
+ *
+ * @author Christian Plattner, plattner@trilead.com
+ * @version $Id: RemoteX11AcceptThread.java,v 1.2 2008/04/01 12:38:09 cplattne Exp $
+ */
+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;
+    }
+
+    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
+             */
+            /*
+             * 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(new String(authProtocolName, "ISO-8859-1")) == false)
+                throw new IOException("Unknown X11 authorization protocol!");
+
+            if (authProtocolDataLength != 16)
+                throw new IOException("Wrong data length for X11 authorization data!");
+
+            StringBuffer tmp = new StringBuffer(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, s, 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 e) {
+                }
+            }
+
+            /* 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.log(50, "IOException in X11 proxy code: " + e.getMessage());
+
+            try {
+                c.cm.closeChannel(c, "IOException in X11 proxy code (" + e.getMessage() + ")", true);
+            }
+            catch (IOException e1) {
+            }
+
+            try {
+                if (s != null)
+                    s.close();
+            }
+            catch (IOException e1) {
+            }
+        }
+    }
+}