Cascade a X11 connection from a remote computer within an internal network to a SSH Xforwarding connection to an outside computer

Problem:  Cascade a X11 connection from a remote computer within an internal network to a SSH Xforwarding connection without using ssh for the last ‘hop’.


                                                                   Firewall
Home Computer           SSH                              |                                telnet
  Cygwin                ---------------------------------------à | Linux Box ---------------------------------à Sun Box
                                Only port 8080 open          |                             all ports open


I have a VPN that connects my home computer to a corporate network.  The VPN blocks most ports and I wish to use X11 X windows from within the network.  I am attempting to use SSH to tunnel the X11 connection from within the network to my Cygwin home computer.  The inner computer on the internal network does not allow SSH – thus I can not properly cascade SSH connections to allow X11 forwarding.  The internal network is secure so I am not concerned with security.  I have read every newsgroup article (and man page) I can get my hands on – but have not figured out the misconfiguration after a night of searching – probably a stupid oversight.

I am essentially looking to have any computer within the internal network be able to send an Xwindow to my home cygwin.

Thus – I need to use SSH to go from my home cygwin to the Linux box and telnet (or rlogin) to go from the Linux box to the sun box.  I have admin rights to the cygwin and the Linux box.  I do not have admin rights to the sun box.

Cygwin:   My ~/.ssh/config config file contains
      ForwardX11 yes

Linux: My sshd_config file contains
           X11Forwarding yes
          GatewayPorts yes
          X11DisplayOffset 10


Cygwin:  > ssh -X -l myuserid -p 8080 linux.myhost.com
      
Linux:      Warning: No xauth data; using fake authentication data for X11 forwarding.
      [should this output concern me?  I have xhost + enabled (I know it is bad practice but the VPN provides needed security]

Linux:      > xterm &
      [the xterm window appears as desired on cygwin]

Linux:   > echo $DISPLAY
      localhost:10.0
Linux:   > xhost +
      [temporary measure to reduce xauth issues]

Linux:   > telnet sun.myhost.com

Sun:      > export DISPLAY=linux.myhost.com:10.0
Sun:      > xterm &

Cannot connect to X server linux:10.
Check the DISPLAY environment variable or use `-d'.
Also use the `xhost' program to verify that it is set to permit
connections from your machine.

Sun:      > export DISPLAY=linux.myhost.com: 0.0
Sun:      > xterm &
[The xterm appears on my local sun box without problem]


A number of newsgroup post I saw referred to the need for a proper xauth config.  From my linux box I tried

Linux:      xauth list $DISPLAY
      [it was suggested that I copy the output to SUN’s .Xauthority file – however, the output to this command was blank]

      xauth list
            linux/unix:0  MIT-MAGIC-COOKIE-1  a03875840a61adf8970ba9cba7693271
                                localhost.localdomain/unix:0  MIT-MAGIC-COOKIE-1  a03875840a61adf8970ba9cba7693271
                                linux.myhost.com:0  MIT-MAGIC-COOKIE-1  a03875840a61adf8970ba9cba7693271
                                linux.myhost.com:0  MIT-MAGIC-COOKIE-1  a03875840a61adf8970ba9cba7693271
                                linux.myhost.com:0  MIT-MAGIC-COOKIE-1  a03875840a61adf8970ba9cba7693271
                                linux/unix:10  MIT-MAGIC-COOKIE-1  a03875840a61adf8970ba9cba7693271

      I copied the .Xauthority file from linux to sun.  I also tried the xauth add methods without avail.

This did not help.  Help is much appreciated.

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