xauth failure when tunneling over ssh

[Pollywog]

On Tuesday 11 November 2008 21:27:38 Elliot Isaacson wrote:
> Hi,
>
> I've set up X11Forwarding on several linux servers before, but I've
> just wasted a day trying (unsuccessfully) to figure out why I can't
> get it working on freebsd (7.0-RELEASE GENERIC).
>
> I have not changed the defaults in the sshd_config file.
>
> One the client computer:
>
> $ xhost +
>
> $ ssh -Y 192.ip.of.server
> Warning: No xauth data; using fake authentication data for X11
> forwarding.
>
> /usr/local/bin/xauth:  creating new authority
> file /home/xxx/.Xauthority
> /usr/local/bin/xauth: (stdin):1:  bad display name "unix:10.0"
> in "remove" command
> /usr/local/bin/xauth: (stdin):2:  bad display name "unix:10.0"
> in "add" command
>
> [xxx@ ~] kcalc
> X11 connection rejected because of wrong authentication.
> kcalc: Fatal IO error: client killed
>
> [xxx@ ~] ls -a .Xauth*
> <no results>
>
> Now, when I go to the server and login directly, and do a startx,
> the x server starts fine, but there's still no .Xauthority file in
> the home directory. I find that odd.
>
> This also looks strange to me:
>
> [xxx@ ~] ps -aux | grep X
> root    1470  0.0  2.7 65456 13668  v0  S     4:01PM   0:01.24
> X :0 -auth /home/xxx/.serverauth.1451 (Xorg)
>
> [xxx@ ~] ls -a /home/xxx/.serverauth*
> <no results>
>
> How could it authenticate with a non-existent file?
>
> Any pointers in the right direction would be greatly appreciated.

I had the same problem when trying to SSH to the FreeBSD machines from Linux.
If I remember correctly, I had to make a change to ssh_config on the Linux side 
to get things to work:

Host *
  XAuthLocation /usr/bin/xauth

It might also help if you would post sshd_config on the FreeBSD side.