Xlib: connection to "sr1-ubur-20:34.0" refused by server

[Ethan Mallove]

On Fri, Oct/23/2009 08:58:19AM, Alan Coopersmith wrote:
> Ethan Mallove wrote:
> > Hello,
> > 
> > It seems I suddenly can not access my own DISPLAY. All X applications
> > now error out with the following, e.g.,
> > 
> >  $ xterm
> >  Xlib: connection to "sr1-ubur-20:34.0" refused by server
> >  Xlib: No protocol specified
> >  xterm Xt error: Can't open display: sr1-ubur-20:34.0
> > 
> > Is there an xauth command that can get X working for me again?
> 
> Check your $XAUTHORITY & $HOME environment variables - those control
> where libX11 looks for the cookies for authentication.
> ($HOME/.xauthority is the default if $XAUTHORITY is not set)
> 
> If those are set correctly and the cookie for your display is gone,
> you would have to know the original magic cookie for the display in
> order to re-add it with xauth, there is no "crack the display
> security and recover my cookie" option.
> 
> There's two copies made at session startup - one in your $XAUTHORITY
> and one in a system directory that differs by display manager (gdm,
> xdm, kdm, dtlogin, startx, etc.) that's passed to the X server started
> (the -auth /path/to/file you can see in the arguments when running ps)
> and is usually only readable by root.  Authentication works by comparing
> the one your client reads from the authority file and sends to the server
> with the one the server read from it's copy of the file at startup.
> 
> I suppose it might be possible to dig through the memory of currently
> connected clients with a debugger to find the cookie they used, but
> I've never tried that and don't know how easy it would be.
> 
> If this is a recurring problem, things you could do when starting a
> new session to protect against it in the future:
>  - keep a backup of your .xauthority so you can recover the cookie
>    if it gets overwritten
>  - run 'xhost +si:localuser:ethan' (or whatever username you use)
>    so that local connections from that uid are always accepted,
>    without needing a cookie.

The issue has been happening about once or twice a month, so I
anticipate it will happen again. I have backed up my ~/.Xauthority
file. When the problem reoccurs, I will do the following:

  $ cp ~/.Xauthority.backup ~/.Xauthority

Many thanks!

-Ethan

> 
> -- 
> 	-Alan Coopersmith-           alan.coopersmith at sun.com
> 	 Sun Microsystems, Inc. - X Window System Engineering
> 
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