On 2009-11-16 18:04-0500 David A. Ventimiglia wrote:

> Hello,
>
> When I try to use the Tk driver, I get the error "X server insecure",
> which is pasted into the email below.  How do I get around this?  This
> is on Ubuntu Linux 9.10 "Karmic Koala", a Debian-package managed system.
> When I search for this error in Google, I find this wiki.tcl.tk page
> that was last updated in 2003:
>
> http://wiki.tcl.tk/1829
>
> There's some finger-wagging about insecure systems, and then it seems to
> recommend doing some minor surgery, removing hosts using this script:
>
> #!/bin/sh
> for host in 'xhost | sed 1d' ; do
>    echo removing $host from access control list
>    xhost -$host
> done
> echo removing general access from access control list
> xhost -
>
>
> While that works, it seems a little strange that I have to do this just
> to run a Tcl/Tk application, and it gives me pause if I consider
> building an "Extended WISH" that uses Tk, as described in the PLplot
> documentation.
>
> What does the PLplot community recommend in this situation?

Hi David:

Good question.

"man xhost" says it implements rudimentary X security.  Of course, that is
only the case if you use xhost to turn off all access (other than your own)
which the above script appears to do.  Because running the above script on
Ubuntu karmic apparently makes a difference, that means karmic has
configured xhost by default in a way that is blatently insecure (at least if
there is any network access to your system).

The above script makes no difference on my own Debian stable system, i.e.,
access control is turned on.  I don't recall fiddling with xhost (before
today) so I think this actually happened during Debian stable installation,
and I am surprised that apparently is not the case for Ubuntu karmic.

Anyhow, I am glad for your sake that you discovered the Ubuntu karmic xhost
security hole via your use of the PLplot Tk driver.  At least now you have
some rudimentary X security via the above script.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
__________________________

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