Re: XDM Insecurity revisited

[mkp () SUNSITE AUC DK (Martin K. Petersen)]

> > > > > "Jochen" == Jochen Bauer <jtb () THEO2 PHYSIK UNI-STUTTGART DE> writes:

Jochen> However, this warning seemed to have little effect as (at
Jochen> least) Digital Unix 4.0E, SuSE Linux 6.1 and Red Hat Linux 6.0
Jochen> are still (1.5 years later) shipped with this default Xaccess
Jochen> file.

Same story for Solaris, HP/UX and (iirc) Irix...

Jochen> It is somehow ironic that e.g. SuSE now uses tcpwrappers by
Jochen> default on most TCP services in it's distribution and
Jochen> describes the use of tcpwrappers in the manual in a special
Jochen> chapter about security, but fails to close (or even mention)
Jochen> that way to circumvent login restrictions.

Incidentally, the Gnome Display Manager which is also included in Red
Hat 6.0 uses tcpwrappers for access control (Unfortunately it is
slightly broken wrt. XDMCP in the shipped version -- mea culpa).  GDM
also has an option to disallow root logins and makes extensive use of
PAM for authentication.

In general, I'd advise anyone running XDM or derivatives (like dtlogin
from CDE) to block UDP port 177 on their firewall. It's an extremely
good idea. Believe me...

--
Martin Kasper Petersen          BOFH, IC1&2, Aalborg University, DK