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Date:      Thu, 28 Mar 2002 07:09:13 -0800
From:      Cy Schubert - CITS Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>
To:        David Pick <d.m.pick@qmul.ac.uk>
Cc:        Brett Glass <brett@lariat.org>, security@FreeBSD.ORG
Subject:   Re: Is FreeBSD susceptible to this vulnerability? 
Message-ID:  <200203281510.g2SFA4m66570@cwsys.cwsent.com>
In-Reply-To: Message from David Pick <d.m.pick@qmul.ac.uk>  of "Thu, 28 Mar 2002 14:58:11 GMT." <E16qbLv-0004xx-00@xi.css.qmw.ac.uk> 

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In message <E16qbLv-0004xx-00@xi.css.qmw.ac.uk>, David Pick writes:
> 
> > Apparently, several UNIX-like operating systems can be penetrated via 
> > XDMCP/UDP; see
> > 
> > http://www.procheckup.com/security_info/vuln_pr0208.html
> > 
> > Is FreeBSD vulnerable? What about the other BSDs?
> 
> (All the following is from reading the notice and having used
> XDM myself in the past; not from reading the code...)
> 
> The notice says it's an "information leakage" vulnerability that
> can leak information useful for otherwise unrelated brute-force
> attacks.
> 
> It's also more a matter of the default configurations for the
> XMDCP daemon rather than the code of the daemon.
> 
> The FreeBSD default configuratin *is* vulnerable but doesn't
> gratuitously leak information (for example by providing lists
> of valid users). So it's no more or less vulnerable than having
> an open listening "telnet" service. Or an open "finger" service.
> However, the notice is worthwhile because it points out that
> such leakage can happen via services that use UDP as well as
> services using TCP.

The default FreeBSD configuration, at least in the XFree86-4 port, 
ships with the following lines in Xaccess:

...
#*                                      #any host can get a login window
...
#*              CHOOSER BROADCAST       #any indirect host can get a 
chooser
..

This doesn't appear open to me (notice the lines have been commented 
out).


Regards,                         Phone:  (250)387-8437
Cy Schubert                        Fax:  (250)387-5766
Team Leader, Sun/Alpha Team      Email:  Cy.Schubert@osg.gov.bc.ca
Open Systems Group, CITS
Ministry of Management Services
Province of BC            
                    FreeBSD UNIX:  cy@FreeBSD.org




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