Mandrake: 'kdm' Unauthorized access vulnerability
Posted by LinuxSecurity.com Team   
Mandrake By default, it allows XDMCP connections from any host, which can be used to obtain a login screen on your system remotely. This can be used to get a list of users on that host, as displayed by kdm.

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________________________________________________________________________

                Mandrake Linux Security Update Advisory
________________________________________________________________________

Package name:           kdm
Advisory ID:            MDKSA-2002:025
Date:                   March 20th, 2002
Affected versions:      7.1, 7.2, 8.0, Corporate Server 1.0.1
________________________________________________________________________

Problem Description:

 A problem was discovered with the default configuration of the kdm
 display manager in Mandrake Linux.  By default, it allows XDMCP
 connections from any host, which can be used to obtain a login screen
 on your system remotely.  This can be used to get a list of users on
 that host, as displayed by kdm.  It can also be used to circumvent
 access control mechanisms such as tcpwrappers and root login
 restrictions on the console and via remote.

Solution:

 To disable remote connections, edit the /etc/X11/xdm/Xaccess file and
 change the following two lines:

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

 to:

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


 Please note that Mandrake Linux 8.1 and 8.2 are not vulnerable to this
 as newer versions of kdm have a configuration option in the 
 /usr/share/config/kdm/kdmrc file which explicitly have XDMCP support
 disabled.

 Also please note that this is only valid if you are running kdm.
________________________________________________________________________

References:

  http://www.procheckup.com/security_info/vuln_pr0208.html
  http://www.kb.cert.org/vuls/id/634847
________________________________________________________________________

Updated Packages:

 There are no updated packages available.  Please refer to the Solution
 noted above for the fix.
________________________________________________________________________

Bug IDs fixed (see https://qa.mandrakesoft.com for more information):

________________________________________________________________________

To upgrade automatically, use MandrakeUpdate.  The verification of md5
checksums and GPG signatures is performed automatically for you.

If you want to upgrade manually, download the updated package from one 
of our FTP server mirrors and upgrade with "rpm -Fvh *.rpm".  A list of
FTP mirrors can be obtained from:

   http://www.mandrakesecure.net/en/ftp.php

Please verify the update prior to upgrading to ensure the integrity of
the downloaded package.  You can do this with the command:

  rpm --checksig 

All packages are signed by MandrakeSoft for security.  You can obtain
the GPG public key of the Mandrake Linux Security Team from:

  https://www.mandrakesecure.net/RPM-GPG-KEYS

Please be aware that sometimes it takes the mirrors a few hours to 
update.

You can view other update advisories for Mandrake Linux at:

   http://www.mandrakesecure.net/en/advisories/

MandrakeSoft has several security-related mailing list services that
anyone can subscribe to.  Information on these lists can be obtained by
visiting:

   http://www.mandrakesecure.net/en/mlist.php

If you want to report vulnerabilities, please contact

  security@linux-mandrake.com
________________________________________________________________________

Type Bits/KeyID     Date       User ID
pub  1024D/22458A98 2000-07-10 Linux Mandrake Security Team
  <security@linux-mandrake.com>


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