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iDEFENSE Security Advisory 11.11.02:
http://www.idefense.com/advisory/11.11.02.txt
Buffer Overflow in KDE resLISa
November 11, 2002

I. BACKGROUND

KDE is a popular open source graphical desktop environment for Unix
workstations. Its kdenetwork module contains a LAN browsing
implementation known as LISa, which is used to identify CIFS and
other servers on the local network. LISa consists of two main
modules: "lisa", a network daemon, and "resLISa", a restricted
version of the lisa daemon created by Alexander Neundorf. LISa's lisa
module can be accessed in KDE using the URL type "lan://"; the
resLISa module can be accessed using the URL type "rlan://".

II. DESCRIPTION

Local exploitation of a buffer overflow within the resLISa module
could allow an attacker to gain elevated privileges. The overflow
exists in the parsing of the LOGNAME environment variable; an overly
long value will overwrite the instruction pointer, thereby allowing
an attacker to seize control of the executable. The following is a
snapshot of the exploit in action:

farmer@debian30:~$ ./reslisa_bof
farmer@debian30:~$ NetManager::prepare: listen failed
sh-2.05a$ id
uid=1000(farmer) gid=1000(farmer) groups=1000(farmer)

While the attacker's privileges have not been escalated, the
following shows the creation of a raw socket that is accessible by
the attacker:

farmer@debian30:~$ lsof | grep raw
sh 1413 farmer 3u raw 1432 00000000:0001->00000000:0000 st=07

farmer@debian30:~$ cd /proc/1413/fd/
farmer@debian30:/proc/1413/fd$ ls -l
total 0
lrwx------ 1 farmer farmer 64 Oct 11 02:47 0 -> /dev/pts/3
lrwx------ 1 farmer farmer 64 Oct 11 02:47 1 -> /dev/pts/3
lrwx------ 1 farmer farmer 64 Oct 11 02:47 2 -> /dev/pts/3
lrwx------ 1 farmer farmer 64 Oct 11 02:47 255 -> /dev/pts/3
lrwx------ 1 farmer farmer 64 Oct 11 02:47 3 -> socket:[1432]
l-wx------ 1 farmer farmer 64 Oct 11 02:47 4 -> /dev/null
lrwx------ 1 farmer farmer 64 Oct 11 02:47 5 -> socket:[1433]

III. ANALYSIS

Local attackers can use access to a raw socket to sniff network
traffic and generate malicious traffic (such as network scans, ARP
redirects, DNS poisoning). This can lead to further compromise of the
target system as well as other neighboring systems, depending on
network trust relationships.

IV. DETECTION

This vulnerability exists in all versions of resLISa included within
kdenetwork packages found in versions of KDE before 3.0.5. To
determine if a specific implementation is vulnerable issue the
following commands: 
 
$ LOGNAME=`perl -e 'print "A"x5000'` 
$ `which reslisa` -c . 
 
If the application exits, printing "signal caught: 11, exiting", then
it is vulnerable.  The above example was performed on resLISa version
0.1.1 which is packaged and distributed with Debian 3.0r0. 

V. VENDOR FIX

KDE 3.0.5 fixes this vulnerability, as well as a remotely exploitable
buffer overflow found in LISa by Olaf Kirch of SuSE Linux AG. More
information about the fix is available at
http://www.kde.org/info/security. Individual Unix vendors should be
providing updated KDE distributions on their appropriate download
sites.

Lisa 0.2.2, which also fixes these issues and compiles independent of
KDE, can be downloaded at
http://lisa-home.sourceforge.net/download.html.

VI. CVE INFORMATION

The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project
assigned the identification number CAN-2002-1247 to this issue.

VII. DISCLOSURE TIMELINE

10/02/2002  Issue disclosed to iDEFENSE
10/31/2002  Maintainer, Alexander Neundorf (neundorf@kde.org), 
    and Linux Security list (vendor-sec@lst.de) notified
10/31/2002  Response received from Alexander Neundorf
11/01/2002  iDEFENSE clients notified
11/11/2002  Coordinated public disclosure

VIII. CREDIT

Texonet (http://www.texonet.com) discovered this vulnerability.



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- -dave

David Endler, CISSP
Director, Technical Intelligence
iDEFENSE, Inc.
14151 Newbrook Drive
Suite 100
Chantilly, VA 20151
voice: 703-344-2632
fax: 703-961-1071

dendler@idefense.com
www.idefense.com

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