Buffer Overflow in KDE resLISa

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 in the 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.