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[SecuriWeb.2005.1] - Barracuda SPAM firewall advisory
From: Francois Harvey <fharvey () securiweb net>
Date: Wed, 31 Aug 2005 22:48:16 -0400

ID :                    2005.1
Product :          Barracuda Spam Firewall Appliance
Vendor :           Barracuda networks
Affected product : firmware <= 3.1.17
Class : Directory Traveral, Remote Execution, Password Retrieving
Remote :          yes
local :               na
Author :           Francois Harvey <fharvey at securiweb dot net>
Published date :   01/09/2005 (Initial Vendor contact 2005-06-14)
CVE :               CVE-MAP-NOMATCH
Solution :        Install Firmware 3.1.18
Reference URL : http://www.securiweb.net/wiki/Ressources/AvisDeSecurite/2005.1


Summary
======

A remote "Directory Traversal" and "Remote Execution" vulnerability exist in Barracuda Spam Firewall appliance from Barracuda Networks (barracudanetworks.com). In the script "/cgi-bin/img.pl", used to show graph, the value of the "f" (filename) parameters is not sanitized.

No authentification is required to exploit this remote vulnerability

Other vulnerabilies exist in the advanced utilities section but admin privilege is needed.
Affected product

   * Tested on Barracuda Spam Firewall firmware v.3.1.16 / v.3.1.17

Note: on the spyware edition img.pl is present but not executable
Note: on firmware 3.3.* the img.pl is img.cgi and they fixed the vulnerability

Impact
=====
   * Arbitrary file reading (as uid of the webserver)
   * Arbitrary file execution (as uid of the webserver)
   * Full reading of the system configuration
   * Audit of the Barracuda Spam firewall

Description
========
Vulnerability #1
---------------------------

As see below the img.pl script try to unlink the file after the reading. The webserver user (nobody) should not have a lot of delete permission but you have been warned.

In /cgi-bin/img.pl scripts

my $file_img="/tmp/".CGI::param('f');
open (IMG, $file_img) or die "Could not open image because: $!\n";
...
unlink ($file_img);

The "magic" perl open function can also be used to execute commands. If the string finish by | the script will execute the command and pipe the output to the IMG file descriptor.

file retreivial :
 f=../etc/passwd

remote execution :
 f=../bin/ls|

This vulnerability can be used to extract the admin password (see proof of concept)

Vulnerability #2
---------------------------

In the utility section, it's possible to call some process to troubleshoot the Barracuda. In the command list we can use Dig and Tcpdump ( /cgi-bin/dig_device.cgi and /cgi-bin/tcpdump_device.cgi). The input string is validate with a list of valid char but both dig and tcpdump allow filesystem operation with standard parameters.

Dig :

  The -f option makes dig  operate in batch mode by  reading  a  list  of
  lookup  requests to process from the file filename.

Tcpdump :

  -r     Read  packets  from file (which was created with the -w option).
             Standard input is used if file is ``-''.
  -w     Write  the  raw packets to file rather than parsing and printing
them out. They can later be printed with the -r option. Stan-
             dard output is used if file is ``-''.

As the use of some character is prohibited, we can only interact with the current directory.

Using -f <some_file_in_the_cgi-bin-directory> in the dig edit box allow the partial reading of source code. (grep DiG to reconstruct the code)

Using -r in tcpdump edit box allow only a reading of a valid pcap file but we can know if a file exist.

Using -w in tcpdump edit box should overwrite file in the cgi-bin directory. (not tested)

Proof of concept
===========

http://<BarracudaHost>:8000/cgi-bin/img.pl?f=../home/emailswitch/code/config/current.conf

   * The config is in /home/emailswitch/code/config/current.conf
   * The config key for the password is system_password
   * The password is in clear text (!!)
* The IP ACL for admin authentification is the config key : httpd_acl_ip_admin_address/httpd_acl_ip_admin_netmask * it's possible to desactivate for ~5 minutes the IP ACL (hint : look for the shell using by the user sa)

Solution
=====
Firmware update 3.1.18 fix this issue

Author
=====
Francois Harvey <fharvey at securiweb dot net>
Security Analyst
SecuriWeb inc.
www.securiweb.net

History
=====

2005-06-14 : Initial vendor contact
2005-06-14 : Initial feedback from Barracuda Networks
2005-07-* : Firmware 3.1.18 resolved this issue
2005-08-17 : Confirmation to disclose the vulnerability
2005-09-01 : Public disclosure



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