#FORMAT python
#! /usr/bin/env python

#
# WARNING: See dnsmasq --address=/#/1.2.3.4 before!!!!!
#

# Fake dns multithread

from SocketServer import *

FAKEADDRESS="111.111.111.111"
PORT=53 #udp

class DNSQuery:
  #da http://preachermm.blogspot.com/2006/04/servidor-fake-dns-en-python.html (single thread)
  def __init__(self, data):
    self.data=data
    self.dominio=''
    tipo = (ord(data[2]) >> 3) & 15   # Opcode bits
    if tipo == 0:                     # Standard query
      ini=12
      lon=ord(data[ini])
      while lon != 0:
        self.dominio+=data[ini+1:ini+lon+1]+'.'
        ini+=lon+1
        lon=ord(data[ini])

  def respuesta(self, ip):
    packet=''
    if self.dominio:
      packet+=self.data[:2] + "\x81\x80"
      packet+=self.data[4:6] + self.data[4:6] + '\x00\x00\x00\x00'   # Questions and Answers Counts
      packet+=self.data[12:]                                         # Original Domain Name Question
      packet+='\xc0\x0c'                                             # Pointer to domain name
      packet+='\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04'             # Response type, ttl and resource data length -> 4 bytes
      packet+=''.join(chr(int(x)) for x in ip.split('.'))            # 4bytes of IP
    return packet
#DNSQuery
    
class DNSRequestHandler (DatagramRequestHandler):
	def handle(self):
		DNSRequest=self.rfile.read()
		q=DNSQuery(DNSRequest)
 		DNSDatagram=q.respuesta(FAKEADDRESS)
  		self.wfile.write(DNSDatagram)
#DNSRequestHandler

#crea una classe di server udp threadizzato
class FakeDNSServer (ThreadingMixIn, UDPServer): pass

dummyDNS=FakeDNSServer(('',PORT),DNSRequestHandler)

#per prevenire attacchi, l'unico modo x fermare il server e' killarlo (SIGTERM, SIGKILL) o premere ctrl-C
going=True
while going:
	try:
		dummyDNS.serve_forever()
 	except KeyboardInterrupt:
 		going=False
	except:
		pass