scanner.py

#!/usr/bin/python2.7
# sniffer with ip header decoding, icmp host identification
# Black Hat Python, with modification to adapt 32/64bit host


import socket
import os
import struct
from ctypes import *
import threading
import time
from netaddr import IPNetwork,IPAddress

#host to listen on
host='192.168.65.133'

#subnet to target
subnet='192.168.0.0/24'

# magic string we'll check ICMP responses for
magic_message = "Python rules!"

#this sprays out the UDP datagrams
def udp_sender(subnet,magic_message):
	time.sleep(5)
	sender = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
	
	for ip in IPNetwork(subnet):
		try:
			sender.sendto(magic_message,("%s" % ip,65212))
		except:
			pass

#our ip header
class IP(Structure):
    _fields_= [
        ("ihl",		c_ubyte, 4),
        ("version", 	c_ubyte, 4),
        ("tos", 	c_ubyte),
        ("len", 	c_ushort),
        ("id", 		c_ushort),
        ("offset", 	c_ushort),
        ("ttl", 	c_ubyte),
        ("protocol_num", c_ubyte),
        ("sum",		c_ushort),
        ("src", 	c_uint32),
        ("dst", 	c_uint32),
    ]
    
    def __new__(self, socket_buffer=None):
        return self.from_buffer_copy(socket_buffer)
    
    def __init__(self, socket_buffer=None):
        
        # map protocol constants to their names
        self.protocol_map = {1:"ICMP", 6:"TCP", 17:"UDP"}
        
        # human readable IP addresses
        self.src_address = socket.inet_ntoa(struct.pack("@I",self.src))
        self.dst_address = socket.inet_ntoa(struct.pack("@I",self.dst))

        # human readable protocol
        try:
            self.protocol = self.protocol_map[self.protocol_num]
        except:
            self.protocol = str(self.protocol_num)

class ICMP(Structure):

	_fields_= [
		("type",	c_ubyte),
		("code",	c_ubyte),
		("checksum",	c_ushort),
		("unused",	c_ushort),
		("next_hop_mtu", c_ushort)
		]
	def __new__(self, socket_buffer):
		return self.from_buffer_copy(socket_buffer)

	def __init__(self, socket_buffer):
		pass

#crete a rawsocket and bind it to the public iterface
if os.name == "nt":
    socket_protocol = socket.IPPROTO_IP
else:
    socket_protocol = socket.IPPROTO_ICMP

sniffer = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket_protocol)

sniffer.bind((host, 0))

# capture ip headers also
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

if os.name == "nt":
    sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
#start sending packets
t = threading.Thread(target=udp_sender,args=(subnet,magic_message))
t.start()


try:
    while True:
        
        #read in a packet
        raw_buffer = sniffer.recvfrom(65565)[0]
        
        #create an IP header from the first 20 bytes of the buffer
        ip_header = IP(raw_buffer)
        
        # print out the protocol that was detected and the hosts
        print "Protocol: %s %s -> %s" % (ip_header.protocol, ip_header.src_address, ip_header.dst_address)

	if ip_header.protocol == "ICMP":
		
		#calculate packet start
		offset = ip_header.ihl * 4
		buf = raw_buffer[offset:offset + sizeof(ICMP)]

		#create ICMP structure
		icmp_header = ICMP(buf)

		#print "ICMP -> Type: %d Code: %d" % (icmp_header.type, icmp_header.code)

		#now check for type 3 and code
		if icmp_header.code == 3 and icmp_header.type == 3:

			#make sure host is in our target subnet
			if IPAdress(ip_header.src_address) in IPNetwork(subnet):
				#make sure it has our magic message
				if raw_buffer[len(raw_buffer)-len(magic_message):] == magic_message:
					print "Host Up: %s" % ip_header.src_address


 #handle CTRL-C
except KeyboardInterrupt:
    
    #if we're using Windows, turn off promiscuous mode
    if os.name == "nt":
        sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)