scanner.py

# -*- coding: utf-8 -*-

import socket

import os
import struct
from ctypes import *

import threading 
import time
from netaddr import IPNetwork,IPAddress

# ip addres of listened host
host = '192.168.91.134'

# the subnet of the target
subnet = "192.168.91.0/24"

# magic message to check icmp response
magic_message = "PYTHONRULES!"

# send udp data gram to subnet
def udp_sender(subnet, magic_message):
    time.sleep(5)
    sender = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    # SOCK_DGRAM: set to use udp
    
    for ip in IPNetwork(subnet):
        
        try:
            sender.sendto(magic_message, ("%s" % ip,65212))
        except:
            pass
        

# ip header
class IP(Structure):
    _fields_ = [
        ("ihl",        c_uint8, 4),
        ("version",    c_uint8, 4),
        ("tos",        c_uint8),
        ("len",        c_uint16),
        ("id",         c_uint16),
        ("offset",     c_uint16),
        ("ttl",        c_uint8),
        ("protocol_num", c_uint8),
        ("sum",        c_uint16),
        ("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):
        
        # mapping protocol constant value to name
        self.protocol_map = {1:"ICMP", 6:"TCP", 17:"UDP"}
        
        # transfer to readable ip address
        self.src_address = socket.inet_ntoa(struct.pack("<L", self.src))
        self.dst_address = socket.inet_ntoa(struct.pack("<L", self.dst))
        
        # transfer to readable protocol name
        try:
            self.protocol = self.protocol_map[self.protocol_num]
        except:
            self.protocol = str(self.protocol_num)

class ICMP(Structure):
    
    _fields_ = [
        ("type",      c_uint8),
        ("code",      c_uint8),
        ("checksum",  c_uint16),
        ("unused",    c_uint16),
        ("next_hop_mtu", c_uint16)
    ]
    
    def __new__(self, socket_buffer):
        return self.from_buffer_copy(socket_buffer)
    
    def __init__(self, socket_buffer):
        pass

            
# handle like last example
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))

# setting to add ip address of listened host to capture result
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

if os.name == "nt":
    sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)

# start to send packet
t = threading.Thread(target=udp_sender, args=(subnet, magic_message))
t.start()
    
try:
    while True:
        
        # read packets
        raw_buffer = sniffer.recvfrom(65565)[0]
        
        # create ip structure from first 20 bytes of buffer
        ip_header = IP(raw_buffer[0:20])
        
        # print detected host and protocol
        print "Protocol: %s %s -> %s" % (ip_header.protocol, ip_header.src_address, ip_header.dst_address)
        
        # handle if icmp
        if ip_header.protocol == "ICMP":
            
            # calculate the position of icmp packet
            offset = ip_header.ihl * 4
            buf = raw_buffer[offset:offset + sizeof(ICMP)]
            
            # create structure of icmp
            icmp_header = ICMP(buf)
            
            print "ICMP -> Type: %d Code: %d" % (icmp_header.type, icmp_header.code)
        
            # check if code and type are 3
            if icmp_header.code == 3 and icmp_header.type == 3:
            
                # check if subnet of the target
                if IPAddress(ip_header.src_address) in IPNetwork(subnet):
                
                    # check if magic message is included
                    if raw_buffer[len(raw_buffer)-len(magic_message):] == magic_message:
                        print "Host Up: %s" % ip_header.src_address
        
        
# handle Ctrl-C
except KeyboardInterrupt:
    
    # disable promisecasmode if windows
    if os.name == "nt":
        sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)