Strumenti network

Strumenti per trovare DHCP Server:

Script Python:

Usage: ./rogue_dhcp_check.py <interface_name> [timeout in seconds]

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	#!/usr/bin/env python3
	# This script sends a DHCP discover on the specified interface
	# then waits for the specified number of seconds (default: 5)
	# for replies from DHCP servers and prints the results.
	# Install dependencies:
	# sudo apt install python3-pip
	# sudo pip3 install scapy # do not use the one in Ubuntu apt (as of 18.04)
	# scapy API: https://scapy.readthedocs.io/en/latest/api/scapy.layers.html
	# TODO
	#
	# * What if a single DHCP server replies twice
	# or the rogue DHCP server is spoofing MAC addresses?
	# * Support plain BOOTP servers
	#
	import os
	import sys
	from scapy.all import *
	def die(err):
	print(err, file=sys.stderr)
	sys.exit(1)
	def usage(file=sys.stdout):
	print("Usage:", sys.argv[0], "<interface_name> [timeout in seconds]", file=file)
	if len(sys.argv) < 2 or len(sys.argv) > 3:
	usage(sys.stderr)
	sys.exit(1)
	iface = sys.argv[1]
	timeout = 5
	if len(sys.argv) == 3:
	try:
	timeout = int(sys.argv[2])
	except:
	usage(sys.stderr)
	sys.exit(1)
	if timeout < 1:
	timeout = 5
	if os.geteuid() != 0:
	die("You must be root to send DHCP packets")
	conf.checkIPaddr = False
	try:
	fam, hw = get_if_raw_hwaddr(iface)
	except OSError as e:
	die(e)
	dhcp_discover = Ether(dst="ff:ff:ff:ff:ff:ff") / IP(src="0.0.0.0", dst="255.255.255.255") / UDP(sport=68, dport=67) / BOOTP(chaddr=hw) / DHCP(options=[("message-type","discover"), "end"])
	print("Sending DHCP Discover packet on interface", iface)
	print("Waiting", timeout, "seconds for reply")
	ans, unans = srp(dhcp_discover, multi=True, timeout=timeout)
	dhcp_servers = {}
	for snd, rcv in ans:
	# We only care about message-type == 2
	# a.k.a. DHCP Offers
	is_offer = False
	for opt in rcv.payload.payload.payload.payload.options:
	if opt[0] == 'message-type':
	if opt[1] == 2:
	is_offer = True
	if not is_offer:
	continue
	# rcv.fields: list fields
	# rcv.payload: the decoded payload
	if not rcv.src in dhcp_servers:
	dhcp_servers[rcv.src] = {'MAC': rcv.src, 'IP': rcv.payload.src, 'offer': rcv.payload.payload.payload.yiaddr, 'options': rcv.payload.payload.payload.payload.options}
	print()
	print("Received", len(ans), "replies from", len(dhcp_servers), "different (based on MAC address) DHCP server(s)")
	print()
	if len(dhcp_servers) > 1:
	print("WARNING: Looks like there might be more than one DHCP server on your network")
	print()
	for mac in dhcp_servers:
	server = dhcp_servers[mac]
	print("DHCP server", mac)
	print(" Server IP:", server['IP'])
	print(" Offer IP:", server['offer'])
	print(" Options:")
	for opt in server['options']:
	if opt[0] == 'message-type':
	print(' message-type:', DHCPTypes[opt[1]])
	else:
	print(' ' + str(opt[0])+':', opt[1])
	print()