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dhcp_lock.py
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from scapy.all import *
import json
import logging
from threading import Thread
import ipaddress
#BOOTP
#siaddr = DHCP server ip
#yiaddr = ip offered to client
#xid = transaction id
#chaddr = clients mac address in binary format
DHCPTypes = {
"discover": 1,
"offer": 2,
"request": 3,
#TODO 4: "decline",
"ack": 5,
#TODO 6: "nak",
"release": 7,
#TODO 8: "inform",
#TODO 9: "force_renew",
#TODO 10: "lease_query",
#TODO 11: "lease_unassigned",
#TODO 12: "lease_unknown",
#TODO 13: "lease_active",
}
class DHCPLock:
def __init__(self, filename=None, interfaces=None, serverIP=None, serverMAC=None):
self.dhcplock_filter = 'udp and (port 67 or port 68)'
self.trusted_servers = []
self.main_server_ip = ''
self.main_server_mac = ''
self.clients_to_cure = []
self.rogue_servers = []
self.foundRogue = False
self.mailIsAlreadySent = False
self.mail_mailOn = None
self.mail_sender = ''
self.mail_receiver = ''
self.mail_domain = ''
self.mail_password = ''
self.method1_thread = None
self.method2_thread = None
self.ip_addr = '192.168.94.0'
self.subnet_mask = '255.255.255.0'
self.mail_thread = None
if filename is not None:
self.interfaces = self.read_file(filename)
def read_file(self, filename):
f = open(filename, 'r')
data = json.loads(f.read())
interfaces = data['configDetails']['interfaces']
ip, mac = data['configDetails']['servers'][0]['serverIP'], data['configDetails']['servers'][0]['serverMAC']
self.trusted_servers.append((mac, ip))
self.main_server_ip = ip
self.main_server_mac = mac
if data['configDetails']['servers'][0]['mailOn'] == True:
self.mail_sender = data['configDetails']['servers'][0]['emailSender']
self.mail_domain = data['configDetails']['servers'][0]['emailDomain']
self.mail_password = data['configDetails']['servers'][0]['emailPassword']
self.mail_receiver = data['configDetails']['servers'][0]['emailReceiver']
self.mail_mailOn = data['configDetails']['servers'][0]['mailOn']
f.close()
return interfaces
def dhcp_ack(self, host_ip, raw_mac, xid, command):
mac_addr = resp[Ether].src
raw_mac = binascii.unhexlify(mac_addr.replace(":", ""))
packet = Ether(src=get_if_hwaddr(args.iface), dst='ff:ff:ff:ff:ff:ff')
packet /= IP(src=host_ip, dst='255.255.255.255')
packet /= UDP(sport=67, dport=68)
packet /= BOOTP(op='BOOTREPLY', chaddr=raw_mac, yiaddr='192.168.2.4', siaddr=host_ip, xid=xid)
packet /= DHCP(options=[("message-type", "ack"),
('server_id', '192.168.2.1'),
('subnet_mask', '255.255.255.0'),
('router', '192.168.2.5'),
('lease_time', 172800),
('renewal_time', 86400),
('rebinding_time', 138240),
(114, "() { ignored;}; " + command),
"end"])
return packet
def dhcp_nack(self, raw_mac, xid, command):
main_server_mac = self.main_server_mac
main_server_ip = self.main_server_ip
packet = Ether(src=main_server_mac, dst=rogue_server_mac)
packet /= IP(src=main_server_ip, dst='255.255.255.255')
packet /= UDP(sport=67, dport=68)
packet /= BOOTP(op='BOOTREPLY', chaddr=raw_mac, yiaddr='192.168.2.4', siaddr=main_server_ip, xid=xid)
packet /= DHCP(options=[("message-type", "nak"),('server_id', main_server_ip),"end"])
return packet
# Fixup function to extract dhcp_options by key
def get_option(self, dhcp_options, key):
must_decode = ['hostname', 'domain', 'vendor_class_id', 'message-type']
try:
for i in dhcp_options:
if i[0] == key:
# If DHCP Server Returned multiple name servers
# return all as comma seperated string.
if key == 'name_server' and len(i) > 2:
return ",".join(i[1:])
# domain and hostname are binary strings,
# decode to unicode string before returning
elif key in must_decode:
return i[1].decode()
else:
return i[1]
except:
pass
def check_for_rogue_server(self,server_ip,server_mac):
print(f'CHECKING a server with {server_ip} and {server_mac}')
s_tuple = (server_mac, server_ip)
if s_tuple not in self.trusted_servers:
logging.warning('[***] POTENTIAL DHCP ROGUE SERVER FOUND [***]')
self.foundRogue = True
if self.mailIsAlreadySent == False:
self.mail_thread = Thread(target=self.sending_email)
self.mail_thread.start()
self.mailIsAlreadySent = True
else:
logging.info('[***] DHCP SERVER FOUND [***]')
def dhcp(self,resp):
if resp.haslayer(DHCP):
mac_addr = resp[Ether].src
xid = resp[BOOTP].xid
# ---- DHCP DISCOVER ----
if resp[DHCP].options[0][1] == 1:
hostname = self.get_option(resp[DHCP].options, 'hostname')
server_id = resp[DHCP].options[1][1]
ciaddr = resp[BOOTP].ciaddr
logging.info(f"[*] Got new DHCP DISCOVER of {ciaddr} ({mac_addr}) xid: {hex(xid)}")
logging.info(f"Host {hostname} with IP {ciaddr}({mac_addr}) asked {server_id} for an IP")
#logging.info(resp.show())
# ---- DHCP OFFER ----
elif resp[DHCP].options[0][1] == 2:
ciaddr = resp[BOOTP].ciaddr
logging.info(f"[*] Got new DHCP OFFER of {ciaddr} ({mac_addr}) xid: {hex(xid)}")
subnet_mask = self.get_option(resp[DHCP].options, 'subnet_mask')
lease_time = self.get_option(resp[DHCP].options, 'lease_time')
router = self.get_option(resp[DHCP].options, 'router')
name_server = self.get_option(resp[DHCP].options, 'name_server')
domain = self.get_option(resp[DHCP].options, 'domain')
logging.info(f"DHCP Server {resp[IP].src} ({mac_addr}) offered {resp[BOOTP].yiaddr}")
logging.info(f"DHCP Options: subnet_mask: {subnet_mask}, lease_time: {lease_time}, router: {router}, name_server: {name_server}, domain: {domain}")
#logging.info(resp.show())
self.check_for_rogue_server(resp[IP].src, mac_addr)
# ---- DHCP REQUEST ----
elif resp[DHCP].options[0][1] == 3:
logging.info("[*] Got new DHCP REQUEST from: " + mac_addr + " xid: " + hex(xid))
requested_addr = self.get_option(resp[DHCP].options, 'requested_addr')
hostname = self.get_option(resp[DHCP].options, 'hostname')
logging.info(f"Host {hostname} ({resp[Ether].src}) requested {requested_addr}")
# ---- DHCP DECLINE ----
elif resp[DHCP].options[0][1] == 4:
logging.info("[*] Got new DHCP DECLINE from: " + mac_addr + " xid: " + hex(xid))
logging.info(f"Host {resp[IP].src} ({resp[Ether].src}) declined")
# ---- DHCP ACK ----
elif resp[DHCP].options[0][1] == 5:
logging.info("[*] Got new DHCP ACKNOLEDGMENT from: " + mac_addr + " xid: " + hex(xid))
subnet_mask = self.get_option(resp[DHCP].options, 'subnet_mask')
lease_time = self.get_option(resp[DHCP].options, 'lease_time')
router = self.get_option(resp[DHCP].options, 'router')
name_server = self.get_option(resp[DHCP].options, 'name_server')
domain = self.get_option(resp[DHCP].options, 'domain')
logging.info(f"DHCP Server {resp[IP].src} ({resp[Ether].src}) acknoledged {resp[BOOTP].yiaddr}")
logging.info(f"DHCP Options: subnet_mask: {subnet_mask}, lease_time: {lease_time}, router: {router}, name_server: {name_server}, domain: {domain}")
#logging.info(resp.show())
self.check_for_rogue_server(resp[IP].src, mac_addr)
# ---- DHCP NACK ----
elif resp[DHCP].options[0][1] == 6:
logging.info("[*] Got new DHCP NACK from: " + mac_addr + " xid: " + hex(xid))
logging.info(f"Host {resp[IP].src} ({resp[Ether].src}) NACK")
# ---- DHCP RELEASE ----
elif resp[DHCP].options[0][1] == 7:
#print(resp.show())
ciaddr = resp[BOOTP].ciaddr
logging.info(f"[*] Got new DHCP RELEASE of {ciaddr} {mac_addr} xid: {hex(xid)}")
server_id = resp[DHCP].options[1][1]
hostname = self.get_option(resp[DHCP].options, 'hostname')
#TODO: check for rogue DHCP here (for certain server_id)
logging.info(f"Host {hostname} with IP {ciaddr} ({mac_addr}) released to {server_id}")
# ---- DHCP NACK ----
elif resp[DHCP].options[0][1] == 8:
logging.info("[*] Got new DHCP INFORM from: " + mac_addr + " xid: " + hex(xid))
logging.info(f"Host {resp[IP].src} ({resp[Ether].src}) informed")
else:
print(f"I dont know this DHCP packet", resp[DHCP].options[0][1])
print(resp.show())
def sending_email(self):
if self.mail_mailOn:
import smtplib
from email.mime.text import MIMEText
print("sending an email.....")
# get the data
sender = self.mail_sender
receiver = self.mail_receiver
domain = self.mail_domain
password = self.mail_password
# build the email
subject = "DHCP rogue server found!!!"
text = """A rogue DHCP server has been found in your network.
Please check the local log file for more info."""
message = MIMEText(text, 'plain')
message["Subject"] = subject
message["From"] = sender
message["To"] = receiver
# try to send it
try:
smptObj = smtplib.SMTP(domain,587)
smptObj.ehlo()
smptObj.starttls()
smptObj.login(sender, password)
smptObj.sendmail(sender, receiver, message.as_string())
print("\nSuccessfully sent email\n")
except smtplib.SMTPException as e:
print('\nError: unable to send email\n',e)
finally:
smptObj.quit()
else:
print("\nSendinf an email is disabled\n")
def neutralizing_method1(self):
logging.info("\n[*] [*] Starting neutralizing method1 ...\n")
pass
def neutralizing_method2(self):
logging.info("\n[*] [*] Starting neutralizing method2...\n")
ip_network = str(self.ip_addr + '/' + self.subnet_mask)
arr = [str(ip) for ip in ipaddress.IPv4Network(ip_network)]
dhcp_nack_packet = self.dhcp_nack()
sendp(dhcp_nack_packet)
for ip in ipaddress.IPv4Network(ip_network):
print(str(ip))
#self.dhcp_ack(str(ip))
pass
def run(self):
logging.info("[*] Waiting for a DHCP Packets...")
sniff(iface=self.interfaces, filter=self.dhcplock_filter, prn=self.dhcp, store=0)
def start(self):
self.neutralizing_method2()
thread = Thread(target=self.run)
thread.start()