Welcome back, cyberwarriors!

Earlier, we wrote an article on the issues that cars have. These issues are still common and car ransomware might soon emerge, hitting not just individual cars but entire fleets as vehicles get more autonomous and packed with different features.

In light of that, we want to show you a tool that makes car hacking more approachable. It’s GearGoat. The tool was built to simulate a car’s internal network so you can play with it.

GearGoat

GearGoat is a car simulator developed by INE Labs. It lets you work with the internal communication network used by most modern vehicles (CAN bus). Every action generates CAN packets on a virtual interface. You can use cansniffer, candump and UDS scanners with GearGoat, just like with any vehicle.

In a real car, you’d connect a CAN adapter (CANable or Macchina M2) into the OBD-II port, located under the dashboard. This port is basically a gateway into the vehicle’s internal network. Your system will treat the adapter as a network interface (can0) and you can start capturing and sending CAN messages. When someone presses the brake or turns on the indicators, it generates messages that travel across the network.

Setting Up

GearGoat runs inside a Docker container, so it’s easy to deploy. Clone the repository and run the script:

kali > git clone https://github.com/ine-labs/GearGoat.git
kali > cd GearGoat
kali > sudo chmod +x initial_setup.sh
kali > sudo ./initial_setup.sh

Then you need to configure the virtual CAN interface (vcan0):

kali > sudo chmod +x vcan_setup.sh
kali > sudo ./vcan_setup.sh

On certain distros you might be missing kernel modules. Here’s how you install them:

kali > sudo apt-get install -y linux-modules-extra-$(uname -r)

It doesn’t always work on Kali Linux though. You can manually load the required modules and create the interface yourself:

kali > sudo modprobe vcan
kali > sudo ip link add dev vcan0 type vcan
kali > sudo ip link set up vcan0
kali > ip link show vcan0

Now everything should be ready. You can start GearGoat:

kali > sudo docker run --network="host" --privileged geargoat

The simulator will be hosted on http://localhost. There you’ll see different car functions. Each button on the interface generates CAN traffic.

Intercepting Traffic

While the simulator’s running, it continuously generates CAN traffic. To see this traffic, use cansniffer.

kali > cansniffer -c vcan0

The output can feel overwhelming. The tool keeps highlighting changing bytes dynamically. It’s very noisy when you’re trying to establish a baseline. You need a way to tell the tool what normal looks like. Press Shift + 3 + Enter multiple times and cansniffer will treat the current state as the baseline. It won’t highlight the background noise anymore, so you’ll only see the changes you make.

Once the baseline is set, you can start playing with the simulator. Click the Left Indicator button and you’ll notice a change in the CAN data.

The first byte of a frame changes and it’s tied to 0x188. That means this identifier controls the indicator state.

When you play with the speedometer, you’ll see a different pattern. The changes happen in the 4th and 5th bytes are associated with 0x244. The speed climbs gradually.

Repeat this with other controls and you’ll see how functions map on the CAN bus.

Sending Input

Now we know which messages control specific functions, so we can interact with them.

To control the indicators, we’ll send CAN frames using cansend:

kali > cansend vcan0 188#0100000000000000  # left
kali > cansend vcan0 188#0200000000000000  # right

These commands will turn on the left and right indicators. The CAN bus runs at high speed, so these changes can be hard to catch. We used the watch command to make it more visible:

kali > watch -n 0.1 "cansend vcan0 188#0200000000000000"

Working with speed gets slightly more complex. Earlier, we found the address (0x244) and that specific bytes that control the value. To set a speed, we need to convert miles per hour into the format the CAN message expects.

To simulate a speed of 50 miles per hour you send:

kali > cansend vcan0 244#0000001F6F

You can see the simulator accelerating. Use the formula V = round(mph / 0.6213751 * 100) to calculate the value, then convert it into hexadecimal using big-endian.

Capturing and Replaying Traffic

You can also capture and replay traffic. That way you can record a sequence of actions and reproduce them.

To capture traffic, you use candump with logging:

kali > candump -l vcan0 

It’ll record the CAN messages into a log file. Once captured, you can replay it:

kali > canplayer -I <log_file_name>.log

Summary

GearGoat can get you started with car hacking. You work with a simulated CAN bus to understand the communication patterns and message structure. It’s easy to set up and it’s not resource intensive, so it’ll run on pretty much any computer.

We also have our three-day Car Hacking training, showing you real attacks. It includes CAN protocol exploitation and the use of Software Defined Radio (SDR). There we show you how modern vehicles are actually compromised.

The post Automobile Hacking: Hacking with GearGoat first appeared on Hackers Arise.