CANSPY: Auditing CAN Devices

Architecture and Background

In the past few years, several tools have been released allowing hobbyists to connect to CAN buses found in cars. This is welcomed as the CAN protocol is becoming the backbone for embedded computers found in smart cars. Its use is now even spreading outside the car through the OBD-II connector: usage-based policies from insurance companies, air-pollution control from law enforcement or engine diagnostics from smartphones for instance. Nonetheless, these tools will do no more than what professional tools from automobile manufacturers can do.

Vulnerability Analysis

In fact, they will do less as they do not have knowledge of upper-layer protocols. Security auditors are used to deal with this kind of situation: they reverse-engineer protocols before implementing them on top of their tool of choice. However, to be efficient at this, they need more than just being able to listen to or interact with what they are auditing. Precisely, they need to be able to intercept communications and block them, forward them or modify them on the fly.

Exploitation and Demonstrations

This is why, for example, a framework such as Burp Suite is popular when it comes to auditing web applications. In this paper, we present CANSPY, a framework giving security auditors such capabilities when auditing CAN devices. Not only can it block, forward or modify CAN frames on the fly, it can do so autonomously with a set of rules or interactively using Ethernet and a packet manipulation framework such as Scapy. It is also worth noting that it was designed to be cheap and easy to build as it is mostly made of inexpensive COTS.

Remediation and Defensive Strategies

Last but not least, we demonstrate its versatility by turning around a security issue usually considered when it comes to cars: instead of auditing an electronic control unit (ECU) through the OBD-II connector, we are going to partially emulate ECUs in order to audit a device that connects to this very connector. Jonathan-Christofer Demay, PhD is the current penetration testing team leader at AIRBUS Defense and Space. As a former academic researcher, he has been working on IDS bypassing, intrusion detection and general network security. Now a consultant for various key industries and government bodies, he is working on incident response, penetration testing and social engineering. Arnold Lebrun is a command and control engineer currently working at AIRBUS Defense and Space. He is focusing on security issues for several projects in the aerospace industry and related areas such as radioactive waste disposal facilities or large telescopes. He also supports the penetration testing team for perimeters that include ICS infrastructures or embedded electronics.