BlueHat v17 || KERNELFAULT: R00ting the Unexploitable using Hardware Fault Injection

Niek Timmers, Riscure B.V.
Cristofaro Mune, Independent Embedded Security Consultant

Fault injection attacks have been historically perceived as high-end attacks not available to most hackers. They used to require expensive tooling and a mysterious mix of skills which resulted them being out of reach for even the most skilled attackers. These days are over as low-cost fault injection tooling is changing the capabilities of the hacking masses at a rapid pace.

Historically, fault injection attacks are used to break cryptographic implementation (e.g. Differential Fault Analysis) or bypassing security checks like performed by a pin verification function. However, nothing prevents them to be used on richer systems like embedded devices or IoT devices. Fault injection attacks can be used to change the intended behavior of hardware and software, due, among the others, to corrupted memory reads and instructions execution.

In this talk we show that fault injection attacks and, more specifically, voltage fault injection, allow escalating privileges from an unprivileged context, in absence of logically exploitable software vulnerabilities. This is demonstrated using practical examples where the control flow of the Linux kernel is influenced in order to gain root privileges. All practical examples are performed on a fully patched Linux operating system, executed by a fast and feature rich System-on-Chip. A live demonstration of Fault Injection is part of the talk.