WooKey: USB Devices Strike Back — Arnauld Michelizza, Jérémy Lefaure, Mathieu Renard, Philippe Thierry, Philippe Trebuchet, Ryad Benadjila
Date : 13 juin 2018 à 17:15 — 30 min.
The USB bus has been a growing subject of research in recent years. In particular, securing the USB stack (and hence the USB hosts and devices) started to draw interest from the academic community since major exploitable flaws have been revealed by the BadUSB threat.
The work presented in this paper takes place in the design initiatives that have emerged to thwart such attacks. While some proposals have focused on the host side by enhancing the Operating System's USB sub-module robustness, or by adding a proxy between the host and the device, we have chosen to focus our efforts on the device side.
More specifically, our work presents the WooKey platform: a custom STM32-based USB thumb drive with mass storage capabilities designed for user data encryption and protection, with a full-fledged set of in-depth security defenses. The device embeds a firmware with a secure DFU (Device Firmware Update) implementation featuring up-to-date cryptography, and uses an extractable authentication token. The runtime software security is built upon EwoK: a custom microkernel implementation designed with advanced security paradigms in mind, such as memory confinement using the MPU (Memory Protection Unit) and the integration of safe languages and formal methods for very sensitive modules. This microkernel comes along with MosEslie: a versatile and modular SDK that has been developed to easily integrate user applications in C, Ada and Rust.
Another strength of this project is its core guiding principle: provide an open source and open hardware platform using off-the-shelf components for the PCB design to ease its manufacturing and reproducibility.