Chien-Ying Chen

Jiyang Chen, Tomasz Kloda, Ayoosh Bansal et al.

Real-time systems have recently been shown to be vulnerable to timing inference attacks, mainly due to their predictable behavioral patterns. Existing solutions such as schedule randomization lack the ability to protect against such attacks, often limited by the system's real-time nature. This paper presents SchedGuard: a temporal protection framework for Linux-based hard real-time systems that protects against posterior scheduler side-channel attacks by preventing untrusted tasks from executing during specific time segments. SchedGuard is integrated into the Linux kernel using cgroups, making it amenable to use with container frameworks. We demonstrate the effectiveness of our system using a realistic radio-controlled rover platform and synthetically generated workloads. Not only is SchedGuard able to protect against the attacks mentioned above, but it also ensures that the real-time tasks/containers meet their temporal requirements.

Chien-Ying Chen, Sibin Mohan, Rodolfo Pellizzoni et al.

While the existence of scheduler side-channels has been demonstrated recently for fixed-priority real-time systems (RTS), there have been no similar explorations for dynamic-priority systems. The dynamic nature of such scheduling algorithms, e.g., EDF, poses a significant challenge in this regard. In this paper we demonstrate that side-channels exist in dynamic priority real-time systems. Using this side-channel, our proposed DyPS algorithm is able to effectively infer, with high precision, critical task information from the vantage point of an unprivileged (user space) task. Apart from demonstrating the effectiveness of DyPS, we also explore the various factors that impact such attack algorithms using a large number of synthetic task sets. We also compare against the state-of-the-art and demonstrate that our proposed DyPS algorithms outperform the ScheduLeak algorithms in attacking the EDF RTS.

Chien-Ying Chen, Monowar Hasan, AmirEmad Ghassami et al.

The deterministic (timing) behavior of real-time systems (RTS) can be used by adversaries - say, to launch side channel attacks or even destabilize the system by denying access to critical resources. We propose a protocol (named REORDER) to obfuscate this predictable timing behavior of RTS, especially ones designed using dynamic-priority scheduling algorithms (e.g., EDF). We also present a metric (named "schedule entropy") that measures the levels of obfuscation introduced into a given real-time system. The REORDER protocol was integrated into the standard Linux real-time scheduler and evaluated on a realistic embedded platform (Raspberry Pi) running the MiBench automotive benchmark workloads. We also demonstrate how designers of RTS can increase the security of their systems and also quantitatively measure the impact (both in terms of security and performance) of using this protocol.

Chien-Ying Chen, AmirEmad Ghassami, Sibin Mohan et al.

In real-time embedded systems (RTS), failures due to security breaches can cause serious damage to the system, the environment and/or injury to humans. Therefore, it is very important to understand the potential threats and attacks against these systems. In this paper we present a novel reconnaissance attack that extracts the exact schedule of real-time systems designed using fixed priority scheduling algorithms. The attack is demonstrated on both a real hardware platform and a simulator, with a high success rate. Our evaluation results show that the algorithm is robust even in the presence of execution time variation.

Fardin Abdi, Chien-Ying Chen, Monowar Hasan et al.

Many physical plants that are controlled by embedded systems have safety requirements that need to be respected at all times - any deviations from expected behavior can result in damage to the system (often to the physical plant), the environment or even endanger human life. In recent times, malicious attacks against such systems have increased - many with the intent to cause physical damage. In this paper, we aim to decouple the safety of the plant from security of the embedded system by taking advantage of the inherent inertia in such systems. In this paper we present a system-wide restart-based framework that combines hardware and software components to (a) maintain the system within the safety region and (b) thwart potential attackers from destabilizing the system. We demonstrate the feasibility of our approach using two realistic systems - an actual 3 degree of freedom (3-DoF) helicopter and a simulated warehouse temperature control unit. Our proof-of-concept implementation is tested against multiple emulated attacks on the control units of these systems.