A Case Study on Covert Channel Establishment via Software Caches in High-Assurance Computing Systems

TL;DR

This paper explores how software caches can be exploited to establish covert channels in high-assurance computing systems, demonstrating vulnerabilities and proposing disruption methods to enhance security.

Contribution

It presents a detailed case study of covert channel establishment via file system caching in component-based OS, highlighting security risks in high-assurance systems.

Findings

Covert timing channels can be created through file system caches.

Such channels are stable and can be disrupted with specific methodologies.

High-assurance systems are vulnerable despite minimal trusted computing bases.

Abstract

Covert channels can be utilized to secretly deliver information from high privileged processes to low privileged processes in the context of a high-assurance computing system. In this case study, we investigate the possibility of covert channel establishment via software caches in the context of a framework for component-based operating systems. While component-based operating systems offer security through the encapsulation of system service processes, complete isolation of these processes is not reasonably feasible. This limitation is practically demonstrated with our concept of a specific covert timing channel based on file system caching. The stability of the covert channel is evaluated and a methodology to disrupt the covert channel transmission is presented. While these kinds of attacks are not limited to high-assurance computing systems, our study practically demonstrates that even security-focused computing systems with a minimal trusted computing base are vulnerable for such kinds of attacks and careful design decisions are necessary for secure operating system architectures.