Verifying the Reliability of Operating System-Level Information Flow Control Systems in Linux

Information Flow Control at Operating System (OS) level features interesting properties and have been an active topic of research for years. However, no implementation can work reliably if there does not exist a way to correctly and precisely track all information flows occurring in the system. The existing implementations for Linux are based on the Linux Security Modules (LSM) framework which implements hooks at specific points in code where any security mechanism may interpose a security decision in the execution. However, previous works on the verification of LSM only addressed access control and no work has raised the question of the reliability of information flow control systems built on LSM@. In this work, we present a compiler-assisted and reproducible static analysis on the Linux kernel to verify that the LSM hooks are correctly placed with respect to operations generating information flows so that LSM-based information flow monitors can properly track all information flows. Our results highlight flaws in LSM that we propose to solve, thus improving the suitability of this framework for the implementation of information flow monitors.