Supporting Secured Integration of Microarchitectural Defenses

TL;DR

This paper introduces a methodology and tools for early detection and evaluation of security vulnerabilities caused by naive integration of microarchitectural defenses, ensuring more secure and effective defense combinations.

Contribution

It presents a two-step methodology including a modeling framework and simulation approach to identify and fix security assumption violations in integrated microarchitectural defenses.

Findings

Maestro reveals 8 microarchitectural defense assumption violations.

Maestro achieves ~15x reduction in modeling complexity.

Repaired defenses resist covert channel attacks in simulation.

Abstract

There has been a plethora of microarchitectural-level attacks leading to many proposed countermeasures. This has created an unexpected and unaddressed security issue where naive integration of those defenses can potentially lead to security vulnerabilities. This occurs when one defense changes an aspect of a microarchitecture that is crucial for the security of another defense. We refer to this problem as a microarchitectural defense assumption violation} (MDAV). We propose a two-step methodology to screen for potential MDAVs in the early-stage of integration. The first step is to design and integrate a composed model, guided by bounded model checking of security properties. The second step is to implement the model concretely on a simulator and to evaluate with simulated attacks. As a contribution supporting the first step, we propose an event-based modeling framework, called Maestro, for testing and evaluating microarchitectural models with integrated defenses. In our evaluation, Maestro reveals MDAVs (8), supports compact expression (~15x Alloy LoC ratio), enables semantic composability and eliminates performance degradations (>100x). As a contribution supporting the second step, we use an event-based simulator (GEM5) for investigating integrated microarchitectural defenses. We show that a covert channel attack is possible on a naively integrated implementation of some state-of-the-art defenses, and a repaired implementation using our integration methodology is resilient to the attack.