Towards Continuous Integrity Attestation and Its Challenges in Practice: A Case Study of Keylime

Continuous integrity attestation is vital for cloud providers to ensure the integrity of remote systems in a continuous manner. Current solutions, such as Keylime, rely on Trusted Platform Module (TPM) and Linux's Integrity Measurement Architecture (IMA) but often struggle to balance minimizing false alerts and maintaining effective threat detection. In this paper, we examine common causes of attestation failures in Keylime through active experiments. We find that false positives often stem from unscheduled OS updates, and we propose a dynamic policy generation scheme as a solution (validated over 66 days of experiments). Our false negative experiments reveal vulnerabilities in existing designs, including five common issues across Keylime and IMA. Exploiting these issues, attackers could evade detection in all tested scenarios. Our findings offer insights into common failures of continuous integrity attestation, and our proposed solution is being integrated into Keylime with community support, enhancing cloud security. Our code will be available at https://github.com/mruffin/Dynamic-Policy-Generator.