Demystifying Attestation in Intel Trust Domain Extensions via Formal Verification

• Published in: IEEE access Vol. 9; pp. 83067 - 83079
• Main Authors: Sardar, Muhammad Usama, Musaev, Saidgani, Fetzer, Christof
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical models; Computer bugs; Domains; Feedback; Formal specifications; Formal verification; Intel TDX; Microprocessors; ProVerif; remote attestation; Runtime; Security; Software; Specification and description languages; symbolic security analysis; trust domains; trusted execution environment; Verification; Virtual machine monitors
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2021.3087421

In August 2020, Intel asked the research community for feedback on the newly offered architecture extensions, called Intel Trust Domain Extensions (TDX), which give more control to Trust Domains (TDs) over processor resources. One of the key features of these extensions is the remote attestation mechanism, which provides a unified report verification mechanism for TDX and its predecessor Software Guard Extensions (SGX). Based on our experience and intuition, we respond to the request for feedback by formally specifying the attestation mechanism in the TDX using ProVerif's specification language. Although the TDX technology seems very promising, the process of formal specification reveals a number of subtle discrepancies in Intel's specifications that could potentially lead to design and implementation flaws. After resolving these discrepancies, we also present fully automated proofs that our specification of TD attestation preserves the confidentiality of the secret and authentication of the report by considering the state-of-the-art Dolev-Yao adversary in the symbolic model using ProVerif. We have submitted the draft to Intel, and Intel is in the process of making the changes.