RATS Working Group M. U. Sardar Internet-Draft TU Dresden Updates: 9334 (if approved) 1 November 2025 Intended status: Informational Expires: 5 May 2026 Guidelines for Security Considerations of RATS draft-rats-sardar-sec-cons-latest Abstract This document aims to provide guidelines and best practices for writing security considerations for technical specifications for RATS targeting the needs of implementers, researchers, and protocol designers. It presents an outline of the topics future versions will cover. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://muhammad- usama-sardar.github.io/rats-sec-cons/draft-rats-sardar-sec-cons.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-rats-sardar-sec-cons/. Source for this draft and an issue tracker can be found at https://github.com/muhammad-usama-sardar/rats-sec-cons. 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Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction 2. Conventions and Definitions 3. General Hierarchy of Authentication 4. Threat Modeling 4.1. System Model 4.2. Actors 4.2.1. Legal perspective 4.2.2. Technical perspective 4.3. Threat Model 4.4. Typical Security Goals 5. Attacks 6. Potential Mitigations 7. Examples of Specifications That Could Be Improved 7.1. RFC9334 7.1.1. Unprotected Evidence 7.1.2. Missing Roles and Conceptual Messages 8. Examples of Parts of Specifications That Are Detrimental for Security 9. Security Considerations 10. IANA Considerations 11. References 11.1. Normative References 11.2. Informative References Acknowledgments Author's Address 1. Introduction While [I-D.irtf-cfrg-cryptography-specification] provides excellent guidelines, remote attestation [RFC9334] has several distinguishing features which necessitate a separate document. One specific example of such feature is architectural complexity. 2. Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. General Hierarchy of Authentication [Gen-Approach] proposes general hierarchy of one-way authentication, which can help precisely state the intended level of authentication (in decreasing order): * One-way injective agreement * One-way non-injective agreement * Aliveness Recentness can be added to each of these levels of authentication. 4. Threat Modeling 4.1. System Model 4.2. Actors 4.2.1. Legal perspective * Data subject is an identifiable natural person (as defined in Article 4 (1) of GDPR [GDPR]). * (Data) Controller (as defined in Article 4 (7) of GDPR [GDPR]) manages and controls what happens with personal data of data subject. * (Data) Processor (as defined in Article 4 (8) of GDPR [GDPR]) performs data processing on behalf of the data controller. 4.2.2. Technical perspective * Infrastucture Provider is a role which refers to the Processor in GDPR. An example of this role is a cloud service provider (CSP). 4.3. Threat Model 4.4. Typical Security Goals 5. Attacks Security considerations in RATS specifications need to clarify how the following attacks are avoided or mitigated: * Diversion attacks: In this attack, a network adversary -- with Dolev-Yao capabilities [Dolev-Yao] and access (e.g., via Foreshadow [Foreshadow]) to attestation key of any machine in the world -- can redirect a connection intended for a specific Infrastructure Provider to the compromised machine, potentially resulting in exposure of confidential data [Meeting-122-TLS-Slides]. * Relay attacks * Replay attacks 6. Potential Mitigations 7. Examples of Specifications That Could Be Improved 7.1. RFC9334 7.1.1. Unprotected Evidence Section 7.4 of [RFC9334] has: | A conveyance protocol that provides authentication and integrity | protection can be used to convey Evidence that is otherwise | unprotected (e.g., not signed). Using a conveyance protocol that provides authentication and integrity protection, such as TLS 1.3 [RFC8446], to convey Evidence that is otherwise unprotected (e.g., not signed) undermines all security of remote attestation. Essentially, this breaks the chain up to the trust anchor (such as hardware manufacturer) for remote attestation. Hence, remote attestation effectively provides no protection in this case and the security guarantees are limited to those of the conveyance protocol only. In order to benefit from remote attestation, Evidence MUST be protected using dedicated keys chaining back to the trust anchor for remote attestation. 7.1.2. Missing Roles and Conceptual Messages * Identity Supplier and its corresponding conceptual message Identity are missing and need to be added to the architecture [Tech-Concepts]. * Attestation Challenge as conceptual message needs to be added to the architecture [Tech-Concepts]. 8. Examples of Parts of Specifications That Are Detrimental for Security It is the author's personal opinion that the following parts of designs are detrimental for the RATS ecosystem: * Multi-Verifiers [I-D.deshpande-rats-multi-verifier]: the design of multi-verifiers not only increases security risks in terms of increasing the Trusted Computing Base (TCB), but also increases the privacy risks, as potentially sensitive information is sent to multiple verifiers. * Aggregator-based design [I-D.ietf-rats-coserv]: Aggregator is an explicit trust anchor and the addition of new trust anchor needs to have a strong justification. 9. Security Considerations All of this document is about security considerations. 10. IANA Considerations This document has no IANA actions. 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and W. Pan, "Remote ATtestation procedureS (RATS) Architecture", RFC 9334, DOI 10.17487/RFC9334, January 2023, . 11.2. Informative References [Dolev-Yao] Dolev, D. and A. Yao, "On the security of public key protocols", March 1983. [Foreshadow] Jo Van Bulck, Marina Minkin, Ofir Weisse, Daniel Genkin, Baris Kasikci, Frank Piessens, Mark Silberstein, Thomas F Wenisch, Yuval Yarom, and Raoul Strackx, "Perspicuity of Attestation Mechanisms in Confidential Computing: Technical Concepts", October 2025, . [GDPR] European Commission, "Regulation (EU) 2016/679 of the European Parliament and of the Council of 27 April 2016 on the protection of natural persons with regard to the pro- cessing of personal data and on the free movement of such data, and repealing Direc- tive 95/46/EC (General Data Protection Regulation) (Text with EEA relevance)", May 2016, . [Gen-Approach] Sardar, M. U., "Perspicuity of Attestation Mechanisms in Confidential Computing: General Approach", October 2025, . [I-D.deshpande-rats-multi-verifier] Deshpande, Y., jun, Z., Labiod, H., and H. Birkholz, "Remote Attestation with Multiple Verifiers", Work in Progress, Internet-Draft, draft-deshpande-rats-multi- verifier-03, 20 October 2025, . [I-D.ietf-rats-coserv] Howard, P., Fossati, T., Birkholz, H., Kamal, S., Mandyam, G., and D. Ma, "Concise Selector for Endorsements and Reference Values", Work in Progress, Internet-Draft, draft-ietf-rats-coserv-02, 20 October 2025, . [I-D.irtf-cfrg-cryptography-specification] Sullivan, N. and C. A. Wood, "Guidelines for Writing Cryptography Specifications", Work in Progress, Internet- Draft, draft-irtf-cfrg-cryptography-specification-02, 7 July 2025, . [Meeting-122-TLS-Slides] Sardar, M. U., Moustafa, M., and T. Aura, "Identity Crisis in Attested TLS for Confidential Computing", March 2025, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [Tech-Concepts] Sardar, M. U., "Perspicuity of Attestation Mechanisms in Confidential Computing: Technical Concepts", October 2025, . Acknowledgments The author wishes to thank Ira McDonald and Ivan Gudymenko for insightful discussions. The author also gratefully acknowledges the authors of [I-D.irtf-cfrg-cryptography-specification], which serves as the inspiration of this work. Author's Address Muhammad Usama Sardar TU Dresden Email: muhammad_usama.sardar@tu-dresden.de