RATS Working Group M. U. Sardar Internet-Draft TU Dresden Updates: 9334 (if approved) S. Bu Intended status: Informational Stevens Institute of Technology Expires: 2 April 2027 C. Huang Independent H. Song Shanghai Guan An Information Technology Co., Ltd. 29 September 2026 Guidelines for Security Considerations of RATS draft-sardar-rats-sec-cons-06 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. In particular, it discusses some of the 'bottom turtle' issues. This is a work-in-progress, and the current version mainly presents an outline of the general security guidelines, baseline, or template for RATS that future versions will cover in more detail. 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-sardar-rats-sec-cons.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-sardar-rats-sec-cons/. Source for this draft and an issue tracker can be found at https://github.com/muhammad-usama-sardar/rats-sec-cons. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Sardar, et al. Expires 2 April 2027 [Page 1] Internet-Draft RATS Security Considerations September 2026 Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 2 April 2027. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Need for Specialized Guidance in RATS . . . . . . . . . . 3 1.2. Needs of the Target Audience of RATS . . . . . . . . . . 3 1.3. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 1.3.1. Concrete Motivational Example: Practical Exploits in Production Systems . . . . . . . . . . . . . . . . . 4 1.4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4 3. General Hierarchy of Authentication . . . . . . . . . . . . . 4 4. Threat Modeling . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. System Model . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Actors . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.2.1. Legal perspective . . . . . . . . . . . . . . . . . . 5 4.2.2. Technical perspective . . . . . . . . . . . . . . . . 5 4.3. Threat Model . . . . . . . . . . . . . . . . . . . . . . 5 4.4. Typical Security Goals . . . . . . . . . . . . . . . . . 5 5. Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. (Evidence) Replay Attacks . . . . . . . . . . . . . . . . 6 5.2. Diversion Attacks . . . . . . . . . . . . . . . . . . . . 6 5.3. Relay Attacks . . . . . . . . . . . . . . . . . . . . . . 6 6. Potential Mitigations . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 Sardar, et al. Expires 2 April 2027 [Page 2] Internet-Draft RATS Security Considerations September 2026 9.2. Informative References . . . . . . . . . . . . . . . . . 7 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction 1.1. Need for Specialized Guidance in RATS Every Internet Draft needs to have a "Security Considerations" section. While general guidelines such as [RFC3552] exist, the underlying threat model is that the endpoint is fully trusted (i.e., all software and hardware components in the device may access the keys). RATS [RFC9334] has a primarily different threat model in the sense that only parts of the endpoint (called Attester) are trusted (i.e., only specific software and hardware components in the device may access the keys), and the goal is to establish the trustworthiness of the endpoint. In other words, [RFC3552] deals with a network adversary, whereas RATS deals with an endpoint adversary, which may have root access or physical control over the device with which it can extract keys from software or hardware. Moreover, remote attestation has several distinguishing features that necessitate a separate document. One specific example of such a feature is the architectural complexity of the endpoint. While network protocols typically have 2 roles, RATS has additional roles, which complicates the picture. Unfortunately, no guidelines currently exist for remote attestation [RFC9334] in RATS. This document aims to fill this gap. 1.2. Needs of the Target Audience of RATS Moreover, while the target audience of Internet Drafts is implementers, researchers, and protocol designers [I-D.irtf-cfrg-cryptography-specification], RATS drafts generally do not fulfill these needs, in particular the needs of researchers and protocol designers. On the other hand, in our observation, implementers generally find it hard to relate the abstract concepts of RATS to the real-world systems. In general, implementers and protocol designers of RATS are thus left with little or no guidance. 1.3. Motivation Unverified protocol designs, imprecisely stated threat model and security goals have led to high and critical severity vulnerabilities related to remote attestation. Sardar, et al. Expires 2 April 2027 [Page 3] Internet-Draft RATS Security Considerations September 2026 1.3.1. Concrete Motivational Example: Practical Exploits in Production Systems The formal analysis led to three orthogonal issues: * Formal analysis [ID-Crisis-repo] found *diversion* attacks when unique hardware identifier is not included in Evidence. For technical details, please see the corresponding paper [ID-Crisis]. * Formal analysis [Intra-handshake.fail-repo] of several *production* implementations of remote attestation led to the discovery of [CVE-2026-33697] of *CVSS 7.5* for *relay* attacks. For technical details, please see the corresponding paper [Intra-handshake.fail]. * Further formal analysis of *production* implementation of remote attestation has led to discovery of another class of attacks and will potentially lead to three CVEs (currently under _responsible_ disclosure) _each_ with an expected *CVSS 9.1*. This shows the value of precise threat model and formal analysis in the design of secure protocols to find subtle vulnerabilities, which could otherwise be missed. This draft aims to provide the baseline security considerations that other drafts can simply refer to. 1.4. Scope To improve the situation, this draft presents general security baseline that other drafts can simply point to, or guidelines or template that other drafts can use. 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 Authentication is a term which is often ambiguous in RATS specifications. We propose general hierarchy of one-way authentication, which can help precisely state the intended level of authentication (in decreasing order): * One-way injective agreement Sardar, et al. Expires 2 April 2027 [Page 4] Internet-Draft RATS Security Considerations September 2026 * One-way non-injective agreement * Aliveness Recentness can be added to each of these levels of authentication. Details will be added in future versions. 4. Threat Modeling This section describes "What can go wrong?" 4.1. System Model See Section 4 of [Intra-handshake.fail] as an example. 4.2. Actors It has both legal and technical perspective. 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 See Section 6.1 of [Intra-handshake.fail] as an example. 4.4. Typical Security Goals See [ID-Crisis] as an example. 5. Attacks Security considerations in RATS specifications need to clarify how the following attacks are avoided or mitigated: Sardar, et al. Expires 2 April 2027 [Page 5] Internet-Draft RATS Security Considerations September 2026 5.1. (Evidence) Replay Attacks In this attack, a network or endpoint adversary -- with access to older Evidence -- can replay Evidence with stale Claims which no longer represent the actual state of the Attester, potentially resulting in exposure of confidential data [RA-TLS]. Replay of stale Evidence may be within the same connection or across multiple connections. 5.2. Diversion Attacks In this attack, a network adversary -- with Dolev-Yao capabilities [Dolev-Yao] and access (e.g., via Foreshadow [Foreshadow]) to the 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 [ID-Crisis]. In the context of confidential computing and TLS as a transport protocol, we reported these attacks to the TLS WG in February 2025 [Usama-TLS-26Feb25]. A formal proof is available [ID-Crisis-repo] for further research and development. Since reporting to TLS WG, these attacks have been practically exploited in TEE.fail (https://tee.fail/), Wiretap.fail (https://wiretap.fail/), and BadRAM (https://badram.eu/). 5.3. Relay Attacks In this attack, a network or endpoint adversary -- with access to suitable binding material -- can relay an attestation request to a genuine Attester and present the genuine Evidence as its own, potentially resulting in impersonation of genuine Attester [Intra-handshake.fail]. Note that _replay_ is about _same_ Attester while _relay_ attack is about _different_ Attesters. 6. Potential Mitigations This section describes the countermeasures and their evaluation. To mitigate the above attacks, we propose post-handshake attestation. We are not aware of any attacks on post-handshake attestation. Post- handshake attestation avoids replay attacks by using a fresh attestation nonce. Moreover, considering TLS as the transport protocol, it avoids diversion and relay attacks by binding the Evidence to the underlying TLS connection, such as using Exported Sardar, et al. Expires 2 April 2027 [Page 6] Internet-Draft RATS Security Considerations September 2026 Keying Material (EKM) [I-D.ietf-tls-rfc8446bis], as proposed in Section 9.2 of [ID-Crisis]. [RFC9261] and [RFC9266] provide mechanisms for such bindings. Efforts for a formal proof of security of post-handshake attestation are ongoing. 7. Security Considerations All of this document is about security considerations. 8. IANA Considerations This document has no IANA actions. 9. References 9.1. 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, . 9.2. Informative References [CVE-2026-33697] CVE, "CoCoS attested TLS is vulnerable to relay attacks via extracted ephemeral TLS keys", March 2026, . [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, "Foreshadow", October 2025, . Sardar, et al. Expires 2 April 2027 [Page 7] Internet-Draft RATS Security Considerations September 2026 [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 processing of personal data and on the free movement of such data, and repealing Directive 95/46/EC (General Data Protection Regulation) (Text with EEA relevance)", May 2016, . [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-04, 7 February 2026, . [I-D.ietf-tls-rfc8446bis] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", Work in Progress, Internet-Draft, draft- ietf-tls-rfc8446bis-14, 13 September 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-03, 6 July 2026, . [ID-Crisis] Sardar, M., Moustafa, M., and T. Aura, "Identity Crisis in Confidential Computing: Formal Analysis of Attested TLS", ACM, Proceedings of the ACM Asia Conference on Computer and Communications Security pp. 547-560, DOI 10.1145/3779208.3785387, June 2026, . [ID-Crisis-repo] Sardar, M. U., Moustafa, M., and T. Aura, "Identity Crisis in Confidential Computing: Formal Analysis of Attested TLS", November 2025, . Sardar, et al. Expires 2 April 2027 [Page 8] Internet-Draft RATS Security Considerations September 2026 [Intra-handshake.fail] Sardar, M. U., Dubeyko, V., and J.-M. Jacquet, "Intra- handshake.fail (CVE-2026-33697): High-severity CVE in Attested TLS", June 2026, . [Intra-handshake.fail-repo] Sardar, M. U., Dubeyko, V., and J.-M. Jacquet, "Intra- handshake.fail (CVE-2026-33697): High-severity CVE in Attested TLS", June 2026, . [RA-TLS] Sardar, M., Niemi, A., Tschofenig, H., and T. Fossati, "Towards Validation of TLS 1.3 Formal Model and Vulnerabilities in Intel’s RA-TLS Protocol", Institute of Electrical and Electronics Engineers (IEEE), IEEE Access vol. 12, pp. 173670-173685, DOI 10.1109/access.2024.3497184, 2024, . [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, DOI 10.17487/RFC3552, July 2003, . [RFC9261] Sullivan, N., "Exported Authenticators in TLS", RFC 9261, DOI 10.17487/RFC9261, July 2022, . [RFC9266] Whited, S., "Channel Bindings for TLS 1.3", RFC 9266, DOI 10.17487/RFC9266, July 2022, . [Usama-TLS-26Feb25] Muhammad Usama Sardar, "Impersonation attacks on protocol in draft-fossati-tls-attestation (Identity crisis in Attested TLS) for Confidential Computing", February 2025, . Acknowledgments The author wishes to thank Ira McDonald and Ivan Gudymenko for insightful discussions. Sardar, et al. Expires 2 April 2027 [Page 9] Internet-Draft RATS Security Considerations September 2026 History -01 * Concrete text proposal for security and privacy considerations of multi-verifiers [I-D.deshpande-rats-multi-verifier] -02 * Introduction and motivation * Defined replay and relay attacks * Added mitigations Authors' Addresses Muhammad Usama Sardar TU Dresden Email: muhammad_usama.sardar@tu-dresden.de Songbo Bu Stevens Institute of Technology New York, United States of America Email: bluedognull@gmail.com Chengxin Huang Independent Email: aurestarnull@gmail.com Haowen Song Shanghai Guan An Information Technology Co., Ltd. China Email: havan12050544@gmail.com Sardar, et al. Expires 2 April 2027 [Page 10]