TLS 1.3 Extended Key Schedule
draft-jhoyla-tls-extended-key-schedule-03
jhoyla J. Hoyland
Internet-Draft Cloudflare Ltd.
Intended status: Standards Track C.A. Wood
Expires: 7 June 2021 Cloudflare
4 December 2020
TLS 1.3 Extended Key Schedule
draft-jhoyla-tls-extended-key-schedule-03
Abstract
TLS 1.3 is sometimes used in situations where it is necessary to
inject extra key material into the handshake. This draft aims to
describe methods for doing so securely. This key material must be
injected in such a way that both parties agree on what is being
injected and why, and further, in what order.
Note to Readers
Discussion of this document takes place on the TLS Working Group
mailing list (tls@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/tls/
(https://mailarchive.ietf.org/arch/browse/tls/).
Source for this draft and an issue tracker can be found at
https://github.com/jhoyla/draft-jhoyla-tls-key-injection
(https://github.com/jhoyla/draft-jhoyla-tls-key-injection).
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
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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 7 June 2021.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Key Schedule Extension . . . . . . . . . . . . . . . . . . . 3
3.1. Handshake Secret Injection . . . . . . . . . . . . . . . 3
3.2. Main Secret Injection . . . . . . . . . . . . . . . . . . 3
4. Key Schedule Injection Negotiation . . . . . . . . . . . . . 4
5. Key Schedule Extension Structure . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Potential Use Cases . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Introducing additional key material into the TLS handshake is a non-
trivial process because both parties need to agree on the injection
content and context. If the two parties do not agree then an
attacker may exploit the mismatch in so-called channel
synchronization attacks, such as those described by [SLOTH].
Injecting key material into the TLS handshake allows other protocols
to be bound to the handshake. For example, it may provide additional
protections to the ClientHello message, which in the standard TLS
handshake only receives protections after the server's Finished
message has been received. It may also permit the use of combined
shared secrets, possibly from multiple key exchange algorithms, to be
included in the key schedule. This pattern is common for Post
Quantum key exchange algorithms, as discussed in
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[I-D.ietf-tls-hybrid-design]. In particular,
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