Importing External PSKs for TLS
draft-ietf-tls-external-psk-importer-01
tls D. Benjamin
Internet-Draft Google, LLC.
Intended status: Standards Track C. Wood
Expires: April 4, 2020 Apple, Inc.
October 02, 2019
Importing External PSKs for TLS
draft-ietf-tls-external-psk-importer-01
Abstract
This document describes an interface for importing external PSK (Pre-
Shared Key) into TLS 1.3.
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/.
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 April 4, 2020.
Copyright Notice
Copyright (c) 2019 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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Benjamin & Wood Expires April 4, 2020 [Page 1]
Internet-Draft Importing External PSKs for TLS October 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
4. Key Import . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Deprecating Hash Functions . . . . . . . . . . . . . . . . . 5
6. Incremental Deployment . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8
Appendix B. Addressing Selfie . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
TLS 1.3 [RFC8446] supports pre-shared key (PSK) authentication,
wherein PSKs can be established via session tickets from prior
connections or externally via some out-of-band mechanism. The
protocol mandates that each PSK only be used with a single hash
function. This was done to simplify protocol analysis. TLS 1.2
[RFC5246], in contrast, has no such requirement, as a PSK may be used
with any hash algorithm and the TLS 1.2 PRF. This means that
external PSKs could possibly be re-used in two different contexts
with the same hash functions during key derivation. Moreover, it
requires external PSKs to be provisioned for specific hash functions.
To mitigate these problems, external PSKs can be bound to a specific
KDF and hash function when used in TLS 1.3, even if they are
associated with a different hash function when provisioned. This
document specifies an interface by which external PSKs may be
imported for use in a TLS 1.3 connection to achieve this goal. In
particular, it describes how KDF-bound PSKs can be differentiated by
the target (D)TLS protocol version and KDF for which the PSK will be
used. This produces a set of candidate PSKs, each of which are bound
to a specific target protocol and KDF. This expands what would
normally have been a single PSK identity into a set of PSK
identities. However, importantly, it requires no change to the TLS
1.3 key schedule.
Benjamin & Wood Expires April 4, 2020 [Page 2]
Internet-Draft Importing External PSKs for TLS October 2019
2. Conventions and Definitions
Show full document text