Importing External PSKs for TLS
draft-ietf-tls-external-psk-importer-06
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Active Internet-Draft (tls WG)
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David Benjamin
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Christopher Wood
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2021-01-07
(latest revision 2020-12-03)
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draft-wood-tls-external-psk-importer
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IETF
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Intended RFC status |
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Proposed Standard
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plain text
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bibtex
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WG state
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Submitted to IESG for Publication
(wg milestone:
Jan 2021 - Submit "Importing Ex...
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Document shepherd |
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Joseph Salowey
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Shepherd write-up |
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Show
(last changed 2020-05-23)
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IESG |
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IESG Evaluation::Revised I-D Needed
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Consensus Boilerplate |
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Yes
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Has a DISCUSS. Has enough positions to pass once DISCUSS positions are resolved.
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Responsible AD |
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Roman Danyliw
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Send notices to |
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Joseph Salowey <joe@salowey.net>
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IANA |
IANA review state |
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IANA OK - Actions Needed
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tls D. Benjamin
Internet-Draft Google, LLC.
Intended status: Standards Track C.A. Wood
Expires: 6 June 2021 Cloudflare
3 December 2020
Importing External PSKs for TLS
draft-ietf-tls-external-psk-importer-06
Abstract
This document describes an interface for importing external Pre-
Shared Keys (PSKs) 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 6 June 2021.
Copyright Notice
Copyright (c) 2020 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 6 June 2021 [Page 1]
Internet-Draft Importing External PSKs for TLS December 2020
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
4. PSK Import . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. External PSK Diversification . . . . . . . . . . . . . . 4
4.2. Binder Key Derivation . . . . . . . . . . . . . . . . . . 6
5. Deprecating Hash Functions . . . . . . . . . . . . . . . . . 6
6. Incremental Deployment . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 10
Appendix B. Addressing Selfie . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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 pseudorandom function (PRF).
While there is no known way in which the same external PSK might
produce related output in TLS 1.3 and prior versions, only limited
analysis has been done. Applications SHOULD provision separate PSKs
for TLS 1.3 and prior versions.
To mitigate against any interference, this document specifies a PSK
Importer interface by which external PSKs may be imported and
subsequently bound to a specific key derivation function (KDF) and
hash function for use in TLS 1.3 [RFC8446] and DTLS 1.3 [DTLS13]. In
particular, it describes a mechanism for differentiating external
PSKs by the target KDF, (D)TLS protocol version, and an optional
context string. This process yields a set of candidate PSKs, each of
which are bound to a target KDF and protocol, that are separate from
those used in (D)TLS 1.2 and prior versions. This expands what would
normally have been a single PSK and identity into a set of PSKs and
identities.
Benjamin & Wood Expires 6 June 2021 [Page 2]
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