PEM file format for ECH
draft-farrell-tls-pemesni-06
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Stephen Farrell | ||
| Last updated | 2023-12-04 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
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draft-farrell-tls-pemesni-06
TLS S. Farrell
Internet-Draft Trinity College Dublin
Intended status: Experimental 4 December 2023
Expires: 6 June 2024
PEM file format for ECH
draft-farrell-tls-pemesni-06
Abstract
Encrypted ClientHello (ECH) key pairs need to be configured into TLS
servers, that can be built using different TLS libraries, so there is
a benefit and little cost in documenting a file format to use for
these key pairs, similar to how RFC7468 defines other PEM file
formats.
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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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 2024.
Copyright Notice
Copyright (c) 2023 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/
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Please review these documents carefully, as they describe your rights
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extracted from this document must include Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. ECHConfig file . . . . . . . . . . . . . . . . . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
7. Normative References . . . . . . . . . . . . . . . . . . . . 3
Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
Encrypted ClientHello (ECH) [I-D.ietf-tls-esni] for TLS1.3 [RFC8446]
defines a confidentiality mechanism for server names and other
ClientHello content in TLS. That requires publication of an
ECHConfigList data structure in an HTTPS or SVCB RR
[I-D.ietf-dnsop-svcb-https] in the DNS. An ECHConfigList can contain
one or more ECHConfig values. An ECHConfig structure contains the
public component of a key pair that will typically be periodically
(re-)generated by some key manager for a TLS server. TLS servers
then need to be configured to use these key pairs, and given that
various TLS servers can be built with different TLS libraries, there
is a benefit in having a standard format for ECH key pairs, just as
was done with [RFC7468].
[[At present, based on TLS WG list discussion, it seems most likely
that this draft will be sent to the Independent stream once ECH is
done and dusted (but not before). The source for this is in
https://github.com/sftcd/pemesni/ PRs are welcome there too.]]
2. Terminology
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. ECHConfig file
The public and private keys MUST both be PEM encoded. The file
contains the catenation of the PEM encoding of the private key
followed by the PEM encoding of the public key as an ECHConfigList
containing exactly one ECHConfig. The private key MUST be encoded as
a PKCS#8 PrivateKey. The public key MUST be the base64 encoded form
of an ECHConfigList value that can also be published in the DNS. The
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string "ECHCONFIG" MUST be used in the PEM file delimiter for the
public key.
There MUST only be one key pair in each file even if a server
publishes multiple public keys in the DNS in one ECHConfigList
structure.
Figure 1 shows an example ECHConfig PEM File
-----BEGIN PRIVATE KEY-----
MC4CAQAwBQYDK2VuBCIEICjd4yGRdsoP9gU7YT7My8DHx1Tjme8GYDXrOMCi8v1V
-----END PRIVATE KEY-----
-----BEGIN ECHCONFIG-----
AD7+DQA65wAgACA8wVN2BtscOl3vQheUzHeIkVmKIiydUhDCliA4iyQRCwAEAAEA
AQALZXhhbXBsZS5jb20AAA==
-----END ECHCONFIG-----
Figure 1: Example ECHConfig PEM file
4. Security Considerations
Storing cryptographic keys in files leaves them vulnerable should
anyone get shell access to the TLS server machine. So: Don't let
that happen:-)
5. Acknowledgements
TBD, as needed
6. IANA Considerations
There are none so this section can be deleted later.
7. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7468] Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
April 2015, <https://www.rfc-editor.org/info/rfc7468>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[I-D.ietf-tls-esni]
Rescorla, E., Oku, K., Sullivan, N., and C. A. Wood, "TLS
Encrypted Client Hello", Work in Progress, Internet-Draft,
draft-ietf-tls-esni-17, 9 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
esni-17>.
[I-D.ietf-dnsop-svcb-https]
Schwartz, B. M., Bishop, M., and E. Nygren, "Service
binding and parameter specification via the DNS (DNS SVCB
and HTTPS RRs)", Work in Progress, Internet-Draft, draft-
ietf-dnsop-svcb-https-12, 11 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-
svcb-https-12>.
Appendix A. Changes
From -05 to -06:
* Refresh due to expiry.
From -04 to -05:
* Refresh due to expiry.
From -03 to -04:
* Refresh due to expiry.
From -02 to -03:
* Refresh due to expiry and not possible ISE destination
From -01 to -02:
* ECHO -> ECH
From -00 to -01:
* ESNI -> ECHO
Author's Address
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Stephen Farrell
Trinity College Dublin
Dublin
2
Ireland
Phone: +353-1-896-2354
Email: stephen.farrell@cs.tcd.ie
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