Internet DRAFT - draft-tschofenig-core-early-data-option
draft-tschofenig-core-early-data-option
CoRE Working Group H. Tschofenig
Internet-Draft T. Fossati
Intended status: Standards Track Arm Limited
Expires: 7 January 2023 6 July 2022
Early Data Option for CoAP
draft-tschofenig-core-early-data-option-00
Abstract
This document defines mechanisms that allow clients to communicate
with servers about CoAP requests that are sent in early data.
Techniques are described that use these mechanisms to mitigate the
risk of replay.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the Constrained RESTful
Environments Working Group mailing list (core@ietf.org), which is
archived at https://mailarchive.ietf.org/arch/browse/core/.
Source for this draft and an issue tracker can be found at
https://github.com/thomas-fossati/draft-coap-early-data.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 7 January 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. 0-RTT Data . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5.1. New Option . . . . . . . . . . . . . . . . . . . . . . . 4
5.2. New Response Code . . . . . . . . . . . . . . . . . . . . 4
6. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
TLS and DTLS 1.3 provide a "zero round-trip time" (0-RTT) feature,
the mechanics of which are described in Section 2.3 of [TLS13].
This feature provides a significant performance enhancement by
enabling a client to send data to a server whom it has already spoken
to in the first TLS handshake flight. However, TLS does not provide
inherent replay protections for 0-RTT data, therefore the application
running atop the TLS session has to take care of that. Specifically,
Appendix E.5 of [TLS13] establishes that:
Application protocols MUST NOT use 0-RTT data without a profile
that defines its use. That profile needs to identify which
messages or interactions are safe to use with 0-RTT and how to
handle the situation when the server rejects 0-RTT and falls back
to 1-RTT.
This document defines the application profile for CoAP [CoAP] to
allow clients and servers to exchange CoAP requests that are sent in
early data. It also describes how to mitigate the risk of replay.
The design is inspired by [RFC8470].
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1.1. Requirements Language
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.
2. 0-RTT Data
For a given request, the level of tolerance to replay risk is
specific to the resource it operates upon (and therefore only known
to the origin server). In general, if processing a request does not
have state-changing side effects, the consequences of replay are not
significant. The server can choose whether it will process early
data before the TLS handshake completes.
It is RECOMMENDED that origin servers allow resources to explicitly
configure whether early data is appropriate in requests.
This document specifies the Early-Data option, which indicates that
the request has been conveyed in early data and that a client
understands the 4.25 (Too Early) status code. The semantic follows
[RFC8470].
+=====+===+===+===+===+============+========+========+=========+===+
| No. | C | U | N | R | Name | Format | Length | Default | E |
+=====+===+===+===+===+============+========+========+=========+===+
| TBD | x | | | | Early-Data | empty | 0 | (none) | x |
+-----+---+---+---+---+------------+--------+--------+---------+---+
Table 1: Early-Data Option
// Note that 4.25 is just the suggested CoAP response code, which has
// not been registered yet.
3. Open Issues
A list of open issues can be found at https://github.com/thomas-
fossati/draft-coap-early-data/issues
4. Security Considerations
Background:
* Appendix E.5 of [TLS13]
* Section 8 of [TLS13]
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* Section 6 of [RFC8470]
5. IANA Considerations
5.1. New Option
IANA is asked to add the Option defined in Table 2 to the CoAP Option
Numbers registry.
+========+============+===========+
| Number | Name | Reference |
+========+============+===========+
| TBD | Early-Data | RFCthis |
+--------+------------+-----------+
Table 2: Early-Data Option
5.2. New Response Code
IANA is asked to add the Response Code defined in Table 3 to the CoAP
Response Code registry.
+======+=============+===========+
| Code | Description | Reference |
+======+=============+===========+
| 4.25 | Too Early | RFCthis |
+------+-------------+-----------+
Table 3: Too Early Response Code
6. Normative References
[CoAP] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/rfc/rfc7252>.
[DTLS13] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
<https://www.rfc-editor.org/rfc/rfc9147>.
[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/rfc/rfc2119>.
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[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/rfc/rfc8174>.
[RFC8470] Thomson, M., Nottingham, M., and W. Tarreau, "Using Early
Data in HTTP", RFC 8470, DOI 10.17487/RFC8470, September
2018, <https://www.rfc-editor.org/rfc/rfc8470>.
[TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>.
Authors' Addresses
Hannes Tschofenig
Arm Limited
Email: Hannes.Tschofenig@gmx.net
Thomas Fossati
Arm Limited
Email: Thomas.Fossati@arm.com
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