Internet DRAFT - draft-bishop-httpbis-grease
draft-bishop-httpbis-grease
HTTPbis M. Bishop
Internet-Draft Akamai
Intended status: Standards Track 24 June 2020
Expires: 26 December 2020
GREASE for HTTP/2
draft-bishop-httpbis-grease-01
Abstract
Reserves several values in the HTTP/2 registries to exercise the
requirement that clients and servers ignore unknown values.
Status of This Memo
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This Internet-Draft will expire on 26 December 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Using GREASE in HTTP/2 . . . . . . . . . . . . . . . . . . . 2
2.1. GREASE for Frame Types . . . . . . . . . . . . . . . . . 2
2.2. GREASE for SETTINGS . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4.1. Frame Types . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. Settings . . . . . . . . . . . . . . . . . . . . . . . . 3
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.1. Normative References . . . . . . . . . . . . . . . . . . 3
5.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
[UseIt] observes that extension and negotiation mechanisms which
aren't exercised regularly can be found not to work when they are
later employed by an extension to the protocol. [GREASE] is one
mitigation which originated in TLS, registering multiple values in
various TLS registries which can be sent prospectively by clients.
The common requirement of the different spaces described by these
documents is the requirement that recipients ignore unrecognized
values. By reserving a scattered set of codepoints to have no
defined meaning, clients and servers can inject values from these
ranges into connections on a regular basis and exercise this
requirement.
HTTP/2 [HTTP2] frame types and settings employ a similar mechanism of
ignoring unknown values. This makes HTTP/2 a good candidate to
employ grease on connections. The need for such a technique was
demonstrated recently by an HTTP/2 implementation which closed the
connection upon receipt of an unknown setting.
2. Using GREASE in HTTP/2
2.1. GREASE for Frame Types
Frame types of the format "0xb + (0x1f * N)" are reserved for use as
grease. These frames have no semantic meaning, and SHOULD be send
instead of using padding on DATA or HEADERS frames where possible.
They MAY also be sent on connections where there is no application
data currently being transferred. Endpoints MUST NOT consider these
frames to have any meaning upon receipt.
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The flags, the payload, and the length of the frames SHOULD be
selected randomly, subject to implementation-defined limits on the
length.
[HTTP2] is ambiguous about whether unknown frame types are permitted
on streams in the "idle", "reserved", "closed", or "half-closed
(local)" states. As a result, some implementations could
legitimately consider this to be an error. Therefore, these frames
SHOULD NOT be sent on streams in those states.
2.2. GREASE for SETTINGS
Settings identifiers of the format "0x?a?a" are reserved for use as
grease. Such settings have no defined meaning. Endpoints SHOULD
include at least one such setting in their initial SETTINGS frame,
and MAY send new SETTINGS frames during the connection containing
additional grease values. Endpoints MUST NOT consider such settings
to have any meaning upon receipt.
Because the setting has no defined meaning, the value of the setting
SHOULD be selected randomly.
3. Security Considerations
The ability to design, implement, and deploy new protocol mechanisms
can be critical to security.
4. IANA Considerations
4.1. Frame Types
This document reserves a range of entries in the "HTTP/2 Frame Type"
registry defined in [HTTP2]. Each code of the format "0xb + (0x1f *
N)" for values of N in the range (0..7) (that is, "0xb", "0x2a",
etc., through "0xe4") MUST NOT be assigned by IANA for any purpose.
4.2. Settings
This document reserves a range of entries in the "HTTP/2 Settings"
registry defined in [HTTP2]. Each code of the format "0x?a?a" where
each "?" is any octet (that is, "0x0a0a", "0x0a1a", etc. through
"0xfafa") MUST NOT be assigned by IANA for any purpose.
5. References
5.1. Normative References
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[HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>.
5.2. Informative References
[GREASE] Benjamin, D., "Applying GREASE to TLS Extensibility", Work
in Progress, Internet-Draft, draft-ietf-tls-grease-04, 22
August 2019, <http://www.ietf.org/internet-drafts/draft-
ietf-tls-grease-04.txt>.
[UseIt] Thomson, M., "Long-term Viability of Protocol Extension
Mechanisms", Work in Progress, Internet-Draft, draft-
thomson-use-it-or-lose-it-04, 7 July 2019,
<http://www.ietf.org/internet-drafts/draft-thomson-use-it-
or-lose-it-04.txt>.
Appendix A. Acknowledgements
This draft arose from a discussion in the QUIC WG with Lucas Pardue,
Ryan Hamilton, and Martin Thomson.
Author's Address
Mike Bishop
Akamai
Email: mbishop@evequefou.be
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