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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

   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
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   This Internet-Draft will expire on 26 December 2020.

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
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   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.







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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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