draft-ietf-httpbis-cice-02.txt   draft-ietf-httpbis-cice-03.txt 
HTTP Working Group J. Reschke HTTP Working Group J. Reschke
Internet-Draft greenbytes Internet-Draft greenbytes
Intended status: Standards Track August 13, 2015 Intended status: Standards Track September 8, 2015
Expires: February 14, 2016 Expires: March 11, 2016
Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding
draft-ietf-httpbis-cice-02 draft-ietf-httpbis-cice-03
Abstract Abstract
In HTTP, content codings allow for payload encodings such as for In HTTP, content codings allow for payload encodings such as for
compression or integrity checks. In particular, the "gzip" content compression or integrity checks. In particular, the "gzip" content
coding is widely used for payload data sent in response messages. coding is widely used for payload data sent in response messages.
Content codings can be used in request messages as well, however Content codings can be used in request messages as well, however
discoverability is not on par with response messages. This document discoverability is not on par with response messages. This document
extends the HTTP "Accept-Encoding" header field for use in responses, extends the HTTP "Accept-Encoding" header field for use in responses,
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Discussion of this draft takes place on the HTTPBIS working group Discussion of this draft takes place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
<https://lists.w3.org/Archives/Public/ietf-http-wg/>. <https://lists.w3.org/Archives/Public/ietf-http-wg/>.
Working Group information can be found at Working Group information can be found at
<https://tools.ietf.org/wg/httpbis/> and <http://httpwg.github.io/>; <https://tools.ietf.org/wg/httpbis/> and <http://httpwg.github.io/>;
source code and issues list for this draft can be found at source code and issues list for this draft can be found at
<https://github.com/httpwg/http-extensions>. <https://github.com/httpwg/http-extensions>.
The changes in this draft are summarized in Appendix A.5. The changes in this draft are summarized in Appendix A.6.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 14, 2016. This Internet-Draft will expire on March 11, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. Using the 'Accept-Encoding' Header Field in Responses . . . . . 3 3. Using the 'Accept-Encoding' Header Field in Responses . . . . . 3
4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Deployment Considerations . . . . . . . . . . . . . . . . . . . 5 5. Deployment Considerations . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Header Field Registry . . . . . . . . . . . . . . . . . . . 5 7.1. Header Field Registry . . . . . . . . . . . . . . . . . . . 5
7.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 6 7.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Change Log (to be removed by RFC Editor before Appendix A. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . 7 publication) . . . . . . . . . . . . . . . . . . . . . 7
A.1. Since draft-reschke-http-cice-00 . . . . . . . . . . . . . 7 A.1. Since draft-reschke-http-cice-00 . . . . . . . . . . . . . 7
A.2. Since draft-reschke-http-cice-01 . . . . . . . . . . . . . 7 A.2. Since draft-reschke-http-cice-01 . . . . . . . . . . . . . 7
A.3. Since draft-reschke-http-cice-02 . . . . . . . . . . . . . 7 A.3. Since draft-reschke-http-cice-02 . . . . . . . . . . . . . 7
A.4. Since draft-ietf-httpbis-cice-00 . . . . . . . . . . . . . 7 A.4. Since draft-ietf-httpbis-cice-00 . . . . . . . . . . . . . 7
A.5. Since draft-ietf-httpbis-cice-01 . . . . . . . . . . . . . 7 A.5. Since draft-ietf-httpbis-cice-01 . . . . . . . . . . . . . 8
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . . 7 A.6. Since draft-ietf-httpbis-cice-02 . . . . . . . . . . . . . 8
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
In HTTP, content codings allow for payload encodings such as for In HTTP, content codings allow for payload encodings such as for
compression or integrity checks ([RFC7231], Section 3.1.2). In compression or integrity checks ([RFC7231], Section 3.1.2). In
particular, the "gzip" content coding is widely used for payload data particular, the "gzip" content coding ([RFC7230], Section 4.2) is
sent in response messages. widely used for payload data sent in response messages.
Content codings can be used in request messages as well, however Content codings can be used in request messages as well, however
discoverability is not on par with response messages. This document discoverability is not on par with response messages. This document
extends the HTTP "Accept-Encoding" header field ([RFC7231], Section extends the HTTP "Accept-Encoding" header field ([RFC7231], Section
5.3.4) for use in responses, to indicate the content codings that are 5.3.4) for use in responses, to indicate the content codings that are
supported in requests. It furthermore updates the definition of supported in requests. It furthermore updates the definition of
status code 415 (Unsupported Media Type) ([RFC7231], Section 6.5.13), status code 415 (Unsupported Media Type) ([RFC7231], Section 6.5.13),
recommending to include the "Accept-Encoding" header field when recommending to include the "Accept-Encoding" header field when
appropriate. appropriate.
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Note that this information is specific to the associated request; the Note that this information is specific to the associated request; the
set of supported encodings might be different for other resources on set of supported encodings might be different for other resources on
the same server, and could change over time or depend on other the same server, and could change over time or depend on other
aspects of the request (such as the request method). aspects of the request (such as the request method).
Section 6.5.13 of [RFC7231] defines status code 415 (Unsupported Section 6.5.13 of [RFC7231] defines status code 415 (Unsupported
Media Type) to apply to both media type and content coding related Media Type) to apply to both media type and content coding related
problems. problems.
Servers that fail a request due to an unsupported content coding Servers that fail a request due to an unsupported content coding
SHOULD respond with a 415 status and SHOULD include an "Accept- ought to respond with a 415 status and ought to include an "Accept-
Encoding" header field in that response, allowing clients to Encoding" header field in that response, allowing clients to
distinguish between content coding related issues and media type distinguish between content coding related issues and media type
related issues. In order to avoid confusion with media type related related issues. In order to avoid confusion with media type related
problems, servers that fail a request with a 415 status for reasons problems, servers that fail a request with a 415 status for reasons
unrelated to content codings SHOULD NOT include the "Accept-Encoding" unrelated to content codings MUST NOT include the "Accept-Encoding"
header field. header field.
It is expected that the most common use of "Accept-Encoding" in It is expected that the most common use of "Accept-Encoding" in
responses will have the 415 (Unsupported Media Type) status code, in responses will have the 415 (Unsupported Media Type) status code, in
response to optimistic use of a content coding by clients. However, response to optimistic use of a content coding by clients. However,
the header field can also be used to indicate to clients that content the header field can also be used to indicate to clients that content
codings are supported, to optimize future interactions. For example, codings are supported, to optimize future interactions. For example,
a resource might include it in a 2xx response when the request a resource might include it in a 2xx response when the request
payload was big enough to justify use of a compression coding, but payload was big enough to justify use of a compression coding, but
the client failed do so. the client failed do so.
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requests with unsupported content codings as well. To be compliant requests with unsupported content codings as well. To be compliant
with this specification, servers will need to use the status code 415 with this specification, servers will need to use the status code 415
(Unsupported Media Type) to signal the problem, and will have to (Unsupported Media Type) to signal the problem, and will have to
include an "Accept-Encoding" header field that enumerates the content include an "Accept-Encoding" header field that enumerates the content
codings that are supported. As the set of supported content codings codings that are supported. As the set of supported content codings
is usually static and small, adding the header field ought to be is usually static and small, adding the header field ought to be
trivial. trivial.
6. Security Considerations 6. Security Considerations
This specification does not introduce any new security considerations This specification only adds discovery of supported content codings
beyond those discussed in Section 9 of [RFC7231]. and diagnostics for requests failing due to unsupported content
codings. As such, it doesn't introduce any new security
considerations over those already present in HTTP/1.1 (Section 9 of
[RFC7231]) and HTTP/2 (Section 10 of [RFC7540]).
However, the point of better discoverability and diagnostics is to
make it easier to use content codings in requests. This might lead
to increased usage of compression codings such as gzip (Section 4.2
of [RFC7230]), which, when used over a secure channel, can enable
side-channel attacks such as BREACH (see Section 10.6 of [RFC7540]
and [BREACH]). At the time of publication, it was unclear how
BREACH-like attacks can be applied to compression in HTTP requests.
7. IANA Considerations 7. IANA Considerations
7.1. Header Field Registry 7.1. Header Field Registry
HTTP header fields are registered within the "Message Headers" HTTP header fields are registered within the "Message Headers"
registry located at registry located at
<http://www.iana.org/assignments/message-headers>, as defined by <http://www.iana.org/assignments/message-headers>, as defined by
[BCP90]. [BCP90].
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Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>. <http://www.rfc-editor.org/info/rfc7231>.
8.2. Informative References 8.2. Informative References
[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864, Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004, <http://www.rfc-editor.org/info/bcp90>. September 2004, <http://www.rfc-editor.org/info/bcp90>.
[BREACH] Gluck, Y., Harris, N., and A. Prado, "BREACH: Reviving the
CRIME Attack", July 2013, <http://breachattack.com/
resources/
BREACH%20-%20SSL,%20gone%20in%2030%20seconds.pdf>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.
Appendix A. Change Log (to be removed by RFC Editor before publication) Appendix A. Change Log (to be removed by RFC Editor before publication)
A.1. Since draft-reschke-http-cice-00 A.1. Since draft-reschke-http-cice-00
Clarified that the information returned in Accept-Encoding is per Clarified that the information returned in Accept-Encoding is per
resource, not per server. resource, not per server.
Added some deployment considerations. Added some deployment considerations.
Updated HTTP/1.1 references. Updated HTTP/1.1 references.
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A.4. Since draft-ietf-httpbis-cice-00 A.4. Since draft-ietf-httpbis-cice-00
Apply editorial improvements suggested by Mark Nottingham. Apply editorial improvements suggested by Mark Nottingham.
A.5. Since draft-ietf-httpbis-cice-01 A.5. Since draft-ietf-httpbis-cice-01
Clarify that we're also extending the definition of status code 415 Clarify that we're also extending the definition of status code 415
(so update that IANA registry entry as well). (so update that IANA registry entry as well).
A.6. Since draft-ietf-httpbis-cice-02
Removed normative language that required used of Accept-Encoding in
responses (which would have made existing servers non-compliant).
Add BREACH like attacks to security considerations
(<https://github.com/httpwg/http-extensions/issues/94>).
Appendix B. Acknowledgements Appendix B. Acknowledgements
Thanks go to the members of the and HTTPbis Working Group, namely Thanks go to the members of the and HTTPbis Working Group, namely
Amos Jeffries, Mark Nottingham, Pete Resnick, and Ted Hardie. Amos Jeffries, Ben Campbell, Mark Nottingham, Pete Resnick, Stephen
Farrell, and Ted Hardie.
Author's Address Author's Address
Julian F. Reschke Julian F. Reschke
greenbytes GmbH greenbytes GmbH
Hafenweg 16 Hafenweg 16
Muenster, NW 48155 Muenster, NW 48155
Germany Germany
EMail: julian.reschke@greenbytes.de EMail: julian.reschke@greenbytes.de
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