draft-ietf-httpbis-cice-03.txt		draft-ietf-httpbis-cice-latest.txt
	HTTP Working Group J. Reschke		HTTP Working Group J. Reschke
	Internet-Draft greenbytes		Internet-Draft greenbytes
	Intended status: Standards Track September 8, 2015		Intended status: Standards Track October 28, 2025
	Expires: March 11, 2016		Expires: May 1, 2026
	Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding		Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding
	draft-ietf-httpbis-cice-03		draft-ietf-httpbis-cice-latest
	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,
	to indicate the content codings that are supported in requests.		to indicate the content codings that are supported in requests.
	Editorial Note (To be removed by RFC Editor before publication)		Editorial Note (To be removed by RFC Editor before publication)
	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/
	<https://tools.ietf.org/wg/httpbis/> and <http://httpwg.github.io/>;		httpbis/> and <http://httpwg.github.io/>; source code and issues list
	source code and issues list for this draft can be found at		for this draft can be found at <https://github.com/httpwg/http-
	<https://github.com/httpwg/http-extensions>.		extensions>.
	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 https://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 March 11, 2016.
			This Internet-Draft will expire on May 1, 2026.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2025 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		(https://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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	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 . . . . . . . . . . . . . . . . . . 4
	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 . . . . . . . . . . . . . . . . . . 7		8.2. Informative References . . . . . . . . . . . . . . . . . 6
	Appendix A. Change Log (to be removed by RFC Editor before		Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 8
	publication) . . . . . . . . . . . . . . . . . . . . . 7		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
	A.1. Since draft-reschke-http-cice-00 . . . . . . . . . . . . . 7
	A.2. Since draft-reschke-http-cice-01 . . . . . . . . . . . . . 7
	A.3. Since draft-reschke-http-cice-02 . . . . . . . . . . . . . 7
	A.4. Since draft-ietf-httpbis-cice-00 . . . . . . . . . . . . . 7
	A.5. Since draft-ietf-httpbis-cice-01 . . . . . . . . . . . . . 8
	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 ([RFC7230], Section 4.2) is		particular, the "gzip" content coding ([RFC7230], Section 4.2) is
	widely used for payload data 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],
	5.3.4) for use in responses, to indicate the content codings that are		Section 5.3.4) for use in responses, to indicate the content codings
	supported in requests. It furthermore updates the definition of		that are supported in requests. It furthermore updates the
	status code 415 (Unsupported Media Type) ([RFC7231], Section 6.5.13),		definition of status code 415 (Unsupported Media Type) ([RFC7231],
	recommending to include the "Accept-Encoding" header field when		Section 6.5.13), recommending that the "Accept-Encoding" header field
	appropriate.		be included when appropriate.
	2. Notational Conventions		2. Notational Conventions
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	This document reuses terminology defined in the base HTTP		This document reuses terminology defined in the base HTTP
	specifications, namely Section 2 of [RFC7230] and Section 3.1.2 of		specifications, namely Section 2 of [RFC7230] and Section 3.1.2 of
	[RFC7231].		[RFC7231].
	skipping to change at page 3, line 44 ¶		skipping to change at page 3, line 28 ¶
	header field only.		header field only.
	This specification expands that definition to allow "Accept-Encoding"		This specification expands that definition to allow "Accept-Encoding"
	as a response header field as well. When present in a response, it		as a response header field as well. When present in a response, it
	indicates what content codings the resource was willing to accept in		indicates what content codings the resource was willing to accept in
	the associated request. A field value that only contains "identity"		the associated request. A field value that only contains "identity"
	implies that no content codings were supported.		implies that no content codings were supported.
	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
	aspects of the request (such as the request method).		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 problems related to both media types and
	problems.		content codings.
	Servers that fail a request due to an unsupported content coding		Servers that fail a request due to an unsupported content coding
	ought to respond with a 415 status and ought to 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 issues related to content codings and media
	related issues. In order to avoid confusion with media type related		types. In order to avoid confusion with issues related to media
	problems, servers that fail a request with a 415 status for reasons		types, servers that fail a request with a 415 status for reasons
	unrelated to content codings MUST 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
	the client failed do so.		client failed do so.
	4. Example		4. Example
	A client submits a POST request using the "compress" content coding		A client submits a POST request using the "compress" content coding
	([RFC7231], Section 3.1.2.1):		([RFC7231], Section 3.1.2.1):
	POST /edit/ HTTP/1.1		POST /edit/ HTTP/1.1
	Host: example.org		Host: example.org
	Content-Type: application/atom+xml;type=entry		Content-Type: application/atom+xml;type=entry
	Content-Encoding: compress		Content-Encoding: compress
	...compressed payload...		...compressed payload...
	The server rejects request because it only allows the "gzip" content		The server rejects the request because it only allows the "gzip"
	coding:		content coding:
	HTTP/1.1 415 Unsupported Media Type		HTTP/1.1 415 Unsupported Media Type
	Date: Fri, 09 May 2014 11:43:53 GMT		Date: Fri, 09 May 2014 11:43:53 GMT
	Accept-Encoding: gzip		Accept-Encoding: gzip
	Content-Length: 68		Content-Length: 68
	Content-Type: text/plain		Content-Type: text/plain
	This resource only supports the "gzip" content coding in requests.		This resource only supports the "gzip" content coding in requests.
	...at which point the client can retry the request with the supported		At this point, the client can retry the request with the supported
	"gzip" content coding.		"gzip" content coding.
	Alternatively, a server that does not support any content codings in		Alternatively, a server that does not support any content codings in
	requests could answer with:		requests could answer with:
	HTTP/1.1 415 Unsupported Media Type		HTTP/1.1 415 Unsupported Media Type
	Date: Fri, 09 May 2014 11:43:53 GMT		Date: Fri, 09 May 2014 11:43:53 GMT
	Accept-Encoding: identity		Accept-Encoding: identity
	Content-Length: 61		Content-Length: 61
	Content-Type: text/plain		Content-Type: text/plain
	This resource does not support content codings in requests.		This resource does not support content codings in requests.
	5. Deployment Considerations		5. Deployment Considerations
	Servers that do not support content codings in requests already are		Servers that do not support content codings in requests already are
	required to fail a request that uses a content coding. Section		required to fail a request that uses a content coding.
	6.5.13 of [RFC7231] defines the status code 415 (Unsupported Media		Section 6.5.13 of [RFC7231] defines the status code 415 (Unsupported
	Type) for this purpose, so the only change needed is to include the		Media Type) for this purpose, so the only change needed is to include
	"Accept-Encoding" header field with value "identity" in that		the "Accept-Encoding" header field with the value "identity" in that
	response.		response.
	Servers that do support some content codings are required to fail		Servers that do support some content codings are required to fail
	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 only adds discovery of supported content codings		This specification only adds discovery of supported content codings
	and diagnostics for requests failing due to unsupported content		and diagnostics for requests failing due to unsupported content
	codings. As such, it doesn't introduce any new security		codings. As such, it doesn't introduce any new security
	skipping to change at page 5, line 52 ¶		skipping to change at page 5, line 32 ¶
	of [RFC7230]), which, when used over a secure channel, can enable		of [RFC7230]), which, when used over a secure channel, can enable
	side-channel attacks such as BREACH (see Section 10.6 of [RFC7540]		side-channel attacks such as BREACH (see Section 10.6 of [RFC7540]
	and [BREACH]). At the time of publication, it was unclear how		and [BREACH]). At the time of publication, it was unclear how
	BREACH-like attacks can be applied to compression in HTTP requests.		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-
	<http://www.iana.org/assignments/message-headers>, as defined by		headers>, as defined by [BCP90].
	[BCP90].
	This document updates the definition of the "Accept-Encoding" header		This document updates the definition of the "Accept-Encoding" header
	field, so the "Permanent Message Header Field Names" registry ought		field. The "Permanent Message Header Field Names" registry has been
	to be updated accordingly:		updated as follows:
	+-----------------+----------+----------+---------------------------+		+-----------------+----------+----------+---------------------------+
	| Header Field | Protocol | Status | Reference |		| Header Field | Protocol | Status | Reference |
	| Name | | | |		| Name | | | |
	+-----------------+----------+----------+---------------------------+		+-----------------+----------+----------+---------------------------+
	| Accept-Encoding | http | standard | [RFC7231], Section 5.3.4, |		| Accept-Encoding | http | standard | Section 5.3.4 of |
	| | | | and Section 3 of this |		| | | | [RFC7231] and Section 3 |
	| | | | document |		| | | | of this document |
	+-----------------+----------+----------+---------------------------+		+-----------------+----------+----------+---------------------------+
	7.2. Status Code Registry		7.2. Status Code Registry
	HTTP status codes are registered within the "Status Code" registry		HTTP status codes are registered within the "HTTP Status Codes"
	located at <http://www.iana.org/assignments/http-status-codes>.		registry located at <http://www.iana.org/assignments/http-status-
			codes>.
	This document updates the definition of the status code 415		This document updates the definition of the status code 415
	(Unsupported Media Type), so the "Status Code" registry ought to be		(Unsupported Media Type). The "HTTP Status Codes" registry has been
	updated accordingly:		updated as follows:
	+-------+------------------+----------------------------------------+		+-------+-----------------+-----------------------------------------+
	| Value | Description | Reference |		| Value | Description | Reference |
	+-------+------------------+----------------------------------------+		+-------+-----------------+-----------------------------------------+
	| 415 | Unsupported | [RFC7231], Section 6.5.13, and |		| 415 | Unsupported | Section 6.5.13 of [RFC7231] and |
	| | Media Type | Section 3 of this document |		| | Media Type | Section 3 of this document |
	+-------+------------------+----------------------------------------+		+-------+-----------------+-----------------------------------------+
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/		Requirement Levels", BCP 14, RFC 2119,
	RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Message Syntax and Routing",		Protocol (HTTP/1.1): Message Syntax and Routing",
	RFC 7230, DOI 10.17487/RFC7230, June 2014,		RFC 7230, DOI 10.17487/RFC7230, June 2014,
	<http://www.rfc-editor.org/info/rfc7230>.		<https://www.rfc-editor.org/info/rfc7230>.
	[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	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>.		<https://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, <https://www.rfc-editor.org/info/bcp90>.
	[BREACH] Gluck, Y., Harris, N., and A. Prado, "BREACH: Reviving the		[BREACH] Gluck, Y., Harris, N., and A. Prado, "BREACH: Reviving the
	CRIME Attack", July 2013, <http://breachattack.com/		CRIME Attack", July 2013,
	resources/		<http://breachattack.com/resources/
	BREACH%20-%20SSL,%20gone%20in%2030%20seconds.pdf>.		BREACH%20-%20SSL,%20gone%20in%2030%20seconds.pdf>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext		[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,		Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,		DOI 10.17487/RFC7540, May 2015,
	<http://www.rfc-editor.org/info/rfc7540>.		<https://www.rfc-editor.org/info/rfc7540>.
	Appendix A. Change Log (to be removed by RFC Editor before publication)
	A.1. Since draft-reschke-http-cice-00
	Clarified that the information returned in Accept-Encoding is per
	resource, not per server.
	Added some deployment considerations.
	Updated HTTP/1.1 references.
	A.2. Since draft-reschke-http-cice-01
	Restrict the scope of A-E from "future requests" to "at the time of
	this request".
	Mention use of A-E in responses other than 415.
	Recommend not to include A-E in a 415 response unless there was
	actually a problem related to content coding.
	A.3. Since draft-reschke-http-cice-02
	First Working Group draft; updated boilerplate accordingly.
	A.4. Since draft-ietf-httpbis-cice-00
	Apply editorial improvements suggested by Mark Nottingham.
	A.5. Since draft-ietf-httpbis-cice-01
	Clarify that we're also extending the definition of status code 415
	(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		Acknowledgements
	Thanks go to the members of the and HTTPbis Working Group, namely		Thanks go to the Hypertext Transfer Protocol Working Group
	Amos Jeffries, Ben Campbell, Mark Nottingham, Pete Resnick, Stephen		participants, namely Amos Jeffries, Ben Campbell, Mark Nottingham,
	Farrell, and Ted Hardie.		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
End of changes. 33 change blocks.
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