draft-reschke-http-jfv-00.txt		draft-reschke-http-jfv-01.txt
	Network Working Group J. Reschke		Network Working Group J. Reschke
	Internet-Draft greenbytes		Internet-Draft greenbytes
	Intended status: Standards Track July 2, 2014		Intended status: Standards Track March 9, 2015
	Expires: January 3, 2015		Expires: September 10, 2015
	A JSON Encoding for HTTP Header Field Values		A JSON Encoding for HTTP Header Field Values
	draft-reschke-http-jfv-00		draft-reschke-http-jfv-01
	Abstract		Abstract
	This document establishes a convention for use of JSON-encoded field		This document establishes a convention for use of JSON-encoded field
	values in HTTP header fields.		values in HTTP header fields.
	Editorial Note (To be removed by RFC Editor before publication)		Editorial Note (To be removed by RFC Editor before publication)
	Distribution of this document is unlimited. Although this is not a		Distribution of this document is unlimited. Although this is not a
	work item of the HTTPbis Working Group, comments should be sent to		work item of the HTTPbis Working Group, comments should be sent to
	skipping to change at page 1, line 45 ¶		skipping to change at page 1, line 45 ¶
	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 January 3, 2015.		This Internet-Draft will expire on September 10, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2014 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
	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
	skipping to change at page 2, line 27 ¶		skipping to change at page 2, line 27 ¶
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Data Model and Format . . . . . . . . . . . . . . . . . . . . . 3		2. Data Model and Format . . . . . . . . . . . . . . . . . . . . . 3
	3. Sender Requirements . . . . . . . . . . . . . . . . . . . . . . 4		3. Sender Requirements . . . . . . . . . . . . . . . . . . . . . . 4
	4. Recipient Requirements . . . . . . . . . . . . . . . . . . . . 5		4. Recipient Requirements . . . . . . . . . . . . . . . . . . . . 5
	5. Using this Format in Header Field Definitions . . . . . . . . . 5		5. Using this Format in Header Field Definitions . . . . . . . . . 5
	6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5		6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	6.1. Content-Length . . . . . . . . . . . . . . . . . . . . . . 5		6.1. Content-Length . . . . . . . . . . . . . . . . . . . . . . 5
	6.2. Content-Disposition . . . . . . . . . . . . . . . . . . . . 6		6.2. Content-Disposition . . . . . . . . . . . . . . . . . . . . 6
	6.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . . 7		6.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . . 7
	7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 8		7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 7
	8. Deployment Considerations . . . . . . . . . . . . . . . . . . . 8		8. Deployment Considerations . . . . . . . . . . . . . . . . . . . 8
	9. Internationalization Considerations . . . . . . . . . . . . . . 8		9. Internationalization Considerations . . . . . . . . . . . . . . 8
	10. Security Considerations . . . . . . . . . . . . . . . . . . . . 8		10. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8		11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	11.1. Normative References . . . . . . . . . . . . . . . . . . . 8		11.1. Normative References . . . . . . . . . . . . . . . . . . . 8
	11.2. Informative References . . . . . . . . . . . . . . . . . . 9		11.2. Informative References . . . . . . . . . . . . . . . . . . 9
	Appendix A. Sample Code and Test Cases . . . . . . . . . . . . . . 9		Appendix A. Change Log (to be removed by RFC Editor before
			publication) . . . . . . . . . . . . . . . . . . . . . 9
			A.1. draft-reschke-http-jfv-00 . . . . . . . . . . . . . . . . . 9
	1. Introduction		1. Introduction
	Defining syntax for new HTTP header fields ([RFC7230], Section 3.2)		Defining syntax for new HTTP header fields ([RFC7230], Section 3.2)
	is non-trivial. Among the commonly encountered problems are:		is non-trivial. Among the commonly encountered problems are:
	o There is no common syntax for complex field values. Several well-		o There is no common syntax for complex field values. Several well-
	known header fields do use a similarly looking syntax, but it is		known header fields do use a similarly looking syntax, but it is
	hard to write generic parsing code that will both correctly handle		hard to write generic parsing code that will both correctly handle
	valid field values but also fail on invalid ones.		valid field values but also reject invalid ones.
	o The HTTP message format allows header fields to repeat, so field		o The HTTP message format allows header fields to repeat, so field
	syntax needs to be designed in a way that these cases are either		syntax needs to be designed in a way that these cases are either
	meaningful, or can be unambiguously detected and rejected.		meaningful, or can be unambiguously detected and rejected.
	o HTTP/1.1 does not define a character encoding scheme ([RFC6365],		o HTTP/1.1 does not define a character encoding scheme ([RFC6365],
	Section 2), so header fields are either stuck with US-ASCII		Section 2), so header fields are either stuck with US-ASCII
	([USASCII]), or need out-of-band information to decide what		([RFC0020]), or need out-of-band information to decide what
	encoding scheme is used. Furthermore, APIs usually assume a		encoding scheme is used. Furthermore, APIs usually assume a
	default encoding scheme in order to map from octet sequences to		default encoding scheme in order to map from octet sequences to
	strings (for instance, [XMLHttpRequest] uses the IDL type		strings (for instance, [XMLHttpRequest] uses the IDL type
	"ByteString", effectively resulting in the ISO-8859-1 character		"ByteString", effectively resulting in the ISO-8859-1 character
	encoding scheme [ISO-8859-1] being used).		encoding scheme [ISO-8859-1] being used).
	(See Section 8.3.1 of [RFC7231] for a summary of considerations for		(See Section 8.3.1 of [RFC7231] for a summary of considerations for
	new header fields.)		new header fields.)
	This specification addresses the issues listed above by defining both		This specification addresses the issues listed above by defining both
	skipping to change at page 3, line 45 ¶		skipping to change at page 3, line 45 ¶
	2. Data Model and Format		2. Data Model and Format
	In HTTP, header fields with the same field name can occur multiple		In HTTP, header fields with the same field name can occur multiple
	times within a single message (Section 3.2.2 of [RFC7230]). When		times within a single message (Section 3.2.2 of [RFC7230]). When
	this happens, recipients are allowed to combine the field values		this happens, recipients are allowed to combine the field values
	using commas as delimiter. This rule matches nicely JSON's array		using commas as delimiter. This rule matches nicely JSON's array
	format (Section 5 of [RFC7159]). Thus, the basic data model used		format (Section 5 of [RFC7159]). Thus, the basic data model used
	here is the JSON array.		here is the JSON array.
	Header field definitions that need only a single value can restrict		Header field definitions that need only a single value can restrict
	themselves to arrays of lenght 1, and are encouraged to define error		themselves to arrays of length 1, and are encouraged to define error
	handling in case more values are received (such as "first wins",		handling in case more values are received (such as "first wins",
	"last wins", or "abort with fatal error message").		"last wins", or "abort with fatal error message").
	JSON arrays are mapped to field values by creating a sequence of		JSON arrays are mapped to field values by creating a sequence of
	serialized member elements, separated by commas and optionally		serialized member elements, separated by commas and optionally
	whitespace. This is equivalent to using the full JSON array format,		whitespace. This is equivalent to using the full JSON array format,
	while leaving out the "begin-array" ('[') and "end-array" (']')		while leaving out the "begin-array" ('[') and "end-array" (']')
	delimiters.		delimiters.
	The ABNF character names and classes below are used (copied from		The ABNF character names and classes below are used (copied from
	skipping to change at page 4, line 22 ¶		skipping to change at page 4, line 22 ¶
	SP = %x20 ; space		SP = %x20 ; space
	VCHAR = %x21-7E ; visible (printing) characters		VCHAR = %x21-7E ; visible (printing) characters
	Characters in JSON strings that are not allowed or discouraged in		Characters in JSON strings that are not allowed or discouraged in
	HTTP header field values -- that is, not in the "VCHAR" definition --		HTTP header field values -- that is, not in the "VCHAR" definition --
	need to be represented using JSON's "backslash" escaping mechanism		need to be represented using JSON's "backslash" escaping mechanism
	([RFC7159], Section 7).		([RFC7159], Section 7).
	The control characters CR, LF, and HTAB do not appear inside JSON		The control characters CR, LF, and HTAB do not appear inside JSON
	strings, but can be used outside (line breaks, indentation etc).		strings, but can be used outside (line breaks, indentation etc).
	These characters can be either stripped or replaced by space		These characters need to be either stripped or replaced by space
	characters (ABNF "SP").		characters (ABNF "SP").
	Formally, using the HTTP specification's ABNF extensions defined in		Formally, using the HTTP specification's ABNF extensions defined in
	Section 7 of [RFC7230]:		Section 7 of [RFC7230]:
	json-field-value = #json-field-item		json-field-value = #json-field-item
	json-field-item = JSON-Text		json-field-item = JSON-Text
	; see [RFC7159], Section 2,		; see [RFC7159], Section 2,
	; post-processed so that only VCHAR characters		; post-processed so that only VCHAR characters
	; are used		; are used
	3. Sender Requirements		3. Sender Requirements
	[[anchor3: The text below assumes we're starting with a JSON-		To map a JSON array to an HTTP header field value, process each array
	formatted sequence of characters, not octets; need to clarify.]] To
	map a JSON array to an HTTP header field value, process each array
	element separately by:		element separately by:
	1. generating the JSON representation,		1. generating the JSON representation,
	2. stripping all JSON control characters (CR, HTAB, LF), or		2. stripping all JSON control characters (CR, HTAB, LF), or
	replacing them by space ("SP") characters,		replacing them by space ("SP") characters,
	3. replacing all remaining non-VSPACE characters by the equivalent		3. replacing all remaining non-VSPACE characters by the equivalent
	backslash-escape sequence ([RFC7159], Section 7).		backslash-escape sequence ([RFC7159], Section 7).
	The resulting list of strings is transformed into an HTTP field value		The resulting list of strings is transformed into an HTTP field value
	by combining them using comma (%x2C) plus optional SP as delimiter,		by combining them using comma (%x2C) plus optional SP as delimiter,
	and encoding the resulting string into an octet sequence using the		and encoding the resulting string into an octet sequence using the
	US-ASCII character encoding scheme.		US-ASCII character encoding scheme ([RFC0020]).
	4. Recipient Requirements		4. Recipient Requirements
	To map a set of HTTP header field instances to a JSON array:		To map a set of HTTP header field instances to a JSON array:
	1. remove all header field instances that only contain whitespace		1. combine all header field instances into a single field as per
	(SP / HTAB) and "comma" characters [[anchor5: either drop this or
	make it more precise]],
	2. combine all header field instances into a single field as per
	Section 3.2.2 of [RFC7230],		Section 3.2.2 of [RFC7230],
	3. add a leading begin-array ("[") octet and a trailing end-array		2. add a leading begin-array ("[") octet and a trailing end-array
	("]") octet, then		("]") octet, then
	4. run the resulting octet sequence through a JSON parser.		3. run the resulting octet sequence through a JSON parser.
	The result of the parsing operation is either an error (in which case		The result of the parsing operation is either an error (in which case
	the header field values needs to be considered invalid), or a JSON		the header field values needs to be considered invalid), or a JSON
	array.		array.
	5. Using this Format in Header Field Definitions		5. Using this Format in Header Field Definitions
	[[anchor7: Explain what a definition of a new header field needs to		[[anchor5: Explain what a definition of a new header field needs to
	do precisely to use this format]]		do precisely to use this format]]
	6. Examples		6. Examples
	This section shows how some of the existing HTTP header fields would		This section shows how some of the existing HTTP header fields would
	look like if they would use the format defined by this specification.		look like if they would use the format defined by this specification.
	6.1. Content-Length		6.1. Content-Length
	"Content-Length" is defined in Section 3.3.2 of [RFC7230], with the		"Content-Length" is defined in Section 3.3.2 of [RFC7230], with the
	skipping to change at page 8, line 14 ¶		skipping to change at page 8, line 8 ¶
	7. Discussion		7. Discussion
	This approach uses a default of "JSON array", using implicit array		This approach uses a default of "JSON array", using implicit array
	markers. An alternative would be a default of "JSON object". This		markers. An alternative would be a default of "JSON object". This
	would simplify the syntax for non-list-typed haeders, but all the		would simplify the syntax for non-list-typed haeders, but all the
	benefits of having the same data model for both types of header		benefits of having the same data model for both types of header
	fields would be gone. A hybrid approach might make sense, as long as		fields would be gone. A hybrid approach might make sense, as long as
	it doesn't require any heuristics on the recipient's side.		it doesn't require any heuristics on the recipient's side.
	[[anchor9: Use of generic libs vs compactness of field values..]]		[[anchor7: Use of generic libs vs compactness of field values..]]
	8. Deployment Considerations		8. Deployment Considerations
	[[anchor11: Mention that some code might be refused by double quotes		This JSON-based syntax will only apply to newly introduced header
	not being used for quoted-string.]]		fields, thus backwards compatibility is not a problem. That being
			said, it is conceivable that there is existing code that might trip
			over double quotes not being used for HTTP's quoted-string syntax
			(Section 3.2.6 of [RFC7230]).
	9. Internationalization Considerations		9. Internationalization Considerations
	[[anchor13: TBD, mention migration path to message format that is		[[anchor10: TBD, mention migration path to message format that is
	robust wrt UTF-8, or other binary encodings of JSON]]		robust wrt UTF-8, or other binary encodings of JSON]]
	10. Security Considerations		10. Security Considerations
	[[anchor15: TBD]]		[[anchor12: TBD]]
	11. References		11. References
	11.1. Normative References		11.1. Normative References
			[RFC0020] Cerf, V., "ASCII format for network interchange",
			STD 80, RFC 20, October 1969.
	[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for		[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for
	Syntax Specifications: ABNF", STD 68, RFC 5234,		Syntax Specifications: ABNF", STD 68, RFC 5234,
	January 2008.		January 2008.
	[RFC7159] Bray, T., "The JavaScript Object Notation (JSON)		[RFC7159] Bray, T., "The JavaScript Object Notation (JSON)
	Data Interchange Format", RFC 7159, March 2014.		Data Interchange Format", RFC 7159, March 2014.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext		[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
	Transfer Protocol (HTTP/1.1): Message Syntax and		Transfer Protocol (HTTP/1.1): Message Syntax and
	Routing", RFC 7230, June 2014.		Routing", RFC 7230, June 2014.
	[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext		[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
	Transfer Protocol (HTTP/1.1): Semantics and		Transfer Protocol (HTTP/1.1): Semantics and
	Content", RFC 7231, June 2014.		Content", RFC 7231, June 2014.
	[USASCII] American National Standards Institute, "Coded
	Character Set -- 7-bit American Standard Code for
	Information Interchange", ANSI X3.4, 1986.
	11.2. Informative References		11.2. Informative References
	[ISO-8859-1] International Organization for Standardization,		[ISO-8859-1] International Organization for Standardization,
	"Information technology -- 8-bit single-byte coded		"Information technology -- 8-bit single-byte coded
	graphic character sets -- Part 1: Latin alphabet		graphic character sets -- Part 1: Latin alphabet
	No. 1", ISO/IEC 8859-1:1998, 1998.		No. 1", ISO/IEC 8859-1:1998, 1998.
	[RFC5987] Reschke, J., "Character Set and Language Encoding		[RFC5987] Reschke, J., "Character Set and Language Encoding
	for Hypertext Transfer Protocol (HTTP) Header Field		for Hypertext Transfer Protocol (HTTP) Header Field
	Parameters", RFC 5987, August 2010.		Parameters", RFC 5987, August 2010.
	skipping to change at page 9, line 43 ¶		skipping to change at page 9, line 43 ¶
	Latest version available at		Latest version available at
	<http://www.w3.org/TR/XMLHttpRequest/>.		<http://www.w3.org/TR/XMLHttpRequest/>.
	URIs		URIs
	[1] <mailto:ietf-http-wg@w3.org>		[1] <mailto:ietf-http-wg@w3.org>
	[2] <mailto:ietf-http-wg-request@w3.org?subject=subscribe>		[2] <mailto:ietf-http-wg-request@w3.org?subject=subscribe>
	Appendix A. Sample Code and Test Cases		Appendix A. Change Log (to be removed by RFC Editor before publication)
	[[anchor19: TBD]]		A.1. draft-reschke-http-jfv-00
			Editorial fixes + working on the TODOs.
	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. 24 change blocks.
	34 lines changed or deleted		34 lines changed or added
This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/