< draft-ietf-httpbis-header-structure-10.txt   draft-ietf-httpbis-header-structure-11.txt >
HTTP M. Nottingham HTTP M. Nottingham
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track P-H. Kamp Intended status: Standards Track P-H. Kamp
Expires: October 19, 2019 The Varnish Cache Project Expires: January 9, 2020 The Varnish Cache Project
April 17, 2019 July 8, 2019
Structured Headers for HTTP Structured Headers for HTTP
draft-ietf-httpbis-header-structure-10 draft-ietf-httpbis-header-structure-11
Abstract Abstract
This document describes a set of data types and algorithms associated This document describes a set of data types and associated algorithms
with them that are intended to make it easier and safer to define and that are intended to make it easier and safer to define and handle
handle HTTP header fields. It is intended for use by new HTTP header fields. It is intended for use by specifications of new
specifications of HTTP header fields as well as revisions of existing HTTP header fields that wish to use a common syntax that is more
header field specifications when doing so does not cause restrictive than traditional HTTP field values.
interoperability issues.
Note to Readers Note to Readers
_RFC EDITOR: please remove this section before publication_ _RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP 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/ [1]. https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].
Working Group information can be found at https://httpwg.github.io/ Working Group information can be found at https://httpwg.github.io/
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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 https://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 October 19, 2019. This Internet-Draft will expire on January 9, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
(https://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
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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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Intentionally Strict Processing . . . . . . . . . . . . . 4 1.1. Intentionally Strict Processing . . . . . . . . . . . . . 4
1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Defining New Structured Headers . . . . . . . . . . . . . . . 5 2. Defining New Structured Headers . . . . . . . . . . . . . . . 5
3. Structured Header Data Types . . . . . . . . . . . . . . . . 7 3. Structured Header Data Types . . . . . . . . . . . . . . . . 6
3.1. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Lists of Lists . . . . . . . . . . . . . . . . . . . . . 8 3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.4. Parameterised Lists . . . . . . . . . . . . . . . . . . . 8 3.4. Integers . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.5. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6. Integers . . . . . . . . . . . . . . . . . . . . . . . . 9 3.6. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.7. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.7. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.8. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.8. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 10
3.9. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.9. Booleans . . . . . . . . . . . . . . . . . . . . . . . . 11
3.10. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 11 4. Working With Structured Headers in Textual HTTP Headers . . . 11
3.11. Booleans . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Serializing Structured Headers . . . . . . . . . . . . . 11
4. Structured Headers in HTTP/1 . . . . . . . . . . . . . . . . 12 4.2. Parsing Header Fields into Structured Headers . . . . . . 17
4.1. Serialising Structured Headers into HTTP/1 . . . . . . . 12 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
4.2. Parsing HTTP/1 Header Fields into Structured Headers . . 18 6. Security Considerations . . . . . . . . . . . . . . . . . . . 26
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
6. Security Considerations . . . . . . . . . . . . . . . . . . . 28 7.1. Normative References . . . . . . . . . . . . . . . . . . 26
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.2. Informative References . . . . . . . . . . . . . . . . . 27
7.1. Normative References . . . . . . . . . . . . . . . . . . 28 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.2. Informative References . . . . . . . . . . . . . . . . . 29 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 28
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 28
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 30 B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 28
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 30 B.2. Structured Headers don't "fit" my data. . . . . . . . . . 29
B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 30 Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 29
B.2. Structured Headers don't "fit" my data. . . . . . . . . . 30 Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 30
B.3. What should generic Structured Headers implementations D.1. Since draft-ietf-httpbis-header-structure-10 . . . . . . 30
expose? . . . . . . . . . . . . . . . . . . . . . . . . . 31 D.2. Since draft-ietf-httpbis-header-structure-09 . . . . . . 30
Appendix C. Changes . . . . . . . . . . . . . . . . . . . . . . 31 D.3. Since draft-ietf-httpbis-header-structure-08 . . . . . . 31
C.1. Since draft-ietf-httpbis-header-structure-09 . . . . . . 31 D.4. Since draft-ietf-httpbis-header-structure-07 . . . . . . 31
C.2. Since draft-ietf-httpbis-header-structure-08 . . . . . . 32 D.5. Since draft-ietf-httpbis-header-structure-06 . . . . . . 32
C.3. Since draft-ietf-httpbis-header-structure-07 . . . . . . 32 D.6. Since draft-ietf-httpbis-header-structure-05 . . . . . . 32
C.4. Since draft-ietf-httpbis-header-structure-06 . . . . . . 33 D.7. Since draft-ietf-httpbis-header-structure-04 . . . . . . 32
C.5. Since draft-ietf-httpbis-header-structure-05 . . . . . . 33 D.8. Since draft-ietf-httpbis-header-structure-03 . . . . . . 32
C.6. Since draft-ietf-httpbis-header-structure-04 . . . . . . 33 D.9. Since draft-ietf-httpbis-header-structure-02 . . . . . . 32
C.7. Since draft-ietf-httpbis-header-structure-03 . . . . . . 33 D.10. Since draft-ietf-httpbis-header-structure-01 . . . . . . 33
C.8. Since draft-ietf-httpbis-header-structure-02 . . . . . . 33 D.11. Since draft-ietf-httpbis-header-structure-00 . . . . . . 33
C.9. Since draft-ietf-httpbis-header-structure-01 . . . . . . 34 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
C.10. Since draft-ietf-httpbis-header-structure-00 . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
Specifying the syntax of new HTTP header fields is an onerous task; Specifying the syntax of new HTTP header fields is an onerous task;
even with the guidance in [RFC7231], Section 8.3.1, there are many even with the guidance in [RFC7231], Section 8.3.1, there are many
decisions - and pitfalls - for a prospective HTTP header field decisions - and pitfalls - for a prospective HTTP header field
author. author.
Once a header field is defined, bespoke parsers and serialisers often Once a header field is defined, bespoke parsers and serializers often
need to be written, because each header has slightly different need to be written, because each header has slightly different
handling of what looks like common syntax. handling of what looks like common syntax.
This document introduces a set of common data structures for use in This document introduces a set of common data structures for use in
HTTP header field values to address these problems. In particular, definitions of new HTTP header field values to address these
it defines a generic, abstract model for header field values, along problems. In particular, it defines a generic, abstract model for
with a concrete serialisation for expressing that model in HTTP/1 header field values, along with a concrete serialisation for
[RFC7230] header fields. expressing that model in textual HTTP [RFC7230] header fields.
HTTP headers that are defined as "Structured Headers" use the types HTTP headers that are defined as "Structured Headers" use the types
defined in this specification to define their syntax and basic defined in this specification to define their syntax and basic
handling rules, thereby simplifying both their definition by handling rules, thereby simplifying both their definition by
specification writers and handling by implementations. specification writers and handling by implementations.
Additionally, future versions of HTTP can define alternative Additionally, future versions of HTTP can define alternative
serialisations of the abstract model of these structures, allowing serialisations of the abstract model of these structures, allowing
headers that use it to be transmitted more efficiently without being headers that use it to be transmitted more efficiently without being
redefined. redefined.
Note that it is not a goal of this document to redefine the syntax of Note that it is not a goal of this document to redefine the syntax of
existing HTTP headers; the mechanisms described herein are only existing HTTP headers; the mechanisms described herein are only
intended to be used with headers that explicitly opt into them. intended to be used with headers that explicitly opt into them.
To specify a header field that is a Structured Header, see Section 2. Section 2 describes how to specify a Structured Header.
Section 3 defines a number of abstract data types that can be used in Section 3 defines a number of abstract data types that can be used in
Structured Headers. Structured Headers. Those abstract types can be serialized into and
parsed from textual HTTP headers using the algorithms described in
Those abstract types can be serialised into and parsed from textual Section 4.
headers - such as those used in HTTP/1 - using the algorithms
described in Section 4.
1.1. Intentionally Strict Processing 1.1. Intentionally Strict Processing
This specification intentionally defines strict parsing and This specification intentionally defines strict parsing and
serialisation behaviours using step-by-step algorithms; the only serialisation behaviours using step-by-step algorithms; the only
error handling defined is to fail the operation altogether. error handling defined is to fail the operation altogether.
This is designed to encourage faithful implementation and therefore It is designed to encourage faithful implementation and therefore
good interoperability. Therefore, implementations that try to be good interoperability. Therefore, an implementation that tried to be
"helpful" by being more tolerant of input are doing a disservice to "helpful" by being more tolerant of input would make interoperability
the overall community, since it will encourage other implementations worse, since that would create pressure on other implementations to
to implement similar (but likely subtly different) workarounds. implement similar (but likely subtly different) workarounds.
In other words, strict processing is an intentional feature of this In other words, strict processing is an intentional feature of this
specification; it allows non-conformant input to be discovered and specification; it allows non-conformant input to be discovered and
corrected early, and avoids both interoperability and security issues corrected by the producer early, and avoids both interoperability and
that might otherwise result. security issues that might otherwise result.
Note that as a result of this strictness, if a header field is Note that as a result of this strictness, if a header field is
appended to by multiple parties (e.g., intermediaries, or different appended to by multiple parties (e.g., intermediaries, or different
components in the sender), it could be that an error in one party's components in the sender), an error in one party's value is likely to
value causes the entire header field to fail parsing. cause the entire header field to fail parsing.
1.2. Notational Conventions 1.2. 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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This document uses the Augmented Backus-Naur Form (ABNF) notation of
[RFC5234], including the VCHAR, SP, DIGIT, ALPHA and DQUOTE rules
from that document. It also includes the OWS rule from [RFC7230].
This document uses algorithms to specify parsing and serialisation This document uses algorithms to specify parsing and serialisation
behaviours, and ABNF to illustrate expected syntax in HTTP/1-style behaviours, and the Augmented Backus-Naur Form (ABNF) notation of
header fields. [RFC5234] to illustrate expected syntax in textual HTTP header
fields. In doing so, uses the VCHAR, SP, DIGIT, ALPHA and DQUOTE
rules from [RFC5234]. It also includes the OWS rule from [RFC7230].
For parsing from HTTP/1 header fields, implementations MUST follow When parsing from textual HTTP header fields, implementations MUST
the algorithms, but MAY vary in implementation so as the behaviours follow the algorithms, but MAY vary in implementation so as the
are indistinguishable from specified behaviour. If there is behaviours are indistinguishable from specified behaviour. If there
disagreement between the parsing algorithms and ABNF, the specified is disagreement between the parsing algorithms and ABNF, the
algorithms take precedence. In some places, the algorithms are specified algorithms take precedence. In some places, the algorithms
"greedy" with whitespace, but this should not affect conformance. are "greedy" with whitespace, but this should not affect conformance.
For serialisation to HTTP/1 header fields, the ABNF illustrates the For serialisation to textual header fields, the ABNF illustrates the
range of acceptable wire representations with as much fidelity as range of acceptable wire representations with as much fidelity as
possible, and the algorithms define the recommended way to produce possible, and the algorithms define the recommended way to produce
them. Implementations MAY vary from the specified behaviour so long them. Implementations MAY vary from the specified behaviour so long
as the output still matches the ABNF. as the output still matches the ABNF.
2. Defining New Structured Headers 2. Defining New Structured Headers
To define a HTTP header as a structured header, its specification To define a HTTP header as a structured header, its specification
needs to: needs to:
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semantics. Syntax definitions are encouraged to use the ABNF semantics. Syntax definitions are encouraged to use the ABNF
rules beginning with "sh-" defined in this specification. rules beginning with "sh-" defined in this specification.
o Specify any additional constraints upon the syntax of the o Specify any additional constraints upon the syntax of the
structured used, as well as the consequences when those structured used, as well as the consequences when those
constraints are violated. When Structured Headers parsing fails, constraints are violated. When Structured Headers parsing fails,
the header is discarded (see Section 4.2); in most situations, the header is discarded (see Section 4.2); in most situations,
header-specific constraints should do likewise. header-specific constraints should do likewise.
Note that a header field definition cannot relax the requirements of Note that a header field definition cannot relax the requirements of
a structure or its processing because doing so would preclude this specification because doing so would preclude handling by
handling by generic software; they can only add additional generic software; they can only add additional constraints (for
constraints. Likewise, header field definitions should use example, on the numeric range of integers and floats, the format of
Structured Headers for the entire header field value, not a portion strings and tokens, or the number of items in a list). Likewise,
thereof. header field definitions should use Structured Headers for the entire
header field value, not a portion thereof.
For example: This specification defines minimums for the length or number of
various structures supported by Structured Headers implementations.
It does not specify maximum sizes in most cases, but header authors
should be aware that HTTP implementations do impose various limits on
the size of individual header fields, the total number of fields,
and/or the size of the entire header block.
# Foo-Example Header For example,
42. Foo-Example Header
The Foo-Example HTTP header field conveys information about how The Foo-Example HTTP header field conveys information about how
much Foo the message has. much Foo the message has.
Foo-Example is a Structured Header [RFCxxxx]. Its value MUST be a Foo-Example is a Structured Header [RFCxxxx]. Its value MUST be a
dictionary ([RFCxxxx], Section Y.Y). Its ABNF is: dictionary ([RFCxxxx], Section Y.Y). Its ABNF is:
Foo-Example = sh-dictionary Foo-Example = sh-dictionary
The dictionary MUST contain: The dictionary MUST contain:
* Exactly one member whose key is "foo", and whose value is an * Exactly one member whose name is "foo", and whose value is an
integer ([RFCxxxx], Section Y.Y), indicating the number of foos integer ([RFCxxxx], Section Y.Y), indicating the number of foos
in the message. in the message.
* Exactly one member whose key is "barUrls", and whose value is a * Exactly one member whose name is "barUrl", and whose value is a
string ([RFCxxxx], Section Y.Y), conveying the Bar URLs for the string ([RFCxxxx], Section Y.Y), conveying the Bar URL for the
message. See below for processing requirements. message. See below for processing requirements.
If the parsed header field does not contain both, it MUST be If the parsed header field does not contain both, it MUST be
ignored. ignored.
"foo" MUST be between 0 and 10, inclusive; other values MUST cause "foo" MUST be between 0 and 10, inclusive; other values MUST cause
the header to be ignored. the header to be ignored.
"barUrls" contains a space-separated list of URI-references "barUrl" contains a URI-reference ([RFC3986], Section 4.1).
([RFC3986], Section 4.1):
barURLs = URI-reference *( 1*SP URI-reference )
If a member of barURLs is not a valid URI-reference, it MUST cause
that value to be ignored.
If a member of barURLs is a relative reference ([RFC3986],
Section 4.2), it MUST be resolved ([RFC3986], Section 5) before
being used.
This specification defines minimums for the length or number of If barURL is not a valid URI-reference, it MUST be ignored.
various structures supported by Structured Headers implementations. If barURL is a relative reference ([RFC3986], Section 4.2),
It does not specify maximum sizes in most cases, but header authors it MUST be resolved ([RFC3986], Section 5) before being used.
should be aware that HTTP implementations do impose various limits on
the size of individual header fields, the total number of fields,
and/or the size of the entire header block.
3. Structured Header Data Types 3. Structured Header Data Types
This section defines the abstract value types that can be composed This section defines the abstract value types that can be composed
into Structured Headers. The ABNF provided represents the on-wire into Structured Headers. The ABNF provided represents the on-wire
format in HTTP/1. format in HTTP.
3.1. Dictionaries
Dictionaries are ordered maps of key-value pairs, where the keys are
short, textual strings and the values are items (Section 3.5). There
can be one or more members, and keys are required to be unique.
Implementations MUST provide access to dictionaries both by index and
by key. Specifications MAY use either means of accessing the
members.
The ABNF for dictionaries in HTTP/1 headers is:
sh-dictionary = dict-member *( OWS "," OWS dict-member )
dict-member = member-name "=" member-value
member-name = key
member-value = sh-item
key = lcalpha *( lcalpha / DIGIT / "_" / "-" )
lcalpha = %x61-7A ; a-z
In HTTP/1, keys and values are separated by "=" (without whitespace),
and key/value pairs are separated by a comma with optional
whitespace. For example:
Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=*
Typically, a header field specification will define the semantics of 3.1. Lists
individual keys, as well as whether their presence is required or
optional. Recipients MUST ignore keys that are undefined or unknown,
unless the header field's specification specifically disallows them.
Parsers MUST support dictionaries containing at least 1024 key/value Lists are arrays of zero or more members, each of which can be an
pairs, and dictionary keys with at least 64 characters. item (Section 3.3) or an inner list (an array of zero or more items).
3.2. Lists Each member of the top-level list can also have associated parameters
- an ordered map of key-value pairs where the keys are short, textual
strings and the values are items (Section 3.3). There can be zero or
more parameters on a member, and their keys are required to be unique
within that scope.
Lists are arrays of items (Section 3.5) with one or more members. The ABNF for lists is:
The ABNF for lists in HTTP/1 headers is: sh-list = list-member *( OWS "," OWS list-member )
list-member = ( sh-item / inner-list ) *parameter
inner-list = "(" OWS [ sh-item *( SP sh-item ) OWS ] ")"
parameter = OWS ";" OWS param-name [ "=" param-value ]
param-name = key
key = lcalpha *( lcalpha / DIGIT / "_" / "-" )
lcalpha = %x61-7A ; a-z
param-value = sh-item
sh-list = list-member *( OWS "," OWS list-member ) In textual HTTP headers, each member is separated by a comma and
list-member = sh-item optional whitespace. For example, a header field whose value is
In HTTP/1, each member is separated by a comma and optional defined as a list of strings could look like:
whitespace. For example, a header field whose value is defined as a
list of strings could look like:
Example-StrListHeader: "foo", "bar", "It was the best of times." Example-StrListHeader: "foo", "bar", "It was the best of times."
Header specifications can constrain the types of individual values if In textual HTTP headers, inner lists are denoted by surrounding
necessary. parenthesis, and have their values delimited by a single space. A
header field whose value is defined as a list of lists of strings
could look like:
Parsers MUST support lists containing at least 1024 members. Example-StrListListHeader: ("foo" "bar"), ("baz"), ("bat" "one"), ()
3.3. Lists of Lists Note that the last member in this example is an empty inner list.
Lists of Lists are arrays of arrays containing items (Section 3.5). In textual HTTP headers, members' parameters are separated from the
member and each other by semicolons. For example:
The ABNF for lists of lists in HTTP/1 headers is: Example-ParamListHeader: abc_123;a=1;b=2; cdef_456, (ghi jkl);q="9";r="w"
sh-listlist = inner-list *( OWS "," OWS inner-list ) Parsers MUST support lists containing at least 1024 members, support
inner-list = list-member *( OWS ";" OWS list-member ) members with at least 256 parameters, support inner-lists containing
at least 256 members, and support parameter keys with at least 64
characters.
In HTTP/1, each inner-list is separated by a comma and optional Header specifications can constrain the types of individual list
whitespace, and members of the inner-list are separated by semicolons values (including that of individual inner-list members and
and optional whitespace. For example, a header field whose value is parameters) if necessary.
defined as a list of lists of strings could look like:
Example-StrListListHeader: "foo";"bar", "baz", "bat"; "one" 3.2. Dictionaries
Header specifications can constrain the types of individual inner- Dictionaries are ordered maps of name-value pairs, where the names
list values if necessary. are short, textual strings and the values are items (Section 3.3) or
arrays of items. There can be zero or more members, and their names
are required to be unique within the scope of the dictionary they
occur within.
Parsers MUST support lists of lists containing at least 1024 members, Implementations MUST provide access to dictionaries both by index and
and inner-lists containing at least 256 members. by name. Specifications MAY use either means of accessing the
members.
3.4. Parameterised Lists The ABNF for dictionaries in textual HTTP headers is:
Parameterised Lists are arrays of parameterised identifiers, with one sh-dictionary = dict-member *( OWS "," OWS dict-member )
or more members. dict-member = member-name "=" member-value
member-name = key
member-value = sh-item / inner-list
A parameterised identifier is a primary identifier (a Section 3.9}) In textual HTTP headers, members are separated by a comma with
with associated parameters, an ordered map of key-value pairs where optional whitespace, while names and values are separated by "="
the keys are short, textual strings and the values are items (without whitespace). For example:
(Section 3.5). There can be zero or more parameters, and keys are
required to be unique.
The ABNF for parameterised lists in HTTP/1 headers is: Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=*
sh-param-list = param-item *( OWS "," OWS param-item ) A dictionary with a member whose value is an inner-list of tokens:
param-item = primary-id *parameter
primary-id = sh-token
parameter = OWS ";" OWS param-name [ "=" param-value ]
param-name = key
param-value = sh-item
In HTTP/1, each param-id is separated by a comma and optional Example-DictListHeader: rating=1.5, feelings=(joy sadness)
whitespace (as in Lists), and the parameters are separated by
semicolons. For example:
Example-ParamListHeader: abc_123;a=1;b=2; cdef_456, ghi;q="9";r="w" Typically, a header field specification will define the semantics of
individual member names, as well as whether their presence is
required or optional. Recipients MUST ignore names that are
undefined or unknown, unless the header field's specification
specifically disallows them.
Parsers MUST support parameterised lists containing at least 1024 Parsers MUST support dictionaries containing at least 1024 name/value
members, support members with at least 256 parameters, and support pairs, and names with at least 64 characters.
parameter keys with at least 64 characters.
3.5. Items 3.3. Items
An item is can be a integer (Section 3.6), float (Section 3.7), An item is can be a integer (Section 3.4), float (Section 3.5),
string (Section 3.8), token (Section 3.9), byte sequence string (Section 3.6), token (Section 3.7), byte sequence
(Section 3.10), or Boolean (Section 3.11). (Section 3.8), or Boolean (Section 3.9).
The ABNF for items in HTTP/1 headers is: The ABNF for items in textual HTTP headers is:
sh-item = sh-integer / sh-float / sh-string / sh-token / sh-binary sh-item = sh-integer / sh-float / sh-string / sh-token / sh-binary
/ sh-boolean / sh-boolean
3.6. Integers 3.4. Integers
Integers have a range of -999,999,999,999,999 to 999,999,999,999,999 Integers have a range of -999,999,999,999,999 to 999,999,999,999,999
inclusive (i.e., up to fifteen digits, signed). inclusive (i.e., up to fifteen digits, signed), for IEEE 754
compatibility ([IEEE754]).
The ABNF for integers in HTTP/1 headers is: The ABNF for integers in textual HTTP headers is:
sh-integer = ["-"] 1*15DIGIT sh-integer = ["-"] 1*15DIGIT
For example: For example:
Example-IntegerHeader: 42 Example-IntegerHeader: 42
3.7. Floats Note that commas in integers are used in this section's prose only
for readability; they are not valid in the wire format.
3.5. Floats
Floats are integers with a fractional part, that can be stored as Floats are integers with a fractional part, that can be stored as
IEEE 754 double precision numbers (binary64) ([IEEE754]). IEEE 754 double precision numbers (binary64) ([IEEE754]).
The ABNF for floats in HTTP/1 headers is: The ABNF for floats in textual HTTP headers is:
sh-float = ["-"] ( sh-float = ["-"] (
DIGIT "." 1*14DIGIT / DIGIT "." 1*14DIGIT /
2DIGIT "." 1*13DIGIT / 2DIGIT "." 1*13DIGIT /
3DIGIT "." 1*12DIGIT / 3DIGIT "." 1*12DIGIT /
4DIGIT "." 1*11DIGIT / 4DIGIT "." 1*11DIGIT /
5DIGIT "." 1*10DIGIT / 5DIGIT "." 1*10DIGIT /
6DIGIT "." 1*9DIGIT / 6DIGIT "." 1*9DIGIT /
7DIGIT "." 1*8DIGIT / 7DIGIT "." 1*8DIGIT /
8DIGIT "." 1*7DIGIT / 8DIGIT "." 1*7DIGIT /
skipping to change at page 10, line 26 skipping to change at page 9, line 42
11DIGIT "." 1*4DIGIT / 11DIGIT "." 1*4DIGIT /
12DIGIT "." 1*3DIGIT / 12DIGIT "." 1*3DIGIT /
13DIGIT "." 1*2DIGIT / 13DIGIT "." 1*2DIGIT /
14DIGIT "." 1DIGIT ) 14DIGIT "." 1DIGIT )
For example, a header whose value is defined as a float could look For example, a header whose value is defined as a float could look
like: like:
Example-FloatHeader: 4.5 Example-FloatHeader: 4.5
3.8. Strings 3.6. Strings
Strings are zero or more printable ASCII [RFC0020] characters (i.e., Strings are zero or more printable ASCII [RFC0020] characters (i.e.,
the range 0x20 to 0x7E). Note that this excludes tabs, newlines, the range 0x20 to 0x7E). Note that this excludes tabs, newlines,
carriage returns, etc. carriage returns, etc.
The ABNF for strings in HTTP/1 headers is: The ABNF for strings in textual HTTP headers is:
sh-string = DQUOTE *(chr) DQUOTE sh-string = DQUOTE *(chr) DQUOTE
chr = unescaped / escaped chr = unescaped / escaped
unescaped = %x20-21 / %x23-5B / %x5D-7E unescaped = %x20-21 / %x23-5B / %x5D-7E
escaped = "\" ( DQUOTE / "\" ) escaped = "\" ( DQUOTE / "\" )
In HTTP/1 headers, strings are delimited with double quotes, using a In textual HTTP headers, strings are delimited with double quotes,
backslash ("\") to escape double quotes and backslashes. For using a backslash ("\") to escape double quotes and backslashes. For
example: example:
Example-StringHeader: "hello world" Example-StringHeader: "hello world"
Note that strings only use DQUOTE as a delimiter; single quotes do Note that strings only use DQUOTE as a delimiter; single quotes do
not delimit strings. Furthermore, only DQUOTE and "\" can be not delimit strings. Furthermore, only DQUOTE and "\" can be
escaped; other sequences MUST cause parsing to fail. escaped; other sequences MUST cause parsing to fail.
Unicode is not directly supported in this document, because it causes Unicode is not directly supported in this document, because it causes
a number of interoperability issues, and - with few exceptions - a number of interoperability issues, and - with few exceptions -
header values do not require it. header values do not require it.
When it is necessary for a field value to convey non-ASCII string When it is necessary for a field value to convey non-ASCII string
content, a byte sequence (Section 3.10) SHOULD be specified, along content, a byte sequence (Section 3.8) SHOULD be specified, along
with a character encoding (preferably UTF-8). with a character encoding (preferably UTF-8).
Parsers MUST support strings with at least 1024 characters. Parsers MUST support strings with at least 1024 characters.
3.9. Tokens 3.7. Tokens
Tokens are short textual words; their abstract model is identical to Tokens are short textual words; their abstract model is identical to
their expression in the textual HTTP serialisation. their expression in the textual HTTP serialisation.
The ABNF for tokens in HTTP/1 headers is: The ABNF for tokens in textual HTTP headers is:
sh-token = ALPHA *( ALPHA / DIGIT / "_" / "-" / "." / ":" / "%" / "*" / "/" ) sh-token = ALPHA
*( ALPHA / DIGIT / "_" / "-" / "." / ":" / "%"
/ "*" / "/" )
Parsers MUST support tokens with at least 512 characters. Parsers MUST support tokens with at least 512 characters.
Note that a Structured Header token is not the same as the "token" Note that a Structured Header token is not the same as the "token"
ABNF rule defined in [RFC7230]. ABNF rule defined in [RFC7230].
3.10. Byte Sequences 3.8. Byte Sequences
Byte sequences can be conveyed in Structured Headers. Byte sequences can be conveyed in Structured Headers.
The ABNF for a byte sequence in HTTP/1 headers is: The ABNF for a byte sequence in textual HTTP headers is:
sh-binary = "*" *(base64) "*" sh-binary = "*" *(base64) "*"
base64 = ALPHA / DIGIT / "+" / "/" / "=" base64 = ALPHA / DIGIT / "+" / "/" / "="
In HTTP/1 headers, a byte sequence is delimited with asterisks and In textual HTTP headers, a byte sequence is delimited with asterisks
encoded using base64 ([RFC4648], Section 4). For example: and encoded using base64 ([RFC4648], Section 4). For example:
Example-BinaryHdr: *cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==* Example-BinaryHdr: *cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==*
Parsers MUST support byte sequences with at least 16384 octets after Parsers MUST support byte sequences with at least 16384 octets after
decoding. decoding.
3.11. Booleans 3.9. Booleans
Boolean values can be conveyed in Structured Headers. Boolean values can be conveyed in Structured Headers.
The ABNF for a Boolean in HTTP/1 headers is: The ABNF for a Boolean in textual HTTP headers is:
sh-boolean = "?" boolean sh-boolean = "?" boolean
boolean = "0" / "1" boolean = "0" / "1"
In HTTP/1 headers, a boolean is indicated with a leading "?" In textual HTTP headers, a boolean is indicated with a leading "?"
character. For example: character. For example:
Example-BoolHdr: ?1 Example-BoolHdr: ?1
4. Structured Headers in HTTP/1 4. Working With Structured Headers in Textual HTTP Headers
This section defines how to serialise and parse Structured Headers in This section defines how to serialize and parse Structured Headers in
HTTP/1 textual header fields, and protocols compatible with them textual header fields, and protocols compatible with them (e.g., in
(e.g., in HTTP/2 [RFC7540] before HPACK [RFC7541] is applied). HTTP/2 [RFC7540] before HPACK [RFC7541] is applied).
4.1. Serialising Structured Headers into HTTP/1 4.1. Serializing Structured Headers
Given a structured defined in this specification: Given a structure defined in this specification:
1. If the structure is a dictionary, return the result of 1. If the structure is a dictionary or list and its value is empty
Serialising a Dictionary (Section 4.1.1). (i.e., it has no members), do not send the serialize field at all
(i.e., omit both the field-name and field-value).
2. If the structure is a parameterised list, return the result of 2. If the structure is a dictionary, let output_string be the result
Serialising a Parameterised List (Section 4.1.4). of Serializing a Dictionary (Section 4.1.2).
3. If the structure is a list of lists, return the result of 3. Else if the structure is a list, let output_string be the result
Serialising a List of Lists ({ser-listlist}). of Serializing a List Section 4.1.1.
4. If the structure is a list, return the result of Serialising a 4. Else if the structure is an item, let output_string be the result
List Section 4.1.2. of Serializing an Item (Section 4.1.3).
5. If the structure is an item, return the result of Serialising an 5. Else, fail serialisation.
Item (Section 4.1.5).
6. Otherwise, fail serialisation. 6. Return output_string converted into an array of bytes, using
ASCII encoding [RFC0020].
4.1.1. Serialising a Dictionary 4.1.1. Serializing a List
Given a dictionary as input_dictionary: Given a list of (member, parameters) as input_list:
1. Let output be an empty string. 1. Let output be an empty string.
2. For each member mem of input_dictionary: 2. For each (member, parameters) of input_list:
1. Let name be the result of applying Serialising an Key
(Section 4.1.1.1) to mem's member-name.
2. Append name to output.
3. Append "=" to output.
4. Let value be the result of applying Serialising an Item
(Section 4.1.5) to mem's member-value.
5. Append value to output.
6. If more members remain in input_dictionary:
1. Append a COMMA to output.
2. Append a single WS to output.
3. Return output.
4.1.1.1. Serialising a Key
Given a key as input_key: 1. If member is an array, let mem_value be the result of
applying Serialising an Inner List (Section 4.1.1.1) to
member.
1. If input_key is not a sequence of characters, or contains 2. Otherwise, let mem_value be the result of applying
characters not allowed in the ABNF for key, fail serialisation. Serializing an Item (Section 4.1.3) to member.
2. Let output be an empty string. 3. Append mem_value to output.
3. Append input_key to output, using ASCII encoding [RFC0020]. 4. For each parameter in parameters:
4. Return output. 1. Append ";" to output.
4.1.2. Serialising a List 2. Let name be the result of applying Serializing a Key
(Section 4.1.1.2) to parameter's param-name.
Given a list as input_list: 3. Append name to output.
1. Let output be an empty string. 4. If parameter has a param-value:
2. For each member mem of input_list: 1. Let value be the result of applying Serializing an
Item (Section 4.1.3) to parameter's param-value.
1. Let value be the result of applying Serialising an Item 2. Append "=" to output.
(Section 4.1.5) to mem.
2. Append value to output. 3. Append value to output.
3. If more members remain in input_list: 5. If more members remain in input_plist:
1. Append a COMMA to output. 1. Append a COMMA to output.
2. Append a single WS to output. 2. Append a single WS to output.
3. Return output. 3. Return output.
4.1.3. Serialising a List of Lists 4.1.1.1. Serialising an Inner List
Given a list of lists of items as input_list:
1. Let output be an empty string. Given an array inner_list:
2. For each member inner_list of input_list: 1. Let output be the string "(".
1. If inner_list is not a list, fail serialisation. 2. For each member mem of inner_list:
2. If inner_list is empty, fail serialisation. 1. Let value be the result of applying Serializing an Item
(Section 4.1.3) to mem.
3. For each inner_mem of inner_list: 2. Append value to output.
1. Let value be the result of applying Serialising an Item 3. If inner_list is not empty, append a single WS to output.
(Section 4.1.5) to inner_mem.
2. Append value to output. 3. Append ")" to output.
3. If more members remain in inner_list: 4. Return output.
1. Append a ";" to output. 4.1.1.2. Serializing a Key
2. Append a single WS to output. Given a key as input_key:
4. If more members remain in input_list: 1. If input_key is not a sequence of characters, or contains
characters not allowed in the ABNF for key, fail serialisation.
1. Append a COMMA to output. 2. Let output be an empty string.
2. Append a single WS to output. 3. Append input_key to output.
3. Return output. 4. Return output.
4.1.4. Serialising a Parameterised List 4.1.2. Serializing a Dictionary
Given a parameterised list as input_plist: Given a dictionary as input_dictionary:
1. Let output be an empty string. 1. Let output be an empty string.
2. For each member mem of input_plist: 2. For each member mem of input_dictionary:
1. Let id be the result of applying Serialising a Token
(Section 4.1.9) to mem's token.
2. Append id to output.
3. For each parameter in mem's parameters:
1. Append ";" to output.
2. Let name be the result of applying Serialising a Key 1. Let name be the result of applying Serializing a Key
(Section 4.1.1.1) to parameter's param-name. (Section 4.1.1.2) to mem's member-name.
3. Append name to output. 2. Append name to output.
4. If parameter has a param-value: 3. Append "=" to output.
1. Let value be the result of applying Serialising an 4. If mem is an array, let value be the result of applying
Item (Section 4.1.5) to parameter's param-value. Serialising an Inner List (Section 4.1.1.1) to mem.
2. Append "=" to output. 5. Otherwise, let value be the result of applying Serializing an
Item (Section 4.1.3) to mem.
3. Append value to output. 6. Append value to output.
4. If more members remain in input_plist: 7. If more members remain in input_dictionary:
1. Append a COMMA to output. 1. Append a COMMA to output.
2. Append a single WS to output. 2. Append a single WS to output.
3. Return output. 3. Return output.
4.1.5. Serialising an Item 4.1.3. Serializing an Item
Given an item as input_item: Given an item as input_item:
1. If input_item is an integer, return the result of applying 1. If input_item is an integer, return the result of applying
Serialising an Integer (Section 4.1.6) to input_item. Serializing an Integer (Section 4.1.4) to input_item.
2. If input_item is a float, return the result of applying 2. If input_item is a float, return the result of applying
Serialising a Float (Section 4.1.7) to input_item. Serializing a Float (Section 4.1.5) to input_item.
3. If input_item is a string, return the result of applying 3. If input_item is a string, return the result of applying
Serialising a String (Section 4.1.8) to input_item. Serializing a String (Section 4.1.6) to input_item.
4. If input_item is a token, return the result of Serialising a 4. If input_item is a token, return the result of Serializing a
Token (Section 4.1.9) to input_item. Token (Section 4.1.7) to input_item.
5. If input_item is a Boolean, return the result of applying 5. If input_item is a Boolean, return the result of applying
Serialising a Boolean (Section 4.1.11) to input_item. Serializing a Boolean (Section 4.1.9) to input_item.
6. If input_item is a byte sequence, return the result of applying 6. If input_item is a byte sequence, return the result of applying
Serialising a Byte Sequence (Section 4.1.10) to input_item. Serializing a Byte Sequence (Section 4.1.8) to input_item.
7. Otherwise, fail serialisation. 7. Otherwise, fail serialisation.
4.1.6. Serialising an Integer 4.1.4. Serializing an Integer
Given an integer as input_integer: Given an integer as input_integer:
1. If input_integer is not an integer in the range of 1. If input_integer is not an integer in the range of
-999,999,999,999,999 to 999,999,999,999,999 inclusive, fail -999,999,999,999,999 to 999,999,999,999,999 inclusive, fail
serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. If input_integer is less than (but not equal to) 0, append "-" to 3. If input_integer is less than (but not equal to) 0, append "-" to
output. output.
4. Append input_integer's numeric value represented in base 10 using 4. Append input_integer's numeric value represented in base 10 using
only decimal digits to output. only decimal digits to output.
5. Return output. 5. Return output.
4.1.7. Serialising a Float 4.1.5. Serializing a Float
Given a float as input_float: Given a float as input_float:
1. If input_float is not a IEEE 754 double precision number, fail 1. If input_float is not a IEEE 754 double precision number, fail
serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. If input_float is less than (but not equal to) 0, append "-" to 3. If input_float is less than (but not equal to) 0, append "-" to
output. output.
skipping to change at page 16, line 37 skipping to change at page 15, line 37
4. Append input_float's integer component represented in base 10 4. Append input_float's integer component represented in base 10
using only decimal digits to output; if it is zero, append "0". using only decimal digits to output; if it is zero, append "0".
5. Append "." to output. 5. Append "." to output.
6. Append input_float's decimal component represented in base 10 6. Append input_float's decimal component represented in base 10
using only decimal digits to output; if it is zero, append "0". using only decimal digits to output; if it is zero, append "0".
7. Return output. 7. Return output.
4.1.8. Serialising a String 4.1.6. Serializing a String
Given a string as input_string: Given a string as input_string:
1. If input_string is not a sequence of characters, or contains 1. If input_string is not a sequence of characters, or contains
characters outside the range allowed by VCHAR or SP, fail characters outside the range allowed by VCHAR or SP, fail
serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append DQUOTE to output. 3. Append DQUOTE to output.
4. For each character char in input_string: 4. For each character char in input_string:
1. If char is "\" or DQUOTE: 1. If char is "\" or DQUOTE:
1. Append "\" to output. 1. Append "\" to output.
2. Append char to output, using ASCII encoding [RFC0020]. 2. Append char to output.
5. Append DQUOTE to output. 5. Append DQUOTE to output.
6. Return output. 6. Return output.
4.1.9. Serialising a Token 4.1.7. Serializing a Token
Given a token as input_token: Given a token as input_token:
1. If input_token is not a sequence of characters, or contains 1. If input_token is not a sequence of characters, or contains
characters not allowed in Section 3.9}, fail serialisation. characters not allowed in Section 3.7}, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append input_token to output, using ASCII encoding [RFC0020]. 3. Append input_token to output.
4. Return output. 4. Return output.
4.1.10. Serialising a Byte Sequence 4.1.8. Serializing a Byte Sequence
Given a byte sequence as input_bytes: Given a byte sequence as input_bytes:
1. If input_bytes is not a sequence of bytes, fail serialisation. 1. If input_bytes is not a sequence of bytes, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append "*" to output. 3. Append "*" to output.
4. Append the result of base64-encoding input_bytes as per 4. Append the result of base64-encoding input_bytes as per
skipping to change at page 18, line 5 skipping to change at page 17, line 5
6. Return output. 6. Return output.
The encoded data is required to be padded with "=", as per [RFC4648], The encoded data is required to be padded with "=", as per [RFC4648],
Section 3.2. Section 3.2.
Likewise, encoded data SHOULD have pad bits set to zero, as per Likewise, encoded data SHOULD have pad bits set to zero, as per
[RFC4648], Section 3.5, unless it is not possible to do so due to [RFC4648], Section 3.5, unless it is not possible to do so due to
implementation constraints. implementation constraints.
4.1.11. Serialising a Boolean 4.1.9. Serializing a Boolean
Given a Boolean as input_boolean: Given a Boolean as input_boolean:
1. If input_boolean is not a boolean, fail serialisation. 1. If input_boolean is not a boolean, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append "?" to output. 3. Append "?" to output.
4. If input_boolean is true, append "1" to output. 4. If input_boolean is true, append "1" to output.
5. If input_boolean is false, append "0" to output. 5. If input_boolean is false, append "0" to output.
6. Return output. 6. Return output.
4.2. Parsing HTTP/1 Header Fields into Structured Headers 4.2. Parsing Header Fields into Structured Headers
When a receiving implementation parses textual HTTP header fields When a receiving implementation parses textual HTTP header fields
(e.g., in HTTP/1 or HTTP/2) that are known to be Structured Headers, that are known to be Structured Headers, it is important that care be
it is important that care be taken, as there are a number of edge taken, as there are a number of edge cases that can cause
cases that can cause interoperability or even security problems. interoperability or even security problems. This section specifies
This section specifies the algorithm for doing so. the algorithm for doing so.
Given an ASCII string input_string that represents the chosen Given an array of bytes input_bytes that represents the chosen
header's field-value, and header_type, one of "dictionary", "list", header's field-value (which is an empty string if that header is not
"list-list", "param-list", or "item", return the parsed header value. present), and header_type (one of "dictionary", "list", or "item"),
return the parsed header value.
1. Discard any leading OWS from input_string. 1. Convert input_bytes into an ASCII string input_string; if
conversion fails, fail parsing.
2. If header_type is "dictionary", let output be the result of 2. Discard any leading OWS from input_string.
Parsing a Dictionary from Text (Section 4.2.1).
3. If header_type is "list", let output be the result of Parsing a 3. If header_type is "list", let output be the result of Parsing a
List from Text (Section 4.2.3). List from Text (Section 4.2.1).
4. If header_type is "list-list", let output be the result of
Parsing a List of Lists from Text (Section 4.2.4).
5. If header_type is "param-list", let output be the result of 4. If header_type is "dictionary", let output be the result of
Parsing a Parameterised List from Text (Section 4.2.5). Parsing a Dictionary from Text (Section 4.2.2).
6. If header_type is "item", let output be the result of Parsing an 5. If header_type is "item", let output be the result of Parsing an
Item from Text (Section 4.2.7). Item from Text (Section 4.2.4).
7. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
8. If input_string is not empty, fail parsing. 7. If input_string is not empty, fail parsing.
9. Otherwise, return output. 8. Otherwise, return output.
When generating input_string, parsers MUST combine all instances of When generating input_bytes, parsers MUST combine all instances of
the target header field into one comma-separated field-value, as per the target header field into one comma-separated field-value, as per
[RFC7230], Section 3.2.2; this assures that the header is processed [RFC7230], Section 3.2.2; this assures that the header is processed
correctly. correctly.
For Lists, Lists of Lists, Parameterised Lists and Dictionaries, this For Lists and Dictionaries, this has the effect of correctly
has the effect of correctly concatenating all instances of the header concatenating all instances of the header field, as long as
field, as long as individual individual members of the top-level data individual individual members of the top-level data structure are not
structure are not split across multiple header instances. split across multiple header instances.
Strings split across multiple header instances will have Strings split across multiple header instances will have
unpredictable results, because comma(s) and whitespace inserted upon unpredictable results, because comma(s) and whitespace inserted upon
combination will become part of the string output by the parser. combination will become part of the string output by the parser.
Since concatenation might be done by an upstream intermediary, the Since concatenation might be done by an upstream intermediary, the
results are not under the control of the serialiser or the parser. results are not under the control of the serializer or the parser.
Integers, Floats and Byte Sequences cannot be split across multiple Tokens, Integers, Floats and Byte Sequences cannot be split across
headers because the inserted commas will cause parsing to fail. multiple headers because the inserted commas will cause parsing to
fail.
If parsing fails - including when calling another algorithm - the If parsing fails - including when calling another algorithm - the
entire header field's value MUST be discarded. This is intentionally entire header field's value MUST be discarded. This is intentionally
strict, to improve interoperability and safety, and specifications strict, to improve interoperability and safety, and specifications
referencing this document cannot loosen this requirement. referencing this document are not allowed to loosen this requirement.
Note that this has the effect of discarding any header field with
non-ASCII characters in input_string.
4.2.1. Parsing a Dictionary from Text 4.2.1. Parsing a List from Text
Given an ASCII string input_string, return an ordered map of (key, Given an ASCII string input_string, return an array of (member,
item). input_string is modified to remove the parsed value. parameters). input_string is modified to remove the parsed value.
1. Let dictionary be an empty, ordered map. 1. Let members be an empty array.
2. While input_string is not empty: 2. While input_string is not empty:
1. Let this_key be the result of running Parse a Key from Text 1. Let member be the result of running Parsing a Parameterized
(Section 4.2.2) with input_string. Member from Text (Section 4.2.1.1) with input_string.
2. If dictionary already contains this_key, fail parsing.
3. Consume the first character of input_string; if it is not
"=", fail parsing.
4. Let this_value be the result of running Parse Item from Text
(Section 4.2.7) with input_string.
5. Add key this_key with value this_value to dictionary.
6. Discard any leading OWS from input_string.
7. If input_string is empty, return dictionary.
8. Consume the first character of input_string; if it is not
COMMA, fail parsing.
9. Discard any leading OWS from input_string.
10. If input_string is empty, fail parsing. 2. Append member to members.
3. No structured data has been found; fail parsing. 3. Discard any leading OWS from input_string.
4.2.2. Parsing a Key from Text 4. If input_string is empty, return members.
Given an ASCII string input_string, return a key. input_string is 5. Consume the first character of input_string; if it is not
modified to remove the parsed value. COMMA, fail parsing.
1. If the first character of input_string is not lcalpha, fail 6. Discard any leading OWS from input_string.
parsing.
2. Let output_string be an empty string. 7. If input_string is empty, there is a trailing comma; fail
parsing.
3. While input_string is not empty: 3. No structured data has been found; return members (which is
empty).
1. Let char be the result of removing the first character of 4.2.1.1. Parsing a Parameterized Member from Text
input_string.
2. If char is not one of lcalpha, DIGIT, "_", or "-": Given an ASCII string input_string, return an token with an ordered
map of parameters. input_string is modified to remove the parsed
value.
1. Prepend char to input_string. 1. If the first character of input_string is "(", let member be the
result of running Parsing an Inner List (Section 4.2.1.2) with
input_string.
2. Return output_string. 2. Else, let member be the result of running Parsing an Item
(Section 4.2.4) with input_string.
3. Append char to output_string. 3. Let parameters be an empty, ordered map.
4. Return output_string. 4. In a loop:
4.2.3. Parsing a List from Text 1. Discard any leading OWS from input_string.
Given an ASCII string input_string, return a list of items. 2. If the first character of input_string is not ";", exit the
input_string is modified to remove the parsed value. loop.
1. Let items be an empty array. 3. Consume a ";" character from the beginning of input_string.
2. While input_string is not empty: 4. Discard any leading OWS from input_string.
1. Let item be the result of running Parse Item from Text 5. let param_name be the result of Parsing a key from Text
(Section 4.2.7) with input_string. (Section 4.2.3) from input_string.
2. Append item to items. 6. If param_name is already present in parameters, there is a
duplicate; fail parsing.
3. Discard any leading OWS from input_string. 7. Let param_value be a null value.
4. If input_string is empty, return items. 8. If the first character of input_string is "=":
5. Consume the first character of input_string; if it is not 1. Consume the "=" character at the beginning of
COMMA, fail parsing. input_string.
6. Discard any leading OWS from input_string. 2. Let param_value be the result of Parsing an Item from
Text (Section 4.2.4) from input_string.
7. If input_string is empty, fail parsing. 9. Append key param_name with value param_value to parameters.
3. No structured data has been found; fail parsing. 5. Return the tuple (member, parameters).
4.2.4. Parsing a List of Lists from Text 4.2.1.2. Parsing an Inner List
Given an ASCII string input_string, return a list of lists of items. Given an ASCII string input_string, return an array of items.
input_string is modified to remove the parsed value. input_string is modified to remove the parsed value.
1. let top_list be an empty array. 1. Consume the first character of input_string; if it is not "(",
fail parsing.
2. Let inner_list be an empty array. 2. Let inner_list be an empty array.
3. While input_string is not empty: 3. While input_string is not empty:
1. Let item be the result of running Parse Item from Text 1. Discard any leading OWS from input_string.
(Section 4.2.7) with input_string.
2. Append item to inner_list.
3. Discard any leading OWS from input_string.
4. If input_string is empty, append inner_list to top_list and
return top_list.
5. Let char be the result of consuming the first character of
input_string.
6. If char is COMMA: 2. If the first character of input_string is ")":
1. Append inner_list to top_list. 1. Consume the first character of input_string.
2. Let inner_list be an empty array. 2. Return inner_list.
7. Else if char is not ";", fail parsing. 3. Let item be the result of running Parsing an Item from Text
(Section 4.2.4) with input_string.
8. Discard any leading OWS from input_string. 4. Append item to inner_list.
9. If input_string is empty, fail parsing. 5. If the first character of input_string is not SP or ")", fail
parsing.
4. No structured data has been found; fail parsing. 4. The end of the inner list was not found; fail parsing.
4.2.5. Parsing a Parameterised List from Text 4.2.2. Parsing a Dictionary from Text
Given an ASCII string input_string, return a list of parameterised Given an ASCII string input_string, return an ordered map of (key,
identifiers. input_string is modified to remove the parsed value. item). input_string is modified to remove the parsed value.
1. Let items be an empty array. 1. Let dictionary be an empty, ordered map.
2. While input_string is not empty: 2. While input_string is not empty:
1. Let item be the result of running Parse Parameterised 1. Let this_key be the result of running Parsing a Key from
Identifier from Text (Section 4.2.6) with input_string. Text (Section 4.2.3) with input_string.
2. Append item to items.
3. Discard any leading OWS from input_string.
4. If input_string is empty, return items. 2. If dictionary already contains the name this_key, there is a
duplicate; fail parsing.
5. Consume the first character of input_string; if it is not 3. Consume the first character of input_string; if it is not
COMMA, fail parsing. "=", fail parsing.
6. Discard any leading OWS from input_string. 4. If the first character of input_string is "(", let
this_value be the result of running Parsing an Inner List
(Section 4.2.1.2) with input_string.
7. If input_string is empty, fail parsing. 5. Else, let this_value be the result of running Parsing an
Item (Section 4.2.4) with input_string.
3. No structured data has been found; fail parsing. 6. Add name this_key with value this_value to dictionary.
4.2.6. Parsing a Parameterised Identifier from Text 7. Discard any leading OWS from input_string.
Given an ASCII string input_string, return an token with an unordered 8. If input_string is empty, return dictionary.
map of parameters. input_string is modified to remove the parsed
value.
1. Let primary_identifier be the result of Parsing a Token from Text 9. Consume the first character of input_string; if it is not
(Section 4.2.10) from input_string. COMMA, fail parsing.
2. Let parameters be an empty, ordered map. 10. Discard any leading OWS from input_string.
3. In a loop: 11. If input_string is empty, there is a trailing comma; fail
parsing.
1. Discard any leading OWS from input_string. 3. No structured data has been found; return dictionary (which is
empty).
2. If the first character of input_string is not ";", exit the 4.2.3. Parsing a Key from Text
loop.
3. Consume a ";" character from the beginning of input_string. Given an ASCII string input_string, return a key. input_string is
modified to remove the parsed value.
4. Discard any leading OWS from input_string. 1. If the first character of input_string is not lcalpha, fail
parsing.
5. let param_name be the result of Parsing a key from Text 2. Let output_string be an empty string.
(Section 4.2.2) from input_string.
6. If param_name is already present in parameters, fail parsing. 3. While input_string is not empty:
7. Let param_value be a null value. 1. Let char be the result of removing the first character of
input_string.
8. If the first character of input_string is "=": 2. If char is not one of lcalpha, DIGIT, "_", or "-":
1. Consume the "=" character at the beginning of 1. Prepend char to input_string.
input_string.
2. Let param_value be the result of Parsing an Item from 2. Return output_string.
Text (Section 4.2.7) from input_string.
9. Add key param_name with value param_value to parameters. 3. Append char to output_string.
4. Return the tuple (primary_identifier, parameters). 4. Return output_string.
4.2.7. Parsing an Item from Text 4.2.4. Parsing an Item from Text
Given an ASCII string input_string, return an item. input_string is Given an ASCII string input_string, return an item. input_string is
modified to remove the parsed value. modified to remove the parsed value.
1. If the first character of input_string is a "-" or a DIGIT, 1. If the first character of input_string is a "-" or a DIGIT,
process input_string as a number (Section 4.2.8) and return the process input_string as a number (Section 4.2.5) and return the
result. result.
2. If the first character of input_string is a DQUOTE, process 2. If the first character of input_string is a DQUOTE, process
input_string as a string (Section 4.2.9) and return the result. input_string as a string (Section 4.2.6) and return the result.
3. If the first character of input_string is "*", process 3. If the first character of input_string is "*", process
input_string as a byte sequence (Section 4.2.11) and return the input_string as a byte sequence (Section 4.2.8) and return the
result. result.
4. If the first character of input_string is "?", process 4. If the first character of input_string is "?", process
input_string as a Boolean (Section 4.2.12) and return the result. input_string as a Boolean (Section 4.2.9) and return the result.
5. If the first character of input_string is an ALPHA, process 5. If the first character of input_string is an ALPHA, process
input_string as a token (Section 4.2.10) and return the result. input_string as a token (Section 4.2.7) and return the result.
6. Otherwise, fail parsing. 6. Otherwise, the item type is unrecognized; fail parsing.
4.2.8. Parsing a Number from Text 4.2.5. Parsing a Number from Text
Given an ASCII string input_string, return a number. input_string is Given an ASCII string input_string, return a number. input_string is
modified to remove the parsed value. modified to remove the parsed value.
NOTE: This algorithm parses both Integers Section 3.6 and Floats NOTE: This algorithm parses both Integers Section 3.4 and Floats
Section 3.7, and returns the corresponding structure. Section 3.5, and returns the corresponding structure.
1. Let type be "integer". 1. Let type be "integer".
2. Let sign be 1. 2. Let sign be 1.
3. Let input_number be an empty string. 3. Let input_number be an empty string.
4. If the first character of input_string is "-", remove it from 4. If the first character of input_string is "-", consume it and
input_string and set sign to -1. set sign to -1.
5. If input_string is empty, fail parsing. 5. If input_string is empty, there is an empty integer; fail
parsing.
6. If the first character of input_string is not a DIGIT, fail 6. If the first character of input_string is not a DIGIT, fail
parsing. parsing.
7. While input_string is not empty: 7. While input_string is not empty:
1. Let char be the result of removing the first character of 1. Let char be the result of consuming the first character of
input_string. input_string.
2. If char is a DIGIT, append it to input_number. 2. If char is a DIGIT, append it to input_number.
3. Else, if type is "integer" and char is ".", append char to 3. Else, if type is "integer" and char is ".", append char to
input_number and set type to "float". input_number and set type to "float".
4. Otherwise, prepend char to input_string, and exit the loop. 4. Otherwise, prepend char to input_string, and exit the loop.
5. If type is "integer" and input_number contains more than 15 5. If type is "integer" and input_number contains more than 15
skipping to change at page 25, line 9 skipping to change at page 23, line 32
6. If type is "float" and input_number contains more than 16 6. If type is "float" and input_number contains more than 16
characters, fail parsing. characters, fail parsing.
8. If type is "integer": 8. If type is "integer":
1. Parse input_number as an integer and let output_number be 1. Parse input_number as an integer and let output_number be
the product of the result and sign. the product of the result and sign.
2. If output_number is outside the range defined in 2. If output_number is outside the range defined in
Section 3.6, fail parsing. Section 3.4, fail parsing.
9. Otherwise: 9. Otherwise:
1. If the final character of input_number is ".", fail parsing. 1. If the final character of input_number is ".", fail parsing.
2. Parse input_number as a float and let output_number be the 2. Parse input_number as a float and let output_number be the
product of the result and sign. product of the result and sign.
10. Return output_number. 10. Return output_number.
4.2.9. Parsing a String from Text 4.2.6. Parsing a String from Text
Given an ASCII string input_string, return an unquoted string. Given an ASCII string input_string, return an unquoted string.
input_string is modified to remove the parsed value. input_string is modified to remove the parsed value.
1. Let output_string be an empty string. 1. Let output_string be an empty string.
2. If the first character of input_string is not DQUOTE, fail 2. If the first character of input_string is not DQUOTE, fail
parsing. parsing.
3. Discard the first character of input_string. 3. Discard the first character of input_string.
4. While input_string is not empty: 4. While input_string is not empty:
1. Let char be the result of removing the first character of 1. Let char be the result of consuming the first character of
input_string. input_string.
2. If char is a backslash ("\"): 2. If char is a backslash ("\"):
1. If input_string is now empty, fail parsing. 1. If input_string is now empty, fail parsing.
2. Else: 2. Else:
1. Let next_char be the result of removing the first 1. Let next_char be the result of consuming the first
character of input_string. character of input_string.
2. If next_char is not DQUOTE or "\", fail parsing. 2. If next_char is not DQUOTE or "\", fail parsing.
3. Append next_char to output_string. 3. Append next_char to output_string.
3. Else, if char is DQUOTE, return output_string. 3. Else, if char is DQUOTE, return output_string.
4. Else, if char is in the range %x00-1f or %x7f (i.e., is not 4. Else, if char is in the range %x00-1f or %x7f (i.e., is not
in VCHAR or SP), fail parsing. in VCHAR or SP), fail parsing.
5. Else, append char to output_string. 5. Else, append char to output_string.
5. Reached the end of input_string without finding a closing DQUOTE; 5. Reached the end of input_string without finding a closing DQUOTE;
fail parsing. fail parsing.
4.2.10. Parsing a Token from Text 4.2.7. Parsing a Token from Text
Given an ASCII string input_string, return a token. input_string is Given an ASCII string input_string, return a token. input_string is
modified to remove the parsed value. modified to remove the parsed value.
1. If the first character of input_string is not ALPHA, fail 1. If the first character of input_string is not ALPHA, fail
parsing. parsing.
2. Let output_string be an empty string. 2. Let output_string be an empty string.
3. While input_string is not empty: 3. While input_string is not empty:
1. Let char be the result of removing the first character of 1. Let char be the result of consuming the first character of
input_string. input_string.
2. If char is not one of ALPHA, DIGIT, "_", "-", ".", ":", "%", 2. If char is not one of ALPHA, DIGIT, "_", "-", ".", ":", "%",
"*" or "/": "*" or "/":
1. Prepend char to input_string. 1. Prepend char to input_string.
2. Return output_string. 2. Return output_string.
3. Append char to output_string. 3. Append char to output_string.
4. Return output_string. 4. Return output_string.
4.2.11. Parsing a Byte Sequence from Text 4.2.8. Parsing a Byte Sequence from Text
Given an ASCII string input_string, return a byte sequence. Given an ASCII string input_string, return a byte sequence.
input_string is modified to remove the parsed value. input_string is modified to remove the parsed value.
1. If the first character of input_string is not "*", fail parsing. 1. If the first character of input_string is not "*", fail parsing.
2. Discard the first character of input_string. 2. Discard the first character of input_string.
3. If there is not a "*" character before the end of input_string, 3. If there is not a "*" character before the end of input_string,
fail parsing. fail parsing.
4. Let b64_content be the result of removing content of input_string 4. Let b64_content be the result of consuming content of
up to but not including the first instance of the character "*". input_string up to but not including the first instance of the
character "*".
5. Consume the "*" character at the beginning of input_string. 5. Consume the "*" character at the beginning of input_string.
6. If b64_content contains a character not included in ALPHA, DIGIT, 6. If b64_content contains a character not included in ALPHA, DIGIT,
"+", "/" and "=", fail parsing. "+", "/" and "=", fail parsing.
7. Let binary_content be the result of Base 64 Decoding [RFC4648] 7. Let binary_content be the result of Base 64 Decoding [RFC4648]
b64_content, synthesising padding if necessary (note the b64_content, synthesizing padding if necessary (note the
requirements about recipient behaviour below). requirements about recipient behaviour below).
8. Return binary_content. 8. Return binary_content.
Because some implementations of base64 do not allow reject of encoded Because some implementations of base64 do not allow reject of encoded
data that is not properly "=" padded (see [RFC4648], Section 3.2), data that is not properly "=" padded (see [RFC4648], Section 3.2),
parsers SHOULD NOT fail when it is not present, unless they cannot be parsers SHOULD NOT fail when it is not present, unless they cannot be
configured to do so. configured to do so.
Because some implementations of base64 do not allow rejection of Because some implementations of base64 do not allow rejection of
encoded data that has non-zero pad bits (see [RFC4648], Section 3.5), encoded data that has non-zero pad bits (see [RFC4648], Section 3.5),
parsers SHOULD NOT fail when it is present, unless they cannot be parsers SHOULD NOT fail when it is present, unless they cannot be
configured to do so. configured to do so.
This specification does not relax the requirements in [RFC4648], This specification does not relax the requirements in [RFC4648],
Section 3.1 and 3.3; therefore, parsers MUST fail on characters Section 3.1 and 3.3; therefore, parsers MUST fail on characters
outside the base64 alphabet, and on line feeds in encoded data. outside the base64 alphabet, and on line feeds in encoded data.
4.2.12. Parsing a Boolean from Text 4.2.9. Parsing a Boolean from Text
Given an ASCII string input_string, return a Boolean. input_string is Given an ASCII string input_string, return a Boolean. input_string is
modified to remove the parsed value. modified to remove the parsed value.
1. If the first character of input_string is not "?", fail parsing. 1. If the first character of input_string is not "?", fail parsing.
2. Discard the first character of input_string. 2. Discard the first character of input_string.
3. If the first character of input_string matches "1", discard the 3. If the first character of input_string matches "1", discard the
first character, and return true. first character, and return true.
skipping to change at page 28, line 10 skipping to change at page 26, line 31
5. IANA Considerations 5. IANA Considerations
This draft has no actions for IANA. This draft has no actions for IANA.
6. Security Considerations 6. Security Considerations
The size of most types defined by Structured Headers is not limited; The size of most types defined by Structured Headers is not limited;
as a result, extremely large header fields could be an attack vector as a result, extremely large header fields could be an attack vector
(e.g., for resource consumption). Most HTTP implementations limit (e.g., for resource consumption). Most HTTP implementations limit
the sizes of size of individual header fields as well as the overall the sizes of individual header fields as well as the overall header
header block size to mitigate such attacks. block size to mitigate such attacks.
It is possible for parties with the ability to inject new HTTP header It is possible for parties with the ability to inject new HTTP header
fields to change the meaning of a Structured Header. In some fields to change the meaning of a Structured Header. In some
circumstances, this will cause parsing to fail, but it is not circumstances, this will cause parsing to fail, but it is not
possible to reliably fail in all such circumstances. possible to reliably fail in all such circumstances.
7. References 7. References
7.1. Normative References 7.1. Normative References
skipping to change at page 30, line 39 skipping to change at page 29, line 10
depths. Since the resulting memory commitment might be unsuitable depths. Since the resulting memory commitment might be unsuitable
(e.g., in embedded and other limited server deployments), it's (e.g., in embedded and other limited server deployments), it's
necessary to limit it in some fashion; however, existing JSON necessary to limit it in some fashion; however, existing JSON
implementations have no such limits, and even if a limit is implementations have no such limits, and even if a limit is
specified, it's likely that some header field definition will find a specified, it's likely that some header field definition will find a
need to violate it. need to violate it.
Because of JSON's broad adoption and implementation, it is difficult Because of JSON's broad adoption and implementation, it is difficult
to impose such additional constraints across all implementations; to impose such additional constraints across all implementations;
some deployments would fail to enforce them, thereby harming some deployments would fail to enforce them, thereby harming
interoperability. interoperability. In short, if it looks like JSON, people will be
tempted to use a JSON parser / serialiser on header fields.
Since a major goal for Structured Headers is to improve Since a major goal for Structured Headers is to improve
interoperability and simplify implementation, these concerns led to a interoperability and simplify implementation, these concerns led to a
format that requires a dedicated parser and serialiser. format that requires a dedicated parser and serializer.
Additionally, there were widely shared feelings that JSON doesn't Additionally, there were widely shared feelings that JSON doesn't
"look right" in HTTP headers. "look right" in HTTP headers.
B.2. Structured Headers don't "fit" my data. B.2. Structured Headers don't "fit" my data.
Structured headers intentionally limits the complexity of data Structured headers intentionally limits the complexity of data
structures, to assure that it can be processed in a performant manner structures, to assure that it can be processed in a performant manner
with little overhead. This means that work is necessary to fit some with little overhead. This means that work is necessary to fit some
data types into them. data types into them.
Sometimes, this can be achieved by creating limited substructures in Sometimes, this can be achieved by creating limited substructures in
values, and/or using more than one header. For example, consider: values, and/or using more than one header. For example, consider:
Example-Thing: name="Widget", cost=89.2, descriptions="foo bar" Example-Thing: name="Widget", cost=89.2, descriptions=(foo bar)
Example-Description: foo; url="https://example.net"; context=123, Example-Description: foo; url="https://example.net"; context=123,
bar; url="https://example.org"; context=456 bar; url="https://example.org"; context=456
Since the description contains a list of key/value pairs, we use a Since the description contains an array of key/value pairs, we use a
Parameterised List to represent them, with the token for each item in List to represent them, with the token for each item in the array
the list used to identify it in the "descriptions" member of the used to identify it in the "descriptions" member of the Example-Thing
Example-Thing header. header.
When specifying more than one header, it's important to remember to When specifying more than one header, it's important to remember to
describe what a processor's behaviour should be when one of the describe what a processor's behaviour should be when one of the
headers is missing. headers is missing.
If you need to fit arbitrarily complex data into a header, Structured If you need to fit arbitrarily complex data into a header, Structured
Headers is probably a poor fit for your use case. Headers is probably a poor fit for your use case.
B.3. What should generic Structured Headers implementations expose? Appendix C. Implementation Notes
A generic implementation should expose the top-level parse A generic implementation of this specification should expose the top-
(Section 4.2) and serialise (Section 4.1) functions. They need not level parse (Section 4.2) and serialize (Section 4.1) functions.
be functions; for example, it could be implemented as an object, with They need not be functions; for example, it could be implemented as
methods for each of the different top-level types. an object, with methods for each of the different top-level types.
For interoperability, it's important that generic implementations be For interoperability, it's important that generic implementations be
complete and follow the algorithms closely; see Section 1.1. To aid complete and follow the algorithms closely; see Section 1.1. To aid
this, a common test suite is being maintained by the community; see this, a common test suite is being maintained by the community; see
https://github.com/httpwg/structured-header-tests [7]. https://github.com/httpwg/structured-header-tests [7].
Implementers should note that dictionaries and parameters are order- Implementers should note that dictionaries and parameters are order-
preserving maps. Some headers may not convey meaning in the ordering preserving maps. Some headers may not convey meaning in the ordering
of these data types, but it should still be exposed so that of these data types, but it should still be exposed so that
applications which need to use it will have it available. applications which need to use it will have it available.
Appendix C. Changes Likewise, implementations should note that it's important to preserve
the distinction between tokens and strings. While most programming
languages have native types that map to the other types well, it may
be necessary to create a wrapper "token" object or use a parameter on
functions to assure that these types remain separate.
Appendix D. Changes
_RFC Editor: Please remove this section before publication._ _RFC Editor: Please remove this section before publication._
C.1. Since draft-ietf-httpbis-header-structure-09 D.1. Since draft-ietf-httpbis-header-structure-10
o Update abstract (#799).
o Input and output are now arrays of bytes (#662).
o Implementations need to preserve difference between token and
string (#790).
o Allow empty dictionaries and lists (#781).
o Change parameterized lists to have primary items (#797).
o Allow inner lists in both dictionaries and lists; removes lists of
lists (#816).
o Subsume Parameterised Lists into Lists (#839).
D.2. Since draft-ietf-httpbis-header-structure-09
o Changed Boolean from T/F to 1/0 (#784). o Changed Boolean from T/F to 1/0 (#784).
o Parameters are now ordered maps (#765). o Parameters are now ordered maps (#765).
o Clamp integers to 15 digits (#737). o Clamp integers to 15 digits (#737).
C.2. Since draft-ietf-httpbis-header-structure-08 D.3. Since draft-ietf-httpbis-header-structure-08
o Disallow whitespace before items properly (#703). o Disallow whitespace before items properly (#703).
o Created "key" for use in dictionaries and parameters, rather than o Created "key" for use in dictionaries and parameters, rather than
relying on identifier (#702). Identifiers have a separate minimum relying on identifier (#702). Identifiers have a separate minimum
supported size. supported size.
o Expanded the range of special characters allowed in identifier to o Expanded the range of special characters allowed in identifier to
include all of ALPHA, ".", ":", and "%" (#702). include all of ALPHA, ".", ":", and "%" (#702).
skipping to change at page 32, line 31 skipping to change at page 31, line 29
o Gave better names for referring specs to use in Parameterised o Gave better names for referring specs to use in Parameterised
Lists (#720). Lists (#720).
o Added Lists of Lists (#721). o Added Lists of Lists (#721).
o Rename Identifier to Token (#725). o Rename Identifier to Token (#725).
o Add implementation guidance (#727). o Add implementation guidance (#727).
C.3. Since draft-ietf-httpbis-header-structure-07 D.4. Since draft-ietf-httpbis-header-structure-07
o Make Dictionaries ordered mappings (#659). o Make Dictionaries ordered mappings (#659).
o Changed "binary content" to "byte sequence" to align with Infra o Changed "binary content" to "byte sequence" to align with Infra
specification (#671). specification (#671).
o Changed "mapping" to "map" for #671. o Changed "mapping" to "map" for #671.
o Don't fail if byte sequences aren't "=" padded (#658). o Don't fail if byte sequences aren't "=" padded (#658).
o Add Booleans (#683). o Add Booleans (#683).
o Allow identifiers in items again (#629). o Allow identifiers in items again (#629).
o Disallowed whitespace before items (#703). o Disallowed whitespace before items (#703).
o Explain the consequences of splitting a string across multiple o Explain the consequences of splitting a string across multiple
headers (#686). headers (#686).
C.4. Since draft-ietf-httpbis-header-structure-06 D.5. Since draft-ietf-httpbis-header-structure-06
o Add a FAQ. o Add a FAQ.
o Allow non-zero pad bits. o Allow non-zero pad bits.
o Explicitly check for integers that violate constraints. o Explicitly check for integers that violate constraints.
C.5. Since draft-ietf-httpbis-header-structure-05 D.6. Since draft-ietf-httpbis-header-structure-05
o Reorganise specification to separate parsing out. o Reorganise specification to separate parsing out.
o Allow referencing specs to use ABNF. o Allow referencing specs to use ABNF.
o Define serialisation algorithms. o Define serialisation algorithms.
o Refine relationship between ABNF, parsing and serialisation o Refine relationship between ABNF, parsing and serialisation
algorithms. algorithms.
C.6. Since draft-ietf-httpbis-header-structure-04 D.7. Since draft-ietf-httpbis-header-structure-04
o Remove identifiers from item. o Remove identifiers from item.
o Remove most limits on sizes. o Remove most limits on sizes.
o Refine number parsing. o Refine number parsing.
C.7. Since draft-ietf-httpbis-header-structure-03 D.8. Since draft-ietf-httpbis-header-structure-03
o Strengthen language around failure handling. o Strengthen language around failure handling.
C.8. Since draft-ietf-httpbis-header-structure-02 D.9. Since draft-ietf-httpbis-header-structure-02
o Split Numbers into Integers and Floats. o Split Numbers into Integers and Floats.
o Define number parsing. o Define number parsing.
o Tighten up binary parsing and give it an explicit end delimiter. o Tighten up binary parsing and give it an explicit end delimiter.
o Clarify that mappings are unordered. o Clarify that mappings are unordered.
o Allow zero-length strings. o Allow zero-length strings.
o Improve string parsing algorithm. o Improve string parsing algorithm.
o Improve limits in algorithms. o Improve limits in algorithms.
o Require parsers to combine header fields before processing. o Require parsers to combine header fields before processing.
o Throw an error on trailing garbage. o Throw an error on trailing garbage.
C.9. Since draft-ietf-httpbis-header-structure-01 D.10. Since draft-ietf-httpbis-header-structure-01
o Replaced with draft-nottingham-structured-headers. o Replaced with draft-nottingham-structured-headers.
C.10. Since draft-ietf-httpbis-header-structure-00 D.11. Since draft-ietf-httpbis-header-structure-00
o Added signed 64bit integer type. o Added signed 64bit integer type.
o Drop UTF8, and settle on BCP137 ::EmbeddedUnicodeChar for h1- o Drop UTF8, and settle on BCP137 ::EmbeddedUnicodeChar for h1-
unicode-string. unicode-string.
o Change h1_blob delimiter to ":" since "'" is valid t_char o Change h1_blob delimiter to ":" since "'" is valid t_char
Authors' Addresses Authors' Addresses
 End of changes. 257 change blocks. 
527 lines changed or deleted 480 lines changed or added

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