draft-ietf-httpbis-header-structure-07.txt   draft-ietf-httpbis-header-structure-latest.txt 
HTTP Working Group M. Nottingham HTTP Working Group M. Nottingham
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track P-H. Kamp Intended status: Standards Track P-H. Kamp
Expires: January 3, 2019 The Varnish Cache Project Expires: April 14, 2019 The Varnish Cache Project
July 2, 2018 October 11, 2018
Structured Headers for HTTP Structured Headers for HTTP
draft-ietf-httpbis-header-structure-07 draft-ietf-httpbis-header-structure-latest
Abstract Abstract
This document describes a set of data types and algorithms associated This document describes a set of data types and algorithms associated
with them that are intended to make it easier and safer to define and with them that are intended to make it easier and safer to define and
handle HTTP header fields. It is intended for use by new handle HTTP header fields. It is intended for use by new
specifications of HTTP header fields as well as revisions of existing specifications of HTTP header fields as well as revisions of existing
header field specifications when doing so does not cause header field specifications when doing so does not cause
interoperability issues. interoperability issues.
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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 January 3, 2019. This Internet-Draft will expire on April 14, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Defining New Structured Headers . . . . . . . . . . . . . . . 4 2. Defining New Structured Headers . . . . . . . . . . . . . . . 4
3. Structured Header Data Types . . . . . . . . . . . . . . . . 6 3. Structured Header Data Types . . . . . . . . . . . . . . . . 7
3.1. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Parameterised Lists . . . . . . . . . . . . . . . . . . . 7 3.3. Parameterised Lists . . . . . . . . . . . . . . . . . . . 8
3.4. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.4. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5. Integers . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5. Integers . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.6. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.7. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.7. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.8. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 9 3.8. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 10
3.9. Binary Content . . . . . . . . . . . . . . . . . . . . . 9 3.9. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 10
4. Structured Headers in HTTP/1 . . . . . . . . . . . . . . . . 10 3.10. Booleans . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Serialising Structured Headers into HTTP/1 . . . . . . . 10 4. Structured Headers in HTTP/1 . . . . . . . . . . . . . . . . 11
4.2. Parsing HTTP/1 Header Fields into Structured Headers . . 14 4.1. Serialising Structured Headers into HTTP/1 . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 4.2. Parsing HTTP/1 Header Fields into Structured Headers . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 22 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 6. Security Considerations . . . . . . . . . . . . . . . . . . . 24
7.1. Normative References . . . . . . . . . . . . . . . . . . 22 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.2. Informative References . . . . . . . . . . . . . . . . . 23 7.1. Normative References . . . . . . . . . . . . . . . . . . 25
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Frequently Asked Questions . . . . . . . . . . . . . 24 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 24 Appendix A. Frequently Asked Questions . . . . . . . . . . . . . 26
A.2. Structured Headers don't "fit" my data. . . . . . . . . . 25 A.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 26
Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . 25 A.2. Structured Headers don't "fit" my data. . . . . . . . . . 27
B.1. Since draft-ietf-httpbis-header-structure-06 . . . . . . 25 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . 28
B.2. Since draft-ietf-httpbis-header-structure-05 . . . . . . 25 B.1. Since draft-ietf-httpbis-header-structure-07 . . . . . . 28
B.3. Since draft-ietf-httpbis-header-structure-04 . . . . . . 26 B.2. Since draft-ietf-httpbis-header-structure-06 . . . . . . 28
B.4. Since draft-ietf-httpbis-header-structure-03 . . . . . . 26 B.3. Since draft-ietf-httpbis-header-structure-05 . . . . . . 28
B.5. Since draft-ietf-httpbis-header-structure-02 . . . . . . 26 B.4. Since draft-ietf-httpbis-header-structure-04 . . . . . . 28
B.6. Since draft-ietf-httpbis-header-structure-01 . . . . . . 26 B.5. Since draft-ietf-httpbis-header-structure-03 . . . . . . 29
B.7. Since draft-ietf-httpbis-header-structure-00 . . . . . . 26 B.6. Since draft-ietf-httpbis-header-structure-02 . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 B.7. Since draft-ietf-httpbis-header-structure-01 . . . . . . 29
B.8. Since draft-ietf-httpbis-header-structure-00 . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
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 serialisers often
need to be written, because each header has slightly different need to be written, because each header has slightly different
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1.1. Notational Conventions 1.1. 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 This document uses the Augmented Backus-Naur Form (ABNF) notation of
[RFC5234], including the VCHAR, DIGIT, ALPHA and DQUOTE rules from [RFC5234], including the VCHAR, SP, DIGIT, ALPHA and DQUOTE rules
that document. It also includes the OWS rule from [RFC7230]. 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. behaviours, and ABNF to illustrate expected syntax in HTTP/1-style
header fields.
For parsing, implementations MUST follow the algorithms, but MAY vary For parsing from HTTP/1 header fields, implementations MUST follow
in implementation so as the behaviours are indistinguishable from the algorithms, but MAY vary in implementation so as the behaviours
specified behaviour. If there is disagreement between the parsing are indistinguishable from specified behaviour. If there is
algorithms and ABNF, the specified algorithms take precedence. disagreement between the parsing algorithms and ABNF, the specified
algorithms take precedence. In some places, the algorithms are
"greedy" with whitespace, but this should not affect conformance.
For serialisation, the ABNF illustrates the range of acceptable wire For serialisation to HTTP/1 header fields, the ABNF illustrates the
representations with as much fidelity as possible, and the algorithms range of acceptable wire representations with as much fidelity as
define the recommended way to produce them. Implementations MAY vary possible, and the algorithms define the recommended way to produce
from the specified behaviour so long as the output still matches the them. Implementations MAY vary from the specified behaviour so long
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:
o Reference this specification. Recipients and generators of the o Reference this specification. Recipients and generators of the
header need to know that the requirements of this document are in header need to know that the requirements of this document are in
effect. effect.
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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; they can only add additional a structure or its processing because doing so would preclude
constraints, because doing so would preclude handling by generic handling by generic software; they can only add additional
software. constraints.
For example: For example:
# Foo-Example Header # 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:
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and/or the size of the entire header block. 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/1.
3.1. Dictionaries 3.1. Dictionaries
Dictionaries are unordered maps of key-value pairs, where the keys Dictionaries are ordered maps of key-value pairs, where the keys are
are identifiers (Section 3.8) and the values are items (Section 3.4). identifiers (Section 3.8) and the values are items (Section 3.4).
There can be one or more members, and keys are required to be unique. There can be one or more members, and keys are required to be unique.
The ABNF for dictionaries is: 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 ) sh-dictionary = dict-member *( OWS "," OWS dict-member )
dict-member = member-name "=" member-value dict-member = member-name "=" member-value
member-name = identifier member-name = sh-identifier
member-value = sh-item member-value = sh-item
In HTTP/1, keys and values are separated by "=" (without whitespace), In HTTP/1, keys and values are separated by "=" (without whitespace),
and key/value pairs are separated by a comma with optional and key/value pairs are separated by a comma with optional
whitespace. For example: whitespace. For example:
Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGUK=* Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=*
Typically, a header field specification will define the semantics of Typically, a header field specification will define the semantics of
individual keys, as well as whether their presence is required or individual keys, as well as whether their presence is required or
optional. Recipients MUST ignore keys that are undefined or unknown, optional. Recipients MUST ignore keys that are undefined or unknown,
unless the header field's specification specifically disallows them. unless the header field's specification specifically disallows them.
Parsers MUST support dictionaries containing at least 1024 key/value Parsers MUST support dictionaries containing at least 1024 key/value
pairs. pairs.
3.2. Lists 3.2. Lists
Lists are arrays of items (Section 3.4) with one or more members. Lists are arrays of items (Section 3.4) 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 ) sh-list = list-member *( OWS "," OWS list-member )
list-member = sh-item list-member = sh-item
In HTTP/1, each member is separated by a comma and optional In HTTP/1, each member is separated by a comma and optional
whitespace. For example, a header field whose value is defined as a whitespace. For example, a header field whose value is defined as a
list of strings could look like: 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 Header specifications can constrain the types of individual values if
necessary. necessary.
Parsers MUST support lists containing at least 1024 members. Parsers MUST support lists containing at least 1024 members.
3.3. Parameterised Lists 3.3. Parameterised Lists
Parameterised Lists are arrays of a parameterised identifiers. Parameterised Lists are arrays of a parameterised identifiers.
A parameterised identifier is an identifier (Section 3.8) with an A parameterised identifier is an identifier (Section 3.8) with an
optional set of parameters, each parameter having a identifier and an optional set of parameters, each parameter having an identifier and
optional value that is an item (Section 3.4). Ordering between an optional value that is an item (Section 3.4). Ordering between
parameters is not significant, and duplicate parameters MUST cause parameters is not significant, and duplicate parameters MUST cause
parsing to fail. parsing to fail.
The ABNF for parameterised lists is: The ABNF for parameterised lists in HTTP/1 headers is:
sh-param-list = param-id *( OWS "," OWS param-id ) sh-param-list = param-id *( OWS "," OWS param-id )
param-id = identifier *parameter param-id = sh-identifier *parameter
parameter = OWS ";" OWS param-name [ "=" param-value ] parameter = OWS ";" OWS param-name [ "=" param-value ]
param-name = identifier param-name = sh-identifier
param-value = sh-item param-value = sh-item
In HTTP/1, each param-id is separated by a comma and optional In HTTP/1, each param-id is separated by a comma and optional
whitespace (as in Lists), and the parameters are separated by whitespace (as in Lists), and the parameters are separated by
semicolons. For example: semicolons. For example:
Example-ParamListHeader: abc_123;a=1;b=2; cdef_456, ghi;q="9";r=w Example-ParamListHeader: abc_123;a=1;b=2; cdef_456, ghi;q="9";r="w"
Parsers MUST support parameterised lists containing at least 1024 Parsers MUST support parameterised lists containing at least 1024
members, and support members with at least 256 parameters. members, and support members with at least 256 parameters.
3.4. Items 3.4. Items
An item is can be a integer (Section 3.5), float (Section 3.6), An item is can be a integer (Section 3.5), float (Section 3.6),
string (Section 3.7), or binary content (Section 3.9). string (Section 3.7), identifier (Section 3.8), byte sequence
(Section 3.9), or Boolean (Section 3.10).
The ABNF for items is: The ABNF for items in HTTP/1 headers is:
sh-item = sh-integer / sh-float / sh-string / sh-binary sh-item = sh-integer / sh-float / sh-string / sh-identifier / sh-binary
/ sh-boolean
3.5. Integers 3.5. Integers
Integers have a range of -9,223,372,036,854,775,808 to Integers have a range of -9,223,372,036,854,775,808 to
9,223,372,036,854,775,807 inclusive (i.e., a 64-bit signed integer). 9,223,372,036,854,775,807 inclusive (i.e., a 64-bit signed integer).
The ABNF for integers is: The ABNF for integers in HTTP/1 headers is:
sh-integer = ["-"] 1*19DIGIT sh-integer = ["-"] 1*19DIGIT
For example: For example:
Example-IntegerHeader: 42 Example-IntegerHeader: 42
3.6. Floats 3.6. 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 is: The ABNF for floats in HTTP/1 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 /
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like: like:
Example-FloatHeader: 4.5 Example-FloatHeader: 4.5
3.7. Strings 3.7. 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 is: The ABNF for strings in HTTP/1 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 HTTP/1 headers, strings are delimited with double quotes, using a
backslash ("\") to escape double quotes and backslashes. For backslash ("\") to escape double quotes and backslashes. For
example: example:
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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, binary content (Section 3.9) SHOULD be specified, along with content, a byte sequence (Section 3.9) SHOULD be specified, along
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.
3.8. Identifiers 3.8. Identifiers
Identifiers are short textual identifiers; their abstract model is Identifiers are short textual identifiers; their abstract model is
identical to their expression in the textual HTTP serialisation. identical to their expression in the textual HTTP serialisation.
Parsers MUST support identifiers with at least 64 characters. Parsers MUST support identifiers with at least 64 characters.
The ABNF for identifiers is: The ABNF for identifiers in HTTP/1 headers is:
identifier = lcalpha *( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ) sh-identifier = lcalpha *( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
lcalpha = %x61-7A ; a-z lcalpha = %x61-7A ; a-z
Note that identifiers can only contain lowercase letters. Note that identifiers can only contain lowercase letters.
3.9. Binary Content 3.9. Byte Sequences
Arbitrary binary content can be conveyed in Structured Headers. Byte sequences can be conveyed in Structured Headers.
The ABNF for binary content is: The ABNF for a byte sequence in HTTP/1 headers is:
sh-binary = "*" *(base64) "*" sh-binary = "*" *(base64) "*"
base64 = ALPHA / DIGIT / "+" / "/" / "=" base64 = ALPHA / DIGIT / "+" / "/" / "="
In HTTP/1 headers, binary content is delimited with asterisks and In HTTP/1 headers, a byte sequence is delimited with asterisks and
encoded using base64 ([RFC4648], Section 4). For example: encoded using base64 ([RFC4648], Section 4). For example:
Example-BinaryHdr: *cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==* Example-BinaryHdr: *cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==*
Parsers MUST support binary content with at least 16384 octets after Parsers MUST support byte sequences with at least 16384 octets after
decoding. decoding.
3.10. Booleans
Boolean values can be conveyed in Structured Headers.
The ABNF for a Boolean in HTTP/1 headers is:
sh-boolean = "!" boolean
boolean = "T" / "F"
In HTTP/1 headers, a byte sequence is delimited with a "!" character.
For example:
Example-BoolHdr: !T
4. Structured Headers in HTTP/1 4. Structured Headers in HTTP/1
This section defines how to serialise and parse Structured Headers in This section defines how to serialise and parse Structured Headers in
HTTP/1 textual header fields, and protocols compatible with them HTTP/1 textual header fields, and protocols compatible with them
(e.g., in HTTP/2 [RFC7540] before HPACK [RFC7541] is applied). (e.g., in HTTP/2 [RFC7540] before HPACK [RFC7541] is applied).
4.1. Serialising Structured Headers into HTTP/1 4.1. Serialising Structured Headers into HTTP/1
Given a structured defined in this specification: Given a structured defined in this specification:
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2. Append name to output. 2. Append name to output.
3. Append "=" to output. 3. Append "=" to output.
4. Let value be the result of applying Serialising an Item 4. Let value be the result of applying Serialising an Item
Section 4.1.4 to mem's member-value. Section 4.1.4 to mem's member-value.
5. Append value to output. 5. Append value to output.
6. If more members remain in input:
1. Append a COMMA to output.
2. Append a single WS to output.
3. Return output. 3. Return output.
4.1.2. Serialising a List 4.1.2. Serialising a List
Given a list as input: Given a list as input:
1. Let output be an empty string. 1. Let output be an empty string.
2. For each member mem of input: 2. For each member mem of input:
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2. For each member mem of input: 2. For each member mem of input:
1. Let id be the result of applying Serialising an Identifier 1. Let id be the result of applying Serialising an Identifier
Section 4.1.8 to mem's identifier. Section 4.1.8 to mem's identifier.
2. Append id to output. 2. Append id to output.
3. For each parameter in mem's parameters: 3. For each parameter in mem's parameters:
1. Let name be the result of applying Serialising an 1. Append ";" to output.
2. Let name be the result of applying Serialising an
Identifier Section 4.1.8 to parameter's param-name. Identifier Section 4.1.8 to parameter's param-name.
2. Append name to output. 3. Append name to output.
3. If parameter has a param-value: 4. If parameter has a param-value:
1. Let value be the result of applying Serialising an 1. Let value be the result of applying Serialising an
Item Section 4.1.4 to parameter's param-value. Item Section 4.1.4 to parameter's param-value.
2. Append "=" to output. 2. Append "=" to output.
3. Append value to output. 3. Append value to output.
4. If more members remain in input:
1. Append a COMMA to output.
2. Append a single WS to output.
3. Return output. 3. Return output.
4.1.4. Serialising an Item 4.1.4. Serialising an Item
Given an item as input: Given an item as input:
1. If input is a type other than an integer, float, string or binary 1. If input is a type other than an integer, float, string,
content, fail serialisation. identifier, byte sequence, or Boolean, fail serialisation.
2. Let output be an empty string. 2. If input is an integer, return the result of applying Serialising
an Integer Section 4.1.5 to input.
3. If input is an integer, let value be the result of applying 3. If input is a float, return the result of applying Serialising a
Serialising an Integer Section 4.1.5 to input. Float Section 4.1.6 to input.
4. If input is a float, let value be the result of applying 4. If input is a string, return the result of applying Serialising a
Serialising a Float Section 4.1.6 to input. String Section 4.1.7 to input.
5. If input is a string, let value be the result of applying 5. If input is an identifier, return the result of Serialising an
Serialising a String Section 4.1.7 to input. Identifier {#ser-identifier}.
6. If input is binary content, let value be the result of applying 6. If input is a Boolean, return the result of applying Serialising
Serialising Binary Content Section 4.1.9 to input. a Boolean Section 4.1.10 to input.
7. Return output. 7. Otherwise, return the result of applying Serialising a Byte
Sequence Section 4.1.9 to input.
4.1.5. Serialising an Integer 4.1.5. Serialising an Integer
Given an integer as input: Given an integer as input:
1. If input is not an integer in the range of 1. If input is not an integer in the range of
-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
inclusive, fail serialisation. inclusive, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
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6. Append input's decimal component represented in base 10 using 6. Append input's decimal component represented in base 10 using
only decimal digits to output; if it is zero, append "0". only decimal digits to output; if it is zero, append "0".
7. Return output. 7. Return output.
4.1.7. Serialising a String 4.1.7. Serialising a String
Given a string as input: Given a string as input:
1. If input is not a sequence of characters, or contains characters 1. If input is not a sequence of characters, or contains characters
outside the range allowed by VCHAR, fail serialisation. outside the range allowed by VCHAR or SP, fail 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: 4. For each character char in input:
1. If char is "\" or DQUOTE: 1. If char is "\" or DQUOTE:
1. Append "\" to output. 1. Append "\" to output.
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1. If input is not a sequence of characters, or contains characters 1. If input is not a sequence of characters, or contains characters
not allowed in Section 3.8, fail serialisation. not allowed in Section 3.8, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append input to output, using ASCII encoding [RFC0020]. 3. Append input to output, using ASCII encoding [RFC0020].
4. Return output. 4. Return output.
4.1.9. Serialising Binary Content 4.1.9. Serialising a Byte Sequence
Given binary content as input: Given a byte sequence as input:
1. If input is not a sequence of bytes, fail serialisation. 1. If input 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 as per [RFC4648], 4. Append the result of base64-encoding input as per [RFC4648],
Section 4, taking account of the requirements below. Section 4, taking account of the requirements below.
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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.
4.1.10. Serialising a Boolean
Given a Boolean as input:
1. If input is not a boolean, fail serialisation.
2. Let output be an empty string.
3. Append "!" to output.
4. If input is true, append "T" to output.
5. If input is false, append "F" to output.
6. Return output.
4.2. Parsing HTTP/1 Header Fields into Structured Headers 4.2. Parsing HTTP/1 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, (e.g., in HTTP/1 or HTTP/2) that are known to be Structured Headers,
it is important that care be taken, as there are a number of edge it is important that care be taken, as there are a number of edge
cases that can cause interoperability or even security problems. cases that can cause interoperability or even security problems.
This section specifies the algorithm for doing so. This section specifies the algorithm for doing so.
Given an ASCII string input_string that represents the chosen Given an ASCII string input_string that represents the chosen
header's field-value, and header_type, one of "dictionary", "list", header's field-value, and header_type, one of "dictionary", "list",
skipping to change at page 15, line 37 skipping to change at page 17, line 32
[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, Parameterised Lists and Dictionaries, this has the effect For Lists, Parameterised Lists and Dictionaries, this has the effect
of correctly concatenating all instances of the header field. of correctly concatenating all instances of the header field.
Strings can but SHOULD NOT be split across multiple header instances, Strings can but SHOULD NOT be split across multiple header instances,
because comma(s) inserted upon combination will become part of the because comma(s) inserted upon combination will become part of the
string output by the parser. string output by the parser.
Integers, Floats and Binary Content cannot be split across multiple Integers, Floats and Byte Sequences cannot be split across multiple
headers because the inserted commas will cause parsing to fail. 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 cannot loosen this requirement.
Note that this has the effect of discarding any header field with Note that this has the effect of discarding any header field with
non-ASCII characters in input_string. non-ASCII characters in input_string.
4.2.1. Parsing a Dictionary from Text 4.2.1. Parsing a Dictionary from Text
Given an ASCII string input_string, return a mapping of (identifier, Given an ASCII string input_string, return an ordered map of
item). input_string is modified to remove the parsed value. (identifier, item). input_string is modified to remove the parsed
value.
1. Let dictionary be an empty, unordered mapping. 1. Let dictionary be an empty, ordered map.
2. While input_string is not empty: 2. While input_string is not empty:
1. Let this_key be the result of running Parse Identifier from 1. Let this_key be the result of running Parse Identifier from
Text (Section 4.2.8) with input_string. Text (Section 4.2.8) with input_string.
2. If dictionary already contains this_key, fail parsing. 2. If dictionary already contains this_key, fail parsing.
3. Consume the first character of input_string; if it is not 3. Consume the first character of input_string; if it is not
"=", fail parsing. "=", fail parsing.
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COMMA, fail parsing. COMMA, fail parsing.
6. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
7. If input_string is empty, fail parsing. 7. If input_string is empty, fail parsing.
3. No structured data has been found; fail parsing. 3. No structured data has been found; fail parsing.
4.2.4. Parsing a Parameterised Identifier from Text 4.2.4. Parsing a Parameterised Identifier from Text
Given an ASCII string input_string, return a identifier with an Given an ASCII string input_string, return an identifier with an
mapping of parameters. input_string is modified to remove the parsed unordered map of parameters. input_string is modified to remove the
value. parsed value.
1. Let primary_identifier be the result of Parsing a Identifier from 1. Let primary_identifier be the result of Parsing an Identifier
Text (Section 4.2.8) from input_string. from Text (Section 4.2.8) from input_string.
2. Let parameters be an empty, unordered mapping. 2. Let parameters be an empty, unordered map.
3. In a loop: 3. In a loop:
1. Discard any leading OWS from input_string. 1. If the first character of input_string is not ";", exit the
2. If the first character of input_string is not ";", exit the
loop. loop.
3. Consume a ";" character from the beginning of input_string. 2. Consume a ";" character from the beginning of input_string.
4. Discard any leading OWS from input_string. 3. Discard any leading OWS from input_string.
5. let param_name be the result of Parsing a Identifier from 4. let param_name be the result of Parsing an Identifier from
Text (Section 4.2.8) from input_string. Text (Section 4.2.8) from input_string.
6. If param_name is already present in parameters, fail parsing. 5. If param_name is already present in parameters, fail parsing.
7. Let param_value be a null value. 6. Let param_value be a null value.
8. If the first character of input_string is "=": 7. If the first character of input_string is "=":
1. Consume the "=" character at the beginning of 1. Consume the "=" character at the beginning of
input_string. input_string.
2. Let param_value be the result of Parsing an Item from 2. Let param_value be the result of Parsing an Item from
Text (Section 4.2.5) from input_string. Text (Section 4.2.5) from input_string.
9. Insert (param_name, param_value) into parameters. 8. Insert (param_name, param_value) into parameters.
4. Return the tuple (primary_identifier, parameters). 4. Return the tuple (primary_identifier, parameters).
4.2.5. Parsing an Item from Text 4.2.5. 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. Discard any leading OWS from input_string. 1. Discard any leading OWS from input_string.
2. If the first character of input_string is a "-" or a DIGIT, 2. If the first character of input_string is a "-" or a DIGIT,
process input_string as a number (Section 4.2.6) and return the process input_string as a number (Section 4.2.6) and return the
result. result.
3. If the first character of input_string is a DQUOTE, process 3. If the first character of input_string is a DQUOTE, process
input_string as a string (Section 4.2.7) and return the result. input_string as a string (Section 4.2.7) and return the result.
4. If the first character of input_string is "*", process 4. If the first character of input_string is "*", process
input_string as binary content (Section 4.2.9) and return the input_string as a byte sequence (Section 4.2.9) and return the
result. result.
5. Otherwise, fail parsing. 5. If the first character of input_string is "!", process
input_string as a Boolean (Section 4.2.10) and return the result.
6. If the first character of input_string is a lcalpha, process
input_string as an identifier (Section 4.2.8) and return the
result.
7. Otherwise, fail parsing.
4.2.6. Parsing a Number from Text 4.2.6. Parsing a Number from Text
NOTE: This algorithm parses both Integers Section 3.5 and Floats NOTE: This algorithm parses both Integers Section 3.5 and Floats
Section 3.6, and returns the corresponding structure. Section 3.6, 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.
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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 removing 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, fail parsing. 4. Otherwise, prepend char to input_string, and exit the loop.
5. If type is "integer" and input_number contains more than 19 5. If type is "integer" and input_number contains more than 19
characters, fail parsing. characters, fail parsing.
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 result. 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 3.5, fail parsing. Section 3.5, 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
result. product of the result and sign.
10. Return the product of output_number and sign. 10. Return output_number.
4.2.7. Parsing a String from Text 4.2.7. 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.
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1. Let next_char be the result of removing the first 1. Let next_char be the result of removing 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), fail parsing. in VCHAR or SP), fail parsing.
5. Else, append char to output_string. 5. Else, append char to output_string.
5. Otherwise, fail parsing. 5. Reached the end of input_string without finding a closing DQUOTE;
fail parsing.
4.2.8. Parsing an Identifier from Text 4.2.8. Parsing an Identifier from Text
Given an ASCII string input_string, return a identifier. input_string Given an ASCII string input_string, return an identifier.
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 lcalpha, fail 1. If the first character of input_string is not lcalpha, 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 removing the first character of
input_string. input_string.
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2. If char is not one of lcalpha, DIGIT, "_", "-", "*" or "/": 2. If char is not one of lcalpha, DIGIT, "_", "-", "*" 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.
4.2.9. Parsing Binary Content from Text 4.2.9. Parsing a Byte Sequence from Text
Given an ASCII string input_string, return binary content. 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. Let b64_content be the result of removing content of input_string 3. Let b64_content be the result of removing content of input_string
up to but not including the first instance of the character "*". up to but not including the first instance of the character "*".
If there is not a "*" character before the end of input_string, If there is not a "*" character before the end of input_string,
fail parsing. fail parsing.
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5. If b64_content contains a character not included in ALPHA, DIGIT, 5. If b64_content contains a character not included in ALPHA, DIGIT,
"+", "/" and "=", fail parsing. "+", "/" and "=", fail parsing.
6. Let binary_content be the result of Base 64 Decoding [RFC4648] 6. Let binary_content be the result of Base 64 Decoding [RFC4648]
b64_content, synthesising padding if necessary (note the b64_content, synthesising padding if necessary (note the
requirements about recipient behaviour below). requirements about recipient behaviour below).
7. Return binary_content. 7. Return binary_content.
As per [RFC4648], Section 3.2, it is RECOMMENDED that parsers reject Because some implementations of base64 do not allow reject of encoded
encoded data that is not properly padded, although this might not be data that is not properly "=" padded (see [RFC4648], Section 3.2),
possible in some base64 implementations. parsers SHOULD NOT fail when it is not present, unless they cannot be
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 handle it. 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.
4.2.10. Parsing a Boolean from Text
Given an ASCII string input_string, return a Boolean. input_string is
modified to remove the parsed value.
1. If the first character of input_string is not "!", fail parsing.
2. Discard the first character of input_string.
3. If the first character of input_string case-sensitively matches
"T", discard the first character, and return true.
4. If the first character of input_string case-sensitively matches
"F", discard the first character, and return false.
5. No value has matched; fail parsing.
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 size of individual header fields as well as the overall
header block size to mitigate such attacks. header 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 Headers. 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
[RFC0020] Cerf, V., "ASCII format for network interchange", STD 80, [RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969, RFC 20, DOI 10.17487/RFC0020, October 1969,
<https://www.rfc-editor.org/info/rfc20>. <https://www.rfc-editor.org/info/rfc20>.
skipping to change at page 25, line 38 skipping to change at page 28, line 9
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.
Appendix B. Changes Appendix B. Changes
_RFC Editor: Please remove this section before publication._ _RFC Editor: Please remove this section before publication._
B.1. Since draft-ietf-httpbis-header-structure-06 B.1. Since draft-ietf-httpbis-header-structure-07
o Make Dictionaries ordered mappings (#659).
o Changed "binary content" to "byte sequence" to align with Infra
specification (#671).
o Changed "mapping" to "map" for #671.
o Don't fail if byte sequences aren't "=" padded (#658).
o Add Booleans (#683).
o Allow identifiers in items again (#629).
o Disallowed whitespace before items (#703).
B.2. 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.
B.2. Since draft-ietf-httpbis-header-structure-05 B.3. 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.
B.3. Since draft-ietf-httpbis-header-structure-04 B.4. 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.
B.4. Since draft-ietf-httpbis-header-structure-03 B.5. Since draft-ietf-httpbis-header-structure-03
o Strengthen language around failure handling. o Strengthen language around failure handling.
B.5. Since draft-ietf-httpbis-header-structure-02 B.6. 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.
B.6. Since draft-ietf-httpbis-header-structure-01 B.7. Since draft-ietf-httpbis-header-structure-01
o Replaced with draft-nottingham-structured-headers. o Replaced with draft-nottingham-structured-headers.
B.7. Since draft-ietf-httpbis-header-structure-00 B.8. 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. 86 change blocks. 
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