draft-ietf-httpbis-header-structure-14.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: May 2, 2020 The Varnish Cache Project Expires: June 11, 2020 The Varnish Cache Project
October 30, 2019 December 9, 2019
Structured Headers for HTTP Structured Headers for HTTP
draft-ietf-httpbis-header-structure-14 draft-ietf-httpbis-header-structure-latest
Abstract Abstract
This document describes a set of data types and associated algorithms This document describes a set of data types and associated algorithms
that are intended to make it easier and safer to define and handle that are intended to make it easier and safer to define and handle
HTTP header fields. It is intended for use by specifications of new HTTP header fields. It is intended for use by specifications of new
HTTP header fields that wish to use a common syntax that is more HTTP header fields that wish to use a common syntax that is more
restrictive than traditional HTTP field values. restrictive than traditional HTTP field values.
Note to Readers Note to Readers
skipping to change at page 2, line 10 skipping to change at page 2, line 10
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 May 2, 2020. This Internet-Draft will expire on June 11, 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Intentionally Strict Processing . . . . . . . . . . . . . 4 1.1. Intentionally Strict Processing . . . . . . . . . . . . . 4
1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.2. Notational Conventions . . . . . . . . . . . . . . . . . 5
2. Defining New Structured Headers . . . . . . . . . . . . . . . 5 2. Defining New Structured Headers . . . . . . . . . . . . . . . 5
3. Structured Data Types . . . . . . . . . . . . . . . . . . . . 7 3. Structured Data Types . . . . . . . . . . . . . . . . . . . . 7
3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1.1. Inner Lists . . . . . . . . . . . . . . . . . . . . . 8
3.1.2. Parameters . . . . . . . . . . . . . . . . . . . . . 9
3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 9 3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4. Working With Structured Headers in HTTP Headers . . . . . . . 13 3.3.1. Integers . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Serializing Structured Headers . . . . . . . . . . . . . 13 3.3.2. Floats . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.3. Strings . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.4. Tokens . . . . . . . . . . . . . . . . . . . . . . . 13
3.3.5. Byte Sequences . . . . . . . . . . . . . . . . . . . 13
3.3.6. Booleans . . . . . . . . . . . . . . . . . . . . . . 13
4. Working With Structured Headers in HTTP Headers . . . . . . . 14
4.1. Serializing Structured Headers . . . . . . . . . . . . . 14
4.1.1. Serializing a List . . . . . . . . . . . . . . . . . 14
4.1.2. Serializing a Dictionary . . . . . . . . . . . . . . 16
4.1.3. Serializing an Item . . . . . . . . . . . . . . . . . 17
4.1.4. Serializing an Integer . . . . . . . . . . . . . . . 18
4.1.5. Serializing a Float . . . . . . . . . . . . . . . . . 18
4.1.6. Serializing a String . . . . . . . . . . . . . . . . 19
4.1.7. Serializing a Token . . . . . . . . . . . . . . . . . 19
4.1.8. Serializing a Byte Sequence . . . . . . . . . . . . . 20
4.1.9. Serializing a Boolean . . . . . . . . . . . . . . . . 20
4.2. Parsing Header Fields into Structured Headers . . . . . . 20 4.2. Parsing Header Fields into Structured Headers . . . . . . 20
4.2.1. Parsing a List . . . . . . . . . . . . . . . . . . . 22
4.2.2. Parsing a Dictionary . . . . . . . . . . . . . . . . 23
4.2.3. Parsing an Item . . . . . . . . . . . . . . . . . . . 24
4.2.4. Parsing a Number . . . . . . . . . . . . . . . . . . 26
4.2.5. Parsing a String . . . . . . . . . . . . . . . . . . 28
4.2.6. Parsing a Token . . . . . . . . . . . . . . . . . . . 29
4.2.7. Parsing a Byte Sequence . . . . . . . . . . . . . . . 29
4.2.8. Parsing a Boolean . . . . . . . . . . . . . . . . . . 30
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
6. Security Considerations . . . . . . . . . . . . . . . . . . . 30 6. Security Considerations . . . . . . . . . . . . . . . . . . . 30
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.1. Normative References . . . . . . . . . . . . . . . . . . 30 7.1. Normative References . . . . . . . . . . . . . . . . . . 31
7.2. Informative References . . . . . . . . . . . . . . . . . 31 7.2. Informative References . . . . . . . . . . . . . . . . . 31
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 31 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 32 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 32
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 32 Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 32
B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 32 B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 32
B.2. Structured Headers don't "fit" my data. . . . . . . . . . 33 B.2. Structured Headers don't "fit" my data. . . . . . . . . . 33
Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 33 Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 34
Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 34 Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 34
D.1. Since draft-ietf-httpbis-header-structure-13 . . . . . . 34 D.1. Since draft-ietf-httpbis-header-structure-14 . . . . . . 34
D.2. Since draft-ietf-httpbis-header-structure-12 . . . . . . 34 D.2. Since draft-ietf-httpbis-header-structure-13 . . . . . . 35
D.3. Since draft-ietf-httpbis-header-structure-11 . . . . . . 34 D.3. Since draft-ietf-httpbis-header-structure-12 . . . . . . 35
D.4. Since draft-ietf-httpbis-header-structure-10 . . . . . . 34 D.4. Since draft-ietf-httpbis-header-structure-11 . . . . . . 35
D.5. Since draft-ietf-httpbis-header-structure-09 . . . . . . 35 D.5. Since draft-ietf-httpbis-header-structure-10 . . . . . . 35
D.6. Since draft-ietf-httpbis-header-structure-08 . . . . . . 35 D.6. Since draft-ietf-httpbis-header-structure-09 . . . . . . 36
D.7. Since draft-ietf-httpbis-header-structure-07 . . . . . . 35 D.7. Since draft-ietf-httpbis-header-structure-08 . . . . . . 36
D.8. Since draft-ietf-httpbis-header-structure-06 . . . . . . 36 D.8. Since draft-ietf-httpbis-header-structure-07 . . . . . . 36
D.9. Since draft-ietf-httpbis-header-structure-05 . . . . . . 36 D.9. Since draft-ietf-httpbis-header-structure-06 . . . . . . 37
D.10. Since draft-ietf-httpbis-header-structure-04 . . . . . . 36 D.10. Since draft-ietf-httpbis-header-structure-05 . . . . . . 37
D.11. Since draft-ietf-httpbis-header-structure-03 . . . . . . 36 D.11. Since draft-ietf-httpbis-header-structure-04 . . . . . . 37
D.12. Since draft-ietf-httpbis-header-structure-02 . . . . . . 36 D.12. Since draft-ietf-httpbis-header-structure-03 . . . . . . 37
D.13. Since draft-ietf-httpbis-header-structure-01 . . . . . . 37 D.13. Since draft-ietf-httpbis-header-structure-02 . . . . . . 37
D.14. Since draft-ietf-httpbis-header-structure-00 . . . . . . 37 D.14. Since draft-ietf-httpbis-header-structure-01 . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37 D.15. Since draft-ietf-httpbis-header-structure-00 . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
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 Section 8.3.1 of [RFC7231], there are many even with the guidance in Section 8.3.1 of [RFC7231], 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 serializers 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
skipping to change at page 7, line 32 skipping to change at page 7, line 32
for the message. See below for processing requirements. for the message. See below for processing requirements.
"fooUrl" contains a URI-reference (Section 4.1 of "fooUrl" contains a URI-reference (Section 4.1 of
[RFC3986], Section 4.1). If its value is not a valid URI-reference, [RFC3986], Section 4.1). If its value is not a valid URI-reference,
that URL MUST be ignored. If its value is a relative reference that URL MUST be ignored. If its value is a relative reference
(Section 4.2 of [RFC3986]), it MUST be resolved (Section 5 of (Section 4.2 of [RFC3986]), it MUST be resolved (Section 5 of
[RFC3986]) before being used. [RFC3986]) before being used.
For example: For example:
Foo-Example: 2; fooUrl="https://foo.example.com/" Foo-Example: 2; foourl="https://foo.example.com/"
3. Structured Data Types 3. Structured 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 headers. format in HTTP headers.
In summary: In summary:
o There are three top-level types that a HTTP header can be defined o There are three top-level types that a HTTP header can be defined
skipping to change at page 8, line 52 skipping to change at page 8, line 52
whose value is defined as a list of inner-lists of strings could look whose value is defined as a list of inner-lists of strings could look
like: like:
Example-StrListListHeader: ("foo" "bar"), ("baz"), ("bat" "one"), () Example-StrListListHeader: ("foo" "bar"), ("baz"), ("bat" "one"), ()
Note that the last member in this example is an empty inner list. Note that the last member in this example is an empty inner list.
A header field whose value is defined as a list of inner-lists with A header field whose value is defined as a list of inner-lists with
parameters at both levels could look like: parameters at both levels could look like:
Example-ListListParam: ("foo"; a=1;b=2);lvl=5, ("bar", "baz");lvl=1 Example-ListListParam: ("foo"; a=1;b=2);lvl=5, ("bar" "baz");lvl=1
Parsers MUST support inner-lists containing at least 256 members. Parsers MUST support inner-lists containing at least 256 members.
Header specifications can constrain the types and cardinality of Header specifications can constrain the types and cardinality of
individual inner-list members as they require. individual inner-list members as they require.
3.1.2. Parameters 3.1.2. Parameters
Parameters are an ordered map of key-values pairs that are associated Parameters are an ordered map of key-values pairs that are associated
with an item (Section 3.3) or inner-list (Section 3.1.1). The keys with an item (Section 3.3) or inner-list (Section 3.1.1). The keys
are required to be unique within the scope of a map of parameters, are required to be unique within the scope of a map of parameters,
and the values are bare items (i.e., they themselves cannot be and the values are bare items (i.e., they themselves cannot be
skipping to change at page 9, line 29 skipping to change at page 9, line 29
param-name = key param-name = key
key = lcalpha *( lcalpha / DIGIT / "_" / "-" / "*" ) key = lcalpha *( lcalpha / DIGIT / "_" / "-" / "*" )
lcalpha = %x61-7A ; a-z lcalpha = %x61-7A ; a-z
param-value = bare-item param-value = bare-item
In HTTP headers, parameters are separated from their item or inner- In HTTP headers, parameters are separated from their item or inner-
list and each other by semicolons. For example: list and each other by semicolons. For example:
Example-ParamListHeader: abc;a=1;b=2; cde_456, (ghi;jk=4 l);q="9";r=w Example-ParamListHeader: abc;a=1;b=2; cde_456, (ghi;jk=4 l);q="9";r=w
Parameters whose value is Boolean true MUST omit that value when
serialised. For example:
Example-IntHeader: 1; a; b=?0
Note that this requirement is only on serialisation; parsers are
still required to correctly handle the true value when it appears in
parameters.
Parsers MUST support at least 256 parameters on an item or inner- Parsers MUST support at least 256 parameters on an item or inner-
list, and support parameter keys with at least 64 characters. Header list, and support parameter keys with at least 64 characters. Header
specifications can constrain the types and cardinality of individual specifications can constrain the types and cardinality of individual
parameter names and values as they require. parameter names and values as they require.
3.2. Dictionaries 3.2. Dictionaries
Dictionaries are ordered maps of name-value pairs, where the names Dictionaries are ordered maps of name-value pairs, where the names
are short, textual strings and the values are items (Section 3.3) or are short, textual strings and the values are items (Section 3.3) or
arrays of items, both of which can be parameterised (Section 3.1.2). arrays of items, both of which can be parameterised (Section 3.1.2).
There can be zero or more members, and their names are required to be There can be zero or more members, and their names are required to be
unique within the scope of the dictionary they occur within. unique in the scope of the dictionary they occur within.
Implementations MUST provide access to dictionaries both by index and Implementations MUST provide access to dictionaries both by index and
by name. Specifications MAY use either means of accessing the by name. Specifications MAY use either means of accessing the
members. members.
The ABNF for dictionaries in HTTP headers is: The ABNF for dictionaries in HTTP 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 = key member-name = key
member-value = sh-item / inner-list member-value = sh-item / inner-list
In HTTP headers, members are separated by a comma with optional In HTTP headers, members are separated by a comma with optional
whitespace, while names and values are separated by "=" (without whitespace, while names and values are separated by "=" (without
whitespace). For example: whitespace). For example:
Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=* Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=*
Members whose value is Boolean true MUST omit that value when
serialised, unless it has parameters. For example, here both "b" and
"c" are true, but "c"'s value is serialised because it has
parameters:
Example-DictHeader: a=?0, b, c=?1; foo=bar
Note that this requirement is only on serialisation; parsers are
still required to correctly handle the true value when it appears in
dictionary values.
A dictionary with a member whose value is an inner-list of tokens: A dictionary with a member whose value is an inner-list of tokens:
Example-DictListHeader: rating=1.5, feelings=(joy sadness) Example-DictListHeader: rating=1.5, feelings=(joy sadness)
A dictionary with a mix of singular and list values, some with A dictionary with a mix of singular and list values, some with
parameters: parameters:
Example-MixDict: a=(1 2), b=3, c=4;aa=bb, d=(5 6);valid=?1 Example-MixDict: a=(1 2), b=3, c=4;aa=bb, d=(5 6);valid=?1
As with lists, an empty dictionary is represented in HTTP headers by As with lists, an empty dictionary is represented in HTTP headers by
skipping to change at page 13, line 41 skipping to change at page 14, line 16
This section defines how to serialize and parse Structured Headers in This section defines how to serialize and parse Structured Headers in
header fields, and protocols compatible with them (e.g., in HTTP/2 header fields, and protocols compatible with them (e.g., in HTTP/2
[RFC7540] before HPACK [RFC7541] is applied). [RFC7540] before HPACK [RFC7541] is applied).
4.1. Serializing Structured Headers 4.1. Serializing Structured Headers
Given a structure defined in this specification, return an ASCII Given a structure defined in this specification, return an ASCII
string suitable for use in a HTTP header value. string suitable for use in a HTTP header value.
1. If the structure is a dictionary or list and its value is empty 1. If the structure is a Dictionary or List and its value is empty
(i.e., it has no members), do not serialize the field at all (i.e., it has no members), do not serialize the field at all
(i.e., omit both the field-name and field-value). (i.e., omit both the field-name and field-value).
2. If the structure is a dictionary, let output_string be the result 2. If the structure is a Dictionary, let output_string be the result
of running Serializing a Dictionary (Section 4.1.2) with the of running Serializing a Dictionary (Section 4.1.2) with the
structure. structure.
3. Else if the structure is a list, let output_string be the result 3. Else if the structure is a List, let output_string be the result
of running Serializing a List (Section 4.1.1) with the structure. of running Serializing a List (Section 4.1.1) with the structure.
4. Else if the structure is an item, let output_string be the result 4. Else if the structure is an Item, let output_string be the result
of running Serializing an Item (Section 4.1.3) with the of running Serializing an Item (Section 4.1.3) with the
structure. structure.
5. Else, fail serialisation. 5. Else, fail serialisation.
6. Return output_string converted into an array of bytes, using 6. Return output_string converted into an array of bytes, using
ASCII encoding [RFC0020]. ASCII encoding [RFC0020].
4.1.1. Serializing a List 4.1.1. Serializing a List
Given an array of (member-value, parameters) tuples as input_list, Given an array of (member_value, parameters) tuples as input_list,
return an ASCII string suitable for use in a HTTP header value. return an ASCII string suitable for use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each (member-value, parameters) of input_list: 2. For each (member_value, parameters) of input_list:
1. If member-value is an array, append the result of running 1. If member_value is an array, append the result of running
Serialising an Inner List (Section 4.1.1.1) with (member- Serialising an Inner List (Section 4.1.1.1) with
value, parameters) to output. (member_value, parameters) to output.
2. Otherwise, append the result of running Serializing an Item 2. Otherwise, append the result of running Serializing an Item
(Section 4.1.3) with (member-value, parameters) to output. (Section 4.1.3) with (member_value, parameters) to output.
3. If more member-values remain in input_list: 3. If more member_values remain in input_list:
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.
4.1.1.1. Serialising an Inner List 4.1.1.1. Serialising an Inner List
Given an array of (member-value, parameters) tuples as inner_list, Given an array of (member_value, parameters) tuples as inner_list,
and parameters as list_parameters, return an ASCII string suitable and parameters as list_parameters, return an ASCII string suitable
for use in a HTTP header value. for use in a HTTP header value.
1. Let output be the string "(". 1. Let output be the string "(".
2. For each (member-value, parameters) of inner_list: 2. For each (member_value, parameters) of inner_list:
1. Append the result of running Serializing an Item 1. Append the result of running Serializing an Item
(Section 4.1.3) with (member-value, parameters) to output. (Section 4.1.3) with (member_value, parameters) to output.
2. If more values remain in inner_list, append a single WS to 2. If more values remain in inner_list, append a single WS to
output. output.
3. Append ")" to output. 3. Append ")" to output.
4. Append the result of running Serializing Parameters 4. Append the result of running Serializing Parameters
Section 4.1.1.2 with list_parameters to output. Section 4.1.1.2 with list_parameters to output.
5. Return output. 5. Return output.
4.1.1.2. Serializing Parameters 4.1.1.2. Serializing Parameters
Given an ordered dictionary as input_parameters (each member having a Given an ordered dictionary as input_parameters (each member having a
param-name and a param-value), return an ASCII string suitable for param_name and a param_value), return an ASCII string suitable for
use in a HTTP header value. use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each parameter-name with a value of param-value in 2. For each parameter-name with a value of param_value in
input_parameters: input_parameters:
1. Append ";" to output. 1. Append ";" to output.
2. Append the result of running Serializing a Key 2. Append the result of running Serializing a Key
(Section 4.1.1.3) with param-name to output. (Section 4.1.1.3) with param_name to output.
3. If param-value is not null: 3. If param_value is not Boolean true:
1. Append "=" to output. 1. Append "=" to output.
2. Append the result of running Serializing a bare Item 2. Append the result of running Serializing a bare Item
(Section 4.1.3.1) with param-value to output. (Section 4.1.3.1) with param_value to output.
3. Return output. 3. Return output.
4.1.1.3. Serializing a Key 4.1.1.3. Serializing a Key
Given a key as input_key, return an ASCII string suitable for use in Given a key as input_key, return an ASCII string suitable for use in
a HTTP header value. a HTTP header value.
1. If input_key is not a sequence of characters, or contains 1. If input_key is not a sequence of characters, or contains
characters not in lcalpha, DIGIT, "*", "_", or "-", fail characters not in lcalpha, DIGIT, "*", "_", or "-", fail
skipping to change at page 16, line 8 skipping to change at page 16, line 28
2. Let output be an empty string. 2. Let output be an empty string.
3. Append input_key to output. 3. Append input_key to output.
4. Return output. 4. Return output.
4.1.2. Serializing a Dictionary 4.1.2. Serializing a Dictionary
Given an ordered dictionary as input_dictionary (each member having a Given an ordered dictionary as input_dictionary (each member having a
member-name and a tuple value of (member-value, parameters)), return member_name and a tuple value of (member_value, parameters)), return
an ASCII string suitable for use in a HTTP header value. an ASCII string suitable for use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each member-name with a value of (member-value, parameters) 2. For each member_name with a value of (member_value, parameters)
in input_dictionary: in input_dictionary:
1. Append the result of running Serializing a Key 1. Append the result of running Serializing a Key
(Section 4.1.1.3) with member's member-name to output. (Section 4.1.1.3) with member's member_name to output.
2. Append "=" to output. 3. If member_value is not Boolean true or parameters is not empty:
3. If member-value is an array, append the result of running 1. Append "=" to output.
Serialising an Inner List (Section 4.1.1.1) with (member-
value, parameters) to output.
4. Otherwise, append the result of running Serializing an Item 1. If member_value is an array, append the result of running
(Section 4.1.3) with (member-value, parameters) to output. Serialising an Inner List (Section 4.1.1.1) with
(member_value, parameters) to output.
5. If more members remain in input_dictionary: 2. Otherwise, append the result of running Serializing an
Item (Section 4.1.3) with (member_value, parameters) to
output.
1. Append a COMMA to output. 4. If more members remain in input_dictionary:
2. Append a single WS to output. 1. Append a COMMA to output.
3. Return output. 2. Append a single WS to output.
5. Return output.
4.1.3. Serializing an Item 4.1.3. Serializing an Item
Given an item bare_item and parameters item_parameters as input, Given an item bare_item and parameters item_parameters as input,
return an ASCII string suitable for use in a HTTP header value. return an ASCII string suitable for use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. Append the result of running Serializing a Bare Item 2. Append the result of running Serializing a Bare Item
Section 4.1.3.1 with bare_item to output. Section 4.1.3.1 with bare_item to output.
skipping to change at page 18, line 31 skipping to change at page 18, line 50
5. If integer_digits is greater than 14, fail serialisation. 5. If integer_digits is greater than 14, fail serialisation.
6. Let digits_avail be 15 minus integer_digits. 6. Let digits_avail be 15 minus integer_digits.
7. Let fractional_digits_avail be the minimum of digits_avail and 7. Let fractional_digits_avail be the minimum of digits_avail and
6. 6.
8. Append "." to output. 8. Append "." to output.
9. Append at most fractional_digits_avail digits of input_float's 9. If input_float's fractional component is 0, append "0" to
fractional component represented in base 10 to output (using output.
only decimal digits, and truncating any remaining digits); if it
is zero, append "0".
10. Return output. 10. Else if input_float's fractional component has
fractional_digits_avail or less digits, append input_float's
fractional component represented in base 10 to output.
11. Else append fractional_digits_avail digits of input_float's
fractional component represented in base 10 to output, rounding
to the nearest value, or to the even value if it is equidistant.
12. Return output.
4.1.6. Serializing a String 4.1.6. Serializing a String
Given a string as input_string, return an ASCII string suitable for Given a string as input_string, return an ASCII string suitable for
use in a HTTP header value. use in a HTTP header value.
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 in the range %x00-1f or %x7f (i.e., is not in VCHAR or characters in the range %x00-1f or %x7f (i.e., is not in VCHAR or
SP), fail serialisation. SP), fail serialisation.
skipping to change at page 19, line 20 skipping to change at page 19, line 45
5. Append DQUOTE to output. 5. Append DQUOTE to output.
6. Return output. 6. Return output.
4.1.7. Serializing a Token 4.1.7. Serializing a Token
Given a token as input_token, return an ASCII string suitable for use Given a token as input_token, return an ASCII string suitable for use
in a HTTP header value. in a HTTP header value.
1. If input_token is not a sequence of characters, or contains 1. If input_token is not a sequence of characters, or contains a
characters not allowed by the tchar ABNF rule, fail character not in tchar, ":" or "/", fail serialisation.
serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append input_token to output. 3. Append input_token to output.
4. Return output. 4. Return output.
4.1.8. Serializing a Byte Sequence 4.1.8. Serializing a Byte Sequence
Given a byte sequence as input_bytes, return an ASCII string suitable Given a byte sequence as input_bytes, return an ASCII string suitable
skipping to change at page 23, line 38 skipping to change at page 24, line 13
1. Let dictionary be an empty, ordered map. 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 Parsing a Key 1. Let this_key be the result of running Parsing a Key
(Section 4.2.3.3) with input_string. (Section 4.2.3.3) with input_string.
2. If dictionary already contains the name this_key, there is a 2. If dictionary already contains the name this_key, there is a
duplicate; fail parsing. duplicate; fail parsing.
3. Consume the first character of input_string; if it is not 3. If the first character of input_string is "=":
"=", fail parsing.
4. Let member be the result of running Parsing an Item or Inner 1. Consume the first character of input_string.
List (Section 4.2.1.1) with input_string.
2. Let member be the result of running Parsing an Item or
Inner List (Section 4.2.1.1) with input_string.
4. Otherwise:
1. Let value be Boolean true.
2. Let parameters be an empty, ordered map.
3. Let member be the tuple (value, parameters).
5. Add name this_key with value member to dictionary. 5. Add name this_key with value member to dictionary.
6. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
7. If input_string is empty, return dictionary. 7. If input_string is empty, return dictionary.
8. Consume the first character of input_string; if it is not 8. Consume the first character of input_string; if it is not
COMMA, fail parsing. COMMA, fail parsing.
skipping to change at page 25, line 28 skipping to change at page 26, line 11
2. Consume a ";" character from the beginning of input_string. 2. Consume a ";" character from the beginning of input_string.
3. Discard any leading OWS from input_string. 3. Discard any leading OWS from input_string.
4. let param_name be the result of running Parsing a Key 4. let param_name be the result of running Parsing a Key
(Section 4.2.3.3) with input_string. (Section 4.2.3.3) with input_string.
5. If param_name is already present in parameters, there is a 5. If param_name is already present in parameters, there is a
duplicate; fail parsing. duplicate; fail parsing.
6. Let param_value be a null value. 6. Let param_value be Boolean true.
7. 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 running Parsing a Bare 2. Let param_value be the result of running Parsing a Bare
Item (Section 4.2.3.1) with input_string. Item (Section 4.2.3.1) with input_string.
8. Append key param_name with value param_value to parameters. 8. Append key param_name with value param_value to parameters.
3. Return parameters. 3. Return parameters.
4.2.3.3. Parsing a Key from Text 4.2.3.3. Parsing a Key
Given an ASCII string as input_string, return a key. input_string is Given an ASCII string as input_string, return a key. 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 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:
skipping to change at page 26, line 15 skipping to change at page 26, line 47
1. If the first character of input_string is not one of lcalpha, 1. If the first character of input_string is not one of lcalpha,
DIGIT, "*", "_", or "-", return output_string. DIGIT, "*", "_", or "-", return output_string.
2. Let char be the result of removing the first character of 2. Let char be the result of removing the first character of
input_string. input_string.
3. Append char to output_string. 3. Append char to output_string.
4. Return output_string. 4. Return output_string.
4.2.4. Parsing a Number from Text 4.2.4. Parsing a Number
Given an ASCII string as input_string, return a number. input_string Given an ASCII string as input_string, return a number. input_string
is modified to remove the parsed value. is modified to remove the parsed value.
NOTE: This algorithm parses both Integers (Section 3.3.1) and Floats NOTE: This algorithm parses both Integers (Section 3.3.1) and Floats
(Section 3.3.2), and returns the corresponding structure. (Section 3.3.2), 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.
skipping to change at page 27, line 13 skipping to change at page 27, line 46
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 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 -999,999,999,999,999
Section 3.3.1, fail parsing. to 999,999,999,999,999 inclusive, 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. If the number of characters after "." in input_number is 2. If the number of characters after "." in input_number is
greater than six, fail parsing. greater than six, fail parsing.
3. Parse input_number as a float and let output_number be the 3. 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.
4.2.5. Parsing a String from Text 4.2.5. Parsing a String
Given an ASCII string as input_string, return an unquoted string. Given an ASCII string as 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.
skipping to change at page 28, line 17 skipping to change at page 29, line 5
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.
4.2.6. Parsing a Token from Text 4.2.6. Parsing a Token
Given an ASCII string as input_string, return a token. input_string Given an ASCII string as input_string, return a token. input_string
is modified to remove the parsed value. is 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. If the first character of input_string is not allowed by the 1. If the first character of input_string is not in tchar, ":"
tchar ABNF rule, return output_string. or "/", return output_string.
2. Let char be the result of consuming the first character of 2. Let char be the result of consuming the first character of
input_string. input_string.
3. Append char to output_string. 3. Append char to output_string.
4. Return output_string. 4. Return output_string.
4.2.7. Parsing a Byte Sequence from Text 4.2.7. Parsing a Byte Sequence
Given an ASCII string as input_string, return a byte sequence. Given an ASCII string as 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.
skipping to change at page 29, line 34 skipping to change at page 30, line 19
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.
4.2.8. Parsing a Boolean from Text 4.2.8. Parsing a Boolean
Given an ASCII string as input_string, return a Boolean. input_string Given an ASCII string as input_string, return a Boolean. input_string
is modified to remove the parsed value. 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 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 33, line 22 skipping to change at page 33, line 52
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 an array of key/value pairs, we use a Since the description contains an array of key/value pairs, we use a
List to represent them, with the token for each item in the array List to represent them, with the token for each item in the array
used to identify it in the "descriptions" member of the Example-Thing used to identify it in the "descriptions" member of the Example-Thing
header. dictionary 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.
Appendix C. Implementation Notes Appendix C. Implementation Notes
skipping to change at page 34, line 9 skipping to change at page 34, line 39
Likewise, implementations should note that it's important to preserve Likewise, implementations should note that it's important to preserve
the distinction between tokens and strings. While most programming the distinction between tokens and strings. While most programming
languages have native types that map to the other types well, it may 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 be necessary to create a wrapper "token" object or use a parameter on
functions to assure that these types remain separate. functions to assure that these types remain separate.
Appendix D. Changes Appendix D. Changes
_RFC Editor: Please remove this section before publication._ _RFC Editor: Please remove this section before publication._
D.1. Since draft-ietf-httpbis-header-structure-13 D.1. Since draft-ietf-httpbis-header-structure-14
o Editorial improvements.
o Round the fractional component of floats, rather than truncating
it (#982).
o Allow empty dictionary values (#992).
o Change value of omitted parameter value to True (#995).
D.2. Since draft-ietf-httpbis-header-structure-13
o Editorial improvements. o Editorial improvements.
o Define "structured header name" and "structured header value" o Define "structured header name" and "structured header value"
terms (#908). terms (#908).
o Corrected text about valid characters in strings (#931). o Corrected text about valid characters in strings (#931).
o Removed most instances of the word "textual", as it was redundant o Removed most instances of the word "textual", as it was redundant
(#915). (#915).
o Allowed parameters on Items and Inner Lists (#907). o Allowed parameters on Items and Inner Lists (#907).
o Expand the range of characters in token (#961). o Expand the range of characters in token (#961).
o Disallow OWS before ";" delimiter in parameters (#961). o Disallow OWS before ";" delimiter in parameters (#961).
D.2. Since draft-ietf-httpbis-header-structure-12 D.3. Since draft-ietf-httpbis-header-structure-12
o Editorial improvements. o Editorial improvements.
o Reworked float serialisation (#896). o Reworked float serialisation (#896).
o Don't add a trailing space in inner-list (#904). o Don't add a trailing space in inner-list (#904).
D.3. Since draft-ietf-httpbis-header-structure-11 D.4. Since draft-ietf-httpbis-header-structure-11
o Allow * in key (#844). o Allow * in key (#844).
o Constrain floats to six digits of precision (#848). o Constrain floats to six digits of precision (#848).
o Allow dictionary members to have parameters (#842). o Allow dictionary members to have parameters (#842).
D.4. Since draft-ietf-httpbis-header-structure-10 D.5. Since draft-ietf-httpbis-header-structure-10
o Update abstract (#799). o Update abstract (#799).
o Input and output are now arrays of bytes (#662). o Input and output are now arrays of bytes (#662).
o Implementations need to preserve difference between token and o Implementations need to preserve difference between token and
string (#790). string (#790).
o Allow empty dictionaries and lists (#781). o Allow empty dictionaries and lists (#781).
o Change parameterized lists to have primary items (#797). o Change parameterized lists to have primary items (#797).
o Allow inner lists in both dictionaries and lists; removes lists of o Allow inner lists in both dictionaries and lists; removes lists of
lists (#816). lists (#816).
o Subsume Parameterised Lists into Lists (#839). o Subsume Parameterised Lists into Lists (#839).
D.5. Since draft-ietf-httpbis-header-structure-09 D.6. 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).
D.6. Since draft-ietf-httpbis-header-structure-08 D.7. 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 35, line 44 skipping to change at page 36, line 42
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).
D.7. Since draft-ietf-httpbis-header-structure-07 D.8. 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).
D.8. Since draft-ietf-httpbis-header-structure-06 D.9. 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.
D.9. Since draft-ietf-httpbis-header-structure-05 D.10. 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.
D.10. Since draft-ietf-httpbis-header-structure-04 D.11. 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.
D.11. Since draft-ietf-httpbis-header-structure-03 D.12. Since draft-ietf-httpbis-header-structure-03
o Strengthen language around failure handling. o Strengthen language around failure handling.
D.12. Since draft-ietf-httpbis-header-structure-02 D.13. 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.
D.13. Since draft-ietf-httpbis-header-structure-01 D.14. Since draft-ietf-httpbis-header-structure-01
o Replaced with draft-nottingham-structured-headers. o Replaced with draft-nottingham-structured-headers.
D.14. Since draft-ietf-httpbis-header-structure-00 D.15. 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. 74 change blocks. 
101 lines changed or deleted 176 lines changed or added

This html diff was produced by rfcdiff 1.44jr. The latest version is available from http://tools.ietf.org/tools/rfcdiff/