draft-ietf-httpbis-retrofit-01.txt   draft-ietf-httpbis-retrofit-02.txt 
Network Working Group M. Nottingham Network Working Group M. Nottingham
Internet-Draft 23 April 2022 Internet-Draft 11 May 2022
Intended status: Standards Track Intended status: Standards Track
Expires: 25 October 2022 Expires: 12 November 2022
Retrofit Structured Fields for HTTP Retrofit Structured Fields for HTTP
draft-ietf-httpbis-retrofit-01 draft-ietf-httpbis-retrofit-02
Abstract Abstract
This specification defines how a selection of existing HTTP fields This specification nominates a selection of existing HTTP fields as
can be handled as Structured Fields. having syntax that is compatible with Structured Fields, so that they
can be handled as such (subject to certain caveats).
To accommodate some additional fields whose syntax is not compatible,
it also defines mappings of their semantics into new Structured
Fields. It does not specify how to negotiate their use.
About This Document About This Document
This note is to be removed before publishing as an RFC. This note is to be removed before publishing as an RFC.
Status information for this document may be found at Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-httpbis-retrofit/. https://datatracker.ietf.org/doc/draft-ietf-httpbis-retrofit/.
Discussion of this document takes place on the HTTP Working Group Discussion of this document takes place on the HTTP Working Group
mailing list (mailto:ietf-http-wg@w3.org), which is archived at mailing list (mailto:ietf-http-wg@w3.org), which is archived at
skipping to change at page 1, line 45 skipping to change at page 2, line 4
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 12 November 2022.
This Internet-Draft will expire on 25 October 2022.
Copyright Notice Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the Copyright (c) 2022 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 (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 30 skipping to change at page 2, line 31
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Compatible Fields . . . . . . . . . . . . . . . . . . . . . . 3 2. Compatible Fields . . . . . . . . . . . . . . . . . . . . . . 3
3. Mapped Fields . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Mapped Fields . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. URLs . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. URLs . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Dates . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2. Dates . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. ETags . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3. ETags . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Links . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4. Links . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.5. Cookies . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.5. Cookies . . . . . . . . . . . . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. Normative References . . . . . . . . . . . . . . . . . . . . 12 6. Normative References . . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
Structured Field Values for HTTP [STRUCTURED-FIELDS] introduced a Structured Field Values for HTTP [STRUCTURED-FIELDS] introduced a
data model with associated parsing and serialization algorithms for data model with associated parsing and serialization algorithms for
use by new HTTP field values. Header fields that are defined as use by new HTTP field values. Fields that are defined as Structured
Structured Fields can realise a number of benefits, including: Fields can realise a number of benefits, including:
* Improved interoperability and security: precisely defined parsing * Improved interoperability and security: precisely defined parsing
and serialisation algorithms are typically not available for and serialisation algorithms are typically not available for
fields defined with just ABNF and/or prose. fields defined with just ABNF and/or prose.
* Reuse of common implementations: many parsers for other fields are * Reuse of common implementations: many parsers for other fields are
specific to a single field or a small family of fields specific to a single field or a small family of fields.
* Canonical form: because a deterministic serialisation algorithm is * Canonical form: because a deterministic serialisation algorithm is
defined for each type, Structure Fields have a canonical defined for each type, Structure Fields have a canonical
representation representation.
* Enhanced API support: a regular data model makes it easier to * Enhanced API support: a regular data model makes it easier to
expose field values as a native data structure in implementations expose field values as a native data structure in implementations.
* Alternative serialisations: While [STRUCTURED-FIELDS] defines a * Alternative serialisations: While [STRUCTURED-FIELDS] defines a
textual serialisation of that data model, other, more efficient textual serialisation of that data model, other, more efficient
serialisations of the underlying data model are also possible. serialisations of the underlying data model are also possible.
However, a field needs to be defined as a Structured Field for these However, a field needs to be defined as a Structured Field for these
benefits to be realised. Many existing fields are not, making up the benefits to be realised. Many existing fields are not, making up the
bulk of header and trailer fields seen in HTTP traffic on the bulk of header and trailer fields seen in HTTP traffic on the
internet. internet.
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can be handled as Structured Fields, so that these benefits can be can be handled as Structured Fields, so that these benefits can be
realised -- thereby making them Retrofit Structured Fields. realised -- thereby making them Retrofit Structured Fields.
It does so using two techniques. Section 2 lists compatible fields It does so using two techniques. Section 2 lists compatible fields
-- those that can be handled as if they were Structured Fields due to -- those that can be handled as if they were Structured Fields due to
the similarity of their defined syntax to that in Structured Fields. the similarity of their defined syntax to that in Structured Fields.
Section 3 lists mapped fields -- those whose syntax needs to be Section 3 lists mapped fields -- those whose syntax needs to be
transformed into an underlying data model which is then mapped into transformed into an underlying data model which is then mapped into
that defined by Structured Fields. that defined by Structured Fields.
While implementations can parse and serialise compatible fields as Note that while implementations can parse and serialise compatible
Structured Fields subject to the caveats in Section 2, a sender fields as Structured Fields subject to the caveats in Section 2, a
cannot generate mapped fields from Section 3 and expect them to be sender cannot generate mapped fields from Section 3 and expect them
understood and acted upon by the recipient without prior negotiation. to be understood and acted upon by the recipient without prior
This specification does not define such a mechanism. negotiation. This specification does not define such a mechanism.
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 "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Compatible Fields 2. Compatible Fields
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+----------------------------------+-----------------+ +----------------------------------+-----------------+
| Vary | List | | Vary | List |
+----------------------------------+-----------------+ +----------------------------------+-----------------+
| X-Content-Type-Options | Item | | X-Content-Type-Options | Item |
+----------------------------------+-----------------+ +----------------------------------+-----------------+
| X-Frame-Options | Item | | X-Frame-Options | Item |
+----------------------------------+-----------------+ +----------------------------------+-----------------+
| X-XSS-Protection | List | | X-XSS-Protection | List |
+----------------------------------+-----------------+ +----------------------------------+-----------------+
Table 1 Table 1: Compatible Fields
Note the following caveats regarding compatibility: Note the following caveats regarding compatibility:
Parameter and Dictionary keys: HTTP parameter names are case- Parameter and Dictionary keys: HTTP parameter names are case-
insensitive (per Section 5.6.6 of [HTTP]), but Structured Fields insensitive (per Section 5.6.6 of [HTTP]), but Structured Fields
require them to be all-lowercase. Although the vast majority of require them to be all-lowercase. Although the vast majority of
parameters seen in typical traffic are all-lowercase, parameters seen in typical traffic are all-lowercase,
compatibility can be improved by force-lowercasing parameters when compatibility can be improved by force-lowercasing parameters when
encountered. Likewise, many Dictionary-based fields (e.g., Cache- encountered. Likewise, many Dictionary-based fields (e.g., Cache-
Control, Expect-CT, Pragma, Prefer, Preference-Applied, Surrogate- Control, Expect-CT, Pragma, Prefer, Preference-Applied, Surrogate-
Control) have case-insensitive keys, and compatibility can be Control) have case-insensitive keys, and compatibility can be
improved by force-lowercasing them. improved by force-lowercasing them.
Parameter delimitation: The parameters rule in HTTP (see Parameter delimitation: The parameters rule in HTTP (see
Section 5.6.6 of [HTTP]) allows whitespace before the ";" Section 5.6.6 of [HTTP]) allows whitespace before the ";"
delimiter, but Structured Fields does not. Compatibility can be delimiter, but Structured Fields does not. Compatibility can be
improved by allowing such whitespace. improved by allowing such whitespace.
String quoting: Section 5.6.4 of [HTTP] allows backslash-escaping String quoting: Section 5.6.4 of [HTTP] allows backslash-escaping
most characters in quoted strings, whereas Structured Field most characters in quoted strings, whereas Structured Field
Strings only escapes "" and DQUOTE. Compatibility can be improved Strings only escape "\" and DQUOTE. Compatibility can be improved
by unescaping other characters before processing as Strings. by unescaping other characters before processing as Strings.
Token limitations: In Structured Fields, tokens are required to Token limitations: In Structured Fields, tokens are required to
begin with an alphabetic character or "*", whereas HTTP tokens begin with an alphabetic character or "*", whereas HTTP tokens
allow a wider range of characters. This prevents use of mapped allow a wider range of characters. This prevents use of mapped
values that begin with one of these characters. For example, values that begin with one of these characters. For example,
media types, field names, methods, range-units, character and media types, field names, methods, range-units, character and
transfer codings that begin with a number or special character transfer codings that begin with a number or special character
other than "*" might be valid HTTP protocol elements, but will not other than "*" might be valid HTTP protocol elements, but will not
be able to be parsed as Structured Field Tokens. be able to be parsed as Structured Field Tokens.
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not uncommon for implementations to mistakenly send multiple not uncommon for implementations to mistakenly send multiple
values. See Section 8.6 of [HTTP] for handling requirements. values. See Section 8.6 of [HTTP] for handling requirements.
Retry-After: Only the delta-seconds form of Retry-After is Retry-After: Only the delta-seconds form of Retry-After is
supported; a Retry-After value containing a http-date will need to supported; a Retry-After value containing a http-date will need to
be either converted into delta-seconds or represented as a raw be either converted into delta-seconds or represented as a raw
value. value.
3. Mapped Fields 3. Mapped Fields
Some HTTP fields can have their values represented in Structured Some HTTP field values have syntax that cannot be successfully parsed
Fields by mapping them into its data types and then serialising the as Structured Fields. Instead, it is necessary to map them into a
result using an alternative field name. separate Structured Field with an alternative name.
For example, the Date HTTP header field carries a string representing For example, the Date HTTP header field carries a date:
a date:
Date: Sun, 06 Nov 1994 08:49:37 GMT Date: Sun, 06 Nov 1994 08:49:37 GMT
Its value is more efficiently represented as an integer number of Its value is more efficiently represented as an Integer number of
delta seconds from the Unix epoch (00:00:00 UTC on 1 January 1970, delta seconds from the Unix epoch (00:00:00 UTC on 1 January 1970,
minus leap seconds). Thus, the example above would be mapped as: minus leap seconds). Thus, the example above would be mapped to:
SF-Date: 784072177 SF-Date: 784072177
As in Section 2, these fields are unable to represent values that are As in Section 2, these fields are unable to carry values that are not
not parseable, and so an application using this specification will valid Structured Fields, and so an application using this
need to how to support such values. Typically, handling them using specification will need to how to support such values. Typically,
the original field name is sufficient. handling them using the original field name is sufficient.
Each field name listed below indicates a replacement field name and a Each field name listed below indicates a replacement field name and a
means of mapping its original value into a Structured Field. means of mapping its original value into a Structured Field.
3.1. URLs 3.1. URLs
The field names in Table 2 (paired with their mapped field names) The field names in Table 2 (paired with their mapped field names)
have values that can be represented as Structured Fields by have values that can be mapped into Structured Fields by treating the
considering the original field's value as a string. original field's value as a String.
+==================+=====================+ +==================+=====================+
| Field Name | Mapped Field Name | | Field Name | Mapped Field Name |
+==================+=====================+ +==================+=====================+
| Content-Location | SF-Content-Location | | Content-Location | SF-Content-Location |
+------------------+---------------------+ +------------------+---------------------+
| Location | SF-Location | | Location | SF-Location |
+------------------+---------------------+ +------------------+---------------------+
| Referer | SF-Referer | | Referer | SF-Referer |
+------------------+---------------------+ +------------------+---------------------+
Table 2 Table 2: URL Fields
For example, a Location field could be represented as: For example, a Location field could be mapped as:
SF-Location: "https://example.com/foo" SF-Location: "https://example.com/foo"
3.2. Dates 3.2. Dates
The field names in Table 3 (paired with their mapped field names) The field names in Table 3 (paired with their mapped field names)
have values that can be represented as Structured Fields by parsing have values that can be mapped into Structured Fields by parsing
their payload according to Section 5.6.7 of [HTTP] and representing their payload according to Section 5.6.7 of [HTTP] and representing
the result as an integer number of seconds delta from the Unix Epoch the result as an Integer number of seconds delta from the Unix Epoch
(00:00:00 UTC on 1 January 1970, minus leap seconds). (00:00:00 UTC on 1 January 1970, minus leap seconds).
+=====================+===================+ +=====================+===================+
| Field Name | Mapped Field Name | | Field Name | Mapped Field Name |
+=====================+===================+ +=====================+===================+
| Date | SF-Date | | Date | SF-Date |
+---------------------+-------------------+ +---------------------+-------------------+
| Expires | SF-Expires | | Expires | SF-Expires |
+---------------------+-------------------+ +---------------------+-------------------+
| If-Modified-Since | SF-IMS | | If-Modified-Since | SF-IMS |
+---------------------+-------------------+ +---------------------+-------------------+
| If-Unmodified-Since | SF-IUS | | If-Unmodified-Since | SF-IUS |
+---------------------+-------------------+ +---------------------+-------------------+
| Last-Modified | SF-LM | | Last-Modified | SF-LM |
+---------------------+-------------------+ +---------------------+-------------------+
Table 3 Table 3: Date Fields
For example, an Expires field could be represented as: For example, an Expires field could be mapped as:
SF-Expires: 1571965240 SF-Expires: 1571965240
3.3. ETags 3.3. ETags
The field value of the ETag header field can be represented as a The field value of the ETag header field can be mapped into the SF-
String Structured Field by representing the entity-tag as a string, ETag Structured Field by representing the entity-tag as a String, and
and the weakness flag as a boolean "w" parameter on it, where true the weakness flag as a Boolean "w" parameter on it, where true
indicates that the entity-tag is weak; if 0 or unset, the entity-tag indicates that the entity-tag is weak; if 0 or unset, the entity-tag
is strong. is strong.
For example: For example:
SF-ETag: "abcdef"; w=?1 SF-ETag: "abcdef"; w=?1
If-None-Match's field value can be represented as SF-INM, which is a If-None-Match's field value can be mapped into the SF-INM Structured
List of the structure described above. Field, which is a List of the structure described above.
For example: For example:
SF-INM: "abcdef"; w=?1, "ghijkl" SF-INM: "abcdef"; w=?1, "ghijkl"
3.4. Links 3.4. Links
The field value of the Link header field [RFC8288] can be represented The field value of the Link header field [RFC8288] can be mapped into
in the SF-Link List Structured Field by representing the URI- the SF-Link List Structured Field by considering the URI-Reference as
Reference as a string, and link-param as parameters. a String, and link-param as Parameters.
For example: For example:
SF-Link: "/terms"; rel="copyright"; anchor="#foo" SF-Link: "/terms"; rel="copyright"; anchor="#foo"
3.5. Cookies 3.5. Cookies
The field values of the Cookie and Set-Cookie fields [RFC6265] can be The field values of the Cookie and Set-Cookie fields [COOKIES] can be
represented in the SF-Cookie Structured Field (a List) and SF-Set- mapped into the SF-Cookie Structured Field (a List) and SF-Set-Cookie
Cookie Structured Field (a Dictionary), respectively. Structured Field (a Dictionary), respectively.
In each case, cookie names are serialized as tokens, whereas their In each case, cookie names are Tokens. Their values are Strings,
values are serialised as Strings, unless they can be represented unless they can be represented accurately and unambiguously using the
accurately and unambiguously using the textual representation of textual representation of another structured types (e.g., an Integer
another structured types (e.g., an Integer or Decimal). or Decimal).
Set-Cookie parameters map to parameters on the appropriate SF-Set- Set-Cookie parameters map to Parameters on the appropriate SF-Set-
Cookie member, with the parameter name being forced to lowercase. Cookie member, with the parameter name being forced to lowercase.
Set-Cookie parameter values are Strings unless a specific type is Set-Cookie parameter values are Strings unless a specific type is
defined. This specification defines the parameter types in Table 4. defined for them. This specification defines the parameter types in
Table 4.
+================+=================+ +================+=================+
| Parameter Name | Structured Type | | Parameter Name | Structured Type |
+================+=================+ +================+=================+
| HttpOnly | Boolean |
+----------------+-----------------+
| Expires | Integer |
+----------------+-----------------+
| Max-Age | Integer | | Max-Age | Integer |
+----------------+-----------------+ +----------------+-----------------+
| Secure | Boolean | | Secure | Boolean |
+----------------+-----------------+ +----------------+-----------------+
| HttpOnly | Boolean |
+----------------+-----------------+
| SameSite | Token | | SameSite | Token |
+----------------+-----------------+ +----------------+-----------------+
Table 4 Table 4: Set-Cookie Parameter Types
Note that cookies in both fields are separated by commas, not Expires is mapped to an Integer representation of parsed-cookie-date
semicolons, and multiple cookies can appear in each field. (see Part x.x of [COOKIES]) expressed as a number of seconds delta
from the Unix Epoch (00:00:00 UTC on 1 January 1970, minus leap
seconds).
Note that although this mapping is very similar to the syntax of
Cookie and Set-Cookie headers, cookies in both fields are separated
by commas, not semicolons, and multiple cookies can appear in each
field.
For example: For example:
SF-Set-Cookie: lang=en-US; expires="Wed, 09 Jun 2021 10:18:14 GMT"; SF-Set-Cookie: lang="en-US"; expires="Wed, 09 Jun 2021 10:18:14 GMT";
samesite=Strict samesite=Strict; secure=?1
SF-Cookie: SID=31d4d96e407aad42, lang=en-US SF-Cookie: SID="31d4d96e407aad42", lang="en-US"
4. IANA Considerations 4. IANA Considerations
Please add the following note to the "Hypertext Transfer Protocol Please add the following note to the "Hypertext Transfer Protocol
(HTTP) Field Name Registry": (HTTP) Field Name Registry":
The "Structured Type" column indicates the type of the field (per The "Structured Type" column indicates the type of the field (per
RFC8941), if any, and may be "Dictionary", "List" or "Item". A RFC8941), if any, and may be "Dictionary", "List" or "Item". A
prefix of "*" indicates that it is a retrofit type (i.e., not prefix of "*" indicates that it is a retrofit type (i.e., not
natively Structured); see [this specification]. natively Structured); see [this specification].
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Then, add the field names in Table 5, with the corresponding Then, add the field names in Table 5, with the corresponding
Structured Type as indicated, a status of "permanent" and referring Structured Type as indicated, a status of "permanent" and referring
to this document. to this document.
+=====================+=================+ +=====================+=================+
| Field Name | Structured Type | | Field Name | Structured Type |
+=====================+=================+ +=====================+=================+
| SF-Content-Location | String | | SF-Content-Location | String |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-Location | String | | SF-Cookie | List |
+---------------------+-----------------+
| SF-Referer | String |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-Date | Item | | SF-Date | Item |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-ETag | Item |
+---------------------+-----------------+
| SF-Expires | Item | | SF-Expires | Item |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-IMS | Item | | SF-IMS | Item |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-INM | List |
+---------------------+-----------------+
| SF-IUS | Item | | SF-IUS | Item |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-LM | Item | | SF-Link | List |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-ETag | Item | | SF-LM | Item |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-INM | List | | SF-Location | String |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-Link | List | | SF-Referer | String |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-Set-Cookie | Dictionary | | SF-Set-Cookie | Dictionary |
+---------------------+-----------------+ +---------------------+-----------------+
| SF-Cookie | List |
+---------------------+-----------------+
Table 5 Table 5: New Fields
Finally, add the indicated structured type for each existing registry Finally, add the indicated Structured Type for each existing registry
entry below: entry listed in Table 6.
+==========================================+=================+ +==========================================+=================+
| Field Name | Structured Type | | Field Name | Structured Type |
+==========================================+=================+ +==========================================+=================+
| Accept-CH | List | | Accept-CH | List |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| Cache-Status | List | | Cache-Status | List |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| CDN-Cache-Control | Dictionary | | CDN-Cache-Control | Dictionary |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| Cross-Origin-Opener-Policy | Item |
+------------------------------------------+-----------------+
| Cross-Origin-Opener-Policy-Report-Only | Item |
+------------------------------------------+-----------------+
| Cross-Origin-Embedder-Policy | Item | | Cross-Origin-Embedder-Policy | Item |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| Cross-Origin-Embedder-Policy-Report-Only | Item | | Cross-Origin-Embedder-Policy-Report-Only | Item |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| Cross-Origin-Opener-Policy | Item |
+------------------------------------------+-----------------+
| Cross-Origin-Opener-Policy-Report-Only | Item |
+------------------------------------------+-----------------+
| Origin-Agent-Cluster | Item | | Origin-Agent-Cluster | Item |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| Priority | Dictionary | | Priority | Dictionary |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
| Proxy-Status | List | | Proxy-Status | List |
+------------------------------------------+-----------------+ +------------------------------------------+-----------------+
Table 6 Table 6: Existing Fields
5. Security Considerations 5. Security Considerations
Section 2 identifies existing HTTP fields that can be parsed and Section 2 identifies existing HTTP fields that can be parsed and
serialised with the algorithms defined in [STRUCTURED-FIELDS]. serialised with the algorithms defined in [STRUCTURED-FIELDS].
Variances from other implementations might be exploitable, Variances from existing parser behavior might be exploitable,
particularly if they allow an attacker to target one implementation particularly if they allow an attacker to target one implementation
in a chain (e.g., an intermediary). However, given the considerable in a chain (e.g., an intermediary). However, given the considerable
variance in parsers already deployed, convergence towards a single variance in parsers already deployed, convergence towards a single
parsing algorithm is likely to have a net security benefit in the parsing algorithm is likely to have a net security benefit in the
longer term. longer term.
Section 3 defines alternative representations of existing fields. Section 3 defines alternative representations of existing fields.
Because downstream consumers might interpret the message differently Because downstream consumers might interpret the message differently
based upon whether they recognise the alternative representation, based upon whether they recognise the alternative representation,
implementations are prohibited from generating such fields unless implementations are prohibited from generating such fields unless
they have negotiated support for them with their peer. This they have negotiated support for them with their peer. This
specification does not define such a mechanism, but any such specification does not define such a mechanism, but any such
definition needs to consider the implications of doing so carefully. definition needs to consider the implications of doing so carefully.
6. Normative References 6. Normative References
[COOKIES] Chen, L., Englehardt, S., West, M., and J. Wilander,
"Cookies: HTTP State Management Mechanism", Work in
Progress, Internet-Draft, draft-ietf-httpbis-rfc6265bis-
10, 24 April 2022, <https://datatracker.ietf.org/doc/html/
draft-ietf-httpbis-rfc6265bis-10>.
[HTTP] Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP [HTTP] Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Semantics", Work in Progress, Internet-Draft, draft-ietf- Semantics", Work in Progress, Internet-Draft, draft-ietf-
httpbis-semantics-19, 12 September 2021, httpbis-semantics-19, 12 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis- <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
semantics-19>. semantics-19>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/rfc/rfc6265>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288, [RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017, DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/rfc/rfc8288>. <https://www.rfc-editor.org/rfc/rfc8288>.
[STRUCTURED-FIELDS] [STRUCTURED-FIELDS]
Nottingham, M. and P-H. Kamp, "Structured Field Values for Nottingham, M. and P-H. Kamp, "Structured Field Values for
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