Applications Area WG (APPSAWG) L. Hunt, Ed.
Internet-Draft Opera Software, ASA.
Intended Status: Standards Track M. Yevstifeyev, Ed.
Expires: April 19, 2012 October 17, 2011
The 'about' URI Scheme
draft-ietf-appsawg-about-uri-scheme-00
Abstract
This document defines the 'about' URI scheme, that is widely used by
Web browsers and some other applications to designate access to their
internal resources, such as settings, application information, hidden
built-in functionality, and so on.
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Copyright (c) 2011 IETF Trust and the persons identified as the
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the Trust Legal Provisions and are provided without warranty as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. URI Scheme Specification . . . . . . . . . . . . . . . . . . . 3
2.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . . 3
2.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . . 3
2.2.1. Special-Purpose 'about' URIs . . . . . . . . . . . . . 3
2.2.2. Unrecognized 'about' URIs . . . . . . . . . . . . . . . 4
2.3. Encoding Considerations . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
4.1. URI Scheme Registration . . . . . . . . . . . . . . . . . . 5
4.2. A Registry for SPTs . . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
This document specifies the 'about' Uniform Resource Identifier (URI)
scheme, that is currently widely used by Web browsers and some other
applications to designate access to their internal resources, such as
settings, application information, so called "Easter eggs" (i.e.
hidden feature or joke in an application), and so on.
The concept of 'about' URIs has been formed at the times when the
applications did not have the "friendly" user interface, in order to
provide an access to the aforementioned resources via typing the URIs
in the address bar. Even though the user interface of current
Internet-targeted software effectively rescinds the issue, and
'about' URIs can be thought to be a rudimentary phenomenon, they are
still supported by a variety of Web browsers and are not going to
cease to exist.
As use of 'about' URIs has been quiet long-lasting, and the URIs have
been used without any proper registration and absent any proper
specification, the necessity for the the latter two actions arises.
The purpose of this document is to provide a stable specification for
'about' URI scheme and correspondingly register it in the IANA
registry. Along, several provisions for handling the 'about' URIs
are set.
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Please consult RFC 3986 [RFC3986] for definition of generic URIs
syntax and RFC 4395 [RFC4395] for description of registration process
for new URI schemes.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. URI Scheme Specification
2.1. URI Scheme Syntax
The 'about' URI MUST syntactically conform to the <about-uri> rule
below, expressed using Augmented Backus-Naur Form (ABNF) [RFC5234]:
about-uri = "about:" about-token [ about-query ]
about-token = segment
about-query = "?" query
segment = <as specified in RFC 3986, Appendix A>
query = <as specified in RFC 3986, Appendix A>
In terms of RFC 3986, <about-token> part corresponds to <hier-part>,
and <about-query> to the query component of URI.
2.2. URI Scheme Semantics
Generally speaking, the resource a particular 'about' URI resolves to
is denoted by <about-token> part of the URI, and <about-query>
specifies additional information concerning its handling and/or the
information that should be returned in the resource a URI is resolved
to.
However, it is impossible to specify binding between all the possible
tokens and the semantics of 'about' URIs that would contain such
tokens. Therefore any application MAY resolve an 'about' URI to any
desired resource, and MAY redirect such URIs. Several exceptions are
defined, though; they are named "special-purpose 'about' URIs" and
MUST be handled in strict accordance with provisions set in Section
2.2.1.
2.2.1. Special-Purpose 'about' URIs
A small, though expandable, range of <about-token>s are reserved for
use in special-purpose 'about' URIs, abbreviated "SPU" (special-
purpose URI). Such tokens are named "special-purpose 'about' URI
tokens", and abbreviated "SPT" (special-purpose token).
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An SPU is an 'about' URI containing one of the registered SPTs as the
<about-token> part. An SPU MUST be handled in strict accordance with
the rules defined for SPT contained therein. The SPT specification
MAY define additional provisions on handling of <about-query> part in
the corresponding SPU; by default, it MUST be ignored for the purpose
of handling SPU.
SPU MAY be defined to be unresolvable. This means that an
application MUST NOT resolve it in some particular resource. Such
SPUs may be used as placeholders, or in some other way.
One pre-defined SPT is specified: the "blank" SPT. The URI
<about:blank> MUST resolve to a blank page; this page need not
necessarily contain no data, it should rather represent blank page.
There is no additional handling of query component in <about:blank>
URIs: both <about:blank> and <about:blank?foo> shall resolve into the
blank page.
Additional SPTs may be defined via adding the entry in the registry
created by this document. Please note that defining an SPT should
only be used as a last resort approach, when a strict limitation on
handling 'about' URI with such SPT is necessary.
2.2.2. Unrecognized 'about' URIs
Naturally, an application will support only a particular range of
'about' URIs; also, some applications will support 'about' URIs that
are not supported by an other one. This document specifies the rules
for handling unrecognized 'about' URIs.
An unrecognized 'about' URIs as a URI that may not be recognized by
an application. (Correspondingly, such categorization is per-
application, not per-fact.) An unrecognized 'about' URI SHOULD be
handled as the <about:blank> URI, although other behavior is
possible.
2.3. Encoding Considerations
'about' URIs are subject to encoding rules defined in RFC 3986
[RFC3986]. 'about' IRIs [RFC3987] are not permitted.
3. Security Considerations
Generic security considerations for URIs are discussed in Section 7
of RFC 3986 [RFC3986]. However, many of those provisions hardly
apply to 'about' URI scheme, as they are mainly scoped to schemes
used in the Internet, not internally.
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'about' URIs may sometimes refer to a sensitive information, such as
user passwords stored in a cache, or parameter that, if changed, may
affect user's data. The application should therefore ensure that
user's data is in the safety, and no threats are imposed by 'about'
URIs.
4. IANA Considerations
4.1. URI Scheme Registration
IANA is asked to update the register the 'about' URI scheme using the
following template, per [RFC4395]:
URI scheme name: about
Status: Permanent
URI scheme syntax: see Section 2.1 of RFC xxxx
URI scheme semantics: see Section 2.2 of RFC xxxx
URI scheme encoding considerations: see Section 2.3 of RFC xxxx
Applications/protocols that use the scheme: 'about' URIs are
predominantly used by Web browsers, although they may be used by
other applications.
Security considerations: see Section 3 of RFC xxxx
Contact: IESG <iesg@ietf.org>
Author/Change controller: IETF <ietf@ietf.org>
References: see Section 5 of RFC xxxx
[RFC Editor: Please replace xxxx with assigned RFC number]
4.2. A Registry for SPTs
IANA is asked to set up a new registry entitled "'about' URIs SPTs"
following the guidelines below.
The registry entries consist of 3 fields: SPT, Description and
Reference. The SPT field MUST conform to <about-token> production
defined in Section 2.1. The initial registry contents consist of one
entry:
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+----------+----------------------------------------+-----------+
| SPT | Description | Reference |
+----------+----------------------------------------+-----------+
| blank | Used in 'about' URIs referring to a | RFC xxxx |
| | blank page. | |
+----------+----------------------------------------+-----------+
The registration policy for new entries is "Specification Required",
as defined in RFC 5226 [RFC5226]. Additionally, the following
template MUST be provided by the registrant:
o SPT: The desired special-purpose token to be used in 'about' URIs.
o Intended usage: A short description of how 'about' URIs with the
registered token must be handled; especially, what they must be
resolved to, if resolvable.
o Resolvable: "Yes" if resolvable (i.e. can be resolved to a
particular resource) or "No" if unresolvable (see Section 2.2.1).
o Handling query component: It should be mentioned whether there are
some provisions on handling query components in the 'about' URIs
with the registered token.
o Contact/Change controller: An individual or an organization which
(1) should be contacted for more details, and (2) is authorized to
change the registration.
o Published specifications: A reference to the published
specification for the registered token.
The following is a template for "blank" SPT:
o SPT: blank
o Intended usage: The <about:blank> URI must resolve to a blank
page.
o Resolvable: Yes.
o Handling query component: No special provisions.
o Contact/Change controller: IESG <iesg@ietf.org> (on behalf of
IETF).
o Published specifications: This document.
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234, January
2008.
5.2. Informative References
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35,
RFC 4395, February 2006.
This document has been formed from the draft initially authored by,
additionally to Lachlan Hunt, the editor of the current one, Joseph
Holsten. Additionally, the contributions of <TBD> are gratefully
acknowledged.
Authors' Addresses
Lachlan Hunt (editor)
Opera Software, ASA.
EMail: lachlan.hunt@lachy.id.au
URI: http://lachy.id.au/
Mykyta Yevstifeyev (editor)
8 Kuzovkov St., Apt. 25
Kotovsk
Ukraine
EMail: evnikita2@gmail.com
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