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Internet Engineering Task Force (IETF)                 S. Moonesamy, Ed.Request for Comments: 6694                                   August 2012Category: InformationalISSN: 2070-1721The "about" URI SchemeAbstract   This document describes the "about" URI scheme, which 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.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6694.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Moonesamy                     Informational                     [Page 1]

RFC 6694                 The "about" URI Scheme              August 2012Table of Contents1. Introduction ....................................................22. URI Scheme Specification ........................................22.1. URI Scheme Syntax ..........................................22.2. URI Scheme Semantics .......................................32.2.1. Well-Known "about" URIs .............................32.3. Encoding Considerations ....................................33. "about:blank" ...................................................34. Security Considerations .........................................35. IANA Considerations .............................................45.1. URI Scheme Registration ....................................45.2. A Registry for Well-Known Tokens ...........................55.2.1. Registration Procedure ..............................56. References ......................................................66.1. Normative References .......................................66.2. Informative References .....................................6Appendix A. Acknowledgments ........................................71.  Introduction   This document describes the "about" Uniform Resource Identifier (URI)   scheme.  The "about" URI scheme is currently widely used by Web   browsers to designate access to their internal resources, such as   settings, application information, and so-called "Easter eggs" (i.e.,   a hidden feature or joke in an application).2.  URI Scheme Specification2.1.  URI Scheme Syntax   The "about" URI syntactically conforms to the <about-uri> rule below,   expressed using the Augmented Backus-Naur Form (ABNF) [RFC5234]:     about-uri = "about:" about-token [ about-query ] [ about-fragment ]     about-token = *pchar     about-query = "?" query     about-fragment = "#" fragment     pchar     = <as specified inRFC 3986, Appendix A>     query     = <as specified inRFC 3986, Appendix A>     fragment  = <as specified inRFC 3986, Appendix A>Moonesamy                     Informational                     [Page 2]

RFC 6694                 The "about" URI Scheme              August 20122.2.  URI Scheme Semantics   The resource that is referenced by a particular "about" URI is   denoted by the <about-token> part of the URI.  It is not a   hierarchical element for a naming authority.  The <about-query> part   specifies additional information about its handling and/or the   information that should be returned by the resource referenced by   the URI.   It is impossible to specify a binding between all the possible tokens   and the semantics of "about" URIs that would contain such tokens.   Therefore, the resource referenced by the URI is generally considered   to be specific to a Web browser implementation.2.2.1.  Well-Known "about" URIs   Some <about-token>s have been reserved, as the behavior of the   resource that is referenced is well-known (well-known tokens).   A well-known "about" URI is a URI that has a well-known token as its   <about-token> part.  It is recommended that such URIs be handled in   accordance with the specification referenced in the "about" URI   Tokens registry (seeSection 5.2).   Well-known "about" URIs are intended to be registered when there is a   need to codify the behavior of a particular <about-token>.2.3.  Encoding Considerations   "about" URIs are subject to encoding rules as defined inRFC 3986   [RFC3986].3.  "about:blank"   This document defines one well-known token: "blank".  The   "about:blank" URI refers to a resource represented in the browser by   a blank page.4.  Security Considerations   Security considerations for URIs are discussed inSection 7 of   RFC 3986 [RFC3986].  However, most of those provisions do not apply   to the "about" URI scheme, as they are mainly scoped to schemes used   in the Internet.Moonesamy                     Informational                     [Page 3]

RFC 6694                 The "about" URI Scheme              August 2012   "about" URIs can sometimes refer to sensitive information, such as   user passwords stored in a cache, or parameters that, if changed,   could affect a user's data.  The application therefore needs to   ensure that the user's data is secured and no threats are imposed by   "about" URIs.5.  IANA Considerations5.1.  URI Scheme Registration   The "about" URI scheme has been registered in the "Permanent URI   Schemes" registry.  The information below is provided according to   the guidelines fromRFC 4395 [RFC4395]:      URI scheme name: about      Status: Permanent      URI scheme syntax: SeeSection 2.1 of RFC 6694.      URI scheme semantics: SeeSection 2.2 of RFC 6694.      URI scheme encoding considerations: SeeSection 2.3 of RFC 6694.      Applications that use the scheme: "about" URIs are predominantly         used by Web browsers.      Security considerations: SeeSection 4 of RFC 6694.      Contact: IETF Applications Area Directors         <app-ads@tools.ietf.org>      Author/Change controller: IESG <iesg@ietf.org> (on behalf of the         IETF)      References: SeeSection 6 of RFC 6694.Moonesamy                     Informational                     [Page 4]

RFC 6694                 The "about" URI Scheme              August 20125.2.  A Registry for Well-Known Tokens   This document creates the '"about" URI Tokens' registry.   The registry entries consist of three fields: Token, Description, and   Reference.  The Token field has to conform to <about-token>   production as defined inSection 2.1.  The initial assignment is as   follows:   +--------------+------------------------------------+-------------+   | Token        | Description                        | Reference   |   +--------------+------------------------------------+-------------+   | blank        | The about:blank URI references a   |RFC 6694    |   |              | blank page.                        |             |   +--------------+------------------------------------+-------------+5.2.1.  Registration Procedure   The registration policy for this registry is "First Come First   Served", as described inRFC 5226 [RFC5226].  The registrant of the   token should provide the information mentioned in the following   registration template:   o  Registered token:  The desired well-known token to be used in      "about" URIs.   o  Intended usage:  A short description of how "about" URIs with the      registered token are handled, including information about the      referenced resource.   o  Contact/change controller:  Person (including contact information)      authorized to change this registration.   o  Specification:  A stable reference to a document that specifies      the registered "about" URI.  The question of interoperability does      not arise.  The key motivation is to have a reference to a      specification documenting well-known behavior of the "about" URI      in Web browsers.  As a rule of thumb, if the behavior is common to      two or more Web browser implementations, it can be considered      well-known.  An existing assignment may be duplicated if the      registered token is used in more than one Web browser      implementation.Moonesamy                     Informational                     [Page 5]

RFC 6694                 The "about" URI Scheme              August 2012   The following is a template for the "blank" token:   o  Registered token:  blank   o  Intended usage:  The about:blank URI references a blank page.   o  Contact/change controller:  IESG <iesg@ietf.org> (on behalf of the      IETF).   o  Specification:RFC 66946.  References6.1.  Normative References   [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 2008.6.2.  Informative References   [RFC4395]   Hansen, T., Hardie, T., and L. Masinter, "Guidelines and               Registration Procedures for New URI Schemes",BCP 35,RFC 4395, February 2006.Moonesamy                     Informational                     [Page 6]

RFC 6694                 The "about" URI Scheme              August 2012Appendix A.  Acknowledgments   This document was formed from a previous draft document initially   authored by Lachlan Hunt and Joseph Holsten.  Additionally, the   contributions of Frank Ellermann and Alexey Melnikov are gratefully   acknowledged.  Barry Leiba and Murray Kucherawy deserve special   credit for providing a great amount of text that was used in this   document.   Lachlan Hunt and Mykyta Yevstifeyev edited previous versions of this   document.  Tim Bray and John Klensin provided suggestions about how   to improve the document.Author's Address   S. Moonesamy (editor)   76 Ylang Ylang Avenue   Quatre Bornes   Mauritius   EMail: sm+ietf@elandsys.comMoonesamy                     Informational                     [Page 7]