< draft-nottingham-rfc5785bis-00.txt   draft-nottingham-rfc5785bis-01.txt >
Network Working Group M. Nottingham Network Working Group M. Nottingham
Internet-Draft November 13, 2017 Internet-Draft November 13, 2017
Obsoletes: 5785 (if approved) Obsoletes: 5785 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: May 17, 2018 Expires: May 17, 2018
Defining Well-Known Uniform Resource Identifiers (URIs) Defining Well-Known Uniform Resource Identifiers (URIs)
draft-nottingham-rfc5785bis-00 draft-nottingham-rfc5785bis-01
Abstract Abstract
This memo defines a path prefix for "well-known locations", "/.well- This memo defines a path prefix for "well-known locations", "/.well-
known/", in selected Uniform Resource Identifier (URI) schemes. known/", in selected Uniform Resource Identifier (URI) schemes.
Note to Readers Note to Readers
_RFC EDITOR: please remove this section before publication_ _RFC EDITOR: please remove this section before publication_
This draft is a proposed revision of RFC5875. Version -00 is a copy This draft is a proposed revision of RFC5875.
of the original RFC.
The issues list for this draft can be found at The issues list for this draft can be found at
https://github.com/mnot/I-D/labels/5785bis . https://github.com/mnot/I-D/labels/5785bis .
The most recent (often, unpublished) draft is at The most recent (often, unpublished) draft is at
https://mnot.github.io/I-D/5785bis/ . https://mnot.github.io/I-D/5785bis/ .
Recent changes are listed at https://github.com/mnot/I-D/commits/gh- Recent changes are listed at https://github.com/mnot/I-D/commits/gh-
pages/5785bis . pages/5785bis .
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Appropriate Use of Well-Known URIs . . . . . . . . . . . 3 1.1. Appropriate Use of Well-Known URIs . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3
3. Well-Known URIs . . . . . . . . . . . . . . . . . . . . . . . 3 3. Well-Known URIs . . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5.1. The Well-Known URI Registry . . . . . . . . . . . . . . . 4 5.1. The Well-Known URI Registry . . . . . . . . . . . . . . . 5
5.1.1. Registration Template . . . . . . . . . . . . . . . . 5 5.1.1. Registration Template . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5 6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6 Appendix A. Frequently Asked Questions . . . . . . . . . . . . . 6
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 6 Appendix B. Changes from RFC5785 . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
It is increasingly common for Web-based protocols to require the Some applications on the Web require the discovery of policy or other
discovery of policy or other information about a host ("site-wide information about an origin [RFC6454] (sometimes called "site-wide
metadata") before making a request. For example, the Robots metadata") before making a request. For example, the Robots
Exclusion Protocol (http://www.robotstxt.org/ ) specifies a way for Exclusion Protocol (http://www.robotstxt.org/ ) specifies a way for
automated processes to obtain permission to access resources; automated processes to obtain permission to access resources;
likewise, the Platform for Privacy Preferences [W3C.REC-P3P-20020416] likewise, the Platform for Privacy Preferences [W3C.REC-P3P-20020416]
tells user-agents how to discover privacy policy beforehand. tells user-agents how to discover privacy policy before interacting
with a site.
While there are several ways to access per-resource metadata (e.g., While there are several ways to access per-resource metadata (e.g.,
HTTP headers, WebDAV's PROPFIND [RFC4918]), the perceived overhead HTTP headers, WebDAV's PROPFIND [RFC4918]), the perceived overhead
(either in terms of client-perceived latency and/or deployment (either in terms of client-perceived latency and/or deployment
difficulties) associated with them often precludes their use in these difficulties) associated with them often precludes their use in these
scenarios. scenarios.
When this happens, it is common to designate a "well-known location" When this happens, one solution is designating a "well-known
for such data, so that it can be easily located. However, this location" for data or services related to the origin, so that it can
approach has the drawback of risking collisions, both with other such be easily located. However, this approach has the drawback of
designated "well-known locations" and with pre-existing resources. risking collisions, both with other such designated "well-known
locations" and with pre-existing resources.
To address this, this memo defines a path prefix in HTTP(S) URIs for To address this, this memo defines a path prefix in HTTP(S) URIs for
these "well-known locations", "/.well-known/". Future specifications these "well-known locations", "/.well-known/". Future specifications
that need to define a resource for such site-wide metadata can that need to define a resource for such site-wide metadata can
register their use to avoid collisions and minimise impingement upon register their use to avoid collisions and minimise impingement upon
sites' URI space. sites' URI space.
Well-known URIs can also be used with other URI schemes, but only
when those schemes' definitions explicitly allow it.
1.1. Appropriate Use of Well-Known URIs 1.1. Appropriate Use of Well-Known URIs
There are a number of possible ways that applications could use Well- There are a number of possible ways that applications could use well-
known URIs. However, in keeping with the Architecture of the World- known URIs. However, in keeping with the Architecture of the World-
Wide Web [W3C.REC-webarch-20041215], well-known URIs are not intended Wide Web [W3C.REC-webarch-20041215], well-known URIs are not intended
for general information retrieval or establishment of large URI for general information retrieval or establishment of large URI
namespaces on the Web. Rather, they are designed to facilitate namespaces on the Web. Rather, they are designed to facilitate
discovery of information on a site when it isn't practical to use discovery of information on a site when it isn't practical to use
other mechanisms; for example, when discovering policy that needs to other mechanisms; for example, when discovering policy that needs to
be evaluated before a resource is accessed, or when using multiple be evaluated before a resource is accessed, or when using multiple
round-trips is judged detrimental to performance. round-trips is judged detrimental to performance.
As such, the well-known URI space was created with the expectation As such, the well-known URI space was created with the expectation
that it will be used to make site-wide policy information and other that it will be used to make policy information and other metadata
metadata available directly (if sufficiently concise), or provide about the origin available directly (if sufficiently concise), or
references to other URIs that provide such metadata. provide references to other URIs that provide it.
Therefore, it is inappropriate to use well-known URIs as a means of
identifying or locating a new protocol built on top of HTTP, since
they are intended for metadata about their origin.
In particular, locating information using a hostname instead of a URI
is, on its own, insufficient reason to register a well-known URI.
2. Notational Conventions 2. 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. Well-Known URIs 3. Well-Known URIs
A well-known URI is a URI [RFC3986] whose path component begins with A well-known URI is a URI [RFC3986] whose path component begins with
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known URIs. known URIs.
Applications that wish to mint new well-known URIs MUST register Applications that wish to mint new well-known URIs MUST register
them, following the procedures in Section 5.1. them, following the procedures in Section 5.1.
For example, if an application registers the name 'example', the For example, if an application registers the name 'example', the
corresponding well-known URI on 'http://www.example.com/' would be corresponding well-known URI on 'http://www.example.com/' would be
'http://www.example.com/.well-known/example'. 'http://www.example.com/.well-known/example'.
Registered names MUST conform to the segment-nz production in Registered names MUST conform to the segment-nz production in
[RFC3986]. [RFC3986]. This means they cannot contain the "/" character.
Note that this specification defines neither how to determine the Note that this specification defines neither how to determine the
authority to use for a particular context, nor the scope of the authority to use for a particular context, nor the scope of the
metadata discovered by dereferencing the well-known URI; both should metadata discovered by dereferencing the well-known URI; both should
be defined by the application itself. be defined by the application itself.
Typically, a registration will reference a specification that defines Typically, a registration will reference a specification that defines
the format and associated media type to be obtained by dereferencing the format and associated media type to be obtained by dereferencing
the well-known URI. the well-known URI.
It MAY also contain additional information, such as the syntax of It MAY also contain additional information, such as the syntax of
additional path components, query strings and/or fragment identifiers additional path components, query strings and/or fragment identifiers
to be appended to the well-known URI, or protocol-specific details to be appended to the well-known URI, or protocol-specific details
(e.g., HTTP [RFC2616] method handling). (e.g., HTTP [RFC7231] method handling).
Note that this specification does not define a format or media-type Note that this specification does not define a format or media-type
for the resource located at "/.well-known/" and clients should not for the resource located at "/.well-known/" and clients should not
expect a resource to exist at that location. expect a resource to exist at that location.
4. Security Considerations 4. Security Considerations
This memo does not specify the scope of applicability of metadata or This memo does not specify the scope of applicability of metadata or
policy obtained from a well-known URI, and does not specify how to policy obtained from a well-known URI, and does not specify how to
discover a well-known URI for a particular application. Individual discover a well-known URI for a particular application. Individual
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issues, including (but not limited to) exposure of sensitive data, issues, including (but not limited to) exposure of sensitive data,
denial-of-service attacks (in addition to normal load issues), server denial-of-service attacks (in addition to normal load issues), server
and client authentication, vulnerability to DNS rebinding attacks, and client authentication, vulnerability to DNS rebinding attacks,
and attacks where limited access to a server grants the ability to and attacks where limited access to a server grants the ability to
affect how well-known URIs are served. affect how well-known URIs are served.
5. IANA Considerations 5. IANA Considerations
5.1. The Well-Known URI Registry 5.1. The Well-Known URI Registry
This document establishes the well-known URI registry. This document specifies procedures for the well-known URI registry,
first defined in [RFC5785].
Well-known URIs are registered on the advice of one or more Well-known URIs are registered on the advice of one or more experts
Designated Experts (appointed by the IESG or their delegate), with a (appointed by the IESG or their delegate), with a Specification
Specification Required (using terminology from [RFC5226]). However, Required (using terminology from [RFC8126]). However, to allow for
to allow for the allocation of values prior to publication, the the allocation of values prior to publication, the expert(s) may
Designated Expert(s) may approve registration once they are satisfied approve registration once they are satisfied that such a
that such a specification will be published. specification will be published.
Registration requests should be sent to the wellknown-uri- Registration requests can be sent to the wellknown-uri-
review@ietf.org mailing list for review and comment, with an review@ietf.org mailing list for review and comment, with an
appropriate subject (e.g., "Request for well-known URI: example"). appropriate subject (e.g., "Request for well-known URI: example").
Before a period of 14 days has passed, the Designated Expert(s) will
either approve or deny the registration request, communicating this
decision both to the review list and to IANA. Denials should include
an explanation and, if applicable, suggestions as to how to make the
request successful. Registration requests that are undetermined for
a period longer than 21 days can be brought to the IESG's attention
(using the iesg@iesg.org mailing list) for resolution.
5.1.1. Registration Template 5.1.1. Registration Template
URI suffix: The name requested for the well-known URI, relative to URI suffix: The name requested for the well-known URI, relative to
"/.well-known/"; e.g., "example". "/.well-known/"; e.g., "example".
Change controller: For Standards-Track RFCs, state "IETF". For Change controller: For Standards-Track RFCs, state "IETF". For
others, give the name of the responsible party. Other details others, give the name of the responsible party. Other details
(e.g., postal address, e-mail address, home page URI) may also be (e.g., postal address, e-mail address, home page URI) may also be
included. included.
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[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, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, <https://www.rfc-editor.org/info/ RFC2119, March 1997, <https://www.rfc-editor.org/info/
rfc2119>. rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, DOI 10.17487/RFC3986, January 2005, 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, DOI
IANA Considerations Section in RFCs", RFC 5226, DOI 10.17487/RFC6454, December 2011, <https://www.rfc-
10.17487/RFC5226, May 2008, <https://www.rfc- editor.org/info/rfc6454>.
editor.org/info/rfc5226>.
6.2. Informative References [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 6.2. Informative References
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, DOI 10.17487/
RFC2616, June 1999, <https://www.rfc-editor.org/info/
rfc2616>.
[RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed [RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, DOI Authoring and Versioning (WebDAV)", RFC 4918, DOI
10.17487/RFC4918, June 2007, <https://www.rfc- 10.17487/RFC4918, June 2007, <https://www.rfc-
editor.org/info/rfc4918>. editor.org/info/rfc4918>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785, DOI
10.17487/RFC5785, April 2010, <https://www.rfc-
editor.org/info/rfc5785>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI
10.17487/RFC7231, June 2014, <https://www.rfc-
editor.org/info/rfc7231>.
[W3C.REC-P3P-20020416] [W3C.REC-P3P-20020416]
Marchiori, M., "The Platform for Privacy Preferences 1.0 Marchiori, M., "The Platform for Privacy Preferences 1.0
(P3P1.0) Specification", World Wide Web Consortium (P3P1.0) Specification", World Wide Web Consortium
Recommendation REC-P3P-20020416, April 2002, Recommendation REC-P3P-20020416, April 2002,
<http://www.w3.org/TR/2002/REC-P3P-20020416>. <http://www.w3.org/TR/2002/REC-P3P-20020416>.
Appendix A. Acknowledgements Appendix A. Frequently Asked Questions
We would like to acknowledge the contributions of everyone who
provided feedback and use cases for this document; in particular,
Phil Archer, Dirk Balfanz, Adam Barth, Tim Bray, Brian Eaton, Brad
Fitzpatrick, Joe Gregorio, Paul Hoffman, Barry Leiba, Ashok Malhotra,
Breno de Medeiros, John Panzer, and Drummond Reed. However, they are
not responsible for errors and omissions.
Appendix B. Frequently Asked Questions
1. Aren't well-known locations bad for the Web? 1. Aren't well-known locations bad for the Web?
They are, but for various reasons - both technical and social - They are, but for various reasons - both technical and social -
they are commonly used and their use is increasing. This memo they are sometimes necessary. This memo defines a "sandbox" for
defines a "sandbox" for them, to reduce the risks of collision them, to reduce the risks of collision and to minimise the impact
and to minimise the impact upon pre-existing URIs on sites. upon pre-existing URIs on sites.
2. Why /.well-known? 2. Why /.well-known?
It's short, descriptive, and according to search indices, not It's short, descriptive, and according to search indices, not
widely used. widely used.
3. What impact does this have on existing mechanisms, such as P3P 3. What impact does this have on existing mechanisms, such as P3P
and robots.txt? and robots.txt?
None, until they choose to use this mechanism. None, until they choose to use this mechanism.
4. Why aren't per-directory well-known locations defined? 4. Why aren't per-directory well-known locations defined?
Allowing every URI path segment to have a well-known location Allowing every URI path segment to have a well-known location
(e.g., "/images/.well-known/") would increase the risks of (e.g., "/images/.well-known/") would increase the risks of
colliding with a pre-existing URI on a site, and generally these colliding with a pre-existing URI on a site, and generally these
solutions are found not to scale well, because they're too solutions are found not to scale well, because they're too
"chatty". "chatty".
Appendix B. Changes from RFC5785
o Discuss inappropriate uses more fully
o Adjusted IANA instructions
o Updated references
o Various other clarifications
Author's Address Author's Address
Mark Nottingham Mark Nottingham
Email: mnot@mnot.net Email: mnot@mnot.net
URI: https://www.mnot.net/ URI: https://www.mnot.net/
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