< draft-nottingham-rfc5785bis-09.txt   draft-nottingham-rfc5785bis-10.txt >
Network Working Group M. Nottingham Network Working Group M. Nottingham
Internet-Draft February 26, 2019 Internet-Draft March 26, 2019
Obsoletes: 5785, 8307 (if approved) Obsoletes: 5785, 8307 (if approved)
Updates: 7230, 6455 (if approved) Updates: 7230, 6455 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: August 30, 2019 Expires: September 27, 2019
Well-Known Uniform Resource Identifiers (URIs) Well-Known Uniform Resource Identifiers (URIs)
draft-nottingham-rfc5785bis-09 draft-nottingham-rfc5785bis-10
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.
In doing so, it obsoletes RFC 5785 and RFC 8307, and updates the URI In doing so, it obsoletes RFC 5785 and RFC 8307, and updates the URI
schemes defined in RFC 7230 and RFC 6455 to reserve that space. schemes defined in RFC 7230 and RFC 6455 to reserve that space.
Note to Readers Note to Readers
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on August 30, 2019. This Internet-Draft will expire on September 27, 2019.
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
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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
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3
3. Well-Known URIs . . . . . . . . . . . . . . . . . . . . . . . 3 3. Well-Known URIs . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Registering Well-Known URIs . . . . . . . . . . . . . . . 5 3.1. Registering Well-Known URIs . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4.1. Interaction with Web Browsing . . . . . . . . . . . . . . 6 4.1. Protecting Well-Known Resources . . . . . . . . . . . . . 6
4.2. Scoping Applications . . . . . . . . . . . . . . . . . . 7 4.2. Interaction with Web Browsing . . . . . . . . . . . . . . 6
4.3. Hidden Capabilities . . . . . . . . . . . . . . . . . . . 8 4.3. Scoping Applications . . . . . . . . . . . . . . . . . . 7
4.4. Hidden Capabilities . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. The Well-Known URI Registry . . . . . . . . . . . . . . . 8 5.1. The Well-Known URI Registry . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . 8 6.1. Normative References . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . 10
6.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix A. Frequently Asked Questions . . . . . . . . . . . . . 11 Appendix A. Frequently Asked Questions . . . . . . . . . . . . . 11
Appendix B. Changes from RFC5785 . . . . . . . . . . . . . . . . 11 Appendix B. Changes from RFC5785 . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
Some applications on the Web require the discovery of information Some applications on the Web require the discovery of information
about an origin [RFC6454] (sometimes called "site-wide metadata") about an origin [RFC6454] (sometimes called "site-wide metadata")
before making a request. For example, the Robots Exclusion Protocol before making a request. For example, the Robots Exclusion Protocol
(http://www.robotstxt.org/ [5]) specifies a way for automated (http://www.robotstxt.org/ [5]) specifies a way for automated
processes to obtain permission to access resources; likewise, the processes to obtain permission to access resources; likewise, the
Platform for Privacy Preferences [P3P] tells user-agents how to Platform for Privacy Preferences [P3P] tells user-agents how to
discover privacy policy before interacting with an origin server. discover privacy policy before interacting with an origin server.
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way to locate one or more resources on a given host. way to locate one or more resources on a given host.
When this happens, one solution is to designate a "well-known When this happens, one solution is to designate a "well-known
location" for data or services related to the origin overall, so that location" for data or services related to the origin overall, so that
it can be easily located. However, this approach has the drawback of it can be easily located. However, this approach has the drawback of
risking collisions, both with other such designated "well-known risking collisions, both with other such designated "well-known
locations" and with resources that the origin has created (or wishes locations" and with resources that the origin has created (or wishes
to create). Furthermore, defining well-known locations usurp's the to create). Furthermore, defining well-known locations usurp's the
origin's control over its own URI space [RFC7320]. origin's control over its own URI space [RFC7320].
To address these uses, this memo defines a path prefix in HTTP(S) To address these uses, this memo reserves a path prefix in HTTP,
URIs for these "well-known locations", "/.well-known/". Future HTTPS, WS and WSS URIs for these "well-known locations", "/.well-
specifications that need to define a resource for such metadata can known/". Future specifications that need to define a resource for
register their use to avoid collisions and minimise impingement upon such metadata can register their use to avoid collisions and minimise
origins' URI space. impingement upon origins' URI space.
Well-known URIs can also be used with other URI schemes, but only Well-known URIs can also be used with other URI schemes, but only
when those schemes' definitions explicitly allow it. when those schemes' definitions explicitly allow it.
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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
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Values defined by standards-track RFCs and other open standards (in Values defined by standards-track RFCs and other open standards (in
the sense of [RFC2026], Section 7.1.1) have a status of "permanent". the sense of [RFC2026], Section 7.1.1) have a status of "permanent".
Other values can also be registered as permanent, if the Experts find Other values can also be registered as permanent, if the Experts find
that they are in use, in consultation with the community. Other that they are in use, in consultation with the community. Other
values should be registered as "provisional". values should be registered as "provisional".
Provisional entries can be removed by the Experts if - in Provisional entries can be removed by the Experts if - in
consultation with the community - the Experts find that they are not consultation with the community - the Experts find that they are not
in use. The Experts can change a provisional entry's status to in use. The Experts can change a provisional entry's status to
permanent at any time. permanent; in doing so, the Experts should consider how widely used a
value is, and consult the community beforehand.
Note that well-known URIs can be registered by third parties Note that "consult with the community" above refers to those
(including the expert(s)), if the expert(s) determines that an responsible for the URI scheme(s) in question. Generally, this would
unregistered well-known URI is widely deployed and not likely to be take place on the mailing list(s) of the appropriate Working Group(s)
registered in a timely manner otherwise. Such registrations still (possibly historical), or on art@ietf.org if no such list exists.
are subject to the requirements defined, including the need to
reference a specification. Well-known URIs can be registered by third parties (including the
expert(s)), if the expert(s) determine that an unregistered well-
known URI is widely deployed and not likely to be registered in a
timely manner otherwise. Such registrations still are subject to the
requirements defined, including the need to reference a
specification.
4. Security Considerations 4. Security Considerations
Applications minting new well-known URIs, as well as administrators Applications minting new well-known URIs, as well as administrators
deploying them, will need to consider several security-related deploying them, will need to consider several security-related
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.
4.1. Interaction with Web Browsing [RFC3552] contains some examples of potential security considerations
that may be relevant to application protocols and administrators
deploying them.
4.1. Protecting Well-Known Resources
Because well-known locations effectively represent the entire origin,
server operators should appropriately control the ability to write to
them. This is especially true when more than one entity is co-
located on the same origin. Even for origins that are controlled by
and represent a single entity, due care should be taken to assure
that write access to well-known locations is not granted unwittingly,
either externally through server configuration, or locally through
implementation permissions (e.g., on a filesystem).
4.2. Interaction with Web Browsing
Applications using well-known URIs for "http" or "https" URLs need to Applications using well-known URIs for "http" or "https" URLs need to
be aware that well-known resources will be accessible to Web be aware that well-known resources will be accessible to Web
browsers, and therefore are able to be manipulated by content browsers, and therefore are able to be manipulated by content
obtained from other parts of that origin. If an attacker is able to obtained from other parts of that origin. If an attacker is able to
inject content (e.g., through a Cross-Site Scripting vulnerability), inject content (e.g., through a Cross-Site Scripting vulnerability),
they will be able to make potentially arbitrary requests to the well- they will be able to make potentially arbitrary requests to the well-
known resource. known resource.
HTTP and HTTPS also use origins as a security boundary for many other HTTP and HTTPS also use origins as a security boundary for many other
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o Using Referrer-Policy [REFERRER-POLICY] to prevent sensitive data o Using Referrer-Policy [REFERRER-POLICY] to prevent sensitive data
in URLs from being leaked in the Referer request header field in URLs from being leaked in the Referer request header field
o Avoiding use of compression on any sensitive information (e.g., o Avoiding use of compression on any sensitive information (e.g.,
authentication tokens, passwords), as the scripting environment authentication tokens, passwords), as the scripting environment
offered by Web browsers allows an attacker to repeatedly probe the offered by Web browsers allows an attacker to repeatedly probe the
compression space; if the attacker has access to the path of the compression space; if the attacker has access to the path of the
communication, they can use this capability to recover that communication, they can use this capability to recover that
information. information.
4.2. Scoping Applications 4.3. Scoping Applications
This memo does not specify the scope of applicability for the This memo does not specify the scope of applicability for the
information obtained from a well-known URI, and does not specify how information obtained from a well-known URI, and does not specify how
to discover a well-known URI for a particular application. to discover a well-known URI for a particular application.
Individual applications using this mechanism must define both Individual applications using this mechanism must define both
aspects; if this is not specified, security issues can arise from aspects; if this is not specified, security issues can arise from
implementation deviations and confusion about boundaries between implementation deviations and confusion about boundaries between
applications. applications.
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where there might be none, giving control to a potential attacker. where there might be none, giving control to a potential attacker.
Likewise, specifying that a well-known URI on a particular hostname Likewise, specifying that a well-known URI on a particular hostname
is to be used to bootstrap a protocol can cause a large number of is to be used to bootstrap a protocol can cause a large number of
undesired requests. For example, if a well-known HTTPS URI is used undesired requests. For example, if a well-known HTTPS URI is used
to find policy about a separate service such as e-mail, it can result to find policy about a separate service such as e-mail, it can result
in a flood of requests to Web servers, even if they don't implement in a flood of requests to Web servers, even if they don't implement
the well-known URI. Such undesired requests can resemble a denial- the well-known URI. Such undesired requests can resemble a denial-
of-services attack. of-services attack.
4.3. Hidden Capabilities 4.4. Hidden Capabilities
Applications using well-known locations should consider that some Applications using well-known locations should consider that some
server administrators might be unaware of its existence (especially server administrators might be unaware of its existence (especially
on operating systems that hide directories whose names begin with on operating systems that hide directories whose names begin with
"."). This means that if an attacker has write access to the .well- "."). This means that if an attacker has write access to the .well-
known directory, they would be able to control its contents, possibly known directory, they would be able to control its contents, possibly
without the administrator realising it. without the administrator realising it.
5. IANA Considerations 5. IANA Considerations
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[REFERRER-POLICY] [REFERRER-POLICY]
Eisinger, J. and E. Stark, "Referrer Policy", World Wide Eisinger, J. and E. Stark, "Referrer Policy", World Wide
Web Consortium CR CR-referrer-policy-20170126, January Web Consortium CR CR-referrer-policy-20170126, January
2017, 2017,
<https://www.w3.org/TR/2017/CR-referrer-policy-20170126>. <https://www.w3.org/TR/2017/CR-referrer-policy-20170126>.
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996, 3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,
<https://www.rfc-editor.org/info/rfc2026>. <https://www.rfc-editor.org/info/rfc2026>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed [RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, Authoring and Versioning (WebDAV)", RFC 4918,
DOI 10.17487/RFC4918, June 2007, DOI 10.17487/RFC4918, June 2007,
<https://www.rfc-editor.org/info/rfc4918>. <https://www.rfc-editor.org/info/rfc4918>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785, Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010, DOI 10.17487/RFC5785, April 2010,
<https://www.rfc-editor.org/info/rfc5785>. <https://www.rfc-editor.org/info/rfc5785>.
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