Internet Engineering Task Force (IETF) M. West
Request for Comments: 7762 Google, Inc
Category: Informational January 2016
ISSN: 2070-1721
Initial Assignment for the Content Security Policy Directives Registry
Abstract
This document establishes an Internet Assigned Number Authority
(IANA) registry for Content Security Policy directives and populates
that registry with the directives defined in the Content Security
Policy Level 2 specification.
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; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7762.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 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
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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.
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RFC 7762 Content Security Policy Registry Assignments January 2016
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Use of the Registry . . . . . . . . . . . . . . . . . . . . . 2
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4.1. Content Security Policy Directives Registry . . . . . . . 3
4.2. Registration Policy for Content Security Policy
Directives . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Content Security Policy (CSP) specification [CSP] defines a
mechanism that web developers can use to control the resources that a
particular page can fetch or execute, as well as a number of
additional security-relevant policy decisions.
The policy language specified in that document consists of an
extensible set of "directives", each of which controls a specific
resource type or policy decision. This specification establishes a
registry to ensure that extensions to CSP are listed and
standardized.
2. 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 [RFC2119].
3. Use of the Registry
Content Security Policy directives must be documented in a readily
available public specification in order to be registered by IANA.
This documentation MUST fully explain the syntax, intended usage, and
semantics of the directive. The intent of this requirement is to
assure interoperable independent implementations, and to prevent
accidental namespace collisions between implementations of dissimilar
features.
Documents defining new Content Security Policy directives MUST
register them with IANA, as described in Section 3. The IANA
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registration policy for such parameters is "Specification Required"
[RFC5226] and is further discussed in Section 3.2.
4. IANA Considerations
This specification creates a new top-level IANA registry named
"Content Security Policy Directives".
4.1. Content Security Policy Directives Registry
New Content Security Policy directives, and updates to existing
directives, MUST be registered with IANA.
When registering a new Content Security Policy directive, the
following information MUST be provided:
o The directive's name, an ASCII string conforming to the
"directive-name" rule specified in Section 4.1 of [CSP]. The ABNF
[RFC5234] is as follows:
directive-name = 1*( ALPHA / DIGIT / "-" )
o A reference to the readily available public specification defining
the new directive's syntax, usage, and semantics.
The following table contains the initial values for this registry:
+-----------------+-----------+
| Directive Name | Reference |
+-----------------+-----------+
| base-uri | [CSP] |
| child-src | [CSP] |
| connect-src | [CSP] |
| default-src | [CSP] |
| font-src | [CSP] |
| form-action | [CSP] |
| frame-ancestors | [CSP] |
| frame-src | [CSP] |
| img-src | [CSP] |
| media-src | [CSP] |
| object-src | [CSP] |
| plugin-types | [CSP] |
| report-uri | [CSP] |
| sandbox | [CSP] |
| script-src | [CSP] |
| style-src | [CSP] |
+-----------------+-----------+
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4.2. Registration Policy for Content Security Policy Directives
The registration policy for Content Security Policy directives is
"Specification Required" [RFC5226], which uses a designated expert to
review the specification.
When appointing an Expert (or Experts), the IESG SHOULD draw from the
W3C's security community, coordinating through the liaison.
The designated expert, when deliberating on whether to include a new
directive in the registry, SHOULD consider the following criteria.
This is not an exhaustive list, but representative of the issues to
consider when rendering a decision:
o Content Security Policy is a restrictive feature, which allows web
developers to deny themselves access to resources and APIs that
would otherwise be available. Deploying Content Security Policy
is, therefore, a strict reduction in risk. The expert SHOULD
carefully consider whether proposed directives would violate this
property.
o Granular directives are valuable, but the expert SHOULD strive to
strike a reasonable balance between providing developers with all
the knobs and switches possible and providing only those with
known security implications.
5. Security Considerations
The registry in this document does not in itself have security
implications. The directives specified, however, certainly do. The
documents referenced when registering new directives MUST contain
detailed security and privacy considerations sections, and SHOULD
contain usage information that informs web developers as to the
directive's expected implementation.
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6. References
6.1. Normative References
[CSP] West, M., Barth, A., and D. Veditz, "Content Security
Policy Level 2", July 2015, <https://www.w3.org/TR/CSP2>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
6.2. Informative References
[RFC5341] Jennings, C. and V. Gurbani, "The Internet Assigned Number
Authority (IANA) tel Uniform Resource Identifier (URI)
Parameter Registry", RFC 5341, DOI 10.17487/RFC5341,
September 2008, <http://www.rfc-editor.org/info/rfc5341>.
Acknowledgements
Much of this document's structure comes from [RFC5341]. Thank you to
Cullen Jennings and Vijay K. Gurbani for giving me a reasonable
template to work within and to Barry Leiba for his helpful commentary
and suggestions.
Author's Address
Mike West
Google, Inc
Email: mkwst@google.com
URI: https://mikewest.org/
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