Network Working Group M. West
Internet-Draft Google, Inc
Intended status: Informational October 7, 2015
Expires: April 9, 2016
Content Security Policy Directive Registry
draft-west-webappsec-csp-reg-03
Abstract
This document establishes an Internet Assigned Number Authority
(IANA) registry for Content Security Policy directives. It populates
the registry with the directives defined in the CSP specification.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use of the Registry . . . . . . . . . . . . . . . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 2
3.1. Content Security Policy directives Registry . . . . . . . 3
3.2. Registration Policy for Content Security Policy
directives . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Content Security Policy specification [CSP] defines a mechanism
by which web developers can control the resources which a particular
page can fetch or execute, as well as a number of 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. 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
registration policy for such parameters is "Specification Required"
[RFC5226], and is further discussed in Section 3.2.
3. IANA Considerations
This specification creates a new top-level IANA registry named
"Content Security Policy directives".
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3.1. 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] |
+-----------------+-----------+
3.2. 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.
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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 which
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.
4. 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 which informs web developers as to the
directive's expected implementation.
5. References
5.1. Normative References
[CSP] West, M. and D. Veditz, "Content Security Policy", n.d.,
.
[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,
.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
5.2. 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, .
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Appendix A. 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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