eXtensible Access Control Markup Language (XACML) XML Media Type
draft-sinnema-xacml-media-type-05

Abstract

This specification registers an XML-based media type for the eXtensible Access Control Markup Language (XACML).

Note to Readers

This draft should be discussed on the apps-discuss mailing list.

Online access to all versions and files is available on github.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on December 20, 2013.

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Table of Contents

• 1. Introduction
• 2. IANA Considerations
• 2.1. XACML Media Type application/xacml+xml
• 3. Security Considerations
• 4. Change Log
• 4.1. From -04 to -05
• 4.2. From -03 to -04
• 4.3. From -02 to -03
• 4.4. From -01 to -02
• 4.5. From -00 to -01
• 4.6. Versions prior to I-D -00
• 5. Normative References
• Appendix A. Acknowledgements
• Authors' Addresses

1. Introduction

The eXtensible Access Control Markup Language (XACML) [XACML-3] defines an architecture and a language for access control (authorization). The language consists of requests, responses, and policies. Clients sends a request to a server to query whether a given action should be allowed. The server evaluates the request against the available policies and returns a reponse. The policies implement the organization's access control requirements.

2. IANA Considerations

This specification registers an XML-based media type for the eXtensible Access Control Markup Language (XACML) that will be registered with the Internet Assigned Numbers Authority (IANA) following the "Media Type Specifications and Registration Procedures" [RFC6838]. The XACML media type represents an XACML request, response, or policy in the XML-based format defined by the core XACML specification [XACML-3].

2.1. XACML Media Type application/xacml+xml

This specification requests the registration of an XML-based media type for the eXtensible Access Control Markup Language (XACML).

2.1.1. Media Type Name

application

2.1.2. Subtype Name

xacml+xml

2.1.3. Required Parameters

none

2.1.4. Optional Parameters

charset: The charset parameter is the same as the charset parameter of application/xml [RFC3023], including the same default (see section 3.2).

version: The version parameter indicates the version of the XACML specification. It can be used for content negotiation when dealing with clients and servers that support multiple XACML versions. Its range is the range of published XACML versions. As of this writing that is: 1.0 [XACML-1], 1.1 [XACML-1.1], 2.0 [XACML-2], and 3.0 [XACML-3]. These and future version identifiers must follow the OASIS patterns for versions [OASIS-Version]. If this parameter is not specified by the client, the server is free to return any version it deems fit. If a client cannot or does not want to deal with that, it should explicitly specify a version.

2.1.5. Encoding Considerations

Same as for application/xml [RFC3023].

2.1.6. Security Considerations

Per their specification, application/xacml+xml typed objects do not contain executable content. However, these objects are XML-based, and thus they have all of the general security considerations presented in section 10 of RFC 3023 [RFC3023].

XACML [XACML-3] contains information whose integrity and authenticity is important - identity provider and service provider public keys and endpoint addresses, for example. Sections "9.2.1 Authentication" and "9.2.4 Policy Integrity" in XACML [XACML-3] describe requirements and considerations for such authentication and integrity protection.

To counter potential issues, the publisher may sign application/xacml+xml typed objects. Any such signature should be verified by the recipient of the data - both as a valid signature, and as being the signature of the publisher. The XACML v3.0 XML Digital Signature Profile [XACML-3-DSig] describes how to use XML-based digital signatures with XACML.

Additionally, various of the possible publication protocols, for example HTTPS, offer means for ensuring the authenticity of the publishing party and for protecting the policy in transit.

2.1.7. Interoperability Considerations

Different versions of XACML use different XML namespace URIS:

• 1.0 & 1.1 use the urn:oasis:names:tc:xacml:1.0:policy XML namespace URI for policies, and the urn:oasis:names:tc:xacml:1.0:context XML namespace URI for requests and responses
• 2.0 uses the urn:oasis:names:tc:xacml:2.0:policy XML namespace URI for policies, and the urn:oasis:names:tc:xacml:2.0:context XML namespace URI for requests and responses
• 3.0 uses the urn:oasis:names:tc:xacml:3.0:core:schema:wd-17 XML namespace URI for policies, requests, and responses

Signed XACML has a wrapping SAML 2.0 assertion [SAML-2], which uses the urn:oasis:names:tc:SAML:2.0:assertion namespace URI. Interoperability with SAML is defined by the SAML 2.0 Profile of XACML [XACML-3-SAML] for all versions of XACML.

2.1.8. Applications which use this media type

Potentially any application implementing or using XACML, as well as those applications implementing or using specifications based on XACML. In particular, applications using the REST Profile [XACML-REST] can benefit from this media type.

2.1.9. Magic number(s)

In general, the same as for application/xml [RFC3023]. In particular, the XML document element of the returned object will be one of xacml:Policy, xacml:PolicySet, context:Request, or context:Response. The xacml and context prefixes differ for the various versions of XACML as follows:

• 1.0 & 1.1: The xacml prefix maps to urn:oasis:names:tc:xacml:1.0:policy, the context prefix maps to urn:oasis:names:tc:xacml:1.0:context
• 2.0: The xacml prefix maps to urn:oasis:names:tc:xacml:2.0:policy, the context prefix maps to urn:oasis:names:tc:xacml:2.0:context
• 3.0: Both the xacml and context prefixes map to the namespace URI urn:oasis:names:tc:xacml:3.0:core:schema:wd-17

For signed XACML [XACML-3-DSig], the XML document element is saml:Assertion, where the saml prefix maps to the SAML 2.0 namespace URI urn:oasis:names:tc:SAML:2.0:assertion [SAML-2]

2.1.10. File extension(s)

none

2.1.11. Macintosh File Type Code(s)

none

2.1.12. Person & email address to contact for further information

This registration is made on behalf of the OASIS eXtensible Access Control Markup Language Technical Committee (XACMLTC). Please refer to the XACMLTC website for current information on committee chairperson(s) and their contact addresses: http://www.oasis-open.org/committees/xacml/. Committee members should submit comments and potential errata to the xacml@lists.oasis-open.org list. Others should submit them by filling out the web form located at http://www.oasis-open.org/committees/comments/form.php?wg_abbrev=xacml.

Additionally, the XACML developer community email distribution list, xacml-dev@lists.oasis-open.org, may be employed to discuss usage of the application/xacml+xml MIME media type. The xacml-dev mailing list is publicly archived here: http://www.oasis-open.org/archives/xacml-dev/. To post to the xacml-dev mailing list, one must subscribe to it. To subscribe, visit the OASIS mailing list page at http://www.oasis-open.org/mlmanage/.

2.1.13. Intended Usage

Common

2.1.14. Author/Change Controller

The XACML specification sets are a work product of the OASIS eXtensible Access Control Markup Language Technical Committee (XACMLTC). OASIS and the XACMLTC have change control over the XACML specification sets.

3. Security Considerations

The security considerations for this specifications are described in Section 2.1.6 of the media type registration.

4. Change Log

Note to RFC Editor: Please remove this section before publication.

4.1. From -04 to -05

• Incorporating feedback from Oscar Koeroo (ISE review report).

4.2. From -03 to -04

• Creating a proper "IANA Considerations" section.
• Creating a proper "Security Considerations" section.

4.3. From -02 to -03

• Switched category from "std" to "info".

4.4. From -01 to -02

• Added new introduction text.
• Improved definition of version numbers and their handling.

4.5. From -00 to -01

• Added new introduction text.
• Changed reference from RFC 4288 to RFC 6838 (updated RFC for media type registrations).

4.6. Versions prior to I-D -00

Prior to being published as a I-D document, this document was published and revised as an OASIS document with the following versions:

• 2012-02-29 (WD01): Initial revision with one media type.
• 2012-04-23 (WD02): Added JSON media type.
• 2012-04-24 (WD03): Fixed layout, typos, and references. Better defined the allowable range of values for the version parameter.

5. Normative References

Appendix A. Acknowledgements

The following individuals have participated in the creation of this specification and are gratefully acknowledged: Oscar Koeroo (Nikhef), Erik Rissanen (Axiomatics), and Jonathan Robie (EMC).

Authors' Addresses