ABFAB J. Howlett
Internet-Draft JANET(UK)
Intended status: Informational S. Hartman
Expires: September 11, 2011 Painless Security
March 10, 2011

A RADIUS Attribute for SAML Messages


This document defines the SAML-Message attribute for use with the RADIUS protocol. This attribute is used for encapsulating Security Assertion Mark-up Language (SAML) messages.

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Table of Contents

1. Introduction

The SAML-Message attribute has motivated by the requirements of the ABFAB architecture [I-D.lear-abfab-arch]. In this architecture, the attribute is used to convey Security Assertion Mark-up Language (SAML) messages between a SAML requester and responder.

In the SAML model, the composition of such message exchanges with an underlying transport protocol is known as a SAML binding. SAML already defines [OASIS.saml-bindings-2.0-os] a number of mainly HTTP-based bindings, principally (although by no means exclusively) for use with the SAML Web Browser Single Sign-On Profile [OASIS.saml-profiles-2.0-os].

In the ABFAB architecture, AAA-based transport protocols are used to convey SAML messages. This document defines a RADIUS attribute required for binding SAML to RADIUS [RFC2865] transport. A draft document exists that describes a proposed binding, but it has not yet been submitted to the OASIS Security Services Technical Committee. This is pending conclusions on the following aspects of the ABFAB architecture:

This attribute is likely to be useful for other purposes besides ABFAB; an example of a potential application is SAML-based authorisation for network access.

2. Conventions

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 RFC 2119 [RFC2119].

3. SAML Message Attribute

This attribute contains a SAML [OASIS.saml-core-2.0-os] message. Where multiple SAML-Message attributes are included in a RADIUS message, the Message fields of these attributes are to be concatenated to form a single SAML message.

A summary of the SAML-Message format is shown below. The fields are transmitted from left to right.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|     Type      |    Length     |         SAML Message...

                                 Figure 1

4. Security Considerations


5. IANA Considerations

Assignments of additional enumerated values for the RADIUS attributes defined in this document are to be processed as described in [RFC3575], subject to the additional requirements of a published specification.

6. References

6.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2865] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000.
[OASIS.saml-core-2.0-os] Cantor, S., Kemp, J., Philpott, R. and E. Maler, "Assertions and Protocol for the OASIS Security Assertion Markup Language (SAML) V2.0", OASIS Standard saml-core-2.0-os, March 2005.
[RFC3575] Aboba, B., "IANA Considerations for RADIUS (Remote Authentication Dial In User Service)", RFC 3575, July 2003.

6.2. Informative References

[I-D.jones-diameter-abfab] Jones, M and H Tschofenig, "The Diameter 'Application Bridging for Federated Access Beyond Web (ABFAB)' Application", Internet-Draft draft-jones-diameter-abfab-00, March 2011.
[I-D.lear-abfab-arch] Howlett, J, Hartman, S, Tschofenig, H and E Lear, "Application Bridging for Federated Access Beyond Web (ABFAB) Architecture", Internet-Draft draft-lear-abfab-arch-02, March 2011.
[OASIS.saml-bindings-2.0-os] Cantor, S., Hirsch, F., Kemp, J., Philpott, R. and E. Maler, "Bindings for the OASIS Security Assertion Markup Language (SAML) V2.0", OASIS Standard saml-bindings-2.0-os, March 2005.
[OASIS.saml-profiles-2.0-os] Hughes, J., Cantor, S., Hodges, J., Hirsch, F., Mishra, P., Philpott, R. and E. Maler, "Profiles for the OASIS Security Assertion Markup Language (SAML) V2.0", OASIS Standard OASIS.saml-profiles-2.0-os, March 2005.

Authors' Addresses

Josh Howlett JANET(UK) Lumen House, Library Avenue, Harwell Oxford, OX11 0SG UK Phone: +44 1235 822363 EMail: Josh.Howlett@ja.net
Sam Hartman Painless Security EMail: hartmans-ietf@mit.edu