A RADIUS Attribute for SAML Messages
draft-ietf-abfab-aaa-saml-01

Abstract

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
• 2. Conventions
• 3. SAML Message Attribute
• 4. Security Considerations
• 5. IANA Considerations
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Authors' Addresses

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:

• The use of the SAML attribute query at some arbitrary time after the initial EAP authentication exchange.
• The use of the SAML attribute query to obtain attributes for a principal from more than one attribute authority.
• Alignment with the Diameter ABFAB application [I-D.jones-diameter-abfab].

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

TODO

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

6.2. Informative References

Authors' Addresses