This document defines an extension to the SAML 2.0 Single Logout Protocol that allows the initiator to indicate that it does not expect to receive a response from the session authority. This improves user interface interoperability in deployments that want the identity provider to control the user experience during logout.

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[SAML-Async-SLO]

SAML V2.0 Asynchronous Single Logout Profile Extension Version 1.0. 22 November 2012. OASIS Committee Specification 01. http://docs.oasis-open.org/security/saml/Post2.0/saml-async-slo/v1.0/cs01/saml-async-slo-v1.0-cs01.html.

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Table of Contents

1 Introduction................................................................................................................................ 5

1.1 Terminology......................................................................................................................... 5

1.2 Normative References.......................................................................................................... 5

2 Single Logout Protocol Extension for Asynchronous Requests..................................................... 7

2.1 Element <aslo:Asynchronous>............................................................................................. 7

2.2 Asynchronous Logout Request Processing........................................................................... 7

2.3 Metadata Considerations...................................................................................................... 7

3 Conformance.............................................................................................................................. 8

Appendix A Acknowledgments......................................................................................................... 9

Appendix B Revision History.......................................................................................................... 10

1 Introduction

This document defines an extension to the Single Logout Protocol that allows the initiator to indicate that it does not expect to receive a response from the session authority.

The SAML 2 Single Logout Protocol, defined in section 3.7 of [SAMLCore], provides for request delivery over front- and back-channel mechanisms. When logout is begun with an SP-initiated front-channel request, either the session authority or service provider may present a user interface to the user but neither entity knows, or can indicate, that it will perform this task. If both present such a UI, this would likely lead to user confusion. This extension allows the SP to signal to the session authority that the session authority is expected to present the UI.

In addition, an entity may wish to directly initiate a logout (e.g., an administrator destroying a user's session). If such behavior is triggered by the delivery of a SAML 2 logout request (instead of via a proprietary mechanism), this extension informs the sessions authority that a response is not necessary.

1.1 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 [RFC 2119].

Conventional XML namespace prefixes are used throughout the listings in this specification to stand for their respective namespaces as follows, whether or not a namespace declaration is present in the example:

Prefix	XML Namespace	Comments
samlp:	urn:oasis:names:tc:SAML:2.0:protocol	This is the SAML V2.0 protocol namespace defined in the SAML V2.0 core specification [SAMLCore]
aslo:	urn:oasis:names:tc:SAML:2.0:protocol:ext:async-slo	The namespace defined by this document.
xsd:	http://www.w3.org/2001/XMLSchema	This namespace is defined in the W3C XML Schema specification [Schema1]. In schema listings, this is the default namespace and no prefix is shown.
xsi:	http://www.w3.org/2001/XMLSchema-instance	This is the XML Schema namespace for schema-related markup that appears in XML instances [Schema1].

This specification uses the following typographical conventions in text: <ns:Element>, Attribute, Datatype, OtherCode.

This specification uses the following typographical conventions in XML listings:

Listings of XML schemas appear like this.

Listings of XML examples appear like this. These listings are non-normative.

1.2 Normative References

[RFC 2119] S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. IETF RFC 2119, March 1997. http://www.ietf.org/rfc/rfc2119.txt

[SAMLCore] OASIS Approved Standard, Assertions and Protocols for the OASIS Security Assertion Markup Language (SAML) V2.0, March 2005. http://docs.oasis-open.org/security/saml/v2.0/saml-2.0-os.zip

[SAML2Errata] OASIS Approved Errata, SAML V2.0 Errata, May 2012. http://docs.oasis-open.org/security/saml/v2.0/errata05/os/saml-v2.0-errata05-os.pdf

[SAMLMeta] OASIS Approved Standard, Metadata for the OASIS Security Assertion Markup Language (SAML) V2.0, March 2005. http://docs.oasis-open.org/security/saml/v2.0/saml-2.0-os.zip

[Schema1] H. S. Thompson et al. XML Schema Part 1: Structures. World Wide Web Consortium Recommendation, May 2001. See http://www.w3.org/TR/2001/REC- xmlschema-1-20010502/

2 Single Logout Protocol Extension for Asynchronous Requests

2.1 Element <aslo:Asynchronous>

The <aslo:Asynchronous> element indicates that the containing <samlp:LogoutRequest> is an asynchronous request and should be processed as described in the following section.

The <aslo:Asynchronous> element MUST appear within the <samlp:Extensions> element of a <samlp:LogoutRequest> element. The use of the <aslo:Asynchronous> element outside of that context is not defined by this specification.

2.2 Asynchronous Logout Request Processing

When a session authority receives a <samlp:LogoutRequest> containing the asynchronous request extension, the session authority SHALL process the request as described in section 3.7.3.2 of [SAMLCore] except that the session authority MUST NOT send a <samlp:LogoutResponse> to the request initiator.

Note, because no <samlp:LogoutResponse> is sent back to the request initiator, the session authority MUST provide all relevant feedback. For example, in the case of front-channel bindings, the session authority would display a web page indicating the success or failure of the logout process.

2.3 Metadata Considerations

SAML metadata MAY be used to indicate support for this protocol extension at particular protocol endpoints, using the extension capabilities of the metadata schema.

Support for this extension is expressed in SAML V2.0 metadata [SAMLMeta] by adding a boolean-typed XML attribute to an element derived from the md:EndpointType complex type, indicating that SAML request messages sent to that endpoint MAY include this extension.

The following schema fragment defines the aslo:supportsAsynchronous attribute:

3 Conformance

A logout request initiator conforms to this specification if it supports the inclusion of the <aslo:Asynchronous> element as defined in section 2.1 of this specification.

A session authority conforms to this specification if it can processes a logout request as defined primarily by [SAMLCore], as supplemented by section 2.2 of this specification.

Appendix A Acknowledgments

The editors would like to acknowledge the contributions of the OASIS Security Services Technical Committee, whose voting members at the time of publication were:

· Scott Cantor, Internet2

· Chad LaJoie, Internet2,

· Nate Klingenstein, Internet2,

· Thomas Hardjono, M.I.T.

· Frederick Hirsch, Nokia Corporation

· Hal Lockhart, Oracle

· Anil Saldhana, Red Hat

· Duane DeCouteau, Veteran's Health Administration

Appendix B Revision History

Revision	Date	Editor	Changes Made
WD01	July 6, 2012	Chad La Joie	Initial version
WD02	Sep 4, 2012	Scott Cantor	Added metadata portion, and a bit of cleanup.