SAML V2.0 Kerberos Attribute Profile Version 1.0

Committee Draft 01

15 December 2009

Specification URIs:

This Version:

http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-attribute-kerberos-cd-01.html

http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-attribute-kerberos-cd-01.odt (Authoritative)

http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-attribute-kerberos-cd-01.pdf

Previous Version:

N/A

Latest Version:

http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-attribute-kerberos.html

http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-attribute-kerberos.odt

http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-attribute-kerberos.pdf

Technical Committee:

OASIS Security Services TC

Chair(s):

Hal Lockhart, Oracle, Inc.

Thomas Hardjono, MIT

Editor(s):

Josh Howlett, Individual

Thomas Hardjono, MIT

Declared XML Namespace(s):

urn:oasis:names:tc:SAML:2.0:profiles:attribute:kerberos

Abstract:

This specification defines an attribute profile for the Kerberos protocol.

Status:

This document was last revised or approved by the SSTC on the above date. The level of approval is also listed above. Check the "Latest Version" or "Latest Approved Version" location noted above for possible later revisions of this document.

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The non-normative errata page for this specification is located at http://www.oasis-open.org/committees/security.

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Table of Contents

1 Introduction5

1.1 Terminology5

1.2 Normative References5

2 SAML 2.0 Kerberos Attribute Profile6

2.1 Required Information6

2.2 Profile Overview6

2.3 SAML Attribute Naming6

2.3.1 Attribute Name Comparison6

2.4 Profile-Specific XML Attributes6

2.5 SAML Attribute Values6

2.6 Attribute Definition6

2.7 Examples7

3 Conformance8

3.1 SAML 2.0 Kerberos Attribute Profile8

Appendix A. Acknowledgments9

Appendix B. Revision History10

 

1 Introduction

The SAML V2.0 Kerberos Attribute Profile describes a SAML attribute profile for requesting and expressing Kerberos protocol messages.

1.1 Terminology

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this specification are to be interpreted as described in IETF RFC 2119.

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.

[RFC 4120]C. Neuman et al. The Kerberos Network Authentication Service (V5). IETF RFC 4120, July 2005. http://www.ietf.org/rfc/rfc4120.txt.

[RFC 3061]M. Mealling. A URN Namespace of Object Identifiers. IETF RFC 3061, February 2001. http://www.ietf.org/rfc/rfc3061.txt.

[Kerberos-XSD]J. Howlett et al., “Kerberos SAML schema Version 2.0”. OASIS SSTC, November 2009.  http://www.oasis-open.org/apps/org/workgroup/security/saml-schema-kerberos-2.0.

[RFC 2045]N. Freed et al. Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies. IETF RFC 2045, November 1996.  http://www.ietf.org/rfc/rfc2045.txt.

2 SAML 2.0 Kerberos Attribute Profile

2.1 Required Information

Identification:  urn:oasis:names:tc:SAML:2.0:profiles:attribute:kerberos

Contact information: security-services-comment@lists.oasis-open.org

Description: Given below.

Updates: None.

2.2 Profile Overview

This specification describes a SAML attribute profile that can be used to request and express Kerberos protocol messages. In this version of the specification, this is constrained to the Kerberos AP-REQ message type. The mechanisms that are used to generate the Kerberos message are outside the scope of this document and are described by [RFC 4120].

2.3 SAML Attribute Naming

The NameFormat XML attribute in <Attribute> elements MUST be urn:oasis:names:tc:SAML:2.0:attrname-format:uri.

2.3.1 Attribute Name Comparison

Two <Attribute> elements refer to the same SAML attribute if and only if their Name XML attribute values are equivalent in the sense of [RFC 3061]. The FriendlyName attribute plays no role in the comparison.

2.4 Profile-Specific XML Attributes

No additional XML attributes are defined for use with the <Attribute> element.

2.5 SAML Attribute Values

The value of this attribute is a Kerberos message that is expressed using the <KerberosData> element defined in the XML namespace urn:oasis:names:tc:SAML:2.0:attribute:kerberos.

When comparing attribute values for equality, an attribute value which does not contain a <KerberosMessage> element MUST be considered equivalent to any other value. This rule is necessary to satisfy the equality condition stipulated in section 3.3.2.3 of [SAMLCore], in the case where the attribute is used within the <AttributeQuery> element.

2.6 Attribute Definition

This profile currently defines a single multi-valued attribute named “ap-req”.

Name: urn:oasis:names:tc:SAML:2.0:profiles:attribute:kerberos:ap-req

An <AttributeValue> element MUST contain a single <KerberosData> element from the XML namespace urn:oasis:names:tc:SAML:2.0:attribute:kerberos. For purposes of human readability, there may also be a requirement for some applications to carry an optional string name together with the URI. The optional XML attribute FriendlyName (defined in [SAMLCore]) MAY be used for this purpose.

When used to request a Kerberos AP-REQ message, this element MUST include a single instance of the <KerberosSname> element, naming the intended service principal, and SHOULD include a single instance of the <KerberosCname> element, naming the preferred user principal.

When used to express a Kerberos AP-REQ message, this element MUST include single instances of the <KerberosSname> and <KerberosCame> elements naming the service and user principals associated with the AP-REQ message and a single instance of the <KerberosMessage> element whose value takes the base64-encoded [RFC 2045] representation of the AP-REQ message and whose KerberosMsgType attribute MUST take a value of “KRB_AP_REQ”.

The issuer SHOULD attempt to satisfy the user principal named by the requester, if given, but MAY use any other user principal (for example, if a local policy forbids or requires a particular user principal for a service).

The AP-REQ issued in a <KerberosMessageData> element MUST conform to [RFC 4120].

2.7 Examples

A SAML requester issues a request to a SAML attribute authority for a Kerberos AP-REQ message:

<saml:Attribute

        xmlns:kerberos="urn:oasis:names:tc:SAML:2.0:attribute:kerberos"

        NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri"

        Name="urn:oasis:names:tc:SAML:2.0:profiles:attribute:kerberos:ap-req">

<saml:AttributeValue>

<kerberos:KerberosData>

<kerberos:KerberosCname>

joe@EXAMPLE.ORG

</kerberos:KerberosCname>

<kerberos:KerberosSname>

http/www@EXAMPLE.ORG

</kerberos:KerberosSname>

</kerberos:KerberosData>

</saml:AttributeValue>

</saml:Attribute>

A SAML attribute authority returns a Kerberos AP-REQ message:

<saml:Attribute

        xmlns:kerberos="urn:oasis:names:tc:SAML:2.0:attribute:kerberos"

        NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri"

        Name="urn:oasis:names:tc:SAML:2.0:profiles:attribute:kerberos:ap-req"

<saml:AttributeValue>

<kerberos:KerberosData>

<kerberos:KerberosCname>

joe@EXAMPLE.ORG

</kerberos:KerberosCname>

<kerberos:KerberosSname>

http/www@EXAMPLE.ORG

</kerberos:KerberosSname>

<kerberos:KerberosMessage KerberosMsgType=”KRB_AP_REQ”>

...base64 representation of an AP-REQ message...

</kerberos:Message>

</kerberos:KerberosData>

</saml:AttributeValue>

</saml:Attribute>

3 Conformance

3.1 SAML 2.0 Kerberos Attribute Profile

An asserting party implementation conforms to this profile if it can produce assertions and other SAML-defined content consistent with the normative text of section 2 .

A relying party implementation conforms to this profile if it can accept assertions and other SAML-defined content consistent with the normative text of section 2 .

 

  1. Appendix A. Acknowledgments 

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

 

The editor would also like to acknowledge the following particular individuals who contributed to the development of this document:

 

 

 

 

 

  1. Appendix B. Revision History 

 

Document ID

Date

Committer

Comment

sstc-saml-attribute-kerberos-draft-01

7 Aug 2009

J. Howlett

Initial draft

sstc-saml-attribute-kerberos-draft-02

3 Sep 2009

J. Howlett

Response to comments

sstc-saml-attribute-kerberos-cd-01

18 Nov 2009

J. Howlett

Committee Draft 01