Geopriv C. Guenther
Internet-Draft Siemens
Expires: August 17, 2005 February 13, 2005
SAML in Authorization Policies
draft-guenther-saml-policy-00.txt
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of Section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 17, 2005.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
Rules of an authorization policy prescribe under which conditions an
entity or subject has which permissions. Existing policies support
identity-based authorization by matching the authenticated identity
of the entity requesting access to a resource with the available
policies. This document is about formulating policy rules that
express conditions with respect to SAML assertions, thereby
supporting non-identity-based authorization and anonymity.
Guenther Expires August 17, 2005 [Page 1]
Internet-Draft SAML in Authorization Policies February 2005
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Basic Scenario . . . . . . . . . . . . . . . . . . . . . . . 5
4. SAML Conditions Example . . . . . . . . . . . . . . . . . . 6
5. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 10
8. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Normative References . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . 13
Guenther Expires August 17, 2005 [Page 2]
Internet-Draft SAML in Authorization Policies February 2005
1. Introduction
The Security Assertion Markup Language, see [SAML], is an XML
sublanguage for exchanging security information. It is suitable for
expressing assertions concerning previously performed authentication
procedures and authorization decisions. For example, a SAML
assertion can be used by the assertion issuer to assure that the
assertion subject (e.g., a person, a network entity, ...) has been
authenticated by means of a specific authentication method M. A
recipient of such an assertion - if it has trust in the assertion
issuer and the integrity of the assertion - can then base its
authorization decisions on this assertion.
This document is about defining an extension to the Common Policy
markup language, see [I-D.ietf-geopriv-common-policy], that allows to
express conditions with respect to statements contained in SAML
assertions. It shall be possible to express authorization policy
rules of the following fashion: If the SAML assertion has been issued
by the assertion issuer A and if the assertion assures that the
assertion subject S has been authenticated by means of the
authenticated method M, then S is permitted to ... .
Guenther Expires August 17, 2005 [Page 3]
Internet-Draft SAML in Authorization Policies February 2005
2. 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 [RFC2119].
Guenther Expires August 17, 2005 [Page 4]
Internet-Draft SAML in Authorization Policies February 2005
3. Basic Scenario
Figure 1 depicts a basic scenario in the scope of this document: a
Subject S wishes to have access to a certain resource (e.g., location
information of a particular entity). After a successful
authentication protocol execution between S and the Asserting Party
(AP), see step 1, the AP issues a SAML assertion (step 2), which
asserts that S has been authenticated by AP using method M and is
associated with a certain set of attributes.
+-------------+ 1: Authentication +------------+
| |<----------------->| Asserting |
| Subject S | | Party |
| |<------------------| (AP) |
+-------------+ 2: SAML Assertion +------------+
|
|
3:| Service Request
| + Assertion
v
+-------------+ +------------+
| Relying | 4: Policy | Policy |
| Party |<------------------| Server |
| (RP) | | (PS) |
+-------------+ +------------+
Figure 1: Basic Scenario
After receipt of the assertion, the Relying Party (RP) can base its
resource access authorization decision on this assertion. The
authorization policy governing access to the requested resource is
stored at the Policy Server (PS). Thanks to the language elements
introduced in this document, this policy can contain rules whose
conditions parts express properties that the SAML assertion must meet
in order to make the rule match.
Guenther Expires August 17, 2005 [Page 5]
Internet-Draft SAML in Authorization Policies February 2005
4. SAML Conditions Example
This document extends the Common Policy markup language by adding new
elements to the <condition> substitution group defined in the schema
of the Common Policy markup language, see
[I-D.ietf-geopriv-common-policy]. This paragraph provides a basic
example of an XML document valid with respect to the XML schema
defined in Section 5.
<?xml version="1.0" encoding="UTF-8"?>
<ruleset
xmlns="urn:ietf:params:xml:ns:common-policy"
xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
xmlns:samlc="urn:ietf:params:xml:ns:saml-cond"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"urn:ietf:params:xml:ns:common-policy cp.xsd
urn:ietf:params:xml:ns:saml-cond sc.xsd
urn:oasis:names:tc:SAML:2.0:assertion
sstc-saml-schema-assertion-2.0.xsd ">
<rule id="Hz90op54I">
<conditions>
<samlc:samlcondition>
<saml:Issuer>https://www.idp.com/</saml:Issuer>
<samlc:authnstatement>
<samlc:authncontextclassref>
urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport
</samlc:authncontextclassref>
</samlc:authnstatement>
</samlc:samlcondition>
<validity>
<from>2005-03-06T17:00:00-05:00</from>
<to>2005-03-11T19:00:00-05:00</to>
</validity>
</conditions>
<actions></actions>
</rule>
Guenther Expires August 17, 2005 [Page 6]
Internet-Draft SAML in Authorization Policies February 2005
</ruleset>
The rule set in this example consists of one rule only. The
<conditions> part of the rule consists of a <validity> condition
(defined by the Common Policy schema) and a <samlcondition> condition
which is defined by this document in Section 5. As there is no
<Subject> subelement of <samlcondition>, this rule matches for each
Subject identified in a SAML authentication assertion issued by
idp.com that asserts that the Subject has been authenticated through
the presentation of a password over a protected session (e.g.,
protected by SSL or IPSec).
Guenther Expires August 17, 2005 [Page 7]
Internet-Draft SAML in Authorization Policies February 2005
5. XML Schema
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
targetNamespace="urn:ietf:params:xml:ns:saml-cond"
xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
xmlns:cp="urn:ietf:params:xml:ns:common-policy"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xs:import namespace="urn:oasis:names:tc:SAML:2.0:assertion"
schemaLocation="sstc-saml-schema-assertion-2.0.xsd"/>
<xs:import namespace="urn:ietf:params:xml:ns:common-policy"
schemaLocation="cp.xsd"/>
<xs:element name="samlcondition" substitutionGroup="cp:condition">
<xs:complexType>
<xs:sequence>
<xs:element ref="saml:Issuer" minOccurs="0"/>
<xs:element ref="saml:Subject" minOccurs="0"/>
<xs:element name="authnstatement"
minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="authncontextclassref" type="anyURI"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:compleyType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
Guenther Expires August 17, 2005 [Page 8]
Internet-Draft SAML in Authorization Policies February 2005
6. Security Considerations
[tbd]
Guenther Expires August 17, 2005 [Page 9]
Internet-Draft SAML in Authorization Policies February 2005
7. IANA Considerations
[tbd]
Guenther Expires August 17, 2005 [Page 10]
Internet-Draft SAML in Authorization Policies February 2005
8. Open Issues
1) There are not only authentication assertions in SAML, but also
authorization decision and attribute assertions. Inspect the
usability of these types of SAML assertions in the scope of this
document.
2) Modify and enhance the XML schema in accordance to 1). Possibly,
it could be more appropriate to directly adopt XML element and type
definitions as given in the SAML assertion schema instead of defining
new ones.
3) It could be useful to let the <samlcondition> element represent an
XML schema that specizializes the SAML assertion schema with respect
to the target of the authorization policy. Example: Instaed of
listing all permitted authentication context class references in
<authncontextclassref>, you could write down a target-specific SAML
assertion schema with an <AuthnContextClassRef> element whose
definition is completely identical to the SAML definition of
<AuthnContextClassRef>, except for the fact that only certain URIs
are permitted as values to make the SAML assertion valid with respect
to this specialized assertion schema.
4) Security considerations.
5) IANA considerations.
9. Normative References
[I-D.ietf-geopriv-common-policy]
Schulzrinne, H., Morris, J., Tschofenig, H., Polk, J. and
J. Rosenberg, "A Document Format for Expressing Privacy
Preferences", Internet-Draft draft-ietf-common-policy-03,
October 2004.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[SAML] OASIS, "Assertions and Protocol for the OASIS Security
Assertion Markup Language (SAML) V2.0", OASIS Committee
Draft sstc-saml-core-2.0-cd-04.pdf, January 2005.
Guenther Expires August 17, 2005 [Page 11]
Internet-Draft SAML in Authorization Policies February 2005
Author's Address
Christian Guenther
Siemens
Otto-Hahn-Ring 6
Munich, Bayern 81739
Germany
Email: christian.guenther@siemens.com
Guenther Expires August 17, 2005 [Page 12]
Internet-Draft SAML in Authorization Policies February 2005
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Guenther Expires August 17, 2005 [Page 13]