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Network Working Group                                      I. Young, Ed.
Internet-Draft                                               Independent
Intended status: Informational                              L. Johansson
Expires: January 18, 2018                                          SUNET
                                                               S. Cantor
                                                   Shibboleth Consortium
                                                           July 17, 2017


                The Entity Category SAML Attribute Types
                     draft-young-entity-category-05

Abstract

   This document describes a SAML entity attribute which can be used to
   assign category membership semantics to an entity, and a second
   attribute for use in claiming interoperation with or support for
   entities in such categories.

   This document is a product of the Research and Education Federations
   (REFEDS) Working Group process.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on January 18, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  REFEDS Document Process . . . . . . . . . . . . . . . . .   3
   2.  Notation and Conventions  . . . . . . . . . . . . . . . . . .   3
   3.  Entity Category Attribute . . . . . . . . . . . . . . . . . .   4
     3.1.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Semantics . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Entity Category Example . . . . . . . . . . . . . . . . .   5
   4.  Entity Category Support Attribute . . . . . . . . . . . . . .   6
     4.1.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Semantics . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Entity Category Support Example . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  11
   Appendix B.  Change Log (to be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . .  11
     B.1.  Since draft-young-entity-category-04  . . . . . . . . . .  11
     B.2.  Since draft-young-entity-category-03  . . . . . . . . . .  11
     B.3.  Since draft-young-entity-category-02  . . . . . . . . . .  11
     B.4.  Since draft-young-entity-category-01  . . . . . . . . . .  12
     B.5.  Since draft-young-entity-category-00  . . . . . . . . . .  12
     B.6.  Since draft-macedir-entity-category . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   This document describes a SAML attribute, referred to here as the
   "entity category attribute", values of which represent entity types
   or categories.  When used with the SAML V2.0 Metadata Extension for
   Entity Attributes [SAML2MetadataAttr] each such entity category
   attribute value represents a claim that the entity thus labelled
   meets the requirements of, and is asserted to be a member of, the
   indicated category.

   These category membership claims MAY be used by a relying party to
   provision policy for release of attributes from an identity provider,
   to influence user interface decisions such as those related to
   identity provider discovery, or for any other purpose.  In general,
   the intended uses of any claim of membership in a given category will




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   depend on the details of the category's definition, and will often be
   included as part of that definition.

   Entity category attribute values are URIs, and this document does not
   specify a controlled vocabulary.  Category URIs may therefore be
   defined by any appropriate authority without any requirement for
   central registration.  It is anticipated that other specifications
   may provide management and discovery mechanisms for entity category
   attribute values.

   A second SAML attribute, referred to here as the "entity category
   support attribute", contains URI values which represent claims that
   an entity supports and/or interoperates with entities in a given
   category or categories.  These values, defined in conjunction with
   specific entity category values, provide entities in a category with
   the means to identify peer entities that wish to interact with them
   in category-specific fashion.

   This document does not specify any values either for the entity
   category attribute or for the entity category support attribute.

1.1.  REFEDS Document Process

   The Research and Education Federations group ([REFEDS]) is the voice
   that articulates the mutual needs of research and education identity
   federations worldwide.  It aims to represent the requirements of
   research and education in the ever-growing space of access and
   identity management.

   From time to time REFEDS will wish to publish a document in the
   Internet RFC series.  Such documents will be published as part of the
   RFC Independent Submission Stream [RFC4844]; however the REFEDS
   working group sign-off process will have been followed for these
   documents, as described in the REFEDS Participant's Agreement
   [REFEDS.agreement].

   This document is a product of the REFEDS Working Group process.

2.  Notation and 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 [BCP14].








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3.  Entity Category Attribute

3.1.  Syntax

   Entity category attribute values MUST be URIs.  It is RECOMMENDED
   that http:-scheme or https:-scheme URLs are used, and further
   RECOMMENDED that each such value resolves to a human-readable
   document defining the category.

   The entity category attribute MUST be encoded as a SAML 2.0 Attribute
   element with @NameFormat urn:oasis:names:tc:SAML:2.0:attrname-
   format:uri and @Name http://macedir.org/entity-category.

   A SAML entity is associated with one or more categories by including
   the Attribute element described here in the entity's metadata through
   use of the [SAML2MetadataAttr] metadata extension, in which the
   Attribute element is contained within an mdattr:EntityAttributes
   element directly contained within an md:Extensions element directly
   contained within the entity's md:EntityDescriptor.

   The meaning of the entity category attribute is undefined by this
   specification if it appears anywhere else within a metadata instance,
   or within any other XML document.

   If the entity category attribute Attribute element appears more than
   once in the metadata for an entity, the combined set of associated
   attribute values SHOULD be interpreted by relying parties as if they
   all appeared within a single Attribute element.

3.2.  Semantics

   The presence of the entity category attribute within an entity's
   entity attributes represents a series of claims (one for each
   attribute value) that the entity is a member of each named category.
   The precise semantics of such a claim depend on the definition of the
   category itself.

   An entity may be claimed to be a member of more than one category.
   In this case, the entity is claimed to meet the requirements of each
   category independently unless otherwise specified by the category
   definitions themselves.

   The definition of the concept of a category is intentionally not
   addressed in this document, in order to leave it as general as
   possible.  However, to be useful, category definitions SHOULD include
   the following as appropriate:





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   o  A definition of the authorities who may validly assert membership
      in the category.  While membership in some categories may be self-
      asserted informally by an entity's owner, others may need to be
      validated by third parties such as the entity's home federation or
      other registrar.

   o  A set of criteria by which an entity's membership in the category
      can be objectively assessed.

   o  A definition of the processes by which valid authorities may
      determine that an entity meets the category's membership criteria.

   o  A description of the anticipated uses for category membership by
      relying parties.

   o  A statement indicating the applicability or otherwise of
      membership of the entity category to different SAML role
      descriptors, and any protocol support restrictions that may be
      relevant.

   Entity categories SHOULD NOT be used to indicate the certification
   status of an entity regarding its conformance to the requirements of
   an identity assurance framework.  The [SAML2IDAssuranceProfile]
   extension SHOULD be used for this purpose.

   If significant changes are made to a category definition, the new
   version of the category SHOULD be represented by a different category
   URI so that the old and new versions can be distinguished by a
   relying party.

   No ordering relation is defined over entity category value URIs.
   Entity category attribute value URIs MUST be treated as opaque
   strings for the purpose of comparison.

3.3.  Entity Category Example
















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   <md:EntityDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"
     entityID="https://service.example.com/entity">
     <md:Extensions>
       <mdattr:EntityAttributes
         xmlns:mdattr="urn:oasis:names:tc:SAML:metadata:attribute">
         <Attribute xmlns="urn:oasis:names:tc:SAML:2.0:assertion"
           NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri"
           Name="http://macedir.org/entity-category">
           <AttributeValue
             >http://example.org/category/dog</AttributeValue>
           <AttributeValue>urn:oid:1.3.6.1.4.1.21829</AttributeValue>
         </Attribute>
       </mdattr:EntityAttributes>
     </md:Extensions>
     ...
   </md:EntityDescriptor>

4.  Entity Category Support Attribute

4.1.  Syntax

   Entity category support attribute values MUST be URIs.  It is
   RECOMMENDED that http:-scheme or https:-scheme URLs are used, and
   further RECOMMENDED that each such value resolves to a human-readable
   document defining the value's semantics.  A given entity category
   value MAY be associated with multiple support values in order to
   allow for multiple forms of support, participation, or interoperation
   with entities in the category.

   The entity category support attribute MUST be encoded as a SAML 2.0
   Attribute element with @NameFormat
   urn:oasis:names:tc:SAML:2.0:attrname-format:uri and @Name
   http://macedir.org/entity-category-support.

   Claims that a SAML entity implements support for one or more
   categories are represented by including the Attribute element
   described here in the entity's metadata through use of the
   [SAML2MetadataAttr] metadata extension, in which the Attribute
   element is contained within an mdattr:EntityAttributes element
   directly contained within an md:Extensions element directly contained
   within the entity's md:EntityDescriptor.

   The meaning of the entity category support attribute is undefined by
   this specification if it appears anywhere else within a metadata
   instance, or within any other XML document.

   If the entity category support attribute Attribute element appears
   more than once in the metadata for an entity, the combined set of



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   associated attribute values SHOULD be interpreted by relying parties
   as if they all appeared within a single Attribute element.

4.2.  Semantics

   The presence of the entity category support attribute within an
   entity's entity attributes represents a series of claims (one for
   each attribute value) that the entity supports peer entities in a
   category in a particular fashion.  The precise semantics of such a
   claim depend on the definition of the category support identifier
   itself.  Category support claims will often be defined to be self-
   asserted.

   An entity may be claimed to support more than one category.  In this
   case, the entity is claimed to meet the support requirements of each
   category independently unless otherwise specified by the category
   definitions themselves.

   The definition of the concept of "support" for a category is
   intentionally not addressed in this document, in order to leave it as
   general as possible.  It is assumed that entity category definitions
   MAY define one or more support values signifying particular
   definitions for "support" by peers as motivated by use cases arising
   from the definition of the category itself.

   A common case is expected to be the definition of a single support
   value whose URI is identical to that defined for the category itself.

   If significant changes are made to a category support definition, the
   new version SHOULD be represented by a different category support URI
   so that the old and new versions can be distinguished by a relying
   party.

   No ordering relation is defined over entity category value URIs.
   Entity category attribute value URIs MUST be treated as opaque
   strings for the purpose of comparison.

4.3.  Entity Category Support Example













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   <md:EntityDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"
     entityID="https://idp.example.edu/entity">
     <md:Extensions>
       <mdattr:EntityAttributes
         xmlns:mdattr="urn:oasis:names:tc:SAML:metadata:attribute">
         <Attribute xmlns="urn:oasis:names:tc:SAML:2.0:assertion"
           NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri"
           Name="http://macedir.org/entity-category-support">
           <AttributeValue
             >http://example.org/category/dog/basic</AttributeValue>
           <AttributeValue
             >http://example.org/category/dog/advanced</AttributeValue>
           <AttributeValue>urn:oid:1.3.6.1.4.1.21829</AttributeValue>
         </Attribute>
       </mdattr:EntityAttributes>
     </md:Extensions>
     ...
   </md:EntityDescriptor>

5.  IANA Considerations

   This memo includes no request to IANA.

6.  Security Considerations

   The presence of the entity category attribute within an entity's
   entity attributes represents a series of claims (one for each
   attribute value) that the entity is a member of the named categories.
   Before accepting and acting on such claims, any relying party needs
   to establish, at a level of assurance sufficient for the intended
   use, a chain of trust concluding that the claim is justified.

   Some of the elements in such a chain of trust might include:

   o  The integrity of the metadata delivered to the relying party, as
      for example assured by a digital signature.

   o  If the entity category attribute is carried within a signed
      assertion, the assertion itself must be evaluated.

   o  The policies and procedures of the immediate source of the
      metadata; in particular, any procedures the immediate source has
      with regard to aggregation of metadata from other sources.

   o  The policies and procedures implemented by agents along the
      publication path from the original metadata registrar: this may be
      determined either by examination of the published procedures of
      each agent in turn, or may be simplified if the entity metadata



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      includes publication path metadata in mdrpi:PublicationPath
      elements as described in [SAML2MetadataRPI] section 2.3.1.

   o  The policies and procedures implemented by the original metadata
      registrar.  The registrar's identity may be known implicitly, or
      may be determined from the entity metadata if it includes an
      mdrpi:RegistrationInfo element and corresponding
      @registrationAuthority attribute as described in
      [SAML2MetadataRPI] section 2.1.1.

   o  The definition of the category itself; in particular, any
      statements it makes about whether membership of the category may
      be self-asserted, or may only be asserted by particular
      authorities.

   Although entity category support attribute values will often be
   defined as self-asserted claims by the containing entity, the
   provenance of the metadata remains relevant to a relying party's
   decision to accept a claim of support as legitimate, and the specific
   definition of a support claim will influence the assurance required
   to act on it.

   The conclusion that a claim of category membership or support is
   justified and should be acted upon may require a determination of the
   origin of the claim.  This may not be necessary if the immediate
   source of the metadata is trusted to such an extent that the trust
   calculation is essentially delegated to it.

   In many cases, a claim will be included in an entity's metadata by
   the original metadata registrar on behalf of the entity's owner, and
   the mdrpi:RegistrationInfo element's @registrationAuthority attribute
   is available to carry the registrar's identity.  However, any agent
   that is part of the chain of custody between the original registrar
   and the final relying party may have added, removed or transformed
   claims according to local policy.  For example, an agent charged with
   redistributing metadata may remove claims it regards as
   untrustworthy, or add others which were not already present if they
   have value to its intended audience.

7.  References

7.1.  Normative References

   [BCP14]    Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.






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   [SAML2MetadataAttr]
              Cantor, S., Ed., "SAML V2.0 Metadata Extension for Entity
              Attributes", August 2009,
              <http://wiki.oasis-open.org/security/SAML2MetadataAttr>.

   [SAML2MetadataRPI]
              La Joie, C., Ed., "SAML V2.0 Metadata Extensions for
              Registration and Publication Information Version 1.0",
              April 2012,
              <http://wiki.oasis-open.org/security/SAML2MetadataDRI>.

7.2.  Informative References

   [REFEDS]   Research and Education Federations, "REFEDS Home Page",
              <http://www.refeds.org/>.

   [REFEDS.agreement]
              Research and Education Federations, "REFEDS Participant's
              Agreement", <https://refeds.org/about/refeds-participants-
              agreement>.

   [RFC4844]  Daigle, L. and Internet Architecture Board, "The RFC
              Series and RFC Editor", RFC 4844, July 2007.

   [SAML2IDAssuranceProfile]
              Morgan, RL., Ed., Madsen, P., Ed., and S. Cantor, Ed.,
              "SAML V2.0 Identity Assurance Profiles Version 1.0",
              November 2010, <https://wiki.oasis-open.org/security/
              SAML2IDAssuranceProfile>.






















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Appendix A.  Acknowledgements

   This work has been a collaborative effort within the REFEDS and MACE-
   Dir communities.  Special thanks to (in no particular order):

   o  RL 'Bob' Morgan

   o  Ken Klingenstein

   o  Keith Hazelton

   o  Steven Olshansky

   o  Mikael Linden

   o  Nicole Harris

   o  Tom Scavo

Appendix B.  Change Log (to be removed by RFC Editor before publication)

B.1.  Since draft-young-entity-category-04

   No substantive changes.

B.2.  Since draft-young-entity-category-03

   Additional improvements in response to IETF Gen-Art review:

   o  Section 3.2: additional SHOULD language recommending that category
      definitions include applicability information for particular SAML
      role descriptors.

   o  Section 3.2: added an informative reference to
      [SAML2IDAssuranceProfile] and language recommending its use over
      entity categories where appropriate.

B.3.  Since draft-young-entity-category-02

   Fix link to the REFEDS Participant's Agreement [REFEDS.agreement].

   Clarifications in response to IETF Gen-Art review:

   o  Section 1: make explicit the fact that we don't specify any values
      of either attribute in this document.

   o  Section 3.1, Section 4.1: clarify that it is possible for
      attribute values to appear within multiple Attribute elements, and



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      that this SHOULD be regarded as equivalent to combining them
      within a single Attribute element.

   o  Section 3.2, Section 4.2: clarify the expectation that categories
      are independent unless their definitions say otherwise.

   o  Section 3.2, Section 4.2: If significant changes are made to a
      category definition, the new version of the category SHOULD be
      represented by a different category URI *so that the old and new
      versions can be distinguished by a relying party*.

   o  Section 3.2, Section 4.2: *No ordering relation is defined over
      entity category value URIs.* Entity category attribute value URIs
      MUST be treated as opaque strings *for the purpose of comparison*.

B.4.  Since draft-young-entity-category-01

   Changes from REFEDS consultation process:

   1.  Simplify title from "The Entity Category SAML Entity Metadata
       Attribute Types" to "The Entity Category SAML Attribute Types".

   2.  Clarify the use of [SAML2MetadataRPI] in Section 6 by indicating
       the elements and attributes to be used, and the sections of
       [SAML2MetadataRPI] in which they are defined.

   3.  Remove any implication that category and category support claims
       are necessarily being made "by" the entity itself.

   4.  Clarify that the origin of a category membership or support claim
       may not always be the original registrar.

   Grammar fix in Abstract.

   Change the reference anchor for the SAML [SAML2MetadataRPI]
   extension, as it now more commonly known as RPI than its original DRI
   abbreviation.

B.5.  Since draft-young-entity-category-00

   Update affiliations for Leif Johansson and Scott Cantor.

   Remove authors from acknowledgements.

   Reorganize some of the introductory boilerplate sections.






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B.6.  Since draft-macedir-entity-category

   Adopted as base for draft-young-entity-category-00.

   Changed ipr from "pre5378Trust200902" to "trust200902" and submission
   type from IETF to independent.

   Designate Ian Young as editor for this version.  Set more general
   affiliation.

   Modernised reference to RFC 2119 [BCP14] and moved that reference to
   the introduction.

   Adjusted layout of examples so that they don't exceed the RFC
   standard line length.

   Minor typographical nits but (intentionally) no substantive content
   changes.

Authors' Addresses

   Ian A. Young (editor)
   Independent

   EMail: ian@iay.org.uk


   Leif Johansson
   SUNET

   EMail: leifj@sunet.se


   Scott Cantor
   Shibboleth Consortium

   EMail: cantor.2@osu.edu














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