rfc8409.xml

<?xml version="1.0" encoding="US-ASCII"?>

<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no" ?>

<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
]>

<rfc number="8409" ipr="trust200902" submissionType="independent" category="info">

  <front>

    <title abbrev="Entity Category">
      The Entity Category Security Assertion Markup Language (SAML) Attribute&nbsp;Types
    </title>



    <author initials="I.A." fullname="Ian A. Young" surname="Young" role="editor">
      <organization>Independent</organization>
      <address>
        <email>ian@iay.org.uk</email>
      </address>
    </author>

    <author fullname="Leif Johansson" initials="L." surname="Johansson">
      <organization>SUNET</organization>
      <address>
        <email>leifj@sunet.se</email>
      </address>
    </author>

    <author fullname="Scott Cantor" initials="S." surname="Cantor">
      <organization>Shibboleth Consortium</organization>
      <address>
        <email>cantor.2@osu.edu</email>
      </address>
    </author>

    <date month="August" year="2018"/>


    <keyword>REFEDS</keyword>


    <abstract>

      <t>
        This document describes two SAML entity attributes: one that can be
        used to assign category membership semantics to an entity and another
        for use in claiming interoperation with or support for
        entities in such categories.
      </t>
      <t>
        This document is a product of the working group process of the
	      Research and Education FEDerations (REFEDS) group.
      </t>
    </abstract>

  </front>

  <middle>
    <section title="Introduction" anchor="introduction">
      <t>
        This document describes a SAML attribute called the
	"entity category attribute".
        Values of this attribute represent entity types
        or categories. When used with the
        <xref target="SAML2MetadataAttr">SAML V2.0 Metadata Extension for Entity Attributes</xref>,
        each such entity category attribute value represents a claim that the entity thus labeled
        meets the requirements of, and is asserted to be a member of, the indicated category.
      </t>

      <t>
        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
        depend on the details of the category's definition and will often be included as
        part of that definition.
      </t>

      <t>
        Entity category attribute values are URIs. Therefore, this document does not specify a
        controlled vocabulary for assigning such values; they may 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.
      </t>

      <t>
        This document also describes a SAML attribute called the
	"entity category support attribute". This attribute
        contains URI values that 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 attribute values, provide entities in a category with the means to identify
        peer entities that wish to interact with them in a fashion described by the category specification.
      </t>

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

      <section title="REFEDS Document Process">
        <t>
          The Research and Education FEDerations <xref target="REFEDS"/> group
          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.
        </t>
        <t>
          From time to time, REFEDS
          will publish a document in the RFC Series.  Such
          documents will be published as part of the Independent Submission
          stream <xref target="RFC4844"/>; however, the REFEDS Working Group
	  sign-off process will
          have been followed for these documents, as described in
          the <xref target="REFEDS.agreement">REFEDS Participant's Agreement</xref>.
        </t>
        <t>
          This document is a product of the REFEDS Working Group process.
        </t>
      </section>

    </section>

    <section title="Notation and Conventions">

        <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
    NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
    "MAY", and "OPTIONAL" in this document are to be interpreted as
    described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
    when, and only when, they appear in all capitals, as shown here.
        </t>

        <t>
          The notation "@example" is used as a shorthand for an XML attribute
          with attribute name "example".
        </t>

    </section>

    <section title="Entity Category Attribute">
      <section anchor="cat-syntax" title="Syntax">
        <t>
          Entity category attribute values MUST be URIs. Such values are
          also referred to as "category URIs" in this document.
        </t>

        <t>
          It is RECOMMENDED that http:-scheme or https:-scheme URIs are used;
          it is further RECOMMENDED that a category URI
          resolves to a human-readable document defining the category.
        </t>

        <t>
          Authorities defining entity categories MUST produce a specification of the entity
          category and SHOULD make arrangement for the category URI to resolve to the
          specification in human-readable form.
        </t>

        <t>
          Authorities defining entity categories MAY use versioning of category URIs where
          appropriate; if versioning is used, each version of the specification of the entity category
          SHOULD clearly indicate the latest version of the category URI (and hence of the
          specification).



          The specification SHOULD include a description of
          how the authority defining the entity category implements governance
          for the specification if the specification is updated.
        </t>

        <t>
          When used in SAML metadata or protocol elements, 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.
        </t>

        <t>
          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 metadata extension defined in
          <xref target="SAML2MetadataAttr"/>. In this extension, 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.
        </t>

        <t>
          The meaning of the entity category attribute is not defined by this specification if it
          appears anywhere else within a metadata instance or within any other XML document.
        </t>

        <t>
          If the entity category attribute appears more than once in the
          metadata for an entity, relying parties SHOULD interpret the combined
          set of associated attribute values as if they all appeared together
          within a single entity category attribute.
        </t>
      </section>

      <section anchor="cat-semantics" title="Semantics">
        <t>
          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.
        </t>

        <t>
          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.
        </t>



        <t>
          This document intentionally does not define "category", in order to
          leave the concept as general as possible.
          However, to be useful,
          category definitions SHOULD include the following as appropriate:
          <list style="symbols">
            <t>
              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.
            </t>
            <t>
              A set of criteria by which an entity's membership in the category can be
              objectively assessed.
            </t>
            <t>
              A definition of the processes by which valid authorities
              may determine that an entity meets the category's membership criteria.
            </t>
            <t>
              A description of the anticipated uses for category membership by relying parties.
            </t>
            <t>
              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.
            </t>
          </list>
        </t>

        <t>
          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 SAML extension defined in
	  <xref target="SAML2IDAssuranceProfile"/> SHOULD be used
          for this purpose.
        </t>

        <t>
          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. It
          is for this reason that authorities defining entity categories MAY
          employ some form of versioning for category URIs. When versioning is
          used, each version of the entity category MUST be treated as a separate URI.
        </t>



        <t>
          No ordering relation is defined for entity category attribute values.
          Entity category attribute values MUST be treated as opaque strings
          for the purpose of comparison. In particular, if the specification defining the
          entity category relies on versioning of the category URI, a relying
          party MUST NOT assume any particular ordering between different versions of
          the category URI. Any order between versions MUST be spelled out in the
          specification.
        </t>

      </section>

      <section title="Entity Category Example">
        <figure>
          <artwork><![CDATA[<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>]]></artwork>
        </figure>
      </section>
    </section>

    <section title="Entity Category Support Attribute">
      <section anchor="sup-syntax" title="Syntax">



        <t>
          Entity category support attribute values MUST be URIs. Such values are
          also referred to as "category support URIs" in this document.
        </t>

        <t>
          It is RECOMMENDED that http:-scheme or https:-scheme URLs are used;
          it is further RECOMMENDED that each such value
          resolves to a human-readable document defining the value's semantics.
        </t>

        <t>
          A given category URI MAY be associated with multiple category support URIs in
          order to allow for multiple forms of support, participation, or interoperation
          with entities in the category. The authority defining the category URI and
          category support URIs MUST clearly describe the relationship between
          (all versions of) the category URI and (all versions of) the
          category support URIs as applicable in the entity category specification.
        </t>

<!-- [rfced]  We see that http://macedir.org/entity-category redirects to
https://tools.ietf.org/html/draft-young-entity-category-07. In addition,
we encountered a "404 Not Found" when trying to open
http://macedir.org/entity-category-support. Please review and let us know
how to update.

Original:
   When used in SAML metadata or protocol elements, 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.
...
   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.

[9] RESOLVED: these values must not be changed; to do so would be to invalidate
the entire installed base of current users of the mechanism described here.

Note that the values are URIs rather than URLs, so that it is not necessary for
them to resolve to human-readable documents. Nevertheless, we will be working
to make sure that they do resolve to the final RFC at some point. We don't believe
that it is necessary for that to be the case to proceed to publication of the RFC.
-->



        <t>
          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.
        </t>

        <t>
          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 metadata extension defined in <xref
	  target="SAML2MetadataAttr"/>.
          In this extension,
          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.
        </t>

        <t>
          The meaning of the entity category support attribute is not defined by this
          specification if it appears anywhere else within a metadata instance or within
          any other XML document.
        </t>

        <t>
          If the entity category support attribute appears more than once in the
          metadata for an entity, relying parties SHOULD interpret the combined
          set of associated attribute values as if they all appeared together
          within a single entity category support attribute.
        </t>
      </section>

      <section anchor="sup-semantics" title="Semantics">
        <t>
          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 URI itself.
          Category support claims will often be defined to be self-asserted.
        </t>

        <t>
          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.
        </t>

        <t>
          This document intentionally does not define "support" for a category,
          in order to leave the concept as general as possible.
          It is
          assumed that entity category definitions MAY define one or more category support URIs
          signifying particular definitions for "support" by peers as motivated by use
          cases arising from the definition of the category itself.
        </t>

        <t>
          A common case is expected to be the definition of a single category support URI
          whose value is identical to the category URI.
        </t>

        <t>
          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. It is for this reason that
          authorities defining entity categories support MAY employ some form of versioning.
          When versioning is used, each version of the category support
	        URI MUST be treated as a separate URI.
        </t>


        <t>
          No ordering relation is defined for entity category support attribute values.
          Entity category support attribute values MUST be treated as opaque strings
          for the purpose of comparison. In particular, if the specification defining the
          category support URIs relies on versioning, a relying
          party MUST NOT assume any particular ordering between different versions of
          the category support URI. Any order between versions MUST be spelled
          out in the specification.
        </t>

      </section>

      <section title="Entity Category Support Example">
        <figure>
          <artwork><![CDATA[<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>]]></artwork>
        </figure>
      </section>
    </section>

    <section anchor="IANA" title="IANA Considerations">
<t>This document has no IANA actions.
</t>
    </section>

    <section anchor="Security" title="Security Considerations">
      <t>
        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.
      </t>

      <t>
        Some of the elements in such a chain of trust might include:
        <list style="symbols">
          <t>
            The integrity of the metadata delivered to the relying party,
	    for
	    example, as
            assured by a digital signature.
          </t>
          <t>
            If the entity category attribute is carried within a signed assertion, the assertion
            itself must be evaluated.
          </t>
          <t>
            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.
          </t>
          <t>
            The policies and procedures implemented by agents along the publication path from
            the original metadata registrar. This may be determined by examination of
            the published procedures of each agent in turn or may be simplified if the
            entity metadata includes publication path metadata in mdrpi:PublicationPath
            elements as described in Section 2.3.1 of
            <xref target="SAML2MetadataRPI"/>.
          </t>
          <t>
            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 as described in
	    Section 2.1.1 of
            <xref target="SAML2MetadataRPI"/>.
          </t>
          <t>
            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.
          </t>
        </list>
      </t>
      <t>
        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.
      </t>

      <t>
        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.
      </t>

      <t>
        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 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 that were not already present if they have value to
        its intended audience.
      </t>

    </section>
  </middle>

  <back>
    <references title="Normative References">

<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.8174"?>



      <reference anchor="SAML2MetadataAttr"
        target="http://docs.oasis-open.org/security/saml/Post2.0/sstc-metadata-attr-cs-01.pdf">
        <front>
          <title>SAML V2.0 Metadata Extension for Entity Attributes Version 1.0</title>
          <author fullname="Scott Cantor" role="editor" initials="S." surname="Cantor"/>
          <date day="3" month="August" year="2009"/>
        </front>
      </reference>

      <reference anchor="SAML2MetadataRPI"
        target="http://docs.oasis-open.org/security/saml/Post2.0/saml-metadata-rpi/v1.0/cs01/saml-metadata-rpi-v1.0-cs01.pdf">
        <front>
          <title>SAML V2.0 Metadata Extensions for Registration and Publication Information Version 1.0</title>
          <author surname="La Joie" initials="C." role="editor" fullname="Chad La Joie"/>
          <date day="3" month="April" year="2012"/>
        </front>
      </reference>

    </references>

    <references title="Informative References">

<?rfc include="reference.RFC.4844"?>


      <reference anchor="REFEDS" target="http://www.refeds.org/">
        <front>
          <title>Research and Education FEDerations (REFEDS) Group</title>
          <author>
            <organization></organization>
          </author>
          <date/>
        </front>
      </reference>

      <reference anchor="REFEDS.agreement" target="https://refeds.org/about/refeds-participants-agreement">
        <front>
          <title>REFEDS Participant's Agreement</title>
          <author>
            <organization>Research and Education Federations</organization>
          </author>
          <date/>
        </front>
      </reference>

      <reference anchor="SAML2IDAssuranceProfile"
        target="http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-assurance-profile-cs-01.pdf">
        <front>
          <title>SAML V2.0 Identity Assurance Profiles Version 1.0</title>
          <author fullname='RL "Bob" Morgan' role="editor" initials="RL" surname="Morgan"/>
          <author fullname="Paul Madsen" role="editor" initials="P" surname="Madsen"/>
          <author fullname="Scott Cantor" role="editor" initials="S." surname="Cantor"/>
          <date day="5" month="November" year="2010"/>
        </front>
      </reference>

    </references>

    <section anchor="Acknowledgements" title="Acknowledgements" numbered="no">
      <t>
        This work has been a collaborative effort within the REFEDS and MACE-Dir
        communities. Special thanks to the following individuals (in no particular order):
        <list style="symbols">
          <t>RL 'Bob' Morgan</t>

          <t>Ken Klingenstein</t>

          <t>Keith Hazelton</t>

          <t>Steven Olshansky</t>

          <t>Mikael Linden</t>

          <t>Nicole Harris</t>

          <t>Tom Scavo</t>
        </list>
      </t>
    </section>


  </back>
</rfc>