Internet DRAFT - draft-young-entity-category
draft-young-entity-category
Network Working Group I. Young, Ed.
Internet-Draft Independent
Intended status: Informational L. Johansson
Expires: August 4, 2018 SUNET
S. Cantor
Shibboleth Consortium
January 31, 2018
The Entity Category SAML Attribute Types
draft-young-entity-category-07
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.
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This Internet-Draft will expire on August 4, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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carefully, as they describe your rights and restrictions with respect
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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 . . . . . . . . . . . . . . . . . 6
4. Entity Category Support Attribute . . . . . . . . . . . . . . 6
4.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Semantics . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. Entity Category Support Example . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10
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-05 . . . . . . . . . . 11
B.2. Since draft-young-entity-category-04 . . . . . . . . . . 11
B.3. Since draft-young-entity-category-03 . . . . . . . . . . 11
B.4. Since draft-young-entity-category-02 . . . . . . . . . . 11
B.5. Since draft-young-entity-category-01 . . . . . . . . . . 12
B.6. Since draft-young-entity-category-00 . . . . . . . . . . 12
B.7. 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
therefore does not specify a controlled vocabulary for assigning
entity category values. Category URIs 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.
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 a fashion described by the category specification.
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 valid URIs. It is
RECOMMENDED that http:-scheme or https:-scheme URIs are used, and
further RECOMMENDED that an entity category URI resolves to a human-
readable document defining the category.
Authorities defining entity categories MUST produce a specification
of the entity category and SHOULD make arrangement for the entity
category URI to resolve to the specification in human readable form.
Authorities defining entity categories MAY use versioning of entity
category URIs where appropriate, in which case each version of the
specification of the entity category SHOULD clearly indicate the
latest version of the entity 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 in the case when the specification may be
updated.
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.
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.
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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:
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. It is for this reason that authorities defining
entity categories MAY employ some form of versioning for entity
category URI. When versioning is used each version of the entity
category MUST be treated as a separate URI.
No ordering relation is defined over entity category value URIs.
Entity category attribute value URIs MUST be treated as opaque
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strings for the purpose of comparison. In particular, if the
specification defining the entity category relies on versioning of
the entity category URI, a relying party MUST NOT assume any
particular ordering between different versions of the entity
category. Any order between versions MUST be spelled out in the
specification.
3.3. Entity Category Example
<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 authoritiy defining the entity
category and entity category support values MUST clearly describe the
relationship between (all versions of) the entity category URI and
(all versions of) the entity category support URIs as applicable in
the entity category specification.
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.
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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
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. It is for this reason that authorities defining entity
categories support MAY employ some form of versioning. When
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versioning is used each version of the entity category support URI
MUST be treated as a separate URI.
No ordering relation is defined over entity category URIs. Entity
category attribute support value URIs MUST be treated as opaque
strings for the purpose of comparison. In particular, if the
specification defining the entity category support values relies on
versioning, a relying party MUST NOT assume any particular ordering
between different versions of the entity category support URI. Any
order between versions MUST be spelled out in the specification.
4.3. Entity Category Support Example
<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:
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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
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
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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.
[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-05
Recommendation on versioning and language on requirements for entity
category specification.
B.2. Since draft-young-entity-category-04
No substantive changes.
B.3. 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.4. Since draft-young-entity-category-02
Fix link to the REFEDS Participant's Agreement [REFEDS.agreement].
Clarifications in response to IETF Gen-Art review:
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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
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.5. 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.6. Since draft-young-entity-category-00
Update affiliations for Leif Johansson and Scott Cantor.
Remove authors from acknowledgements.
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Reorganize some of the introductory boilerplate sections.
B.7. 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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