| Network Working Group | L. Johansson |
| Internet-Draft | NORDUNet |
| Intended status: Informational | April 11, 2012 |
| Expires: October 11, 2012 |
An IANA registry for Level of Assurance (LoA) Profiles
draft-johansson-loa-registry-05
This document establishes an IANA registry for Level of Assurance (LoA) Profiles. The registry is intended to be used as an aid to discovering such LoA definitions in protocols that use an LoA concept, including SAML 2.0 and OpenID Connect.
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].
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This document establishes an IANA registry for Level of Assurance Profiles.
Quoting from sstc.saml-assurance-profile [OASIS.sstc.saml-assurance-profile] we find the following definition of the concept of 'level of assurance':
Many existing (and potential) SAML federation deployments have adopted a “levels of assurance” (or LOA) model for categorizing the wide variety of authentication methods into a small number of levels, typically based on some notion of the strength of the authentication. Federation members (service providers or “relying parties”) then decide which level of assurance is required to access specific protected resources, based on some assessment of “value” or “risk”.
Another definition of a 'level of assurance' is given in RFC4949 [RFC4949] which also identifies the roots of such profiles in the NIST special publication series, in particular SP 800-63 [SP63]. Level of Assurance profiles are used in various protocols, including the Security Assertion Markup Language (SAML) version 2.0 and OpenID Connect.
Several so called trust frameworks and identity federations now exist, some of which define one or more Level of Assurance (LoA). The purpose of this specification is to create an IANA registry where such LoA definitions can be discovered. While the quote above references SAML the notion of a "level of assurance" has gained wide-spread acceptance and should be treated as a protocol-independent concept. The proposed IANA registry attempts to reflects this.
Although the registry will contain URIs that reference SAML Authentication Context Profiles other protocols may use such URIs to identify levels of assurance definitions without relying on or transmitting their SAML XML definitions. Use of the registry by protocols other than SAML is encouraged.
For instance OpenID Connect defines the standard claim 'acr' as a identifier that may reference a SAML Authentication Context Class even though OpenID Connect is not itself based on XML or SAML.
Protocol designers who want to reference the registry should be aware that registered LoAs may depend on assumptions that do not carry over to all protocols and that such assumptions may vary among the protocols for which the LoAs were originally registered.
The name of the registry shall be "Level of Assurance Profile", in plural "Level of Assurance Profiles". The term LoA is an abbreviation of Level of Assurance.
The following information must be provided with each registration:
Note that it is possible for a single SAML Authentication Context Class to contain definitions of multiple URIs. In that case a separate registration is to be used for each URI. Both the name and the URI are to uniquely and unambigously identify the LoA. The name is meant to be used in protocols where URIs are not appropriate. In addition the requester is expected to provide basic contact information and the name of the organization on behalf of which the LoA definition is registered.
The Name is defined by the following ABNF (as defined in RFC5234 [RFC5234]):
label = ( ALPHA / DIGIT ) name = label 1*( label / "-" / "." / "_" )
The elements defined by the following ABNF productions represent a set of reserved values for the Name element and are not to be registered:
reserved = loa / al / num loa = ( "l" / "L" ) ( "o" / "O" ) ( "a" / "A") *DIGIT al = ( "a" / "A") ( "l" / "L") *DIGIT num = *DIGIT
The reason for excluding these productions is a desire to avoid a race to register overly generic LoA profiles under names like "AL1" or "LOA2".
SAML 2.0 Authentication Context Class Definition
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
targetNamespace="http://foo.example.com/assurance/loa-1"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="http://foo.example.com/assurance/loa-1"
finalDefault="extension"
blockDefault="substitution"
version="2.0">
<xs:redefine
schemaLocation="saml-schema-authn-context-loa-profile.xsd">
<xs:annotation>
<xs:documentation>
Class identifier:
http://foo.example.com/assurance/loa-1
Defines Level 1 of the Foo Assurance Framework
</xs:documentation>
</xs:annotation>
<xs:complexType name="GoverningAgreementRefType">
<xs:complexContent>
<xs:restriction base="GoverningAgreementRefType">
<xs:attribute name="governingAgreementRef"
type="xs:anyURI"
fixed="https://foo.example.com/assurance/"
use="required"/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:redefine>
</xs:schema>
The example is borrowed (slightly modified) from sstc.saml-assurance-profile [OASIS.sstc.saml-assurance-profile]. The example should not be registered.
The registry is to be operated under the "Expert Review" policy from RFC5226 [RFC5226] employing a pool of experts. IANA is kindly asked to do rough randomized load-balancing among the experts and also do an initial review of each submission to ensure that the name is and URI are unique within the registry. The review criteria are outlined below.
Registrations that reference multiple LoAs in a consistent set of policies - for instance when a trust framework defines multiple levels of assurance - the registered LoA Name and URIs should be consistently named so that they identified as belonging to the same set of registrations. For instance fruitLoA1,fruitLoA2 and fruitLoA3 is preferred over apple,pear and banana when these Names refer to a single set of policies defining 3 LoAs.
The expectation of the IANA LoA Registry is that it contain registrations of bona fide Level of Assurance Profiles while not presenting a very high bar for entry.
Expert reviewers are expected to verify that:
Note that multiple registrations may share a common Informational URL.
The reviewers should exclude registrations where the Name does not unambiguously identify the LoA definition or where the Name is a simple variation on one of the reserved names.
Expert reviewers are expected to allow registrations made in good faith that fulfil these requirements.
The intended use for this registry is to serve as a basis for discovery of LoA definitions that might for instance be used by protocol-specific (eg SAML 2.0 or OpenID Connect) management tools.
Consumers of the registry must not treat the registry as a complete list of all existing LoA definitions and should provide a way for the user to provide additional LoA definitions while ensuring that such additional LoA definitions do not duplicate or override entries in the registry.
The presence of an entry in the registry does not imply any semantic or quality beyond that which results from the review done by the expert reviewer as part of the registration process.
This document sets up a registry with IANA making the whole document a set of considerations for IANA.
The registry is not a federation or trust framework. Consumers of the registry are strongly advised to review the information about an LoA before relying on it.
RL 'Bob' Morgan, Scott Cantor, Lucy Lynch and John Bradley were involved in the initial discussions around this idea and contributed to the semantics of the registry. The various versions of the draft were socialized in the Kantara Federation Interoperability WG and in other parts of the identity community.
Note to the RFC editor: This section should be removed before publication.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC5234] | Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. |
| [OASIS.sstc.saml-assurance-profile] | Morgan, RL, Madsen, PM and S Cantor, "SAML V2.0 Identity Assurance Profiles Version 1.0", November 2010. |
| [RFC5226] | Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. |
| [SP63] | NIST, "Electronic Authentication Guideline, NIST Special Publication 800-63", June 2004. |
| [RFC4949] | Shirey, R., "Internet Security Glossary, Version 2", RFC 4949, August 2007. |