Authentication Method Reference Values
draft-ietf-oauth-amr-values-01

OAuth Working Group                                             M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                                 P. Hunt
Expires: January 8, 2017                                          Oracle
                                                              A. Nadalin
                                                               Microsoft
                                                            July 7, 2016

                 Authentication Method Reference Values
                     draft-ietf-oauth-amr-values-01

Abstract

   The "amr" (Authentication Methods References) claim is defined and
   registered in the IANA "JSON Web Token Claims" registry but no
   standard Authentication Method Reference values are currently
   defined.  This specification establishes a registry for
   Authentication Method Reference values and defines an initial set of
   Authentication Method Reference values.

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
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   This Internet-Draft will expire on January 8, 2017.

Copyright Notice

   Copyright (c) 2016 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect

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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Authentication Method Reference Values  . . . . . . . . . . .   3
   3.  Relationship to "acr" (Authentication Context Class
       Reference)  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Authentication Method Reference Values Registry . . . . .   6
       6.1.1.  Registration Template . . . . . . . . . . . . . . . .   7
       6.1.2.  Initial Registry Contents . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  11
   Appendix B.  Document History . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The "amr" (Authentication Methods References) claim is defined and
   registered in the IANA "JSON Web Token Claims" registry
   [IANA.JWT.Claims] but no standard Authentication Method Reference
   values are currently defined.  This specification establishes a
   registry for Authentication Method Reference values and defines an
   initial set of Authentication Method Reference values.

   The set of "amr" values defined by this specification is not intended
   to be an exhaustive set covering all use cases.  Additional values
   can and will be added to the registry by other specifications.
   Rather, the values defined herein are an intentionally small set that
   are already actually being used in practice.

   For context, while the claim values registered pertain to
   authentication, note that OAuth 2.0 [RFC6749] is designed for
   resource authorization and cannot be used for authentication without
   employing appropriate extensions, such as those defined by OpenID
   Connect Core 1.0 [OpenID.Core].  The existence of the "amr" claim and
   values for it should not be taken as encouragement to try to use

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   OAuth 2.0 for authentication without employing extensions enabling
   secure authentication to be performed.

   When used with OpenID Connect, if the identity provider supplies an
   "amr" claim in the ID Token resulting from a successful
   authentication, the relying party can inspect the values returned and
   thereby learn details about how the authentication was performed.
   For instance, the relying party might learn that only a password was
   used or it might learn that iris recognition was used in combination
   with a hardware-secured key.  Whether "amr" values are provided and
   which values are understood by what parties are both beyond the scope
   of this specification.  The OpenID Connect MODRNA Authentication
   Profile 1.0 [OpenID.MODRNA] is one example of an application context
   that uses "amr" values defined by this specification.

1.1.  Requirements Notation and Conventions

   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 RFC
   2119 [RFC2119].

1.2.  Terminology

   This specification uses the terms defined by JSON Web Token (JWT)
   [JWT] and OpenID Connect Core 1.0 [OpenID.Core].

2.  Authentication Method Reference Values

   The "amr" (Authentication Methods References) claim is defined by the
   OpenID Connect Core 1.0 specification [OpenID.Core] as follows:

   amr
      OPTIONAL.  Authentication Methods References.  JSON array of
      strings that are identifiers for authentication methods used in
      the authentication.  For instance, values might indicate that both
      password and OTP authentication methods were used.  The definition
      of particular values to be used in the "amr" Claim is beyond the
      scope of this specification.  Parties using this claim will need
      to agree upon the meanings of the values used, which may be
      context-specific.  The "amr" value is an array of case sensitive
      strings.

   However, OpenID Connect does not specify any particular
   Authentication Method Reference values to be used in the "amr" claim.
   The following is a list of Authentication Method Reference values
   defined by this specification:

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   face
      Facial recognition

   fpt
      Fingerprint biometric

   geo
      Use of geolocation information

   hwk
      Proof-of-possession (PoP) of a hardware-secured key.  See
      Appendix C of [RFC4211] for a discussion on PoP.

   iris
      Iris scan biometric

   kba
      Knowledge-based authentication [NIST.800-63-2]

   mca
      Multiple-channel authentication.  The authentication involves
      communication over more than one distinct channel.

   mfa
      Multiple-factor authentication [NIST.800-63-2].  When this is
      present, specific authentication methods used may also be
      included.

   otp
      One-time password.  One-time password specifications that this
      authentication method applies to include [RFC4226] and [RFC6238].

   pin
      Personal Identification Number or pattern (not restricted to
      containing only numbers) that a user enters to unlock a key on the
      device.  This mechanism SHOULD have a way to deter an attacker
      from obtaining the PIN by trying repeated guesses.

   pwd
      Password-based authentication

   rba
      Risk-based authentication [JECM]

   retina
      Retina scan biometric

   sc

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      Smart card

   sms
      Confirmation using SMS message to the user at a registered number

   swk
      Proof-of-possession (PoP) of a software-secured key.  See
      Appendix C of [RFC4211] for a discussion on PoP.

   tel
      Confirmation by telephone call to the user at a registered number

   user
      User presence test

   vbm
      Voice biometric

   wia
      Windows integrated authentication, as described in [MSDN]

3.  Relationship to "acr" (Authentication Context Class Reference)

   The "acr" (Authentication Context Class Reference) claim and
   "acr_values" request parameter are related to the "amr"
   (Authentication Methods References) claim, but with important
   differences.  An Authentication Context Class specifies a set of
   business rules that authentications are being requested to satisfy.
   These rules can often be satisfied by using a number of different
   specific authentication methods, either singly or in combination.
   Interactions using "acr_values" request that the specified
   Authentication Context Classes be used and that the result should
   contain an "acr" claim saying which Authentication Context Class was
   satisfied.  The "acr" claim in the reply states that the business
   rules for the class were satisfied -- not how they were satisfied.

   In contrast, interactions using the "amr" claim make statements about
   the particular authentication methods that were used.  This tends to
   be more brittle than using "acr", since the authentication methods
   that may be appropriate for a given authentication will vary over
   time, both because of the evolution of attacks on existing methods
   and the deployment of new authentication methods.

4.  Privacy Considerations

   The list of "amr" claim values returned in an ID Token reveals
   information about the way that the end-user authenticated to the

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   identity provider.  In some cases, this information may have privacy
   implications.

5.  Security Considerations

   The security considerations in OpenID Connect Core 1.0 [OpenID.Core],
   OAuth 2.0 [RFC6749], and the OAuth 2.0 Threat Model [RFC6819] apply
   to this specification.

   As described in Section 3, taking a dependence upon particular
   authentication methods may result in brittle systems, since the
   authentication methods that may be appropriate for a given
   authentication will vary over time.

6.  IANA Considerations

6.1.  Authentication Method Reference Values Registry

   This specification establishes the IANA "Authentication Method
   Reference Values" registry for "amr" claim array element values.  The
   registry records the Authentication Method Reference value and a
   reference to the specification that defines it.  This specification
   registers the Authentication Method Reference values defined in
   Section 2.

   Values are registered on an Expert Review [RFC5226] basis after a
   three-week review period on the jwt-reg-review@ietf.org mailing list,
   on the advice of one or more Designated Experts.  To increase
   potential interoperability, the experts are requested to encourage
   registrants to provide the location of a publicly-accessible
   specification defining the values being registered, so that their
   intended usage can be more easily understood.

   Registration requests sent to the mailing list for review should use
   an appropriate subject (e.g., "Request to register Authentication
   Method Reference value: otp").

   Within the review period, the Designated Experts will either approve
   or deny the registration request, communicating this decision to the
   review list and IANA.  Denials should include an explanation and, if
   applicable, suggestions as to how to make the request successful.
   Registration requests that are undetermined for a period longer than
   21 days can be brought to the IESG's attention (using the
   iesg@ietf.org mailing list) for resolution.

   Criteria that should be applied by the Designated Experts includes
   determining whether the proposed registration duplicates existing
   functionality, whether it is likely to be of general applicability or

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   whether it is useful only for a single application, whether the value
   is actually being used, and whether the registration description is
   clear.

   IANA must only accept registry updates from the Designated Experts
   and should direct all requests for registration to the review mailing
   list.

   It is suggested that the same Designated Experts evaluate these
   registration requests as those who evaluate registration requests for
   the IANA "JSON Web Token Claims" registry [IANA.JWT.Claims].

6.1.1.  Registration Template

   Authentication Method Reference Name:
      The name requested (e.g., "otp").  Because a core goal of this
      specification is for the resulting representations to be compact,
      it is RECOMMENDED that the name be short -- that is, not to exceed
      8 characters without a compelling reason to do so.  This name is
      case sensitive.  Names may not match other registered names in a
      case-insensitive manner unless the Designated Experts state that
      there is a compelling reason to allow an exception.

   Authentication Method Reference Description:
      Brief description of the Authentication Method Reference (e.g.,
      "One-time password").

   Change Controller:
      For Standards Track RFCs, state "IESG".  For others, give the name
      of the responsible party.  Other details (e.g., postal address,
      email address, home page URI) may also be included.

   Specification Document(s):
      Reference to the document or documents that specify the parameter,
      preferably including URIs that can be used to retrieve copies of
      the documents.  An indication of the relevant sections may also be
      included but is not required.

6.1.2.  Initial Registry Contents

   o  Authentication Method Reference Name: "face"
   o  Authentication Method Reference Description: Facial recognition
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "fpt"
   o  Authentication Method Reference Description: Fingerprint biometric
   o  Change Controller: IESG

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   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "geo"
   o  Authentication Method Reference Description: Geolocation
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "hwk"
   o  Authentication Method Reference Description: Proof-of-possession
      of a hardware-secured key
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "iris"
   o  Authentication Method Reference Description: Iris scan biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "kba"
   o  Authentication Method Reference Description: Knowledge-based
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "mca"
   o  Authentication Method Reference Description: Multiple-channel
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "mfa"
   o  Authentication Method Reference Description: Multiple-factor
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "otp"
   o  Authentication Method Reference Description: One-time password
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "pin"
   o  Authentication Method Reference Description: Personal
      Identification Number or pattern
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "pwd"

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   o  Authentication Method Reference Description: Password-based
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "rba"
   o  Authentication Method Reference Description: Risk-based
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "retina"
   o  Authentication Method Reference Description: Retina scan biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "sc"
   o  Authentication Method Reference Description: Smart card
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "sms"
   o  Authentication Method Reference Description: Confirmation using
      SMS
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "swk"
   o  Authentication Method Reference Description: Proof-of-possession
      of a software-secured key
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "tel"
   o  Authentication Method Reference Description: Confirmation by
      telephone call
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "user"
   o  Authentication Method Reference Description: User presence test
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "vbm"
   o  Authentication Method Reference Description: Voice biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

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   o  Authentication Method Reference Name: "wia"
   o  Authentication Method Reference Description: Windows integrated
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

7.  References

7.1.  Normative References

   [IANA.JWT.Claims]
              IANA, "JSON Web Token Claims",
              <http://www.iana.org/assignments/jwt>.

   [JECM]     Williamson, G., "Enhanced Authentication In Online
              Banking", Journal of Economic Crime Management 4.2: 18-19,
              2006,
              <http://utica.edu/academic/institutes/ecii/publications/
              articles/51D6D996-90F2-F468-AC09C4E8071575AE.pdf>.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, May 2015,
              <http://www.rfc-editor.org/info/rfc7519>.

   [MSDN]     Microsoft, "Integrated Windows Authentication with
              Negotiate", September 2011,
              <http://blogs.msdn.com/b/benjaminperkins/
              archive/2011/09/14/iis-integrated-windows-authentication-
              with-negotiate.aspx>.

   [NIST.800-63-2]
              National Institute of Standards and Technology (NIST),
              "Electronic Authentication Guideline", NIST Special
              Publication 800-63-2, August 2013,
              <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/
              NIST.SP.800-63-2.pdf>.

   [OpenID.Core]
              Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
              C. Mortimore, "OpenID Connect Core 1.0", November 2014,
              <http://openid.net/specs/openid-connect-core-1_0.html>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

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   [RFC4211]  Schaad, J., "Internet X.509 Public Key Infrastructure
              Certificate Request Message Format (CRMF)", RFC 4211,
              DOI 10.17487/RFC4211, September 2005,
              <http://www.rfc-editor.org/info/rfc4211>.

   [RFC4226]  M'Raihi, D., Bellare, M., Hoornaert, F., Naccache, D., and
              O. Ranen, "HOTP: An HMAC-Based One-Time Password
              Algorithm", RFC 4226, DOI 10.17487/RFC4226, December 2005,
              <http://www.rfc-editor.org/info/rfc4226>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6238]  M'Raihi, D., Machani, S., Pei, M., and J. Rydell, "TOTP:
              Time-Based One-Time Password Algorithm", RFC 6238,
              DOI 10.17487/RFC6238, May 2011,
              <http://www.rfc-editor.org/info/rfc6238>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <http://www.rfc-editor.org/info/rfc6749>.

7.2.  Informative References

   [OpenID.MODRNA]
              Connotte, J. and J. Bradley, "OpenID Connect MODRNA
              Authentication Profile 1.0", February 2016,
              <https://bitbucket.org/openid/mobile/raw/default/draft-
              mobile-authentication-01.txt>.

   [RFC6819]  Lodderstedt, T., Ed., McGloin, M., and P. Hunt, "OAuth 2.0
              Threat Model and Security Considerations", RFC 6819,
              DOI 10.17487/RFC6819, January 2013,
              <http://www.rfc-editor.org/info/rfc6819>.

Appendix A.  Acknowledgements

   Caleb Baker participated in specifying the original set of "amr"
   values.  John Bradley, Brian Campbell, William Denniss, James Manger,
   Nat Sakimura, and Mike Schwartz provided reviews of the
   specification.

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Appendix B.  Document History

   [[ to be removed by the RFC editor before publication as an RFC ]]

   -01

   o  Distinguished between retina and iris biometrics.
   o  Expanded the introduction to provide additional context to
      readers.
   o  Referenced the OpenID Connect MODRNA Authentication Profile 1.0
      specification, which uses "amr" values defined by this
      specification

   -00

   o  Created the initial working group draft from draft-jones-oauth-
      amr-values-05 with no normative changes.

Authors' Addresses

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/

   Phil Hunt
   Oracle

   Email: phil.hunt@yahoo.com

   Anthony Nadalin
   Microsoft

   Email: tonynad@microsoft.com

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