ALFA 2.0 - the Abbreviated Language for Authorization
draft-brossard-alfa-authz-00

Web Authorization Protocol                                   D. Brossard
Internet-Draft                                                Axiomatics
Intended status: Standards Track                               A. Clymer
Expires: 23 January 2025                            Rock Solid Knowledge
                                                           T. Dimitrakos
                                  University of Kent School of Computing
                                                            22 July 2024

         ALFA 2.0 - the Abbreviated Language for Authorization
                      draft-brossard-alfa-authz-00

Abstract

   The Abbreviated Language for Authorization 2.0 is a constrained
   policy language aimed at solving fine-grained authorization
   challenges.  This specification builds on top of [XACML] and replaces
   [ALFA] to provide a more complete and easier language to use.

   Use cases for ALFA 2.0 include the ability to express: - Role-based
   access control ([RBAC]), - Attribute-based access control ([ABAC]),
   and - Relationship-based access control ([ReBAC])

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   https://davidjbrossard.github.io/alfa-authorization-language/draft-
   brossard-alfa-authz.html.  Status information for this document may
   be found at https://datatracker.ietf.org/doc/draft-brossard-alfa-
   authz/.

   Discussion of this document takes place on the Web Authorization
   Protocol Working Group mailing list (mailto:oauth@ietf.org), which is
   archived at https://mailarchive.ietf.org/arch/browse/oauth/.
   Subscribe at https://www.ietf.org/mailman/listinfo/oauth/.

   Source for this draft and an issue tracker can be found at
   https://github.com/davidjbrossard/alfa-authorization-language.

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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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   While authentication has _largely_ been solved and standardized (see
   [OAUTH] and SAML as successful authentication standards), not as much
   can be said of authorization.  One of the oldest and more mature
   standards is [XACML], the eXtensible Access Control Markup Language
   established in 2001 under the helm of OASIS.  The latest version,
   XACML 3.0, was released in 2013.

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   Since, there has been little innovation in the authorization space.
   Two standards emerged:

   *  ALFA: Abbreviated Language for Authorization (ALFA) is a domain-
      specific language for a high-level description of XACML policies.
      It is designed with ease of use in mind, for use by XACML policy
      writers.  ALFA provides the means to present domain specific
      information, such as attribute identifiers, in compact form and
      lays down the basic principle to compile policies expressed in
      ALFA into XACML 3.0 policies.  ALFA does not bring new semantics
      to XACML.  Anything that can be expressed in ALFA must be
      expressible in XACML.  ALFA has been designed in such a way that
      lossless round-trip translations is possible.

   *  OPA: Open Policy Agent is an open source, general-purpose policy
      engine that unifies policy enforcement across the stack.  OPA
      provides a high-level declarative language that lets you specify
      policy as code and simple APIs to offload policy decision-making
      from your software.  [OPA]

   While OPA became part of CNCF, ALFA remained as a draft under OASIS.
   OPA's strength is also its drawback.  It's a fullblown Datalog-based
   programming language which can achieve anything: it's extremely
   broad.  As for ALFA, as mentioned above, it's true to XACML and aims
   to achieve lossless round-trip translations leading to unnecessary
   complications in ALFA's existing grammar.

   The aim of this standard is to provide a simple and constrained
   authorization language largely inspired by ALFA but not tied to XACML
   and not limited by the need to provide round-tripping.

2.  Conventions and Definitions

   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 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Security Considerations

   TODO Security

4.  IANA Considerations

   This document has no IANA actions.

5.  References

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5.1.  Normative References

   [ABAC]     Hu, V. and D. Ferraiolo, "Guide to Attribute Based Access
              Control (ABAC) Definition and Considerations - NIST
              Special Publication 800-162", January 2014,
              <https://doi.org/10.6028/NIST.SP.800-162>.

   [ALFA]     Giambiagi, P., Nair, S. K., and D. Brossard, "Abbreviated
              Language for Authorization Version 1.0", March 2015,
              <https://groups.oasis-
              open.org/higherlogic/ws/public/download/55228/alfa-for-
              xacml-v1.0-wd01.doc>.

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [XACML]    Rissanen, E., "eXtensible Access Control Markup Language
              (XACML) Version 3.0, OASIS Standard", January 2013,
              <https://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-
              spec-os-en.html>.

5.2.  Informative References

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

   [OPA]      Styra, "Open Policy Agent | Documentation", July 2024,
              <https://www.openpolicyagent.org/docs/latest/>.

   [RBAC]     Kuhn, R., Ferraiolo, D., and R. Sandhu, "The NIST Model
              for Role-Based Access Control: Towards a Unified
              Standard", July 2000,
              <https://doi.org/10.1145/344287.344301>.

   [ReBAC]    Gates, C., "Access Control Requirements for Web 2.0
              Security and Privacy", January 2007,
              <https://doi.org/10.1145/344287.344301>.

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Acknowledgments

   The authors would like to acknowledge the authors of the original
   version of ALFA namely Pablo Giambiagi and Dr. Srijith Nair.  The
   authors would also like to acknowledge Erik Rissanen, the then editor
   of the XACML Technical Committee.

Authors' Addresses

   David Brossard
   Axiomatics
   Canada
   Email: david.brossard@gmail.com

   Andrew Clymer
   Rock Solid Knowledge
   United Kingdom
   Email: andy@rocksolidknowledge.com

   Theodosios Dimitrakos
   University of Kent School of Computing
   Email: t.dimitrakos@kent.ac.uk

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