ALFA 2.0 - the Abbreviated Language for Authorization

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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶

This Internet-Draft will expire on 23 January 2025.¶

Copyright Notice

Copyright (c) 2024 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 Provisions Relating to IETF Documents (https://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 to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

Table of Contents

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.¶

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

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