OAuth 2.0 Incremental Authorization
draft-ietf-oauth-incremental-authz-02

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OAuth Working Group                                           W. Denniss
Internet-Draft                                                    Google
Intended status: Standards Track                             May 3, 2019
Expires: November 4, 2019

                  OAuth 2.0 Incremental Authorization
                 draft-ietf-oauth-incremental-authz-02

Abstract

   OAuth 2.0 authorization requests that include every scope the client
   might ever need can result in over-scoped authorization and a sub-
   optimal end-user consent experience.  This specification enhances the
   OAuth 2.0 authorization protocol by adding incremental authorization,
   the ability to request specific authorization scopes as needed, when
   they're needed, removing the requirement to request every possible
   scope that might be needed upfront.

Status of This Memo

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   This Internet-Draft will expire on November 4, 2019.

Copyright Notice

   Copyright (c) 2019 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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   include Simplified BSD License text as described in Section 4.e of

Denniss                 Expires November 4, 2019                [Page 1]
Internet-Draft     OAuth 2.0 Incremental Authorization          May 2019

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Incremental Auth for Confidential Clients . . . . . . . . . .   3
   5.  Incremental Auth for Public Clients . . . . . . . . . . . . .   4
   6.  Usability Considerations  . . . . . . . . . . . . . . . . . .   4
     6.1.  Handling Denials  . . . . . . . . . . . . . . . . . . . .   4
   7.  Alternative Approaches  . . . . . . . . . . . . . . . . . . .   5
     7.1.  Alternative for Public Clients  . . . . . . . . . . . . .   5
     7.2.  Alternative for Confidential Clients  . . . . . . . . . .   5
   8.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   5
     8.1.  Requesting Authorization In Context . . . . . . . . . . .   5
     8.2.  Preventing Overbroad Authorization Requests . . . . . . .   6
     8.3.  Authorization Correlation . . . . . . . . . . . . . . . .   6
   9.  Discovery Metadata  . . . . . . . . . . . . . . . . . . . . .   6
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   7
     10.1.  Public Client Impersonation  . . . . . . . . . . . . . .   7
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  OAuth Parameters Registry  . . . . . . . . . . . . . . .   7
     11.2.  OAuth 2.0 Authorization Server Metadata  . . . . . . . .   8
   12. Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   8
   Appendix B.  Document History . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   OAuth 2.0 clients may offer multiple features that require user
   authorization, but commonly not every user will use each feature.
   Without incremental authentication, applications need to either
   request all the possible scopes they need upfront, potentially
   resulting in a bad user experience, or track each authorization grant
   separately, complicating development.

   The goal of incremental authorization is to allow clients to request
   just the scopes they need, when they need them, while allowing them
   to store a single authorization grant for the user that contains the
   sum of the scopes granted.  Thus, each new authorization request
   increments the scope of the authorization grant, without the client
   needing to track a separate authorization grant for each group of