OAuth 2.0 Authorization Server Issuer Identifier in Authorization Response
draft-meyerzuselhausen-oauth-iss-auth-resp-02

Document Type Active Internet-Draft (individual)
Authors Karsten zu Selhausen  , Daniel Fett 
Last updated 2020-11-17
Stream (None)
Intended RFC status (None)
Formats plain text html xml pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
Web Authorization Protocol                         K. Meyer zu Selhausen
Internet-Draft                                                 Hackmanit
Intended status: Standards Track                                 D. Fett
Expires: 21 May 2021                                             yes.com
                                                        17 November 2020

   OAuth 2.0 Authorization Server Issuer Identifier in Authorization
                                Response
             draft-meyerzuselhausen-oauth-iss-auth-resp-02

Abstract

   This document specifies a new parameter "iss" that is used to
   explicitly include the issuer identifier of the authorization server
   in the authorization response of an OAuth authorization flow.  If
   implemented correctly, the "iss" parameter serves as an effective
   countermeasure to "mix-up attacks".

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 21 May 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Meyer zu Selhausen & Fett  Expires 21 May 2021                  [Page 1]
Internet-Draft             oauth-iss-auth-resp             November 2020

   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 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.  Conventions and Terminology . . . . . . . . . . . . . . .   3
   2.  Response Parameter "iss"  . . . . . . . . . . . . . . . . . .   4
     2.1.  Example Authorization Response  . . . . . . . . . . . . .   4
     2.2.  Example Error Response  . . . . . . . . . . . . . . . . .   4
     2.3.  Providing the Issuer Identifier "iss" . . . . . . . . . .   4
     2.4.  Validation of the Issuer Identifier "iss" . . . . . . . .   5
   3.  Authorization Server Metadata . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  OAuth Authorization Server Metadata . . . . . . . . . . .   8
     5.2.  OAuth Parameters Registration . . . . . . . . . . . . . .   8
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   8.  Informative References  . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The OAuth authorization framework [RFC6749] allows clients to
   interact with multiple independent authorization servers under the
   control of separate entities.  Some OAuth grant types utilize the
   resource owner's user-agent to deliver the authorization server's
   response to the OAuth client.  One example of this pattern is the
   authorization response of the authorization code grant.

   The authorization response as specified in Section 4.1.2. of
   [RFC6479] does not contain any information about the identity of the
   authorization server which issued the response.  Therefore, clients
   receiving a response from the resource owner's user-agent cannot be
   sure who initially issued the response.  The lack of certainty about
   the origin of the response benefits a class of attacks called "mix-up
   attacks".

Meyer zu Selhausen & Fett  Expires 21 May 2021                  [Page 2]
Internet-Draft             oauth-iss-auth-resp             November 2020

   This type of attack is a threat to all OAuth clients that interact
   with multiple authorization servers when at least one of these
   authorization servers is under an attacker's control.  There are
   multiple ways in which an attacker can gain control over an
   authorization server supported by the client: For example, an
Show full document text