OAuth Working Group N. Sakimura
Internet-Draft Nomura Research Institute
Intended status: Standards Track N. Matake
Expires: August 1, 2016 GREE, Inc.
SPR. Preibisch
CA Technologies
January 29, 2016

OAuth Response Metadata


This specification defines an extensible metadata that may be inserted into the OAuth 2.0 responses to assist the clients to process those responses. It is expressed either as a link header, or query parameters. It will allow the client to learn where the members in the response could be used, what is the characteristics of the payload is, how it should be processed, and so on. Since they are just additional response header/query parameters, any client that does not understand this extension should not break and work normally while supporting clients can utilize the metadata to take the advantage of the extension.

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 http://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 August 1, 2016.

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 Provisions Relating to IETF Documents (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 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

Although OAuth 2.0 [RFC6749] has been known for its REST friendliness, OAuth itself is not RESTful, as it heavily relies on out-of-band information to drive the interactions. This situation can be eased by hypertext-enabling the endpoint responses through the introduction of data structure that represents such hypertext and other metadata.

Hyper-text enabling the OAuth responses has many advantages. For example,

This specification defines methods to represent such metadata in the authorization and token responses.

1.1. Requirements Notation and Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD 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 "Access Token", "Authorization Code", "Authorization Endpoint", "Authorization Grant", "Authorization Server", "Client", "Client Authentication", "Protected Resource", "Refresh Token", and "Token Endpoint" defined by OAuth 2.0 [RFC6749].

2. Token Endpoint Response

Token Endpoints that implements this specification returns the following link relation (rel) and the corresponding URI value as defined in [RFC5988] in the Access Token Response defined in [RFC6749].

Resource URI. The value of this parameter is the URI of the Resource Endpoint that the Access Token is supposed to be used at. If this value is present, the cleint MUST NOT send the Access Token to any other URI.
Token Endpoint URI. The value of this parameter is the URI of the Token Endpoint that the Refresh Token can be sent to obtain a new Access Token. If this value is present, then the client MUST NOT send the refresh token to any other places.

Any other rels that are registered in Link Relation Type Registry defined in [RFC5988] registry can be used.

Following is an example of an HTTPS response.

HTTP/1.1 200 OK
Link: <https://example.com/userinfo>; rel="ruri",
 <https://example.com/payment-upon-trial-expiry>; rel="payments"
Content-Type: application/JSON; charset=utf-8


3. Authorization Response

While [RFC5988] defines a useful way of conveying link relations, it cannot be utilized for a redirect based communication such as the authorization response of OAuth 2.0. This section defines a way to return a limited set of those link relations as query parameters so that it can be conveyed over the redirection.

The authorization response of the implementation of this specification may return the following query parameter in the redirect URI.

Token Endpoint URI. The value of this parameter is the URI of the Token Endpoint that the Authorization Code can be sent to obtain the Access Token. If this parameter is specified, the client MUST check that the value of turi matches exactly with the pre-registered token endpoint URI of the Authorization Server that the session recoverd from the state variable points to. The cleint MUST NOT send the code to any other URIs than the value of this parameter.
Resource URI. The value of this parameter is the URI of the Resource Endpoint that the Access Token can be used at. If this parameter is specified, the cleint MUST NOT send the Access Token to any other URIs than the value of this parameter.

As long as the link relation type string does not collide with the underlying protocol parameters, they can also be specified as a query parameter. The value MUST be encoded in application/x-www-form-urlencoded.

The following is an example of such resopnse. Line breaks are for display purposes only.

HTTP/1.1 302 Found
Location: https://client.example.com/cb?code=SplxlOBeZQQYbYS6WxSbIA

4. IANA Considerations

4.1. Link Type Registration

Pursuant to [RFC5988], the following link type registrations [[will be]] registered by mail to link-relations@ietf.org.

5. Security Considerations

5.1. Authorization Response Query Parameter Tampering by a Bad User

The query response parameters may be tampered by the man-in-the-browser. It can also be tampered by a malicious user. In general, anything that comes via the browser/user-agent can be tainted and untrusted.

This specification mandates the turi check so that tamparing of turi by the malicious user will be detected. It does not mandate ruri check as the user can get the Access Token and send it to anywhere he wants anyways when it is returned to the browser.

However, other parameters are not protected. The Client MUST treat them tainted and implement its own check rules for each parameters.

To solve this "Tampering by bad user", either HMAC(concat(params)) need to be sent with them or have all of them inside the JWS.

6. Acknowledgements

Members of OAuth WG helped to form this specification. Notabely: Hannes tschofenig, John Bradley, Justin Richer, Kaoru Maeda, Masashi Kurabayashi, Michael B. Jones, Phil Hunt, William Dennis, James Manger, (add yourselves).

7. Document History








8. References

8.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, DOI 10.17487/RFC2616, June 1999.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, DOI 10.17487/RFC5988, October 2010.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012.

8.2. Informational References

[HAL] Kelly, M., "JSON Hypermedia API Language", February 2013.
[oauth-lrdd] Mills, W., "Link Type Registrations for OAuth 2", October 2012.
[RFC4627] Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, DOI 10.17487/RFC4627, July 2006.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M. and D. Orchard, "URI Template", RFC 6570, DOI 10.17487/RFC6570, March 2012.

Authors' Addresses

Nat Sakimura Nomura Research Institute EMail: sakimura@gmail.com
Nov Matake GREE, Inc. EMail: nov@matake.jp URI: http://matake.jp
Sascha Preibisch CA Technologies EMail: Sascha.Preibisch@gmail.com