Destination Claim for JSON Web Token
draft-campbell-oauth-dst4jwt-00

Abstract

The Destination Claim for JSON Web Token (JWT) provides a means of indicating the address to which the JWT is sent. The Claim can be used to preventing malicious forwarding or redirection of a JWT to unintended recipients.

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Table of Contents

• 1. Introduction
• 1.1. Requirements Notation and Conventions
• 1.2. Terminology
• 2. The Destination Claim
• 3. IANA Considerations
• 3.1. JSON Web Token Claim Registration
• 3.1.1. Registry Request Contents
• 4. Security Considerations
• 5. References
• 5.1. Normative References
• 5.2. Informative References
• Appendix A. Open Issues
• Appendix B. Document History
• Authors' Addresses

1. Introduction

JWT [I-D.ietf-oauth-json-web-token] is a compact, URL-safe means of representing claims to be transferred between two parties. Oftentimes an HTTP 302 redirect or an auto-submitted HTML form, using the user agent as a intermediary, is employed as the method of transfer. The Destination Claim provides a standard way for for the Issuer to indicate the address to which it instructed the user agent to deliver the JWT. The recipient of the JWT can detect and prevent malicious forwarding or redirection to unintended recipients by verifying that the address conveyed by the Destination Claim matches the actual location at which the JWT was received.

While the Destination Claim bears some seeming similarity to the Audience Claim already defined in JWT, the distinction is that the Audience identifies who the JWT is intended for while the Destination identifies where the JWT is sent.

1.1. Requirements Notation and Conventions

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 RFC 2119 [RFC2119].

1.2. Terminology

This specification uses the terms JSON Web Token (JWT), Issuer Claim, Claim Name, and Claim Value as defined in [I-D.ietf-oauth-json-web-token], and the term "user agent" as defined by RFC 7230 [RFC7230].

2. The Destination Claim

The Claim Name of the Destination Claim is dst and its Claim Value is a URI [RFC3986] indicating the address to which the JWT is sent. Use of this Claim is OPTIONAL but, if the Claim is present, the recipient MUST check that the URI identifies the location at which the JWT was received. If the JWT is received at a different location than the one conveyed by the value of the dst claim, then the JWT MUST be rejected.

3. IANA Considerations

3.1. JSON Web Token Claim Registration

This specification registers the Destination Claim defined herein in the IANA JSON Web Token Claims registry defined in [I-D.ietf-oauth-json-web-token].

3.1.1. Registry Request Contents

• Claim Name: dst
• Claim Description: Destination
• Change Controller: IESG
• Specification Document(s): Section 2 of this document

4. Security Considerations

The Destination Claim defined in Section 2 provides a means to assist in detecting and preventing malicious forwarding or redirection of a JWT to unintended recipients. If, for example, an Issuer can be tricked into sending a JWT to a malicious site (perhaps due to inadequate checking of the target URI combined with Cross-Site Request Forgery) the JWT would be unusable at the legitimate site because the dst would contain a URI of the malicious site.

5. References

5.1. Normative References

5.2. Informative References

Appendix A. Open Issues

• Is there compelling reason to allow the dst Claim to accommodate multiple values? A single value is sufficient for the cases envisioned and is certainly simpler.

Appendix B. Document History

[[ to be removed by the RFC Editor before publication as an RFC ]]

-00

• Gotta start somewhere...

Authors' Addresses