Open Authentication Protocol T. Lodderstedt, Ed.
Internet-Draft AG
Intended status: Standards Track V. Dzhuvinov
Expires: November 29, 2018 Connect2id Ltd.
May 28, 2018

JWT Response for OAuth Token Introspection


This draft proposes an additional JSON Web Token (JWT) based response for OAuth 2.0 Token Introspection.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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Table of Contents

1. Introduction

OAuth 2.0 Token Introspection specifies a method for a protected resource to query an OAuth 2.0 authorization server to determine the state of an access token and obtain data associated with the access token. This allows deployments to implement identifier-based access tokens in an interoperable way.

The introspection response as specified in OAuth 2.0 Token Introspection is a plain JSON object. However, there are use cases where the resource server requires stronger assurance that the authorisation server issued the access token, including cases where the authorisation server assumes liability for the token's content. An example is a resource server using verified person data to create qualified electronic signatures.

In such use cases, it would be useful to return a signed JWT as the introspection response. This specification extends the Token Introspection endpoint with the capability to return responses as JWTs.

2. Requesting a JWT Response

A resource server requests to receive a JWT introspection response by including an Accept header with content type "application/jwt" in the introspection request.

The following is a non-normative example request:

POST /introspect HTTP/1.1
Accept: application/jwt
Content-Type: application/x-www-form-urlencoded


3. JWT Response

The introspection endpoint responds with a JWT, setting the Content-Type header to "application/jwt".

This JWT MUST contain the claims iss and aud in order to prevent misuse of the JWT as ID or access token (see Section 8.1).

This JWT may furthermore contain all other claims described in Section 2.2. of [RFC7662].

The following is a non-normative example response (with line breaks for display purposes only):

HTTP/1.1 200 OK
Content-Type: application/jwt


The example response contains the following JSON document:

  "sub": "Z5O3upPC88QrAjx00dis",
  "aud": "",
  "scope": "read write dolphin",
  "iss": "",
  "active": true,
  "exp": 1419356238,
  "iat": 1419350238,
  "client_id": "l238j323ds-23ij4",
  "given_name": "John",

4. Client Metadata

The authorization server determines what algorithm to employ to secure the JWT for a particular introspection response. This decision can be based on registered metadata parameters for the resource server, supplied via dynamic client registration with the resource server posing as the client.

The parameter names follow the pattern established by OpenID Connect Dynamic Client Registration for configuring signing and encryption algorithms for JWT responses at the UserInfo endpoint.

The following client metadata parameters are introduced by this specification:

JWS alg algorithm JWA REQUIRED for signing introspection responses. If this is specified, the response will be JWT serialized, and signed using JWS. The default, if omitted, is for the introspection response to return the Claims as a UTF-8 encoded JSON object using the "application/json" content type, as defined in [RFC7662].
JWE alg algorithm JWA REQUIRED for encrypting introspection responses. If both signing and encryption are requested, the response will be signed then encrypted, with the result being a Nested JWT, as defined in JWT. The default, if omitted, is that no encryption is performed.
JWE enc algorithm JWA REQUIRED for encrypting introspection responses. If introspection_encrypted_response_alg is specified, the default for this value is A128CBC-HS256. When introspection_encrypted_response_enc is included, introspection_encrypted_response_alg MUST also be provided.

Resource servers may register their public encryption keys using the jwks_uri or jwks metadata parameters.

5. Authorization Server Metadata

Authorization servers SHOULD publish the supported algorithms for signing and encrypting the JWT of an introspection response by utilizing OAuth Authorization Server Metadata parameters.

The following parameters are introduced by this specification:

OPTIONAL. JSON array containing a list of the JWS signing algorithms (alg values) JWA supported by the Introspection Endpoint to sign the response.
OPTIONAL. JSON array containing a list of the JWE encryption algorithms (alg values) JWA supported by the Introspection Endpoint to encrypt the response.
OPTIONAL. JSON array containing a list of the JWE encryption algorithms (enc values) JWA supported by the Introspection Endpoint to encrypt the response.

6. Acknowledgements

We would like to thank Petteri Stenius and Neil Madden for their valuable feedback.

7. IANA Considerations

7.1. OAuth Dynamic Client Registration Metadata Registration

This specification requests registration of the following client metadata definitions in the IANA "OAuth Dynamic Client Registration Metadata" registry [IANA.OAuth.Parameters] established by [RFC7591]:

7.1.1. Registry Contents

7.2. OAuth Authorization Server Metadata Registration

This specification requests registration of the following value in the IANA "OAuth Authorization Server Metadata" registry [IANA.OAuth.Parameters] established by [I-D.ietf-oauth-discovery].

7.2.1. Registry Contents

7.3. OAuth Token Introspection Response

TBD: add all OpenID Connect standard claims.

8. Security Considerations

8.1. Cross-JWT Confusion

JWT introspection responses and OpenID Connect ID Tokens are syntactically more or less equivalent. An attacker could therefore try to misuse an JWT obtained from an introspection response to impersonate the user whose claims are included in this JWT at a OpenID Connect RP. Such an attack is treated and prevented like any other token substitution attack. The AS MUST include the claims iss and aud into every JWT introspection response. This allows every well behaving OpenID Connect RP to detect substitution by checking the iss and aud claims as described in Section of [OpenID.Core]. RPs should also use and check the nonce parameter and claim to prevent token and code replay.

Resource servers utilizing JWTs to represent structured access tokens could be susceptible to replay attacks as well. Resource servers should therefore apply proper counter measures against replay as described in [I-D.ietf-oauth-security-topics], section 2.2.

JWT Confusion and other attacks on JWTs are discussed in detail in [I-D.ietf-oauth-jwt-bcp].

9. References

9.1. Normative References

[I-D.ietf-oauth-discovery] Jones, M., Sakimura, N. and J. Bradley, "OAuth 2.0 Authorization Server Metadata", Internet-Draft draft-ietf-oauth-discovery-10, March 2018.
[I-D.ietf-oauth-jwt-bcp] Sheffer, Y., Hardt, D. and M. Jones, "JSON Web Token Best Current Practices", Internet-Draft draft-ietf-oauth-jwt-bcp-03, May 2018.
[I-D.ietf-oauth-security-topics] Lodderstedt, T., Bradley, J., Labunets, A. and D. Fett, "OAuth 2.0 Security Best Current Practice", Internet-Draft draft-ietf-oauth-security-topics-06, May 2018.
[OpenID.Core] NRI, Ping Identity, Microsoft, Google and Salesforce, "OpenID Connect Core 1.0 incorporating errata set 1", Nov 2014.
[OpenID.Registration] NRI, Ping Identity and Microsoft, "OpenID Connect Dynamic Client Registration 1.0 incorporating errata set 1", Nov 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, DOI 10.17487/RFC2246, January 1999.
[RFC7515] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, DOI 10.17487/RFC7518, May 2015.
[RFC7519] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015.
[RFC7591] Richer, J., Jones, M., Bradley, J., Machulak, M. and P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol", RFC 7591, DOI 10.17487/RFC7591, July 2015.
[RFC7662] Richer, J., "OAuth 2.0 Token Introspection", RFC 7662, DOI 10.17487/RFC7662, October 2015.

9.2. Informative References

[IANA.OAuth.Parameters] IANA, "OAuth Parameters"

Appendix A. Document History

[[ To be removed from the final specification ]]



Authors' Addresses

Torsten Lodderstedt (editor) AG EMail:
Vladimir Dzhuvinov Connect2id Ltd. EMail: