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Versions: (draft-lodderstedt-oauth-jwt-introspection-response) 00 01 02 03 04 05

Open Authentication Protocol                         T. Lodderstedt, Ed.
Internet-Draft                                                YES.com AG
Intended status: Standards Track                            V. Dzhuvinov
Expires: February 6, 2019                                Connect2id Ltd.
                                                         August 05, 2018


               JWT Response for OAuth Token Introspection
             draft-ietf-oauth-jwt-introspection-response-00

Abstract

   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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 February 6, 2019.

Copyright Notice

   Copyright (c) 2018 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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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requesting a JWT Response . . . . . . . . . . . . . . . . . .   3
   3.  JWT Response  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Client Metadata . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Authorization Server Metadata . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
     6.1.  Cross-JWT Confusion . . . . . . . . . . . . . . . . . . .   5
     6.2.  Token Data Leakage  . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  OAuth Dynamic Client Registration Metadata Registration .   7
       8.1.1.  Registry Contents . . . . . . . . . . . . . . . . . .   7
     8.2.  OAuth Authorization Server Metadata Registration  . . . .   7
       8.2.1.  Registry Contents . . . . . . . . . . . . . . . . . .   7
     8.3.  OAuth Token Introspection Response  . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   OAuth 2.0 Token Introspection [RFC7662] 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 [RFC7662], is a plain JSON object.  However, there are
   use cases where the resource server requires stronger assurance that
   the authorization server issued the access token, including cases
   where the authorization server assumes liability for the token's
   content.  An example is a resource server using verified person data
   to create certificates, which in turn are used to create qualified
   electronic signatures.

   In such use cases it may be useful or even required to return a
   signed JWT as the introspection response.  This specification extends
   the token introspection endpoint with the capability to return
   responses as JWTs.







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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
   Host: server.example.com
   Accept: application/jwt
   Content-Type: application/x-www-form-urlencoded

   token=2YotnFZFEjr1zCsicMWpAA

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 6.1).

   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

   eyJraWQiOiIxIiwiYWxnIjoiUlMyNTYifQ.eyJzdWIiOiJaNU8zdXBQQzg4UXJBa
   ngwMGRpcyIsImF1ZCI6Imh0dHBzOlwvXC9wcm90ZWN0ZWQuZXhhbXBsZS5uZXRcL
   3Jlc291cmNlIiwiZXh0ZW5zaW9uX2ZpZWxkIjoidHdlbnR5LXNldmVuIiwic2Nvc
   GUiOiJyZWFkIHdyaXRlIGRvbHBoaW4iLCJpc3MiOiJodHRwczpcL1wvc2VydmVyL
   mV4YW1wbGUuY29tXC8iLCJhY3RpdmUiOnRydWUsImV4cCI6MTQxOTM1NjIzOCwia
   WF0IjoxNDE5MzUwMjM4LCJjbGllbnRfaWQiOiJsMjM4ajMyM2RzLTIzaWo0Iiwid
   XNlcm5hbWUiOiJqZG9lIn0.HEQHf05vqVvWVnWuEjbzUnPz6JDQVR69QkxgzBNq5
   kk-sK54ieg1STazXGsdFAT8nUhiiV1f_Z4HOKNnBs8TLKaFXokhA0MqNBOYI--2u
   nVHDqI_RPmC3p0NmP02Xmv4hzxFmTmpgjSy3vpKQDihOjhwNBh7G81JNaJqjJQTR
   v_1dHUPJotQjMK3k8_5FyiO2p64Y2VyxyQn1VWVlgOHlJwhj6BaGHk4Qf5F8DHQZ
   1WCPg2p_-hwfINfXh1_buSjxyDRF4oe9pKy6ZB3ejh9qIMm-WrwltuU1uWMXxN6e
   S6tUtpKo8UCHBwLWCHmJN7KU6ZojmaISspdS23lELAlyw

   The example response contains the following JSON document:





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   {
     "sub": "Z5O3upPC88QrAjx00dis",
     "aud": "https://protected.example.net/resource",
     "scope": "read write dolphin",
     "iss": "https://server.example.com/",
     "active": true,
     "exp": 1419356238,
     "iat": 1419350238,
     "client_id": "l238j323ds-23ij4",
     "given_name": "John",
     "family_name":"Doe",
     "birthdate":"1982-02-01"
   }

   Depending on the specific resource server policy the JWT is either
   signed, or signed and encrypted.  If the JWT is signed and encrypted
   it MUST be a Nested JWT, as defined in JWT [RFC7519].

   Note: If the resource server policy requires a signed and encrypted
   response and the authorization server receives an unauthenticated
   request containing an Accept header with content type "application/
   json", it MUST refuse to serve the request and return an HTTP status
   code 400.  This is done to prevent downgrading attacks to obtain
   token data intended for release to legitimate recipients only (which
   possess the respective decryption key).

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, as defined by this draft.

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

   The following client metadata parameters are introduced by this
   specification:

   introspection_signed_response_alg  JWS [RFC7515] "alg" algorithm JWA
           [RFC7518] REQUIRED for signing introspection responses.  If
           this is specified, the response will be signed using JWS and
           the configured algorithm.  The default, if omitted, is RSA
           SHA-256.




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   introspection_encrypted_response_alg  JWE [RFC7516] "alg" algorithm
           JWA [RFC7518] 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 [RFC7519].  The default, if
           omitted, is that no encryption is performed.

   introspection_encrypted_response_enc  JWE [RFC7516] "enc" algorithm
           JWA [RFC7518] 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 2.0 Authorization Server Metadata [RFC8414]
   parameters.

   The following parameters are introduced by this specification:

   introspection_signing_alg_values_supported  OPTIONAL.  JSON array
           containing a list of the JWS [RFC7515] signing algorithms
           ("alg" values) JWA [RFC7518] supported by the introspection
           endpoint to sign the response.

   introspection_encryption_alg_values_supported  OPTIONAL.  JSON array
           containing a list of the JWE [RFC7516] encryption algorithms
           ("alg" values) JWA [RFC7518] supported by the introspection
           endpoint to encrypt the response.

   introspection_encryption_enc_values_supported  OPTIONAL.  JSON array
           containing a list of the JWE [RFC7516] encryption algorithms
           ("enc" values) JWA [RFC7518] supported by the introspection
           endpoint to encrypt the response.

6.  Security Considerations

6.1.  Cross-JWT Confusion

   JWT introspection responses and OpenID Connect ID Tokens are
   syntactically similar.  An attacker could therefore attempt to




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   impersonate an end-user at a OpenID Connect relying party by passing
   the JWT as an ID token.

   Such an attack can be prevented like any other token substitution
   attack.  The authorization server MUST include the claims "iss" and
   "aud" in each JWT introspection response, with the "iss" value set to
   the authorization server's issuer URL and the "aud" value set to the
   resource server's identifier.  This allows a correctly implemented
   OpenID Connect relying party to detect substitution by checking the
   "iss" and "aud" claims as described in Section 3.1.3.7. of
   [OpenID.Core].  Relying parties 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.  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 involving JWTs are discussed in
   [I-D.ietf-oauth-jwt-bcp].

6.2.  Token Data Leakage

   If the authorization server supports unauthenticated requests an
   attacker could potentially retrieve token data which must be kept
   confidential.  This attack can be prevented by either authenticating
   any request to the token introspection endpoint or by setting up the
   respective recipient for encrypted responses.

   In the latter case, confidentiality is ensured by the fact that only
   the legitimate recipient is able to decrypt the response.  An
   attacker could try to circumvent this measure by requesting a plain
   JSON response, using an Accept header with the content type set to
   "application/json" instead of "application/jwt".  To prevent this
   attack the authorization server MUST not serve requests with content
   type "application/json" if the resource server is set up to receive
   encrypted responses (see also Section 3).

7.  Acknowledgements

   We would like to thank Petteri Stenius, Neil Madden, Filip Skokan,
   and Tony Nadalin for their valuable feedback.

8.  IANA Considerations







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8.1.  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]:

8.1.1.  Registry Contents

   o  Client Metadata Name: "introspection_signed_response_alg"

   o  Client Metadata Description: String value indicating the client's
      desired introspection response signing algorithm.

   o  Change Controller: IESG

   o  Specification Document(s): Section 4 of [[ this specification ]]

   o  Client Metadata Name: "introspection_encrypted_response_alg"

   o  Client Metadata Description: String value specifying the desired
      introspection response encryption algorithm (alg value).

   o  Change Controller: IESG

   o  Specification Document(s): Section 4 of [[ this specification ]]

   o  Client Metadata Name: "introspection_encrypted_response_enc"

   o  Client Metadata Description: String value specifying the desired
      introspection response encryption algorithm (enc value).

   o  Change Controller: IESG

   o  Specification Document(s): Section 4 of [[ this specification ]]

8.2.  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].

8.2.1.  Registry Contents

   o  Metadata Name: "introspection_signing_alg_values_supported"

   o  Metadata Description: JSON array containing a list of algorithms
      supported by the authorization server for introspection response
      signing.



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   o  Change Controller: IESG

   o  Specification Document(s): Section 5 of [[ this specification ]]

   o  Metadata Name: "introspection_encryption_alg_values_supported"

   o  Metadata Description: JSON array containing a list of algorithms
      supported by the authorization server for introspection response
      encryption (alg value).

   o  Change Controller: IESG

   o  Specification Document(s): Section 5 of [[ this specification ]]

   o  Metadata Name: "introspection_encryption_enc_values_supported"

   o  Metadata Description: JSON array containing a list of algorithms
      supported by the authorization server for introspection response
      encryption (enc value).

   o  Change Controller: IESG

   o  Specification Document(s): Section 5 of [[ this specification ]]

8.3.  OAuth Token Introspection Response

   TBD: add all OpenID Connect standard claims.

9.  References

9.1.  Normative References

   [I-D.ietf-oauth-discovery]
              Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
              Authorization Server Metadata", draft-ietf-oauth-
              discovery-10 (work in progress), March 2018.

   [I-D.ietf-oauth-jwt-bcp]
              Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
              Current Practices", draft-ietf-oauth-jwt-bcp-03 (work in
              progress), May 2018.

   [I-D.ietf-oauth-security-topics]
              Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
              "OAuth 2.0 Security Best Current Practice", draft-ietf-
              oauth-security-topics-06 (work in progress), May 2018.





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   [OpenID.Core]
              NRI, Ping Identity, Microsoft, Google, and Salesforce,
              "OpenID Connect Core 1.0 incorporating errata set 1", Nov
              2014,
              <http://openid.net/specs/openid-connect-core-1_0.html>.

   [OpenID.Registration]
              NRI, Ping Identity, and Microsoft, "OpenID Connect Dynamic
              Client Registration 1.0 incorporating errata set 1", Nov
              2014, <https://openid.net/specs/
              openid-connect-registration-1_0.html>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, DOI 10.17487/RFC2246, January 1999,
              <https://www.rfc-editor.org/info/rfc2246>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <https://www.rfc-editor.org/info/rfc7516>.

   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <https://www.rfc-editor.org/info/rfc7518>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

   [RFC7591]  Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
              P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
              RFC 7591, DOI 10.17487/RFC7591, July 2015,
              <https://www.rfc-editor.org/info/rfc7591>.

   [RFC7662]  Richer, J., Ed., "OAuth 2.0 Token Introspection",
              RFC 7662, DOI 10.17487/RFC7662, October 2015,
              <https://www.rfc-editor.org/info/rfc7662>.






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   [RFC8414]  Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
              Authorization Server Metadata", RFC 8414,
              DOI 10.17487/RFC8414, June 2018,
              <https://www.rfc-editor.org/info/rfc8414>.

9.2.  Informative References

   [IANA.OAuth.Parameters]
              IANA, "OAuth Parameters",
              <http://www.iana.org/assignments/oauth-parameters>.

Appendix A.  Document History

   [[ To be removed from the final specification ]]

   -00

   o  initial version of the WG draft

   o  defined default signing algorithm

   o  changed behavior in case resource server is set up for encryption

   o  Added text on token data leakage prevention to the security
      considerations

   o  moved Security Considerations section forward

   WG draft

   -01

   o  fixed typos in client meta data field names

   o  added OAuth Server Metadata parameters to publish algorithms
      supported for signing and encrypting the introspection response

   o  added registration of new parameters for OAuth Server Metadata and
      Client Registration

   o  added explicit request for JWT introspection response

   o  made iss and aud claims mandatory in introspection response

   o  Stylistic and clarifying edits, updates references

   -00




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   o  initial version

Authors' Addresses

   Torsten Lodderstedt (editor)
   YES.com AG

   Email: torsten@lodderstedt.net


   Vladimir Dzhuvinov
   Connect2id Ltd.

   Email: vladimir@connect2id.com





































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