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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: January 24, 2020                                Connect2id Ltd.
                                                            Jul 23, 2019


               JWT Response for OAuth Token Introspection
             draft-ietf-oauth-jwt-introspection-response-05

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
   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 January 24, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (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.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   3
   2.  Requesting a JWT Response . . . . . . . . . . . . . . . . . .   3
   3.  JWT Response  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Client Metadata . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Authorization Server Metadata . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     6.1.  Cross-JWT Confusion . . . . . . . . . . . . . . . . . . .   6
     6.2.  Token Data Leakage  . . . . . . . . . . . . . . . . . . .   7
     6.3.  Keeping Token Data Confidential from OAuth Clients  . . .   7
     6.4.  Logging and Audit of Introspection Activity . . . . . . .   7
     6.5.  Data Minimization . . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  OAuth Dynamic Client Registration Metadata Registration .   8
       8.1.1.  Registry Contents . . . . . . . . . . . . . . . . . .   8
     8.2.  OAuth Authorization Server Metadata Registration  . . . .   8
       8.2.1.  Registry Contents . . . . . . . . . . . . . . . . . .   8
     8.3.  OAuth Token Introspection Response  . . . . . . . . . . .   9
       8.3.1.  Registry Contents . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

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




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   the token introspection endpoint with the capability to return
   responses as JWTs.

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 BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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 claims defined in the "OAuth
   Token Introspection Response" registry established by [RFC7662].

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












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   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:

   {
     "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 other than
   "application/jwt", 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
   (see Section 6.2).








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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  OPTIONAL.  JWS [RFC7515] algorithm
           ("alg" value) as defined in JWA [RFC7518] for signing
           introspection responses.  If this is specified, the response
           will be signed using JWS and the configured algorithm.  The
           default, if omitted, is "RS256".

   introspection_encrypted_response_alg  OPTIONAL.  JWE [RFC7516]
           algorithm ("alg" value) as defined in JWA [RFC7518] for
           encrypting introspection responses.  If this is specified,
           the response will be encrypted using JWE and the configured
           algorithm.  The default, if omitted, is that no encryption is
           performed.  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].

   introspection_encrypted_response_enc  OPTIONAL.  JWE [RFC7516]
           algorithm ("enc" value) as defined in JWA [RFC7518] for
           authenticated encryption of introspection responses.  The
           default, if omitted, is "A128CBC-HS256".  Note: This
           parameter MUST NOT be specified without setting
           "introspection_encrypted_response_alg".

   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.




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   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) as defined in 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) as defined in 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) as defined in 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
   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 self-contained 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].








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6.2.  Token Data Leakage

   The authorization server MUST use Transport Layer Security (TLS) 1.2
   (or higher) per [RFC7525] in order to prevent token data leakage.

   To prevent introspection of leaked tokens and to present an
   additional security layer against token guessing attacks the
   authorization server may require all requests to the token
   introspection endpoint to be authenticated.  As an alternative or as
   an addition to the authentication, the intended recipients may be set
   up 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,
   for example, "application/json" instead of "application/jwt".  To
   prevent this attack the authorization server MUST NOT serve requests
   with content type other than "application/jwt" if the resource server
   is set up to receive encrypted responses (see also Section 3).

6.3.  Keeping Token Data Confidential from OAuth Clients

   Authorization servers with a policy that requires token data to be
   kept confidential from OAuth clients must require all requests to the
   token introspection endpoint to be authenticated.  As an alternative
   or as an addition to the authentication, the intended recipients may
   be set up for encrypted responses.

6.4.  Logging and Audit of Introspection Activity

   Authorization servers with a policy that requires token introspection
   activity to be logged and audited must require all requests to the
   token introspection endpoint to be authenticated.

6.5.  Data Minimization

   The authorisation server determines the token data a resource server
   is allowed to see based on the resource server's client_id and
   suitable token data, e.g. the scope value.

7.  Acknowledgements

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






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8.  IANA Considerations

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 values in
   the IANA "OAuth Authorization Server Metadata" registry
   [IANA.OAuth.Parameters] established by [RFC8414].

8.2.1.  Registry Contents

   o  Metadata Name: "introspection_signing_alg_values_supported"





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

   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

   This specification requests registration of the following claim
   values as defined in [OpenID.Core], Section 5.1, in the IANA "OAuth
   Token Introspection Response" registry.  [IANA.OAuth.Parameters]
   established by [RFC7662].

8.3.1.  Registry Contents

   o  Name: "name"

   o  Description: End-User's full name in displayable form including
      all name parts, possibly including titles and suffixes, ordered
      according to the End-User's locale and preferences.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "given_name"



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   o  Description: Given name(s) or first name(s) of the End-User.  Note
      that in some cultures, people can have multiple given names; all
      can be present, with the names being separated by space
      characters.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "family_name"

   o  Description: Surname(s) or last name(s) of the End-User.  Note
      that in some cultures, people can have multiple family names or no
      family name; all can be present, with the names being separated by
      space characters.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "middle_name"

   o  Description: Middle name(s) of the End-User.  Note that in some
      cultures, people can have multiple middle names; all can be
      present, with the names being separated by space characters.  Also
      note that in some cultures, middle names are not used.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "nickname"

   o  Description: Casual name of the End-User that may or may not be
      the same as the given_name.  For instance, a nickname value of
      Mike might be returned alongside a given_name value of Michael.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "preferred_username"

   o  Description: Shorthand name by which the End-User wishes to be
      referred to at the RP, such as janedoe or j.doe.  This value MAY
      be any valid JSON string including special characters such as @,
      /, or whitespace.




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   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "profile"

   o  Description:URL of the End-User's profile page.  The contents of
      this Web page SHOULD be about the End-User.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "picture"

   o  Description: URL of the End-User's profile picture.  This URL MUST
      refer to an image file (for example, a PNG, JPEG, or GIF image
      file), rather than to a Web page containing an image.  Note that
      this URL SHOULD specifically reference a profile photo of the End-
      User suitable for displaying when describing the End-User, rather
      than an arbitrary photo taken by the End-User.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "website"

   o  Description: URL of the End-User's Web page or blog.  This Web
      page SHOULD contain information published by the End-User or an
      organization that the End-User is affiliated with.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "email"

   o  Description: End-User's preferred e-mail address.  Its value MUST
      conform to the [RFC5322] "addr-spec" syntax.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "email_verified"





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   o  Description: True if the End-User's e-mail address has been
      verified; otherwise false.  When this Claim Value is true, this
      means that the OP took affirmative steps to ensure that this
      e-mail address was controlled by the End-User at the time the
      verification was performed.  The means by which an e-mail address
      is verified is context-specific, and dependent upon the trust
      framework or contractual agreements within which the parties are
      operating.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "gender"

   o  Description:End-User's gender.  Values defined by this
      specification are female and male.  Other values MAY be used when
      neither of the defined values are applicable.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "birthdate"

   o  Description:Time the End-User's information was last updated.  Its
      value is a JSON number representing the number of seconds from
      1970-01-01T0:0:0Z as measured in UTC until the date/time.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "zoneinfo"

   o  Description: String from zoneinfo [zoneinfo] time zone database
      representing the End-User's time zone.  For example, Europe/Paris
      or America/Los_Angeles.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "locale"

   o  Description: Time the End-User's information was last updated.
      Its value is a JSON number representing the number of seconds from
      1970-01-01T0:0:0Z as measured in UTC until the date/time.



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   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "phone_number"

   o  Description: End-User's preferred telephone number.  E.164 [E.164]
      is RECOMMENDED as the format of this Claim, for example, +1 (425)
      555-1212 or +56 (2) 687 2400.  If the phone number contains an
      extension, it is RECOMMENDED that the extension be represented
      using the [RFC3966] extension syntax, for example, +1 (604)
      555-1234;ext=5678.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "phone_number_verified"

   o  Description: True if the End-User's phone number has been
      verified; otherwise false.  When this Claim Value is true, this
      means that the OP took affirmative steps to ensure that this phone
      number was controlled by the End-User at the time the verification
      was performed.  The means by which a phone number is verified is
      context-specific, and dependent upon the trust framework or
      contractual agreements within which the parties are operating.
      When true, the phone_number Claim MUST be in E.164 format and any
      extensions MUST be represented in [RFC3966] format.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "address"

   o  Description: End-User's preferred postal address.  The value of
      the address member is a JSON [RFC7159] structure containing some
      or all of the members defined in [OpenID.Core], Section 5.1.1.

   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

   o  Name: "updated_at"

   o  Description: Time the End-User's information was last updated.
      Its value is a JSON number representing the number of seconds from
      1970-01-01T0:0:0Z as measured in UTC until the date/time.



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   o  Change Controller: IESG

   o  Specification Document(s):[OpenID.Core], Section 5.1

9.  References

9.1.  Normative References

   [I-D.ietf-oauth-jwt-bcp]
              Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
              Current Practices", draft-ietf-oauth-jwt-bcp-06 (work in
              progress), June 2019.

   [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-13 (work in progress), July 2019.

   [OpenID.Core]
              Sakimura, N., Bradley, J., Jones, M., Medeiros, B. D., and
              C. Mortimore, "OpenID Connect Core 1.0 incorporating
              errata set 1", Nov 2014,
              <http://openid.net/specs/openid-connect-core-1_0.html>.

   [OpenID.Registration]
              Sakimura, N., Bradley, J., and M. Jones, "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>.

   [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
              RFC 3966, DOI 10.17487/RFC3966, December 2004,
              <https://www.rfc-editor.org/info/rfc3966>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.





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   [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>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.






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Appendix A.  Document History

   [[ To be removed from the final specification ]]

   -05

   o  improved wording for TLS requirement

   o  added RFC 2119 boilerplate

   o  fixed and updated some references

   -04

   o  reworked definition of parameters in section 4

   o  added text on data minimization to security considerations section

   o  added statement regarding TLS to security considerations section

   -03

   o  added registration for OpenID Connect Standard Claims to OAuth
      Token Introspection Response registry

   -02

   o  updated references

   -01

   o  adapted wording to preclude any accept header except "application/
      jwt" if encrypted responses are required

   o  use registered alg value RS256 for default signing algorithm

   o  added text on claims in the token introspection response

   -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



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   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

   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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