OAuth Working Group                                           M.B. Jones
Internet-Draft                                    Self-Issued Consulting
Obsoletes: 7523 (if approved)                                B. Campbell
Updates: 7521, 7522, 9101, 9126 (if approved)              Ping Identity
Intended status: Standards Track                            C. Mortimore
Expires: 31 July 2025                                             Disney
                                                         27 January 2025


  JSON Web Token (JWT) Profile for OAuth 2.0 Client Authentication and
                          Authorization Grants
                    draft-jones-oauth-rfc7523bis-00

Abstract

   This specification defines the use of a JSON Web Token (JWT) Bearer
   Token as a means for requesting an OAuth 2.0 access token as well as
   for client authentication.

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 31 July 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.











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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  HTTP Parameter Bindings for Transporting Assertions . . . . .   4
     2.1.  Using JWTs as Authorization Grants  . . . . . . . . . . .   5
     2.2.  Using JWTs for Client Authentication  . . . . . . . . . .   5
   3.  JWT Format and Processing Requirements  . . . . . . . . . . .   6
     3.1.  Authorization Grant Processing  . . . . . . . . . . . . .   8
     3.2.  Client Authentication Processing  . . . . . . . . . . . .   8
   4.  Authorization Grant Example . . . . . . . . . . . . . . . . .   9
   5.  Interoperability Considerations . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Media Type Registration . . . . . . . . . . . . . . . . .  11
       8.1.1.  Registry Contents . . . . . . . . . . . . . . . . . .  11
   9.  Updates to RFC 7521 . . . . . . . . . . . . . . . . . . . . .  12
   10. Updates to RFC 7522 . . . . . . . . . . . . . . . . . . . . .  13
   11. Updates to RFC 9101 . . . . . . . . . . . . . . . . . . . . .  15
   12. Updates to RFC 9126 . . . . . . . . . . . . . . . . . . . . .  16
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     13.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  19
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   JSON Web Token (JWT) [JWT] is a JSON-based [RFC8259] security token
   encoding that enables identity and security information to be shared
   across security domains.  A security token is generally issued by an
   Identity Provider and consumed by a Relying Party that relies on its
   content to identify the token's subject for security-related
   purposes.





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   The OAuth 2.0 Authorization Framework [RFC6749] provides a method for
   making authenticated HTTP requests to a resource using an access
   token.  Access tokens are issued to third-party clients by an
   authorization server (AS) with the (sometimes implicit) approval of
   the resource owner.  In OAuth, an authorization grant is an abstract
   term used to describe intermediate credentials that represent the
   resource owner authorization.  An authorization grant is used by the
   client to obtain an access token.  Several authorization grant types
   are defined to support a wide range of client types and user
   experiences.  OAuth also allows for the definition of new extension
   grant types to support additional clients or to provide a bridge
   between OAuth and other trust frameworks.  Finally, OAuth allows the
   definition of additional authentication mechanisms to be used by
   clients when interacting with the authorization server.

   "Assertion Framework for OAuth 2.0 Client Authentication and
   Authorization Grants" [RFC7521] is an abstract extension to OAuth 2.0
   that provides a general framework for the use of assertions (a.k.a.
   security tokens) as client credentials and/or authorization grants
   with OAuth 2.0.  This specification profiles the OAuth Assertion
   Framework [RFC7521] to define an extension grant type that uses a JWT
   Bearer Token to request an OAuth 2.0 access token as well as for use
   as client credentials.  The format and processing rules for the JWT
   defined in this specification are intentionally similar, though not
   identical, to those in the closely related specification "Security
   Assertion Markup Language (SAML) 2.0 Profile for OAuth 2.0 Client
   Authentication and Authorization Grants" [RFC7522].  The differences
   arise where the structure and semantics of JWTs differ from SAML
   Assertions.  JWTs, for example, have no direct equivalent to the
   <SubjectConfirmation> or <AuthnStatement> elements of SAML
   Assertions.




















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   This document defines how a JWT Bearer Token can be used to request
   an access token when a client wishes to utilize an existing trust
   relationship, expressed through the semantics of the JWT, without a
   direct user-approval step at the authorization server.  It also
   defines how a JWT can be used as a client authentication mechanism.
   The use of a security token for client authentication is orthogonal
   to and separable from using a security token as an authorization
   grant.  They can be used either in combination or separately.  Client
   authentication using a JWT is nothing more than an alternative way
   for a client to authenticate to the token endpoint or other endpoints
   such as the pushed authorization endpoint [RFC9126] and must be used
   in conjunction with some grant type to form a complete and meaningful
   protocol request.  JWT authorization grants may be used with or
   without client authentication or identification.  Whether or not
   client authentication is needed in conjunction with a JWT
   authorization grant, as well as the supported types of client
   authentication, are policy decisions at the discretion of the
   authorization server.

   The process by which the client obtains the JWT, prior to exchanging
   it with the authorization server or using it for client
   authentication, is out of scope.

1.1.  Notational 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.

   Unless otherwise noted, all the protocol parameter names and values
   are case sensitive.

1.2.  Terminology

   All terms are as defined in the following specifications: "The OAuth
   2.0 Authorization Framework" [RFC6749], the OAuth Assertion Framework
   [RFC7521], and "JSON Web Token (JWT)" [JWT].

2.  HTTP Parameter Bindings for Transporting Assertions

   The OAuth Assertion Framework [RFC7521] defines generic HTTP
   parameters for transporting assertions (a.k.a. security tokens)
   during interactions with a token endpoint.  This section defines
   specific parameters and treatments of those parameters for use with
   JWT Bearer Tokens.




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2.1.  Using JWTs as Authorization Grants

   To use a Bearer JWT as an authorization grant, the client uses an
   access token request as defined in Section 4 of the OAuth Assertion
   Framework [RFC7521] with the following specific parameter values and
   encodings.

   The value of the grant_type is urn:ietf:params:oauth:grant-type:jwt-
   bearer.

   The value of the assertion parameter MUST contain a single JWT.

   The scope parameter may be used, as defined in the OAuth Assertion
   Framework [RFC7521], to indicate the requested scope.

   Authentication of the client is optional, as described in
   Section 3.2.1 of OAuth 2.0 [RFC6749] and consequently, the client_id
   is only needed when a form of client authentication that relies on
   the parameter is used.

   The following example demonstrates an access token request with a JWT
   as an authorization grant (with extra line breaks for display
   purposes only):

     POST /token.oauth2 HTTP/1.1
     Host: as.example.com
     Content-Type: application/x-www-form-urlencoded

     grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
     &assertion=eyJ0eXAiOiJhdXRob3JpemF0aW9uLWdyYW50K2p3dCIsImFsZyI6Ik
       VTMjU2Iiwia2lkIjoiMTYifQ.
     eyJhdWQiOiJodHRwczovLw[...omitted for brevity...].
     J9l-ZhwP[...omitted for brevity...]

2.2.  Using JWTs for Client Authentication

   To use a JWT Bearer Token for client authentication, the client uses
   the following parameter values and encodings.

   The value of the client_assertion_type is
   urn:ietf:params:oauth:client-assertion-type:jwt-bearer.

   The value of the client_assertion parameter contains a single JWT.
   It MUST NOT contain more than one JWT.

   The following example demonstrates client authentication using a JWT
   during the presentation of an authorization code grant in an access
   token request (with extra line breaks for display purposes only):



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     POST /token.oauth2 HTTP/1.1
     Host: as.example.com
     Content-Type: application/x-www-form-urlencoded

     grant_type=authorization_code&
     code=n0esc3NRze7LTCu7iYzS6a5acc3f0ogp4&
     client_assertion_type=urn%3Aietf%3Aparams%3Aoauth%3A
     client-assertion-type%3Ajwt-bearer&
     client_assertion=eyJ0eXAiOiJjbGllbnQtYXV0aGVudGljYXRpb24rand0Iiwi
       YWxnIjoiUlMyNTYiLCJraWQiOiIyMiJ9.
     eyJhdWQiOiJodHRwczovLw[...omitted for brevity...].
     cC4hiUPo[...omitted for brevity...]

3.  JWT Format and Processing Requirements

   In order to issue an access token response as described in OAuth 2.0
   [RFC6749] or to rely on a JWT for client authentication, the
   authorization server MUST validate the JWT according to the criteria
   below.  Application of additional restrictions and policy are at the
   discretion of the authorization server.

   1.   The JWT MUST be explicitly typed, as defined in Section 3.11 of
        [RFC8725].  The typ header parameter values that MUST be used
        are defined in Section 3.1 and Section 3.2.  The authorization
        server MUST reject JWTs that do not use the specified explicit
        type value.

   2.   The JWT MUST contain an iss (issuer) claim that contains a
        unique identifier for the entity that issued the JWT.  In the
        absence of an application profile specifying otherwise,
        compliant applications MUST compare issuer values using the
        Simple String Comparison method defined in Section 6.2.1 of RFC
        3986 [RFC3986].

   3.   The JWT MUST contain a sub (subject) claim identifying the
        principal that is the subject of the JWT.  Two cases need to be
        differentiated:

        a.  For the authorization grant, the subject typically
            identifies an authorized accessor for which the access token
            is being requested (i.e., the resource owner or an
            authorized delegate), but in some cases, may be a
            pseudonymous identifier or other value denoting an anonymous
            user.

        b.  For client authentication, the subject MUST be the client_id
            of the OAuth client.




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   4.   The JWT MUST contain an aud (audience) claim containing the
        issuer identifier [RFC8414] of the authorization server as its
        sole value.  The authorization server MUST have an issuer
        identifier to be used with this specification.  Unlike the aud
        value specified in [RFC7523], there MUST be no value other than
        the issuer identifier of the intended authorization server used
        as the audience of the JWT; this includes that the token
        endpoint URL of the authorization server MUST NOT be used as an
        audience value.  To simplify implementations, the aud claim
        value MUST be a JSON string, and not a single-valued JSON array.
        The authorization server MUST reject any JWT that does not
        contain its issuer identifier as its sole audience value.  In
        the absence of an application profile specifying otherwise,
        compliant applications MUST compare the audience values using
        the Simple String Comparison method defined in Section 6.2.1 of
        RFC 3986 [RFC3986].

   5.   The JWT MUST contain an exp (expiration time) claim that limits
        the time window during which the JWT can be used.  The
        authorization server MUST reject any JWT with an expiration time
        that has passed, subject to allowable clock skew between
        systems.  Note that the authorization server may reject JWTs
        with an exp claim value that is unreasonably far in the future.

   6.   The JWT MAY contain an nbf (not before) claim that identifies
        the time before which the token MUST NOT be accepted for
        processing.

   7.   The JWT MAY contain an iat (issued at) claim that identifies the
        time at which the JWT was issued.  Note that the authorization
        server may reject JWTs with an iat claim value that is
        unreasonably far in the past.

   8.   The JWT MAY contain a jti (JWT ID) claim that provides a unique
        identifier for the token.  The authorization server MAY ensure
        that JWTs are not replayed by maintaining the set of used jti
        values for the length of time for which the JWT would be
        considered valid based on the applicable exp instant.

   9.   The JWT MAY contain other claims.

   10.  The JWT MUST be digitally signed or have a Message
        Authentication Code (MAC) applied by the issuer.  The
        authorization server MUST reject JWTs with an invalid signature
        or MAC.

   11.  The authorization server MUST reject a JWT that is not valid in
        all other respects per "JSON Web Token (JWT)" [JWT].



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3.1.  Authorization Grant Processing

   Authorization grant JWTs MUST be explicitly typed by using the typ
   header parameter value authorization-grant+jwt or another more
   specific explicit type value defined by a specification profiling
   this specification.  Authorization grant JWTs not using the explicit
   type value MUST be rejected by the authorization server.

   JWT authorization grants may be used with or without client
   authentication or identification.  Whether or not client
   authentication is needed in conjunction with a JWT authorization
   grant, as well as the supported types of client authentication, are
   policy decisions at the discretion of the authorization server.
   However, if client credentials are present in the request, the
   authorization server MUST validate them.

   If the JWT is not valid, or the current time is not within the
   token's valid time window for use, the authorization server
   constructs an error response as defined in OAuth 2.0 [RFC6749].  The
   value of the error parameter MUST be the invalid_grant error code.
   The authorization server MAY include additional information regarding
   the reasons the JWT was considered invalid using the
   error_description or error_uri parameters.

   For example:

     HTTP/1.1 400 Bad Request
     Content-Type: application/json
     Cache-Control: no-store

     {
      "error":"invalid_grant",
      "error_description":"Audience validation failed"
     }

3.2.  Client Authentication Processing

   Client authentication JWTs MUST be explicitly typed by using the typ
   header parameter value client-authentication+jwt another more
   specific explicit type value defined by a specification profiling
   this specification.  Client authentication JWTs not using the
   explicit type value MUST be rejected by the authorization server.









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   If the client JWT is not valid, the authorization server constructs
   an error response as defined in OAuth 2.0 [RFC6749].  The value of
   the error parameter MUST be the invalid_client error code.  The
   authorization server MAY include additional information regarding the
   reasons the JWT was considered invalid using the error_description or
   error_uri parameters.

4.  Authorization Grant Example

   The following examples illustrate what a conforming JWT and an access
   token request would look like.

   The example shows a JWT issued and signed by the system entity
   identified as https://jwt-idp.example.com.  The subject of the JWT is
   identified by email address as mike@example.com.  The intended
   audience of the JWT is https://authz.example.net, which is the
   authorization server's issuer identifier.  The JWT is sent as part of
   an access token request to the authorization server's token endpoint
   at https://authz.example.net/token.oauth2.

   Below is an example JSON object that could be encoded to produce the
   JWT Claims Set for a JWT:

     {"aud":"https://authz.example.net",
      "iss":"https://jwt-idp.example.com",
      "sub":"mailto:mike@example.com",
      "iat":1731721541,
      "exp":1731725141,
      "http://claims.example.com/member":true
     }

   The following example JSON object, used as the header parameters of a
   JWT, declares that the JWT is an authorization grant JWT, is signed
   with the Elliptic Curve Digital Signature Algorithm (ECDSA) P-256
   with SHA-256, and was signed with a key identified by the kid value
   16.

     {"typ":"authorization-grant+jwt","alg":"ES256","kid":"16"}

   To present the JWT with the claims and header shown in the previous
   example as part of an access token request, for example, the client
   might make the following HTTPS request (with extra line breaks for
   display purposes only):








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     POST /token.oauth2 HTTP/1.1
     Host: authz.example.net
     Content-Type: application/x-www-form-urlencoded

     grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
     &assertion=eyJ0eXAiOiJhdXRob3JpemF0aW9uLWdyYW50K2p3dCIsImFsZyI6Ik
       VTMjU2Iiwia2lkIjoiMTYifQ.
     eyJhdWQiOiJodHRwczovLw[...omitted for brevity...].
     J9l-ZhwP[...omitted for brevity...]

5.  Interoperability Considerations

   Agreement between system entities regarding identifiers, keys, and
   endpoints is required in order to achieve interoperable deployments
   of this profile.  Specific items that require agreement include
   values for the issuer identifiers, the locations of endpoints, the
   key used to apply and verify the digital signature or MAC over the
   JWT, one-time use restrictions on the JWT, maximum JWT lifetime
   allowed, and the specific subject and claim requirements of the JWT.
   The exchange of such information is explicitly out of scope for this
   specification.  In some cases, additional profiles may be created
   that constrain or prescribe these values or specify how they are to
   be exchanged.  Examples of such profiles include the OAuth 2.0
   Dynamic Client Registration Protocol [RFC7591], OAuth 2.0
   Authorization Server Metadata [RFC8414], OpenID Connect Dynamic
   Client Registration 1.0 [OpenID.Registration], OpenID Connect
   Discovery 1.0 [OpenID.Discovery], and OpenID Federation 1.0
   [OpenID.Federation].

   The RS256 algorithm, from [JWA], is a mandatory-to-implement JSON Web
   Signature algorithm for this profile.

6.  Security Considerations

   The security considerations described within the following
   specifications are all applicable to this document: "Assertion
   Framework for OAuth 2.0 Client Authentication and Authorization
   Grants" [RFC7521], "The OAuth 2.0 Authorization Framework" [RFC6749],
   and "JSON Web Token (JWT)" [JWT].

   The specification does not mandate replay protection for the JWT
   usage for either the authorization grant or for client
   authentication.  It is an optional feature, which implementations may
   employ at their own discretion.

   This specification tightens the JWT audience requirements to prevent
   attacks that could result from exploiting audience ambiguities
   allowed by [RFC7523].



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7.  Privacy Considerations

   A JWT may contain privacy-sensitive information and, to prevent
   disclosure of such information to unintended parties, should only be
   transmitted over encrypted channels, such as Transport Layer Security
   (TLS).  In cases where it is desirable to prevent disclosure of
   certain information to the client, the JWT should be encrypted to the
   authorization server.

   Deployments should determine the minimum amount of information
   necessary to complete the exchange and include only such claims in
   the JWT.  In some cases, the sub (subject) claim can be a value
   representing an anonymous or pseudonymous user, as described in
   Section 6.3.1 of the OAuth Assertion Framework [RFC7521].

8.  IANA Considerations

   The IANA actions of registering the URNs urn:ietf:params:oauth:grant-
   type:jwt-bearer and urn:ietf:params:oauth:client-assertion-type:jwt-
   bearer in the IANA "OAuth URI" registry [IANA.OAuth.Parameters]
   established by "An IETF URN Sub-Namespace for OAuth" [RFC6755] were
   performed by [RFC7523].

8.1.  Media Type Registration

   This section registers the following media types [RFC2046] in the
   "Media Types" registry [IANA.MediaTypes] in the manner described in
   [RFC6838].

8.1.1.  Registry Contents

   *  Type name: application
   *  Subtype name: authorization-grant+jwt
   *  Required parameters: n/a
   *  Optional parameters: n/a
   *  Encoding considerations: binary; An authorization grant JWT is a
      JWT; JWT values are encoded as a series of base64url-encoded
      values (some of which may be the empty string) separated by period
      ('.') characters.
   *  Security considerations: See Section 6 of this specification
   *  Interoperability considerations: n/a
   *  Published specification: Section 3.1 of this specification
   *  Applications that use this media type: Applications that use this
      specification
   *  Fragment identifier considerations: n/a
   *  Additional information:
         Magic number(s): n/a
         File extension(s): n/a



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         Macintosh file type code(s): n/a
   *  Person & email address to contact for further information:
      Michael B.  Jones, michael_b_jones@hotmail.com
   *  Intended usage: COMMON
   *  Restrictions on usage: none
   *  Author: Michael B.  Jones, michael_b_jones@hotmail.com
   *  Change controller: OpenID Foundation Artifact Binding Working
      Group - openid-specs-ab@lists.openid.net
   *  Provisional registration?  No

   *  Type name: application
   *  Subtype name: client-authentication+jwt
   *  Required parameters: n/a
   *  Optional parameters: n/a
   *  Encoding considerations: binary; A client authentication JWT is a
      JWT; JWT values are encoded as a series of base64url-encoded
      values (some of which may be the empty string) separated by period
      ('.') characters.
   *  Security considerations: See Section 6 of this specification
   *  Interoperability considerations: n/a
   *  Published specification: Section 3.2 of this specification
   *  Applications that use this media type: Applications that use this
      specification
   *  Fragment identifier considerations: n/a
   *  Additional information:
         Magic number(s): n/a
         File extension(s): n/a
         Macintosh file type code(s): n/a
   *  Person & email address to contact for further information:
      Michael B.  Jones, michael_b_jones@hotmail.com
   *  Intended usage: COMMON
   *  Restrictions on usage: none
   *  Author: Michael B.  Jones, michael_b_jones@hotmail.com
   *  Change controller: OpenID Foundation Artifact Binding Working
      Group - openid-specs-ab@lists.openid.net
   *  Provisional registration?  No

9.  Updates to RFC 7521

   This section updates "Assertion Framework for OAuth 2.0 Client
   Authentication and Authorization Grants" [RFC7521] to tighten its
   audience requirements.

   The description of the Audience parameter in Section 5.1 of [RFC7521]
   (Assertion Metamodel) is replaced by:






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   Audience
      A value that identifies the party intended to process the
      assertion.  The audience MUST contain the issuer identifier
      [RFC8414] of the authorization server as its sole value.  Unlike
      the audience value specified in [RFC7521], there MUST be no value
      other than the issuer identifier of the intended authorization
      server used as the audience of the assertion; this includes that
      the token endpoint URL of the authorization server MUST NOT be
      used as an audience value.

   The description of the Audience parameter in Section 5.2 of [RFC7521]
   (General Assertion Format and Processing Rules) is replaced by:

      The assertion MUST contain an audience that identifies the
      authorization server as the intended audience, with the issuer
      identifier [RFC8414] of the authorization server as its sole
      value.  The authorization server MUST reject any assertion that
      does not contain its own issuer identifier as the sole audience
      value.

   In the list of agreements required by participants in Section 7 of
   [RFC7521] (Interoperability Considerations), "Audience identifiers"
   is removed from the list.

10.  Updates to RFC 7522

   This section updates "Security Assertion Markup Language (SAML) 2.0
   Profile for OAuth 2.0 Client Authentication and Authorization Grants"
   [RFC7522] to tighten its audience requirements.

   The description of the Audience element in Item 2 of Section 3 of
   [RFC7522] (Assertion Format and Processing Requirements) is replaced
   by:

      The Assertion MUST contain a <Conditions> element with an
      <AudienceRestriction> element with a single <Audience> element
      that identifies the authorization server as the intended audience.
      The value of the <Audience> element MUST be the issuer identifier
      [RFC8414] of the authorization server.  Section 2.5.1.4 of
      "Assertions and Protocols for the OASIS Security Assertion Markup
      Language (SAML) V2.0" [OASIS.saml-core-2.0-os] defines the
      <AudienceRestriction> and <Audience> elements.  Unlike the
      audience value specified in [RFC7522], there MUST be no value
      other than the issuer identifier of the intended authorization
      server used as the audience of the assertion; this includes that
      the token endpoint URL of the authorization server MUST NOT be
      used as an audience value.




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      The authorization server MUST reject any assertion that does not
      contain its own issuer identifier as the sole audience value.

   In Section 4 of [RFC7522] (Authorization Grant Example), the
   sentence:

      The intended audience of the Assertion is https://saml-
      sp.example.net, which is an identifier for a SAML Service Provider
      with which the authorization server identifies itself.

   is replaced by:

      The intended audience of the Assertion is
      https://authz.example.net, which is the authorization server's
      issuer identifier.

   In the same section, the SAML 2.0 Assertion example is replaced by:


































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     <Assertion IssueInstant="2024-11-17T00:53:34.619Z"
       ID="ef1xsbZxPV2oqjd7HTLRLIBlBb7"
       Version="2.0"
       xmlns="urn:oasis:names:tc:SAML:2.0:assertion">
      <Issuer>https://saml-idp.example.com</Issuer>
      <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
       [...omitted for brevity...]
      </ds:Signature>
      <Subject>
       <NameID
        Format="urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress">
        brian@example.com
       </NameID>
       <SubjectConfirmation
         Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
        <SubjectConfirmationData
          NotOnOrAfter="2024-11-17T00:58:34.619Z"
          Recipient="https://authz.example.net/token.oauth2"/>
        </SubjectConfirmation>
       </Subject>
       <Conditions>
         <AudienceRestriction>
           <Audience>https://authz.example.net</Audience>
         </AudienceRestriction>
       </Conditions>
       <AuthnStatement AuthnInstant="2024-11-17T00:53:34.371Z">
         <AuthnContext>
           <AuthnContextClassRef>
             urn:oasis:names:tc:SAML:2.0:ac:classes:X509
           </AuthnContextClassRef>
         </AuthnContext>
       </AuthnStatement>
     </Assertion>

                    Figure 1: Example SAML 2.0 Assertion

   In the list of agreements required by participants in Section 5 of
   [RFC7521] (Interoperability Considerations), "Audience identifiers"
   is removed from the list.

11.  Updates to RFC 9101

   This section updates "The OAuth 2.0 Authorization Framework: JWT-
   Secured Authorization Request (JAR)" [RFC9101] to tighten its
   audience requirements.






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   The second paragraph in Section 4 of [RFC9101] (The OAuth 2.0
   Authorization Framework: JWT-Secured Authorization Request (JAR)),
   which describes the audience value, is replaced by:

      To sign, JSON Web Signature (JWS) [RFC7515] is used.  The result
      is a JWS-signed [JWT].  If signed, the Authorization Request
      Object MUST contain the Claims iss (issuer) and aud (audience) as
      members with their semantics being the same as defined in the
      [JWT] specification.  The issuer identifier of the authorization
      server, as defined in [RFC8414], MUST be used as the sole value of
      the aud (audience) claim.  The authorization server MUST reject
      any such JWT that does not contain its own issuer identifier as
      the sole audience value.

12.  Updates to RFC 9126

   This section updates "OAuth 2.0 Pushed Authorization Requests"
   [RFC9126] to tighten its audience requirements.

   The paragraph describing the audience value in Section 2 of [RFC9126]
   (Pushed Authorization Request Endpoint) is replaced by:

      This update resolves the potential ambiguity regarding the
      appropriate audience value to use when employing JWT client
      assertion-based authentication (as defined in Section 2.2 of
      [RFC7523] with the private_key_jwt or client_secret_jwt
      authentication method names per Section 9 of [OpenID.Core]) that
      was described in [RFC9126].  To address that ambiguity, the issuer
      identifier URL of the authorization server according to [RFC8414]
      MUST be used as the sole value of the audience.  The authorization
      server MUST reject any such JWT that does not contain its own
      issuer identifier as the sole audience value.

13.  References

13.1.  Normative References

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

   [JWT]      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>.

   [OASIS.saml-core-2.0-os]
              Cantor, S., Kemp, J., Philpott, R., and E. Maler,
              "Assertions and Protocols for the OASIS Security Assertion



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              Markup Language (SAML) V2.0", OASIS Standard saml-core-
              2.0-os, March 2005, <https://docs.oasis-
              open.org/security/saml/v2.0/saml-core-2.0-os.pdf>.

   [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>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.

   [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>.

   [RFC7521]  Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
              "Assertion Framework for OAuth 2.0 Client Authentication
              and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
              May 2015, <https://www.rfc-editor.org/info/rfc7521>.

   [RFC7522]  Campbell, B., Mortimore, C., and M. Jones, "Security
              Assertion Markup Language (SAML) 2.0 Profile for OAuth 2.0
              Client Authentication and Authorization Grants", RFC 7522,
              DOI 10.17487/RFC7522, May 2015,
              <https://www.rfc-editor.org/info/rfc7522>.

   [RFC7523]  Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
              (JWT) Profile for OAuth 2.0 Client Authentication and
              Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May
              2015, <https://www.rfc-editor.org/info/rfc7523>.

   [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>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.





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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>.

   [RFC8725]  Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
              Current Practices", BCP 225, RFC 8725,
              DOI 10.17487/RFC8725, February 2020,
              <https://www.rfc-editor.org/info/rfc8725>.

   [RFC9101]  Sakimura, N., Bradley, J., and M. Jones, "The OAuth 2.0
              Authorization Framework: JWT-Secured Authorization Request
              (JAR)", RFC 9101, DOI 10.17487/RFC9101, August 2021,
              <https://www.rfc-editor.org/info/rfc9101>.

   [RFC9126]  Lodderstedt, T., Campbell, B., Sakimura, N., Tonge, D.,
              and F. Skokan, "OAuth 2.0 Pushed Authorization Requests",
              RFC 9126, DOI 10.17487/RFC9126, September 2021,
              <https://www.rfc-editor.org/info/rfc9126>.

13.2.  Informative References

   [IANA.MediaTypes]
              IANA, "Media Types",
              <https://www.iana.org/assignments/media-types>.

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

   [OpenID.Core]
              Sakimura, N., Bradley, J., Jones, M.B., de Medeiros, B.,
              and C. Mortimore, "OpenID Connect Core 1.0 incorporating
              errata set 2", 15 December 2023,
              <https://openid.net/specs/openid-connect-core-1_0.html>.

   [OpenID.Discovery]
              Sakimura, N., Bradley, J., Jones, M.B., and E. Jay,
              "OpenID Connect Discovery 1.0 incorporating errata set 2",
              15 December 2023, <https://openid.net/specs/openid-
              connect-discovery-1_0.html>.

   [OpenID.Federation]
              Hedberg, R., Jones, M. B., Solberg, A., Bradley, J.,
              Marco, G. D., and V. Dzhuvinov, "OpenID Federation 1.0",
              24 October 2024,
              <https://openid.net/specs/openid-federation-1_0.html>.




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   [OpenID.Registration]
              Sakimura, N., Bradley, J., and M.B. Jones, "OpenID Connect
              Dynamic Client Registration 1.0 incorporating errata set
              2", 15 December 2023, <https://openid.net/specs/openid-
              connect-registration-1_0.html>.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <https://www.rfc-editor.org/info/rfc2046>.

   [RFC6755]  Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
              for OAuth", RFC 6755, DOI 10.17487/RFC6755, October 2012,
              <https://www.rfc-editor.org/info/rfc6755>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

   [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>.

Appendix A.  Document History

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

   -00

   *  Initial draft starting with rfc7523.xml, updated to use current
      references and affiliations and modern xml2rfc syntax, removing
      the IANA actions already performed, and adding the Document
      History section.

   *  Use AS issuer identifier as the sole audience value.

   *  Explicitly typed authorization grant JWTs and client
      authentication JWTs.

   *  Update audience requirements in "Assertion Framework for OAuth 2.0
      Client Authentication and Authorization Grants" [RFC7521].

   *  Update audience requirements in "Security Assertion Markup
      Language (SAML) 2.0 Profile for OAuth 2.0 Client Authentication
      and Authorization Grants" [RFC7522].




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   *  Update audience requirements in "The OAuth 2.0 Authorization
      Framework: JWT-Secured Authorization Request (JAR)" [RFC9101].

   *  Update audience requirements in "OAuth 2.0 Pushed Authorization
      Requests" [RFC9126].

Acknowledgements

   The profile in [RFC7523] was derived from "Security Assertion Markup
   Language (SAML) 2.0 Profile for OAuth 2.0 Client Authentication and
   Authorization Grants" [RFC7522], which has the same authors as this
   document.

   We would like to acknowledge the contributions of the following
   people to this specification: John Bradley, Ralph Bragg, Joseph
   Heenan, Pedram Hosseyni, Aaron Parecki, Filip Skokan, and Tim
   Würtele.

Authors' Addresses

   Michael B. Jones
   Self-Issued Consulting
   Email: michael_b_jones@hotmail.com
   URI:   https://self-issued.info/


   Brian Campbell
   Ping Identity
   Email: brian.d.campbell@gmail.com


   Chuck Mortimore
   Disney
   Email: charliemortimore@gmail.com

















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