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rfc:rfc7523

Internet Engineering Task Force (IETF) M. Jones Request for Comments: 7523 Microsoft Category: Standards Track B. Campbell ISSN: 2070-1721 Ping Identity

                                                          C. Mortimore
                                                            Salesforce
                                                              May 2015
                    JSON Web Token (JWT) Profile
    for OAuth 2.0 Client Authentication and Authorization Grants

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 is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7523.

Copyright Notice

 Copyright (c) 2015 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
 (http://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.

Jones, et al. Standards Track [Page 1] RFC 7523 OAuth JWT Assertion Profiles May 2015

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  . . . . . . . . . . .   4
   2.2.  Using JWTs for Client Authentication  . . . . . . . . . .   5
 3.  JWT Format and Processing Requirements  . . . . . . . . . . .   5
   3.1.  Authorization Grant Processing  . . . . . . . . . . . . .   7
   3.2.  Client Authentication Processing  . . . . . . . . . . . .   8
 4.  Authorization Grant Example . . . . . . . . . . . . . . . . .   8
 5.  Interoperability Considerations . . . . . . . . . . . . . . .   9
 6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
 7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  10
 8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.1.  Sub-Namespace Registration of
         urn:ietf:params:oauth:grant-type:jwt-bearer . . . . . . .  10
   8.2.  Sub-Namespace Registration of
         urn:ietf:params:oauth:client-assertion-type:jwt-bearer  .  10
 9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
   9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  12
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1. Introduction

 JSON Web Token (JWT) [JWT] is a JSON-based [RFC7159] 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.
 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

Jones, et al. Standards Track [Page 2] RFC 7523 OAuth JWT Assertion Profiles May 2015

 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.
 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 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.

Jones, et al. Standards Track [Page 3] RFC 7523 OAuth JWT Assertion Profiles May 2015

1.1. Notational Conventions

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].
 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.

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.

Jones, et al. Standards Track [Page 4] RFC 7523 OAuth JWT Assertion Profiles May 2015

 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=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.
   eyJpc3Mi[...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):
   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=eyJhbGciOiJSUzI1NiIsImtpZCI6IjIyIn0.
   eyJpc3Mi[...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.

Jones, et al. Standards Track [Page 5] RFC 7523 OAuth JWT Assertion Profiles May 2015

 1.   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].
 2.   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.
 3.   The JWT MUST contain an "aud" (audience) claim containing a
      value that identifies the authorization server as an intended
      audience.  The token endpoint URL of the authorization server
      MAY be used as a value for an "aud" element to identify the
      authorization server as an intended audience of the JWT.  The
      authorization server MUST reject any JWT that does not contain
      its own identity as the intended audience.  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].  As noted in Section 5, the precise strings to be
      used as the audience for a given authorization server must be
      configured out of band by the authorization server and the
      issuer of the JWT.
 4.   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.
 5.   The JWT MAY contain an "nbf" (not before) claim that identifies
      the time before which the token MUST NOT be accepted for
      processing.

Jones, et al. Standards Track [Page 6] RFC 7523 OAuth JWT Assertion Profiles May 2015

 6.   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.
 7.   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.
 8.   The JWT MAY contain other claims.
 9.   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.
 10.  The authorization server MUST reject a JWT that is not valid in
      all other respects per "JSON Web Token (JWT)" [JWT].

3.1. Authorization Grant Processing

 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.

Jones, et al. Standards Track [Page 7] RFC 7523 OAuth JWT Assertion Profiles May 2015

 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

 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://jwt-rp.example.net", which is an
 identifier with which the authorization server identifies itself.
 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:
   {"iss":"https://jwt-idp.example.com",
    "sub":"mailto:mike@example.com",
    "aud":"https://jwt-rp.example.net",
    "nbf":1300815780,
    "exp":1300819380,
    "http://claims.example.com/member":true}
 The following example JSON object, used as the header of a JWT,
 declares that the JWT is signed with the Elliptic Curve Digital
 Signature Algorithm (ECDSA) P-256 SHA-256 using a key identified by
 the "kid" value "16".

Jones, et al. Standards Track [Page 8] RFC 7523 OAuth JWT Assertion Profiles May 2015

   {"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):
   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=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.
   eyJpc3Mi[...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 are as
 follows: values for the issuer and audience identifiers, the location
 of the token endpoint, 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 Core
 Protocol [OAUTH-DYN-REG], OpenID Connect Dynamic Client Registration
 1.0 [OpenID.Registration], and OpenID Connect Discovery 1.0
 [OpenID.Discovery].
 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].

Jones, et al. Standards Track [Page 9] RFC 7523 OAuth JWT Assertion Profiles May 2015

 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.

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

8.1. Sub-Namespace Registration of

    urn:ietf:params:oauth:grant-type:jwt-bearer
 This section registers the value "grant-type:jwt-bearer" in the IANA
 "OAuth URI" registry established by "An IETF URN Sub-Namespace for
 OAuth" [RFC6755].
 o  URN: urn:ietf:params:oauth:grant-type:jwt-bearer
 o  Common Name: JWT Bearer Token Grant Type Profile for OAuth 2.0
 o  Change Controller: IESG
 o  Specification Document: RFC 7523

8.2. Sub-Namespace Registration of

    urn:ietf:params:oauth:client-assertion-type:jwt-bearer
 This section registers the value "client-assertion-type:jwt-bearer"
 in the IANA "OAuth URI" registry established by "An IETF URN Sub-
 Namespace for OAuth" [RFC6755].
 o  URN: urn:ietf:params:oauth:client-assertion-type:jwt-bearer
 o  Common Name: JWT Bearer Token Profile for OAuth 2.0 Client
    Authentication
 o  Change Controller: IESG
 o  Specification Document: RFC 7523

Jones, et al. Standards Track [Page 10] RFC 7523 OAuth JWT Assertion Profiles May 2015

9. References

9.1. Normative References

 [JWA]      Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
            DOI 10.17487/RFC7518, May 2015,
            <http://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,
            <http://www.rfc-editor.org/info/rfc7519>.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://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,
            <http://www.rfc-editor.org/info/rfc3986>.
 [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
            RFC 6749, DOI 10.17487/RFC6749, October 2012,
            <http://www.rfc-editor.org/info/rfc6749>.
 [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
            Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
            2014, <http://www.rfc-editor.org/info/rfc7159>.
 [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, <http://www.rfc-editor.org/info/rfc7521>.

9.2. Informative References

 [OAUTH-DYN-REG]
            Richer, J., Jones, M., Bradley, J., Machulak, M., and P.
            Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
            Work in Progress, draft-ietf-oauth-dyn-reg-29, May 2015.
 [OpenID.Discovery]
            Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID
            Connect Discovery 1.0 incorporating errata set 1",
            November 2014, <http://openid.net/specs/
            openid-connect-discovery-1_0.html>.

Jones, et al. Standards Track [Page 11] RFC 7523 OAuth JWT Assertion Profiles May 2015

 [OpenID.Registration]
            Sakimura, N., Bradley, J., and M. Jones, "OpenID Connect
            Dynamic Client Registration 1.0 incorporating errata set
            1", November 2014, <http://openid.net/specs/
            openid-connect-registration-1_0.html>.
 [RFC6755]  Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
            for OAuth", RFC 6755, DOI 10.17487/RFC6755, October 2012,
            <http://www.rfc-editor.org/info/rfc6755>.
 [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,
            <http://www.rfc-editor.org/info/rfc7522>.

Acknowledgements

 This profile 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.

Authors' Addresses

 Michael B. Jones
 Microsoft
 EMail: mbj@microsoft.com
 URI:   http://self-issued.info/
 Brian Campbell
 Ping Identity
 EMail: brian.d.campbell@gmail.com
 Chuck Mortimore
 Salesforce
 EMail: cmortimore@salesforce.com

Jones, et al. Standards Track [Page 12]

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