Self-Issued Consulting

michael_b_jones@hotmail.com https://self-issued.info/

Ping Identity

brian.d.campbell@gmail.com

Disney

charliemortimore@gmail.com

Security OAuth Working Group OAuth JWT Assertion Token Security Token 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.

JSON Web Token (JWT) is a JSON-based 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 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" 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 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" . 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 or other endpoints such as the pushed authorization 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.

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 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.

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

The OAuth Assertion Framework 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.

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 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 , to indicate the requested scope. Authentication of the client is optional, as described in Section 3.2.1 of OAuth 2.0 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):

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):

In order to issue an access token response as described in OAuth 2.0 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. The JWT MUST be explicitly typed, as defined in Section 3.11 of . The typ header parameter values that MUST be used are defined in and . The authorization server MUST reject JWTs that do not use the specified explicit type value. 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 . The JWT MUST contain a sub (subject) claim identifying the principal that is the subject of the JWT. Two cases need to be differentiated: 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. For client authentication, the subject MUST be the client_id of the OAuth client. The JWT MUST contain an aud (audience) claim containing the issuer identifier 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 , 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 . 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. The JWT MAY contain an nbf (not before) claim that identifies the time before which the token MUST NOT be accepted for processing. 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. 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. The JWT MAY contain other claims. 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. The authorization server MUST reject a JWT that is not valid in all other respects per "JSON Web Token (JWT)" .

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 . 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:

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. If the client JWT is not valid, the authorization server constructs an error response as defined in OAuth 2.0 . 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.

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:

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.

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):

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 , OAuth 2.0 Authorization Server Metadata , OpenID Connect Dynamic Client Registration 1.0 , OpenID Connect Discovery 1.0 , and OpenID Federation 1.0 . The RS256 algorithm, from , is a mandatory-to-implement JSON Web Signature algorithm for this profile.

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" , "The OAuth 2.0 Authorization Framework" , and "JSON Web Token (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 .

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 .

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 established by "An IETF URN Sub-Namespace for OAuth" were performed by .

This section registers the following media types in the "Media Types" registry in the manner described in .

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 of this specification Interoperability considerations: n/a Published specification: 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 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 of this specification Interoperability considerations: n/a Published specification: 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

This section updates "Assertion Framework for OAuth 2.0 Client Authentication and Authorization Grants" to tighten its audience requirements. The description of the Audience parameter in Section 5.1 of (Assertion Metamodel) is replaced by: A value that identifies the party intended to process the assertion. The audience MUST contain the issuer identifier of the authorization server as its sole value. Unlike the audience value specified in , 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 (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 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 (Interoperability Considerations), "Audience identifiers" is removed from the list.

This section updates "Security Assertion Markup Language (SAML) 2.0 Profile for OAuth 2.0 Client Authentication and Authorization Grants" to tighten its audience requirements. The description of the Audience element in Item 2 of Section 3 of (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 of the authorization server. Section 2.5.1.4 of "Assertions and Protocols for the OASIS Security Assertion Markup Language (SAML) V2.0" defines the <AudienceRestriction> and <Audience> elements. Unlike the audience value specified in , 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 authorization server MUST reject any assertion that does not contain its own issuer identifier as the sole audience value. In Section 4 of (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: https://saml-idp.example.com [...omitted for brevity...] brian@example.com https://authz.example.net urn:oasis:names:tc:SAML:2.0:ac:classes:X509 ]]>

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

This section updates "The OAuth 2.0 Authorization Framework: JWT-Secured Authorization Request (JAR)" to tighten its audience requirements. The second paragraph in Section 4 of (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) is used. The result is a JWS-signed . 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 specification. The issuer identifier of the authorization server, as defined in , 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.

This section updates "OAuth 2.0 Pushed Authorization Requests" to tighten its audience requirements. The paragraph describing the audience value in Section 2 of (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 with the private_key_jwt or client_secret_jwt authentication method names per Section 9 of ) that was described in . To address that ambiguity, the issuer identifier URL of the authorization server according to 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.

This specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications. It defines several IANA registries for these identifiers. JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted. Internet2

cantor.2@osu.edu

Nokia

John.Kemp@nokia.com

RSA Security

rphilpott@rsasecurity.com

Sun Microsystems

eve.maler@sun.com

NAT.Consulting Yubico Self-Issued Consulting Google Disney NAT.Consulting Yubico Self-Issued Consulting NAT.Consulting Yubico Self-Issued Consulting Illumila independent Self-Issued Consulting Sikt Yubico independent Connect2id IANA IANA

[[ to be removed by the RFC Editor before publication as an RFC ]] -00 Initial working group draft, replacing draft-jones-oauth-rfc7523bis-00.

The profile in was derived from "Security Assertion Markup Language (SAML) 2.0 Profile for OAuth 2.0 Client Authentication and Authorization Grants" , 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.