= OAuth 2.0 Changes

== Validate `typ` Header with `JwtTypeValidator`

`NimbusJwtDecoder` in Spring Security 7 will move `typ` header validation to `JwtTypeValidator` intsead of relying on Nimbus.
This brings it in line with `NimbusJwtDecoder` validating claims instead of relying on Nimbus to validate them.

If you are changing Nimbus's default type validation in a `jwtProcessorCustomizer` method, then you should move that to `JwtTypeValidator` or an implementation of `OAuth2TokenValidator` of your own.

To check if you are prepared for this change, add the default `JwtTypeValidator` to your list of validators, as this will be included by default in 7:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
JwtDecoder jwtDecoder() {
	NimbusJwtDecoder jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .validateTypes(false) <1>
        // ... your remaining configuration
        .build();
	jwtDecoder.setJwtValidator(JwtValidators.createDefaultWithValidators(
		new JwtIssuerValidator(location), JwtTypeValidator.jwt())); <2>
	return jwtDecoder;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun jwtDecoder(): JwtDecoder {
    val jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .validateTypes(false) <1>
        // ... your remaining configuration
        .build()
    jwtDecoder.setJwtValidator(JwtValidators.createDefaultWithValidators(
        JwtIssuerValidator(location), JwtTypeValidator.jwt())) <2>
    return jwtDecoder
}
----
======
<1> - Switch off Nimbus verifying the `typ` (this will be off by default in 7)
<2> - Add the default `typ` validator (this will be included by default in 7)

Note the default value verifies that the `typ` value either be `JWT` or not present, which is the same as the Nimbus default.
It is also aligned with https://datatracker.ietf.org/doc/html/rfc7515#section-4.1.9[RFC 7515] which states that `typ` is optional.


=== I'm Using A `DefaultJOSEObjectTypeVerifier`

If you have something like the following in your configuration:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
JwtDecoder jwtDecoder() {
	NimbusJwtDecoder jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .jwtProcessorCustomizer((c) -> c
            .setJWSTypeVerifier(new DefaultJOSEObjectTypeVerifier<>("JOSE"))
        )
        .build();
	return jwtDecoder;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun jwtDecoder(): JwtDecoder {
    val jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .jwtProcessorCustomizer {
            it.setJWSTypeVerifier(DefaultJOSEObjectTypeVerifier("JOSE"))
        }
        .build()
    return jwtDecoder
}
----
======

Then change this to:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
JwtDecoder jwtDecoder() {
	NimbusJwtDecoder jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .validateTypes(false)
        .build();
	jwtDecoder.setJwtValidator(JwtValidators.createDefaultWithValidators(
		new JwtIssuerValidator(location), new JwtTypeValidator("JOSE")));
	return jwtDecoder;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun jwtDecoder(): JwtDecoder {
    val jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .validateTypes(false)
        .build()
	jwtDecoder.setJwtValidator(JwtValidators.createDefaultWithValidators(
		JwtIssuerValidator(location), JwtTypeValidator("JOSE")))
    return jwtDecoder
}
----
======

To indicate that the `typ` header is optional, use `#setAllowEmpty(true)` (this is the equivalent of including `null` in the list of allowed types in `DefaultJOSEObjectTypeVerifier`).

=== I want to opt-out

If you want to keep doing things the way that you are, then the steps are similar, just in reverse:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
JwtDecoder jwtDecoder() {
	NimbusJwtDecoder jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .validateTypes(true) <1>
        .jwtProcessorCustomizer((c) -> c
            .setJWSTypeVerifier(new DefaultJOSEObjectTypeVerifier<>("JOSE"))
        )
        .build();
	jwtDecoder.setJwtValidator(new DelegatingOAuth2TokenValidator<>(
		new JwtTimestampValidator(), new JwtIssuerValidator(location))); <2>
	return jwtDecoder;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun jwtDecoder(): JwtDecoder {
    val jwtDecoder = NimbusJwtDecoder.withIssuerLocation(location)
        .validateTypes(true) <1>
        .jwtProcessorCustomizer {
            it.setJWSTypeVerifier(DefaultJOSEObjectTypeVerifier("JOSE"))
        }
        .build()
	jwtDecoder.setJwtValidator(DelegatingOAuth2TokenValidator(
        JwtTimestampValidator(), JwtIssuerValidator(location))) <2>
    return jwtDecoder
}
----
======
<1> - leave Nimbus type verification on
<2> - specify the list of validators you need, excluding `JwtTypeValidator`

For additional guidance, please see the xref:servlet/oauth2/resource-server/jwt.adoc#oauth2resourceserver-jwt-validation[JwtDecoder Validators] section in the reference.