NimbusJwtDecoderJwkSupport should offer method to get OAuth2TokenValidator

Summary

NimbusJwtDecoderJwkSupport is the underlying implementation for Spring Security JwtDecoder.

NimbusJwtDecoderJwkSupport provides a method to setJwtValidator(OAuth2TokenValidator<Jwt>), but it does not have a method to retrieve the set validator(s).

NimbusJwtDecoderJwkSupport is used to auto-configure a JwtDecoder bean in OAuth2ResourceServerJwkConfiguration and its instantiation and especially the set JWT validators depend on the existence of either a JWKS URI or an Issuer URI from the spring.security.oauth2.resourceserver.jwt.issuer-uri.

If an application or library wants to add additional JWT validators, today's guidance in Spring Security documentation is to re-declare a JwtDecoder bean and set the validators on it.

Problem is, that now the application / library has no access to the configured defaults of Spring Security which (as described above) depend on the user's configurations.

Ideally we would like to do something like this:

public class WebSecurityConfigurations extends WebSecurityConfigurerAdapter {
     WebSecurityConfigurations(JwtDecoder standardSpringSecurityJwtDecoder) {
         NimbusJwtDecoderJwkSupport decoder = ((NimbusJwtDecoderJwkSupport) standardSpringSecurityJwtDecoder);
         OAuth2TokenValidator<Jwt> standardValidators = decoder.getValidator(); // does not work today.
         OAuth2TokenValidator<Jwt> myCustomValidor = new MyCustomValidator();
         OAuth2TokenValidator<Jwt> jwtValidators = new DelegatingOAuth2TokenValidator<Jwt>(standardValidators, myCustomValidator);
         decoder.setJwtValidator(jwtValidators);
    }
...
}

As an alternative, it might also be ok to add an addValidator(OAuth2TokenValidator<Jwt>) method to NimbusJwtDecoderJwkSupport, though presumably it's implementation would result in a lot of chained DelegatingOAuth2TokenValidator<Jwt>s.

Actual Behavior

No way for an application to get the OAuth2TokenValidators of the auto-configured standard Spring Security JwtDecoder.

Expected Behavior

A way for an application to get the OAuth2TokenValidators of the auto-configured standard Spring Security JwtDecoder or to add additional custom OAuth2TokenValidator.

References

OAuth2ResourceServerJwkConfiguration (Auto-Configuration):

/*
 * Copyright 2012-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
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 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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package org.springframework.boot.autoconfigure.security.oauth2.resource.servlet;

import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.autoconfigure.security.oauth2.resource.IssuerUriCondition;
import org.springframework.boot.autoconfigure.security.oauth2.resource.OAuth2ResourceServerProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.oauth2.jwt.JwtDecoder;
import org.springframework.security.oauth2.jwt.JwtDecoders;
import org.springframework.security.oauth2.jwt.NimbusJwtDecoderJwkSupport;

/**
 * Configures a {@link JwtDecoder} when a JWK Set URI or OpenID Connect Issuer URI is
 * available.
 *
 * @author Madhura Bhave
 * @author Artsiom Yudovin
 */
@Configuration
class OAuth2ResourceServerJwkConfiguration {

	private final OAuth2ResourceServerProperties properties;

	OAuth2ResourceServerJwkConfiguration(OAuth2ResourceServerProperties properties) {
		this.properties = properties;
	}

	@Bean
	@ConditionalOnProperty(name = "spring.security.oauth2.resourceserver.jwt.jwk-set-uri")
	@ConditionalOnMissingBean
	public JwtDecoder jwtDecoderByJwkKeySetUri() {
		return new NimbusJwtDecoderJwkSupport(this.properties.getJwt().getJwkSetUri());
	}

	@Bean
	@Conditional(IssuerUriCondition.class)
	@ConditionalOnMissingBean
	public JwtDecoder jwtDecoderByIssuerUri() {
		return JwtDecoders
				.fromOidcIssuerLocation(this.properties.getJwt().getIssuerUri());
	}

}

Version

Spring Security Version 5.1.5.RELEASE