Override UserAuthenticationConverter for JWT OAuth Tokens

Question

I am trying to create a spring resource server secured with oauth2.

I am using auth0 for my auth2 service, and I have an api and client configured with scopes.

I have a resource server that mostly works. It is secured, and I can use @EnableGlobalMethodSecurity and @PreAuthorize("#oauth2.hasScope('profile:read')") to limit access to tokens with that scope.

However, when I try to get the Principal or the OAuth2Authentication they are both null. I've configured the resource server to use the JWK key-set-uri.

I suspect that this has to do with the DefaultUserAuthenticationConverter trying to read the the 'user_name' claim form the JWT, but it needs to be reading it from the 'sub' claim, and I don't know how to change this behaviour.

Answer 1

First create a UserAuthenticationConverter:

public class OidcUserAuthenticationConverter implements UserAuthenticationConverter {

    final String SUB = "sub";

    @Override
    public Map<String, ?> convertUserAuthentication(Authentication userAuthentication) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Authentication extractAuthentication(Map<String, ?> map) {
        if (map.containsKey(SUB)) {
            Object principal = map.get(SUB);
            Collection<? extends GrantedAuthority> authorities = null;
            return new UsernamePasswordAuthenticationToken(principal, "N/A", authorities);
        }
        return null;
    }
}

Then configure spring to use it like so:

@Configuration
public class OidcJwkTokenStoreConfiguration {
    private final ResourceServerProperties resource;

    public OidcJwkTokenStoreConfiguration(ResourceServerProperties resource) {
        this.resource = resource;
    }

    @Bean
    public TokenStore jwkTokenStore() {
        DefaultAccessTokenConverter tokenConverter = new DefaultAccessTokenConverter();
        tokenConverter.setUserTokenConverter(new OidcUserAuthenticationConverter());
        return new JwkTokenStore(this.resource.getJwk().getKeySetUri(), tokenConverter);
    }
}