tomcat client authentication using clientAuth=want

Question

My application requires client authentication for a specific URL, after client authentication succeeds the application itself also does some verification on the client certificate subject (using spring security x509 filter). I wanted to configure tomcat to force client authentication (clientAuth=true) for the specific URL, but based on this post it seems I can't do this only using tomcat - configure tomcat for client authentication only for specific URL patterns.

My question is, if I use clientAuth=want, will the following be as below when the server requests a certificate:

1. If device has an identity certificate but not trusted by the CA configured in tomcat truststoreFile, no certificate will be passed and the request will fail in the spring security filter (certificate will be null)
2. If device has an identity certificate trusted by the CA configured in tomcat truststoreFile, but is invalid (not sure what validations are done) or expired, either the authentication will fail in tomcat (before the security filter) or as in option 1 no certificate will be passed and the request will fail in the spring security filter (certificate will be null)

Is there a security hole I may be missing using this configuration of want + security filter? I guess the question is - if a certificate is eventually passed from the device to the server, the server will always validate it (not expired, trusted etc) even when using clientAuth=want and will not allow the client to continue if the certificate is invalid? The case where no certificate is passed is covered by the security filter that will check the certificate is not null..

Thanks!

Answer 1

Your assumptions in both 1. and 2. are correct. Tomcat will not allow untrusted or invalid certificates through to your application. If you get a null certificate, you can assume that either no certificate was passed, or an untrusted/invalid certificate was passed.

On the project I am working on we have the same requirement as you: client certificates for certain URLs only. We found out by experimentation how "clientAuth=want" works.