title: Enabling TLS Extension for Token Binding Protocol Negotiation with Java/SpringBoot
body: <p>In my SpringBoot web application, I want to be able to determine whether the TLS '<strong>token_binding</strong>' <strong>extension</strong> (<a href="https://www.rfc-editor.org/rfc/rfc8472" rel="nofollow noreferrer">RFC8472</a>) was used during the 'client hello-server hello' TLS negotiation procedure.</p>
  <p>From the SpringBoot point of view, I'm pretty sure that I have to override the restTemplate using my custom SSLSocketFactory instance, similar to this one: <a href="https://stackoverflow.com/questions/35270709/spring-boot-asyncresttemplate-sslsocketfactory">Spring Boot AsyncRestTemplate SSLSocketFactory</a></p>
  <p>However, I have no clue <strong>how to read/obtain token_binding extension</strong> out of this. It would appreciate an example of how to extract this, or at least how to add any extension to TLS/SSL structure using java (for SSL client).</p>