Abstract:
Transport Layer Security (TLS) is an important protocol and widely used by web servers to provide security. In our work we analyzed the implementation of client certificate authentication in different web servers. We specifically focused on additional methods of access control beyond just checking the validity and trust chain of a certificate. Our tested setups include different configurations of name based access control in the three popular web servers Apache HTTP, NGINX and Apache Tomcat. To execute our constructed test cases, we extended the TLS-Scanner tool. Overall we found one possible way to bypass access control in some Apache HTTP servers.