Hello, I’m currently working on updating an LDAP directory server with support for quantum-resistant encryption. This includes support for TLS-secured connections, and I see that via JEP 527, JDK 27 includes support for some quantum-resistant hybrid key exchange algorithms. And because X25519MLKEM768 is being set as the highest-priority curve group, this is a feature that should basically come for free when communicating with peers that support that curve group.
However, I can’t seem to find any method that can be used to determine which curve group was actually selected for a connection during the TLS negotiation process. This information doesn’t seem to be available in SSLSession, or anywhere else that I can find. When I run a test client with -Djavax.net.debug=all, I can see the “named_group” field in the debug output for the ServerHello message, but there just doesn’t seem to be any way to gain programmatic access to that. I think that it’s essential to be able to obtain the negotiated curve group programmatically to be able to verify whether a given TLS session is protected with quantum-resistant encryption. I’d like to be able to log this along with other details like the negotiated TLS protocol and cipher suite, and potentially to even be able to use this information to make access control decisions, like only returning certain sensitive information to clients if I can confirm if the communication has been secured with quantum-resistant encryption. Would it be possible to get a method like SSLSession.getNamedGroup() to be able to determine which named group was selected in the course of negotiating the session? Thanks! Neil Wilson
