Flink differentiates between internal and external connectivity in case of encryption.
Internal connectivity refers to all connections made between Flink processes.
Because internal communication is mutually authenticated, keystore and truststore typically contain the same dedicated certificate. The certificate can use wildcard hostnames or addresses because the certificate is expected to be a shared secret and hostnames are not verified.
External connectivity (REST endpoints)
External connectivity refers to all connections made from the outside to Flink processes.
When Flink applications are running on CDP Private Cloud Base clusters, the Flink web dashboard is accessible through the tracking URL of the YARN proxy. Depending on the security setup in YARN, the proxy itself can enforce authentication (SPNEGO) and encryption (TLS) already for YARN jobs. This can be sufficient when CDP perimeter is protected by a firewall from external user access. If there is no such protection available, additional TLS configuration is required to protect REST endpoints with TLS.
For more information, see the Apache Flink documentation.