Kafka's documentation should include additional guidance on how to properly enable SSL with hostname verification.
1. Hostname verification will not be performed if ssl.endpoint.identification.algorithm has not been set.
Failing to enable this will leave Kafka susceptible to 'man-in-the-middle attacks' as describe in the oracle java api docs.
2. The docs should also include instructions on how to strictly comply with RFC-2818. This will require adding the DNS SAN extension.
It's worth noting in the docs that placing the FQDN in the CN is still valid despite being less than ideal as well.
KAFKA-3665 aims to set the default value for ssl.endpoint.identification.algorithm to HTTPS. This improvement JIRA aims to document the behavior changes introduced.