Client Authentication for Kafka Producer in Liberty Server

Our problem

We want to run multiple java programmes (in current use case Kafka-Producers) in a single CICS Liberty Server. Authentication on Kafka-Broker side (hosted on our on-premise cloud) is done by client certificates. Our security department requires that we use separate certificates to distinguish different applications. However CICS Liberty Server supports one universal certificate for a given IP-Adress+Port combination, i.e. our Kafka-Broker.

Our suggestion

Each Kafka Producer (i.e. Java program on Liberty) can configure/manage its own certificate decentrally, without a central certificate in Liberty Server.

When creating Kafka events by the producer, it can be configured in the keystores. Here is the documentation for the Confluent Kafka that describes the attributes: https://docs.confluent.io/platform/current/connect/security.html

The keystore is set using the variables:

ssl.keystore.location=/var/private/ssl/kafka.source.keystore.jks
ssl.keystore.password=connector1234
ssl.key.password=connector1234

From this keystore the first certificate is grabbed to authenticate and encrypt the connection. This keystore must be password protected, the key in it must also be password protected.

It should be possible to change these properties in different places, but basically everything seems to converge in one place: The Producer is given a Properties object in the Java program when it is created via the constructor Producer(Properties p). This Properties can be given before over these variables.

Properties props = new Properties();
props.put("ssl.keystore.location", "/path/to/keystore.jks");
props.put("ssl.keystore.password", "keystorepassword ");
props.put("ssl.key.password ", "keystorepassword ");
 
Producer producer = new Producer(props); 

This is also described in the producer documentation: https://kafka.apache.org/20/javadoc/org/apache/kafka/clients/producer/KafkaProducer.html