Configure Simple ACLs with Confluent for Kubernetes

To deploy Kafka with the Access Control Lists authorization, specify the settings in your Kafka CustomResource:

kind: Kafka
    type: simple             --- [1]
  • [1] Required. Set it to simple. Kafka will be configured to use simple authorization (ZooKeeper-backed ACLs) when configured.

mTLS authentication: Extracting principal from certificate

When mTLS authentication is enabled, Confluent Platform determines the identity of the authenticated principal via data extracted from the client certificate. The Subject section of the certificate is used to determine the username.

For example, with the following certificate’s subject (C=US, ST=CA, L=Palo Alto), the username will be extracted as User:L=Palo Alto,ST=CA,C=US.

        Version: 3 (0x2)
        Serial Number:
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, ST=Palo Alto, L=CA, O=Company, OU=Engineering, CN=TestCA
            Not Before: Mar 28 16:37:00 2019 GMT
            Not After : Mar 26 16:37:00 2024 GMT
        Subject: C=US, ST=CA, L=Palo Alto
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)

User:ANONYMOUS is the default user for internal clients and inter-broker communication.

When Kafka is configured with mTLS authentication, in addition to User:ANONYMOUS, the cert user name is required.

Typically, you will have many different users and clients of Confluent Platform. In some cases, you may have shared client certificates across multiple users/clients, but the best practice is to issue unique client certificates for each user and certificate, and each certificate should have a unique subject/username. For each user/client, you must decide what they should be authorized to access within Confluent Platform, and ensure that the corresponding ACLs have been created for the subject/username of their corresponding client certificates. Follow the instructions in Authorization using ACLs to enable ACL authorization for Kafka objects.