Client applications in the same mesh

This scenario covers using Kafka ACLs when your client applications are in the same Istio mesh as the Kafka cluster. In this scenario, the client application is identified as CN=<namespace>-<service-account-name>. For example, if you have a kcat application deployed into the kafka namespace with the default service account, it’s identified as CN=kafka-default.

Prerequisites

To use Kafka ACLs with Istio mTLS, you need:

• a Kubernetes cluster (version 1.19 and above), with
• at least 12 vCPU and 12 GB of memory, and
• with the capability to provision LoadBalancer Kubernetes services.
• A Kafka cluster.

Steps

1. Enable ACLs and configure an external listener using Streaming Data Manager. Complete the following steps.

   1. Verify that your deployed Kafka cluster is up and running:

      smm sdm cluster get --namespace <namespace-of-your-cluster> --kafka-cluster <name-of-your-kafka-cluster> --kubeconfig <path-to-kubeconfig-file>
      

      Expected output:

      Namespace  Name   State           Image                               Alerts  Cruise Control Topic Status  Rolling Upgrade Errors  Rolling Upgrade Last Success
      kafka      kafka  ClusterRunning  banzaicloud/kafka:2.13-2.5.0-bzc.1  0       CruiseControlTopicReady      0
      

   2. Enable ACLs and configure an external listener. The deployed Kafka cluster has no ACLs, and external access is disabled by default. Enable them by applying the following changes:

      smm sdm cluster update --namespace kafka --kafka-cluster kafka --kubeconfig <path-to-kubeconfig-file> -f -<<EOF
      apiVersion: kafka.banzaicloud.io/v1beta1
      kind: KafkaCluster
      spec:
        ingressController: "istioingress"
        istioIngressConfig:
          gatewayConfig:
            mode: PASSTHROUGH
      readOnlyConfig: |
          auto.create.topics.enable=false
          offsets.topic.replication.factor=2
          authorizer.class.name=kafka.security.authorizer.AclAuthorizer
          allow.everyone.if.no.acl.found=false    
      listenersConfig:
          externalListeners:
          - type: "plaintext"
            name: "external"
            externalStartingPort: 19090
            containerPort: 9094
      EOF
      

   3. The update in the previous step reconfigures the Kafka cluster to receive rolling updates. Verify that this is reflected in the state of the cluster.

      smm sdm cluster get --namespace kafka --kafka-cluster kafka --kubeconfig <path-to-kubeconfig-file>
      

      Expected output:

      Namespace  Name   State                    Image                               Alerts  Cruise Control Topic Status  Rolling Upgrade Errors  Rolling Upgrade Last Success
      kafka      kafka  ClusterRollingUpgrading  banzaicloud/kafka:2.13-2.5.0-bzc.1  0       CruiseControlTopicReady      0
      

   4. Wait until the reconfiguration is finished and the cluster is in the ClusterRunning state. This can take a while, as the rolling upgrade applies changes on a broker-by-broker basis.

2. (Optional) At this stage, every listener of the Kafka cluster is configured to the PLAINTEXT protocol. No SSL is configured, mTLS is provided by Istio. You can verify that mTLS is used by trying to connect with openssl (without a certificate) to see that a server certificate is returned and the SSL handshake fails:

   kubectl run openssl --image=frapsoft/openssl --restart=Never -it --rm -- s_client -connect kafka-all-broker.kafka.svc.cluster.local:29092
   

3. From now on, Kafka applications are automatically authenticated and authorized by their service account.