Strimzi provides a way to run an Apache Kafka cluster on Kubernetes or OpenShift in various deployment configurations. In versions 0.49.0 through 0.50.0, when using a custom Cluster or Clients CA with a multistage CA chain consisting of multiple CAs, Strimzi incorrectly configures the trusted certificates for mTLS authentication on the internal as well as user-configured listeners. All CAs from the CA chain will be trusted. And users with certificates signed by any of the CAs in the chain will be able to authenticate. This issue affects only users using a custom Cluster or Clients CA with a multistage CA chain consisting of multiple CAs. It does not affect users using the Strimzi-managed Cluster and Clients CAs. It also does not affect users using custom Cluster or Clients CA with only a single CA (i.e., no CA chain with multiple CAs). This issue has been fixed in version 0.50.1. To workaround this issue, instead of providing the full CA chain as the custom CA, users can provide only the single CA that should be used.

Strimzi provides a way to run an Apache Kafka cluster on Kubernetes or OpenShift in various deployment configurations. From 0.47.0 to before 0.50.1, when a chain consisting of multiple CA (Certificate Authority) certificates is used in the trusted certificates configuration of a Kafka Connect operand or of the target cluster in the Kafka MirrorMaker 2 operand, all of the certificates that are part of the CA chain will be trusted individually when connecting to the Apache Kafka cluster. Due to this error, the affected operand (Kafka Connect or Kafka MirrorMaker 2) might accept connections to Kafka brokers using server certificates signed by one of the other CAs in the CA chain and not just by the last CA in the chain. This issue is fixed in Strimzi 0.50.1.

Impact

In some situations, Strimzi creates an incorrect Kubernetes Role which grants the Apache Kafka Connect and Apache Kafka MirrorMaker 2 operands the GET access to all Kubernetes Secrets that exist in the given Kubernetes namespace. The exact scenario when this happens is when: Apache Kafka Connect is deployed without at least one of the following options configured: TLS encryption with configured trusted certificates (no .spec.tls.trustedCertificates section in the KafkaConnect CR) mTLS authentication (no type: tls in .spec.authentication section of the KafkaConnect CR) TLS encryption with configured trusted certificates for type: oauth authentication (no .spec.authentication.tlsTrustedCertificates section in the KafkaConnect CR) Apache Kafka MirrorMaker2 is deployed without at least one of the following options configured for the target cluster: TLS encryption with configured trusted certificates (no .spec.target.tls.trustedCertificates section in the KafkaConnect CR) mTLS authentication (no type: tls in .spec.target.authentication section of the KafkaConnect CR) TLS encryption with configured trusted certificates for type: oauth authentication (no .spec.target.authentication.tlsTrustedCertificates section in the KafkaConnect CR) TLS encryption with configured trusted certificates (no .spec.clusters[].tls.trustedCertificates section in the KafkaConnect CR for the target cluster) mTLS authentication (no type: tls in .spec.clusters[].authentication section of the KafkaConnect CR for the target cluster) TLS encryption with configured trusted certificates for type: oauth authentication (no .spec.clusters[].authentication.tlsTrustedCertificates section in the KafkaConnect CR for the target cluster)

When the operands configured as described above are deployed with Strimzi >= 0.47.0 and <= 0.49.0, any code running within their Pods and using their Service Account for authentication will be able to GET any Kubernetes Secret from the same namespace. This can be done by executing 3rd party tools from the Pods. Or directly from the Kafka Connect code, for example, using configuration providers or HTTP connectors. The Pods are allowed to only GET the Secrets. They are not allowed to list, watch, modify, or delete the Secrets.

Patches

The issue is fixed in Strimzi 0.49.1.

Workarounds

There is no workaround for this issue when using the affected operands with the affected configurations.