Skip to main content
Version: 21.11

Configuring Redpanda mTLS authentication on Kubernetes

This document provides details on how to enable mutual Transport Layer Security (mTLS) authentication on Kubernetes. mTLS authenticates the server and encrypts communication between the server and client, as one-way TLS does, and also authenticates the client.

For information about Redpanda authentication on Kubernetes in general, see the Redpanda security on Kubernetes document. You’ll find information there about supported authentication methods for each API.

Redpanda supports mTLS authentication on all four APIs:

  • Kafka API
  • HTTP Proxy (formerly Pandaproxy)
  • Schema Registry
  • Admin API

The steps below show you how to:

  1. Create the cluster specification file
  2. Optionally, configure external connectivity
  3. Optionally, provide an issuer or certificate
  4. Create the Redpanda cluster
  5. Create the ConfigMap
  6. Configure the Pod
  7. Create the Pod
  8. Connect to Redpanda
  9. Clean up

For a quick tutorial, the steps below contain Tutorial: Triceratops sections that have commands that you can copy and paste to enable mTLS authentication. To use the tutorial, just follow the steps below.

caution

Redpanda does not perform user authentication on the client certificate. Because Redpanda does not associate the distinguished name (DN) in the client certificate with a Redpanda principal, you cannot distinguish between users when using mTLS. You can use mTLS with multiple users, but from Redpanda’s point of view, the users are identical.

Prerequisites

This guide assumes that you have already completed the following tasks:

  1. Configured the kubectl context
  2. Installed cert-manager
  3. Installed the Redpanda operator

If you haven’t completed these tasks, you can use one of the following quickstarts to get set up before you configure mTLS. Just follow the steps in any of these guides and stop before you install and connect to the Redpanda cluster:

Step 1: Create the cluster specification file

The Redpanda GitHub repository contains an mtls.yaml example configuration file that you can use to enable mTLS authentication. You can find the file here:

redpanda-examples../../example-config/kubernetes/mtls.yaml

note

If you want to modify the example file, save it locally and make the required changes listed below. If you’re following along with the triceratops tutorial or if you don’t need to make changes to the example file, you don’t need to save the file locally.

The text below is the Redpanda mtls.yaml file with the relevant sections highlighted:

 apiVersion: redpanda.vectorized.io/v1alpha1
kind: Cluster
metadata:
name: cluster-sample-mtls
spec:
image: "vectorized/redpanda"
version: "latest"
replicas: 1
resources:
requests:
cpu: 1
memory: 1.2G
limits:
cpu: 1
memory: 1.2G
configuration:
rpcServer:
port: 33145
kafkaApi:
- port: 9092
tls:
enabled: true
requireClientAuth: true
pandaproxyApi:
- port: 8082
tls:
enabled: true
requireClientAuth: true
schemaRegistry:
port: 8081
tls:
enabled: true
requireClientAuth: true
adminApi:
- port: 9644
tls:
enabled: true
requireClientAuth: true
developerMode: true

Complete these steps to configure the cluster specification file. The steps reference the highlighted lines in the file above:

  1. Configure the cluster name. The following property in the file above is the name of the cluster. Change this value to the name of your cluster:
metadata:
name: cluster-sample-mtls
  1. Enable mTLS for each API individually. You can enable mTLS on one or more of the APIs. In the example above, all four APIs have mTLS enabled:
kafkaApi:
- port: 9092
tls:
enabled: true
requireClientAuth: true
pandaproxyApi:
- port: 8082
tls:
enabled: true
requireClientAuth: true
schemaRegistry:
port: 8081
tls:
enabled: true
requireClientAuth: true
adminApi:
- port: 9644
tls:
enabled: true
requireClientAuth: true

Tutorial: Triceratops

If you want to follow along with the triceratops example, you do not need to do anything for this step. Take note of the contents of the file, but you don’t need to modify it or save it locally.

Step 2: Optionally, configure external connectivity

You can specify up to two listeners for each API, but only one listener can have mTLS enabled. If you do have two listeners, one must be internal and one must be external. The exception is Schema Registry. The Schema Registry listener can be internal, or it can be an internal port that is used internally and externally. If you enable external connectivity on Schema Registry, the Kubernetes node port connects to the internal Redpanda port to provide external connectivity.

To enable external connectivity with mTLS, add the following lines to each API in the configuration file that you created in Step 1:

 - external:
enabled: true
subdomain: <subdomain_name>

The subdomain field allows you to specify the advertised address of the external listener. The subdomain addresses, including the brokers, must be registered with a DNS provider, such as Amazon Route 53. You only need to include the subdomain name in this field, not the brokers. Each API in the configuration file must have the same subdomain specified.

The external port is generated automatically and you do not need to specify it. In the example below, mTLS is enabled on the external listener for the Kafka API. Enable external connectivity the same way for Admin API and HTTP Proxy.

kafkaApi:
- port: 9092
- external:
enabled: true
subdomain: <subdomain_name>
tls:
enabled: true
requireClientAuth: true

The Schema Registry syntax is slightly different in that the ports are not a list. You can specify one internal port and one external port. Schema Registry always uses an internal port and with external connectivity configured, the Kubernetes node port connects to the internal Redpanda port. Configure mTLS with external connectivity for Schema Registry like this:

schemaRegistry:
port: 8081
external:
enabled: true
subdomain: <subdomain_name>
tls:
enabled: true
requireClientAuth: true

For more information about external connectivity, including subdomains, see the External connectivity section of the Redpanda security on Kubernetes documentation.

Tutorial: Triceratops

The triceratops tutorial does not use external connectivity, so you do not have to do anything for this step.

Step 3: Optionally, provide an issuer or certificate

Kafka API and Schema Registry allow you to provide a certificate issuer or certificate for the node certificate.

When you enable mTLS, the Redpanda operator generates a root certificate for each API. The root certificate is local to the cluster and the operator uses the root certificate to generate leaf certificates for the nodes and the client. However, for Kafka API and Schema registry you can instead specify a certificate issuer or a certificate.

For information about how certificates are created and used in Redpanda, see the Certificates section of the Redpanda security on Kubernetes document.

Provide an issuer

To provide a certificate issuer, add the issuerRef property to the cluster specification file that you created in the previous step. For information about issuers, see the cert-manager Issuer documentation.

You can provide an issuer for kafkaAPI or schemaRegistry in the same way. The example here is the kafkaAPI configuration configuration with the issuerRef property highlighted:

kafkaApi:
- port: 9092
tls:
enabled: true
issuerRef:
name: <issuer_name>
kind: <issuer>
requireClientAuth: true

The issuerRef property contains the following variables:

  • issuer_name - The name of the issuer or cluster issuer.
  • issuer - A Kubernetes resource that represents a certificate authority. The value of this property can be Issuer or ClusterIssuer. If the kind property is not set, or if it is set to Issuer, an issuer with the name specified in the name property that exists in the same namespace as the certificate will be used.

Provide a certificate

You can provide a certificate as a Secret by adding the nodeSecretRef property to the cluster specification file that you created above. For information about Secrets, see the Kubernetes Secrets documentation. The cert-manager Certificate documentation contains detailed information about certificates, including a diagram of the certificate lifecycle.

You can provide a certificate for kafkaAPI or schemaRegistry in the same way. The example here is the kafkaAPI configuration with the nodeSecretRef property highlighted:

kafkaApi:
- port: 9092
tls:
enabled: true
nodeSecretRef:
name: <secret_name>
namespace: <secret_namespace>
requireClientAuth: true

The nodeSecretRef property contains the following variables:

  • secret_name - Name of the certificate secret.
  • secret_namespace - The Kubernetes namespace where the certificate secret is. If the secret is in a different namespace than the Redpanda cluster, the operator copies it to the namespace of the Redpanda cluster.

Tutorial: Triceratops

The triceratops tutorial uses the certificates generated by cert-manager, so you do not have to do anything for this step.

Step 4: Create the Redpanda cluster

After you configure the cluster specification file, you must run the kubectl apply command to create the cluster. You can run the command using a path to the cluster specification file on your local machine or you can use the URL to the mtls.yaml file above.

If you modified the file in the previous step, you will have the file saved locally. Run this command to create the Redpanda cluster:

kubectl apply -f <cluster_specification.yaml>

If you did not modify the example file, you can use the URL to the example file in GitHub to create the cluster:

kubectl apply -f https://raw.githubusercontent.com/redpanda-data/redpanda-examples/main/docs/example-config/kubernetes/mtls.yaml

Tutorial: Triceratops

To create the cluster for the triceratops tutorial, run this command:

kubectl apply -f https://raw.githubusercontent.com/redpanda-data/redpanda-examples/main/docs/example-config/kubernetes/mtls.yaml

Step 5: Create the ConfigMap

Create a yaml file that will hold the configuration for mTLS, including the location of the public certificate. In the next step, you will create the Pod, which will consume this ConfigMap. This will allow you to run rpk commands with mTLS authentication.

info

The Kubernetes ConfigMaps documentation has everything you ever wanted to know about ConfigMaps.

  1. Copy the text below and save it locally as a yaml file, such as mtls_config_map.yaml.
apiVersion: v1
kind: ConfigMap
metadata:
name: <ConfigMap_name>
data:
redpanda.yaml: |
redpanda:
rpk:
kafka_api:
brokers:
- <cluster_name>-0.<cluster_name>.default.svc.cluster.local:9092
tls:
key_file: <key_file_path>/tls.key
cert_file: <cert_file_path>/tls.crt
truststore_file: <truststore_file_path>/ca.crt
  1. In the file that you just saved, configure these variables:
    • ConfigMap_name - Name of the ConfigMap. This can be any string. This is what you will use to reference the ConfigMap in the next step when you configure the Pod.
    • cluster_name - The name of the Redpanda cluster that you defined in the cluster specification file.
    • key_file_path - The directory where you want to mount the tls.key private client key. Generally this is /etc/tls/certs.
    • cert_file_path - The filename and directory where you want to mount the tls.crt private key. Generally this is /etc/tls/certs.
    • truststore_file_path - The directory where you want to mount the ca.crt file. Generally this is /etc/tls/certs/ca.
  2. Save the file.

External connectivity

If you are configuring mTLS with external connectivity, you must configure the brokers accordingly. Replace the brokers property in the example file with this:

brokers: 
- 0.<subdomain_name>.:<node_port>

Configure the following variables in the brokers property:

  • subdomain_name - The name of the subdomain that you included in the cluster specification file in Step 1.
  • node_port - The Kafka API external port. Unless you included this in the cluster specification file, this port is autogenerated by Kubernetes.

Tutorial: Triceratops

If you're following along with the triceratops tutorial, save the following text locally as a file called triceratops_config.yaml:

apiVersion: v1
kind: ConfigMap
metadata:
name: triceratops-config
data:
redpanda.yaml: |
redpanda:
rpk:
brokers:
- cluster-sample-mtls-0.cluster-sample-mtls.default.svc.cluster.local:9092
tls:
key_file: /etc/tls/certs/tls.key
cert_file: /etc/tls/certs/tls.crt
truststore_file: /etc/tls/certs/ca/ca.crt

Step 6: Configure the Pod

The Pod is the process that consumes the ConfigMap that you created in the previous step. This Pod runs the Redpanda image in order to run rpk, which is part of the Redpanda image.

info

For everything you ever wanted to know about Pods, see the Kubernetes Pods documentation.

  1. Copy the text below and save it locally as a yaml file, such as mtls_pod.yaml.
apiVersion: v1
kind: Pod
metadata:
name: <pod_name>
spec:
containers:
- name: rpk
image: 'vectorized/redpanda:<redpanda-version>'
command:
- /bin/bash
- '-c'
args:
- sleep infinity
volumeMounts:
- mountPath: <key_file_path>
name: <tls_volume_name>
- mountPath: <truststore_file_path>
name: <ca_volume_name>
- mountPath: /etc/redpanda
name: <rpk_volume_name>
restartPolicy: Never
volumes:
- name: <tls_volume_name>
secret:
secretName: <cluster_name>-user-client
- name: <ca_volume_name>
secret:
secretName: <cluster_name>-redpanda
- name: <rpk_volume_name>
configMap:
name: <configMap_name>
  1. In the file that you just saved, configure these variables:
    • pod_name - Name of the Pod. This is the Pod that will run rpk. This can be any string.
    • args - Specifies what you want the Pod to do. You can execute rpk commands here. This example uses the sleep infinity argument, which tells the Pod to keep running so that you can execute as many rpk commands as you want from the command line.
  2. Configure the volumeMounts properties. There are three of these; one for tls, one for ca, and one for rpk.
    • tls - The path and the name of the tls.crt and tls.key volume mount.
      • key_file_path - The same path that you specified in the key_file_path and cert_file_path properties in the ConfigMap. Generally this is /etc/tls/certs.
      • tls_volume_name - Must match the tls_volume_name in the volumeMounts property.
    • ca - The path and the name of the ca.crt volume mount.
      • truststore_file_path - The same path that you specified in the truststore_file_path property in the ConfigMap. Generally this is /etc/tls/certs/ca.
      • ca_volume_name - Can be any string, but it must match the ca_volume_name in the volumes property of this file.
    • rpk - The path and the name of the rpk volume mount.
      • name - Can be any string, but it must match the rpk_volume_name in the volumes property of this file.
  3. Configure the volumes properties. There are three of these; one for tls, one for ca, and one for rpk.
    • tls - The name and Secret of the tls.crt and tls.key volume mount.
      • tls_volume_name - Must be the same as the tls_volume_name in the volumeMounts property of this file.
      • cluster_name - The cluster name that you defined in the cluster specification file in Step 1. The secretName property specifies the name of the client Secret. For the Kafka API, this is <cluster_name>-user-client.
    • ca - The name and Secret of the ca.crt volume mount.
      • name - Must be the same as the ca_volume_name in the volumeMounts property.
      • cluster_name - The cluster name that you defined in the cluster specification file in Step 1. The secretName property specifies the name of the node Secret. For the Kafka API, this is <cluster_name>-redpanda.
    • rpk - The volume name and ConfigMap name of the rpk volume mount.
      • rpk_volume_name - Must match the <rpk_volume_name> in the volumeMounts property of this file.
      • configMap_name - The ConfigMap name that you specified in the name property of the ConfigMap in the previous step.
  4. Configure the <redpanda-version> variable. Add a Redpanda version, such as v21.11.11. You can find all the Redpanda version tags in the Redpanda Docker Hub repository.
  5. Save the file.

Tutorial: Triceratops

To follow along with the triceratops tutorial, save the following text locally as a file called triceratops_pod.yaml:

apiVersion: v1
kind: Pod
metadata:
name: triceratops_pod
spec:
containers:
- name: rpk
image: 'vectorized/redpanda:latest'
command:
- /bin/bash
- '-c'
args:
- sleep infinity
volumeMounts:
- mountPath: /etc/tls/certs
name: tls_volume
- mountPath: /etc/tls/certs/ca
name: ca_volume
- mountPath: /etc/redpanda
name: rpk_volume
restartPolicy: Never
volumes:
- name: tls_volume
secret:
secretName: cluster-sample-mtls-user-client
- name: ca_volume
secret:
secretName: cluster-sample-mtls-redpanda
- name: rpk_volume
configMap:
name: triceratops-config

Step 7: Create the Pod

Run the following command to create the pod:

kubectl apply -f <mtls_pod.yaml>

Tutorial: Triceratops

To create the Pod for the triceratops tutorial, run this command:

kubectl apply -f triceratops_pod.yaml

Step 8: Connect to Redpanda

Now that you have mTLS enabled and the Pod created, you can start using rpk to interact with Redpanda. Note that each time you execute an rpk command, rpk establishes a connection and authenticates the server and the server authenticates the client.

  1. Create a topic with this command:
kubectl exec <pod_name> -- rpk topic create <topic_name> 

The command contains the following variables:

  • pod_name - The Pod name that you specified in the Pod configuration file.
  • topic_name - The name of the topic that you're creating with this command.
  1. This command will describe the topic:
kubectl exec <pod_name> -- rpk topic describe <topic_name> 
note

You do not need to specify the brokers in these commands because they were defined in the ConfigMap. If you include brokers in the rpk commands, it will override the brokers in the ConfigMap.

Tutorial: Triceratops

  1. For the triceratops tutorial, run this command to create a topic called triceratops_topic:
kubectl exec triceratops_pod -- rpk topic create triceratops_topic 
  1. And this command will describe the topic:
kubectl exec triceratops_pod -- rpk topic describe triceratops_topic 

Step 9: Clean up

You can use the rpk commands documentation to start producing and consuming to your cluster.

When you're ready, delete your cluster and configuration files with the following command:

kubectl delete -f <cluster_specification.yaml> -f <mtls_config_map.yaml> -f <mtls_pod.yaml>

Tutorial: Triceratops

Use the rpk commands documentation to experiment with producing and consuming to your cluster. When you're ready, delete the cluster and configuration files with this command:

kubectl delete -f https://raw.githubusercontent.com/redpanda-data/redpanda-examples/main/docs/example-config/kubernetes/mtls.yaml triceratops_config.yaml triceratops_pod.yaml