Use Cloudflare Tunnels with Kubernetes client-go credential plugins

This tutorial explains how to use Cloudflare Tunnels with Kubernetes client-go credential plugins for authentication. By following these steps, you can securely access your Kubernetes cluster through a Cloudflare Tunnel using the kubectl command-line tool.

• A Cloudflare account
• The Cloudflare Tunnel client (cloudflared) installed on your machine
• Access to a Kubernetes cluster
• kubectl installed on your machine

1. Authenticate cloudflared with your Cloudflare account:

   cloudflared tunnel login

2. Create a new tunnel:

   cloudflared tunnel create k8s-tunnel

3. Configure your tunnel by creating a configuration file named config.yml:

   tunnel: <TUNNEL_ID>
   credentials-file: /path/to/credentials.json
   ingress:
     - hostname: k8s.example.com
       service: tcp://kubernetes.default.svc.cluster.local:443
     - service: http_status:404

   Replace <TUNNEL_ID> with your tunnel ID and adjust the hostname as needed.

4. Start the tunnel:

   cloudflared tunnel run k8s-tunnel

Ensure your Kubernetes API server is configured to accept authentication from Cloudflare Tunnels. This may involve setting up an authentication webhook or configuring the API server to trust the Cloudflare Tunnel's client certificates.

1. Create a script named cloudflare-k8s-auth.sh with the following content:

   #!/bin/bash
   
   echo '{
     "apiVersion": "client.authentication.k8s.io/v1beta1",
     "kind": "ExecCredential",
     "status": {
       "token": "'"$(cloudflared access token -app=https://k8s.example.com)"'"
     }
   }'

   Make the script executable:

   chmod +x cloudflare-k8s-auth.sh

2. Update your ~/.kube/config file to use the credential plugin:

   apiVersion: v1
   kind: Config
   clusters:
     - cluster:
         server: https://k8s.example.com
       name: cloudflare-k8s
   users:
     - name: cloudflare-user
       user:
         exec:
           apiVersion: client.authentication.k8s.io/v1beta1
           command: /path/to/cloudflare-k8s-auth.sh
           interactiveMode: Never
   contexts:
     - context:
         cluster: cloudflare-k8s
         user: cloudflare-user
       name: cloudflare-k8s-context
   current-context: cloudflare-k8s-context

Now you can use kubectl commands as usual. The client-go credential plugin will automatically handle authentication through the Cloudflare Tunnel:

kubectl get pods

If you encounter issues:

• Ensure cloudflared is running and the tunnel is active
• Check that your ~/.kube/config file is correctly configured
• Verify that the Kubernetes API server is properly set up to accept authentication from Cloudflare Tunnels
• Review the Cloudflare Tunnel logs for any error messages

For more information, refer to the Cloudflare Tunnels documentation and the Kubernetes client-go credential plugins documentation ↗.