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CKS Challenge 3

Take me to the lab!

Please note that the competition status for CKS Challenges is ended. Please do not submit a solution. It will not be scored.

Challenge

This is a two node kubernetes cluster. Using the kube-bench utility, identify and fix all the issues that were reported as failed for the controlplane and the worker node components.

Inspect the issues in detail by clicking on the icons of the interactive architecture diagram on the right and complete the tasks to secure the cluster. Once done click on the Check button to validate your work.

Click on each icon (in the lab) to see more details. Once done, click the Check button to test your work.

Diagram

Do the tasks in this order:

  1. kube-bench
    • Download kube-bench from AquaSec and extract it under /opt filesystem. Use the appropriate steps from the kube-bench docs to complete this task.
    • Run kube-bench with config directory set to /opt/cfg and /opt/cfg/config.yaml as the config file. Redirect the result to /var/www/html/index.html file.

    When this challenge was created, v0.6.2 of kube-bench was current, so we will download that version for best compatibility.

    1. Download and place under opt

      curl -L https://github.com/aquasecurity/kube-bench/releases/download/v0.6.2/kube-bench_0.6.2_linux_amd64.tar.gz | tar -xz -C /opt

    2. Run it

      1. Create directory for report

        mkdir -p /var/www/html

      2. Execute with given configuration instructions

        /opt/kube-bench --config-dir /opt/cfg --config /opt/cfg/config.yaml > /var/www/html/index.html

    Despite the fact that we redirected the output to index.html, the file content is text and can be inspected like this

    less /var/www/html/index.html
  2. kubelet (node)
    • Ensure that the --protect-kernel-defaults argument is set to true (node01)

    1. ssh to node01

      ssh node01

    2. Edit the kubelet configuration

      vi /var/lib/kubelet/config.yaml

    3. Add the following line to the end of the file

      protectKernelDefaults: true

    4. Save and exit vi, then restart kubelet

      systemctl restart kubelet

    5. Return to controlplane node

      exit
  3. kubelet (controlplane)
    • Ensure that the --protect-kernel-defaults argument is set to true (node01)

    Do exactly the same as above, but this time you don't need to ssh to anywhere first.

  4. kube-controller-mananger
    • Ensure that the --profiling argument is set to false

    1. Edit the manifest

      vi /etc/kubernetes/manifests/kube-controller-manager.yaml

    2. Add the following to the list of arguments in the command section of the pod spec:

          - --profiling=false

    3. Save and exit from vi. Controller manager pod will restart in a minute or so

  5. kube-scheduler
    • Ensure that the --profiling argument is set to false

    Do the exact same staps as above, but with /etc/kubernetes/manifests/kube-scheduler.yaml

  6. etcd
    • Correct the etcd data directory ownership

    1. View the report as discussed in the kube-bench section above, and find the FAIL at section 1.1.12

    2. Verify the data directory by checking the volumes section of the etcd pod static manifest for the hostPath.

    3. Correct the ownership as directed

      chown -R etcd:etcd /var/lib/etcd
  7. kube-apiserver
    • Ensure that the --profiling argument is set to false
    • Ensure PodSecurityPolicy admission controller is enabled
    • Ensure that the --insecure-port argument is set to 0
    • Ensure that the --audit-log-path argument is set to /var/log/apiserver/audit.log
    • Ensure that the --audit-log-maxage argument is set to 30
    • Ensure that the --audit-log-maxbackup argument is set to 10
    • Ensure that the --audit-log-maxsize argument is set to 100

    So this looks like a bunch of argument changes. Well it is, but there's a bit more work than that. If we tell the apiserver to open a log at a given directory, then that directory is expected to be on the host machine, i.e. controlplane itself. This means we also need to create a volume and volumeMount to satisfy this criterion, and also the host directory must exist.

    1. The directory into which the log file will go needs to exist first

       mkdir -p /var/log/apiserver

    2. Edit the manifest file

      vi /etc/kubernetes/manifests/kube-apiserver.yaml

    3. Put in all the new arguments

          - --profiling=false
    - --insecure-port=0
    - --audit-log-maxage=30
    - --audit-log-maxbackup=10
    - --audit-log-path=/var/log/apiserver/audit.log
    - --audit-log-maxsize=100

    4. Enable the admission controller, by appending PodSecurityPolicy to the --enable-admission-plugins argument so it looks like

          - --enable-admission-plugins=NodeRestriction,PodSecurityPolicy

    5. Create a volume for the log file (add to existing volumes)

        volumes:
  - hostPath:
      path: /var/log/apiserver/audit.log
      type: FileOrCreate
    name: audit-log

    6. Create a volumeMount for this volume (add to existing volumeMounts)

          volumeMounts:
    - mountPath: /var/log/apiserver/audit.log
      name: audit-log

    7. Save and exit vi. Wait up to a minute for api server to restart. Be aware of how to debug a crashed apiserver if you muck it up!

Automate the lab in a single script!

As DevOps engineers, we love everything to be automated!

Automation Script

Paste this entire script to the lab terminal, sit back and enjoy!
When the script completes, you can press the Check button and the lab will be complete!

{
start_time=$(date '+%s')

## kube-bench

# Install and run kube-bench
echo 'kube-bench'
curl -L https://github.com/aquasecurity/kube-bench/releases/download/v0.6.2/kube-bench_0.6.2_linux_amd64.tar.gz | tar -xz -C /opt
mkdir -p /var/www/html
/opt/kube-bench --config-dir /opt/cfg --config /opt/cfg/config.yaml > /var/www/html/index.html


## etcd
echo 'etcd'
chown -R etcd:etcd /var/lib/etcd

## kubelet
echo 'kubelet'
echo 'protectKernelDefaults: true' >> /var/lib/kubelet/config.yaml
systemctl restart kubelet
ssh node01 'echo "protectKernelDefaults: true" >> /var/lib/kubelet/config.yaml'
ssh node01 'systemctl restart kubelet'

## kube-controller-mananger
echo 'kube-controller-mananger'
yq -i e '.spec.containers[0].command += "--profiling=false"' /etc/kubernetes/manifests/kube-controller-manager.yaml

## kube-scheduler
echo 'kube-scheduler'
yq -i e '.spec.containers[0].command += "--profiling=false"' /etc/kubernetes/manifests/kube-scheduler.yaml

## kube-apiserver
echo 'kube-apiserver'
# Create audit log path
mkdir -p /var/log/apiserver

# Patch api-server
yq e '.spec.containers[0].command += [
    "--profiling=false",
    "--insecure-port=0",
    "--audit-log-maxage=30",
    "--audit-log-maxbackup=10",
    "--audit-log-path=/var/log/apiserver/audit.log",
    "--audit-log-maxsize=100"
    ] |
    .spec.volumes += {"name": "audit-log", "hostPath":{"path":"/var/log/apiserver/audit.log", "type":"FileOrCreate"}} |
    .spec.containers[0].volumeMounts += {"mountPath": "/var/log/apiserver/audit.log", "name": "audit-log"}' \
    /etc/kubernetes/manifests/kube-apiserver.yaml | \
  sed 's/NodeRestriction/NodeRestriction,PodSecurityPolicy/' > \
  kube-apiserver.yaml.out

# Save current API server container ID
api_container_id=$(crictl ps | grep apiserver | cut -f 1 -d ' ')

mv -f kube-apiserver.yaml.out /etc/kubernetes/manifests/kube-apiserver.yaml

# Kick kubelet - I have seen it not notice the manifest change here.
systemctl restart kubelet

# Shut up warnings from crictl
crictl config \
  --set runtime-endpoint=unix:///var/run/dockershim.sock \
  --set image-endpoint=unix:///var/run/dockershim.sock

# Wait for API server restart (gets a new container ID)
new_id=''

while [ -z "$new_id" -o "$api_container_id" = "$new_id" ]
do
    sleep 2
    new_id=$(crictl ps | grep apiserver | cut -f 1 -d ' ')
    echo "API server container id is $new_id"
done

sleep 5

kubectl get pods -n kube-system

end_time=$(date '+%s')
duration=$(( end_time - start_time ))
echo "Complete in ${duration}s"
}