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Kubernetes CTF

These are all resource that are used to setup the Kubernetes Easter CTF. The CTF was hosted on http://k8s-ctf.rocks/ and ended with the end of eastern. The CTF itself was hosted on Amazon EKS. This repository contains a Vagrantfile (for HashiCorp Vagrant) that allows you to setup the CTF locally. There might be some parts undocumented or not perfectly working, that I forgot to document. Feel free to reach out and we can fix it! :-)

Setup

Setup with Vagrant

To simplify the Installation, a Vagrantfile is supplied to bootstraps the CTF local on an Ubuntu VM + k3s

You can start it with:

vagrant up

Even if the VM is started, the cluster needs some time to pull all images. The status of the deployment can be checked with following commands:

# Connect to vm
vagrant ssh

# Get status of pods
kubectl get pods --all-namespaces

As soon as the Status is Running or Completed the cluster can be accessed on http://localhost:8080.

Configuration

Most of the configurations can be in adjusted in the config config. The vagrant setup depends on k3s and needs according to the documentation some manual adjustment of the calico deployment.

Install k3s

In case you want to deploy it on an existing maschine, k3s can installed as following-

. ./config
curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="--cluster-cidr=$POD_SUBNET --service-cidr=$SVC_SUBNET --write-kubeconfig-mode=644 --no-flannel" sudo -E sh -
sleep 5
kubectl apply -f calico.yaml
mkdir -p ~/.kube
ln -s /etc/rancher/k3s/k3s.yaml ~/.kube/config

Install Helm

The Kubernetes resources are written in Helm 3 Charts. Following commands are necessary to install Helm 3.

curl -fsSL -o ~/get_helm.sh https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3
chmod 700 ~/get_helm.sh
~/get_helm.sh
rm ~/get_helm.sh
helm repo add stable https://kubernetes-charts.storage.googleapis.com/

Deploy CTF

The CTF can as well deployed with Helm 3 to an existing cluster with the following command.

./install-with-helm.sh

And don't forget to adjust the configuration in the config.

Docker Images

The Dockerfiles are stored in the docker-images directory. The images are build automatically by GitHub Actions and published on Docker Hub:

Fixed issues

  • Helm 3 stores all details about the different deployments in the Kubernetes Secrets. Since I stored one EGG in the kubernetes Secret API, the Helm secrets were as well available. According to Issue #6409 you can decode the complete deployment with 2x base64 decode + gunzp (kubectl get secrets <helm-deployment> -o json | jq .data.release -r | base64 --decode | base64 --decode | gunzip -) and all the Kubernetes magic was gone. xD I deleted the Secrets during the CTF manually to avoid the info leak. For now, I relocated the Helm meta info to another namespace.
  • I deployed Datadog Cloud Monitoring for the very first time on a cluster. It is nice as an operator to have fancy charts and stats, to name an advantage. Another advantage was for the CTF participants was the service kube-state-metrics, which exposed the whole log of my overall deployment. After deploying an additional NetworPolicy, the service was not anymore available.