vcluster on OpenShift

See also https://github.com/loft-sh/vcluster/issues/171

Notes

• Images do not run properly as non-root - workaround with multiple emptyDir mounts.
• Default K3s CoreDNS deployment doesn't work on OpenShift Host Cluster -> Custom deployment in in-cluster/coredns.yaml.

Installation

• Create OpenShift Project
• Create vcluster: vcluster create vcluster-1 -n tobru-vcluster-poc -f values.yaml
• Get kubeconfig: oc get secret vc-vcluster-1 --template={{.data.config}} | base64 -d > kubeconfig.yaml
• Get CA for re-encryption of Route: kubectl --kubeconfig=$(pwd)/kubeconfig.yaml config view -o jsonpath='{.clusters[].cluster.certificate-authority-data}' --flatten | base64 -d
• Edit host-cluster/route.yaml, include the retrieved CA and install the route: oc apply -f host-cluster/route.yaml
• Remove CA (we're using Let's Encrypt): kubectl --kubeconfig=$(pwd)/kubeconfig.yaml config unset clusters.local.certificate-authority-data
• Set kubeconfig: export KUBECONFIG=$(pwd)/kubeconfig.yaml
• Install custom CoreDNS in vcluster: kubectl apply -f in-cluster/coredns.yaml
• Configure OIDC: kubectl config set-credentials ... (see below)

OIDC Authentication

• Blog: https://aaron-pejakovic.medium.com/kubernetes-authenticating-to-your-cluster-using-keycloak-eba81710f49b
• K8s Docs: https://kubernetes.io/docs/reference/access-authn-authz/authentication/#openid-connect-tokens
• kubectl plugin: https://github.com/int128/kubelogin

vcluster config

vcluster:
  baseArgs:
[...]
    - --kube-controller-manager-arg=controllers=*,-nodeipam,-nodelifecycle,-persistentvolume-binder,-attachdetach,-persistentvolume-expander,-cloud-node-lifecycle
    - --kube-apiserver-arg=oidc-client-id=tobru-vcluster-test
    - --kube-apiserver-arg=oidc-groups-claim=groups
    - --kube-apiserver-arg=oidc-issuer-url=https://id.dev.appuio.cloud/auth/realms/appuio-cloud-dev
    - --kube-apiserver-arg=oidc-username-claim=email

kubectl plugin

# kubectl oidc-login setup --oidc-issuer-url=https://id.dev.appuio.cloud/auth/realms/appuio-cloud-dev --oidc-client-id=tobru-vcluster-test --oidc-client-secret=63410f24-0721-447b-a290-4b0169c414e0
authentication in progress...

## 2. Verify authentication

You got a token with the following claims:

{
  "exp": 000,
  "iat": 000,
  "auth_time": 000,
  "jti": "XXX",
  "iss": "https://id.dev.appuio.cloud/auth/realms/appuio-cloud-dev",
  "aud": "tobru-vcluster-test",
  "sub": "UUID",
  "typ": "ID",
  "azp": "tobru-vcluster-test",
  "nonce": "XXX",
  "session_state": "XXX",
  "at_hash": "XXX",
  "acr": "1",
  "sid": "XXX",
  "email_verified": true,
  "name": "Tobias Brunner",
  "groups": [
    "admin"
  ],
  "preferred_username": "tobias.brunner",
  "given_name": "Tobias",
  "family_name": "Brunner",
  "email": "tobias.brunner@vshn.net"
}

## 3. Bind a cluster role

Run the following command:

        kubectl create clusterrolebinding oidc-cluster-admin --clusterrole=cluster-admin --user='XXX'

## 4. Set up the Kubernetes API server

Add the following options to the kube-apiserver:

        --oidc-issuer-url=https://id.dev.appuio.cloud/auth/realms/appuio-cloud-dev
        --oidc-client-id=tobru-vcluster-test

## 5. Set up the kubeconfig

Run the following command:

        kubectl config set-credentials oidc \
          --exec-api-version=client.authentication.k8s.io/v1beta1 \
          --exec-command=kubectl \
          --exec-arg=oidc-login \
          --exec-arg=get-token \
          --exec-arg=--oidc-issuer-url=https://id.dev.appuio.cloud/auth/realms/appuio-cloud-dev \
          --exec-arg=--oidc-client-id=tobru-vcluster-test \
          --exec-arg=--oidc-client-secret=63410f24-0721-447b-a290-4b0169c414e0

## 6. Verify cluster access

Make sure you can access the Kubernetes cluster.

        kubectl --user=oidc get nodes

You can switch the default context to oidc.

        kubectl config set-context --current --user=oidc

You can share the kubeconfig to your team members for on-boarding.

# kubectl --kubeconfig ./kubeconfig.yaml config set-credentials oidc \
  --exec-api-version=client.authentication.k8s.io/v1beta1 \
  --exec-command=kubectl \
  --exec-arg=oidc-login \
  --exec-arg=get-token \
  --exec-arg=--oidc-issuer-url=https://id.dev.appuio.cloud/auth/realms/appuio-cloud-dev \
  --exec-arg=--oidc-client-id=tobru-vcluster-test \
  --exec-arg=--oidc-client-secret=63410f24-0721-447b-a290-4b0169c414e0
# kubectl --kubeconfig ./kubeconfig.yaml --user=oidc get po -A

Keycloak client

• "Access Type" confidential
• Valid Redirect URIs: http://localhost:18000 http://localhost:8000 (they are for the kubelogin plugin)