<p>I am creating a Pod Security Policy to stop ALL users from creating a Pod as Root user. My cluster is on GKE.
The steps Ive carried out till now are</p>

<p>1) Enable PodSecurityPolicy in my cluster</p>

<pre><code>gcloud beta container clusters update standard-cluster-11  --enable-pod-security-policy
</code></pre>

<p>2) Define the Policy. The policy is simple and restricts root user.</p>

<pre><code>apiVersion: extensions/v1beta1
kind: PodSecurityPolicy
metadata:
  name: a-restrict-root
spec:
  privileged: false
  runAsUser:
    rule: MustRunAsNonRoot  # &lt;------ Root user restricted.
  seLinux:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  volumes:
  - '*'
</code></pre>

<p>3) And then ofcourse implementing the correct RBAC rules so that it can be implemented for ALL users.</p>

<pre><code>apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: gce:podsecuritypolicy:a-restrict-root
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/cluster-service: "true"
rules:
- apiGroups:
  - policy
  resourceNames:
  - a-restrict-root
  resources:
  - podsecuritypolicies
  verbs:
  - use
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: gce:podsecuritypolicy:a-restrict-root
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/cluster-service: "true"
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: gce:podsecuritypolicy:a-restrict-root
subjects:
- kind: Group
  apiGroup: rbac.authorization.k8s.io
  name: system:serviceaccounts
</code></pre>

<p>Now comes the part where I try to spin up a Pod. The pod definition looks like this :</p>

<pre><code>apiVersion: v1
kind: Pod
metadata:
  name: security-context-demo
spec:
  securityContext:
    runAsUser: 0
    fsGroup: 0
  volumes:
  - name: sec-ctx-vol
    emptyDir: {}
  containers:
  - name: sec-ctx-demo
    image: gcr.io/google-samples/node-hello:1.0
    volumeMounts:
    - name: sec-ctx-vol
      mountPath: /data/demo
    securityContext:
      allowPrivilegeEscalation: false
</code></pre>

<p>As you can see, the <code>runAsUser</code> is set to <code>0</code> meaning <code>root</code>.</p>

<p>When I run <code>kubectl create -f pod.yaml</code>, the pod is creating and goes into <code>Running</code> state.</p>

<p>When I exec into the Pod, I can see all process running as root</p>

<pre><code>$ kubectl exec -it security-context-demo -- sh
# ps aux
USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root           1  0.0  0.0   4336   812 ?        Ss   19:25   0:00 /bin/sh -c node server.js
root           6  0.4  0.5 772124 22656 ?        Sl   19:25   0:00 node server.js
root          11  0.0  0.0   4336   724 ?        Ss   19:26   0:00 sh
root          16  0.0  0.0  17500  2072 ?        R+   19:26   0:00 ps aux
</code></pre>

<p>But based on my PodSecurityPolicy this should NOT be allowed. Is there something I have missed ? </p>

<p><strong>UPDATE :</strong></p>

<p>I spun up a default nginx pod that I know always starts as root user. Its manifest is :</p>

<pre><code>apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx
</code></pre>

<p>And when I create it, it too starts up successfully.</p>

<pre><code>$ kubectl get po
NAME                    READY     STATUS    RESTARTS   AGE
nginx                   1/1       Running   0          2m
</code></pre>

<p>Whereas because of the PSP, it should not start up.</p>

<p>If you fetch the created pod from the API, it will contain an annotation indicating which PSP allowed the pod. I expect a different PSP is in place which allows the pod</p>
