Restricted PSS Profile

Finally we can take a look at the Restricted profile, which is the most heavily restricted policy following current Pod hardening best practices. Add labels to the assets namespace to enable all PSA modes for the Restricted PSS profile:

Kustomize Patch

~/environment/eks-workshop/modules/security/pss-psa/restricted-namespace/namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: assets
  labels:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/warn: restricted

Namespace/assets

apiVersion: v1
kind: Namespace
metadata:
  labels:
    app.kubernetes.io/created-by: eks-workshop
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/warn: restricted
  name: assets

Diff

 kind: Namespace
 metadata:
   labels:
     app.kubernetes.io/created-by: eks-workshop
+    pod-security.kubernetes.io/audit: restricted
+    pod-security.kubernetes.io/enforce: restricted
+    pod-security.kubernetes.io/warn: restricted
   name: assets

Run Kustomize to apply this change to add labels to the assets namespace:

~$kubectl apply -k ~/environment/eks-workshop/modules/security/pss-psa/restricted-namespace

Warning: existing pods in namespace "assets" violate the new PodSecurity enforce level "restricted:latest"

Warning: assets-d59d88b99-flkgp: allowPrivilegeEscalation != false, runAsNonRoot != true, seccompProfile

namespace/assets configured

serviceaccount/assets unchanged

configmap/assets unchanged

service/assets unchanged

deployment.apps/assets unchanged

Similar to the Baseline profile we're getting a warning that the assets Deployment is violating the Restricted profile.

~$kubectl -n assets delete pod --all

pod "assets-d59d88b99-flkgp" deleted

The Pods aren't re-created:

~$kubectl -n assets get pod

No resources found in assets namespace.

The above output indicates that PSA did not allow creation of Pods in the assets Namespace, because the Pod security configuration violates Restricted PSS profile. This behaviour is same as what we saw earlier in the previous section.

In the case of the Restricted profile we actually need to proactively lock down some of the security configuration to meet the profile. Let's add some security controls to the Pod configuration to make it compliant with the Privileged PSS profile configured for the assets namespace:

Kustomize Patch

~/environment/eks-workshop/modules/security/pss-psa/restricted-workload/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: assets
spec:
  template:
    spec:
      containers:
        - name: assets
          securityContext:   
            runAsNonRoot: true
            runAsUser: 999
            allowPrivilegeEscalation: false
            seccompProfile:
              type: RuntimeDefault

Deployment/assets

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app.kubernetes.io/created-by: eks-workshop
    app.kubernetes.io/type: app
  name: assets
  namespace: assets
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/component: service
      app.kubernetes.io/instance: assets
      app.kubernetes.io/name: assets
  template:
    metadata:
      annotations:
        prometheus.io/path: /metrics
        prometheus.io/port: "8080"
        prometheus.io/scrape: "true"
      labels:
        app.kubernetes.io/component: service
        app.kubernetes.io/created-by: eks-workshop
        app.kubernetes.io/instance: assets
        app.kubernetes.io/name: assets
    spec:
      containers:
        - envFrom:
            - configMapRef:
                name: assets
          image: public.ecr.aws/aws-containers/retail-store-sample-assets:0.4.0
          imagePullPolicy: IfNotPresent
          livenessProbe:
            httpGet:
              path: /health.html
              port: 8080
            periodSeconds: 3
          name: assets
          ports:
            - containerPort: 8080
              name: http
              protocol: TCP
          resources:
            limits:
              memory: 128Mi
            requests:
              cpu: 128m
              memory: 128Mi
          securityContext:
            allowPrivilegeEscalation: false
            capabilities:
              drop:
                - ALL
            readOnlyRootFilesystem: false
            runAsNonRoot: true
            runAsUser: 999
            seccompProfile:
              type: RuntimeDefault
          volumeMounts:
            - mountPath: /tmp
              name: tmp-volume
      securityContext: {}
      serviceAccountName: assets
      volumes:
        - emptyDir:
            medium: Memory
          name: tmp-volume

Diff

             requests:
               cpu: 128m
               memory: 128Mi
           securityContext:
+            allowPrivilegeEscalation: false
             capabilities:
               drop:
                 - ALL
             readOnlyRootFilesystem: false
+            runAsNonRoot: true
+            runAsUser: 999
+            seccompProfile:
+              type: RuntimeDefault
           volumeMounts:
             - mountPath: /tmp
               name: tmp-volume
       securityContext: {}

Run Kustomize to apply these changes, which we re-create the Deployment:

~$kubectl apply -k ~/environment/eks-workshop/modules/security/pss-psa/restricted-workload

namespace/assets unchanged

serviceaccount/assets unchanged

configmap/assets unchanged

service/assets unchanged

deployment.apps/assets configured

Now, Run the below commands to check PSA allows the creation of Deployment and Pod with the above changes in the the assets namespace:

~$kubectl -n assets get pod

NAME                     READY   STATUS    RESTARTS   AGE

assets-8dd6fc8c6-9kptf   1/1     Running   0          3m6s

The above output indicates that PSA allowed since Pod security configuration confirms to the Restricted PSS profile.

Note that the above security permissions are not the comprehensive list of controls allowed under Restricted PSS profile. For detailed security controls allowed/disallowed under each PSS profile, refer to the documentation.