Apply Pod Security Standards at the Namespace Level

Pod Security admission (PSA) is enabled by default in v1.23 and later, as it graduated to beta. Pod Security Admission is an admission controller that applies Pod Security Standards when pods are created. In this tutorial, you will enforce the baseline Pod Security Standard, one namespace at a time.

You can also apply Pod Security Standards to multiple namespaces at once at the cluster level. For instructions, refer to Apply Pod Security Standards at the cluster level.

Before you begin

Install the following on your workstation:

• KinD
• kubectl

Create cluster

1. Create a KinD cluster as follows:

   kind create cluster --name psa-ns-level --image kindest/node:v1.23.0
   

   The output is similar to this:

   Creating cluster "psa-ns-level" ...
    ✓ Ensuring node image (kindest/node:v1.23.0) 🖼 
    ✓ Preparing nodes 📦  
    ✓ Writing configuration 📜 
    ✓ Starting control-plane 🕹️ 
    ✓ Installing CNI 🔌 
    ✓ Installing StorageClass 💾 
   Set kubectl context to "kind-psa-ns-level"
   You can now use your cluster with:
   
   kubectl cluster-info --context kind-psa-ns-level
   
   Not sure what to do next? 😅  Check out https://kind.sigs.k8s.io/docs/user/quick-start/
   

2. Set the kubectl context to the new cluster:

   kubectl cluster-info --context kind-psa-ns-level
   

   The output is similar to this:

   Kubernetes control plane is running at https://127.0.0.1:50996
   CoreDNS is running at https://127.0.0.1:50996/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
   
   To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
   

Create a namespace

Create a new namespace called example:

kubectl create ns example

The output is similar to this:

namespace/example created

Apply Pod Security Standards

1. Enable Pod Security Standards on this namespace using labels supported by built-in Pod Security Admission. In this step we will warn on baseline pod security standard as per the latest version (default value)

   kubectl label --overwrite ns example \
     pod-security.kubernetes.io/warn=baseline \
     pod-security.kubernetes.io/warn-version=latest
   

2. Multiple pod security standards can be enabled on any namespace, using labels. Following command will enforce the baseline Pod Security Standard, but warn and audit for restricted Pod Security Standards as per the latest version (default value)

   kubectl label --overwrite ns example \
     pod-security.kubernetes.io/enforce=baseline \
     pod-security.kubernetes.io/enforce-version=latest \
     pod-security.kubernetes.io/warn=restricted \
     pod-security.kubernetes.io/warn-version=latest \
     pod-security.kubernetes.io/audit=restricted \
     pod-security.kubernetes.io/audit-version=latest
   

Verify the Pod Security Standards

1. Create a minimal pod in example namespace:

   cat <<EOF > /tmp/pss/nginx-pod.yaml
   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx
   spec:
     containers:
       - image: nginx
         name: nginx
         ports:
           - containerPort: 80
   EOF
   

2. Apply the pod spec to the cluster in example namespace:

   kubectl apply -n example -f /tmp/pss/nginx-pod.yaml
   

   The output is similar to this:

   Warning: would violate PodSecurity "restricted:latest": allowPrivilegeEscalation != false (container "nginx" must set securityContext.allowPrivilegeEscalation=false), unrestricted capabilities (container "nginx" must set securityContext.capabilities.drop=["ALL"]), runAsNonRoot != true (pod or container "nginx" must set securityContext.runAsNonRoot=true), seccompProfile (pod or container "nginx" must set securityContext.seccompProfile.type to "RuntimeDefault" or "Localhost")
   pod/nginx created
   

3. Apply the pod spec to the cluster in default namespace:

    kubectl apply -n default -f /tmp/pss/nginx-pod.yaml
   

   Output is similar to this:

   pod/nginx created
   

The Pod Security Standards were applied only to the example namespace. You could create the same Pod in the default namespace with no warnings.

Clean up

Run kind delete cluster -name psa-ns-level to delete the cluster created.

What's next

• Run a shell script to perform all the preceding steps all at once.
  1. Create KinD cluster
  2. Create new namespace
  3. Apply baseline Pod Security Standard in enforce mode while applying restricted Pod Security Standard also in warn and audit mode.
  4. Create a new pod with the following pod security standards applied
• Pod Security Admission
• Pod Security Standards
• Apply Pod Security Standards at the cluster level