Kubernetes / OpenShift Security Guide

Comprehensive security assessment, hardening, and compliance for production clusters.

Current Security Tools (January 2026)

Tool	Version	Purpose	Documentation
Trivy	0.58.x	Vulnerability scanning	https://aquasecurity.github.io/trivy/
Kyverno	1.13.x	Policy engine	https://kyverno.io/
OPA Gatekeeper	3.18.x	Policy engine	https://open-policy-agent.github.io/gatekeeper/
Falco	0.39.x	Runtime security	https://falco.org/
kube-bench	0.8.x	CIS benchmarks	https://github.com/aquasecurity/kube-bench
kubescape	3.0.x	Security posture	https://kubescape.io/
External Secrets	0.12.x	Secret management	https://external-secrets.io/
Sealed Secrets	0.27.x	GitOps secrets	https://sealed-secrets.netlify.app/

Tool Installation

bash

# Trivy
brew install trivy

# Kyverno CLI
brew install kyverno

# kubescape
curl -s https://raw.githubusercontent.com/kubescape/kubescape/master/install.sh | /bin/bash

# kube-bench (as a Job)
kubectl apply -f https://raw.githubusercontent.com/aquasecurity/kube-bench/main/job.yaml

Command Usage Convention

IMPORTANT: This skill uses kubectl as the primary command. When working with:

•OpenShift/ARO clusters: Replace kubectl with oc
•Standard Kubernetes (AKS, EKS, GKE): Use kubectl as shown

Security Assessment Workflow

•Inventory: Identify workloads, namespaces, service accounts
•Audit: Run security scans, check configurations
•Classify: Risk level based on exposure and sensitivity
•Remediate: Apply hardening based on priority
•Monitor: Continuous compliance verification

Pod Security Standards (PSS) - Kubernetes 1.31

Security Levels

Level	Description	Use Case
`privileged`	Unrestricted policy	System workloads only
`baseline`	Minimally restrictive	Standard workloads
`restricted`	Heavily restricted	Security-sensitive workloads

Enforcement Modes

Mode	Behavior
`enforce`	Reject violating pods
`audit`	Log violations, allow pods
`warn`	Warn user, allow pods

Namespace Configuration

yaml

apiVersion: v1
kind: Namespace
metadata:
  name: ${NAMESPACE}
  labels:
    # Enforce restricted standard
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/enforce-version: latest
    # Audit for baseline
    pod-security.kubernetes.io/audit: baseline
    pod-security.kubernetes.io/audit-version: latest
    # Warn for restricted
    pod-security.kubernetes.io/warn: restricted
    pod-security.kubernetes.io/warn-version: latest

Restricted Profile Requirements

yaml

spec:
  securityContext:
    runAsNonRoot: true
    seccompProfile:
      type: RuntimeDefault
  containers:
    - securityContext:
        allowPrivilegeEscalation: false
        capabilities:
          drop:
            - ALL
        # Recommended:
        readOnlyRootFilesystem: true
        runAsNonRoot: true

RBAC Best Practices

Principle of Least Privilege

yaml

# BAD: Overly permissive
rules:
  - apiGroups: ["*"]
    resources: ["*"]
    verbs: ["*"]

# GOOD: Specific permissions
rules:
  - apiGroups: [""]
    resources: ["configmaps"]
    verbs: ["get", "list", "watch"]
    resourceNames: ["app-config"]  # Even more specific

Role vs ClusterRole

Type	Scope	Use When
`Role`	Namespace	App-specific permissions
`ClusterRole`	Cluster-wide	Cross-namespace or cluster resources

Common RBAC Patterns

Read-Only Application Access

yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: app-reader
  namespace: ${NAMESPACE}
rules:
  - apiGroups: [""]
    resources: ["pods", "services", "configmaps"]
    verbs: ["get", "list", "watch"]
  - apiGroups: ["apps"]
    resources: ["deployments", "replicasets"]
    verbs: ["get", "list", "watch"]

CI/CD Deployment Access

yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: deployer
  namespace: ${NAMESPACE}
rules:
  - apiGroups: ["apps"]
    resources: ["deployments"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]
  - apiGroups: [""]
    resources: ["configmaps", "secrets", "services"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]

Monitoring Access

yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: monitoring-reader
rules:
  - apiGroups: [""]
    resources: ["pods", "nodes", "services", "endpoints"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get"]
  - apiGroups: ["metrics.k8s.io"]
    resources: ["pods", "nodes"]
    verbs: ["get", "list"]

RBAC Audit Commands

bash

# Check what a service account can do
kubectl auth can-i --list --as=system:serviceaccount:${NS}:${SA}

# Check specific permission
kubectl auth can-i create deployments --as=system:serviceaccount:${NS}:${SA}

# Find overly permissive roles
kubectl get clusterroles -o json | jq -r \
  '.items[] | select(.rules[].verbs | contains(["*"])) | .metadata.name'

NetworkPolicy Zero-Trust

Default Deny All

yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: ${NAMESPACE}
spec:
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress

Allow DNS Egress (Required)

yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-dns
  namespace: ${NAMESPACE}
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: kube-system
        - podSelector:
            matchLabels:
              k8s-app: kube-dns
      ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53

Allow Ingress from Controller

yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-ingress-controller
  namespace: ${NAMESPACE}
spec:
  podSelector:
    matchLabels:
      app.kubernetes.io/name: ${APP_NAME}
  policyTypes:
    - Ingress
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: ingress-nginx
      ports:
        - protocol: TCP
          port: 8080

Allow Inter-Service Communication

yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-frontend-to-backend
  namespace: ${NAMESPACE}
spec:
  podSelector:
    matchLabels:
      app.kubernetes.io/name: backend
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app.kubernetes.io/name: frontend
      ports:
        - protocol: TCP
          port: 8080

Secrets Management

External Secrets Operator (v0.12.x)

bash

# Install
helm repo add external-secrets https://charts.external-secrets.io
helm install external-secrets external-secrets/external-secrets \
  --namespace external-secrets \
  --create-namespace \
  --set installCRDs=true

yaml

# ClusterSecretStore for Vault
apiVersion: external-secrets.io/v1beta1
kind: ClusterSecretStore
metadata:
  name: vault-backend
spec:
  provider:
    vault:
      server: "https://vault.example.com"
      path: "secret"
      version: "v2"
      auth:
        kubernetes:
          mountPath: "kubernetes"
          role: "external-secrets"
---
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: app-secrets
  namespace: ${NAMESPACE}
spec:
  refreshInterval: 1h
  secretStoreRef:
    name: vault-backend
    kind: ClusterSecretStore
  target:
    name: app-secrets
    creationPolicy: Owner
  data:
    - secretKey: DATABASE_URL
      remoteRef:
        key: apps/${APP_NAME}
        property: database_url

Sealed Secrets (GitOps-friendly, v0.27.x)

bash

# Install
helm repo add sealed-secrets https://bitnami-labs.github.io/sealed-secrets
helm install sealed-secrets sealed-secrets/sealed-secrets \
  --namespace kube-system

# Install CLI
brew install kubeseal

# Create sealed secret
kubeseal --format=yaml < secret.yaml > sealed-secret.yaml

# Apply (controller decrypts it)
kubectl apply -f sealed-secret.yaml

OpenShift Security Context Constraints

SCC Hierarchy (Most to Least Restrictive)

•restricted-v2 - Default, most restrictive
•nonroot-v2 - Must run as non-root
•hostnetwork-v2 - Allow host network
•anyuid - Run as any UID
•privileged - Full privileges (avoid!)

Check SCC Assignment

bash

# See which SCC a pod is using
oc get pod ${POD} -n ${NS} -o yaml | grep scc

# List available SCCs
oc get scc

# Check SA SCC permissions
oc adm policy who-can use scc restricted-v2

Grant SCC to Service Account

bash

oc adm policy add-scc-to-user ${SCC} -z ${SERVICE_ACCOUNT} -n ${NAMESPACE}

yaml

# Via RoleBinding (GitOps-friendly)
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: ${SA}-scc-${SCC}
  namespace: ${NAMESPACE}
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:openshift:scc:${SCC}
subjects:
  - kind: ServiceAccount
    name: ${SERVICE_ACCOUNT}
    namespace: ${NAMESPACE}

Image Security

Trivy Scanning

bash

# Scan image for vulnerabilities
trivy image ${IMAGE}:${TAG}

# Scan with severity filter
trivy image --severity HIGH,CRITICAL ${IMAGE}:${TAG}

# Scan and output JSON
trivy image -f json -o results.json ${IMAGE}:${TAG}

# Scan Kubernetes cluster
trivy k8s --report summary cluster

Kyverno Policy Examples

yaml

# Require non-root containers
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-run-as-nonroot
spec:
  validationFailureAction: enforce
  rules:
    - name: run-as-non-root
      match:
        resources:
          kinds:
            - Pod
      validate:
        message: "Containers must run as non-root"
        pattern:
          spec:
            containers:
              - securityContext:
                  runAsNonRoot: true
---
# Block privileged containers
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: disallow-privileged
spec:
  validationFailureAction: enforce
  rules:
    - name: deny-privileged
      match:
        resources:
          kinds:
            - Pod
      validate:
        message: "Privileged containers are not allowed"
        pattern:
          spec:
            containers:
              - securityContext:
                  privileged: "!true"

Security Audit Script

bash

#!/bin/bash
echo "=== KUBERNETES SECURITY AUDIT ==="

# Check for privileged containers
echo "### Privileged Containers ###"
kubectl get pods -A -o json | jq -r \
  '.items[] | select(.spec.containers[].securityContext.privileged == true) |
   "\(.metadata.namespace)/\(.metadata.name)"'

# Check for root containers
echo -e "\n### Containers Running as Root ###"
kubectl get pods -A -o json | jq -r \
  '.items[] | select(.spec.containers[].securityContext.runAsUser == 0) |
   "\(.metadata.namespace)/\(.metadata.name)"'

# Check for host namespace access
echo -e "\n### Host Namespace Access ###"
kubectl get pods -A -o json | jq -r \
  '.items[] | select(.spec.hostNetwork == true or .spec.hostPID == true) |
   "\(.metadata.namespace)/\(.metadata.name)"'

# Check for default service accounts
echo -e "\n### Pods Using Default SA ###"
kubectl get pods -A -o json | jq -r \
  '.items[] | select(.spec.serviceAccountName == "default") |
   "\(.metadata.namespace)/\(.metadata.name)"'

# Check for overly permissive RBAC
echo -e "\n### Wildcard RBAC Roles ###"
kubectl get clusterroles -o json | jq -r \
  '.items[] | select(.rules[].verbs | contains(["*"])) | .metadata.name'

# Check namespaces without NetworkPolicy
echo -e "\n### Namespaces Without NetworkPolicy ###"
for ns in $(kubectl get ns -o jsonpath='{.items[*].metadata.name}'); do
  count=$(kubectl get networkpolicy -n $ns --no-headers 2>/dev/null | wc -l)
  [ "$count" -eq 0 ] && echo "$ns"
done

CIS Benchmark Compliance

bash

# Run kube-bench
kubectl apply -f https://raw.githubusercontent.com/aquasecurity/kube-bench/main/job.yaml
kubectl logs -f job/kube-bench

# Run kubescape
kubescape scan framework nsa --exclude-namespaces kube-system
kubescape scan framework cis-v1.23-t1.0.1