Kubernetes Security Policies

Purpose

When to Use This Skill

• Implement network segmentation
• Configure pod security standards
• Set up RBAC for least-privilege access
• Create security policies for compliance
• Implement admission control
• Secure multi-tenant clusters

Pod Security Standards

1. Privileged (Unrestricted)

Copy
apiVersion: v1
kind: Namespace
metadata:
  name: privileged-ns
  labels:
    pod-security.kubernetes.io/enforce: privileged
    pod-security.kubernetes.io/audit: privileged
    pod-security.kubernetes.io/warn: privileged
`### 2\. Baseline (Minimally restrictive)`
apiVersion: v1
kind: Namespace
metadata:
  name: baseline-ns
  labels:
    pod-security.kubernetes.io/enforce: baseline
    pod-security.kubernetes.io/audit: baseline
    pod-security.kubernetes.io/warn: baseline
`### 3\. Restricted (Most restrictive)`
apiVersion: v1
kind: Namespace
metadata:
  name: restricted-ns
  labels:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/warn: restricted

Network Policies

Default Deny All

Copy
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress
`### Allow Frontend to Backend`
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-frontend-to-backend
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: backend
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: frontend
      ports:
        - protocol: TCP
          port: 8080
`### Allow DNS`
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-dns
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - namespaceSelector:
            matchLabels:
              name: kube-system
      ports:
        - protocol: UDP
          port: 53

RBAC Configuration

Role (Namespace-scoped)

Copy
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-reader
  namespace: production
rules:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["get", "watch", "list"]
`### ClusterRole (Cluster-wide)`
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: secret-reader
rules:
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get", "watch", "list"]
`### RoleBinding`
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: read-pods
  namespace: production
subjects:
  - kind: User
    name: jane
    apiGroup: rbac.authorization.k8s.io
  - kind: ServiceAccount
    name: default
    namespace: production
roleRef:
  kind: Role
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io

Pod Security Context

Restricted Pod

Copy
apiVersion: v1
kind: Pod
metadata:
  name: secure-pod
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 1000
    seccompProfile:
      type: RuntimeDefault
  containers:
    - name: app
      image: myapp:1.0
      securityContext:
        allowPrivilegeEscalation: false
        readOnlyRootFilesystem: true
        capabilities:
          drop:
            - ALL

Policy Enforcement with OPA Gatekeeper

ConstraintTemplate

Copy
apiVersion: templates.gatekeeper.sh/v1
kind: ConstraintTemplate
metadata:
  name: k8srequiredlabels
spec:
  crd:
    spec:
      names:
        kind: K8sRequiredLabels
      validation:
        openAPIV3Schema:
          type: object
          properties:
            labels:
              type: array
              items:
                type: string
  targets:
    - target: admission.k8s.gatekeeper.sh
      rego: |
        package k8srequiredlabels
        violation[{"msg": msg, "details": {"missing_labels": missing}}] {
          provided := {label | input.review.object.metadata.labels[label]}
          required := {label | label := input.parameters.labels[_]}
          missing := required - provided
          count(missing) > 0
          msg := sprintf("missing required labels: %v", [missing])
        }
`### Constraint`
apiVersion: constraints.gatekeeper.sh/v1beta1
kind: K8sRequiredLabels
metadata:
  name: require-app-label
spec:
  match:
    kinds:
      - apiGroups: ["apps"]
        kinds: ["Deployment"]
  parameters:
    labels: ["app", "environment"]

Service Mesh Security (Istio)

PeerAuthentication (mTLS)

Copy
apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: default
  namespace: production
spec:
  mtls:
    mode: STRICT
`### AuthorizationPolicy`
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
  name: allow-frontend
  namespace: production
spec:
  selector:
    matchLabels:
      app: backend
  action: ALLOW
  rules:
    - from:
        - source:
            principals: ["cluster.local/ns/production/sa/frontend"]

Best Practices

1. Implement Pod Security Standards at namespace level
2. Use Network Policies for network segmentation
3. Apply least-privilege RBAC for all service accounts
4. Enable admission control (OPA Gatekeeper/Kyverno)
5. Run containers as non-root
6. Use read-only root filesystem
7. Drop all capabilities unless needed
8. Implement resource quotas and limit ranges
9. Enable audit logging for security events
10. Regular security scanning of images

Compliance Frameworks

CIS Kubernetes Benchmark

• Use RBAC authorization
• Enable audit logging
• Use Pod Security Standards
• Configure network policies
• Implement secrets encryption at rest
• Enable node authentication

NIST Cybersecurity Framework

• Implement defense in depth
• Use network segmentation
• Configure security monitoring
• Implement access controls
• Enable logging and monitoring

Troubleshooting

Copy
# Check if CNI supports NetworkPolicy
kubectl get nodes -o wide
kubectl describe networkpolicy <name>
`**RBAC permission denied:**`
# Check effective permissions
kubectl auth can-i list pods --as system:serviceaccount:default:my-sa
kubectl auth can-i '*' '*' --as system:serviceaccount:default:my-sa

Reference Files

• assets/network-policy-template.yaml - Network policy examples
• assets/pod-security-template.yaml - Pod security policies
• references/rbac-patterns.md - RBAC configuration patterns

Related Skills

• k8s-manifest-generator - For creating secure manifests
• gitops-workflow - For automated policy deployment