K8S Security Policies

Kubernetes Security Policies

Comprehensive guide for implementing NetworkPolicy, PodSecurityPolicy, RBAC, and Pod Security Standards in Kubernetes.

Purpose

Implement defense-in-depth security for Kubernetes clusters using network policies, pod security standards, and RBAC.

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)

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

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:
    -

Allow DNS

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-dns
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - namespaceSelector:
            matchLabels

Reference: See assets/network-policy-template.yaml

RBAC Configuration

Role (Namespace-scoped)

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

Reference: See references/rbac-patterns.md

Pod Security Context

Restricted Pod

apiVersion: v1
kind: Pod
metadata:
  name: secure-pod
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 1000
    seccompProfile:
      type: RuntimeDefault
  containers

Policy Enforcement with OPA Gatekeeper

ConstraintTemplate

apiVersion: templates.gatekeeper.sh/v1
kind: ConstraintTemplate
metadata:
  name: k8srequiredlabels
spec:
  crd:
    spec:
      names:
        kind: K8sRequiredLabels
      validation:
        openAPIV3Schema

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)

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:

Best Practices

Implement Pod Security Standards at namespace level
Use Network Policies for network segmentation
Apply least-privilege RBAC for all service accounts
Enable admission control (OPA Gatekeeper/Kyverno)
Run containers as non-root
Use read-only root filesystem
Drop all capabilities unless needed
Implement resource quotas and limit ranges
Enable audit logging for security events
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

NetworkPolicy not working:

# 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

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