Securing Kubernetes On Cloud

# Production namespace with restricted Pod Security Standard
apiVersion: v1
kind: Namespace
metadata:
  name: production
  labels:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/enforce-version: latest
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/warn: restricted
---
# Staging namespace with baseline enforcement
apiVersion: v1
kind: Namespace
metadata:
  name: staging
  labels:
    pod-security.kubernetes.io/enforce: baseline
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/warn: restricted

# Pod spec compliant with restricted profile
apiVersion: v1
kind: Pod
metadata:
  name: secure-app
  namespace: production
spec:
  automountServiceAccountToken: false
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 1000
    seccompProfile:
      type: RuntimeDefault
  containers:
    - name: app
      image: company/app:v2.1@sha256:abc123...
      securityContext:
        allowPrivilegeEscalation: false
        readOnlyRootFilesystem: true
        capabilities:
          drop: ["ALL"]
      resources:
        limits:
          cpu: "500m"
          memory: "256Mi"
        requests:
          cpu: "100m"
          memory: "128Mi"

# EKS: IAM Roles for Service Accounts (IRSA)
eksctl create iamserviceaccount \
  --cluster production-cluster \
  --namespace production \
  --name web-app-sa \
  --attach-policy-arn arn:aws:iam::123456789012:policy/WebAppS3ReadOnly \
  --approve

# GKE: Workload Identity
gcloud iam service-accounts create web-app-sa \
  --project=my-gcp-project

gcloud iam service-accounts add-iam-policy-binding \
  web-app-sa@my-gcp-project.iam.gserviceaccount.com \
  --role roles/storage.objectViewer \
  --member "serviceAccount:my-gcp-project.svc.id.goog[production/web-app-sa]"

kubectl annotate serviceaccount web-app-sa \
  --namespace production \
  iam.gke.io/gcp-service-account=web-app-sa@my-gcp-project.iam.gserviceaccount.com

# AKS: Azure AD Workload Identity
az identity create --name web-app-identity --resource-group production-rg
az identity federated-credential create \
  --name web-app-federation \
  --identity-name web-app-identity \
  --resource-group production-rg \
  --issuer "$(az aks show -n production-cluster -g production-rg --query oidcIssuerProfile.issuerUrl -o tsv)" \
  --subject system:serviceaccount:production:web-app-sa

# Default deny all ingress and egress in production namespace
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress
---
# Allow web-app to receive traffic from ingress controller only
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-ingress-to-web
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: web-app
  policyTypes:
    - Ingress
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              name: ingress-nginx
      ports:
        - protocol: TCP
          port: 8080
---
# Allow web-app to connect to database only
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-web-to-db
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: web-app
  policyTypes:
    - Egress
  egress:
    - to:
        - podSelector:
            matchLabels:
              app: postgres
      ports:
        - protocol: TCP
          port: 5432
    - to:
        - namespaceSelector: {}
          podSelector:
            matchLabels:
              k8s-app: kube-dns
      ports:
        - protocol: UDP
          port: 53

# Developer role scoped to specific namespace
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: developer-role
  namespace: staging
rules:
  - apiGroups: [""]
    resources: ["pods", "pods/log", "services", "configmaps"]
    verbs: ["get", "list", "watch"]
  - apiGroups: ["apps"]
    resources: ["deployments"]
    verbs: ["get", "list", "watch", "update", "patch"]
  # Explicitly deny secrets access
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: developer-binding
  namespace: staging
subjects:
  - kind: Group
    name: developers
    apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: Role
  name: developer-role
  apiGroup: rbac.authorization.k8s.io

# Kyverno policy: require images from approved registries
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: restrict-image-registries
spec:
  validationFailureAction: Enforce
  rules:
    - name: validate-registries
      match:
        any:
          - resources:
              kinds: ["Pod"]
      validate:
        message: "Images must come from approved registries"
        pattern:
          spec:
            containers:
              - image: "123456789012.dkr.ecr.us-east-1.amazonaws.com/* | gcr.io/my-gcp-project/*"
---
# Kyverno policy: require image digest (no mutable tags)
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-image-digest
spec:
  validationFailureAction: Enforce
  rules:
    - name: require-digest
      match:
        any:
          - resources:
              kinds: ["Pod"]
      validate:
        message: "Images must use digest references, not tags"
        pattern:
          spec:
            containers:
              - image: "*@sha256:*"

# Deploy Falco for runtime threat detection
helm repo add falcosecurity https://falcosecurity.github.io/charts
helm install falco falcosecurity/falco \
  --namespace falco-system --create-namespace \
  --set falcosidekick.enabled=true \
  --set falcosidekick.config.slack.webhookurl="https://hooks.slack.com/services/xxx"

# Run kube-bench for CIS Kubernetes Benchmark assessment
kubectl apply -f https://raw.githubusercontent.com/aquasecurity/kube-bench/main/job-eks.yaml
kubectl logs -l app=kube-bench