K8s Security Policies

# Network Policy Templates

---
# Template 1: Default Deny All (Start Here)
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: <namespace>
spec:
  podSelector: {}
  policyTypes:
  - Ingress
  - Egress

---
# Template 2: Allow DNS (Essential)
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-dns
  namespace: <namespace>
spec:
  podSelector: {}
  policyTypes:
  - Egress
  egress:
  - to:
    - namespaceSelector:
        matchLabels:
          name: kube-system
    ports:
    - protocol: UDP
      port: 53

---
# Template 3: Frontend to Backend
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-frontend-to-backend
  namespace: <namespace>
spec:
  podSelector:
    matchLabels:
      app: backend
      tier: backend
  policyTypes:
  - Ingress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          app: frontend
          tier: frontend
    ports:
    - protocol: TCP
      port: 8080
    - protocol: TCP
      port: 9090

---
# Template 4: Allow Ingress Controller
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-ingress-controller
  namespace: <namespace>
spec:
  podSelector:
    matchLabels:
      app: web
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          name: ingress-nginx
    ports:
    - protocol: TCP
      port: 80
    - protocol: TCP
      port: 443

---
# Template 5: Allow Monitoring (Prometheus)
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-prometheus-scraping
  namespace: <namespace>
spec:
  podSelector:
    matchLabels:
      prometheus.io/scrape: "true"
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          name: monitoring
    ports:
    - protocol: TCP
      port: 9090

---
# Template 6: Allow External HTTPS
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-external-https
  namespace: <namespace>
spec:
  podSelector:
    matchLabels:
      app: api-client
  policyTypes:
  - Egress
  egress:
  - to:
    - ipBlock:
        cidr: 0.0.0.0/0
        except:
        - 169.254.169.254/32  # Block metadata service
    ports:
    - protocol: TCP
      port: 443

---
# Template 7: Database Access
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-app-to-database
  namespace: <namespace>
spec:
  podSelector:
    matchLabels:
      app: postgres
      tier: database
  policyTypes:
  - Ingress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          tier: backend
    ports:
    - protocol: TCP
      port: 5432

---
# Template 8: Cross-Namespace Communication
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-from-prod-namespace
  namespace: <namespace>
spec:
  podSelector:
    matchLabels:
      app: api
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          environment: production
      podSelector:
        matchLabels:
          app: frontend
    ports:
    - protocol: TCP
      port: 8080


# RBAC Patterns and Best Practices

## Common RBAC Patterns

### Pattern 1: Read-Only Access

```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: read-only
rules:
  - apiGroups: ["", "apps", "batch"]
    resources: ["*"]
    verbs: ["get", "list", "watch"]
```

### Pattern 2: Namespace Admin

```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: namespace-admin
  namespace: production
rules:
  - apiGroups: ["", "apps", "batch", "extensions"]
    resources: ["*"]
    verbs: ["*"]
```

### Pattern 3: Deployment Manager

```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: deployment-manager
  namespace: production
rules:
  - apiGroups: ["apps"]
    resources: ["deployments"]
    verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]