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) ```yaml 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) ```yaml 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) ```yaml 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 ```yaml apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: default-deny-all namespace: production spec: podSelector: {} policyTypes: - Ingress - Egress ``` ### Allow Frontend to Backend ```yaml 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 ```yaml 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 ``` **Reference:** See `assets/network-policy-template.yaml` ## RBAC Configuration ### Role (Namespace-scoped) ```yaml 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) ```yaml apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: secret-reader rules: - apiGroups: [""] resources: ["secrets"] verbs: ["get", "watch", "list"] ``` ### RoleBinding ```yaml 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 ``` **Reference:** See `references/rbac-patterns.md` ## Pod Security Context ### Restricted Pod ```yaml 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 ```yaml 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 ```yaml 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) ```yaml apiVersion: security.istio.io/v1beta1 kind: PeerAuthentication metadata: name: default namespace: production spec: mtls: mode: STRICT ``` ### AuthorizationPolicy ```yaml 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 **NetworkPolicy not working:** ```bash # Check if CNI supports NetworkPolicy kubectl get nodes -o wide kubectl describe networkpolicy <name> ``` **RBAC permission denied:** ```bash # 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 ``` ## Related Skills - `k8s-manifest-generator` - For creating secure manifests - `gitops-workflow` - For automated policy deployment