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Kubernetes RBAC chi tiết, Pod Security Standards (PSS), ServiceAccount best practices, least-privilege access, audit logging, và security hardening cho cluster.

Deploy Microservices On-Premises với Kubernetes HA

Phần 9: Security Hardening

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🎯 MỤC TIÊU BÀI HỌC

✅ Kubernetes RBAC (Role, ClusterRole, Binding)
✅ Pod Security Standards (Privileged, Baseline, Restricted)
✅ ServiceAccount best practices
✅ Audit logging configuration
✅ Security hardening checklist

PHẦN 1: KUBERNETES RBAC


RBAC Model:

User/ServiceAccount
        │
        ▼
┌──────────────┐     ┌──────────────────┐
│ RoleBinding  │────►│      Role        │
│(namespace)   │     │  (namespace)     │
│              │     │  - get pods      │
│              │     │  - list services │
└──────────────┘     └──────────────────┘

┌──────────────────┐  ┌──────────────────┐
│ClusterRoleBinding│─►│   ClusterRole    │
│ (cluster-wide)   │  │  (cluster-wide)  │
│                  │  │  - get nodes     │
│                  │  │  - list PVs      │
└──────────────────┘  └──────────────────┘

# Role for app namespace (least privilege):
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: app-developer
  namespace: default
rules:
  - apiGroups: [""]
    resources: ["pods", "services", "configmaps"]
    verbs: ["get", "list", "watch"]
  - apiGroups: ["apps"]
    resources: ["deployments"]
    verbs: ["get", "list", "watch", "update", "patch"]
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get"]
  # Explicitly deny secrets access (not listed)

---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: developer-binding
  namespace: default
subjects:
  - kind: User
    name: [email protected]
    apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: Role
  name: app-developer
  apiGroup: rbac.authorization.k8s.io

# ClusterRole for read-only monitoring:
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: monitoring-reader
rules:
  - apiGroups: [""]
    resources: ["pods", "nodes", "services", "endpoints"]
    verbs: ["get", "list", "watch"]
  - apiGroups: ["metrics.k8s.io"]
    resources: ["pods", "nodes"]
    verbs: ["get", "list"]
  - nonResourceURLs: ["/metrics"]
    verbs: ["get"]

PHẦN 2: SERVICEACCOUNT BEST PRACTICES

# Dedicated ServiceAccount per workload:
apiVersion: v1
kind: ServiceAccount
metadata:
  name: order-service
  namespace: default
automountServiceAccountToken: false  # Disable auto-mount

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: order-service
spec:
  template:
    spec:
      serviceAccountName: order-service
      automountServiceAccountToken: false  # Double ensure
      containers:
        - name: app
          image: registry.local/order-service:v1.0
          securityContext:
            allowPrivilegeEscalation: false
            runAsNonRoot: true
            runAsUser: 1000
            readOnlyRootFilesystem: true
            capabilities:
              drop: ["ALL"]

PHẦN 3: POD SECURITY STANDARDS

Level	Description	Use Case
Privileged	No restrictions	System-level (CNI, storage drivers)
Baseline	Prevent known privilege escalation	Default for most workloads
Restricted	Hardened, all best practices	Sensitive workloads

# Apply PSS via namespace labels:
apiVersion: v1
kind: Namespace
metadata:
  name: production
  labels:
    # Enforce restricted:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/enforce-version: latest
    # Warn on baseline violations:
    pod-security.kubernetes.io/warn: restricted
    pod-security.kubernetes.io/audit: restricted

---
# Namespace for system workloads:
apiVersion: v1
kind: Namespace
metadata:
  name: kube-system
  labels:
    pod-security.kubernetes.io/enforce: privileged

# Pod that complies with Restricted:
apiVersion: v1
kind: Pod
metadata:
  name: secure-app
  namespace: production
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 1000
    seccompProfile:
      type: RuntimeDefault
  containers:
    - name: app
      image: registry.local/app:v1
      securityContext:
        allowPrivilegeEscalation: false
        readOnlyRootFilesystem: true
        capabilities:
          drop: ["ALL"]
      resources:
        requests:
          cpu: 100m
          memory: 128Mi
        limits:
          cpu: 500m
          memory: 256Mi

PHẦN 4: AUDIT LOGGING

# /etc/kubernetes/audit-policy.yaml:
apiVersion: audit.k8s.io/v1
kind: Policy
rules:
  # Log all auth failures:
  - level: Metadata
    omitStages: ["RequestReceived"]
    users: ["system:anonymous"]

  # Log secret access:
  - level: RequestResponse
    resources:
      - group: ""
        resources: ["secrets"]
    verbs: ["get", "list", "watch", "create", "update", "delete"]

  # Log RBAC changes:
  - level: RequestResponse
    resources:
      - group: "rbac.authorization.k8s.io"
        resources: ["roles", "rolebindings", "clusterroles", "clusterrolebindings"]

  # Log pod exec/attach:
  - level: RequestResponse
    resources:
      - group: ""
        resources: ["pods/exec", "pods/attach"]

  # Default: metadata only
  - level: Metadata
    omitStages: ["RequestReceived"]

# Enable in kube-apiserver:
# /etc/kubernetes/manifests/kube-apiserver.yaml
# Add flags:
#   --audit-policy-file=/etc/kubernetes/audit-policy.yaml
#   --audit-log-path=/var/log/kubernetes/audit.log
#   --audit-log-maxage=30
#   --audit-log-maxbackup=10
#   --audit-log-maxsize=100

# Forward audit logs to Loki:
# Configure Promtail to scrape /var/log/kubernetes/audit.log

PHẦN 5: SECURITY HARDENING CHECKLIST

#	Item	Status
1	RBAC enabled, no cluster-admin for apps	☐
2	Pod Security Standards enforced	☐
3	ServiceAccount token auto-mount disabled	☐
4	Network Policies deny-all default	☐
5	Audit logging enabled	☐
6	etcd encryption at rest	☐
7	API server on private network only	☐
8	Kubelet authn/authz enabled	☐
9	Container images signed/scanned	☐
10	Secrets in Vault (not plain K8s secrets)	☐

💡 KEY TAKEAWAYS

RBAC: Least privilege — only grant needed verbs/resources
ServiceAccount: Per-workload, disable token auto-mount
PSS: Enforce Restricted for production namespaces
Audit: Log secret access, RBAC changes, pod exec
SecurityContext: runAsNonRoot, drop ALL capabilities, readOnlyRootFilesystem

🎯 BÀI TẬP

Bài tập 1: RBAC Setup

Create developer/ops Roles with different permissions
Test access with kubectl --as=developer
Enable audit logging, verify secret access is logged

Bài tập 2: Pod Security

Label namespace with restricted PSS
Deploy a privileged pod → verify rejection
Fix pod to comply with restricted level

📚 BÀI TIẾP THEO

Trong Bài 37: Kyverno Policy Engine, chúng ta sẽ implement policy-as-code cho cluster.

BÀI 36: RBAC & POD SECURITY STANDARDS