k8s-security-policies

Kubernetes 安全策略

在 Kubernetes 中实施 NetworkPolicy、PodSecurityPolicy、RBAC 和 Pod 安全标准的综合指南。

目的

使用网络策略、Pod 安全标准和 RBAC 为 Kubernetes 集群实施纵深防御安全。

何时使用此技能

• 实施网络分段
• 配置 Pod 安全标准
• 为最小权限访问设置 RBAC
• 为合规性创建安全策略
• 实施准入控制
• 保护多租户集群

Pod 安全标准

1. Privileged（无限制）

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（最低限制）

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（最严格限制）

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

网络策略

默认拒绝所有

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress

允许前端访问后端

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

允许 DNS

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

参考： 见 assets/network-policy-template.yaml

RBAC 配置

Role（命名空间范围）

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-reader
  namespace: production
rules:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["get", "watch", "list"]

ClusterRole（集群范围）

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: default
    namespace: production
roleRef:
  kind: Role
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io

参考： 见 references/rbac-patterns.md

Pod 安全上下文

受限 Pod

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

使用 OPA Gatekeeper 实施策略

ConstraintTemplate

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

apiVersion: constraints.gatekeeper.sh/v1beta1
kind: K8sRequiredLabels
metadata:
  name: require-app-label
spec:
  match:
    kinds:
      - apiGroups: ["apps"]
        kinds: ["Deployment"]
  parameters:
    labels: ["app", "environment"]

服务网格安全（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:
        - source:
            principals: ["cluster.local/ns/production/sa/frontend"]

最佳实践

1. 在命名空间级别实施 Pod 安全标准
2. 使用网络策略进行网络分段
3. 为所有服务账户应用最小权限 RBAC
4. 启用准入控制（OPA Gatekeeper/Kyverno）
5. 以非 root 用户运行容器
6. 使用只读根文件系统
7. 丢弃所有能力，除非确有必要
8. 实施资源配额和限制范围
9. 为安全事件启用审计日志
10. 定期对镜像进行安全扫描

合规框架

CIS Kubernetes Benchmark

• 使用 RBAC 授权
• 启用审计日志
• 使用 Pod 安全标准
• 配置网络策略
• 实施静态加密的密钥
• 启用节点身份验证

NIST 网络安全框架

• 实施纵深防御
• 使用网络分段
• 配置安全监控
• 实施访问控制
• 启用日志记录和监控

故障排查

NetworkPolicy 不生效：

# Check if CNI supports NetworkPolicy
kubectl get nodes -o wide
kubectl describe networkpolicy <name>

RBAC 权限被拒绝：

# 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

相关技能

• k8s-manifest-generator - 用于创建安全清单
• gitops-workflow - 用于自动化策略部署