Kubernetes的Pod安全策略（Pod Security Policy）准入控制组件会基于您定义的规则验证在集群上创建和更新Pod的请求。如果创建或更新Pod的请求不符合定义的规则，系统将拒绝该请求并返回错误。本文将介绍如何在容器服务Kubernetes版ACK（Container Service for Kubernetes）中使用Pod安全策略。

前提条件

您已完成以下操作：

ACK默认的Pod安全策略

在ACK中，Kubernetes 1.16.6版本的标准专有集群和标准托管集群将默认启用Pod安全策略准入控制组件，并配置一个名为ack.privileged的Pod安全策略。这个安全策略将放行任意类型的Pod，效果等同于集群未开启Pod安全策略准入控制组件。 

$ kubectl get psp ack.privileged
NAME             PRIV   CAPS   SELINUX    RUNASUSER   FSGROUP    SUPGROUP   READONLYROOTFS   VOLUMES
ack.privileged   true   *      RunAsAny   RunAsAny    RunAsAny   RunAsAny   false            *
$ kubectl describe psp ack.privileged
Name:  ack.privileged

Settings:
  Allow Privileged:                       true
  Allow Privilege Escalation:             true
  Default Add Capabilities:               <none>
  Required Drop Capabilities:             <none>
  Allowed Capabilities:                   *
  Allowed Volume Types:                   *
  Allow Host Network:                     true
  Allow Host Ports:                       0-65535
  Allow Host PID:                         true
  Allow Host IPC:                         true
  Read Only Root Filesystem:              false
  SELinux Context Strategy: RunAsAny
    User:                                 <none>
    Role:                                 <none>
    Type:                                 <none>
    Level:                                <none>
  Run As User Strategy: RunAsAny
    Ranges:                               <none>
  FSGroup Strategy: RunAsAny
    Ranges:                               <none>
  Supplemental Groups Strategy: RunAsAny
    Ranges:                               <none>

---
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: ack.privileged
  annotations:
    kubernetes.io/description: 'privileged allows full unrestricted access to
      pod features, as if the PodSecurityPolicy controller was not enabled.'
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
spec:
  privileged: true
  allowPrivilegeEscalation: true
  allowedCapabilities:
  - '*'
  volumes:
  - '*'
  hostNetwork: true
  hostPorts:
  - min: 0
    max: 65535
  hostIPC: true
  hostPID: true
  runAsUser:
    rule: 'RunAsAny'
  seLinux:
    rule: 'RunAsAny'
  supplementalGroups:
    rule: 'RunAsAny'
  fsGroup:
    rule: 'RunAsAny'
  readOnlyRootFilesystem: false

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: ack:podsecuritypolicy:privileged
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
rules:
- apiGroups:
  - policy
  resourceNames:
  - ack.privileged
  resources:
  - podsecuritypolicies
  verbs:
  - use

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: ack:podsecuritypolicy:authenticated
  annotations:
    kubernetes.io/description: 'Allow all authenticated users to create privileged pods.'
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ack:podsecuritypolicy:privileged
subjects:
  - kind: Group
    apiGroup: rbac.authorization.k8s.io
    name: system:authenticated

删除ACK默认Pod安全策略对应的集群角色绑定

警告 在删除ACK默认的Pod安全策略对应的集群角色绑定前必须先配置好自定义的Pod安全策略及其相应的RBAC绑定，否则所有用户、控制器、服务账号都将无法创建或更新Pod。
在配置好自定义的Pod安全策略及其相应的RBAC绑定后，您可以通过删除ACK默认Pod安全策略ack.privileged的集群角色绑定的方式来启用您自定义的Pod安全策略。
注意 请不要删除或修改名为ack.privileged的Pod安全策略以及名为ack:podsecuritypolicy:privileged的集群角色，ACK集群的正常运行需要依赖这两个资源。 
$ cat <<EOF | kubectl delete -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: ack:podsecuritypolicy:authenticated
  annotations:
    kubernetes.io/description: 'Allow all authenticated users to create privileged pods.'
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ack:podsecuritypolicy:privileged
subjects:
  - kind: Group
    apiGroup: rbac.authorization.k8s.io
    name: system:authenticated
EOF

配置或恢复ACK默认的Pod安全策略

$ cat <<EOF | kubectl apply -f -
---
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: ack.privileged
  annotations:
    kubernetes.io/description: 'privileged allows full unrestricted access to
      pod features, as if the PodSecurityPolicy controller was not enabled.'
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
spec:
  privileged: true
  allowPrivilegeEscalation: true
  allowedCapabilities:
  - '*'
  volumes:
  - '*'
  hostNetwork: true
  hostPorts:
  - min: 0
    max: 65535
  hostIPC: true
  hostPID: true
  runAsUser:
    rule: 'RunAsAny'
  seLinux:
    rule: 'RunAsAny'
  supplementalGroups:
    rule: 'RunAsAny'
  fsGroup:
    rule: 'RunAsAny'
  readOnlyRootFilesystem: false

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: ack:podsecuritypolicy:privileged
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
rules:
- apiGroups:
  - policy
  resourceNames:
  - ack.privileged
  resources:
  - podsecuritypolicies
  verbs:
  - use

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: ack:podsecuritypolicy:authenticated
  annotations:
    kubernetes.io/description: 'Allow all authenticated users to create privileged pods.'
  labels:
    kubernetes.io/cluster-service: "true"
    ack.alicloud.com/component: pod-security-policy
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ack:podsecuritypolicy:privileged
subjects:
  - kind: Group
    apiGroup: rbac.authorization.k8s.io
    name: system:authenticated
EOF