kubernetes pod podsecurityPolicies

tags: 资源对象，pod

美剧《开发者》（Devs）颠覆感藏在最后。

1. 简介

Pod Security Policies（PSP）是集群级的 Pod 安全策略，自动为集群内的 Pod 和 Volume 设置 Security Context。

使用 PSP 需要 API Server 开启 extensions/v1beta1/podsecuritypolicy，并且配置 PodSecurityPolicy admission 控制器。

注意： PodSecurityPolicy 自 Kubernetes v1.21 起已弃用，并将在 v1.25 中删除。我们建议迁移到Pod Security Admission或 3rd party admission 插件。有关迁移指南，请参阅从 PodSecurityPolicy 迁移到内置 PodSecurity 准入控制器。有关弃用的更多信息，请参阅PodSecurityPolicy 弃用：过去、现在和未来。

2. API 版本对照表

3. 支持的控制项

4. 实例

4.1 控制是否允许超出父进程特权

allowPrivilegeEscalation：控制进程是否可以获得超出其父进程的特权。 此布尔值直接控制是否为容器进程设置 no_new_privs标志。 当容器满足一下条件之一时，allowPrivilegeEscalation 总是为 true： 以特权模式运行，或者 具有 CAP_SYS_ADMIN 权能 readOnlyRootFilesystem：以只读方式加载容器的根文件系统。

root@master:~/cks/securitytext# vim /etc/kubernetes/manifests/kube-apiserver.yaml
---
    - --enable-admission-plugins=NodeRestriction,PodSecurityPolicy
---


root@master:~/cks/securitytext# cat psp.yaml 
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: default
spec:
  allowPrivilegeEscalation: false
  privileged: false  # Don't allow privileged pods!
  # The rest fills in some required fields.
  seLinux:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  runAsUser:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  volumes:
  - '*'


root@master:~/cks/securitytext# k create -f psp.yaml 
podsecuritypolicy.policy/default created


root@master:~/cks/securitytext# k create deploy nginx --image=nginx
deployment.apps/nginx created
root@master:~/cks/securitytext# k get deploy nginx -w
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   0/1     0            0           22s
^Croot@master:~/cks/securitytext#  k run nginx --image=nginx
pod/nginx created
root@master:~/cks/securitytext# k get pod nginx
NAME    READY   STATUS              RESTARTS   AGE
nginx   1/1     Running             0          44s

root@master:~/cks/securitytext#  k create role psp-access --verb=use --resource=podsecuritypolicies
role.rbac.authorization.k8s.io/psp-access created
root@master:~/cks/securitytext# k create rolebinding psp-access --role=psp-access --serviceaccount=default:default
rolebinding.rbac.authorization.k8s.io/psp-access created
root@master:~/cks/securitytext# k get deploy nginx
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   0/1     0            0           3m26s
root@master:~/cks/securitytext# k delete deploy nginx
deployment.apps "nginx" deleted
root@master:~/cks/securitytext# k create deploy nginx --image=nginx
deployment.apps/nginx created
^Croot@master:~/cks/securitytext# k get deploy nginx
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           20s

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allowPrivilegeEscalation设置为rue

root@master:~/cks/securitytext# vim pod.yaml 
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: pod
  name: pod
spec:
#  securityContext:
#    runAsUser: 1000
#    runAsGroup: 3000
  containers:
  - command:
    - sh
    - -c
    - sleep 1d
    image: busybox
    name: pod
    resources: {}
    securityContext:
      allowPrivilegeEscalation: true
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

root@master:~/cks/securitytext# k -f pod.yaml create
Error from server (Forbidden): error when creating "pod.yaml": pods "pod" is forbidden: PodSecurityPolicy: unable to admit pod: [spec.containers[0].securityContext.allowPrivilegeEscalation: Invalid value: true: Allowing privilege escalation for containers is not allowed]
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4.2 限制端口

限制容器的 host 端口范围为 8000-8080

apiVersion: extensions/v1beta1
kind: PodSecurityPolicy
metadata:
  name: permissive
spec:
  seLinux:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  runAsUser:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  hostPorts:
  - min: 8000
    max: 8080
  volumes:
  - '*'
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4.3 限制只允许使用 lvm 和 cifs 等 flexVolume 插件

apiVersion: extensions/v1beta1
kind: PodSecurityPolicy
metadata:
  name: allow-flex-volumes
spec:
  fsGroup:
    rule: RunAsAny
  runAsUser:
    rule: RunAsAny
  seLinux:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  volumes:
    - flexVolume
  allowedFlexVolumes:
    - driver: example/lvm
    - driver: example/cifs
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参考：

• Pod Security Policies