Updated on 2024-01-24 GMT+08:00

Configuring a Pod Security Policy

A pod security policy (PSP) is a cluster-level resource that controls sensitive security aspects of the pod specification. The PodSecurityPolicy object in Kubernetes defines a group of conditions that a pod must comply with to be accepted by the system, as well as the default values of related fields.

By default, the PSP access control component is enabled for clusters of v1.17.17 and a global default PSP named psp-global is created. You can modify the default policy (but not delete it). You can also create a PSP and bind it to the RBAC configuration.

  • In addition to the global default PSP, the system configures independent PSPs for system components in namespace kube-system. Modifying the psp-global configuration does not affect pod creation in namespace kube-system.
  • PodSecurityPolicy was deprecated in Kubernetes v1.21, and removed from Kubernetes in v1.25. You can use pod security admission as a substitute for PodSecurityPolicy. For details, see Configuring Pod Security Admission.

Modifying the Global Default PSP

Before modifying the global default PSP, ensure that a CCE cluster has been created and connected by using kubectl.

  1. Run the following command:

    kubectl edit psp psp-global

  2. Modify the required parameters, as shown in Table 1.

    Table 1 PSP configuration

    Item

    Description

    privileged

    Starts the privileged container.

    hostPID

    hostIPC

    Uses the host namespace.

    hostNetwork

    hostPorts

    Uses the host network and port.

    volumes

    Specifies the type of the mounted volume that can be used.

    allowedHostPaths

    Specifies the host path to which a hostPath volume can be mounted. The pathPrefix field specifies the host path prefix group to which a hostPath volume can be mounted.

    allowedFlexVolumes

    Specifies the FlexVolume driver that can be used.

    fsGroup

    Configures the supplemental group ID used by the mounted volume in the pod.

    readOnlyRootFilesystem

    Pods can only be started using a read-only root file system.

    runAsUser

    runAsGroup

    supplementalGroups

    Specifies the user ID, primary group ID, and supplemental group ID for starting containers in a pod.

    allowPrivilegeEscalation

    defaultAllowPrivilegeEscalation

    Specifies whether allowPrivilegeEscalation can be set to true in a pod. This configuration controls the use of Setuid and whether programs can use additional privileged system calls.

    defaultAddCapabilities

    requiredDropCapabilities

    allowedCapabilities

    Controls the Linux capabilities used in pods.

    seLinux

    Controls the configuration of seLinux used in pods.

    allowedProcMountTypes

    Controls the ProcMountTypes that can be used by pods.

    annotations

    Configures AppArmor or Seccomp used by containers in a pod.

    forbiddenSysctls

    allowedUnsafeSysctls

    Controls the configuration of Sysctl used by containers in a pod.

Example of Enabling Unsafe Sysctls in Pod Security Policy

You can configure allowed-unsafe-sysctls for a node pool. For CCE clusters of v1.17.17 and later versions, add configurations in allowedUnsafeSysctls of the pod security policy to make the configuration take effect. For details, see Table 1.

In addition to modifying the global pod security policy, you can add new pod security policies. For example, enable the net.core.somaxconn unsafe sysctls. The following is an example of adding a pod security policy:

apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
  name: sysctl-psp
spec:
  allowedUnsafeSysctls:
  - net.core.somaxconn
  allowPrivilegeEscalation: true
  allowedCapabilities:
  - '*'
  fsGroup:
    rule: RunAsAny
  hostIPC: true
  hostNetwork: true
  hostPID: true
  hostPorts:
  - max: 65535
    min: 0
  privileged: true
  runAsGroup:
    rule: RunAsAny
  runAsUser:
    rule: RunAsAny
  seLinux:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  volumes:
  - '*'
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: sysctl-psp
rules:
  - apiGroups:
      - "*"
    resources:
      - podsecuritypolicies
    resourceNames:
      - sysctl-psp
    verbs:
      - use

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: sysctl-psp
roleRef:
  kind: ClusterRole
  name: sysctl-psp
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: Group
  name: system:authenticated
  apiGroup: rbac.authorization.k8s.io

Restoring the Original PSP

If you have modified the default pod security policy and want to restore the original pod security policy, perform the following operations.

  1. Create a policy description file named policy.yaml. policy.yaml is an example file name. You can rename it as required.

    vi policy.yaml

    The content of the description file is as follows:

    apiVersion: policy/v1beta1
    kind: PodSecurityPolicy
    metadata:
      name: psp-global
      annotations:
        seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
    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'
     
    ---
    kind: ClusterRole
    apiVersion: rbac.authorization.k8s.io/v1
    metadata:
      name: psp-global
    rules:
      - apiGroups:
          - "*"
        resources:
          - podsecuritypolicies
        resourceNames:
          - psp-global
        verbs:
          - use
     
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: psp-global
    roleRef:
      kind: ClusterRole
      name: psp-global
      apiGroup: rbac.authorization.k8s.io
    subjects:
    - kind: Group
      name: system:authenticated
      apiGroup: rbac.authorization.k8s.io

  2. Run the following command:

    kubectl apply -f policy.yaml