Cluster Policy Examples for Containers

Here, we demonstrate how to define a cluster security policies.

• Process Execution Restriction

  • Block a specific executable - In operator (csp-in-operator-block-process.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorClusterPolicy
    metadata:
      name: csp-in-operator-block-process
    spec:
      severity: 8
      selector:
        matchExpressions:
          - key: namespace
            operator: In
            values:
              - nginx1
      process:
        matchPaths:
          - path: /usr/bin/apt
      action:
        Block

    • Explanation: The purpose of this policy is to block the execution of '/usr/bin/apt' in the containers present in the namespace nginx1. For this, we define the 'nginx1' value and operator as 'In' in selector -> matchExpressions and the specific path ('/usr/bin/apt') in process -> matchPaths. Also, we put 'Block' as the action of this policy.

    • Verification: After applying this policy, please get into one of the containers in the namespace 'nginx1' (using "kubectl -n nginx1 exec -it nginx-X-... -- bash") and run '/usr/bin/apt'. You will see that /usr/bin/apt is blocked.

  • Block a specific executable - NotIn operator(csp-not-in-operator-block-process.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorClusterPolicy
    metadata:
      name: csp-in-operator-block-process
    spec:
      severity: 8
      selector:
        matchExpressions:
          - key: namespace
            operator: NotIn
            values:
              - nginx1
      process:
        matchPaths:
          - path: /usr/bin/apt
      action:
        Block

    • Explanation: The purpose of this policy is to block the execution of '/usr/bin/apt' in all containers present in the cluster except that are in the namespace nginx1. For this, we define the 'nginx1' value and operator as 'NotIn' in selector -> matchExpressions and the specific path ('/usr/bin/apt') in process -> matchPaths. Also, we put 'Block' as the action of this policy.

    • Verification: After applying this policy, please get into one of the containers in the namespace 'nginx1' (using "kubectl -n nginx1 exec -it nginx-X-... -- bash") and run '/usr/bin/apt'. You will see that /usr/bin/apt is not blocked. Now try running same command in container inside 'nginx2' namespace and it should not be blocked.

• File Access Restriction

  • Block accessing specific file (csp-in-operator-block-file-access.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorClusterPolicy
    metadata:
      name: csp-in-operator-block-file-access
    spec:
      severity: 8
      selector:
        matchExpressions:
          - key: namespace
            operator: In
            values:
              - nginx2
      file:
        matchPaths:
          - path: /etc/host.conf
            fromSource:
            - path: /usr/bin/cat
      action:
        Block
    

    • Explanation: The purpose of this policy is to block the container within the namespace 'nginx2' to read '/etc/host.conf'.

    • Verification: After applying this policy, please get into the container within the namespace 'nginx2' and run 'cat /etc/host.conf'. You can see the operation is blocked.

  • Block accessing specific file (csp-in-operator-block-file-access.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorClusterPolicy
    metadata:
      name: csp-in-operator-block-file-access
    spec:
      severity: 8
      selector:
        matchExpressions:
          - key: namespace
            operator: NotIn
            values:
              - nginx2
      file:
        matchPaths:
          - path: /etc/host.conf
            fromSource:
            - path: /usr/bin/cat
      action:
        Block
    

    • Explanation: The purpose of this policy is to block read access for '/etc/host.conf' in all the containers except the namespace 'bginx2'.

    • Verification: After applying this policy, please get into the container within the namespace 'nginx2' and run 'cat /etc/host.conf'. You can see the operation is not blocked and can see the content of the file. Now try to run 'cat /etc/host.conf' in container of 'nginx1' namespace, this operation should be blocked.

Note Other operations like Network, Capabilities, Syscalls also behave in same way as in security policy. The difference only lies in how we match the cluster policy with the namespaces.