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.

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

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorClusterPolicy
    metadata:
      name: csp-matchlabels-in-block-process
    spec:
      severity: 8
      selector:
        matchExpressions:
          - key: namespace
            operator: In
            values:
              - nginx1
          - key: label
            operator: In
            values:
              - app=nginx
              - app=nginx-dev
      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 workloads who match the labels app=nginx OR app=nginx-dev present in the namespace nginx1 . For this, we define the 'nginx1' as value and operator as 'In' for key namespace AND app=nginx & app=nginx-dev value and operator as 'In' for key label 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. apt won't be blocked in a workload that doesn't have labels app=nginx OR app=nginx-dev in namespace nginx1 and all the workloads across other namespaces.

  • Block accessing specific executable matching labels, NotIn operator (csp-matchlabels-not-in-block-process.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorClusterPolicy
    metadata:
      name: csp-matchlabels-not-in-block-process
    spec:
      severity: 8
      selector:
        matchExpressions:
          - key: namespace
            operator: NotIn
            values:
              - nginx2
          - key: label
            operator: NotIn
            values:
              - app=nginx
      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 the workloads who doesn't match the labels app=nginx AND not present in the namespace nginx2 . For this, we define the 'nginx2' as value and operator as 'NotIn' for key namespace AND app=nginx value and operator as 'NotIn' for key label 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 exec into any container within the namespace 'nginx2' and run '/usr/bin/apt'. You can see the operation is blocked. Then try to do same in other workloads present in different namespace and if they don't have label app=nginx, the operation will be blocked, in case container have label app=nginx, operation won't 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: 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.