Compliance Operator scans

The ScanSetting and ScanSettingBinding APIs are recommended to run compliance scans with the Compliance Operator. For more information on these API objects, run:

$ oc explain scansettings

or

$ oc explain scansettingbindings

Running compliance scans

You can run a scan using the Center for Internet Security (CIS) profiles. For convenience, the Compliance Operator creates a ScanSetting object with reasonable defaults on startup. This ScanSetting object is named default.

Procedure

1. Inspect the ScanSetting object by running:

   $ oc describe scansettings default -n openshift-compliance

   Example output

   Name:         default
   Namespace:    openshift-compliance
   Labels:       <none>
   Annotations:  <none>
   API Version:  compliance.openshift.io/v1alpha1
   Kind:         ScanSetting
   Metadata:
     Creation Timestamp:  2022-10-10T14:07:29Z
     Generation:          1
     Managed Fields:
       API Version:  compliance.openshift.io/v1alpha1
       Fields Type:  FieldsV1
       fieldsV1:
         f:rawResultStorage:
           .:
           f:nodeSelector:
             .:
             f:node-role.kubernetes.io/master:
           f:pvAccessModes:
           f:rotation:
           f:size:
           f:tolerations:
         f:roles:
         f:scanTolerations:
         f:schedule:
         f:showNotApplicable:
         f:strictNodeScan:
       Manager:         compliance-operator
       Operation:       Update
       Time:            2022-10-10T14:07:29Z
     Resource Version:  56111
     UID:               c21d1d14-3472-47d7-a450-b924287aec90
   Raw Result Storage:
     Node Selector:
       node-role.kubernetes.io/master:
     Pv Access Modes:
       ReadWriteOnce (1)
     Rotation:  3 (2)
     Size:      1Gi (3)
     Tolerations:
       Effect:              NoSchedule
       Key:                 node-role.kubernetes.io/master
       Operator:            Exists
       Effect:              NoExecute
       Key:                 node.kubernetes.io/not-ready
       Operator:            Exists
       Toleration Seconds:  300
       Effect:              NoExecute
       Key:                 node.kubernetes.io/unreachable
       Operator:            Exists
       Toleration Seconds:  300
       Effect:              NoSchedule
       Key:                 node.kubernetes.io/memory-pressure
       Operator:            Exists
   Roles:
     master (4)
     worker (4)
   Scan Tolerations: (5)
     Operator:           Exists
   Schedule:             0 1 * * * (6)
   Show Not Applicable:  false
   Strict Node Scan:     true
   Events:               <none>

   1	The Compliance Operator creates a persistent volume (PV) that contains the results of the scans. By default, the PV will use access mode ReadWriteOnce because the Compliance Operator cannot make any assumptions about the storage classes configured on the cluster. Additionally, ReadWriteOnce access mode is available on most clusters. If you need to fetch the scan results, you can do so by using a helper pod, which also binds the volume. Volumes that use the ReadWriteOnce access mode can be mounted by only one pod at time, so it is important to remember to delete the helper pods. Otherwise, the Compliance Operator will not be able to reuse the volume for subsequent scans.
   2	The Compliance Operator keeps results of three subsequent scans in the volume; older scans are rotated.
   3	The Compliance Operator will allocate one GB of storage for the scan results.
   4	If the scan setting uses any profiles that scan cluster nodes, scan these node roles.
   5	The default scan setting object scans all the nodes.
   6	The default scan setting object runs scans at 01:00 each day.

   As an alternative to the default scan setting, you can use default-auto-apply, which has the following settings:

   Name:                      default-auto-apply
   Namespace:                 openshift-compliance
   Labels:                    <none>
   Annotations:               <none>
   API Version:               compliance.openshift.io/v1alpha1
   Auto Apply Remediations:   true
   Auto Update Remediations:  true
   Kind:                      ScanSetting
   Metadata:
     Creation Timestamp:  2022-10-18T20:21:00Z
     Generation:          1
     Managed Fields:
       API Version:  compliance.openshift.io/v1alpha1
       Fields Type:  FieldsV1
       fieldsV1:
         f:autoApplyRemediations: (1)
         f:autoUpdateRemediations: (1)
         f:rawResultStorage:
           .:
           f:nodeSelector:
             .:
             f:node-role.kubernetes.io/master:
           f:pvAccessModes:
           f:rotation:
           f:size:
           f:tolerations:
         f:roles:
         f:scanTolerations:
         f:schedule:
         f:showNotApplicable:
         f:strictNodeScan:
       Manager:         compliance-operator
       Operation:       Update
       Time:            2022-10-18T20:21:00Z
     Resource Version:  38840
     UID:               8cb0967d-05e0-4d7a-ac1c-08a7f7e89e84
   Raw Result Storage:
     Node Selector:
       node-role.kubernetes.io/master:
     Pv Access Modes:
       ReadWriteOnce
     Rotation:  3
     Size:      1Gi
     Tolerations:
       Effect:              NoSchedule
       Key:                 node-role.kubernetes.io/master
       Operator:            Exists
       Effect:              NoExecute
       Key:                 node.kubernetes.io/not-ready
       Operator:            Exists
       Toleration Seconds:  300
       Effect:              NoExecute
       Key:                 node.kubernetes.io/unreachable
       Operator:            Exists
       Toleration Seconds:  300
       Effect:              NoSchedule
       Key:                 node.kubernetes.io/memory-pressure
       Operator:            Exists
   Roles:
     master
     worker
   Scan Tolerations:
     Operator:           Exists
   Schedule:             0 1 * * *
   Show Not Applicable:  false
   Strict Node Scan:     true
   Events:               <none>

   1	Setting autoUpdateRemediations and autoApplyRemediations flags to true allows you to easily create ScanSetting objects that auto-remediate without extra steps.

2. Create a ScanSettingBinding object that binds to the default ScanSetting object and scans the cluster using the cis and cis-node profiles. For example:

   apiVersion: compliance.openshift.io/v1alpha1
   kind: ScanSettingBinding
   metadata:
     name: cis-compliance
     namespace: openshift-compliance
   profiles:
     - name: ocp4-cis-node
       kind: Profile
       apiGroup: compliance.openshift.io/v1alpha1
     - name: ocp4-cis
       kind: Profile
       apiGroup: compliance.openshift.io/v1alpha1
   settingsRef:
     name: default
     kind: ScanSetting
     apiGroup: compliance.openshift.io/v1alpha1

3. Create the ScanSettingBinding object by running:

   $ oc create -f <file-name>.yaml -n openshift-compliance

   At this point in the process, the ScanSettingBinding object is reconciled and based on the Binding and the Bound settings. The Compliance Operator creates a ComplianceSuite object and the associated ComplianceScan objects.

4. Follow the compliance scan progress by running:

   $ oc get compliancescan -w -n openshift-compliance

   The scans progress through the scanning phases and eventually reach the DONE phase when complete. In most cases, the result of the scan is NON-COMPLIANT. You can review the scan results and start applying remediations to make the cluster compliant. See Managing Compliance Operator remediation for more information.

Scheduling the result server pod on a worker node

The result server pod mounts the persistent volume (PV) that stores the raw Asset Reporting Format (ARF) scan results. The nodeSelector and tolerations attributes enable you to configure the location of the result server pod.

This is helpful for those environments where control plane nodes are not permitted to mount persistent volumes.

Procedure

• Create a ScanSetting custom resource (CR) for the Compliance Operator:

  1. Define the ScanSetting CR, and save the YAML file, for example, rs-workers.yaml:

     apiVersion: compliance.openshift.io/v1alpha1
     kind: ScanSetting
     metadata:
       name: rs-on-workers
       namespace: openshift-compliance
     rawResultStorage:
       nodeSelector:
         node-role.kubernetes.io/worker: "" (1)
       pvAccessModes:
       - ReadWriteOnce
       rotation: 3
       size: 1Gi
       tolerations:
       - operator: Exists (2)
     roles:
     - worker
     - master
     scanTolerations:
       - operator: Exists
     schedule: 0 1 * * *

     1	The Compliance Operator uses this node to store scan results in ARF format.
     2	The result server pod tolerates all taints.

  2. To create the ScanSetting CR, run the following command:

     $ oc create -f rs-workers.yaml

Verification

• To verify that the ScanSetting object is created, run the following command:

  $ oc get scansettings rs-on-workers -n openshift-compliance -o yaml

  Example output

  apiVersion: compliance.openshift.io/v1alpha1
  kind: ScanSetting
  metadata:
    creationTimestamp: "2021-11-19T19:36:36Z"
    generation: 1
    name: rs-on-workers
    namespace: openshift-compliance
    resourceVersion: "48305"
    uid: 43fdfc5f-15a7-445a-8bbc-0e4a160cd46e
  rawResultStorage:
    nodeSelector:
      node-role.kubernetes.io/worker: ""
    pvAccessModes:
    - ReadWriteOnce
    rotation: 3
    size: 1Gi
    tolerations:
    - operator: Exists
  roles:
  - worker
  - master
  scanTolerations:
  - operator: Exists
  schedule: 0 1 * * *
  strictNodeScan: true

ScanSetting Custom Resource

The ScanSetting Custom Resource now allows you to override the default CPU and memory limits of scanner pods through the scan limits attribute. The Compliance Operator will use defaults of 500Mi memory, 100m CPU for the scanner container, and 200Mi memory with 100m CPU for the api-resource-collector container. To set the memory limits of the Operator, modify the Subscription object if installed through OLM or the Operator deployment itself.

To increase the default CPU and memory limits of the Compliance Operator, see Increasing Compliance Operator resource limits.

Applying resource requests and limits

When the kubelet starts a container as part of a Pod, the kubelet passes that container’s requests and limits for memory and CPU to the container runtime. In Linux, the container runtime configures the kernel cgroups that apply and enforce the limits you defined.

The CPU limit defines how much CPU time the container can use. During each scheduling interval, the Linux kernel checks to see if this limit is exceeded. If so, the kernel waits before allowing the cgroup to resume execution.

If several different containers (cgroups) want to run on a contended system, workloads with larger CPU requests are allocated more CPU time than workloads with small requests. The memory request is used during Pod scheduling. On a node that uses cgroups v2, the container runtime might use the memory request as a hint to set memory.min and memory.low values.

If a container attempts to allocate more memory than this limit, the Linux kernel out-of-memory subsystem activates and intervenes by stopping one of the processes in the container that tried to allocate memory. The memory limit for the Pod or container can also apply to pages in memory-backed volumes, such as an emptyDir.

The kubelet tracks tmpfs emptyDir volumes as container memory is used, rather than as local ephemeral storage. If a container exceeds its memory request and the node that it runs on becomes short of memory overall, the Pod’s container might be evicted.

Scheduling Pods with container resource requests

When a Pod is created, the scheduler selects a Node for the Pod to run on. Each node has a maximum capacity for each resource type in the amount of CPU and memory it can provide for the Pods. The scheduler ensures that the sum of the resource requests of the scheduled containers is less than the capacity nodes for each resource type.

Although memory or CPU resource usage on nodes is very low, the scheduler might still refuse to place a Pod on a node if the capacity check fails to protect against a resource shortage on a node.

For each container, you can specify the following resource limits and request:

spec.containers[].resources.limits.cpu
spec.containers[].resources.limits.memory
spec.containers[].resources.limits.hugepages-<size>
spec.containers[].resources.requests.cpu
spec.containers[].resources.requests.memory
spec.containers[].resources.requests.hugepages-<size>

Although you can specify requests and limits for only individual containers, it is also useful to consider the overall resource requests and limits for a pod. For a particular resource, a container resource request or limit is the sum of the resource requests or limits of that type for each container in the pod.

Example container resource requests and limits

apiVersion: v1
kind: Pod
metadata:
  name: frontend
spec:
  containers:
  - name: app
    image: images.my-company.example/app:v4
    resources:
      requests: (1)
        memory: "64Mi"
        cpu: "250m"
      limits: (2)
        memory: "128Mi"
        cpu: "500m"
  - name: log-aggregator
    image: images.my-company.example/log-aggregator:v6
    resources:
      requests:
        memory: "64Mi"
        cpu: "250m"
      limits:
        memory: "128Mi"
        cpu: "500m"