CIS compliance

The Center for Internet Security (CIS) maintains a Kubernetes benchmark which helps ensure clusters are deployed in accordance with security best practices. Charmed Kubernetes includes support for the kube-bench utility, which reports how well a cluster complies with this benchmark. This page highlights compliance requirements as well as details on running the benchmark and analysing test results.

Compliance Requirements

Charmed Kubernetes is compliant by default. Key configuration changes from releases prior to 1.19 include the following:

kubernetes-control-plane

Set authorization.mode = Node,RBAC

kube-apiserver must not include AlwaysAllow as an authorization mode. This is set by the authorization-mode config option on the kubernetes-control-plane charm (Node,RBAC by default).

Set encryption-provider-config

kube-apiserver must set encryption-provider-config to the path of a valid EncryptionConfig manifest (/var/snap/kube-apiserver/common/encryption/encryption_config.yaml by default).

Disable insecure-bind-address and insecure-port

kube-apiserver must not respond to requests over an insecure address.

Enable NodeRestriction and PodSecurityPolicy plugins

kube-apiserver must enable the NodeRestriction and PodSecurityPolicy admission control plugins.

Disable profiling

kube-apiserver, kube-controller-manager, and kube-scheduler must set profiling=False.

Set terminated-pod-gc-threshold

kube-controller-manager must set a value for terminated-pod-gc-threshold (12500 by default).

Disable token-auth-file

kube-apiserver must not use file-based authentication. Charmed Kubernetes now deploys a webhook authentication service that compares API requests to Kubernetes secrets. If needed, any existing entries in known_tokens.csv are migrated to secrets on charm upgrade.

kubernetes-worker

Set authorization.mode = Webhook

kubelet must ask the API server whether a given request is authorized.

Enable protect-kernel-defaults

kubelet must not start if any of the kernel tunables are different from the kubelet defaults.

Disable read-only-port

kubelet must not serve data to an unauthenticated request. Typically, these requests come from a metrics collecting service. If needed, adjust any services that access the kubelet read-only-port (10255 by default) to instead use the secure port (10250 by default).

Run the benchmark

The kubernetes-control-plane, kubernetes-worker, and etcd charms used by Charmed Kubernetes include a cis-benchmark action that will install, configure, and run the benchmark on the respective components. Run this action on the units you wish to test with the following:

juju run-action --wait etcd/0 cis-benchmark

By default, the action will display a summary of any issues found as well as the command that was executed on the unit. A report command is included to facilitate transferring the full benchmark report to a local machine for analysis.

results:
  cmd: /home/ubuntu/kube-bench/kube-bench -D /home/ubuntu/kube-bench/cfg-ck
    --benchmark cis-1.5 --noremediations --noresults run --targets etcd
  report: juju scp etcd/0:/home/ubuntu/kube-bench-results/results-text-49681_7h .
  summary: |
    == Summary ==
    7 checks PASS
    0 checks FAIL
    0 checks WARN
    4 checks INFO
status: completed

Configure the benchmark

The following parameters can be adjusted to change the default action behavior. See the descriptions in the actions.yaml file for additional supported values beyond the defaults.

apply

When a failure is detected, this action can attempt to automatically fix it. This parameter is none by default, meaning the action will not attempt to apply any automatic remediations.

config

Specify an archive of custom configuration scripts to use during the benchmark. This parameter is set by default to an archive that is known to work with snap-related components.

release

Specify the kube-bench release to install and run. This parameter is set by default to a release that is known to work with snap-related components.

Example use case

Run the CIS benchmark on the kubernetes-worker charm using a custom configuration archive:

juju run-action --wait kubernetes-worker/0 cis-benchmark \
  config='https://github.com/charmed-kubernetes/kube-bench-config/archive/cis-1.5.zip'

results:
  cmd: /home/ubuntu/kube-bench/kube-bench -D /home/ubuntu/kube-bench/cfg-ck
    --benchmark cis-1.5 --noremediations --noresults run --targets node
  report: juju scp kubernetes-worker/0:/home/ubuntu/kube-bench-results/results-text-nmmlsvy3 .
  summary: |
    == Summary ==
    16 checks PASS
    4 checks FAIL
    3 checks WARN
    0 checks INFO
status: completed

Attempt to apply all known fixes to the failing benchmark tests using the same configuration archive:

juju run-action --wait kubernetes-worker/0 cis-benchmark \
  apply='dangerous' \
  config='https://github.com/charmed-kubernetes/kube-bench-config/archive/cis-1.5.zip'

results:
  cmd: /home/ubuntu/kube-bench/kube-bench -D /home/ubuntu/kube-bench/cfg-ck
    --benchmark cis-1.5 --noremediations --noresults run --targets node
  report: juju scp kubernetes-worker/0:/home/ubuntu/kube-bench-results/results-json-dozp8j3z .
  summary: Applied 4 remediations. Re-run with "apply=none" to generate a new report.
status: completed

Re-run the earlier action to verify previous failures have been fixed:

juju run-action --wait kubernetes-worker/0 cis-benchmark \
  config='https://github.com/charmed-kubernetes/kube-bench-config/archive/cis-1.5.zip'

results:
  cmd: /home/ubuntu/kube-bench/kube-bench -D /home/ubuntu/kube-bench/cfg-ck
    --benchmark cis-1.5 --noremediations --noresults run --targets node
  report: juju scp kubernetes-worker/0:/home/ubuntu/kube-bench-results/results-text-4agbktbf .
  summary: |
    == Summary ==
    20 checks PASS
    0 checks FAIL
    3 checks WARN
    0 checks INFO
status: completed

Remove applied remediations

The cis-benchmark action does not track individual remediations that it applies. However, it does support removing all configuration that it may have set on a unit. To clear this data, set the apply parameter to reset:

juju run-action --wait kubernetes-worker/0 cis-benchmark \
  apply='reset'

results:
  summary: Reset is complete. Re-run with "apply=none" to generate a new report.
status: completed