Enabling the API Audit Log in Downstream Clusters

Kubernetes auditing provides a security-relevant chronological set of records about a cluster. Kube-apiserver performs auditing. Requests generate an event at each stage of its execution, which is then preprocessed according to a certain policy and written to a backend. The policy determines what’s recorded and the backend persists the records.

You might want to configure the audit log as part of compliance with the Center for Internet Security (CIS) Kubernetes Benchmark controls.

For configuration details, refer to the official Kubernetes documentation.

• RKE2/K3s
• RKE1

note

This feature is available in Rancher v2.7.2 and above.

As a prerequisite, you need to create a secret or configmap which will be the source of the audit policy.

The secret or configmap must meet the following two requirements:

1. It must be in the fleet-default namespace where the Cluster object exists.
2. It must have the annotation rke.cattle.io/object-authorized-for-clusters: cluster-name1,cluster-name2 which permits the target clusters to use it.

tip

Rancher Dashboard provides an easy-to-use form for creating the secret or configmap.

Example:

apiVersion: v1
data:
  audit-policy: >-
    IyBMb2cgYWxsIHJlcXVlc3RzIGF0IHRoZSBNZXRhZGF0YSBsZXZlbC4KYXBpVmVyc2lvbjogYXVkaXQuazhzLmlvL3YxCmtpbmQ6IFBvbGljeQpydWxlczoKLSBsZXZlbDogTWV0YWRhdGE=
kind: Secret
metadata:
  annotations:
    rke.cattle.io/object-authorized-for-clusters: cluster1
  name: name1
  namespace: fleet-default

The audit log can be enabled and configured by editing the cluster in YAML and utilizing the machineSelectorFiles and machineGlobalConfig directives.

Example:

apiVersion: provisioning.cattle.io/v1
kind: Cluster
spec:
  rkeConfig:
    machineGlobalConfig:
      kube-apiserver-arg:
        - audit-policy-file=<customized-path>/dev-audit-policy.yaml
        - audit-log-path=<customized-path>/dev-audit.logs
    machineSelectorFiles:
      - fileSources:
          - configMap:
              name: ''
            secret:
              items:
                - key: audit-policy
                  path: <customized-path>/dev-audit-policy.yaml
              name: dev-audit-policy
        machineLabelSelector:
          matchLabels:
            rke.cattle.io/control-plane-role: 'true'

For more information about cluster configuration, refer to the REK2 or K3s cluster configuration reference pages.

The audit log can be enabled and configured by editing the cluster with YAML.

When the audit log is enabled, RKE1 default values will be applied.

# 
# Rancher Config
# 
rancher_kubernetes_engine_config:
  services:
    kube-api:
      audit_log:
        enabled: true

You can customize the audit log by using the configuration directive.

# 
# Rancher Config
# 
rancher_kubernetes_engine_config:
  services:
    kube-api:
      audit_log:
        enabled: true
        configuration:
          max_age: 6
          max_backup: 6
          max_size: 110
          path: /var/log/kube-audit/audit-log.json
          format: json
          policy:
            apiVersion: audit.k8s.io/v1 # This is required.
            kind: Policy
            omitStages:
              - "RequestReceived"
            rules:
              # Log pod changes at RequestResponse level
              - level: RequestResponse
                resources:
                  - group: ""
                    # Resource "pods" doesn't match requests to any subresource of pods,
                    # which is consistent with the RBAC policy.
                    resources: ["pods"]
              # Log "pods/log", "pods/status" at Metadata level
              - level: Metadata
                resources:
                  - group: ""
                    resources: ["pods/log", "pods/status"]

For configuration details, refer to the official RKE1 documentation.