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Center for Internet Security (CIS) Kubernetes benchmark

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As a secure service, Azure Kubernetes Service (AKS) complies with SOC, ISO, PCI DSS, and HIPAA standards. This article covers the security hardening applied to AKS based on the CIS Kubernetes benchmark. For more information about AKS security, see Security concepts for applications and clusters in Azure Kubernetes Service (AKS). For more information on the CIS benchmark, see Center for Internet Security (CIS) Benchmarks.

Kubernetes CIS benchmark

The following are the results from the CIS Kubernetes V1.27 Benchmark v1.9.0 recommendations on AKS. The results are applicable to AKS 1.27.x through AKS 1.29.x.

Security levels

CIS benchmarks provide two levels of security settings:

  • L1, or Level 1, recommends essential basic security requirements that can be configured on any system and should cause little or no interruption of service or reduced functionality.
  • L2, or Level 2, recommends security settings for environments requiring greater security that could result in some reduced functionality.

Assessment status

An assessment status is included for every recommendation. The assessment status indicates whether the given recommendation can be automated or requires manual steps to implement. Both statuses are equally important and are determined and supported as defined below:

  • Automated: Represents recommendations for which assessment of a technical control can be fully automated and validated to a pass/fail state. Recommendations will include the necessary information to implement automation.
  • Manual: Represents recommendations for which assessment of a technical control cannot be fully automated and requires all or some manual steps to validate that the configured state is set as expected. The expected state can vary depending on the environment.

Automated recommendations affect the benchmark score if they aren't applied, while Manual recommendations don't.

Attestation status

Recommendations can have one of the following attestation statuses:

  • Pass: The recommendation has been applied.
  • Fail: The recommendation hasn't been applied.
  • N/A: The recommendation relates to manifest file permission requirements that aren't relevant to AKS. Kubernetes clusters by default use a manifest model to deploy the control plane pods, which rely on files from the node VM. The CIS Kubernetes benchmark recommends these files must have certain permission requirements. AKS clusters use a Helm chart to deploy control plane pods and don't rely on files in the node VM.
  • Depends on Environment: The recommendation is applied in the user's specific environment and isn't controlled by AKS. Automated recommendations affect the benchmark score whether the recommendation applies to the user's specific environment or not.
  • Equivalent Control: The recommendation has been implemented in a different, equivalent manner.

Benchmark details

CIS ID Recommendation description Assessment status Level Status
1 Control Plane Components
1.1 Control Plane Node Configuration Files
1.1.1 Ensure that the API server pod specification file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.2 Ensure that the API server pod specification file ownership is set to root:root Automated L1 N/A
1.1.3 Ensure that the controller manager pod specification file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.4 Ensure that the controller manager pod specification file ownership is set to root:root Automated L1 N/A
1.1.5 Ensure that the scheduler pod specification file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.6 Ensure that the scheduler pod specification file ownership is set to root:root Automated L1 N/A
1.1.7 Ensure that the etcd pod specification file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.8 Ensure that the etcd pod specification file ownership is set to root:root Automated L1 N/A
1.1.9 Ensure that the Container Network Interface file permissions are set to 600 or more restrictive Manual L1 N/A
1.1.10 Ensure that the Container Network Interface file ownership is set to root:root Manual L1 N/A
1.1.11 Ensure that the etcd data directory permissions are set to 700 or more restrictive Automated L1 N/A
1.1.12 Ensure that the etcd data directory ownership is set to etcd:etcd Automated L1 N/A
1.1.13 Ensure that the admin.conf file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.14 Ensure that the admin.conf file ownership is set to root:root Automated L1 N/A
1.1.15 Ensure that the scheduler.conf file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.16 Ensure that the scheduler.conf file ownership is set to root:root Automated L1 N/A
1.1.17 Ensure that the controller-manager.conf file permissions are set to 600 or more restrictive Automated L1 N/A
1.1.18 Ensure that the controller-manager.conf file ownership is set to root:root Automated L1 N/A
1.1.19 Ensure that the Kubernetes PKI directory and file ownership is set to root:root Automated L1 N/A
1.1.20 Ensure that the Kubernetes PKI certificate file permissions are set to 600 or more restrictive Manual L1 N/A
1.1.21 Ensure that the Kubernetes PKI key file permissions are set to 600 Manual L1 N/A
1.2 API Server
1.2.1 Ensure that the --anonymous-auth argument is set to false Manual L1 Pass
1.2.2 Ensure that the --token-auth-file parameter is not set Automated L1 Fail
1.2.3 Ensure that --DenyServiceExternalIPs is not set Manual L1 Fail
1.2.4 Ensure that the --kubelet-client-certificate and --kubelet-client-key arguments are set as appropriate Automated L1 Pass
1.2.5 Ensure that the --kubelet-certificate-authority argument is set as appropriate Automated L1 Fail
1.2.6 Ensure that the --authorization-mode argument is not set to AlwaysAllow Automated L1 Pass
1.2.7 Ensure that the --authorization-mode argument includes Node Automated L1 Pass
1.2.8 Ensure that the --authorization-mode argument includes RBAC Automated L1 Pass
1.2.9 Ensure that the admission control plugin EventRateLimit is set Manual L1 Fail
1.2.10 Ensure that the admission control plugin AlwaysAdmit is not set Automated L1 Pass
1.2.11 Ensure that the admission control plugin AlwaysPullImages is set Manual L1 Fail
1.2.12 Ensure that the admission control plugin ServiceAccount is set Automated L2 Fail
1.2.13 Ensure that the admission control plugin NamespaceLifecycle is set Automated L2 Pass
1.2.14 Ensure that the admission control plugin NodeRestriction is set Automated L2 Pass
1.2.15 Ensure that the --profiling argument is set to false Automated L1 Pass
1.2.16 Ensure that the --audit-log-path argument is set Automated L1 Pass
1.2.17 Ensure that the --audit-log-maxage argument is set to 30 or as appropriate Automated L1 Equivalent Control
1.2.18 Ensure that the --audit-log-maxbackup argument is set to 10 or as appropriate Automated L1 Equivalent Control
1.2.19 Ensure that the --audit-log-maxsize argument is set to 100 or as appropriate Automated L1 Pass
1.2.20 Ensure that the --request-timeout argument is set as appropriate Manual L1 Pass
1.2.21 Ensure that the --service-account-lookup argument is set to true Automated L1 Pass
1.2.22 Ensure that the --service-account-key-file argument is set as appropriate Automated L1 Pass
1.2.23 Ensure that the --etcd-certfile and --etcd-keyfile arguments are set as appropriate Automated L1 Pass
1.2.24 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate Automated L1 Pass
1.2.25 Ensure that the --client-ca-file argument is set as appropriate Automated L1 Pass
1.2.26 Ensure that the --etcd-cafile argument is set as appropriate Automated L1 Pass
1.2.27 Ensure that the --encryption-provider-config argument is set as appropriate Manual L1 Depends on Environment
1.2.28 Ensure that encryption providers are appropriately configured Manual L1 Depends on Environment
1.2.29 Ensure that the API Server only makes use of Strong Cryptographic Ciphers Manual L1 Pass
1.3 Controller Manager
1.3.1 Ensure that the --terminated-pod-gc-threshold argument is set as appropriate Manual L1 Pass
1.3.2 Ensure that the --profiling argument is set to false Automated L1 Pass
1.3.3 Ensure that the --use-service-account-credentials argument is set to true Automated L1 Pass
1.3.4 Ensure that the --service-account-private-key-file argument is set as appropriate Automated L1 Pass
1.3.5 Ensure that the --root-ca-file argument is set as appropriate Automated L1 Pass
1.3.6 Ensure that the RotateKubeletServerCertificate argument is set to true Automated L2 Pass
1.3.7 Ensure that the --bind-address argument is set to 127.0.0.1 Automated L1 Equivalent Control
1.4 Scheduler
1.4.1 Ensure that the --profiling argument is set to false Automated L1 Pass
1.4.2 Ensure that the --bind-address argument is set to 127.0.0.1 Automated L1 Equivalent Control
2 etcd
2.1 Ensure that the --cert-file and --key-file arguments are set as appropriate Automated L1 Pass
2.2 Ensure that the --client-cert-auth argument is set to true Automated L1 Pass
2.3 Ensure that the --auto-tls argument is not set to true Automated L1 Pass
2.4 Ensure that the --peer-cert-file and --peer-key-file arguments are set as appropriate Automated L1 Pass
2.5 Ensure that the --peer-client-cert-auth argument is set to true Automated L1 Pass
2.6 Ensure that the --peer-auto-tls argument is not set to true Automated L1 Pass
2.7 Ensure that a unique Certificate Authority is used for etcd Manual L2 Pass
3 Control Plane Configuration
3.1 Authentication and Authorization
3.1.1 Client certificate authentication should not be used for users Manual L1 Pass
3.1.2 Service account token authentication should not be used for users Manual L1 Pass
3.1.3 Bootstrap token authentication should not be used for users Manual L1 Pass
3.2 Logging
3.2.1 Ensure that a minimal audit policy is created Manual L1 Pass
3.2.2 Ensure that the audit policy covers key security concerns Manual L2 Pass
4 Worker Nodes
4.1 Worker Node Configuration Files
4.1.1 Ensure that the kubelet service file permissions are set to 600 or more restrictive Automated L1 Pass
4.1.2 Ensure that the kubelet service file ownership is set to root:root Automated L1 Pass
4.1.3 If a proxy kubeconfig file exists, ensure permissions are set to 600 or more restrictive Manual L1 N/A
4.1.4 If a proxy kubeconfig file exists, ensure ownership is set to root:root Manual L1 N/A
4.1.5 Ensure that the --kubeconfig kubelet.conf file permissions are set to 600 or more restrictive Automated L1 Pass
4.1.6 Ensure that the --kubeconfig kubelet.conf file ownership is set to root:root Automated L1 Pass
4.1.7 Ensure that the certificate authorities file permissions are set to 600 or more restrictive Manual L1 Pass
4.1.8 Ensure that the client certificate authorities file ownership is set to root:root Manual L1 Pass
4.1.9 If the kubelet config.yaml configuration file is being used, ensure permissions set to 600 or more restrictive Automated L1 Pass
4.1.10 If the kubelet config.yaml configuration file is being used, ensure file ownership is set to root:root Automated L1 Pass
4.2 Kubelet
4.2.1 Ensure that the --anonymous-auth argument is set to false Automated L1 Pass
4.2.2 Ensure that the --authorization-mode argument is not set to AlwaysAllow Automated L1 Pass
4.2.3 Ensure that the --client-ca-file argument is set as appropriate Automated L1 Pass
4.2.4 Ensure that the --read-only-port argument is set to 0 Manual L1 Pass
4.2.5 Ensure that the --streaming-connection-idle-timeout argument is not set to 0 Manual L1 Pass
4.2.6 Ensure that the --make-iptables-util-chains argument is set to true Automated L1 Pass
4.2.7 Ensure that the --hostname-override argument is not set Manual L1 Pass
4.2.8 Ensure that the --eventRecordQPS argument is set to a level which ensures appropriate event capture Manual L2 Pass
4.2.9 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate Manual L1 Pass
4.2.10 Ensure that the --rotate-certificates argument is not set to false Automated L1 Pass
4.2.11 Verify that the RotateKubeletServerCertificate argument is set to true Manual L1 Fail
4.2.12 Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers Manual L1 Pass
4.2.13 Ensure that a limit is set on pod PIDs Manual L1 Pass
4.3 kube-proxy
4.3.1 Ensure that the kube-proxy metrics service is bound to localhost Automated L1 Pass
5 Policies
5.1 RBAC and Service Accounts
5.1.1 Ensure that the cluster-admin role is only used where required Automated L1 Depends on Environment
5.1.2 Minimize access to secrets Automated L1 Depends on Environment
5.1.3 Minimize wildcard use in Roles and ClusterRoles Automated L1 Depends on Environment
5.1.4 Minimize access to create pods Automated L1 Depends on Environment
5.1.5 Ensure that default service accounts are not actively used Automated L1 Depends on Environment
5.1.6 Ensure that Service Account Tokens are only mounted where necessary Automated L1 Depends on Environment
5.1.7 Avoid use of system:masters group Manual L1 Depends on Environment
5.1.8 Limit use of the Bind, Impersonate and Escalate permissions in the Kubernetes cluster Manual L1 Depends on Environment
5.1.9 Minimize access to create persistent volumes Manual L1 Depends on Environment
5.1.10 Minimize access to the proxy sub-resource of nodes Manual L1 Depends on Environment
5.1.11 Minimize access to the approval sub-resource of certificatesigningrequests objects Manual L1 Depends on Environment
5.1.12 Minimize access to webhook configuration objects Manual L1 Depends on Environment
5.1.13 Minimize access to the service account token creation Manual L1 Depends on Environment
5.2 Pod Security Standards
5.2.1 Ensure that the cluster has at least one active policy control mechanism in place Manual L1 Depends on Environment
5.2.2 Minimize the admission of privileged containers Manual L1 Depends on Environment
5.2.3 Minimize the admission of containers wishing to share the host process ID namespace Manual L1 Depends on Environment
5.2.4 Minimize the admission of containers wishing to share the host IPC namespace Manual L1 Depends on Environment
5.2.5 Minimize the admission of containers wishing to share the host network namespace Manual L1 Depends on Environment
5.2.6 Minimize the admission of containers with allowPrivilegeEscalation Manual L1 Depends on Environment
5.2.7 Minimize the admission of root containers Manual L2 Depends on Environment
5.2.8 Minimize the admission of containers with the NET_RAW capability Manual L1 Depends on Environment
5.2.9 Minimize the admission of containers with added capabilities Manual L1 Depends on Environment
5.2.10 Minimize the admission of containers with capabilities assigned Manual L2 Depends on Environment
5.2.11 Minimize the admission of Windows HostProcess Containers Manual L1 Depends on Environment
5.2.12 Minimize the admission of HostPath volumes Manual L1 Depends on Environment
5.2.13 Minimize the admission of containers which use HostPorts Manual L1 Depends on Environment
5.3 Network Policies and CNI
5.3.1 Ensure that the CNI in use supports Network Policies Manual L1 Pass
5.3.2 Ensure that all Namespaces have Network Policies defined Manual L2 Depends on Environment
5.4 Secrets Management
5.4.1 Prefer using secrets as files over secrets as environment variables Manual L2 Depends on Environment
5.4.2 Consider external secret storage Manual L2 Depends on Environment
5.5 Extensible Admission Control
5.5.1 Configure Image Provenance using ImagePolicyWebhook admission controller Manual L2 Fail
5.6 General Policies
5.6.1 Create administrative boundaries between resources using namespaces Manual L1 Depends on Environment
5.6.2 Ensure that the seccomp profile is set to docker/default in your pod definitions Manual L2 Depends on Environment
5.6.3 Apply Security Context to Your Pods and Containers Manual L2 Depends on Environment
5.6.4 The default namespace should not be used Manual L2 Depends on Environment

Note

In addition to the Kubernetes CIS benchmark, there is an AKS CIS benchmark available as well.

Additional notes

  • The security hardened OS is built and maintained specifically for AKS and is not supported outside of the AKS platform.
  • To further reduce the attack surface area, some unnecessary kernel module drivers are disabled in the OS.

Next steps

For more information about AKS security, see the following articles: