Center for Internet Security (CIS) Kubernetes benchmark

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 V1.20 Benchmark v1.0.0 recommendations on AKS.

Scored recommendations affect the benchmark score if they are not applied, while Not Scored recommendations don't.

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.

Recommendations can have one of the following statuses:

  • Pass - The recommendation has been applied.
  • Fail - The recommendation has not been applied.
  • N/A - The recommendation relates to manifest file permission requirements that are not 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 is not controlled by AKS. Scored 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.
CIS ID Recommendation description Scoring Type 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 644 or more restrictive Scored L1 N/A
1.1.2 Ensure that the API server pod specification file ownership is set to root:root Scored L1 N/A
1.1.3 Ensure that the controller manager pod specification file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.4 Ensure that the controller manager pod specification file ownership is set to root:root Scored L1 N/A
1.1.5 Ensure that the scheduler pod specification file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.6 Ensure that the scheduler pod specification file ownership is set to root:root Scored L1 N/A
1.1.7 Ensure that the etcd pod specification file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.8 Ensure that the etcd pod specification file ownership is set to root:root Scored L1 N/A
1.1.9 Ensure that the Container Network Interface file permissions are set to 644 or more restrictive Not Scored L1 N/A
1.1.10 Ensure that the Container Network Interface file ownership is set to root:root Not Scored L1 N/A
1.1.11 Ensure that the etcd data directory permissions are set to 700 or more restrictive Scored L1 N/A
1.1.12 Ensure that the etcd data directory ownership is set to etcd:etcd Scored L1 N/A
1.1.13 Ensure that the admin.conf file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.14 Ensure that the admin.conf file ownership is set to root:root Scored L1 N/A
1.1.15 Ensure that the scheduler.conf file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.16 Ensure that the scheduler.conf file ownership is set to root:root Scored L1 N/A
1.1.17 Ensure that the controller-manager.conf file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.18 Ensure that the controller-manager.conf file ownership is set to root:root Scored L1 N/A
1.1.19 Ensure that the Kubernetes PKI directory and file ownership is set to root:root Scored L1 N/A
1.1.20 Ensure that the Kubernetes PKI certificate file permissions are set to 644 or more restrictive Scored L1 N/A
1.1.21 Ensure that the Kubernetes PKI key file permissions are set to 600 Scored L1 N/A
1.2 API Server
1.2.1 Ensure that the --anonymous-auth argument is set to false Not Scored L1 Pass
1.2.2 Ensure that the --basic-auth-file argument is not set Scored L1 Pass
1.2.3 Ensure that the --token-auth-file parameter is not set Scored L1 Fail
1.2.4 Ensure that the --kubelet-https argument is set to true Scored L1 Equivalent Control
1.2.5 Ensure that the --kubelet-client-certificate and --kubelet-client-key arguments are set as appropriate Scored L1 Pass
1.2.6 Ensure that the --kubelet-certificate-authority argument is set as appropriate Scored L1 Equivalent Control
1.2.7 Ensure that the --authorization-mode argument is not set to AlwaysAllow Scored L1 Pass
1.2.8 Ensure that the --authorization-mode argument includes Node Scored L1 Pass
1.2.9 Ensure that the --authorization-mode argument includes RBAC Scored L1 Pass
1.2.10 Ensure that the admission control plugin EventRateLimit is set Not Scored L1 Fail
1.2.11 Ensure that the admission control plugin AlwaysAdmit is not set Scored L1 Pass
1.2.12 Ensure that the admission control plugin AlwaysPullImages is set Not Scored L1 Fail
1.2.13 Ensure that the admission control plugin SecurityContextDeny is set if PodSecurityPolicy is not used Not Scored L1 Fail
1.2.14 Ensure that the admission control plugin ServiceAccount is set Scored L1 Pass
1.2.15 Ensure that the admission control plugin NamespaceLifecycle is set Scored L1 Pass
1.2.16 Ensure that the admission control plugin PodSecurityPolicy is set Scored L1 Fail
1.2.17 Ensure that the admission control plugin NodeRestriction is set Scored L1 Fail
1.2.18 Ensure that the --insecure-bind-address argument is not set Scored L1 Fail
1.2.19 Ensure that the --insecure-port argument is set to 0 Scored L1 Pass
1.2.20 Ensure that the --secure-port argument is not set to 0 Scored L1 Pass
1.2.21 Ensure that the --profiling argument is set to false Scored L1 Pass
1.2.22 Ensure that the --audit-log-path argument is set Scored L1 Pass
1.2.23 Ensure that the --audit-log-maxage argument is set to 30 or as appropriate Scored L1 Equivalent Control
1.2.24 Ensure that the --audit-log-maxbackup argument is set to 10 or as appropriate Scored L1 Equivalent Control
1.2.25 Ensure that the --audit-log-maxsize argument is set to 100 or as appropriate Scored L1 Pass
1.2.26 Ensure that the --request-timeout argument is set as appropriate Scored L1 Pass
1.2.27 Ensure that the --service-account-lookup argument is set to true Scored L1 Pass
1.2.28 Ensure that the --service-account-key-file argument is set as appropriate Scored L1 Pass
1.2.29 Ensure that the --etcd-certfile and --etcd-keyfile arguments are set as appropriate Scored L1 Pass
1.2.30 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate Scored L1 Pass
1.2.31 Ensure that the --client-ca-file argument is set as appropriate Scored L1 Pass
1.2.32 Ensure that the --etcd-cafile argument is set as appropriate Scored L1 Pass
1.2.33 Ensure that the --encryption-provider-config argument is set as appropriate Scored L1 Fail
1.2.34 Ensure that encryption providers are appropriately configured Scored L1 Fail
1.2.35 Ensure that the API Server only makes use of Strong Cryptographic Ciphers Not Scored L1 Pass
1.3 Controller Manager
1.3.1 Ensure that the --terminated-pod-gc-threshold argument is set as appropriate Scored L1 Pass
1.3.2 Ensure that the --profiling argument is set to false Scored L1 Pass
1.3.3 Ensure that the --use-service-account-credentials argument is set to true Scored L1 Pass
1.3.4 Ensure that the --service-account-private-key-file argument is set as appropriate Scored L1 Pass
1.3.5 Ensure that the --root-ca-file argument is set as appropriate Scored L1 Pass
1.3.6 Ensure that the RotateKubeletServerCertificate argument is set to true Scored L2 Pass
1.3.7 Ensure that the --bind-address argument is set to 127.0.0.1 Scored L1 Fail
1.4 Scheduler
1.4.1 Ensure that the --profiling argument is set to false Scored L1 Pass
1.4.2 Ensure that the --bind-address argument is set to 127.0.0.1 Scored L1 Fail
2 etcd
2.1 Ensure that the --cert-file and --key-file arguments are set as appropriate Scored L1 Pass
2.2 Ensure that the --client-cert-auth argument is set to true Scored L1 Pass
2.3 Ensure that the --auto-tls argument is not set to true Scored L1 Pass
2.4 Ensure that the --peer-cert-file and --peer-key-file arguments are set as appropriate Scored L1 Pass
2.5 Ensure that the --peer-client-cert-auth argument is set to true Scored L1 Pass
2.6 Ensure that the --peer-auto-tls argument is not set to true Scored L1 Pass
2.7 Ensure that a unique Certificate Authority is used for etcd Not Scored L2 Pass
3 Control Plane Configuration
3.1 Authentication and Authorization
3.1.1 Client certificate authentication should not be used for users Not Scored L2 Pass
3.2 Logging
3.2.1 Ensure that a minimal audit policy is created Scored L1 Pass
3.2.2 Ensure that the audit policy covers key security concerns Not Scored L2 Pass
4 Worker Nodes
4.1 Worker Node Configuration Files
4.1.1 Ensure that the kubelet service file permissions are set to 644 or more restrictive Scored L1 Pass
4.1.2 Ensure that the kubelet service file ownership is set to root:root Scored L1 Pass
4.1.3 Ensure that the proxy kubeconfig file permissions are set to 644 or more restrictive Scored L1 Pass
4.1.4 Ensure that the proxy kubeconfig file ownership is set to root:root Scored L1 Pass
4.1.5 Ensure that the kubelet.conf file permissions are set to 644 or more restrictive Scored L1 Pass
4.1.6 Ensure that the kubelet.conf file ownership is set to root:root Scored L1 Pass
4.1.7 Ensure that the certificate authorities file permissions are set to 644 or more restrictive Scored L1 Pass
4.1.8 Ensure that the client certificate authorities file ownership is set to root:root Scored L1 Pass
4.1.9 Ensure that the kubelet configuration file has permissions set to 644 or more restrictive Scored L1 Pass
4.1.10 Ensure that the kubelet configuration file ownership is set to root:root Scored L1 Pass
4.2 Kubelet
4.2.1 Ensure that the --anonymous-auth argument is set to false Scored L1 Pass
4.2.2 Ensure that the --authorization-mode argument is not set to AlwaysAllow Scored L1 Pass
4.2.3 Ensure that the --client-ca-file argument is set as appropriate Scored L1 Pass
4.2.4 Ensure that the --read-only-port argument is set to 0 Scored L1 Pass
4.2.5 Ensure that the --streaming-connection-idle-timeout argument is not set to 0 Scored L1 Pass
4.2.6 Ensure that the --protect-kernel-defaults argument is set to true Scored L1 Pass
4.2.7 Ensure that the --make-iptables-util-chains argument is set to true Scored L1 Pass
4.2.8 Ensure that the --hostname-override argument is not set Not Scored L1 Pass
4.2.9 Ensure that the --event-qps argument is set to 0 or a level which ensures appropriate event capture Not Scored L2 Pass
4.2.10 Ensure that the --tls-cert-fileand --tls-private-key-file arguments are set as appropriate Scored L1 Equivalent Control
4.2.11 Ensure that the --rotate-certificates argument is not set to false Scored L1 Pass
4.2.12 Ensure that the RotateKubeletServerCertificate argument is set to true Scored L1 Fail
4.2.13 Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers Not Scored L1 Pass
5 Policies
5.1 RBAC and Service Accounts
5.1.1 Ensure that the cluster-admin role is only used where required Not Scored L1 Depends on Environment
5.1.2 Minimize access to secrets Not Scored L1 Depends on Environment
5.1.3 Minimize wildcard use in Roles and ClusterRoles Not Scored L1 Depends on Environment
5.1.4 Minimize access to create pods Not Scored L1 Depends on Environment
5.1.5 Ensure that default service accounts are not actively used Scored L1 Depends on Environment
5.1.6 Ensure that Service Account Tokens are only mounted where necessary Not Scored L1 Depends on Environment
5.2 Pod Security Policies
5.2.1 Minimize the admission of privileged containers Not Scored L1 Depends on Environment
5.2.2 Minimize the admission of containers wishing to share the host process ID namespace Scored L1 Depends on Environment
5.2.3 Minimize the admission of containers wishing to share the host IPC namespace Scored L1 Depends on Environment
5.2.4 Minimize the admission of containers wishing to share the host network namespace Scored L1 Depends on Environment
5.2.5 Minimize the admission of containers with allowPrivilegeEscalation Scored L1 Depends on Environment
5.2.6 Minimize the admission of root containers Not Scored L2 Depends on Environment
5.2.7 Minimize the admission of containers with the NET_RAW capability Not Scored L1 Depends on Environment
5.2.8 Minimize the admission of containers with added capabilities Not Scored L1 Depends on Environment
5.2.9 Minimize the admission of containers with capabilities assigned Not Scored L2 Depends on Environment
5.3 Network Policies and CNI
5.3.1 Ensure that the CNI in use supports Network Policies Not Scored L1 Pass
5.3.2 Ensure that all Namespaces have Network Policies defined Scored L2 Depends on Environment
5.4 Secrets Management
5.4.1 Prefer using secrets as files over secrets as environment variables Not Scored L1 Depends on Environment
5.4.2 Consider external secret storage Not Scored L2 Depends on Environment
5.5 Extensible Admission Control
5.5.1 Configure Image Provenance using ImagePolicyWebhook admission controller Not Scored L2 Depends on Environment
5.6 General Policies
5.6.1 Create administrative boundaries between resources using namespaces Not Scored L1 Depends on Environment
5.6.2 Ensure that the seccomp profile is set to docker/default in your pod definitions Not Scored L2 Depends on Environment
5.6.3 Apply Security Context to Your Pods and Containers Not Scored L2 Depends on Environment
5.6.4 The default namespace should not be used Scored 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 have been disabled in the OS.

Next steps

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