# Cluster Hardening If you want to improve the security on your cluster and make it compliant with the [CIS Benchmarks](https://learn.cisecurity.org/benchmarks), here you can find a configuration to harden your **kubernetes** installation. To apply the hardening configuration, create a file (eg. `hardening.yaml`) and paste the content of the following code snippet into that. ## Minimum Requirements The **kubernetes** version should be at least `v1.23.6` to have all the most recent security features (eg. the new `PodSecurity` admission plugin, etc). **N.B.** Some of these configurations have just been added to **kubespray**, so ensure that you have the latest version to make it works properly. Also, ensure that other configurations doesn't override these. `hardening.yaml`: ```yaml # Hardening --- ## kube-apiserver authorization_modes: ['Node','RBAC'] # AppArmor-based OS #kube_apiserver_feature_gates: ['AppArmor=true'] kube_apiserver_request_timeout: 120s kube_apiserver_service_account_lookup: true # enable kubernetes audit kubernetes_audit: true audit_log_path: "/var/log/kube-apiserver-log.json" audit_log_maxage: 30 audit_log_maxbackups: 10 audit_log_maxsize: 100 tls_min_version: VersionTLS12 tls_cipher_suites: - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 # enable encryption at rest kube_encrypt_secret_data: true kube_encryption_resources: [secrets] kube_encryption_algorithm: "secretbox" kube_apiserver_enable_admission_plugins: ['EventRateLimit,AlwaysPullImages,ServiceAccount,NamespaceLifecycle,NodeRestriction,LimitRanger,ResourceQuota,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,PodNodeSelector,PodSecurity'] kube_apiserver_admission_control_config_file: true # EventRateLimit plugin configuration kube_apiserver_admission_event_rate_limits: limit_1: type: Namespace qps: 50 burst: 100 cache_size: 2000 limit_2: type: User qps: 50 burst: 100 kube_profiling: false ## kube-controller-manager kube_controller_manager_bind_address: 127.0.0.1 kube_controller_terminated_pod_gc_threshold: 50 # AppArmor-based OS #kube_controller_feature_gates: ["RotateKubeletServerCertificate=true","AppArmor=true"] kube_controller_feature_gates: ["RotateKubeletServerCertificate=true"] ## kube-scheduler kube_scheduler_bind_address: 127.0.0.1 kube_kubeadm_scheduler_extra_args: profiling: false # AppArmor-based OS #kube_scheduler_feature_gates: ["AppArmor=true"] ## etcd etcd_deployment_type: kubeadm ## kubelet kubelet_authentication_token_webhook: true kube_read_only_port: 0 kubelet_rotate_server_certificates: true kubelet_protect_kernel_defaults: true kubelet_event_record_qps: 1 kubelet_rotate_certificates: true kubelet_streaming_connection_idle_timeout: "5m" kubelet_make_iptables_util_chains: true kubelet_feature_gates: ["RotateKubeletServerCertificate=true"] ``` Let's take a deep look to the resultant **kubernetes** configuration: * The `anonymous-auth` (on `kube-apiserver`) is set to `true` by default. This is fine, because it is considered safe if you enable `RBAC` for the `authorization-mode`. * The `enable-admission-plugins` has not the `PodSecurityPolicy` admission plugin. This because it is going to be definitely removed from **kubernetes** `v1.25`. For this reason we decided to set the newest `PodSecurity` (for more details, please take a look here: ). Then, we set the `EventRateLimit` plugin, providing additional configuration files (that are automatically created under the hood and mounted inside the `kube-apiserver` container) to make it work. * The `encryption-provider-config` provide encryption at rest. This means that the `kube-apiserver` encrypt data that is going to be stored before they reach `etcd`. So the data is completely unreadable from `etcd` (in case an attacker is able to exploit this). * The `rotateCertificates` in `KubeletConfiguration` is set to `true` along with `serverTLSBootstrap`. This could be used in alternative to `tlsCertFile` and `tlsPrivateKeyFile` parameters. Additionally it automatically generates certificates by itself, but you need to manually approve them or at least using an operator to do this (for more details, please take a look here: ). * If you are installing **kubernetes** in an AppArmor-based OS (eg. Debian/Ubuntu) you can enable the `AppArmor` feature gate uncommenting the lines with the comment `# AppArmor-based OS` on top. Once you have the file properly filled, you can run the **Ansible** command to start the installation: ```bash ansible-playbook -v cluster.yml \ -i inventory.ini \ -b --become-user=root \ --private-key ~/.ssh/id_ecdsa \ -e "@vars.yaml" \ -e "@hardening.yaml" ``` **N.B.** The `vars.yaml` contains our general cluster information (SANs, load balancer, dns, etc..) and `hardening.yaml` is the file described above. Once completed the cluster deployment, don't forget to approve the generated certificates (check them with `kubectl get csr`, approve with `kubectl certificate approve `). This action is necessary because the `secureTLSBootstrap` option and `RotateKubeletServerCertificate` feature gate for `kubelet` are enabled (CIS [4.2.11](https://www.tenable.com/audits/items/CIS_Kubernetes_v1.20_v1.0.0_Level_1_Worker.audit:05af3dfbca8e0c3fb3559c6c7de29191), [4.2.12](https://www.tenable.com/audits/items/CIS_Kubernetes_v1.20_v1.0.0_Level_1_Worker.audit:5351c76f8c5bff8f98c29a5200a35435)).