3 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.
5 To apply the hardening configuration, create a file (eg. `hardening.yaml`) and paste the content of the following code snippet into that.
7 ## Minimum Requirements
9 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).
11 **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.
20 authorization_modes: ['Node','RBAC']
22 #kube_apiserver_feature_gates: ['AppArmor=true']
23 kube_apiserver_request_timeout: 120s
24 kube_apiserver_service_account_lookup: true
26 # enable kubernetes audit
27 kubernetes_audit: true
28 audit_log_path: "/var/log/kube-apiserver-log.json"
30 audit_log_maxbackups: 10
31 audit_log_maxsize: 100
33 tls_min_version: VersionTLS12
35 - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
36 - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
37 - TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305
39 # enable encryption at rest
40 kube_encrypt_secret_data: true
41 kube_encryption_resources: [secrets]
42 kube_encryption_algorithm: "secretbox"
44 kube_apiserver_enable_admission_plugins: ['EventRateLimit,AlwaysPullImages,ServiceAccount,NamespaceLifecycle,NodeRestriction,LimitRanger,ResourceQuota,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,PodNodeSelector,PodSecurity']
45 kube_apiserver_admission_control_config_file: true
46 # EventRateLimit plugin configuration
47 kube_apiserver_admission_event_rate_limits:
59 ## kube-controller-manager
60 kube_controller_manager_bind_address: 127.0.0.1
61 kube_controller_terminated_pod_gc_threshold: 50
63 #kube_controller_feature_gates: ["RotateKubeletServerCertificate=true","AppArmor=true"]
64 kube_controller_feature_gates: ["RotateKubeletServerCertificate=true"]
67 kube_scheduler_bind_address: 127.0.0.1
68 kube_kubeadm_scheduler_extra_args:
71 #kube_scheduler_feature_gates: ["AppArmor=true"]
74 etcd_deployment_type: kubeadm
77 kubelet_authorization_mode_webhook: true
78 kubelet_authentication_token_webhook: true
79 kube_read_only_port: 0
80 kubelet_rotate_server_certificates: true
81 kubelet_protect_kernel_defaults: true
82 kubelet_event_record_qps: 1
83 kubelet_rotate_certificates: true
84 kubelet_streaming_connection_idle_timeout: "5m"
85 kubelet_make_iptables_util_chains: true
86 kubelet_feature_gates: ["RotateKubeletServerCertificate=true","SeccompDefault=true"]
87 kubelet_seccomp_default: true
89 # additional configurations
93 # create a default Pod Security Configuration and deny running of insecure pods
94 # kube_system namespace is exempted by default
95 kube_pod_security_use_default: true
96 kube_pod_security_default_enforce: restricted
99 Let's take a deep look to the resultant **kubernetes** configuration:
101 * 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`.
102 * 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: <https://kubernetes.io/docs/concepts/security/pod-security-admission/>). 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.
103 * 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).
104 * 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: <https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/>).
105 * 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.
107 Once you have the file properly filled, you can run the **Ansible** command to start the installation:
110 ansible-playbook -v cluster.yml \
112 -b --become-user=root \
113 --private-key ~/.ssh/id_ecdsa \
118 **N.B.** The `vars.yaml` contains our general cluster information (SANs, load balancer, dns, etc..) and `hardening.yaml` is the file described above.
120 Once completed the cluster deployment, don't forget to approve the generated certificates (check them with `kubectl get csr`, approve with `kubectl certificate approve <csr_name>`). 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)).