This document provides prescriptive guidance for hardening a production installation of Rancher v2.3.3. It outlines the configurations and controls required to address Kubernetes benchmark controls from the Center for Information Security (CIS).

This hardening guide describes how to secure the nodes in your cluster, and it is recommended to follow this guide before installing Kubernetes.

This hardening guide is intended to be used with specific versions of the CIS Kubernetes Benchmark, Kubernetes, and Rancher:

Click here to download a PDF version of this document

For more detail about evaluating a hardened cluster against the official CIS benchmark, refer to the CIS Benchmark Rancher Self-Assessment Guide v2.3.3.

Profile Definitions

The following profile definitions agree with the CIS benchmarks for Kubernetes.

A profile is a set of configurations that provide a certain amount of hardening. Generally, the more hardened an environment is, the more it affects performance.

Level 1

Items in this profile intend to:

• offer practical advice appropriate for the environment;
• deliver an obvious security benefit; and
• not alter the functionality or utility of the environment beyond an acceptable margin

Level 2

Items in this profile extend the “Level 1” profile and exhibit one or more of the following characteristics:

• are intended for use in environments or use cases where security is paramount
• act as a defense in depth measure
• may negatively impact the utility or performance of the technology

1.1 - Rancher RKE Kubernetes cluster host configuration

(See Appendix A. for full ubuntu cloud-config example)

1.1.1 - Configure default sysctl settings on all hosts

Profile Applicability

• Level 1

Description

Configure sysctl settings to match what the kubelet would set if allowed.

Rationale

We recommend that users launch the kubelet with the --protect-kernel-defaults option. The settings that the kubelet initially attempts to change can be set manually.

This supports the following control:

• 2.1.7 - Ensure that the --protect-kernel-defaults argument is set to true (Scored)

Audit

• Verify vm.overcommit_memory = 1

sysctl vm.overcommit_memory

• Verify vm.panic_on_oom = 0

sysctl vm.panic_on_oom

• Verify kernel.panic = 10

sysctl kernel.panic

• Verify kernel.panic_on_oops = 1

sysctl kernel.panic_on_oops

• Verify kernel.keys.root_maxkeys = 1000000

sysctl kernel.keys.root_maxkeys

• Verify kernel.keys.root_maxbytes = 25000000

sysctl kernel.keys.root_maxbytes

Remediation

• Set the following parameters in /etc/sysctl.d/90-kubelet.conf on all nodes:

vm.overcommit_memory=1
vm.panic_on_oom=0
kernel.panic=10
kernel.panic_on_oops=1
kernel.keys.root_maxkeys=1000000
kernel.keys.root_maxbytes=25000000

• Run sysctl -p /etc/sysctl.d/90-kubelet.conf to enable the settings.

1.4.11 Ensure that the etcd data directory permissions are set to 700 or more restrictive

Profile Applicability

• Level 1

Description

Ensure that the etcd data directory has permissions of 700 or more restrictive.

Rationale

etcd is a highly-available key-value store used by Kubernetes deployments for persistent storage of all of its REST API objects. This data directory should be protected from any unauthorized reads or writes. It should not be readable or writable by any group members or the world.

Audit

On the etcd server node, get the etcd data directory, passed as an argument --data-dir , from the below command:

ps -ef | grep etcd

Run the below command (based on the etcd data directory found above). For example,

stat -c %a /var/lib/etcd

Verify that the permissions are 700 or more restrictive.

Remediation

Follow the steps as documented in 1.4.12 remediation.

1.4.12 - Ensure that the etcd data directory ownership is set to etcd:etcd

Profile Applicability

• Level 1

Description

Ensure that the etcd data directory ownership is set to etcd:etcd.

Rationale

etcd is a highly-available key-value store used by Kubernetes deployments for persistent storage of all of its REST API objects. This data directory should be protected from any unauthorized reads or writes. It should be owned by etcd:etcd.

Audit

On a etcd server node, get the etcd data directory, passed as an argument --data-dir, from the below command:

ps -ef | grep etcd

Run the below command (based on the etcd data directory found above). For example,

stat -c %U:%G /var/lib/etcd

Verify that the ownership is set to etcd:etcd.

Remediation

• On the etcd server node(s) add the etcd user:

useradd -c "Etcd user" -d /var/lib/etcd etcd

Record the uid/gid:

id etcd

• Add the following to the RKE cluster.yml etcd section under services:

services:
  etcd:
    uid: <etcd user uid recorded previously>
    gid: <etcd user gid recorded previously>

2.1 - Rancher HA Kubernetes Cluster Configuration via RKE

(See Appendix B. for full RKE cluster.yml example)

2.1.1 - Configure kubelet options

Profile Applicability

• Level 1

Description

Ensure Kubelet options are configured to match CIS controls.

Rationale

To pass the following controls in the CIS benchmark, ensure the appropriate flags are passed to the Kubelet.

• 2.1.1 - Ensure that the --anonymous-auth argument is set to false (Scored)
• 2.1.2 - Ensure that the --authorization-mode argument is not set to AlwaysAllow (Scored)
• 2.1.6 - Ensure that the --streaming-connection-idle-timeout argument is not set to 0 (Scored)
• 2.1.7 - Ensure that the --protect-kernel-defaults argument is set to true (Scored)
• 2.1.8 - Ensure that the --make-iptables-util-chains argument is set to true (Scored)
• 2.1.10 - Ensure that the --event-qps argument is set to 0 (Scored)
• 2.1.13 - Ensure that the RotateKubeletServerCertificate argument is set to true (Scored)
• 2.1.14 - Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers (Not Scored)

Audit

Inspect the Kubelet containers on all hosts and verify that they are running with the following options:

• --streaming-connection-idle-timeout=<duration greater than 0>
• --authorization-mode=Webhook
• --protect-kernel-defaults=true
• --make-iptables-util-chains=true
• --event-qps=0
• --anonymous-auth=false
• --feature-gates="RotateKubeletServerCertificate=true"
• --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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"

Remediation

• Add the following to the RKE cluster.yml kubelet section under services:

services:
  kubelet:
    generate_serving_certificate: true
    extra_args:
      feature-gates: "RotateKubeletServerCertificate=true"
      protect-kernel-defaults: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"

Where <duration> is in a form like 1800s.

• Reconfigure the cluster:

rke up --config cluster.yml

2.1.2 - Configure kube-api options

Profile Applicability

• Level 1

Description

Ensure the RKE configuration is set to deploy the kube-api service with the options required for controls.

NOTE:

Enabling the AlwaysPullImages admission control plugin can cause degraded performance due to overhead of always pulling images. Enabling the DenyEscalatingExec admission control plugin will prevent the ‘Launch kubectl’ functionality in the UI from working.

Rationale

To pass the following controls for the kube-api server ensure RKE configuration passes the appropriate options.

• 1.1.1 - Ensure that the --anonymous-auth argument is set to false (Scored)
• 1.1.8 - Ensure that the --profiling argument is set to false (Scored)
• 1.1.11 - Ensure that the admission control plugin AlwaysPullImages is set (Scored)
• 1.1.12 - Ensure that the admission control plugin DenyEscalatingExec is set (Scored)
• 1.1.14 - Ensure that the admission control plugin NamespaceLifecycle is set (Scored)
• 1.1.15 - Ensure that the --audit-log-path argument is set as appropriate (Scored)
• 1.1.16 - Ensure that the --audit-log-maxage argument is set as appropriate (Scored)
• 1.1.17 - Ensure that the --audit-log-maxbackup argument is set as appropriate (Scored)
• 1.1.18 - Ensure that the --audit-log-maxsize argument is set as appropriate (Scored)
• 1.1.23 - Ensure that the --service-account-lookup argument is set to true (Scored)
• 1.1.24 - Ensure that the admission control plugin PodSecurityPolicy is set (Scored)
• 1.1.30 Ensure that the API Server only makes use of Strong Cryptographic Ciphers (Not Scored)
• 1.1.34 - Ensure that the --encryption-provider-config argument is set as appropriate (Scored)
• 1.1.35 - Ensure that the encryption provider is set to aescbc (Scored)
• 1.1.36 - Ensure that the admission control plugin EventRateLimit is set (Scored)
• 1.1.37 - Ensure that the AdvancedAuditing argument is not set to false (Scored)

Audit

• On nodes with the controlplane role inspect the kube-apiserver containers:

  docker inspect kube-apiserver

• Look for the following options in the command section of the output:

--anonymous-auth=false
--profiling=false
--service-account-lookup=true
--enable-admission-plugins=ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy
--encryption-provider-config=/etc/kubernetes/ssl/encryption.yaml
--admission-control-config-file=/etc/kubernetes/admission.yaml
--audit-log-path=/var/log/kube-audit/audit-log.json
--audit-log-maxage=30
--audit-log-maxbackup=10
--audit-log-maxsize=100
--audit-log-format=json
--audit-policy-file=/etc/kubernetes/audit-policy.yaml
--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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256

• In the volume section of the output ensure the bind mount is present:

/var/log/kube-audit:/var/log/kube-audit

Remediation

• In the RKE cluster.yml add the following directives to the kube-api section under services:

services:
  kube_api:
    always_pull_images: true
    pod_security_policy: true
    service_node_port_range: 30000-32767
    event_rate_limit:
      enabled: true
    audit_log:
      enabled: true
    secrets_encryption_config:
      enabled: true
    extra_args:
      anonymous-auth: "false"
      enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy"
      profiling: "false"
      service-account-lookup: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
    extra_binds:
      - "/opt/kubernetes:/opt/kubernetes"

For k8s 1.14 enable-admission-plugins should be

        enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,PodSecurityPolicy,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,Priority,EventRateLimit"

• Reconfigure the cluster:

rke up --config cluster.yml

NOTE:

Files that are placed in /opt/kubernetes need to be mounted in using the extra_binds functionality in RKE.

2.1.3 - Configure scheduler options

Profile Applicability

• Level 1

Description

Set the appropriate options for the Kubernetes scheduling service.

NOTE: Setting --address to 127.0.0.1 will prevent Rancher cluster monitoring from scraping this endpoint.

Rationale

To address the following controls on the CIS benchmark, the command line options should be set on the Kubernetes scheduler.

• 1.2.1 - Ensure that the --profiling argument is set to false (Scored)
• 1.2.2 - Ensure that the --address argument is set to 127.0.0.1 (Scored)

Audit

• On nodes with the controlplane role: inspect the kube-scheduler containers:

docker inspect kube-scheduler

• Verify the following options are set in the command section.

--profiling=false
--address=127.0.0.1

Remediation

• In the RKE cluster.yml file ensure the following options are set:

services:
  scheduler:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"

• Reconfigure the cluster:

rke up --config cluster.yml

2.1.4 - Configure controller options

Profile Applicability

• Level 1

Description

Set the appropriate arguments on the Kubernetes controller manager.

5*NOTE:** Setting --address to 127.0.0.1 will prevent Rancher cluster monitoring from scraping this endpoint.

Rationale

To address the following controls the options need to be passed to the Kubernetes controller manager.

• 1.3.1 - Ensure that the --terminated-pod-gc-threshold argument is set as appropriate (Scored)
• 1.3.2 - Ensure that the --profiling argument is set to false (Scored)
• 1.3.6 Ensure that the RotateKubeletServerCertificate argument is set to true (Scored)
• 1.3.7 - Ensure that the --address argument is set to 127.0.0.1 (Scored)

Audit

• On nodes with the controlplane role inspect the kube-controller-manager container:

docker inspect kube-controller-manager

• Verify the following options are set in the command section:

--terminated-pod-gc-threshold=1000
--profiling=false
--address=127.0.0.1
--feature-gates="RotateKubeletServerCertificate=true"

Remediation

• In the RKE cluster.yml file ensure the following options are set:

services:
  kube-controller:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"
      terminated-pod-gc-threshold: "1000"
      feature-gates: "RotateKubeletServerCertificate=true"

• Reconfigure the cluster:

rke up --config cluster.yml

2.1.5 - Configure addons and PSPs

Profile Applicability

• Level 1

Description

Configure a restrictive pod security policy (PSP) as the default and create role bindings for system level services to use the less restrictive default PSP.

Rationale

To address the following controls, a restrictive default PSP needs to be applied as the default. Role bindings need to be in place to allow system services to still function.

• 1.7.1 - Do not admit privileged containers (Not Scored)
• 1.7.2 - Do not admit containers wishing to share the host process ID namespace (Not Scored)
• 1.7.3 - Do not admit containers wishing to share the host IPC namespace (Not Scored)
• 1.7.4 - Do not admit containers wishing to share the host network namespace (Not Scored)
• 1.7.5 - Do not admit containers with allowPrivilegeEscalation (Not Scored)
• 1.7.6 - Do not admit root containers (Not Scored)
• 1.7.7 - Do not admit containers with dangerous capabilities (Not Scored)

Audit

• Verify that the cattle-system namespace exists:

kubectl get ns |grep cattle

• Verify that the roles exist:

kubectl get role default-psp-role -n ingress-nginx
kubectl get role default-psp-role -n cattle-system
kubectl get clusterrole restricted-clusterrole

• Verify the bindings are set correctly:

kubectl get rolebinding -n ingress-nginx default-psp-rolebinding
kubectl get rolebinding -n cattle-system default-psp-rolebinding
kubectl get clusterrolebinding restricted-clusterrolebinding

• Verify the restricted PSP is present.

kubectl get psp restricted-psp

Remediation

• In the RKE cluster.yml file ensure the following options are set:

addons: |
  apiVersion: rbac.authorization.k8s.io/v1
  kind: Role
  metadata:
    name: default-psp-role
    namespace: ingress-nginx
  rules:
  - apiGroups:
    - extensions
    resourceNames:
    - default-psp
    resources:
    - podsecuritypolicies
    verbs:
    - use
  ---
  apiVersion: rbac.authorization.k8s.io/v1
  kind: RoleBinding
  metadata:
    name: default-psp-rolebinding
    namespace: ingress-nginx
  roleRef:
    apiGroup: rbac.authorization.k8s.io
    kind: Role
    name: default-psp-role
  subjects:
  - apiGroup: rbac.authorization.k8s.io
    kind: Group
    name: system:serviceaccounts
  - apiGroup: rbac.authorization.k8s.io
    kind: Group
    name: system:authenticated
  ---
  apiVersion: v1
  kind: Namespace
  metadata:
    name: cattle-system
  ---
  apiVersion: rbac.authorization.k8s.io/v1
  kind: Role
  metadata:
    name: default-psp-role
    namespace: cattle-system
  rules:
  - apiGroups:
    - extensions
    resourceNames:
    - default-psp
    resources:
    - podsecuritypolicies
    verbs:
    - use
  ---
  apiVersion: rbac.authorization.k8s.io/v1
  kind: RoleBinding
  metadata:
    name: default-psp-rolebinding
    namespace: cattle-system
  roleRef:
    apiGroup: rbac.authorization.k8s.io
    kind: Role
    name: default-psp-role
  subjects:
  - apiGroup: rbac.authorization.k8s.io
    kind: Group
    name: system:serviceaccounts
  - apiGroup: rbac.authorization.k8s.io
    kind: Group
    name: system:authenticated
  ---
  apiVersion: policy/v1beta1
  kind: PodSecurityPolicy
  metadata:
    name: restricted-psp
  spec:
    requiredDropCapabilities:
    - NET_RAW
    privileged: false
    allowPrivilegeEscalation: false
    defaultAllowPrivilegeEscalation: false
    fsGroup:
      rule: RunAsAny
    runAsUser:
      rule: MustRunAsNonRoot
    seLinux:
      rule: RunAsAny
    supplementalGroups:
      rule: RunAsAny
    volumes:
    - emptyDir
    - secret
    - persistentVolumeClaim
    - downwardAPI
    - configMap
    - projected
  ---
  apiVersion: rbac.authorization.k8s.io/v1
  kind: ClusterRole
  metadata:
    name: restricted-clusterrole
  rules:
  - apiGroups:
    - extensions
    resourceNames:
    - restricted-psp
    resources:
    - podsecuritypolicies
    verbs:
    - use
  ---
  apiVersion: rbac.authorization.k8s.io/v1
  kind: ClusterRoleBinding
  metadata:
    name: restricted-clusterrolebinding
  roleRef:
    apiGroup: rbac.authorization.k8s.io
    kind: ClusterRole
    name: restricted-clusterrole
  subjects:
  - apiGroup: rbac.authorization.k8s.io
    kind: Group
    name: system:serviceaccounts
  - apiGroup: rbac.authorization.k8s.io
    kind: Group
    name: system:authenticated

• Reconfigure the cluster:

rke up --config cluster.yml

3.1 - Rancher Management Control Plane Installation

3.1.1 - Disable the local cluster option

Profile Applicability

• Level 2

Description

When deploying Rancher, disable the local cluster option on the Rancher Server.

NOTE: This requires Rancher v2.1.2 or above.

Rationale

Having access to the local cluster from the Rancher UI is convenient for troubleshooting and debugging; however, if the local cluster is enabled in the Rancher UI, a user has access to all elements of the system, including the Rancher management server itself. Disabling the local cluster is a defense in depth measure and removes the possible attack vector from the Rancher UI and API.

Audit

• Verify the Rancher deployment has the --add-local=false option set.

kubectl get deployment rancher -n cattle-system -o yaml |grep 'add-local'

• In the Rancher UI go to Clusters in the Global view and verify that no local cluster is present.

Remediation

• While upgrading or installing Rancher 2.3.3 or above, provide the following flag:

--set addLocal="false"

3.1.2 - Enable Rancher Audit logging

Profile Applicability

• Level 1

Description

Enable Rancher’s built-in audit logging capability.

Rationale

Tracking down what actions were performed by users in Rancher can provide insight during post mortems, and if monitored proactively can be used to quickly detect malicious actions.

Audit

• Verify that the audit log parameters were passed into the Rancher deployment.

kubectl get deployment rancher -n cattle-system -o yaml | grep auditLog

• Verify that the log is going to the appropriate destination, as set by auditLog.destination

  • sidecar:

  1. List pods:

     kubectl get pods -n cattle-system

  2. Tail logs:

     kubectl logs <pod> -n cattle-system -c rancher-audit-log

  • hostPath
  1. On the worker nodes running the Rancher pods, verify that the log files are being written to the destination indicated in auditlog.hostPath.

Remediation

Upgrade the Rancher server installation using Helm, and configure the audit log settings. The instructions for doing so can be found in the reference section below.

Reference

• https://rancher.com/docs/rancher/v2.x/en/installation/resources/chart-options/#advanced-options

3.2 - Rancher Management Control Plane Authentication

3.2.1 - Change the local admin password from the default value

Profile Applicability

• Level 1

Description

The local admin password should be changed from the default.

Rationale

The default admin password is common across all Rancher installations and should be changed immediately upon startup.

Audit

Attempt to login into the UI with the following credentials: - Username: admin - Password: admin

The login attempt must not succeed.

Remediation

Change the password from admin to a password that meets the recommended password standards for your organization.

3.2.2 - Configure an Identity Provider for Authentication

Profile Applicability

• Level 1

Description

When running Rancher in a production environment, configure an identity provider for authentication.

Rationale

Rancher supports several authentication backends that are common in enterprises. It is recommended to tie Rancher into an external authentication system to simplify user and group access in the Rancher cluster. Doing so assures that access control follows the organization’s change management process for user accounts.

Audit

• In the Rancher UI, select Global
• Select Security
• Select Authentication
• Ensure the authentication provider for your environment is active and configured correctly

Remediation

Configure the appropriate authentication provider for your Rancher installation according to the documentation found at the link in the reference section below.

Reference

• https://rancher.com/docs/rancher/v2.x/en/admin-settings/authentication/

3.3 - Rancher Management Control Plane RBAC

3.3.1 - Ensure that administrator privileges are only granted to those who require them

Profile Applicability

• Level 1

Description

Restrict administrator access to only those responsible for managing and operating the Rancher server.

Rationale

The admin privilege level gives the user the highest level of access to the Rancher server and all attached clusters. This privilege should only be granted to a few people who are responsible for the availability and support of Rancher and the clusters that it manages.

Audit

The following script uses the Rancher API to show users with administrator privileges:

#!/bin/bash
for i in $(curl -sk -u 'token-<id>:<secret>' https://<RANCHER_URL>/v3/users|jq -r .data[].links.globalRoleBindings); do
curl -sk -u 'token-<id>:<secret>' $i| jq '.data[] | "\(.userId) \(.globalRoleId)"'
done

The admin role should only be assigned to users that require administrative privileges. Any role that is not admin or user should be audited in the RBAC section of the UI to ensure that the privileges adhere to policies for global access.

The Rancher server permits customization of the default global permissions. We recommend that auditors also review the policies of any custom global roles.

Remediation

Remove the admin role from any user that does not require administrative privileges.

3.4 - Rancher Management Control Plane Configuration

3.4.1 - Ensure only approved node drivers are active

Profile Applicability

• Level 1

Description

Ensure that node drivers that are not needed or approved are not active in the Rancher console.

Rationale

Node drivers are used to provision compute nodes in various cloud providers and local IaaS infrastructure. For convenience, popular cloud providers are enabled by default. If the organization does not intend to use these or does not allow users to provision resources in certain providers, the drivers should be disabled. This will prevent users from using Rancher resources to provision the nodes.

Audit

• In the Rancher UI select Global
• Select Node Drivers
• Review the list of node drivers that are in an Active state.

Remediation

If a disallowed node driver is active, visit the Node Drivers page under Global and disable it.

4.1 - Rancher Kubernetes Custom Cluster Configuration via RKE

(See Appendix C. for full RKE template example)

4.1.1 - Configure kubelet options

Profile Applicability

• Level 1

Description

Ensure Kubelet options are configured to match CIS controls.

Rationale

To pass the following controls in the CIS benchmark, ensure the appropriate flags are passed to the Kubelet.

• 2.1.1 - Ensure that the --anonymous-auth argument is set to false (Scored)
• 2.1.2 - Ensure that the --authorization-mode argument is not set to AlwaysAllow (Scored)
• 2.1.6 - Ensure that the --streaming-connection-idle-timeout argument is not set to 0 (Scored)
• 2.1.7 - Ensure that the --protect-kernel-defaults argument is set to true (Scored)
• 2.1.8 - Ensure that the --make-iptables-util-chains argument is set to true (Scored)
• 2.1.10 - Ensure that the --event-qps argument is set to 0 (Scored)
• 2.1.13 - Ensure that the RotateKubeletServerCertificate argument is set to true (Scored)
• 2.1.14 - Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers (Not Scored)

Audit

Inspect the Kubelet containers on all hosts and verify that they are running with the following options:

• --streaming-connection-idle-timeout=<duration greater than 0>
• --authorization-mode=Webhook
• --protect-kernel-defaults=true
• --make-iptables-util-chains=true
• --event-qps=0
• --anonymous-auth=false
• --feature-gates="RotateKubeletServerCertificate=true"
• --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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"

Remediation

• Add the following to the RKE cluster.yml kubelet section under services:

services:
  kubelet:
    generate_serving_certificate: true
    extra_args:
      feature-gates: "RotateKubeletServerCertificate=true"
      protect-kernel-defaults: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"

Where <duration> is in a form like 1800s.

• Reconfigure the cluster:

rke up --config cluster.yml

4.1.2 - Configure kube-api options

Profile Applicability

• Level 1

Description

Ensure the RKE configuration is set to deploy the kube-api service with the options required for controls.

NOTE:

Enabling the AlwaysPullImages admission control plugin can cause degraded performance due to overhead of always pulling images. Enabling the DenyEscalatingExec admission control plugin will prevent the ‘Launch kubectl’ functionality in the UI from working.

Rationale

To pass the following controls for the kube-api server ensure RKE configuration passes the appropriate options.

• 1.1.1 - Ensure that the --anonymous-auth argument is set to false (Scored)
• 1.1.8 - Ensure that the --profiling argument is set to false (Scored)
• 1.1.11 - Ensure that the admission control plugin AlwaysPullImages is set (Scored)
• 1.1.12 - Ensure that the admission control plugin DenyEscalatingExec is set (Scored)
• 1.1.14 - Ensure that the admission control plugin NamespaceLifecycle is set (Scored)
• 1.1.15 - Ensure that the --audit-log-path argument is set as appropriate (Scored)
• 1.1.16 - Ensure that the --audit-log-maxage argument is set as appropriate (Scored)
• 1.1.17 - Ensure that the --audit-log-maxbackup argument is set as appropriate (Scored)
• 1.1.18 - Ensure that the --audit-log-maxsize argument is set as appropriate (Scored)
• 1.1.23 - Ensure that the --service-account-lookup argument is set to true (Scored)
• 1.1.24 - Ensure that the admission control plugin PodSecurityPolicy is set (Scored)
• 1.1.30 Ensure that the API Server only makes use of Strong Cryptographic Ciphers (Not Scored)
• 1.1.34 - Ensure that the --encryption-provider-config argument is set as appropriate (Scored)
• 1.1.35 - Ensure that the encryption provider is set to aescbc (Scored)
• 1.1.36 - Ensure that the admission control plugin EventRateLimit is set (Scored)
• 1.1.37 - Ensure that the AdvancedAuditing argument is not set to false (Scored)

Audit

• On nodes with the controlplane role inspect the kube-apiserver containers:

  docker inspect kube-apiserver

• Look for the following options in the command section of the output:

--anonymous-auth=false
--profiling=false
--service-account-lookup=true
--enable-admission-plugins=ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy
--encryption-provider-config=/etc/kubernetes/ssl/encryption.yaml
--admission-control-config-file=/etc/kubernetes/admission.yaml
--audit-log-path=/var/log/kube-audit/audit-log.json
--audit-log-maxage=30
--audit-log-maxbackup=10
--audit-log-maxsize=100
--audit-log-format=json
--audit-policy-file=/etc/kubernetes/audit-policy.yaml
--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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256

• In the volume section of the output ensure the bind mount is present:

/var/log/kube-audit:/var/log/kube-audit

Remediation

• In the RKE cluster.yml add the following directives to the kube-api section under services:

services:
  kube_api:
    always_pull_images: true
    pod_security_policy: true
    service_node_port_range: 30000-32767
    event_rate_limit:
      enabled: true
    audit_log:
      enabled: true
    secrets_encryption_config:
      enabled: true
    extra_args:
      anonymous-auth: "false"
      enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy"
      profiling: "false"
      service-account-lookup: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
    extra_binds:
      - "/opt/kubernetes:/opt/kubernetes"

For k8s 1.14 enable-admission-plugins should be

        enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,PodSecurityPolicy,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,Priority,EventRateLimit"

• Reconfigure the cluster:

rke up --config cluster.yml

NOTE:

Files that are placed in /opt/kubernetes need to be mounted in using the extra_binds functionality in RKE.

4.1.3 - Configure scheduler options

Profile Applicability

• Level 1

Description

Set the appropriate options for the Kubernetes scheduling service.

NOTE: Setting --address to 127.0.0.1 will prevent Rancher cluster monitoring from scraping this endpoint.

Rationale

To address the following controls on the CIS benchmark, the command line options should be set on the Kubernetes scheduler.

• 1.2.1 - Ensure that the --profiling argument is set to false (Scored)
• 1.2.2 - Ensure that the --address argument is set to 127.0.0.1 (Scored)

Audit

• On nodes with the controlplane role: inspect the kube-scheduler containers:

docker inspect kube-scheduler

• Verify the following options are set in the command section.

--profiling=false
--address=127.0.0.1

Remediation

• In the RKE cluster.yml file ensure the following options are set:

services:
  scheduler:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"

• Reconfigure the cluster:

rke up --config cluster.yml

4.1.4 - Configure controller options

Profile Applicability

• Level 1

Description

Set the appropriate arguments on the Kubernetes controller manager.

5*NOTE:** Setting --address to 127.0.0.1 will prevent Rancher cluster monitoring from scraping this endpoint.

Rationale

To address the following controls the options need to be passed to the Kubernetes controller manager.

• 1.3.1 - Ensure that the --terminated-pod-gc-threshold argument is set as appropriate (Scored)
• 1.3.2 - Ensure that the --profiling argument is set to false (Scored)
• 1.3.6 Ensure that the RotateKubeletServerCertificate argument is set to true (Scored)
• 1.3.7 - Ensure that the --address argument is set to 127.0.0.1 (Scored)

Audit

• On nodes with the controlplane role inspect the kube-controller-manager container:

docker inspect kube-controller-manager

• Verify the following options are set in the command section:

--terminated-pod-gc-threshold=1000
--profiling=false
--address=127.0.0.1
--feature-gates="RotateKubeletServerCertificate=true"

Remediation

• In the RKE cluster.yml file ensure the following options are set:

services:
  kube-controller:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"
      terminated-pod-gc-threshold: "1000"
      feature-gates: "RotateKubeletServerCertificate=true"

• Reconfigure the cluster:

rke up --config cluster.yml

4.1.5 - Check PSPs

Profile Applicability

• Level 1

Description

Configure a restrictive pod security policy (PSP) as the default and create role bindings for system level services to use the less restrictive default PSP.

Rationale

To address the following controls, a restrictive default PSP needs to be applied as the default. Role bindings need to be in place to allow system services to still function.

• 1.7.1 - Do not admit privileged containers (Not Scored)
• 1.7.2 - Do not admit containers wishing to share the host process ID namespace (Not Scored)
• 1.7.3 - Do not admit containers wishing to share the host IPC namespace (Not Scored)
• 1.7.4 - Do not admit containers wishing to share the host network namespace (Not Scored)
• 1.7.5 - Do not admit containers with allowPrivilegeEscalation (Not Scored)
• 1.7.6 - Do not admit root containers (Not Scored)
• 1.7.7 - Do not admit containers with dangerous capabilities (Not Scored)

Audit

• Verify that the cattle-system namespace exists:

kubectl get ns |grep cattle

• Verify that the roles exist:

kubectl get role default-psp-role -n ingress-nginx
kubectl get role default-psp-role -n cattle-system
kubectl get clusterrole restricted-clusterrole

• Verify the bindings are set correctly:

kubectl get rolebinding -n ingress-nginx default-psp-rolebinding
kubectl get rolebinding -n cattle-system default-psp-rolebinding

• Verify the restricted PSP is present.

kubectl get psp restricted-psp

Appendix A - Complete ubuntu cloud-config Example

cloud-config file to automate hardening manual steps on nodes deployment.

#cloud-config
bootcmd:
- apt-get update
- apt-get install -y apt-transport-https
apt:
  sources:
    docker:
      source: "deb [arch=amd64] https://download.docker.com/linux/ubuntu $RELEASE stable"
      keyid: 0EBFCD88
packages:
- [docker-ce, '5:19.03.5~3-0~ubuntu-bionic']
- jq
write_files:
# 1.1.1 - Configure default sysctl settings on all hosts
- path: /etc/sysctl.d/90-kubelet.conf
  owner: root:root
  permissions: '0644'
  content: |
    vm.overcommit_memory=1
    vm.panic_on_oom=0
    kernel.panic=10
    kernel.panic_on_oops=1
    kernel.keys.root_maxkeys=1000000
    kernel.keys.root_maxbytes=25000000
# 1.4.12 etcd user
groups:
  - etcd
users:
  - default
  - name: etcd
    gecos: Etcd user
    primary_group: etcd
    homedir: /var/lib/etcd
# 1.4.11 etcd data dir
runcmd:
  - chmod 0700 /var/lib/etcd
  - usermod -G docker -a ubuntu
  - sysctl -p /etc/sysctl.d/90-kubelet.conf

Appendix B - Complete RKE cluster.yml Example

Before apply, replace rancher_kubernetes_engine_config.services.etcd.gid and rancher_kubernetes_engine_config.services.etcd.uid with the proper etcd group and user ids that were created on etcd nodes.

RKE yaml for k8s 1.14

nodes:
- address: 18.191.190.205
  internal_address: 172.31.24.213
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
- address: 18.191.190.203
  internal_address: 172.31.24.203
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
- address: 18.191.190.10
  internal_address: 172.31.24.244
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
addon_job_timeout: 30
authentication:
  strategy: x509
authorization: {}
bastion_host:
  ssh_agent_auth: false
cloud_provider: {}
ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
ingress:
  provider: nginx
kubernetes_version: v1.14.9-rancher1-1
monitoring:
  provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
network:
  options:
    flannel_backend_type: vxlan
  plugin: canal
restore:
  restore: false
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
services:
  etcd:
    backup_config:
      enabled: true
      interval_hours: 12
      retention: 6
      safe_timestamp: false
    creation: 12h
    extra_args:
      election-timeout: '5000'
      heartbeat-interval: '500'
    gid: 1000
    retention: 72h
    snapshot: false
    uid: 1000
  kube-api:
    always_pull_images: true
    audit_log:
      enabled: true
    event_rate_limit:
      enabled: true
    extra_args:
      anonymous-auth: 'false'
      enable-admission-plugins: >-
        ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,PodSecurityPolicy,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,Priority,EventRateLimit
      profiling: 'false'
      service-account-lookup: 'true'
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256
    extra_binds:
      - '/opt/kubernetes:/opt/kubernetes'
    pod_security_policy: true
    secrets_encryption_config:
      enabled: true
    service_node_port_range: 30000-32767
  kube-controller:
    extra_args:
      address: 127.0.0.1
      feature-gates: RotateKubeletServerCertificate=true
      profiling: 'false'
      terminated-pod-gc-threshold: '1000'
  kubelet:
    extra_args:
      protect-kernel-defaults: 'true'
    fail_swap_on: false
    generate_serving_certificate: true
  kubeproxy: {}
  scheduler:
    extra_args:
      address: 127.0.0.1
      profiling: 'false'
ssh_agent_auth: false

RKE yaml for k8s 1.15

nodes:
- address: 18.191.190.205
  internal_address: 172.31.24.213
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
- address: 18.191.190.203
  internal_address: 172.31.24.203
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
- address: 18.191.190.10
  internal_address: 172.31.24.244
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
addon_job_timeout: 30
authentication:
  strategy: x509
ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
ingress:
  provider: nginx
kubernetes_version: v1.15.6-rancher1-2
monitoring:
  provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
network:
  options:
    flannel_backend_type: vxlan
  plugin: canal
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
services:
  etcd:
    backup_config:
      enabled: true
      interval_hours: 12
      retention: 6
      safe_timestamp: false
    creation: 12h
    extra_args:
      election-timeout: 5000
      heartbeat-interval: 500
    gid: 1000
    retention: 72h
    snapshot: false
    uid: 1000
  kube_api:
    always_pull_images: true
    pod_security_policy: true
    service_node_port_range: 30000-32767
    event_rate_limit:
      enabled: true
    audit_log:
      enabled: true
    secrets_encryption_config:
      enabled: true
    extra_args:
      anonymous-auth: "false"
      enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy"
      profiling: "false"
      service-account-lookup: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
    extra_binds:
      - "/opt/kubernetes:/opt/kubernetes"
  kubelet:
    generate_serving_certificate: true
    extra_args:
      feature-gates: "RotateKubeletServerCertificate=true"
      protect-kernel-defaults: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
  kube-controller:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"
      terminated-pod-gc-threshold: "1000"
      feature-gates: "RotateKubeletServerCertificate=true"
  scheduler:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"
ssh_agent_auth: false

RKE yaml for k8s 1.16

nodes:
- address: 18.191.190.205
  internal_address: 172.31.24.213
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
- address: 18.191.190.203
  internal_address: 172.31.24.203
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
- address: 18.191.190.10
  internal_address: 172.31.24.244
  user: ubuntu
  role: [ "controlplane", "etcd", "worker" ]
addon_job_timeout: 30
authentication:
  strategy: x509
ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
ingress:
  provider: nginx
kubernetes_version: v1.16.3-rancher1-1
monitoring:
  provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
network:
  options:
    flannel_backend_type: vxlan
  plugin: canal
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
services:
  etcd:
    backup_config:
      enabled: true
      interval_hours: 12
      retention: 6
      safe_timestamp: false
    creation: 12h
    extra_args:
      election-timeout: 5000
      heartbeat-interval: 500
    gid: 1000
    retention: 72h
    snapshot: false
    uid: 1000
  kube_api:
    always_pull_images: true
    pod_security_policy: true
    service_node_port_range: 30000-32767
    event_rate_limit:
      enabled: true
    audit_log:
      enabled: true
    secrets_encryption_config:
      enabled: true
    extra_args:
      anonymous-auth: "false"
      enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy"
      profiling: "false"
      service-account-lookup: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
    extra_binds:
      - "/opt/kubernetes:/opt/kubernetes"
  kubelet:
    generate_serving_certificate: true
    extra_args:
      feature-gates: "RotateKubeletServerCertificate=true"
      protect-kernel-defaults: "true"
      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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
  kube-controller:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"
      terminated-pod-gc-threshold: "1000"
      feature-gates: "RotateKubeletServerCertificate=true"
  scheduler:
    extra_args:
      profiling: "false"
      address: "127.0.0.1"
ssh_agent_auth: false

Appendix C - Complete RKE Template Example

Before apply, replace rancher_kubernetes_engine_config.services.etcd.gid and rancher_kubernetes_engine_config.services.etcd.uid with the proper etcd group and user ids that were created on etcd nodes.

RKE template for k8s 1.14

# 
# Cluster Config
# 
answers: {}
default_pod_security_policy_template_id: restricted
docker_root_dir: /var/lib/docker
enable_cluster_alerting: false
enable_cluster_monitoring: false
enable_network_policy: false
local_cluster_auth_endpoint:
  enabled: false
name: test-35378
# 
# Rancher Config
# 
rancher_kubernetes_engine_config:
  addon_job_timeout: 30
  authentication:
    strategy: x509
  authorization: {}
  bastion_host:
    ssh_agent_auth: false
  cloud_provider: {}
  ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
  ingress:
    provider: nginx
  kubernetes_version: v1.14.9-rancher1-1
  monitoring:
    provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
  network:
    options:
      flannel_backend_type: vxlan
    plugin: canal
  restore:
    restore: false
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
  services:
    etcd:
      backup_config:
        enabled: true
        interval_hours: 12
        retention: 6
        safe_timestamp: false
      creation: 12h
      extra_args:
        election-timeout: '5000'
        heartbeat-interval: '500'
      gid: 1000
      retention: 72h
      snapshot: false
      uid: 1000
    kube-api:
      always_pull_images: true
      audit_log:
        enabled: true
      event_rate_limit:
        enabled: true
      extra_args:
        anonymous-auth: 'false'
        enable-admission-plugins: >-
          ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,PodSecurityPolicy,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,Priority,EventRateLimit
        profiling: 'false'
        service-account-lookup: 'true'
        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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256
      extra_binds:
        - '/opt/kubernetes:/opt/kubernetes'
      pod_security_policy: true
      secrets_encryption_config:
        enabled: true
      service_node_port_range: 30000-32767
    kube-controller:
      extra_args:
        address: 127.0.0.1
        feature-gates: RotateKubeletServerCertificate=true
        profiling: 'false'
        terminated-pod-gc-threshold: '1000'
    kubelet:
      extra_args:
        protect-kernel-defaults: 'true'
      fail_swap_on: false
      generate_serving_certificate: true
    kubeproxy: {}
    scheduler:
      extra_args:
        address: 127.0.0.1
        profiling: 'false'
  ssh_agent_auth: false
windows_prefered_cluster: false

RKE template for k8s 1.15

# 
# Cluster Config
# 
default_pod_security_policy_template_id: restricted
docker_root_dir: /var/lib/docker
enable_cluster_alerting: false
enable_cluster_monitoring: false
enable_network_policy: false
local_cluster_auth_endpoint:
  enabled: true
# 
# Rancher Config
# 
rancher_kubernetes_engine_config:
  addon_job_timeout: 30
  authentication:
    strategy: x509
  ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
  ingress:
    provider: nginx
  kubernetes_version: v1.15.6-rancher1-2
  monitoring:
    provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
  network:
    options:
      flannel_backend_type: vxlan
    plugin: canal
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
  services:
    etcd:
      backup_config:
        enabled: true
        interval_hours: 12
        retention: 6
        safe_timestamp: false
      creation: 12h
      extra_args:
        election-timeout: 5000
        heartbeat-interval: 500
      gid: 1000
      retention: 72h
      snapshot: false
      uid: 1000
    kube_api:
      always_pull_images: true
      pod_security_policy: true
      service_node_port_range: 30000-32767
      event_rate_limit:
        enabled: true
      audit_log:
        enabled: true
      secrets_encryption_config:
        enabled: true
      extra_args:
        anonymous-auth: "false"
        enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy"
        profiling: "false"
        service-account-lookup: "true"
        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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
      extra_binds:
        - "/opt/kubernetes:/opt/kubernetes"
    kubelet:
      generate_serving_certificate: true
      extra_args:
        feature-gates: "RotateKubeletServerCertificate=true"
        protect-kernel-defaults: "true"
        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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
    kube-controller:
      extra_args:
        profiling: "false"
        address: "127.0.0.1"
        terminated-pod-gc-threshold: "1000"
        feature-gates: "RotateKubeletServerCertificate=true"
    scheduler:
      extra_args:
        profiling: "false"
        address: "127.0.0.1"
  ssh_agent_auth: false
windows_prefered_cluster: false

RKE template for k8s 1.16

# 
# Cluster Config
# 
default_pod_security_policy_template_id: restricted
docker_root_dir: /var/lib/docker
enable_cluster_alerting: false
enable_cluster_monitoring: false
enable_network_policy: false
local_cluster_auth_endpoint:
  enabled: true
# 
# Rancher Config
# 
rancher_kubernetes_engine_config:
  addon_job_timeout: 30
  authentication:
    strategy: x509
  ignore_docker_version: true
# 
# # Currently only nginx ingress provider is supported.
# # To disable ingress controller, set `provider: none`
# # To enable ingress on specific nodes, use the node_selector, eg:
#    provider: nginx
#    node_selector:
#      app: ingress
# 
  ingress:
    provider: nginx
  kubernetes_version: v1.16.3-rancher1-1
  monitoring:
    provider: metrics-server
# 
#   If you are using calico on AWS
# 
#    network:
#      plugin: calico
#      calico_network_provider:
#        cloud_provider: aws
# 
# # To specify flannel interface
# 
#    network:
#      plugin: flannel
#      flannel_network_provider:
#      iface: eth1
# 
# # To specify flannel interface for canal plugin
# 
#    network:
#      plugin: canal
#      canal_network_provider:
#        iface: eth1
# 
  network:
    options:
      flannel_backend_type: vxlan
    plugin: canal
# 
#    services:
#      kube-api:
#        service_cluster_ip_range: 10.43.0.0/16
#      kube-controller:
#        cluster_cidr: 10.42.0.0/16
#        service_cluster_ip_range: 10.43.0.0/16
#      kubelet:
#        cluster_domain: cluster.local
#        cluster_dns_server: 10.43.0.10
# 
  services:
    etcd:
      backup_config:
        enabled: true
        interval_hours: 12
        retention: 6
        safe_timestamp: false
      creation: 12h
      extra_args:
        election-timeout: 5000
        heartbeat-interval: 500
      gid: 1000
      retention: 72h
      snapshot: false
      uid: 1000
    kube_api:
      always_pull_images: true
      pod_security_policy: true
      service_node_port_range: 30000-32767
      event_rate_limit:
        enabled: true
      audit_log:
        enabled: true
      secrets_encryption_config:
        enabled: true
      extra_args:
        anonymous-auth: "false"
        enable-admission-plugins: "ServiceAccount,NamespaceLifecycle,LimitRanger,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota,DefaultTolerationSeconds,AlwaysPullImages,DenyEscalatingExec,NodeRestriction,EventRateLimit,PodSecurityPolicy"
        profiling: "false"
        service-account-lookup: "true"
        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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
      extra_binds:
        - "/opt/kubernetes:/opt/kubernetes"
    kubelet:
      generate_serving_certificate: true
      extra_args:
        feature-gates: "RotateKubeletServerCertificate=true"
        protect-kernel-defaults: "true"
        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,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256"
    kube-controller:
      extra_args:
        profiling: "false"
        address: "127.0.0.1"
        terminated-pod-gc-threshold: "1000"
        feature-gates: "RotateKubeletServerCertificate=true"
    scheduler:
      extra_args:
        profiling: "false"
        address: "127.0.0.1"
  ssh_agent_auth: false
windows_prefered_cluster: false