1 - Security best practices

Using security best practices with your EKS Anywhere deployments

If you discover a potential security issue in this project, we ask that you notify AWS/Amazon Security via our vulnerability reporting page . Please do not create a public GitHub issue for security problems.

This guide provides advice about best practices for EKS Anywhere specific security concerns. For a more complete treatment of Kubernetes security generally please refer to the official Kubernetes documentation on Securing a Cluster and the Amazon EKS Best Practices Guide for Security .

The Shared Responsibility Model and EKS-A

AWS Cloud Services follow the Shared Responsibility Model, where AWS is responsible for security “of” the cloud, while the customer is responsible for security “in” the cloud. However, EKS Anywhere is an open-source tool and the distribution of responsibility differs from that of a managed cloud service like EKS.

AWS Responsibilities

AWS is responsible for building and delivering a secure tool. This tool will provision an initially secure Kubernetes cluster.

AWS is responsible for vetting and securely sourcing the services and tools packaged with EKS Anywhere and the cluster it creates (such as CoreDNS, Cilium, Flux, CAPI, and govc).

The EKS Anywhere build and delivery infrastructure, or supply chain, is secured to the standard of any AWS service and AWS takes responsibility for the secure and reliable delivery of a quality product which provisions a secure and stable Kubernetes cluster. When the eksctl anywhere plugin is executed, EKS Anywhere components are automatically downloaded from AWS. eksctl will then perform checksum verification on the components to ensure their authenticity.

AWS is responsible for the secure development and testing of the EKS Anywhere controller and associated custom resource definitions.

AWS is responsible for the secure development and testing of the EKS Anywhere CLI, and ensuring it handles sensitive data and cluster resources securely.

End user responsibilities

The end user is responsible for the entire EKS Anywhere cluster after it has been provisioned. AWS provides a mechanism to upgrade the cluster in-place, but it is the responsibility of the end user to perform that upgrade using the provided tools. End users are responsible for operating their clusters in accordance with Kubernetes security best practices, and for the ongoing security of the cluster after it has been provisioned. This includes but is not limited to:

  • creation or modification of RBAC roles and bindings
  • creation or modification of namespaces
  • modification of the default container network interface plugin
  • configuration of network ingress and load balancing
  • use and configuration of container storage interfaces
  • the inclusion of add-ons and other services

End users are also responsible for:

  • The hardware and software which make up the infrastructure layer (such as vSphere, ESXi, physical servers, and physical network infrastructure).

  • The ongoing maintenance of the cluster nodes, including the underlying guest operating systems. Additionally, while EKS Anywhere provides a streamlined process for upgrading a cluster to a new Kubernetes version, it is the responsibility of the user to perform the upgrade as necessary.

  • Any applications which run “on” the cluster, including their secure operation, least privilege, and use of well-known and vetted container images.

EKS Anywhere Security Best Practices

This section captures EKS Anywhere specific security best practices. Please read this section carefully and follow any guidance to ensure the ongoing security and reliability of your EKS Anywhere cluster.

Critical Namespaces

EKS Anywhere creates and uses resources in several critical namespaces. All of the EKS Anywhere managed namespaces should be treated as sensitive and access should be limited to only the most trusted users and processes. Allowing additional access or modifying the existing RBAC resources could potentially allow a subject to access the namespace and the resources that it contains. This could lead to the exposure of secrets or the failure of your cluster due to modification of critical resources. Here are rules you should follow when dealing with critical namespaces:

  • Avoid creating Roles in these namespaces or providing users access to them with ClusterRoles . For more information about creating limited roles for day-to-day administration and development, please see the official introduction to Role Based Access Control (RBAC) .

  • Do not modify existing Roles in these namespaces, bind existing roles to additional subjects , or create new Roles in the namespace.

  • Do not modify existing ClusterRoles or bind them to additional subjects.

  • Avoid using the cluster-admin role, as it grants permissions over all namespaces.

  • No subjects except for the most trusted administrators should be permitted to perform ANY action in the critical namespaces.

The critical namespaces include:

  • eksa-system
  • capv-system
  • flux-system
  • capi-system
  • capi-webhook-system
  • capi-kubeadm-control-plane-system
  • capi-kubeadm-bootstrap-system
  • cert-manager
  • kube-system (as with any Kubernetes cluster, this namespace is critical to the functioning of your cluster and should be treated with the highest level of sensitivity.)

Secrets

EKS Anywhere stores sensitive information, like the vSphere credentials and GitHub Personal Access Token, in the cluster as native Kubernetes secrets . These secret objects are namespaced, for example in the eksa-system and flux-system namespace, and limiting access to the sensitive namespaces will ensure that these secrets will not be exposed. Additionally, limit access to the underlying node. Access to the node could allow access to the secret content.

EKS Anywhere does not currently support encryption-at-rest for Kubernetes secrets. EKS Anywhere support for Key Management Services (KMS) is planned.

The EKS Anywhere kubeconfig file

eksctl anywhere create cluster creates an EKS Anywhere-based Kubernetes cluster and outputs a kubeconfig file with administrative privileges to the $PWD/$CLUSTER_NAME directory.

By default, this kubeconfig file uses certificate-based authentication and contains the user certificate data for the administrative user.

The kubeconfig file grants administrative privileges over your cluster to the bearer and the certificate key should be treated as you would any other private key or administrative password.

The EKS Anywhere-generated kubeconfig file should only be used for interacting with the cluster via eksctl anywhere commands, such as upgrade, and for the most privileged administrative tasks. For more information about creating limited roles for day-to-day administration and development, please see the official introduction to Role Based Access Control (RBAC) .

GitOps

GitOps enabled EKS Anywhere clusters maintain a copy of their cluster configuration in the user provided Git repository. This configuration acts as the source of truth for the cluster. Changes made to this configuration will be reflected in the cluster configuration.

AWS recommends that you gate any changes to this repository with mandatory pull request reviews. Carefully review pull requests for changes which could impact the availability of the cluster (such as scaling nodes to 0 and deleting the cluster object) or contain secrets.

GitHub Personal Access Token

Treat the GitHub PAT used with EKS Anywhere as you would any highly privileged secret, as it could potentially be used to make changes to your cluster by modifying the contents of the cluster configuration file through the GitHub.com API.

  • Never commit the PAT to a Git repository
  • Never share the PAT via untrusted channels
  • Never grant non-administrative subjects access to the flux-system namespace where the PAT is stored as a native Kubernetes secret.

Executing EKS Anywhere

Ensure that you execute eksctl anywhere create cluster on a trusted workstation in order to protect the values of sensitive environment variables and the EKS Anywhere generated kubeconfig file.

SSH Access to Cluster Nodes and ETCD Nodes

EKS Anywhere provides the option to configure an ssh authorized key for access to underlying nodes in a cluster, via vsphereMachineConfig.Users.sshAuthorizedKeys. This grants the associated private key the ability to connect to the cluster via ssh as the user capv with sudo permissions. The associated private key should be treated as extremely sensitive, as sudo access to the cluster and ETCD nodes can permit access to secret object data and potentially confer arbitrary control over the cluster.

VMWare OVAs

Only download OVAs for cluster nodes from official sources, and do not allow untrusted users or processes to modify the templates used by EKS Anywhere for provisioning nodes.

Keeping Bottlerocket up to date

EKS Anywhere provides the most updated patch of operating systems with every release. It is recommended that your clusters are kept up to date with the latest EKS Anywhere release to ensure you get the latest security updates. Bottlerocket is an EKS Anywhere supported operating system that can be kept up to date without requiring a cluster update. The Bottlerocket Update Operator is a Kubernetes update operator that coordinates Bottlerocket updates on hosts in the cluster. Please follow the instructions here to install Bottlerocket update operator.

Baremetal Clusters

EKS Anywhere Baremetal clusters run directly on physical servers in a datacenter. Make sure that the physical infrastructure, including the network, is secure before running EKS Anywhere clusters.

Please follow industry best practices for securing your network and datacenter, including but not limited to the following

  • Only allow trusted devices on the network
  • Secure the network using a firewall
  • Never source hardware from an untrusted vendor
  • Inspect and verify the metal servers you are using for the clusters are the ones you intended to use
  • If possible, use a separate L2 network for EKS Anywhere baremetal clusters
  • Conduct thorough audits of access, users, logs and other exploitable venues periodically

Benchmark tests for cluster hardening

EKS Anywhere creates clusters with server hardening configurations out of the box, via the use of security flags and opinionated default templates. You can verify the security posture of your EKS Anywhere cluster by using a tool called kube-bench , that checks whether Kubernetes is deployed securely.

kube-bench runs checks documented in the CIS Benchmark for Kubernetes , such as, pod specification file permissions, disabling insecure arguments, and so on.

Refer to the EKS Anywhere CIS Self-Assessment Guide for more information on how to evaluate the security configurations of your EKS Anywhere cluster.

2 - Authenticate cluster with AWS IAM Authenticator

Configure AWS IAM Authenticator to authenticate user access to the cluster

AWS IAM Authenticator Support (optional)

EKS Anywhere supports configuring AWS IAM Authenticator as an authentication provider for clusters.

When you create a cluster with IAM Authenticator enabled, EKS Anywhere

  • Installs aws-iam-authenticator server as a DaemonSet on the workload cluster.
  • Configures the Kubernetes API Server to communicate with iam authenticator using a token authentication webhook .
  • Creates the necessary ConfigMaps based on user options.

Create IAM Authenticator enabled cluster

Generate your cluster configuration and add the necessary IAM Authenticator configuration. For a full spec reference check AWSIamConfig .

Create an EKS Anywhere cluster as follows:

CLUSTER_NAME=my-cluster-name
eksctl anywhere create cluster -f ${CLUSTER_NAME}.yaml

Example AWSIamConfig configuration

This example uses a region in the default aws partition and EKSConfigMap as backendMode. Also, the IAM ARNs are mapped to the kubernetes system:masters group.

apiVersion: anywhere.eks.amazonaws.com/v1alpha1
kind: Cluster
metadata:
   name: my-cluster-name
spec:
   ...
   # IAM Authenticator
   identityProviderRefs:
      - kind: AWSIamConfig
        name: aws-iam-auth-config
---
apiVersion: anywhere.eks.amazonaws.com/v1alpha1
kind: AWSIamConfig
metadata:
   name: aws-iam-auth-config
spec:
    awsRegion: us-west-1
    backendMode:
        - EKSConfigMap
    mapRoles:
        - roleARN: arn:aws:iam::XXXXXXXXXXXX:role/myRole
          username: myKubernetesUsername
          groups:
          - system:masters
    mapUsers:
        - userARN: arn:aws:iam::XXXXXXXXXXXX:user/myUser
          username: myKubernetesUsername
          groups:
          - system:masters
    partition: aws

Authenticating with IAM Authenticator

After your cluster is created you may now use the mapped IAM ARNs to authenticate to the cluster.

EKS Anywhere generates a KUBECONFIG file in your local directory that uses aws-iam-authenticator client to authenticate with the cluster. The file can be found at

${PWD}/${CLUSTER_NAME}/${CLUSTER_NAME}-aws.kubeconfig

Steps

  1. Ensure the IAM role/user ARN mapped in the cluster is configured on the local machine from which you are trying to access the cluster.

  2. Install the aws-iam-authenticator client binary on the local machine.

    • We recommend installing the binary referenced in the latest release manifest of the kubernetes version used when creating the cluster.
    • The below commands can be used to fetch the installation uri for clusters created with 1.27 kubernetes version and OS linux.
    CLUSTER_NAME=my-cluster-name
    KUBERNETES_VERSION=1.27
    
    export KUBECONFIG=${PWD}/${CLUSTER_NAME}/${CLUSTER_NAME}-eks-a-cluster.kubeconfig
    
    EKS_D_MANIFEST_URL=$(kubectl get bundles $CLUSTER_NAME -o jsonpath="{.spec.versionsBundles[?(@.kubeVersion==\"$KUBERNETES_VERSION\")].eksD.manifestUrl}")
    
    OS=linux
    curl -fsSL $EKS_D_MANIFEST_URL | yq e '.status.components[] | select(.name=="aws-iam-authenticator") | .assets[] | select(.os == '"\"$OS\""' and .type == "Archive") | .archive.uri' -
    
  3. Export the generated IAM Authenticator based KUBECONFIG file.

    export KUBECONFIG=${PWD}/${CLUSTER_NAME}/${CLUSTER_NAME}-aws.kubeconfig
    
  4. Run kubectl commands to check cluster access. Example,

    kubectl get pods -A
    

Modify IAM Authenticator mappings

EKS Anywhere supports modifying IAM ARNs that are mapped on the cluster. The mappings can be modified by either running the upgrade cluster command or using GitOps.

upgrade command

The mapRoles and mapUsers lists in AWSIamConfig can be modified when running the upgrade cluster command from EKS Anywhere.

As an example, let’s add another IAM user to the above example configuration.

apiVersion: anywhere.eks.amazonaws.com/v1alpha1
kind: AWSIamConfig
metadata:
   name: aws-iam-auth-config
spec:
    ...
    mapUsers:
        - userARN: arn:aws:iam::XXXXXXXXXXXX:user/myUser
          username: myKubernetesUsername
          groups:
          - system:masters
        - userARN: arn:aws:iam::XXXXXXXXXXXX:user/anotherUser
          username: anotherKubernetesUsername
    partition: aws

and then run the upgrade command

CLUSTER_NAME=my-cluster-name
eksctl anywhere upgrade cluster -f ${CLUSTER_NAME}.yaml

EKS Anywhere now updates the role mappings for IAM authenticator in the cluster and a new user gains access to the cluster.

GitOps

If the cluster created has GitOps configured, then the mapRoles and mapUsers list in AWSIamConfig can be modified by the GitOps controller. For GitOps configuration details refer to Manage Cluster with GitOps .

  1. Clone your git repo and modify the cluster specification. The default path for the cluster file is:
    clusters/$CLUSTER_NAME/eksa-system/eksa-cluster.yaml
    
  2. Modify the AWSIamConfig object and add to the mapRoles and mapUsers object lists.
  3. Commit the file to your git repository
    git add eksa-cluster.yaml
    git commit -m 'Adding IAM Authenticator access ARNs'
    git push origin main
    

EKS Anywhere GitOps Controller now updates the role mappings for IAM authenticator in the cluster and users gains access to the cluster.

3 - Certificate rotation

How to rotate certificates for etcd and control plane nodes

Certificates for external etcd and control plane nodes expire after 1 year in EKS Anywhere. EKS Anywhere automatically rotates these certificates when new machines are rolled out in the cluster. New machines are rolled out during cluster lifecycle operations such as upgrade. If you upgrade your cluster at least once a year, you do not have to manually rotate the cluster certificates.

This page shows the process for manually rotating certificates if you have not upgraded your cluster in 1 year.

The following table lists the cluster certificate files:

etcd node control plane node
apiserver-etcd-client apiserver-etcd-client
ca ca
etcdctl-etcd-client front-proxy-ca
peer sa
server etcd/ca.crt
apiserver-kubelet-client
apiserver
front-proxy-client

You can rotate certificates by following the steps given below. You cannot rotate the ca certificate because it is the root certificate. Note that the commands used for Bottlerocket nodes are different than those for Ubuntu and RHEL nodes.

External etcd nodes

If your cluster is using external etcd nodes, you need to renew the etcd node certificates first.

  1. SSH into each etcd node and run the following commands. Etcd automatically detects the new certificates and deprecates its old certificates.
# backup certs
cd /etc/etcd
sudo cp -r pki pki.bak
sudo rm pki/*
sudo cp pki.bak/ca.* pki

# run certificates join phase to regenerate the deleted certificates
sudo etcdadm join phase certificates http://eks-a-etcd-dumb-url
# you would be in the admin container when you ssh to the Bottlerocket machine
# open a root shell
sudo sheltie

# pull the image
IMAGE_ID=$(apiclient get | apiclient exec admin jq -r '.settings["host-containers"]["kubeadm-bootstrap"].source')
ctr image pull ${IMAGE_ID}

# backup certs
cd /var/lib/etcd
cp -r pki pki.bak
rm pki/*
cp pki.bak/ca.* pki

# recreate certificates
ctr run \
--mount type=bind,src=/var/lib/etcd/pki,dst=/etc/etcd/pki,options=rbind:rw \
--net-host \
--rm \
${IMAGE_ID} tmp-cert-renew \
/opt/bin/etcdadm join phase certificates http://eks-a-etcd-dumb-url --init-system kubelet
  1. Verify your etcd node is running correctly
sudo etcdctl --cacert=/etc/etcd/pki/ca.crt --cert=/etc/etcd/pki/etcdctl-etcd-client.crt --key=/etc/etcd/pki/etcdctl-etcd-client.key member list
ETCD_CONTAINER_ID=$(ctr -n k8s.io c ls | grep -w "etcd-io" | cut -d " " -f1)
ctr -n k8s.io t exec -t --exec-id etcd ${ETCD_CONTAINER_ID} etcdctl \
     --cacert=/var/lib/etcd/pki/ca.crt \
     --cert=/var/lib/etcd/pki/server.crt \
     --key=/var/lib/etcd/pki/server.key \
     member list
  1. Repeat the above steps for all etcd nodes.

  2. Save the api-server-etcd-client crt and key file as a Secret from one of the etcd nodes, so the key can be picked up by new control plane nodes. You will also need them when renewing the certificates on control plane nodes. See the Kubernetes documentation for details on editing Secrets.

kubectl edit secret ${cluster-name}-api-server-etcd-client -n eksa-system

Control plane nodes

When there are no external etcd nodes, you only need to rotate the certificates for control plane nodes, as etcd certificates are managed by kubeadm when there are no external etcd nodes.

  1. SSH into each control plane node and run the following commands.
sudo kubeadm certs renew all
# you would be in the admin container when you ssh to the Bottlerocket machine
# open root shell
sudo sheltie

# pull the image
IMAGE_ID=$(apiclient get | apiclient exec admin jq -r '.settings["host-containers"]["kubeadm-bootstrap"].source')
ctr image pull ${IMAGE_ID}

# renew certs
# you may see missing etcd certs error, which is expected if you have external etcd nodes
ctr run \
--mount type=bind,src=/var/lib/kubeadm,dst=/var/lib/kubeadm,options=rbind:rw \
--mount type=bind,src=/var/lib/kubeadm,dst=/etc/kubernetes,options=rbind:rw \
--rm \
${IMAGE_ID} tmp-cert-renew \
/opt/bin/kubeadm certs renew all
  1. Verify the certificates have been rotated.
sudo kubeadm certs check-expiration
# you may see missing etcd certs error, which is expected if you have external etcd nodes
ctr run \
--mount type=bind,src=/var/lib/kubeadm,dst=/var/lib/kubeadm,options=rbind:rw \
--mount type=bind,src=/var/lib/kubeadm,dst=/etc/kubernetes,options=rbind:rw \
--rm \
${IMAGE_ID} tmp-cert-renew \
/opt/bin/kubeadm certs check-expiration
  1. If you have external etcd nodes, manually replace the api-server-etcd-client.crt and api-server-etcd-client.key file in /etc/kubernetes/pki (or /var/lib/kubeadm/pki in Bottlerocket) folder with the files you saved from any etcd node.

  2. Restart static control plane pods.

    • For Ubuntu and RHEL: temporarily move all manifest files from /etc/kubernetes/manifests/ and wait for 20 seconds, then move the manifests back to this file location.

    • For Bottlerocket: re-enable the static pods:

    apiclient get | jq -r '.settings.kubernetes["static-pods"] | keys[]' | xargs -n 1 -I {} apiclient set settings.kubernetes.static-pods.{}.enabled=false 
    apiclient get | jq -r '.settings.kubernetes["static-pods"] | keys[]' | xargs -n 1 -I {} apiclient set settings.kubernetes.static-pods.{}.enabled=true`
    

    You can verify Pods restarting by running kubectl from your Admin machine.

  3. Repeat the above steps for all control plane nodes.

You can similarly use the above steps to rotate a single certificate instead of all certificates.

4 - CIS Self-Assessment Guide

CIS Benchmark Self-Assessment Guide for EKS Anywhere clusters

The CIS Benchmark self-assessment guide serves to help EKS Anywhere users evaluate the level of security of the hardened cluster configuration against Kubernetes benchmark controls from the Center for Information Security (CIS). This guide will walk through the various controls and provide updated example commands to audit compliance in EKS Anywhere clusters.

You can verify the security posture of your EKS Anywhere cluster by using a tool called kube-bench . The ideal way to run the benchmark tests on your EKS Anywhere cluster is to apply the Kube-bench Job YAMLs to the cluster. This runs the kube-bench tests on a Pod on the cluster, and the logs of the Pod provide the test results.

Kube-bench currently does not support unstacked etcd topology (which is the default for EKS Anywhere), so the following checks are skipped in the default kube-bench Job YAML. If you created your EKS Anywhere cluster with stacked etcd configuration, you can apply the stacked etcd Job YAML instead.

Check number Check description
1.1.7 Ensure that the etcd pod specification file permissions are set to 644 or more restrictive
1.1.8 Ensure that the etcd pod specification file ownership is set to root:root
1.1.11 Ensure that the etcd data directory permissions are set to 700 or more restrictive
1.1.12 Ensure that the etcd data directory ownership is set to etcd:etcd

The following tests are also skipped, because they are not applicable or enforce settings that might make the cluster unstable.

Check number Check description Reason for skipping
Controlplane node configuration
1.2.6 Ensure that the –kubelet-certificate-authority argument is set as appropriate When generating serving certificates, functionality could break in conjunction with hostname overrides which are required for certain cloud providers
1.2.16 Ensure that the admission control plugin PodSecurityPolicy is set Enabling Pod Security Policy can cause applications to unexpectedly fail
1.2.32 Ensure that the –encryption-provider-config argument is set as appropriate Enabling encryption changes how data can be recovered as data is encrypted
1.2.33 Ensure that encryption providers are appropriately configured Enabling encryption changes how data can be recovered as data is encrypted
Worker node configuration
4.2.6 Ensure that the –protect-kernel-defaults argument is set to true System level configurations are required before provisioning the cluster in order for this argument to be set to true
4.2.10 Ensure that the –tls-cert-file and –tls-private-key-file arguments are set as appropriate When generating serving certificates, functionality could break in conjunction with hostname overrides which are required for certain cloud providers