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 also supports encryption-at-rest for Kubernetes secrets. See etcd encryption for more details.

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.