Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

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Harden Kubernetes RBAC in Amazon EKS

Kubernetes role-based access control (RBAC) controls what actions identities can perform inside a cluster. Many cluster components, including CSI drivers and other add-ons installed as DaemonSets, require broad permissions to function. Reviewing and scoping these permissions reduces the potential scope of any unintended access.

This topic describes the permission considerations for common cluster components and the recommended controls.

DaemonSet service account permissions

DaemonSet Pods run on every node in the cluster, so their service account tokens and the RBAC permissions those tokens grant are present on every node.

An unauthorized process on a node may be able to access the service account tokens of other Pods running on the same node, including DaemonSet Pods. The RBAC permissions granted to DaemonSet service accounts are the same on every node in the cluster.

Components commonly deployed as DaemonSets include:

If a DaemonSet Pod has Amazon IAM credentials through EKS Pod Identity or IAM Roles for Service Accounts (IRSA), a process that gains access outside its container on the same node may also access those credentials. This extends the scope of impact beyond Kubernetes RBAC to any Amazon API permissions granted to a DaemonSet’s IAM role.

CSI driver RBAC scope

CSI drivers commonly hold broad RBAC grants because they interact with nodes, persistent volumes, and storage APIs.

Node object permissions

CSI drivers may require RBAC permissions to modify Node objects to support features such as taint removal or other node management tasks. Due to Kubernetes RBAC limitations, these permissions apply to all Node objects in the cluster, not only the local node the driver is running on.

For the EBS CSI driver, the Helm chart provides a parameter (node.serviceAccount.disableMutation) that removes the node modification permission from the ebs-csi-node service account. Enabling this disables the taint removal feature.

Service account token exposure

CSI driver Pods may use projected service account tokens for authentication. On a node where an unauthorized process has gained access outside its container, those tokens may be accessible through the container filesystem or the kubelet API. If the service account is also associated with an IAM role through EKS Pod Identity or IRSA, an exposed token can be used to obtain Amazon IAM credentials.

Recommended controls

Scope RBAC to least privilege

Enforce Pod security standards

Apply the Kubernetes Pod Security Standards using the built-in Pod Security Admission controller or a policy engine. At minimum, enforce the baseline profile cluster-wide and the restricted profile for workload namespaces. This limits the ability to create privileged containers outside of system namespaces.

Use network policies

Apply network policies to restrict egress from CSI driver and DaemonSet Pods to only the endpoints they need (for example, the Kubernetes API server and Amazon service endpoints). This reduces the scope of actions possible.

Monitor RBAC activity

Enable Kubernetes audit logging and monitor for unexpected API calls from DaemonSet service accounts. Look for:

For more information, see Send control plane logs to CloudWatch Logs.