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KMS Envelope Encryption for EKS clusters

EKS supports using AWS KMS keys to provide envelope encryption of Kubernetes secrets stored in EKS. Implementing envelope encryption is considered a security best practice for applications that store sensitive data and is part of a defense in depth security strategy.

Creating a cluster with KMS encryption enabled

# kms-cluster.yaml
# A cluster with KMS encryption enabled
---
apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: kms-cluster
  region: us-west-2

managedNodeGroups:
- name: ng
# more config

secretsEncryption:
  # KMS key used for envelope encryption of Kubernetes secrets
  keyARN: arn:aws:kms:us-west-2:<account>:key/<key>

$ eksctl create cluster -f kms-cluster.yaml

Enabling KMS encryption on an existing cluster

To enable KMS encryption on a cluster that doesn't already have it enabled, run

$ eksctl utils enable-secrets-encryption -f kms-cluster.yaml

or without a config file:

$ eksctl utils enable-secrets-encryption --cluster=kms-cluster --key-arn=arn:aws:kms:us-west-2:<account>:key/<key> --region=<region>

In addition to enabling KMS encryption on the EKS cluster, eksctl also re-encrypts all existing Kubernetes secrets using the new KMS key by updating them with the annotation eksctl.io/kms-encryption-timestamp. This behaviour can be disabled by passing --encrypt-existing-secrets=false, as in:

$ eksctl utils enable-secrets-encryption --cluster=kms-cluster --key-arn=arn:aws:kms:us-west-2:<account>:key/<key> --encrypt-existing-secrets=false --region=<region>

If a cluster already has KMS encryption enabled, eksctl will proceed to re-encrypting all existing secrets.

Note

Once KMS encryption is enabled, it cannot be disabled or updated to use a different KMS key.

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