Decrypt Confidential Data that is Already Encrypted at Rest

All of the APIs in Kubernetes that let you write persistent API resource data support at-rest encryption. For example, you can enable at-rest encryption for Secrets. This at-rest encryption is additional to any system-level encryption for the etcd cluster or for the filesystem(s) on hosts where you are running the kube-apiserver.

This page shows how to switch from encryption of API data at rest, so that API data are stored unencrypted. You might want to do this to improve performance; usually, though, if it was a good idea to encrypt some data, it's also a good idea to leave them encrypted.

Before you begin

  • You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

  • This task assumes that you are running the Kubernetes API server as a static pod on each control plane node.

  • Your cluster's control plane must use etcd v3.x (major version 3, any minor version).

  • To encrypt a custom resource, your cluster must be running Kubernetes v1.26 or newer.

  • You should have some API data that are already encrypted.

To check the version, enter kubectl version.

Determine whether encryption at rest is already enabled

By default, the API server uses an identity provider that stores plain-text representations of resources. The default identity provider does not provide any confidentiality protection.

The kube-apiserver process accepts an argument --encryption-provider-config that specifies a path to a configuration file. The contents of that file, if you specify one, control how Kubernetes API data is encrypted in etcd. If it is not specified, you do not have encryption at rest enabled.

The format of that configuration file is YAML, representing a configuration API kind named EncryptionConfiguration. You can see an example configuration in Encryption at rest configuration.

If --encryption-provider-config is set, check which resources (such as secrets) are configured for encryption, and what provider is used. Make sure that the preferred provider for that resource type is not identity; you only set identity (no encryption) as default when you want to disable encryption at rest. Verify that the first-listed provider for a resource is something other than identity, which means that any new information written to resources of that type will be encrypted as configured. If you do see identity as the first-listed provider for any resource, this means that those resources are being written out to etcd without encryption.

Decrypt all data

This example shows how to stop encrypting the Secret API at rest. If you are encrypting other API kinds, adjust the steps to match.

Locate the encryption configuration file

First, find the API server configuration files. On each control plane node, static Pod manifest for the kube-apiserver specifies a command line argument, --encryption-provider-config. You are likely to find that this file is mounted into the static Pod using a hostPath volume mount. Once you locate the volume you can find the file on the node filesystem and inspect it.

Configure the API server to decrypt objects

To disable encryption at rest, place the identity provider as the first entry in your encryption configuration file.

For example, if your existing EncryptionConfiguration file reads:

---
apiVersion: apiserver.config.k8s.io/v1
kind: EncryptionConfiguration
resources:
  - resources:
      - secrets
    providers:
      - aescbc:
          keys:
            # Do not use this (invalid) example key for encryption
            - name: example
              secret: 2KfZgdiq2K0g2YrYpyDYs9mF2LPZhQ==

then change it to:

---
apiVersion: apiserver.config.k8s.io/v1
kind: EncryptionConfiguration
resources:
  - resources:
      - secrets
    providers:
      - identity: {} # add this line
      - aescbc:
          keys:
            - name: example
              secret: 2KfZgdiq2K0g2YrYpyDYs9mF2LPZhQ==

and restart the kube-apiserver Pod on this node.

Reconfigure other control plane hosts

If you have multiple API servers in your cluster, you should deploy the changes in turn to each API server.

Make sure that you use the same encryption configuration on each control plane host.

Force decryption

Then run the following command to force decryption of all Secrets:

# If you are decrypting a different kind of object, change "secrets" to match.
kubectl get secrets --all-namespaces -o json | kubectl replace -f -

Once you have replaced all existing encrypted resources with backing data that don't use encryption, you can remove the encryption settings from the kube-apiserver.

The command line options to remove are:

  • --encryption-provider-config
  • --encryption-provider-config-automatic-reload

Restart the kube-apiserver Pod again to apply the new configuration.

Reconfigure other control plane hosts

If you have multiple API servers in your cluster, you should again deploy the changes in turn to each API server.

Make sure that you use the same encryption configuration on each control plane host.

What's next

Last modified September 13, 2024 at 9:33 AM PST: Fix some hyperlinks in the markdown files (e6855623c7)