StorageOS supports encryption for data-at-rest and data-in-transit.

Data-in-transit is data as it is travelling between nodes. It is encrypted by default with mTLS. Data-at-rest is the data stored in your volumes as blob files. Encryption of these blob files is optional and can be enabled by adding a label to your volume definitions before they’re provisioned.

For information on how to enable encryption on your volumes, please see our Encryption Operations page.

How volumes are encrypted

Volumes are encrypted using AES-256 in the XTS-AES mode with 512-bit keys, as specified by IEEE Standard 1619-2007. There is a non-zero performance impact of using encrypted volumes. A 10-25% cost in read/write throughput can be expected from XTS-AES, dependent on workload. Thin provisioning still applies to encrypted volumes.

Encryption Key Generation

On PVC creation, if encryption is enabled, StorageOS will automatically generate up to two keys as Kubernetes secrets. Both keys are stored in the same namespace as the PVC.

Firstly, if it doesn’t already exist, a namespace key is generated. It is always named storageos-namespace-key and only one exists per namespace.

Secondly a volume key is created for each encrypted volume. It has a name in the format storageos-volume-key-<random-id>, with no connection to the name of the volume. The volume it is associated with can be determined by looking at the storageos.com/pvc label on the secret. The storageos.com/encryption-secret-name and storageos.com/encryption-secret-namespace annotations are added to the PVC by an admission controller to map the PVC back to its secret.

The encryption key is passed to StorageOS as part of the CSI volume creation request and is used to encrypt the volume.

Encryption Key Use

The volume specific secret is needed whenever a volume is attached to a node for use by a pod. When this happens, the StorageOS node container’s Service Account reads the secret and passes it to the StorageOS controlplane.

A volume missing its key or with a malformed key will be unable to attach.

The key is stored in memory by StorageOS only on the node that the volume is being used on. As a result, encryption and decryption are performed where the data is consumed, rather than where it is stored.

Because of this, the use of encrypted volumes is transparent to the user. There is a complete integration between Kubernetes applications and StorageOS encryption.

Key Management Best Practices

StorageOS saves encryption keys in Kubernetes Secrets. Backups are therefore imperative in case the Kubernetes Etcd is lost. StorageOS has no ability to decrypt a volume whose encryption keys have been lost.

Secrets in Kubernetes are not encrypted by default, they are stored in the Kubernetes Etcd in simple Base64 encoding. As StorageOS encryption keys are stored as Kubernetes Secrets, this means that anyone with access to a Kubernetes Etcd installation can read encryption keys and decrypt volumes, unless the cluster has an external secrets store.

For better security check Kubernetes secret encryption.

Secrets are not garbage-collected by StorageOS. To clean up completely upon deletion of a volume it is necessary to also delete that volume’s secret. There is no benefit to doing this, however.

Key Management with Kubernetes KMS provider

StorageOS encryption keys are stored within Etcd as Kubernetes secrets. Whilst the Etcd and kubernetes secrets can also be encrypted, many organisations choose to use an external KMS provider.

To address this from a Kubernetes limitations perspective and provide an agnostic solution, our encryption design allows the user to benefit from any Kubernetes KMS provider plugin to envelop the secrets into the KMS provider encryption scheme.

StorageOS allows customers to transparently integrate any supported KMS plugin with StorageOS encryption key management using the standard Kubernetes API and Kubernetes KMS provider framework. The below figure provides an overview of the process.

KMS Key Management

  1. The KMS plugin is deployed within the Kubernetes cluster.
  2. The KMS plugin is configured to act as a broker between the Kubernetes API server and the KMS server API endpoint.
  3. At volume creation, StorageOS will create a Kubernetes secret using Kubernetes API calls
  4. The KMS plugin will handle the Kubernetes API Secret creation call and interface to the KMS server instance.
  5. The KMS server will return the secret using its encryption envelop scheme.
  6. The KMS plugin will store the encrypted secret within the Kubernetes Etcd.

Contact the StorageOS sales team for more information about the dedicated StorageOS Vault KMS plugin integration offering.