Longhorn supports volume encryption in both Filesystem and Block modes, providing protection against unauthorized access, data breaches, and compliance violations. Backups created from encrypted volumes are also encrypted.

Volume encryption is made possible by the Linux kernel module dm_crypt, the command-line utility cryptsetup, and Kubernetes Secrets. dm_crypt and cryptsetup handle the creation and management of encrypted devices, while Secrets (and related permissions) facilitate secure storage of encryption keys.

Requirements

To use encrypted volumes, ensure that the dm_crypt kernel module is loaded and that cryptsetup is installed on your worker nodes.

Setting up Kubernetes Secrets and StorageClasses

Longhorn uses Kubernetes Secrets for secure storage of encryption keys. Kubernetes allows usage of template parameters that are resolved during volume creation. To use a Secret with an encrypted volume, you must configure the Secret as a StorageClass parameter.

Template parameters allow you to use Secrets with individual volumes or with a collection of volumes. For more information about template parameters, see StorageClass Secrets in the Kubernetes CSI Developer Documentation.

In the following example, the encryption key is specified as string data in the CRYPTO_KEY_VALUE parameter of the Secret. Using string data eliminates the need for Base64 encoding before the Secret is submitted via kubectl create.

Besides CRYPTO_KEY_VALUE, parameters CRYPTO_KEY_CIPHER, CRYPTO_KEY_HASH, CRYPTO_KEY_SIZE, and CRYPTO_PBKDF provide the customization for volume encryption.

• CRYPTO_KEY_CIPHER: Sets the cipher specification algorithm string. The default value is aes-xts-plain64 for LUKS.
• CRYPTO_KEY_HASH: Specifies the passphrase hash for open. The default value is sha256.
• CRYPTO_KEY_SIZE: Sets the key size in bits and it must be a multiple of 8. The default value is 256.
• CRYPTO_PBKDF: Sets Password-Based Key Derivation Function (PBKDF) algorithm for LUKS keyslot. The default value is argon2i.

For more information, see cryptsetup(8) in the Linux man pages.

• Example of a Secret:

  apiVersion: v1
  kind: Secret
  metadata:
    name: longhorn-crypto
    namespace: longhorn-system
  stringData:
    CRYPTO_KEY_VALUE: "Your encryption passphrase"
    CRYPTO_KEY_PROVIDER: "secret"
    CRYPTO_KEY_CIPHER: "aes-xts-plain64"
    CRYPTO_KEY_HASH: "sha256"
    CRYPTO_KEY_SIZE: "256"
    CRYPTO_PBKDF: "argon2i"
  

• Example of a StorageClass with a global Secret:

  kind: StorageClass
  apiVersion: storage.k8s.io/v1
  metadata:
    name: longhorn-crypto-global
  provisioner: driver.longhorn.io
  allowVolumeExpansion: true
  parameters:
    numberOfReplicas: "3"
    staleReplicaTimeout: "2880" # 48 hours in minutes
    fromBackup: ""
    encrypted: "true"
    # global secret that contains the encryption key that will be used for all volumes
    csi.storage.k8s.io/provisioner-secret-name: "longhorn-crypto"
    csi.storage.k8s.io/provisioner-secret-namespace: "longhorn-system"
    csi.storage.k8s.io/node-publish-secret-name: "longhorn-crypto"
    csi.storage.k8s.io/node-publish-secret-namespace: "longhorn-system"
    csi.storage.k8s.io/node-stage-secret-name: "longhorn-crypto"
    csi.storage.k8s.io/node-stage-secret-namespace: "longhorn-system"
    csi.storage.k8s.io/node-expand-secret-name: "longhorn-crypto"
    csi.storage.k8s.io/node-expand-secret-namespace: "longhorn-system"
  

• Example of a StorageClass with a volume-specific Secret:

  kind: StorageClass
  apiVersion: storage.k8s.io/v1
  metadata:
    name: longhorn-crypto-per-volume
  provisioner: driver.longhorn.io
  allowVolumeExpansion: true
  parameters:
    numberOfReplicas: "3"
    staleReplicaTimeout: "2880" # 48 hours in minutes
    fromBackup: ""
    encrypted: "true"
    # per volume secret which utilizes the `pvc.name` and `pvc.namespace` template parameters
    csi.storage.k8s.io/provisioner-secret-name: ${pvc.name}
    csi.storage.k8s.io/provisioner-secret-namespace: ${pvc.namespace}
    csi.storage.k8s.io/node-publish-secret-name: ${pvc.name}
    csi.storage.k8s.io/node-publish-secret-namespace: ${pvc.namespace}
    csi.storage.k8s.io/node-stage-secret-name: ${pvc.name}
    csi.storage.k8s.io/node-stage-secret-namespace: ${pvc.namespace}
    csi.storage.k8s.io/node-expand-secret-name: ${pvc.name}
    csi.storage.k8s.io/node-expand-secret-namespace: ${pvc.namespace}
  

Using an Encrypted Volume

To create an encrypted volume, you must create a PVC using a StorageClass that has been configured for encryption. The above StorageClass examples can be used as a starting point.

After creation of the PVC it will remain in Pending state till the associated secret has been created and can be retrieved A newly-created PVC remains in the Pending state until the associated Secret is created and can be retrieved by the csi external-provisioner sidecar. Afterwards, the regular volume creation process continues with encryption taking effect.

Filesystem Expansion

Longhorn supports both online and offline expansion for encrypted volumes.

StorageClass parameters are needed to enable online expansion:

• csi.storage.k8s.io/node-expand-secret-name
• csi.storage.k8s.io/node-expand-secret-namespace

History

• Encryption of volumes in Filesystem mode available starting v1.2.0 (#1859)

• Encryption of volumes in Block mode available starting v1.6.0 (#4883)