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Linux Unified Key Setup (LUKS)

Contributors juliantap
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You can enable Linux Unified Key Setup (LUKS) to encrypt ONTAP SAN and ONTAP SAN ECONOMY volumes on Astra Trident. Astra Trident supports passphrase rotation and volume expansion for LUKS-encrypted volumes.

In Astra Trident, LUKS-encrypted volumes use the aes-xts-plain64 cypher and mode, as recommended by NIST.

Before you begin

  • Worker nodes must have cryptsetup 2.1 or higher (but lower than 3.0) installed. For more information, visit Gitlab: cryptsetup.

  • For performance reasons, we recommend that worker nodes support Advanced Encryption Standard New Instructions (AES-NI). To verify AES-NI support, run the following command:

    grep "aes" /proc/cpuinfo

    If nothing is returned, your processor does not support AES-NI. For more information on AES-NI, visit: Intel: Advanced Encryption Standard Instructions (AES-NI).

Enable LUKS encryption

You can enable per-volume, host-side encryption using Linux Unified Key Setup (LUKS) for ONTAP SAN and ONTAP SAN ECONOMY volumes.

Steps

  1. Define LUKS encryption attributes in the backend configuration. For more information on backend configuration options for ONTAP SAN, refer to ONTAP SAN configuration options.

    "storage": [
    {
        "labels":{"luks": "true"},
        "zone":"us_east_1a",
        "defaults": {
            "luksEncryption": "true"
        }
    },
    {
        "labels":{"luks": "false"},
        "zone":"us_east_1a",
        "defaults": {
            "luksEncryption": "false"
        }
    },
]

  2. Use parameters.selector to define the storage pools using LUKS encryption. For example:

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: luks
provisioner: netapp.io/trident
parameters:
  selector: "luks=true"
  csi.storage.k8s.io/node-stage-secret-name: luks-${pvc.name}
  csi.storage.k8s.io/node-stage-secret-namespace: ${pvc.namespace}

  3. Create a secret that contains the LUKS passphrase. For example:

    kubectl -n trident create -f luks-pvc1.yaml
apiVersion: v1
kind: Secret
metadata:
  name: luks-pvc1
stringData:
  luks-passphrase-name: A
  luks-passphrase: secretA

Limitations

LUKS-encrypted volumes cannot take advantage of ONTAP deduplication and compression.

Backend configuration for importing LUKS volumes

To import a LUKS volume, you must set luksEncryption to true on the backend. The luksEncryption option tells Astra Trident if the volume is LUKS-compliant (true) or not LUKS-compliant (false) as shown in the following example.

version: 1
storageDriverName: ontap-san
managementLIF: 10.0.0.1
dataLIF: 10.0.0.2
svm: trident_svm
username: admin
password: password
defaults:
  luksEncryption: 'true'
  spaceAllocation: 'false'
  snapshotPolicy: default
  snapshotReserve: '10'

Rotate a LUKS passphrase

You can rotate the LUKS passphrase and confirm rotation.

Warning Do not forget a passphrase until you have verified it is no longer referenced by any volume, snapshot, or secret. If a referenced passphrase is lost, you might be unable to mount the volume and the data will remain encrypted and inaccessible.
About this task

LUKS passphrase rotation occurs when a pod that mounts the volume is created after a new LUKS passphrase is specified. When a new pod is created, Astra Trident compares the LUKS passphrase on the volume to the active passphrase in the secret.

  • If the passphrase on the volume does not match the active passphrase in the secret, rotation occurs.

  • If the passphrase on the volume matches the active passphrase in the secret, the previous-luks-passphrase parameter is ignored.

Steps

  1. Add the node-publish-secret-name and node-publish-secret-namespace StorageClass parameters. For example:

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: csi-san
provisioner: csi.trident.netapp.io
parameters:
  trident.netapp.io/backendType: "ontap-san"
  csi.storage.k8s.io/node-stage-secret-name: luks
  csi.storage.k8s.io/node-stage-secret-namespace: ${pvc.namespace}
  csi.storage.k8s.io/node-publish-secret-name: luks
  csi.storage.k8s.io/node-publish-secret-namespace: ${pvc.namespace}

  2. Identify existing passphrases on the volume or snapshot.

    Volume
    tridentctl -d get volume luks-pvc1
GET http://127.0.0.1:8000/trident/v1/volume/<volumeID>

...luksPassphraseNames:["A"]
    Snapshot
    tridentctl -d get snapshot luks-pvc1
GET http://127.0.0.1:8000/trident/v1/volume/<volumeID>/<snapshotID>

...luksPassphraseNames:["A"]

  3. Update the LUKS secret for the volume to specify the new and previous passphrases. Ensure previous-luke-passphrase-name and previous-luks-passphrase match the previous passphrase.

    apiVersion: v1
kind: Secret
metadata:
  name: luks-pvc1
stringData:
  luks-passphrase-name: B
  luks-passphrase: secretB
  previous-luks-passphrase-name: A
  previous-luks-passphrase: secretA

  4. Create a new pod mounting the volume. This is required to initiate the rotation.

  5. Verify the the passphrase was rotated.

    Volume
    tridentctl -d get volume luks-pvc1
GET http://127.0.0.1:8000/trident/v1/volume/<volumeID>

...luksPassphraseNames:["B"]
    Snapshot
    tridentctl -d get snapshot luks-pvc1
GET http://127.0.0.1:8000/trident/v1/volume/<volumeID>/<snapshotID>

...luksPassphraseNames:["B"]
Results

The passphrase was rotated when only the new passphrase is returned on the volume and snapshot.

Note If two passphrases are returned, for example luksPassphraseNames: ["B", "A"], the rotation is incomplete. You can trigger a new pod to attempt to complete the rotation.

Enable volume expansion

You can enable volume expansion on a LUKS-encrypted volume.

Steps

  1. Enable the CSINodeExpandSecret feature gate (beta 1.25+). Refer to Kubernetes 1.25: Use Secrets for Node-Driven Expansion of CSI Volumes for details.

  2. Add the node-expand-secret-name and node-expand-secret-namespace StorageClass parameters. For example:

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: luks
provisioner: netapp.io/trident
parameters:
  selector: "luks=true"
  csi.storage.k8s.io/node-stage-secret-name: luks-${pvc.name}
  csi.storage.k8s.io/node-stage-secret-namespace: ${pvc.namespace}
  csi.storage.k8s.io/node-expand-secret-name: luks-${pvc.name}
  csi.storage.k8s.io/node-expand-secret-namespace: ${pvc.namespace}
allowVolumeExpansion: true
Results

When you initiate online storage expansion, the kubelet passes the appropriate credentials to the driver.