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130 lines
4.3 KiB
Markdown
130 lines
4.3 KiB
Markdown
# Encrypted Persistent Volume Claims
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## Proposal
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Subject of this proposal is to add support for encryption of RBD volumes in
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Ceph-CSI.
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Some but not all the benefits of this approach:
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* guarantee encryption in transit to rbd without using messenger v2
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* extra security layer to application with special regulatory needs
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* at rest encryption can be disabled to selectively allow encryption only where
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required
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## Document Terminology
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* volume encryption: encryption of a volume attached by rbd
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* encryption at rest: encryption of physical disk done by ceph
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* LUKS: Linux Unified Key Setup: stores all of the needed setup information for
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dm-crypt on the disk
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* dm-crypt: linux kernel device-mapper crypto target
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* cryptsetup: the command line tool to interface with dm-crypt
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## Proposed Solution
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The proposed solution in this document, is to address the volume encryption
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requirement by using dm-crypt module through cryptsetup cli interface.
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### Implementation Summary
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* Encryption is implemented using cryptsetup with LUKS extension.
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A good introduction to LUKS and dm-crypt in general can be found
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[here](https://wiki.archlinux.org/index.php/Dm-crypt/Device_encryption#Encrypting_devices_with_cryptsetup)
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Functions to implement necessary interaction are implemented in a separate
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`cryptsetup.go` file.
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* LuksFormat
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* LuksOpen
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* LuksClose
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* LuksStatus
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* `CreateVolume`: refactored to prepare for encryption (tag image that it
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requires encryption later), before returning, if encrypted volume option is
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set.
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* `NodeStageVolume`: refactored to call `encryptDevice` method on the very first
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volume attach request
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* `NodeStageVolume`: refactored to open encrypted device (`openEncryptedDevice`)
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* `openEncryptedDevice`: looks up for a passphrase matching the volume id,
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returns the new device path in the form: `/dev/mapper/luks-<volume_id>`.
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On the woker node where the attach is scheduled:
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```shell
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$ lsblk
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NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
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sda 8:0 0 10G 0 disk
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└─sda1 8:1 0 10G 0 part /
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sdb 8:16 0 20G 0 disk
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rbd0 253:0 0 1G 0 disk
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└─luks-pvc-8a710f4c934811e9 252:0 0 1020M 0 crypt /var/lib/kubelet/pods/9eaceaef-936c-11e9-b396-005056af3de0/volumes/kubernetes.io~csi/pvc-8a710f4c934811e9/mount
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```
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* `detachRBDDevice`: calls `LuksClose` function to remove the LUKS mapping
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before detaching the volume.
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* StorageClass extended with following parameters:
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1. `encrypted` ("true" or "false")
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1. `encryptionKMSID` (string representing kms configuration of choice)
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ceph-csi plugin may support different kms vendors with different type of
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authentication
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* New KMS Configuration created.
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#### Annotated YAML for RBD StorageClass
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```yaml
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apiVersion: storage.k8s.io/v1
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kind: StorageClass
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metadata:
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name: csi-rbd
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provisioner: rbd.csi.ceph.com
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parameters:
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# String representing Ceph cluster configuration
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clusterID: <cluster-id>
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# ceph pool
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pool: rbd
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# RBD image features, CSI creates image with image-format 2
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# CSI RBD currently supports only `layering` feature.
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imageFeatures: layering
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# The secrets have to contain Ceph credentials with required access
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# to the 'pool'.
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csi.storage.k8s.io/provisioner-secret-name: csi-rbd-secret
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csi.storage.k8s.io/provisioner-secret-namespace: default
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csi.storage.k8s.io/controller-expand-secret-name: csi-rbd-secret
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csi.storage.k8s.io/controller-expand-secret-namespace: default
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csi.storage.k8s.io/node-stage-secret-name: csi-rbd-secret
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csi.storage.k8s.io/node-stage-secret-namespace: default
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# Specify the filesystem type of the volume. If not specified,
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# csi-provisioner will set default as `ext4`.
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csi.storage.k8s.io/fstype: ext4
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# Encrypt volumes
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encrypted: "true"
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# Use external key management system for encryption passphrases by specifying
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# a unique ID matching KMS ConfigMap. The ID is only used for correlation to
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# configmap entry.
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encryptionKMSID: <kms-id>
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reclaimPolicy: Delete
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```
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And kms configuration:
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```yaml
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---
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apiVersion: v1
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kind: ConfigMap
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data:
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config.json: |-
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{
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"<kms-id>": {
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"encryptionKMSType": "kmsType",
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kms specific config...
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}
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}
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metadata:
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name: ceph-csi-encryption-kms-config
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```
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