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72 lines
2.4 KiB
Markdown
72 lines
2.4 KiB
Markdown
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# Encryption Key Rotation
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## Proposal
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Subject of this proposal is to add support for rotation of
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encryption keys (KEKs) for encrypted volumes in Ceph-CSI.
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Support for rotating keys on RWX/ROX volumes and filesystem encryption
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with `fscrypt` is out of scope for now and shall be added later.
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## Document Terminology
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- Encryption Key: The passphrase that is used to encrypt and open the device.
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- LUKS: The specification used by dm-crypt to process encrypted volumes on linux.
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## Proposed Solution
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The proposed solution in this document, is to address the rotation
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of encryption keys for encrypted volumes.
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This document outlines the rotation steps for PVCs backed by RBD.
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### Implementation Summary
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This feature builds upon the foundation laid by encrypted pvcs.
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The following new methods are added to `cryptsetup.go` for
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handling the key rotation.
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- `LuksAddKey`: Adds a new key to specified LUKS slot
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- `LuksRemoveKey`: Removes the specified key from its slot using `luksKillSlot`
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- `LuksVerifyKey`: Verifies that the given key exists
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in the given slot using `luksChangeKey`.
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### Implementation Details
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The encryption key rotation request will contain with it
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the volume ID and secrets.
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The secrets are used to generate the credentials for authenticating
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against a ceph cluster.
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These values are then used to call `GenVolFromVolID` to get the
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rbdVolume structure.
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The `VolumeEncryption` struct is modified to make
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`generateNewEncryptionPassphrase` a public member function.
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The `EncryptionKeyRotation` service is registered and implemented
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on the node-plugin.
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The following steps are followed to process the device for key rotation:
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- Create a `rbdvolume` object using volume ID,
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this is done by `GenVolFromVolID`.
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- Fetch the current key from the KMS, it is needed for
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subsequent LUKS operations.
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- Get the device path for the volume by calling `waitForPath` as all LUKS
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operations require the device path.
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- Add the fetched key to LUKS slot 1, this will serve as a backup of the key.
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- Generate a new key and store it locally. It will be updated
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in the KMS at later steps.
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- Remove the existing key from slot 0 upon verifying that the
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key in KMS == the key in slot 0.
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- Add new key to slot 0.
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- Update the new key in the KMS.
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- Fetch the key again and verify that the
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key in KMS == the new key we generated.
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- We can now remove the backup key from slot 1.
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Note that the key in the KMS can always be used to unlock the volume.
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