[CASSANDRA-14107] Dynamic key rotation support for transparent data encryption

• Type: New Feature
• Status: Patch Available
• Priority: Low
• Resolution: Unresolved
• Fix Version/s: 5.x
• Component/s: Legacy/Core
• Labels: encryption
• Assignee: Unassigned
• Reporter: Stefan Podkowinski
• Created: 12/Dec/17 14:42
• Updated: 07/Mar/23 10:54

Description

Handling of encryption keys as introduced in CASSANDRA-9945 takes place by referencing a key alias in either cassandra.yaml, or the header of the (commitlog/hints) file that has been encrypted. Using the alias as literal value will work, but requires some attention when rotating keys.

Currently each time a key is rotated (i.e. adding a new key to the keystore while preserving the previous version), the alias in cassandra.yaml has to be update as well and the node needs to be restarted. It would be more convenient to use a symbolic reference instead. My suggestion here would be to use "<alias>:latest" for referring to the latest version. In this case Cassandra always picks the key with the highest version in "<alias>:<seq_number>".

The non-trivial part of this suggestion is how the "latest" key is referenced in the file header. If we use "latest", e.g. for the commit log header, and the key gets rotated, we'd now try do decrypt the file with the new key, instead of the key it has been created with. Therefor we'd have to introduce an extra step that will resolve the canonical version for "latest" and refer to that one during any encrypt operation.

Issue Links

• depends upon: CASSANDRA-14102 Vault support for transparent data encryption
• is related to: CASSANDRA-9945 Add transparent data encryption core classes