Re: XTS cipher mode for cluster file encryption

Hi,

On 2021-10-16 10:16:25 -0400, Bruce Momjian wrote:
> As a final comment to Andres's email, adding a GCM has the problems
> above, plus it wouldn't detect changes to pg_xact, fsm, vm, etc, which
> could also affect the integrity of the data. Someone could also restore
> and old copy of a patch to revert a change, and that would not be
> detected even by GCM.

> I consider this a checkbox feature and making it too complex will cause
> it to be rightly rejected.

You're just deferring / hiding the complexity. For one, we'll need integrity
before long if we add encryption support. Then we'll deal with a more complex
on-disk format because there will be two different ways of encrypting. For
another, you're spreading out the security analysis to a lot of places in the
code and more importantly to future changes affecting on-disk data.

If it's really just a checkbox feature without a real use case, then we should
just reject requests for it and use our energy for useful things.

Greetings,

Andres Freund