Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS)

On Tue, Jul 9, 2019 at 11:09:01AM -0400, Bruce Momjian wrote:
> On Tue, Jul 9, 2019 at 10:59:12AM -0400, Stephen Frost wrote:
> > * Bruce Momjian (bruce(at)momjian(dot)us) wrote:
> > I agree that all of that isn't necessary for an initial implementation,
> > I was rather trying to lay out how we could improve on this in the
> > future and why having the keying done at a tablespace level makes sense
> > initially because we can then potentially move forward with further
> > segregation to improve the situation. I do believe it's also useful in
> > its own right, to be clear, just not as nice since a compromised backend
> > could still get access to data in shared buffers that it really
> > shouldn't be able to, even broadly, see.
>
> I think TDE is feature of questionable value at best and the idea that
> we would fundmentally change the internals of Postgres to add more
> features to it seems very unlikely. I realize we have to discuss it so
> we don't block reasonable future feature development.

I have a new crazy idea. I know we concluded that allowing multiple
independent keys, e.g., per user, per table, didn't make sense since
they have to be unlocked all the time, e.g., for crash recovery and
vacuum freeze.

However, that assumes that all heap/index pages are encrypted, and all
of WAL. What if we encrypted only the user-data part of the page, i.e.,
tuple data. We left xmin/xmax unencrypted, and only stored the
encrypted part of that data in WAL, and didn't encrypt any more of WAL.
That might allow crash recovery and the freeze part of VACUUM FREEZE to
work. (I don't think we could vacuum since we couldn't read the index
pages to find the matching rows since the index values would be encrypted
too. We might be able to not encrypt the tid in the index typle.)

Is this something considering in version one of this feature? Probably
not, but later? Never? Would the information leakage be too great,
particularly from indexes?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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