On Thu, 11 Jun 2020 at 20:03, Fabien COELHO <coelho@cri.ensmp.fr> wrote:
>
>
> Hello Masahiko-san,
>
> >> If the KEK is ever present in pg process, it presumes that the threat
> >> model being addressed allows its loss if the process is compromised, i.e.
> >> all (past, present, future) security properties are void once the process
> >> is compromised.
> >
> > Why we should not put KEK in pg process but it's okay for other
> > processes?
>
> My point is "elsewhere".
>
> Indeed, it could be on another process on the same host, in which case I'd
> rather have the process run under a different uid, which means another
> compromission would be required if pg is compromissed locally ; it could
> also be in a process on another host ; it could be on some special
> hardware. Your imagination is the limit.
>
> > I guess you're talking about a threat when a malicious user logged in OS
> > (or at least accessible) but I thought there is no difference between pg
> > process and other processes in terms of the process being compromised.
>
> Processes are isolated based on uid, unless root is compromised. Once a id
> is compromised (eg "postgres"), the hacker has basically access to all
> files and processes accessible to that id.
>
> > So the solution, in that case, would be to outsource
> > encryption/decryption to external servers as Bruce mentioned.
>
> Hosting stuff (keys, encryption) on another server is indeed an option if
> "elsewhere" is implemented.
If I understand your idea correctly we put both DEK and KEK
"elsewhere", and a postgres process gets only DEK from it. It seems to
me this idea assumes that the place storing encryption keys employees
2-tire key hierarchy or similar thing. What if the user wants to or
has to manage a single encryption key? For example, storing an
encryption key for PostgreSQL TDE into a file in a safe server instead
of KMS using DEK and KEK because of budgets or requirements whatever.
In this case, if the user does key rotation, that encryption key would
need to be rotated, resulting in the user would need to re-encrypt all
database data encrypted with old key. It should work but what do you
think about how postgres does key rotation and re-encryption?
Regards,
--
Masahiko Sawada http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services