Re: Internal key management system

On Thu, 19 Mar 2020 at 15:59, Masahiko Sawada
<masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
>
> Sending to pgsql-hackers again.
>
> On Tue, 17 Mar 2020 at 03:18, Bruce Momjian
> <bruce(dot)momjian(at)enterprisedb(dot)com> wrote:
> >
> > On Mon, Mar 16, 2020 at 04:13:21PM +0900, Masahiko Sawada wrote:
> > > On Thu, 12 Mar 2020 at 08:13, Bruce Momjian
> > > <bruce(dot)momjian(at)enterprisedb(dot)com> wrote:
> > > >
> > > > On Fri, Mar 6, 2020 at 03:31:00PM +0900, Masahiko Sawada wrote:
> > > > > On Fri, 6 Mar 2020 at 15:25, Moon, Insung <tsukiwamoon(dot)pgsql(at)gmail(dot)com> wrote:
> > > > > >
> > > > > > Dear Sawada-san
> > > > > >
> > > > > > I don't know if my environment or email system is weird, but the V5
> > > > > > patch file is only include simply a changed list.
> > > > > > and previous V4 patch file size was 64kb, but the v5 patch file size was 2kb.
> > > > > > Can you check it?
> > > > > >
> > > > >
> > > > > Thank you! I'd attached wrong file.
> > > >
> > > > Looking at this thread, I wanted to make a few comments:
> > > >
> > > > Everyone seems to think pgcrypto need some maintenance. Who would like
> > > > to take on that task?
> > > >
> > > > This feature does require openssl since all the encryption/decryption
> > > > happen via openssl function calls.
> > > >
> > > > Three are three levels of encrypt here:
> > > >
> > > > 1. The master key generated during initdb
> > > >
> > > > 2. The passphrase to unlock the master key at boot time. Is that
> > > > optional or required?
> > >
> > > The passphrase is required if the internal kms is enabled during
> > > initdb. Currently hashing the passphrase is also required but it could
> > > be optional. Even if we make hashing optional, we still require
> > > openssl to wrap and unwrap.
> >
> > I think openssl should be required for any of this --- that is what I
> > was asking.
> >
> > > > Could the wrap functions expose the master encryption key by passing in
> > > > empty string or null?
> > >
> > > Currently the wrap function returns NULL if null is passed, and
> > > doesn't expose the master encryption key even if empty string is
> > > passed because we add random IV for each wrapping.
> >
> > OK, good, makes sense, but you see why I am asking? We never want the
> > master key to be visible.
>
> Understood.
>
> >
> > > > I wonder if we should create a derived key from
> > > > the master key to use for pg_wrap/pg_unwrap, maybe by appending a fixed
> > > > string to all strings supplied to these functions. We could create
> > > > another derived key for use in block-level encryption, so we are sure
> > > > the two key spaces would never overlap.
> > >
> > > Currently the master key is 32 bytes but you mean to add fixed string
> > > to the master key to derive a new key?
> >
> > Yes, that was my idea --- make a separate keyspace for wrap/unwrap and
> > block-level encryption.
>
> I understand that your idea is to include fixed length string to the
> 256 bit key in order to separate key space. But if we do that, I think
> that the key strength would actually be the same as the strength of
> weaker key length, depending on how we have the fixed string. I think
> if we want to have multiple key spaces, we need to derive keys from the
> master key using KDF.

Or we can simply generate a different encryption key for block
encryption. Therefore we will end up with having two encryption keys
inside database. Maybe we can discuss this after the key manager has
been introduced.

Regards,

--
Masahiko Sawada http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services