Re: Internal key management system

On Thu, 19 Mar 2020 at 18:32, Masahiko Sawada
<masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
>
> 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.
>

Attached updated version patch. This patch incorporated the comments
and changed pg_upgrade so that we take over the master encryption key
from the old cluster to the new one if both enable key management.

Regards,

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