Re: Internal key management system

On Mon, Mar 16, 2020 at 04:13:21PM +0900, Masahiko Sawada wrote:
> On Thu, 12 Mar 2020 at 08:13, Bruce Momjian
> <bruce.momjian@enterprisedb.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.pgsql@gmail.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.

> >  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.

> > pgcryptokey shows a method for creating a secret between client and
> > server using SQL that does not expose the secret in the server logs:
> >
> >         https://momjian.us/download/pgcryptokey/
> >
> > I assume we will create a 256-bit key for the master key, but give users
> > an option of  128-bit vs 256-bit keys for block-level encryption.
> > 256-bit keys are considered necessary for security against future
> > quantum computing attacks.
> 
> 256-bit keys are more weaker than 128-bit key in terms of quantum
> computing attacks?

No, I was saying we are using 256-bits for the master key and might
allow 128 or 256 keys for block encryption.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
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