Re: MD5 authentication needs help

On Wed, Mar 4, 2015 at 03:59:02PM -0500, Stephen Frost wrote:
> * Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> > Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > > Let me update my list of possible improvements:
> >
> > > 1) MD5 makes users feel uneasy (though our usage is mostly safe)
> >
> > > 2) The per-session salt sent to the client is only 32-bits, meaning
> > > that it is possible to reply an observed MD5 hash in ~16k connection
> > > attempts.
> >
> > > 3) Using the user name for the MD5 storage salt allows the MD5 stored
> > > hash to be used on a different cluster if the user used the same
> > > password.
> >
> > > 4) Using the user name for the MD5 storage salt allows the MD5 stored
> > > hash to be used on the _same_ cluster.
> >
> > > 5) Using the user name for the MD5 storage salt causes the renaming of
> > > a user to break the stored password.
> >
> > What happened to "possession of the contents of pg_authid is sufficient
> > to log in"? I thought fixing that was one of the objectives here.
>
> Yes, it certainly was. I think Bruce was thinking that we could simply
> hash what goes on to disk with an additional salt that's stored, but
> that wouldn't actually work without requiring a change to the wireline
> protocol, which is the basis of this entire line of discussion, in my
> view.

I was not really focused on needing or not needing wire protocol
changes, but rather trying to understand the attack vectors and how they
could be fixed, in general.

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

+ Everyone has their own god. +