bugtraq - Re: Postgres: pg_hba.conf, md5, pg

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Date: Wed, 20 Apr 2005 18:10:42 -0400 (EDT)
From: Bruce Momjian <pgman@...dle.pha.pa.us>
To: Tom Lane <tgl@....pgh.pa.us>
Cc: "Jim C. Nasby" <decibel@...ibel.org>, Stephen Frost <sfrost@...wman.net>,
   pgsql-hackers@...tgresql.org, bugtraq@...urityfocus.com
Subject: Re: Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords

Tom Lane wrote:
> "Jim C. Nasby" <decibel@...ibel.org> writes:
> > Simply put, MD5 is no longer strong enough for protecting secrets. It's
> > just too easy to brute-force. SHA1 is ok for now, but it's days are
> > numbered as well. I think it would be good to alter SHA1 (or something
> > stronger) as an alternative to MD5, and I see no reason not to use a
> > random salt instead of username.
> 
> Well, I have no particular problem with offering SHA1 as an alternative
> hash method for those who find MD5 too weak ... but I still question the
> value of putting any random salt in the table.  AFAICS you would have to
> send that salt as part of the initial password challenge, which means
> any potential attacker could find it out even before trying to
> compromise pg_shadow; so Stephen's argument that there is a useful
> improvement in protection against precomputation of password hashes
> still falls down.
> 
> BTW, one could also ask exactly what threat model Stephen is concerned
> about.  ISTM anyone who can obtain the contents of pg_shadow has
> *already* broken your database security.

That's what I told him.  I think his concern about pre-computed hashes
is the only real issue, and give 'postgres' is usually the super-user, I
can see someone pre-computing md5 postgres hashes and doing quick
comparisons, perhaps as a root kit so you don't have to do the hashing
yourself.   I personally don't find that very compelling either.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@...dle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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