[38483] in bugtraq
Re: [HACKERS] Postgres: pg_hba.conf, md5, pg_shadow, encrypted passwords
daemon@ATHENA.MIT.EDU (Bruce Momjian)
Wed Apr 20 18:37:18 2005
From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200504202210.j3KMAgf21874@candle.pha.pa.us>
In-Reply-To: <6070.1114034598@sss.pgh.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 20 Apr 2005 18:10:42 -0400 (EDT)
Cc: "Jim C. Nasby" <decibel@decibel.org>, Stephen Frost <sfrost@snowman.net>,
pgsql-hackers@postgresql.org, bugtraq@securityfocus.com
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Tom Lane wrote:
> "Jim C. Nasby" <decibel@decibel.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@candle.pha.pa.us | (610) 359-1001
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