From: Bruce Momjian <bruce@momjian.us>
To: Stephen Frost <sfrost@snowman.net>
Cc: Álvaro Hernández Tortosa <aht@8kdata.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Some thoughts about SCRAM implementation
Date: Tue, 11 Apr 2017 21:25:32 -0400
Message-ID: <20170412012532.GF20340@momjian.us> (raw)
In-Reply-To: <20170412005830.GU9812@tamriel.snowman.net>
References: <df8c6e27-4d8e-5281-96e5-131a4e638fc8@8kdata.com>
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<729b548a-f434-f31c-15e7-59f44aaecc8d@8kdata.com>
<20170410183230.oxagjpfgj6xxmcwx@alap3.anarazel.de>
<fd4530e0-f016-4eb9-a0d0-e32824482db5@8kdata.com>
<20170412004118.GC20340@momjian.us>
<20170412005830.GU9812@tamriel.snowman.net>
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On Tue, Apr 11, 2017 at 08:58:30PM -0400, Stephen Frost wrote:
> > > But just a bit more is needed to make it really a big announcement and
> > > provide real value to (I guess, mostly but very interesting) enterprise
> > > customers, for which MITM and impersonating are big things. The good news is
> > > that adding channel binding is like inverse Paretto: a 20% of extra effort
> > > (I bet significantly less) leads to 80% improvement.
> >
> > I don't see why channel binding is a big deal for enterprises because I
> > assume they are already using SSL:
>
> Channel binding should be used with SSL to ensure that there is no
> man-in-the-middle attack being performed. It's necessary when the
> end-points aren't performing full, mutual, certificate-based
> verification.
And which enterprises are using SSL without certificates? And I thought
channel binding required certificates anyway, e.g.:
https://en.wikipedia.org/wiki/Salted_Challenge_Response_Authentication_Mechanism#Channel_binding
For instance, for the tls-server-end-point channel binding, it is the
server's TLS certificate.
> > I think the big win for SCRAM is the inability to replay md5 packets
> > after recording 16k sessions (salt was only 32-bit, so a 50% chance of
> > replay after 16 sessions), and storage of SHA256 hashes instead of MD5
> > in pg_authid, though the value of that is mostly a check-box item
> > because collisions are not a problem for the way we use MD5.
>
> There are a lot of wins to having SCRAM implemented. I disagree
> strongly that securing PG from attacks based on latent information
> gathering (backups which include pg_authid) is just a "check-box" item.
Well, they have the entire backup so I don't think cracking the password
is a huge win, though the password does potentially give them access to
future data. And it prevents them from reusing the password on another
server, but _again_, I still think the big win is to prevent replay
after 16k packets are sniffed.
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
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Cc: bruce@momjian.us, sfrost@snowman.net, aht@8kdata.com, andres@anarazel.de, hlinnaka@iki.fi
Subject: Re: Some thoughts about SCRAM implementation
In-Reply-To: <20170412012532.GF20340@momjian.us>
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