Date: Mon, 28 Feb 2022 16:42:55 -0500
From: Stephen Frost <sfrost@snowman.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jeff Davis <pgsql@j-davis.com>, samay sharma <smilingsamay@gmail.com>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: Proposal: Support custom authentication methods using hooks
Message-ID: <20220228214255.GO10577@tamriel.snowman.net>
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Greetings,

* Tom Lane (tgl@sss.pgh.pa.us) wrote:
> Stephen Frost <sfrost@snowman.net> writes:
> > md5 should be removed.
>=20
> Really? I've always thought that the arguments against it were
> overblown for our use-case.  At any rate, it's likely to be
> years before we could practically do that, since it's the best
> that older client libraries can manage.

Yes, really, it's a known-broken system which suffers from such an old
and well known attack that it's been given a name: pass-the-hash.  As
was discussed on this thread even, just the fact that it's not trivial
to break on the wire doesn't make it not-broken, particularly when we
use the username (which is rather commonly the same one used across
multiple systems..) as the salt.  Worse, md5 isn't exactly the pinnacle
of hashing techniques around these days.

The wiki page goes over it in some detail regarding LM/NTLM which
suffers the same problem (and also uses a challenge-response for the
over-the-network bits): https://en.wikipedia.org/wiki/Pass_the_hash

Further, a whole bunch of effort was put in to get scram support added
to the different libraries and language bindings and such, specifically
to allow us to get to a point where we can drop md5.  Even after it's
removed, folks will have 5 years before the release that removes it is
the oldest supported release.  I don't think we'll somehow get agreement
to remove it for v15, so it'll be 5 major versions of overlap (11->15)
by the time v16 comes out, and a total of 10 years of support for scram
before md5 is gone.

That's plenty, it's time to move on.

Keeping it around will just push out the point at which everyone will
finally be done with it, as there's really only two groups: those who
have already moved to scram, and those who won't move until they want to
upgrade to a release that doesn't have md5.

Thanks,

Stephen

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