| From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
|---|---|
| To: | Magnus Hagander <magnus(at)hagander(dot)net>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Michael Paquier <michael(at)paquier(dot)xyz>, Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Postgres hackers <pgsql-hackers(at)postgresql(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net> |
| Subject: | Re: SCRAM with channel binding downgrade attack |
| Date: | 2018-06-28 08:04:05 |
| Message-ID: | 23820cef-365b-672a-8cbf-7eb0ce2eca38@2ndquadrant.com |
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| Lists: | pgsql-hackers pgsql-www |
On 6/28/18 09:35, Magnus Hagander wrote:
> No, we absolutely still have SCRAM channel binding.
>
> *libpq* has no way to *enforce* it, meaning it always acts like our
> default SSL config which is "use it if available but if it's not then
> silently accept the downgrade". From a security perspective, it's just
> as bad as our default ssl config, but unlike ssl you can't configure a
> requirement in 11.
Isn't this similar to what happened whenever we added a new or better
password method? A MITM that didn't want to bother cracking MD5 could
just alter the stream and request "password" authentication. Same with
MD5->SCRAM, SCRAM->SCRAM+CB, and even a hypothetical future change in
the SCRAM hashing method. Clearly, we need a more comprehensive
solution for this.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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