Re: MD5 authentication needs help

On Wed, Mar 4, 2015 at 05:56:25PM -0800, Josh Berkus wrote:
> Catching up here ...
>
> On 03/03/2015 06:01 PM, Bruce Momjian wrote:
> > It feels like MD5 has accumulated enough problems that we need to start
> > looking for another way to store and pass passwords. The MD5 problems
> > are:
> >
> > 1) MD5 makes users feel uneasy (though our usage is mostly safe)
> >
> > 2) The per-session salt sent to the client is only 32-bits, meaning
> > that it is possible to reply an observed MD5 hash in ~16k connection
> > attempts.
>
> Seems like we could pretty easily increase the size of the salt. Of
> course, that just increases the required number of connection attempts,
> without really fixing the problem.
>
> > 3) Using the user name for the MD5 storage salt allows the MD5 stored
> > hash to be used on a different cluster if the user used the same
> > password.
>
> This is a feature as well as a bug. For example, pgBouncer relies on
> this aspect of md5 auth.
>
> > 4) Using the user name for the MD5 storage salt causes the renaming of
> > a user to break the stored password.
>
> Wierdly, in 17 years of Postgres, I've never encountered this issue.
>
> So, are we more worried about attackers getting a copy of pg_authid, or
> sniffing the hash on the wire?

Both. Stephen is more worried about pg_authid, but I am more worried
about sniffing.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +