Re: [PATCH v20] GSSAPI encryption support

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, Joe Conway <mail(at)joeconway(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Michael Paquier <michael(at)paquier(dot)xyz>, Nico Williams <nico(at)cryptonector(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Robbie Harwood <rharwood(at)redhat(dot)com>
Subject: Re: [PATCH v20] GSSAPI encryption support
Date: 2019-04-04 16:24:52
Message-ID: 20190404162452.GM6197@tamriel.snowman.net
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Greetings,

* Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> I wrote:
> > Stephen Frost <sfrost(at)snowman(dot)net> writes:
> >> So I'm a bit surprised that it's taking 4 minutes for you. I wonder if
> >> there might be an issue related to the KDC wanting to get some amount of
> >> random data and the system you're on isn't producing random bytes very
> >> fast..?
>
> > Not sure. This is my usual development box and it also does mail, DNS,
> > etc for my household, so I'd expect it to have plenty of entropy.
> > But it's running a pretty old kernel, and old Kerberos too, so maybe
> > the explanation is in there somewhere.
>
> Same test on a laptop running Fedora 28 takes a shade under 5 seconds.
> The laptop has a somewhat better geekbench rating than my workstation,
> but certainly not 50x better. And I really doubt it's got more entropy
> sources than the workstation. Gotta be something about the kernel.
>
> Watching the test logs, I see that essentially all the time on the RHEL6
> machine is consumed by the two
>
> # Running: /usr/sbin/kdb5_util create -s -P secret0
>
> steps. Is there a case for merging the two scripts so we only have to
> do that once? Maybe not, if nobody else sees this.

I do think that mergeing them would be a good idea and I can look into
that, though at least locally that step takes less than a second.. I
wonder if you might strace (or whatever is appropriate) that kdb5_util
and see what's taking so long. I seriously doubt it's the actual
kdb5_util code and strongly suspect it's some kernel call.

Thanks!

Stephen

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