From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: DSM segment handle generation in background workers |
Date: | 2018-11-14 07:52:18 |
Message-ID: | 20181114075218.GE1096408@rfd.leadboat.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Wed, Nov 14, 2018 at 08:22:42PM +1300, Thomas Munro wrote:
> On Wed, Nov 14, 2018 at 6:34 PM Noah Misch <noah(at)leadboat(dot)com> wrote:
> > On Wed, Nov 14, 2018 at 05:50:26PM +1300, Thomas Munro wrote:
> > > On Wed, Nov 14, 2018 at 3:24 PM Noah Misch <noah(at)leadboat(dot)com> wrote:
> > > > What counts is the ease of predicting a complete seed. HEAD's algorithm has
> > > > ~13 trivially-predictable bits, and the algorithm that stood in BackendRun()
> > > > from 98c5065 until 197e4af had no such bits. You're right that the other 19
> > > > bits are harder to predict than any given 19 bits under the old algorithm, but
> > > > the complete seed remains more predictable than it was before 197e4af.
> > >
> > > However we mix them, given that the source code is well known, isn't
> > > an attacker's job really to predict the time and pid, two not
> > > especially well guarded secrets?
> >
> > True. Better to frame the issue as uniform distribution of seed, not
> > unpredictability of seed selection.
>
> What do you think about the attached?
You mentioned that you rewrote the algorithm because the new function had a
TimestampTz. But the BackendRun() code, which it replaced, also had a
TimestampTz. You can reuse the exact algorithm. Is there a reason to change?
From | Date | Subject | |
---|---|---|---|
Next Message | Andres Freund | 2018-11-14 08:01:52 | Re: [RFC] Removing "magic" oids |
Previous Message | Michael Paquier | 2018-11-14 07:51:51 | Re: Restore CurrentUserId only if 'prevUser' is valid when abort transaction |