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Re: postgres zeroization of dead tuples ? i.e scrubbing dead tuples with sensitive data. - Mailing list pgsql-general

From Alvaro Herrera
Subject Re: postgres zeroization of dead tuples ? i.e scrubbing dead tuples with sensitive data.
Date
Msg-id 20151118201356.GH614468@alvherre.pgsql
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In response to Re: postgres zeroization of dead tuples ? i.e scrubbing dead tuples with sensitive data.  ("David G. Johnston" <david.g.johnston@gmail.com>)
Responses Re: postgres zeroization of dead tuples ? i.e scrubbing dead tuples with sensitive data.  (Melvin Davidson <melvin6925@gmail.com>)
Re: postgres zeroization of dead tuples ? i.e scrubbing dead tuples with sensitive data.  (Tom Lane <tgl@sss.pgh.pa.us>)
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David G. Johnston wrote:
> On Wed, Nov 18, 2015 at 12:45 PM, Day, David <dday@redcom.com> wrote:

> > I believe the   concern,  based on my current understanding  of postgres
> > inner workings,  is  that when a dead tuple is reclaimed by vacuuming:  Is
> > that reclaimed space initialized in some fashion that would  shred any
> > sensitive data that was formerly there to any  inspection by  the
> > subsequent owner of  that disk page ? ( zeroization )

No.  Ultimately, space occupied by dead tuples is "freed" in
PageRepairFragmentation(), src/backend/storage/page/bufpage.c;
the contents of the tuples are shuffled to "defragment" the free space,
but the free space is not zeroed.  You could certainly try to read the
unused page and extract some data from there.

--
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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