NBackup - zap unused (non-allocated) pages
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Key: CORE-6228
URL: http://tracker.firebirdsql.org/browse/CORE-6228
Project: Firebird Core
Issue Type: Improvement
Components: NBACKUP
Affects Versions: 3.0.5, 2.5.9
Reporter: Arioch
Please add a switch for nbackup that when doing a root ( -b 0 ) snapshot the
non-allocated pages were filled with some constant pattern like 0x00 or 0xFF
instead of actual garbage data.
Should provide
1) decrease in network traffic when creating the root backup. Instead of
passing 4 or 8 od more KB of garbage - just transfere the information that
there is the page, but content is irrelevant.
2) removal of sensitive data from the database
3) better compression when putting resulting backup files into ZIP and likes
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On the #2 benefit, the example:
I just was sorting out my file dumps and found an old database, circa 2014 (FB
2.5.3 Win32 client and Win64 server).
That database used to trigger AV (NULL de-reference) in the fbclient.dll when
doing any select from a specific table.
I just tested on FB 2.5.9, still crashes
On SQL level all the data was dropped back in 2014. There are no other tables
left and the only problematic table has zero records.
PIP shows only 1,5% of the pages are allocates.
On binary level, however, looking in hex, reveals the file still has all the
data there. And that is not my own data.
I tried making the database copy using nbackup -b 0 and it shrunk from 335 to
329 MB, all the sensitive data in the non-used pages remains in it. That
database reproduces the crash, but i can not upload it. If i do gbak - i get
6KB backup file and 800KB restored DB, with no AV reproduced.
I wish i could use nbackup to make the reproducible AV issue, if only i could
be sure in nbackup wiping out sensitive data physically like i did it in 2014
on logical SQL level.
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