secure wiping in BTRFS filesystem ?

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secure wiping in BTRFS filesystem ?

Postby bester69 » 2017-03-31 19:08

Hi,
Can anyone of you put some light in this subject, how to do to wipe files from a btrfs filesytem?

(wipe, sfill, shred, dd,..) I think most of them should work as long as there's not a taken snapshot, but im not sure about it...


Now, im using snaphots as a shrindding method, I'm taking a btrfs snapshot before adding files, then to wipe thoses files, I rollback to the previously snapshot, and then, i delete the subvolume with the files to be wiped, so this way (subvolume deleted) should prevent any information to be recovered,
and finally, i shrink the free filesystem space which should contain deleted subvolume (sfill -fvl /), but im not sure if this is enought..
(i'd like need to know if this method can be hacked, and files recovered) :?:
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Re: secure wiping in BTRFS filesystem ?

Postby edbarx » 2017-04-01 17:50

The crucial question to ask yourself is: does the disk's microcontroller delete everything I command it to delete? If you don't know the answer for sure, you cannot be rationally confident any software will delete everything. Somewhere, I read that some manufacturers make disks that do not erase everything, but I must be sincere to admit that I don't know that this was a joke.
Debian == { > 30, 000 packages }; Debian != systemd
The worst infection of all, is a false sense of security!
It is hard to get away from CLI tools.
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Re: secure wiping in BTRFS filesystem ?

Postby pylkko » 2017-04-01 19:00

The btrfs code base is based on ext4, it is similar in many respects. Subvolumes are like files. But that does not even matter as if you overwrite the disk, then it cannot be recovered (albeit for major players like nation states usign creative means like firmware hacking, but let's just leave that aside for now). So if you dd over the disk space it does not matter whether the data is in btrfs or ext4 or even fat32. But I am not sure I undersatnd what you are asking and maybe I am not reponding to your concern?
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Re: secure wiping in BTRFS filesystem ?

Postby dasein » 2017-04-01 19:31

pylkko wrote:if you dd over the disk space it does not matter whether the data is in btrfs or ext4 or even fat32.

+1

Precisely correct; everything else is irrelevant.
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Re: secure wiping in BTRFS filesystem ?

Postby Head_on_a_Stick » 2017-04-01 19:40

“Such is modern computing: everything simple is made too complicated because it’s easy to fiddle with; everything complicated stays complicated because it’s hard to fix." — Rob Pike

Please read before posting How to report a problem
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Re: secure wiping in BTRFS filesystem ?

Postby bester69 » 2017-04-02 00:03

pylkko wrote:The btrfs code base is based on ext4, it is similar in many respects. Subvolumes are like files. But that does not even matter as if you overwrite the disk, then it cannot be recovered (albeit for major players like nation states usign creative means like firmware hacking, but let's just leave that aside for now). So if you dd over the disk space it does not matter whether the data is in btrfs or ext4 or even fat32. But I am not sure I undersatnd what you are asking and maybe I am not reponding to your concern?

ok,
So, readings all of your posts, We can conclude i was right.

As long as there arent any snapshot with the file we wish to erase, we can use any wipping regular method.
So that, we should ensure as well, the snapshots are also shredding if they contained the files to erase (sfill -fvl / from subvolume 0), to prevent any snapshot can be undeleted, just in case.


Thanks a lot. :)
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