Re: [PATCH v2] modsign: use shred to overwrite the private key before deleting it
From: Alexander Holler
Date: Sun Jan 25 2015 - 05:33:28 EST
Am 25.01.2015 um 03:43 schrieb Alexander Holler:
Am 25.01.2015 um 03:13 schrieb PÃdraig Brady:
On 24/01/15 12:29, Alexander Holler wrote:
Am 24.01.2015 um 13:09 schrieb Alexander Holler:
Am 24.01.2015 um 12:37 schrieb Alexander Holler:
Am 24.01.2015 um 11:45 schrieb Alexander Holler:
It uses shred, in the hope it will somedays learn how to shred
stuff on
FLASH based devices securely too, once that has become possible.
BTW: This is a good example where technology failed to keep the
needs of
users in mind.
Failed completely.
Since ever it's a problem for people to securely delete files on
storage.
Also it should be very simple to securely erase files on block based
devices, people have to try cruel ways in the hope to get securely rid
of files nobody else should be able to see ever again.
It's almost unbelievable how completely the IT industry (including the
field I'm working myself: SW) failed in regard to that since 30
years or
even more.
And it isn't such that this is a new requirement. Humans are doing such
since thousands of years. They use fire to get rid of paper documents
and even the old egypts were able to destroyed stuff on stones by using
simple steps. Just the IT failed completely.
Really unbelievable.
So, sorry if anyone got bored by this mail, but I think that really has
to be said and repeated.
Well not failed completely, just used a different method (encryption).
As for "shredding", that improves in effectiveness the lower you go.
I.E. it's effective for the whole file system (SSD range), or whole
device.
That's the usual broken way to go by adding another layer. And if you
encrypt your whole device, it won't help if you want to delete one file.
As long as the encrypted device is mounted and the blocks aren't
overwritten, the stuff is still there. So your solution would end up with:
- mount encrypted device
- build kernel and secret key
- install kernel and secret key
That's wrong, of course it should read "and signed modules".
- unmount encrypted device
That's almost the same as shredding a whole device just to securely
delete one file, with the added complication that the encryption
requires an authentication, which usually is very uncomfortable to do,
at least if the authentication is somewhat secure.
Or what do you have in mind?
Sorry, but deleting a file such that it isn't readable anymore by anyone
shouldn't be a complicated sequence of geek-stuff and all filesystem and
storage designers should be ashamed that they haven't managed it in
around 30 years to accomplish that simple goal. (imho) ;)
By the way, I still remember the time when people learned that if they
delete a file on a FAT file system, it isn't really gone. Afterwards all
kinds of device-shredding software and hardware appeared.
But instead of fixing that broken design, now, around 30 years later,
this stupid and broken design is almost part of any storage and filesystem.
And even worse, because storage is nowadays often fixed to device (no
floppy anymore you can easily destroy), it often has become almost
impossible to really delete stuff on devices.
E.g. how do you overwrite an eMMC which is soldered, without the
possibility to boot from something else in order to launch the shredding
software?
So we are now at the point that the only way to keep some information
private (forever) is to not store it on any computer.
How crazy or userfriendly is that?
Regards,
Alexander Holler
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