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Date: Thu, 29 Jan 2015 23:39:10 +0100 From: Alexander Holler <holler@...oftware.de> To: Pádraig Brady <P@...igBrady.com>, linux-kernel@...r.kernel.org CC: linux-kbuild@...r.kernel.org, Michal Marek <mmarek@...e.cz>, David Howells <dhowells@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH v2] modsign: use shred to overwrite the private key before deleting it Am 25.01.2015 um 11:32 schrieb Alexander Holler: > Am 25.01.2015 um 03:43 schrieb Alexander Holler: >> Am 25.01.2015 um 03:13 schrieb Pádraig 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? I've filed bugs #92271 (ext4) and #92261 (btrfs) in the kernels bugzilla. That might be a more appropriate place for discussion. Here are the links: https://bugzilla.kernel.org/show_bug.cgi?id=92271 https://bugzilla.kernel.org/show_bug.cgi?id=92261 Regards, Alexander Holler -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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