[dm-crypt] About CVE-2016-4484: - Cryptsetup Initrd root Shell

David Niklas doark at mail.com
Tue Nov 29 15:56:28 CET 2016


On Wed, 16 Nov 2016 14:48:27
Arno Wagner <arno at wagner.name> wrote:
> On Wed, Nov 16, 2016 at 08:32:12 CET, Milan Broz wrote:
> > On 11/16/2016 02:15 AM, Sven Eschenberg wrote:
> > ...  
> > > 
> > > There's a whole bunch of headlines among these lines. I've read
> > > that cryptsetup has a vulnerability exposing a root-shell on an
> > > encrypted system. Not quite so.  
> > 
> > Yes, this is the real "contribution" of reporting a bug with
> > (possibly even unrelated) project name in headlines.
> > 
> > But seems users themselves correct some stupid article comments,
> > thanks for it! ;-)
> > 
> > Sometimes I wish security is less theater and more responsibility...
> > (This bug cost me hours of explanation that upstream has nothing to
> > fix and that in fact the cryptsetup/LUKS worked as designed.)  
> 
> Tell me about it. I have these discussions regularly as a 
> security consultant, simply because a lack of understanding
> on customer side and attribution of errors by keyword-matching
> instead. 
> 
> I think I will add a new section to the FAQ dealing with initrd
> issues. 
> Contens: 
> 1) No, the initrd is _not_ part of cryptsetup, it is your
>    distro that screwed up if it is broken or insecure.
> 2) If you depend on the initrd doing something seucrely,
>    roll your own and lock that down.
> 3) (Maybe an example...)
> 
> Regards,
> Arno
> 

Personally, I've know about this for years (because I could not
remember my password one day), and I thought it was helpful to be able to
drop to a shell when cryptsetup does not return 0.
Great debugging aide if you wrote something wrong in the intrid.

Besides, if I was truly an evil attacker with physical access, surly I
could come up with a better attack then this one (Change out the
cpu/CMOS/BIOS with an evil one! No more TPE! No more Intel TxT! No more
*secure* hardware crypto devices! Etc.!!!).

Sincerely,
David


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