[dm-crypt] Encrypt all partitions with dm-crypt

Arno Wagner arno at wagner.name
Thu Aug 23 21:34:15 CEST 2012


On Thu, Aug 23, 2012 at 08:12:43PM +0200, Milan Broz wrote:
> On 08/23/2012 06:07 PM, Arno Wagner wrote:
> >> Debian has full support for cryptsetup/LUKS, 
> > 
> > For encrypted root? News to me, but would be a good thing.
> 
> I am using it for several years on Debian (supported only with combination
> with lvm IIRC).
> 
> >> but not for plain dm-crypt, not to
> >> my knowledge anyway. I think this makes sense as there is no way to
> >> automatically detect an encrypted partition with no header. 
> >>
> >> The only advantage I can see in using encrypted partitions with no header
> >> is to "hide" the encrypted volume, however the partition, cipher and hash
> > 
> > The second one is better resilience, as there is no header 
> > single-point-of-failure. Whether that is worth total loss of
> > key management depends on the application.
> 
> Well, you can have detached LUKS header on USB flash disk (optionally
> with the whole boot partition) for example.

That is not really a good idea. LUKS on Flash/SSD may not work 
as intended. I just added an entry for that to the FAQ (5.17). 
For some scenarios, plain dm-cryp is just the way to go.
Of course, it requires some understanding, e.g. a high-entropy
passphrase is a must.

> (cryptsetup has support for separate LUKS header but no support
> in distros yet I think)
> 
> (You can even have different disk with another header with shifted data
> offset in LUKS header and hide another volume inside the first
> Not that it is comfortable though but possible...)

Hehehe. Messy ;-)
 
> > 
> >> function have to be specified somewhere if one wants the distro to be able
> >> to do automatic configuration.  
> > 
> > Thet is not the issue. Reasonable defaults would do that. The
> > issue is that the partiton type cannot be detected anymore 
> > without the key.
> > 
> >> The bootloader will need it in its
> >> configuration, which doesn't make it any better than LUKS in terms of
> >> discreetness.
> > 
> > Huh? What is the bootloader going to do with that info? Last
> > I checked, you still need a running kernel and system (possibly
> > in the form of an initrd) to do anything with encrypted partitions,
> > no matter whether LUKS or plain. I may be behind times here, if so,
> > please explain.
> 
> Grub2 can handle LUKS directly.

Nice. Finally a reason to switch. 

> (And separate header support is perhaps easy to add.)

Should be. 

Arno
-- 
Arno Wagner,    Dr. sc. techn., Dipl. Inform.,   Email: arno at wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
----
One of the painful things about our time is that those who feel certainty 
are stupid, and those with any imagination and understanding are filled 
with doubt and indecision. -- Bertrand Russell 


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