Bug#371135: [Pkg-cryptsetup-devel] Bug#371135: encrypted swap with variable key fails

[Andrew Pimlott]

On Tue, Jun 20, 2006 at 11:28:57PM +0200, Jonas Meurer wrote:
> On 20/06/2006 Andrew Pimlott wrote:
> > On Tue, Jun 20, 2006 at 10:10:24PM +0200, Jonas Meurer wrote:
> > But as I understand, a randomly keyed partition can't be done with Luks
> > (or can it?).
> 
> first, LUKS devices with random key are possible, you just need to store
> the random key after luksFormat, to reuse it for luksOpen. afterwards
> you can shred/wipe the key.

True, but this can't be configured in crypttab, which makes it
effectively unavailable.  Moreover, it wouldn't provide much additional
safety.  Presumably, a hypothetical "luksrandom" keyword in crypttab
would mean: check that it's a luks partition, than re-luksFormat and
luksOpen with the same random key.  The problem is, this would happily
trash any normal (non-randomly-keyed) luks partition.  So you really
want an explicit marker that says "I am disposable".

> > However it may still be overkill.  I would be happy enough if there were
> > a check for randomly keyed swap partitions that verifies that the source
> > device is 1) not a formatted, unencrypted volume and 2) not Luks.
> > That's still a good measure of safety.
> 
> yes, that's exactly what i suggested as well. in my opinion, up to now all
> other proposed checks are compromises which have disadvantages as well.

Cool.  So you would special case a key of /dev/*random, and perform only
those two checks?  In other words, would my existing configuration

    swap    /dev/hda2 /dev/urandom  swap

start working again?  That sounds like a nice resolution.

Andrew