[vox-tech] Encrypted CDROM

[Richard Harke]

On Wed August 3 2005 13:03, Michael J Wenk wrote:
> On Wed, Aug 03, 2005 at 12:44:52PM -0700, Richard Harke wrote:
> > Using loopback and cryptsetup (which uses the device mapper)
> > I created an encrypted file system about the size of a CDRom. I put
> > some files into this file system then I burned a CD using cdrecord.
> > No error indications so far. Now I want to read the CD to verify
> > whats on it. When I do a cryptsetup, I get an error. The command is
> >
> > cryptsetup create --size=1431552 aname /dev/cdrom
> >
> > The error I get is Invalid argument to an ioctl call. The ioctl call
> > is trying to load the table to the mapper device. I ran strace but
> > didn't get any more info. I've looked at the source but so far
> > I haven't figured it out.
> >
> > Does any one out there have any ideas?
> >
> > Richard Harke
> > _______________________________________________
>
> All I have is a possible workaround.
>
> dd if=/dev/cdrom of=tmp.iso bs=64k
>
>
> Then run the cryptsetup on the iso file.
>
> More than likely(this is just a stab btw, I am not completely sure of
> what I am talking about and I am going off of memory of how the ioctl's
> interface with the driver on linux) what's happening is the ioctl called
> by the command is not valid with the device in question.  If you make
> the device into a file and then try it with the file, it *may* work.
>
> Mike
That does work. I used dd, then losetup, cryptsetup and finally mount.
I need to use losetup first because cryptsetup works on a device,
not a file. As long as I have lots of hard disk space, I guess I could just
keep the encrypted file-system images on the hard drive and just
write to CD for backup.

I'm still a little curious though as I know the ioctl was to the just created
device-mapper device and it certainly needs a table load to function.

Richard