[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v5 1/4] Provide support for the CUSE TPM
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v5 1/4] Provide support for the CUSE TPM |
Date: |
Tue, 31 May 2016 20:10:31 +0100 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
* BICKFORD, JEFFREY E (address@hidden) wrote:
> > * Daniel P. Berrange (address@hidden) wrote:
> > > On Wed, Jan 20, 2016 at 10:54:47AM -0500, Stefan Berger wrote:
> > > > On 01/20/2016 10:46 AM, Daniel P. Berrange wrote:
> > > > >On Wed, Jan 20, 2016 at 10:31:56AM -0500, Stefan Berger wrote:
> > > > >>"Daniel P. Berrange" <address@hidden> wrote on 01/20/2016 10:00:41
> > > > >>AM:
> > > > >>
> > > > >>
> > > > >>>process at all - it would make sense if there was a single
> > > > >>>swtpm_cuse shared across all QEMU's, but if there's one per
> > > > >>>QEMU device, it feels like it'd be much simpler to just have
> > > > >>>the functionality linked in QEMU. That avoids the problem
> > > > >>I tried having it linked in QEMU before. It was basically rejected.
> > > > >I remember an impl you did many years(?) ago now, but don't recall
> > > > >the results of the discussion. Can you elaborate on why it was
> > > > >rejected as an approach ? It just doesn't make much sense to me
> > > > >to have to create an external daemon, a CUSE device and comms
> > > > >protocol, simply to be able to read/write a plain file containing
> > > > >the TPM state. Its massive over engineering IMHO and adding way
> > > > >more complexity and thus scope for failure
> > > >
> > > > The TPM 1.2 implementation adds 10s of thousands of lines of code. The
> > > > TPM 2
> > > > implementation is in the same range. The concern was having this code
> > > > right
> > > > in the QEMU address space. It's big, it can have bugs, so we don't want
> > > > it
> > > > to harm QEMU. So we now put this into an external process implemented
> > > > by the
> > > > swtpm project that builds on libtpms which provides TPM 1.2
> > > > functionality
> > > > (to be extended with TPM 2). We cannot call APIs of libtpms directly
> > > > anymore, so we need a control channel, which is implemented through
> > > > ioctls
> > > > on the CUSE device.
> > >
> > > Ok, the security separation concern does make some sense. The use of CUSE
> > > still seems fairly questionable to me. CUSE makes sense if you want to
> > > provide a drop-in replacement for the kernel TPM device driver, which
> > > would avoid ned for a new QEMU backend. If you're not emulating an
> > > existing
> > > kernel driver ABI though, CUSE + ioctl is feels like a really awful RPC
> > > transport between 2 userspace processes.
>
> > While I don't really like CUSE; I can see some of the reasoning here.
> > By providing the existing TPM ioctl interface I think it means you can use
> > existing host-side TPM tools to initialise/query the soft-tpm, and those
> > should be independent of the soft-tpm implementation.
> > As for the extra interfaces you need because it's a soft-tpm to set it up,
> > once you've already got that ioctl interface as above, then it seems to make
> > sense to extend that to add the extra interfaces needed. The only thing
> > you have to watch for there are that the extra interfaces don't clash
> > with any future kernel ioctl extensions, and that the interface defined
> > is generic enough for different soft-tpm implementations.
>
> > Dave
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
>
>
> Over the past several months, AT&T Security Research has been testing the
> Virtual TPM software from IBM on the Power (ppc64) platform. Based on our
> testing results, the vTPM software works well and as expected. Support for
> libvirt and the CUSE TPM allows us to create VMs with the vTPM functionality
> and was tested in a full-fledged OpenStack environment.
>
> We believe the vTPM functionality will improve various aspects of VM security
> in our enterprise-grade cloud environment. AT&T would like to see these
> patches accepted into the QEMU community as the default-standard build so
> this technology can be easily adopted in various open source cloud
> deployments.
Interesting; however, I see Stefan has been contributing other kernel
patches that create a different vTPM setup without the use of CUSE;
if that's the case then I guess that's the preferable solution.
Jeffrey: Can you detail a bit more about your setup, and how
you're maanging the life cycle of the vTPM data?
Dave
>
> Regards,
> Jeffrey Bickford
> AT&T Security Research Center
> address@hidden
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK