Re: [Qemu-devel] [PATCH 0/7] Provide support for the software TPM emulator

[Daniel P. Berrange]

On Fri, Mar 31, 2017 at 04:10:09PM +0300, Amarnath Valluri wrote:
> Briefly, Theses set of patches introduces:
>  - new TPM backend driver to support software TPM emulators(swtpm(1)).
>  - and few supported fixes/enhancements/cleanup to existing tpm backend code.
> 
> The similar idea was initiated earliar(2) by Stefan Berger(CCed) with slightly
> different approach, using CUSE. As swtpm has excellent support for unix domain
> sockets, hence this implementation uses unix domain sockets to communicate 
> with
> swtpm.
> 
> When Qemu is configured with 'emulator' tpm backend, it spawns 'swtpm' and
> communicates its via Unix domain sockets.

I'm not convinced that having QEMU spawning swtpm itself is a desirable
approach, as it means QEMU needs to have all the privileges that swtpm
will need, so that swtpm can inherit them. At the very least I think we
need to have a way to disable this spawning, so it can connect to a
pre-existing swtpm process that's been spawned ahead of time. This will
let us have stricter privilege separation.

Regards,
Daniel
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