Re: [PATCH v8 08/10] tpm: Proxy driver for supporting multiple emulated TPMs

From: Stefan Berger
Date: Wed Mar 16 2016 - 09:50:15 EST

On 03/16/2016 08:09 AM, Jarkko Sakkinen wrote:
On Sun, Mar 13, 2016 at 06:54:38PM -0400, Stefan Berger wrote:
This patch implements a proxy driver for supporting multiple emulated TPMs
in a system.

The driver implements a device /dev/vtpmx that is used to created
a client device pair /dev/tpmX (e.g., /dev/tpm10) and a server side that
is accessed using a file descriptor returned by an ioctl.
The device /dev/tpmX is the usual TPM device created by the core TPM
driver. Applications or kernel subsystems can send TPM commands to it
and the corresponding server-side file descriptor receives these
commands and delivers them to an emulated TPM.

Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
CC: linux-kernel@xxxxxxxxxxxxxxx
CC: linux-doc@xxxxxxxxxxxxxxx
CC: linux-api@xxxxxxxxxxxxxxx
Alternative to this would be to have /dev/vtpmx create:

* /dev/vtpm0 for the server
* /dev/tpm0 for the client

This is how David Howell's PoC worked and that's why I want
to make this alternative visible.

My initial implementation had this as well.

The server could even respawn without container noticing it.
This solution have better availability properties.

A TPM should be stable enough to not have to be respawned...