Re: [PATCH] tpm: add backend for mssim

[Stefan Berger <stefanb@linux.ibm.com>]

On 12/12/22 11:38, James Bottomley wrote:
> On Mon, 2022-12-12 at 15:47 +0000, Daniel P. Berrangé wrote:
>> Copy'ing Markus for QAPI design feedback.
>>
>> On Sat, Dec 10, 2022 at 12:10:18PM -0500, James Bottomley wrote:
>>> The Microsoft Simulator (mssim) is the reference emulation platform
>>> for the TCG TPM 2.0 specification.
>>>
>>> https://github.com/Microsoft/ms-tpm-20-ref.git
>>>
>>> It exports a fairly simple network socket baset protocol on two
>>> sockets, one for command (default 2321) and one for control
>>> (default 2322).  This patch adds a simple backend that can speak
>>> the mssim protocol over the network.  It also allows the host, and
>>> two ports to be specified on the qemu command line.  The benefits
>>> are twofold: firstly it gives us a backend that actually speaks a
>>> standard TPM emulation protocol instead of the linux specific TPM
>>> driver format of the current emulated TPM backend and secondly,
>>> using the microsoft protocol, the end point of the emulator can be
>>> anywhere on the network, facilitating the cloud use case where a
>>> central TPM service can be used over a control network.
>>
>> What's the story with security for this ?  The patch isn't using
>> TLS, so talking to any emulator over anything other than localhost
>> looks insecure, unless I'm missing something.
> 
> Pretty much every TPM application fears interposers and should thus be
> using the TPM transport security anyway. *If* this is the case, then
> the transport is secure.  Note that this currently isn't the case for

What about all the older kernels that are out there?

> the kernel use of the TPM, but I'm trying to fix that.  The standard
> mssim server is too simplistic to do transport layer security, but like
> everything that does this (or rather doesn't do this), you can front it
> with stunnel4.

And who or what is going to set this up?

    Stefan