linux-kernel - Re: [tpmdd-devel] [PATCH RFC 0/4] RFC: in-kernel resource manager

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Date:   Wed, 4 Jan 2017 14:58:10 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     James Bottomley <jejb@...ux.vnet.ibm.com>,
        linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [tpmdd-devel] [PATCH RFC 0/4] RFC: in-kernel resource manager

On Tue, Jan 03, 2017 at 02:54:45PM -0700, Jason Gunthorpe wrote:
> On Mon, Jan 02, 2017 at 09:26:58PM -0800, James Bottomley wrote:
> 
> > OK, so I put a patch together that does this (see below). It all works
> > nicely (with a udev script that sets the resource manager device to
> > 0666):
> > 
> > jejb@...vis:~> ls -l /dev/tpm*
> > crw------- 1 root root  10,   224 Jan  2 20:54 /dev/tpm0
> > crw-rw-rw- 1 root root 246, 65536 Jan  2 20:54 /dev/tpm0rm
> > 
> > I've modified the tss to connect to /dev/tpm0rm by default and it all
> > seems to work.
> > 
> > The patch applies on top of your tabrm branch, by the way.
> 
> If we are making a new /dev/ node we should think more carefully about
> the design.
> 
> - Do we need a cdev node for every chip? What about just '/dev/tpm' and
>   we encode the chip number in the message. Since the exclusive
>   locking is gone this is very doable.

What about backwards compatiblity? Or would this be just for /dev/tpms?
We can consider this.

> - Should we get rid of the read/write protocol and use ioctl instead?
>   As I understand it ioctl is more usable with seccomp and related
>   schemes? I could see passing a TPM FD into a sandbox and wanting the
>   sandbox only able to do do decrypt/encrypt operations, for instance.

Are you suggesting that command/response transaction would be handled
by ioctl instead of read/write pair. Would make sense looking at how
read/write is managed now (it is more or less of a hack because it
actually is a transction).

> - Something to identify tpm chips and help match key data with the
>   proper chip.

Hey, here's what I propose. I take some of the ideas (not all there
have been so many) and bake a v2 of the RFC. Lets see where we are
at then. I won't add any reviewed/tested-by's before we are in the
same line with "big ideas" nor do I create a non-RFC patch set.

> Jason

/Jarkko