From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750797AbdAXTHW (ORCPT ); Tue, 24 Jan 2017 14:07:22 -0500 Received: from quartz.orcorp.ca ([184.70.90.242]:45539 "EHLO quartz.orcorp.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750704AbdAXTHT (ORCPT ); Tue, 24 Jan 2017 14:07:19 -0500 Date: Tue, 24 Jan 2017 12:07:07 -0700 From: Jason Gunthorpe To: Jarkko Sakkinen Cc: tpmdd-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, Peter Huewe , Marcel Selhorst , open list Subject: Re: [PATCH RFC] tpm: define a command filter Message-ID: <20170124190707.GA9899@obsidianresearch.com> References: <20170124000258.16818-1-jarkko.sakkinen@linux.intel.com> <20170124001918.GA29735@obsidianresearch.com> <20170124143600.siyhblj67qaatewi@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170124143600.siyhblj67qaatewi@intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Broken-Reverse-DNS: no host name found for IP address 10.0.0.156 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 24, 2017 at 04:36:00PM +0200, Jarkko Sakkinen wrote: > On Mon, Jan 23, 2017 at 05:19:18PM -0700, Jason Gunthorpe wrote: > > On Tue, Jan 24, 2017 at 02:02:52AM +0200, Jarkko Sakkinen wrote: > > > This commit adds a command filter for whitelisting a set of commands in > > > a TPM space. When a TPM space is created through /dev/tpms0, no > > > commands are allowed. The user of the TPM space must explicitly define > > > the list of commands allowed before sending any commands. This ioctl is > > > a one shot call so that a resource manager daemon can call it before > > > sending the file descriptor to the client. > > > > I don't think it makes sense to have a daemon in user space that > > passes an open'd /dev/tpms0 FD directly to a client.. > > > > It is trivial and more powerful to just proxy the messages. Can you > > see some reason why passing a FD through a daemon would make sense? > > > > The earlier discussion with James was to have some way to apply a > > global command filter to all tpms0 users with the idea that the > > 'right' restricted command set would enable a 0666 cdev node, and no > > daemon. > > Is that a conflicting goal? > > Maybe the ioctl could be restricted by CAP_MAC_ADMIN in that case? I think you need to spell out a clear use case for how userspace should use this filter feature and why having the kernel involved is a necessary element. Driving userspace from the kernel uAPI design is a bit tricky without participation from people writing the user space code. > How would you propose to change the code below? I guess the "core > code" is about right and this is more about API, am I right? Generally, I'm of the opinion it is better to introduce the minimal amount of uAPI at this point and wait until people working on userspace figure out basic questions like, will there be a TPM2 daemon or not.. I would focus now on getting the RFC series finished up, hook the kAPI users into spaces and get it to the point where it does let user & kernel safely share the TPM. Jason