On Tue, Jan 24, 2017 at 12:07:07PM -0700, Jason Gunthorpe wrote: > 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
There should be anyway someway to limit what commands can be sent but I understand your point. Would it make more sense to have a sysfs file for configuring the global filter that would get the data in the same format (list of 16-bit words)? /Jarkko
