On Fri Nov 1, 2024 at 11:50 PM EET, Jarkko Sakkinen wrote: > On Fri Nov 1, 2024 at 12:06 PM EET, Jarkko Sakkinen wrote: > > On Fri Sep 13, 2024 at 11:05 PM EEST, Ross Philipson wrote: > > > Expose a sysfs interface to allow user mode to set and query the default > > > locality set for the TPM chip. > > > > > > Signed-off-by: Ross Philipson <ross.philipson@xxxxxxxxxx> > > > > Must be read-only. Should be decided per power cycle. > > I'm throwing one incomplete idea not all things considered... > > So one idea is would be to apply set operation to /dev/tpm0 as ioctl > (would not be available for /dev/tpmrm0). > > Then at least access control rules would apply. > > The open here is that the IMA etc. will use a different locality during > boot-time, like it would also with sysfs attribute. Looking at [1] this would become a problem if TPM2_PolicyLocality based policy is ever used during boot-time. We can make a choice of not allowing such policies for in-kernel clients if agree so, but it is a choice that needs to be locked in. With quick thinking I'm not sure if that is horrible limitation. Also does not obviously affect clients communicating with /dev/tpm0. With that constrain it would not matter if during boot-time different locale is used. With that constraint and "set" in ioctl instead of sysfs attributes that might even work out... Open for feedback. [1] https://trustedcomputinggroup.org/wp-content/uploads/TPM-2.0-1.83-Part-3-Commands.pdf BR, Jarkko
