On Thu, Oct 26, 2017 at 01:16:32PM +0200, Jarkko Sakkinen wrote: > On Thu, Oct 26, 2017 at 12:26:10AM +0200, Peter Huewe wrote: > > > > > > Am 25. Oktober 2017 20:53:49 MESZ schrieb Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>: > > >On Wed, Oct 25, 2017 at 07:17:17AM -0700, Matthew Garrett wrote: > > >> On Wed, Oct 25, 2017 at 6:44 AM, Jarkko Sakkinen > > >> <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > >> > I'm implementing a fix for CVE-2017-15361 that simply blacklists > > >> > vulnerable FW versions. I think this is the only responsible action > > >from > > >> > my side that I can do. > > >> > > >> I'm not sure this is ideal - do Infineon have any Linux tooling for > > >> performing firmware updates, and if so will that continue working if > > >> the device is blacklisted? It's also a poor user experience to have > > >> systems using TPM-backed disk encryption keys suddenly rendered > > >> unbootable, and making it as easy as possible for people to do an > > >> upgrade and then re-seal secrets with new keys feels like the correct > > >> approach. > > > > > >I talked today with Alexander Steffen in the KS unconference and we > > >concluded that this would be a terrible idea. > > > > > >Alexander stated the following things about FW updates (Alexander, > > >please correct me if I state something incorrectly or if you have > > >something to add): > > > > > >* FW update can be constructed either in a way that the keys in the > > > NVRAM are not cleared or in a way that they are cleared. > > >* FW update cannot be directly applied to the TPM but must come as > > > part of the firmware update from the vendor. > > > > > >I proposed the following as an alternative: > > > > > >* Print a message to the klog (which log level would be appropriate?). > > Info? > > Maybe warn, definitely not err > > Since the driver does not fail usually warn would make sense but since > here even allowing to continue to use such TPM is questionable I would > use error here. > > People anyway ignore klog too easily so using warn would be a mistake in > my opinion. It's like saying that nothing serious is happening here, > move along. > > Do you think so? > > > >* Possibly sleep for few seconds. Is this a good idea? > > Helps how? > > Obviously to get it noticed that the system integrity is broken. > > > >While writing this email yet another alternative popped into my mind: > > >what if we allow only in-kernel use but disallow the use of /dev/tpm0? > > >You could still use trusted keys. > > > > > No, same terrible idea since you block the upgrade path. > > Upgrade tools work from userspace via the kernel driver. > > So /dev/tpm0 is necessary. > > Right! How stupid of me (my previous response to Jerry) :-) Of course you > can have special commands and talk to the TPM to do the upgrade even if > it is part of the platform and not connected to a standard bus. > > I got understanding in the yesterdays unconfernce discussion that it > should be part of the firmware upgrade. > > How do you do the upgrade through /dev/tpm0? > > /Jarkko I received the following email for iavael@xxxxxxxxxxx: <quote> Hello, I'm writing regarding you mail in tpm fw update discussion from Wed, 25 Oct 2017 20:53:49 +0200. Found it in lkml archive and cannot forward it to myself (captcha is broken), so I cannot join discussion in maillist and writing directly. There's a tool infineon-firmware-updater (found with tricky google-fu) Here's an archive https://gsdview.appspot.com/chromeos-localmirror/distfiles/infineon-firmware-updater-1.1.2459.0.tar.gz And here are some patches and ebuild file https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/chromeos-base/infineon-firmware-updater/ > * FW update can be constructed either in a way that the keys in the > NVRAM are not cleared or in a way that they are cleared. As far as I understand, this tool requires clearing TPM. > * FW update cannot be directly applied to the TPM but must come as > part of the firmware update from the vendor. Some vendors mentioned here https://www.infineon.com/cms/en/product/promopages/tpm-update/ distribute infineon's update tool for windows (actually 2 variants of it: CLI and GUI). Looks like Google got source code of it's *nix variant. </quote> /Jarkko
