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?). * Possibly sleep for few seconds. Is this a good idea? 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. Here are all the ideas that I have and I am open for better alternatives. /Jarkko
