On Sat, Jan 14, 2023 at 09:55:37AM -0500, James Bottomley wrote: > On Tue, 2023-01-03 at 13:10 -0800, Matthew Garrett wrote: > > On Tue, Jan 3, 2023 at 1:05 PM William Roberts > > <bill.c.roberts@xxxxxxxxx> wrote: > > > > > What's the use case of using the creation data and ticket in this > > > context? Who gets the creationData and the ticket? > > > Could a user supplied outsideInfo work? IIRC I saw some patches > > > flying around where the sessions will get encrypted and presumably > > > correctly as well. This would allow the transfer of that > > > outsideInfo, like the NV Index PCR value to be included and > > > integrity protected by the session HMAC. > > > > The goal is to ensure that the key was generated by the kernel. In > > the absence of the creation data, an attacker could generate a > > hibernation image using their own key and trick the kernel into > > resuming arbitrary code. We don't have any way to pass secret data > > from the hibernate kernel to the resume kernel, so I don't think > > there's any easy way to do it with outsideinfo. > > Can we go back again to why you can't use locality? It's exactly > designed for this since locality is part of creation data. Currently > everything only uses locality 0, so it's impossible for anyone on Linux > to produce a key with anything other than 0 in the creation data for > locality. However, the dynamic launch people are proposing that the > Kernel should use Locality 2 for all its operations, which would allow > you to distinguish a key created by the kernel from one created by a > user by locality. > > I think the previous objection was that not all TPMs implement > locality, but then not all laptops have TPMs either, so if you ever > come across one which has a TPM but no locality, it's in a very similar > security boat to one which has no TPM. Kernel could try to use locality 2 and use locality 0 as fallback. BR, Jarkko
