On Wed, 2018-11-21 at 01:13 +0200, Jarkko Sakkinen wrote: > On Tue, Nov 20, 2018 at 09:25:43AM -0800, James Bottomley wrote: > > On Tue, 2018-11-20 at 14:41 +0200, Jarkko Sakkinen wrote: > > > On Tue, Nov 20, 2018 at 01:10:49PM +0200, Jarkko Sakkinen wrote: > > > > This is basically rewrite of TPM genie paper with extras. Maybe > > > > just shorten it to include the proposed architecture and point > > > > to the TPM Genie paper (which is not in the references at all > > > > ATM). > > > > > > > > The way I see it the data validation is way more important than > > > > protecting against physical interposer to be frank. > > > > > > > > The attack scenario would require to open the damn device. For > > > > laptop that would leave physical marks (i.e. evil maid). In a > > > > data center with armed guards I would wish you good luck > > > > accomplishing it. It is not anything like sticking a USB stick > > > > and run. > > > > > > > > We can take a fix into Linux with a clean implementation but it > > > > needs to be an opt-in feature because not all users will want > > > > to use it. > > > > > > Someone (might have been either Mimi or David Howells but cannot > > > recall) correctly pointed out at LSS 2018 that you could just as > > > easily spy and corrupt RAM if you have a time window to perform > > > this type of attack. > > > > Not using the simple plug in on the TPM bus, you can't. The point > > is basically the difference in the technology: the interposer is a > > simple, easy to construct, plugin; a RAM spy is a huge JTAG thing > > that would be hard even to fit into a modern thin laptop, let alone > > extremely difficult to build. > > Why you wouldn't use DMA to spy the RAM? You mean from a plugin on the TPM bus? most of the buses the TPM is on don't get DMA access. Some of them barely get interrupts, which is why we waste a lot of time polling in TPM drivers. James
