On Wed, Nov 21, 2018 at 03:08:51AM -0500, Rich Persaud wrote: > On Nov 21, 2018, at 02:18, Jarkko Sakkinen > <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > On Tue, Nov 20, 2018 at 10:42:01PM -0700, Jason Gunthorpe wrote: > > Why you wouldn't use DMA to spy the RAM? > > The platform has to use IOMMU to prevent improper DMA access from > > places like PCI-E slots if you are using measured boot and want to > > defend against HW tampering. > > Yes. This is what I wanted to point out. Windows 10 has VBS to > achieve something like this. > https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-vbs > > The BIOS has to sequence things so that at least pluggable PCI-E slots > > cannot do DMA until the IOMMU is enabled. > > Yep. > > Honestly not sure if we do this all correctly in Linux, or if BIOS > > vendors even implemented this level of protection. The BIOS would have > > to leave the PCI-E root port slots disabled, and configure the ports > > to reject config TLPs from the hostile PCI-E device, and probably a > > big bunch of other stuff.. Then Linux would have to enable the IOMMU > > and then enable the PCI-E ports for operation. > > Linux should have something like VBS. Like James' proposal it does not > solve the puzzle but is one step forward... > > Qubes OS and OpenXT [1][2] can use Linux, Xen, IOMMU and DRTM for boot > integrity and PCI device isolation. They preceded VBS by several years > [3]. Trammell's talk, "Firmware is the new Software" [4] and work on > Heads [5][6] is also relevant. > Rich > 1. https://www.platformsecuritysummit.com/2018/references/#openxt > 2. https://www.platformsecuritysummit.com/2018/topic/boot/ > 3. https://theinvisiblethings.blogspot.com/2011/09/anti-evil-maid.html > 4. https://www.platformsecuritysummit.com/2018/speaker/hudson/ > 5. https://www.trmm.net/Heads > 6. https://puri.sm/posts/the-librem-key-makes-tamper-detection-easy/ Please do not send HTML trashed emails. For more information how to configure your email client, please refer to: https://www.kernel.org/doc/Documentation/email-clients.txt Thank you. /Jarkko
