On Wed, Aug 10, 2022 at 06:37:18PM +0930, Brendan Trotter wrote: > [1] doesn't provide any useful information. How does a kernel know > that the callback provided by boot loader actually measures what it's > supposed to measure, or even does anything at all? The kernel has no way to know this - *any* code you've run before performing a measurement could tamper with the kernel such that it believes it's fine. This is just as true in DRTM as it is in SRTM. But you know what the expected measurements should be, so you're able to either seal secrets to those PCR values or rely on remote attestation. > [1] doesn't provide any useful information. Senter and skinit don't > provide a method for kernel to detect that (e.g.) a MiTM boot loader > has always measured a forgery and has changed unmeasured code in a > different way every time you boot. Measurements are not opaque objects. If you're not able to reconstruct the expected measurement then you're doing it wrong.
