Kernel drivers and IOCTLs

[Valdis Kl=?utf-8?Q?=c4=93?=tnieks]

On Tue, 04 Feb 2020 20:57:24 -0600, WyoFlippa said:

> I'm actually happy with the existing boot schemes. In this case, the
> driver is going to validate a signed image (U-Boot or Linux) before it
> is programmed into the flash memory. Although the image is validated
> when booting, it is one additional check to avoid surprises.

Is there a reason you're trying to do it from a driver rather than from userspace?

Under what realistic conditions will the kernel be trustable to do the validation
while userspace isn't? What's the threat model here - in other words, what
attack(s) are you trying to stop?  (This is a lot trickier than it looks - over the
decades, I've seen plenty of "Let's do this cargo-cult thing to stop attack X",
while overlooking the fact that any attacker who can do X can equally easily
do Y and still pwn the entire box.....)

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