On Wed, 2012-10-31 at 23:19 +0100, Oliver Neukum wrote: > On Wednesday 31 October 2012 15:58:05 Chris Friesen wrote: > > On 10/31/2012 02:14 PM, Oliver Neukum wrote: > > > > That would do it on my system. > > > Maybe in theory you could solve this by the kernel invalidating images > > > it hasn't written itself and forbidding to change the resume partition from the > > > kernel command line, but that would break user space hibernation. > > > > If the resuming kernel refuses to resume from images it didn't create > > itself, why do you need to forbid changing the resume partition from the > > kernel command line? > > You don't. Signed images solve the problem. I really don't think they do. The proposed attack vector is to try to prevent a local root exploit from running arbitrary in-kernel code, because that would compromise the secure boot part of the kernel. I really think that's mythical: a local privilege elevation attack usually exploits some bug (classically a buffer overflow) which executes arbitrary code in kernel context. In that case, the same attack vector can be used to compromise any in-kernel protection mechanism including turning off the secure boot capability and reading the in-kernel private signing key. There have been one or two privilege elevation attacks that didn't involve in-kernel code (usually by compromising a suid binary or other cross domain scripting attack) that would only compromise local root and thus be confined to the secure boot prison but they are, historically, a minority. The point I'm making is that given that the majority of exploits will already be able to execute arbitrary code in-kernel, there's not much point trying to consider features like this as attacker prevention. We should really be focusing on discussing why we'd want to prevent a legitimate local root from writing to the suspend partition in a secure boot environment. James -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
