Messages in this thread | | | Date | Wed, 4 Apr 2018 08:57:43 -0400 | From | "Theodore Y. Ts'o" <> | Subject | Re: [GIT PULL] Kernel lockdown for secure boot |
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On Wed, Apr 04, 2018 at 04:30:18AM +0000, Matthew Garrett wrote: > What I'm afraid of is this turning into a "security" feature that ends up > being circumvented in most scenarios where it's currently deployed - eg, > module signatures are mostly worthless in the non-lockdown case because you > can just grab the sig_enforce symbol address and then kexec a preamble that > flips it back to N regardless of the kernel config.
Whoa. Why doesn't lockdown prevent kexec? Put another away, why isn't this a problem for people who are fearful that Linux could be used as part of a Windows boot virus in a Secure UEFI context?
If lockdown simply included a requirement for a signed kernel for kexec --- and if kernel signing aren't available, to simply not alow kexec, wouldn't that take care of this case?
This wouldn't even be all that much of a burden for non-distro users with lockdown enabled, since in my experience outside of enterprise and data center use cases, kexec isn't used --- and in fact, very often kexec doesn't even work outside of a very carefully selected and bug-fixed set of device drivers. (It often doesn't work in non-distro kernels because very few upstream developers really care about kexec.)
- Ted
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