CONFIG_MODULE_SIG and the unreproducible Linux Kernel

[kpcyrd]

Dear list,

there has been a recent public discussion on the Arch Linux gitlab about 
the challenges and possible opportunities for making the Linux kernel 
package reproducible that I want to share:

https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/merge_requests/1

This is related to `#Build·time·autogenerated·kernel·key0·` and the 
/sys/kernel/security/lockdown feature (that is currently blocking a 
reproducible Arch Linux kernel).

My personal favorite implementation of that feature would be a hashset 
of allowed module hashes that is generated during the kernel build and 
then embedded in the kernel image. This approach is authority-less[1], 
can be implemented in a reproducible way, doesn't require access to any 
secrets for building and makes it easy to reason about the set of 
modules the computer will/won't load. As far as I know it's currently 
not possible to configure the Linux build like this, so consider this a 
feature request.

cheers,
kpcyrd

[1]: besides the authority that decides on the source code inputs, build 
instructions and build environment of course