Previously, all initrd ELFs would be made *world-writable*.
This commit sets the write bit for the file owner exclusively, and
removes it when done. It also sets the umask so that files don't
implicitly become writable for other users by mistake.
Fixes: https://github.com/NixOS/nixpkgs/security/advisories/GHSA-m7pq-h9p4-8rr4
Reported-By: sudoBash418 <sudobash418@gmail.com>
It's extremely frustrating seeing "Error: Os { code: 13, kind:
PermissionDenied, message: "Permission denied" }" without any hint as to
where exactly that occurred.
This commit fixes that by adding context to most errors.
