SIP and built-in filesystems (HFS)

[Joel Cretan]

Hi all,

I saw in this thread that System Integrity Protection on 10.11 or
later shouldn't necessarily get in the way of a FUSE for macOS
filesystem (I'm using 3.5.2):
https://groups.google.com/forum/#!topic/osxfuse-group/SoQjsrnkp7c

I've had trouble with my case, though, and I'm not sure if I'm doing
something wrong, or if my case is simply not possible with SIP.

Normally, do you put your .fs bundle in /Library/Filesystems instead
of /System/Library/Filesystems? Is that the suggested place now? And
should the mount_$(FS_name) program go in /usr/sbin? (it seems that
/usr/local/* is not a path that mount checks?:
https://opensource.apple.com/source/diskdev_cmds/diskdev_cmds-557.3.1/mount.tproj/mount.c)

I'm worried that if this is how you all do it now with SIP, my case
may not work. I'm updating a working filesystem for pre-SIP systems,
which overrides the built-in hfs.fs bundle, for old HFS-standard
volumes. From my testing so far, it seems like it must be in
/System/Library/Filesystems, or else the default hfs.fs there will be
used (my Info.plist sets FSMediaTypes/Apple_HFS/FSProbeOrder = 900, to
override the value 1000 from hfs.fs). Furthermore, with SIP disabled,
it does not work when my mount_ program is in /usr/sbin instead of
/sbin.

As far as anyone knows, is my case possible with SIP enabled, or must
I in fact use /System/Library/Filesystems? Would getting a kernel
extension signing certificate from Apple help?

Thanks,
Joel