geli - why do I need a keyfile

[Lee Brown]

I want to create a geli provider as authentication only, no password, no
encryption.  I do:

# geli init -a HMAC/SHA256 -e NULL -P -s 4096
geli: No key components given.

instead I tried
# touch /tmp/key
# geli init -a HMAC/SHA256 -e NULL -P -s 4096 -k /tmp/key

test it
# geli attach -p -k /tmp/key

but during boot that fails with with "Cannot find key file size for
/boot/keys/key"
# ls -l /boot/keys/key
-rw-r--r--  1 root wheel 0 Sep 14 11:44 /boot/keys/key

Instead:
# echo " " > /tmp/key
solves that issue, but I still don't get why I even need a key file with -e
NULL?

I'm fine if this is a corner case to be ignored (keyfile required), but I
do think the attach with a zero length key file should fail if it's not
going to work at boot time.  It should be consistent one way or another.

Let me know if I should file a bug report and which way it should be filed
(ie zero length keyfile attach should fail, or zero length keyfile should
work at boot)

Thanks -- lee