u2f-server(1) on Linux
The text 8f291ca59c9a, as Debian 9 (Stretch) shipped it.
Yubico Universal 2nd Factor (U2F) Server Tool
Flags it lists
-
--action -
--appid -
--challenge -
--debug -
--help -
--key-handle -
--origin -
--user-key -
--version -
-V -
-a -
-c -
-d -
-h -
-i -
-k -
-o -
-p