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    1: [[!meta title="A Keylock Security Model for kauth(9)"]]
    2: 
    3: Recently, generic support for electro-mechanical multi-position keylocks
    4: in the kernel has been added to NetBSD.  Such locks can be turned into
    5: various positions, usually up to three or four position.  They come with
    6: a set of keys that are different in so far as not all positions can be
    7: reached with all keys (which key can go up to which position is called
    8: the "locking program").  With the new keylock support, such locks can be
    9: used to tinker with the kernel security, much like the traditional
   10: securelevel variable...
   11: 
   12: The number of keylock positions, the current keylock position, and the
   13: overall keylock state can be read within the kernel using a set of
   14: functions defined in
   15: [keylock.h](http://cvsweb.de.netbsd.org/cgi-bin/cvsweb.cgi/src/sys/dev/keylock.h?rev=HEAD)
   16: and userland
   17: can access them through the <b>hw.keylock</b> sysctl hierarchy.
   18: 
   19: The following components have been added:
   20: 
   21: * <b>[gpiolock(4)](http://netbsd.gw.com/cgi-bin/man-cgi?gpiolock+4+NetBSD-current)</b>
   22: a driver for GPIO attached keylocks.
   23:  The driver registers with the in-kernel keylock "subsystem". See
   24: [gpiolock.c](http://cvsweb.de.netbsd.org/cgi-bin/cvsweb.cgi/src/sys/dev/gpio/gpiolock.c?rev=HEAD).
   25: 
   26: * <b>secmodel_keylock</b>, a {{manual page|kauth|9}} security model that
   27: authorizes based on the keylock "closedness".  Wheter the rightmost
   28: (default) or leftmost position of the keylock means open can be
   29: controlled using the '''hw.keylock.order''' sysctl variable. This
   30: variable can only be changed if the keylock state is OPEN. See
   31: [secmodel_keylock.c](http://cvsweb.de.netbsd.org/cgi-bin/cvsweb.cgi/src/sys/secmodel/keylock/secmodel_keylock.c?rev=HEAD).
   32: 
   33: The security model is started when a keylock driver registers and
   34: stopped when there is no more keylock driver.  The keylock security
   35: model is optional, keylock support can be used without the security
   36: model as well (e.g. to provide keylock state to a userland applications.
   37: Useful e.g. for POS applications).
   38: 
   39: The keylock state interpretation is done in
   40: [keylock.c](http://cvsweb.de.netbsd.org/cgi-bin/cvsweb.cgi/src/sys/dev/keylock.c?rev=HEAD)
   41: and not in the driver itself.  This
   42: allows for adding support for multiple keylocks in the future.  The
   43: hw.keylock.pos and hw.keylock.npos sysctl variable have debugging
   44: character, the hw.keylock.state variable reflects the state and should
   45: be used.
   46: 
   47: Currently, the keylock positions are interpreted as follows:  There are
   48: maximum four positions, OPEN, SEMIOPEN, SEMICLOSE, CLOSE.  What exactly
   49: that means leaves room for interpretation right now.... (experience will
   50: show what makes sense in the end).
   51: 
   52: To enable the keylock support, the keylock security model, and the
   53: {{manual page|gpiolock|4|}} driver, add the following lines to your
   54: kernel configuration file:
   55: 
   56: 	options KEYLOCK
   57: 	options secmodel_keylock
   58: 	gpiolock* at gpio?
   59: 
   60: Of course you must have at least one GPIO device in your system for the
   61: {{manual page|gpiolock|4|}} driver to work and the lock must be
   62: connected properly.
   63: 
   64: <b>Please keep in mind that this is an experimental feature...</b>