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Wed Sep 9 15:47:01 2020 UTC (3 years ago) by kim
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    1: [[!meta title="A Keylock Security Model for kauth(9)"]]
    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...
   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](
   16: and userland
   17: can access them through the <b>hw.keylock</b> sysctl hierarchy.
   19: The following components have been added:
   21: * <b>[[!template id=man name="gpiolock" section="4"]]</b>
   22: a driver for GPIO attached keylocks.
   23:  The driver registers with the in-kernel keylock "subsystem". See
   24: [gpiolock.c](
   26: * <b>secmodel_keylock</b>, a
   27: [[!template id=man name="kauth" section="9"]]
   28: security model that
   29: authorizes based on the keylock "closedness".  Wheter the rightmost
   30: (default) or leftmost position of the keylock means open can be
   31: controlled using the <b>hw.keylock.order</b> sysctl variable. This
   32: variable can only be changed if the keylock state is OPEN. See
   33: [secmodel_keylock.c](
   35: The security model is started when a keylock driver registers and
   36: stopped when there is no more keylock driver.  The keylock security
   37: model is optional, keylock support can be used without the security
   38: model as well (e.g. to provide keylock state to a userland applications.
   39: Useful e.g. for POS applications).
   41: The keylock state interpretation is done in
   42: [keylock.c](
   43: and not in the driver itself.  This
   44: allows for adding support for multiple keylocks in the future.  The
   45: hw.keylock.pos and hw.keylock.npos sysctl variable have debugging
   46: character, the hw.keylock.state variable reflects the state and should
   47: be used.
   49: Currently, the keylock positions are interpreted as follows:  There are
   50: maximum four positions, OPEN, SEMIOPEN, SEMICLOSE, CLOSE.  What exactly
   51: that means leaves room for interpretation right now.... (experience will
   52: show what makes sense in the end).
   54: To enable the keylock support, the keylock security model, and the
   55: [[!template id=man name="gpiolock" section="4"]]
   56: driver, add the following lines to your
   57: kernel configuration file:
   59: 	options KEYLOCK
   60: 	options secmodel_keylock
   61: 	gpiolock* at gpio?
   63: Of course you must have at least one GPIO device in your system for the
   64: [[!template id=man name="gpiolock" section="4"]]
   65: driver to work and the lock must be
   66: connected properly.
   68: <b>Please keep in mind that this is an experimental feature...</b>

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