Introduce support for Mandatory Access Control and extensible kernel access control.
Introduce support for Mandatory Access Control and extensible
kernel access control.

Instrument ctty driver invocations of various vnode operations on the
terminal controlling tty to perform appropriate MAC framework
authorization checks.

Note: VOP_IOCTL() on the ctty appears to be authorized using NOCRED in
the existing code rather than td->td_ucred.  Why?

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs

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