MAC labels are set if MAC is enabled and configured for the user
logging in.
Note that lukemftpd is not considered a supported application when
MAC is enabled, as it does not use the standard system interfaces for
managing user contexts; if lukemftpd is used with labeled MAC policies,
it will not properly give up privileges when switching to the user
account.
Approved by: re
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
d9e2c4241f