Re, Re: BSD-fileflags

From: stealthat_private
Date: Sun Jul 04 1999 - 13:46:15 PDT

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    >I might add that to be able to unmount /usr, if that is indeed where
    >/usr/bin/login is being run from, or any other filesystem for that
    >matter, it needs to be totally unused.  For this reason, I think you
    >would be hard pressed to have /usr unmounted in a manner that would
    >go undetected unless you were in single luser mode.  Depending on
    >what else runs on the system and how packages are installed, the
    >same might be true for other file systems often used for installation
    >of binaries (/usr/local).  To give you some idea of the programs which
    >would need to have been stopped before unmounting /usr are as follows:
    >
    >syslogd, update, cron, inetd, getty
    >
    >(according to NetBSD-1.4).  That said, I do think that the claims made
    >by the documentation for securelevel 1 are false and should instead
    >mention something about changing file flags through "conventional means"
    >with a more complete briefing available for securelevel 2.
    
    Right. You will run in trouble if you try to umount /usr without
    'preparing' the system for it. To do this you also have to link UZip statically
    b/c libc is in /usr. This also means the other programs as syslogd etc.
    Some of them (getty) will die without explicitly kill them.
    Althought hard, it's not impossible and on my test system i was able to remove
    an immutable /usr/bin/login _without_ booting into single user (why the hell 'user'
    isn't it for root? :-) mode.
    
    Regardless whats written in the README, you have to define FORCE_OR_NOT to
    MNT_FORCE (not 1) if it should be done the 'umount -f' way, sorry.
    
    Stealth
    
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