Re: HW access allowed ?

Michael Schmitz (schmitzm@uclink4.berkeley.edu)
Wed, 8 Apr 1998 17:58:33 -0700

At 10:51 AM +1200 4/9/98, Chris Wedgwood wrote:
>On Wed, Apr 08, 1998 at 01:55:47PM -0400, David Schwartz wrote:
>
>> I don't know of any operating system that bases permissions on each
>> program. So far as I know, every operating system bases the permissions on
>> those associated with the user that "happens to" run the program. There is
>> no operating system I know of where it is safe for a privileged user to
>> run buggy or malicious userland programs.
>
>WindowsNT can have per-thread permissions. This is similar to VMS. (Only
>with VMS you have a bitmap and under NT you have ACLs).

You have ACLs on VMS as well, so you can install a privileged image and
restrict
access to it (or any other object for that matter) with ACLs.

But that doesn't keep root from doing

$ SET PROC/PRIV=ALL
$ DELEGATE SYS$SYSTEM:*.*;*

or other stupid things you might come up with. Neither does it protect against
buggy or malicious programs run by root (these need to enable all privileges
first, and you're back to square 1). And PHY_IO allows direct access to
hardware
without going through the usual filesystems or even drivers IIRC. So it's
possible in a real OS, just with more safeguards than Linux currently uses
(but that seems to be changing).

Michael

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