Is DOS under Unix immune?

Joe Smith jes at mbio.med.upenn.edu
Sat Aug 4 10:36:55 AEST 1990


> (4) The UNIX filesystem at the 'stdio' level, through a TSR resident 
>     under DOS (Redirect) that uses hooks to the VP/ix executive.

Would it be possible then for all your 'DOS' files to really be UNIX
files, with the appropriate ownership/permissions (e.g. *real*
read-only directories), which would be inaccessible to the DOS
executable?  I mean, just making your COMMAND.COM owned by root, and
mode 755 would be sufficient to stop several of the common viruses (I
presume VP/ix doesn't support the setuid call, and that the Unix
permission bits are mapped appropriately).  Is that sort of thing
possible?

> But any virus that's dependent on such things as precise clock timing
> or transparent access to the controller hardware seems likely to fail,
> although it could certainly lock up the box in failing.

Aren't hardware (i/o) accesses trapped and 'tamed' in some way?  I mean,
I could care less what the goofy DOS software does with my speaker, but
I'd be real uncomfortable knowing it could start fiddling with the disk
controller registers.

As I think about it I guess it's just impossible to accommodate all the
DOS software that assumes it has free reign of the machine without
really giving it that kind of access.

BTW, there was apparently an article in this thread from Peter da
Silva which I couldn't retrieve.  I'd appreciate it if someone could
pass that along by e-mail.

<Joe
--
 Joe Smith
 University of Pennsylvania                    jes at mbio.med.upenn.edu
 Dept. of Biochemistry and Biophysics          (215) 898-8348
 Philadelphia, PA 19104-6059



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