Re: [OFFTOPIC] Re: Virtual Machines, JVM in kernel

Brandon S. Allbery KF8NH (allbery@kf8nh.apk.net)
Thu, 03 Sep 1998 19:32:08 -0300

In message <y7rvhn4zytr.fsf@sytry.doc.ic.ac.uk>, David Wragg writes:
+-----
| "Brandon S. Allbery KF8NH" <allbery@kf8nh.apk.net> writes:
| > Checking whether the proof is consistent wouldn't be, but how do you verify
| > the proof "goes with" the code? Including a digital signature prevents
| > spoofing, but doesn't promise that the code actually works as the proof
| > claims.
|
| These wouldn't be general proofs of just anything - they would
| naturally refer to the subject of the proof (i.e. the code), so that
| altering the code automatically invalidates the proof.
+--->8

That's the "spoofing" scenario, which as I implied above isn't
"interesting". The point where it falls apart is that a "proof" that some
piece of C code doesn't have any buffer overflows *cannot* be verified.

Type validation is useful, but only when the types themselves prevent
invalid accesses. C types don't insure that you can't write past the limits
of the typed address range (scalar variable, structure, array, etc.), so it
doesn't accomplish anything useful in practice.

-- 
brandon s. allbery	[os/2][linux][solaris][japh]	 allbery@kf8nh.apk.net
system administrator	     [WAY too many hats]	   allbery@ece.cmu.edu
electrical and computer engineering					 KF8NH
carnegie mellon university






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