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Re: [Full-disclosure] Cisco IOS Shellcode Presentation

from [Valdis . Kletnieks] Network Security [Permanent Link]
Subject: Re: [Full-disclosure] Cisco IOS Shellcode Presentation
Date: Fri, 29 Jul 2005 22:12:39 -0400 
On Fri, 29 Jul 2005 15:02:51 -1000, Jason Coombs said:


There are any number of technical solutions that one could use to 
redesign, fundamentally, the turing machine so that before each 
operation is performed a verification step is employed to ensure that 
the operation is the correct one in the correct sequence given prior 
configuration settings loaded into memory at the time the device was 
activated.


Ahem. No.  You *can't* "ensure" it (although you *can* do things like bounds
checking to *minimize* issues).

It's called the Turing Halting Problem, and in fact, the 'Turing machine' was
invented specifically to (a) show the problem for that simple architecture, and
then (b) show that all Turing-equivalent systems have the exact same problem.

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