Re: Writing Secure code

From: Valdis.Kletnieks@vt.edu
Date: 12/27/02

  • Next message: Alex Russell: "Re: Writing Secure code" 
    To: Rahul Chander Kashyap <rahul@nsecure.net>
From: Valdis.Kletnieks@vt.edu
Date: Fri, 27 Dec 2002 13:03:08 -0500

    On Fri, 27 Dec 2002 18:16:17 +0530, Rahul Chander Kashyap <rahul@nsecure.net> said:

    > And one more thing...<this one might be intresting ;-)> Is it possible
    > to write code that is completely secure and not exploitable?

    This is just a specific case of the question "Is it possible to write
    totally bug-free code"? And yes, it's *possible* to write bug-free code.
    The problem is that it's incredibly difficult to manage the development
    process in such a way that bugs are totally prevented - remember that humans
    are writing the code, and humans are.. well... human. ;)

    On the flip side, good development practices can probably gain us 2 or maybe
    even 3 orders of magnitude in security - remember that 98% of security bugs
    are The Same Dumb Things over and over - so simply not doing those dumb
    things gets you 2 orders of magnitude right there.

    Also, remember that there's some basic economics involved too - if you do
    a graph:

      |X . . O where 'X' is the costs (incident response, cleanup,
    C |X . . O lost sales, downtime, etc) of not being secure, and
    O | X .. .. O 'O' is the cost of actually deploying security (this
    S | X ..$.. O stuff *does* have real costs - ever had to get 30K
    T | XX OO users to change their password on a regular basis?)
      | XXX OOO The '.' line is the *sum* of those two, and will have
      |OOOOOOO XXXXXXX a minimum value somewhere - I've marked that with a
      +------------------ '$'. *THAT* is the correct level of security to have.
         SECURITY

    What you want is the *minimum total cost of security*. Now, for different
    applications, the 'X' and 'O' lines have different shapes - if you're securing
    nuclear launch codes, the 'X' is almost a horizontal (and very high) line -
    it's very expensive to get hacked no matter what your security is. It makes
    sense to spend a billion dollars to secure those. On the other hand, it
    *doesnt* make sense to spend even $200K (and that's not much in development
    terms - 2 man-years at best) to secure data that's only worth $2K. 

    -- 
				Valdis Kletnieks
				Computer Systems Senior Engineer
				Virginia Tech

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