Re: Preventing exploitation with rebasing

From: Seth Breidbart (sethbat_private)
Date: Wed Feb 05 2003 - 16:07:15 PST

  • Next message: Fred Cohen: "Preventing exploitation with rebasing"

    In theory, it's easy to prove that some programs cannot be relocated,
    period.  Anybody who has been programming long enough has seen people
    re-use a memory location as both an address and a constant in order to
    keep the program small enough (12k OK; 12k + 2 bytes really bad
    news).  That can't be relocated.
    
    Even under the assumption that locations aren't re-used, it's provably
    impossible (Turing-complete) to determine whether the contents of a
    location can be used as an address by a program.
    
    That said, _if_ a program is relocatable, relocating it would seem to
    be an easy way to gain some security.  Whether that's worth the cost
    (in fragility and undebuggability) is another question.
    
    Seth
    



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