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    SubjectRe: Stopping buffer-overflow security exploits using page protection
    On Sat, 29 Jul 2000, Gary Funck wrote:

    > Oxy, excellent summary of the issues relating to the prevention
    > of exploits, thanks.
    >
    > > The problem isn't Intel's fault or any OS's, it's a problem in the C
    > > language and compiler. There are 5 fixes:
    > >
    > > a) write safe code (which has so far proved hard)
    > > b) compile with bounds-checking (big performance hit)
    >
    > What is the level of performance hit, using bounds-checking?

    Depends very much on the application. Can be 100% or more. It's actually
    probably more of a hit than rewriting something in eg Perl or Python, as
    those languages are designed around bounded arrays where in C it's an
    afterthought. Oh, and in C, there's the whole issue of pointer aliasing
    which means it's only a partial fix.

    (C is a stupid language to write large applications in. The vast majority
    of bugs in C programs simply don't exist in newer languages. For most of
    the things people use computers for today, it's much more important that
    something works well than that it work fast.)

    > > c) compile with StackGuard, etc. (doesn't stop exploits that corrupt
    > > other locals)
    > > d) separate the return address stack from the automatic variable stack
    > > (ditto)
    > > e) use another language (performance)
    >
    > Might there also be an 'alternate universe' where the damage caused
    > by exploit-induced loss of control could be reduced/limited?

    Capabilities are a start. But this is an orthogonal problem. If someone
    hacks just my account rather than root, to me it's just as bad, no?

    --
    "Love the dolphins," she advised him. "Write by W.A.S.T.E.."


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