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From: Kyle Sparger (kspargerDIALTONEINTERNET.NET)
Date: Mon Mar 05 2001 - 17:03:04 CST

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    Woody said:
    > Known Not Vulnerable:
    > Linux - RH6.2 stock kernel

    This information is incorrect; Linux does 'suffer' from this in at least
    version 2.2. I believe it also 'suffers' from this in 2.4. It's easy
    enough to replicate. For example, on ethernet, just assign a static
    MAC address for the IP in question for the server in question, and you'll
    get access to the appropriate interface.

    Elias Levy said:
    > Its obvious that host that implement the Weak ES model are the ones
    > vulnerable, while hosts that implement the Strong ES model are not.

    I had a similar discussion with the maintainers of the Linux stack a few
    months ago. The following quotes (both from Andi Kleen, a listed
    maintainer) apply here:

    "You're describing the Strong ES model (see 3.3.4.2). Linux 2.2 follows
    the weak ES model."

    "There are already enough mechanisms to enforce a stronger model if
    needed: reject routes, firewall rules, routing filter, arpfilter."

    -------------------------------------------------------------------------

    Ultimately, the 'expected' behaviour depends on how you view the addresses
    on the machine -- Are they system wide, or are they per-interface? -- and
    therein lies the debate of weak v. strong.

    Given that on UNIX-like systems one generally assigns an address to an
    interface (via ifconfig), IMO the 'expected' behaviour is that the strong
    model is what is implemented. The implication is certainly there.

    Thanks,

    Kyle Sparger - Senior System Administrator
    kspargerdialtoneinternet.net - http://www.dialtoneinternet.net
    Voice - (954) 581-0097 x 122
    "Forget college, I'm going pro."