DoS: ANS Interlock Firewall

From: Chris A. Henesy (lurkerat_private)
Date: Thu Jul 09 1998 - 12:51:14 PDT

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            This may be repeated information but a quick search of the
    archives didn't turn anything up, so here goes...
    
            There is a problem in the TCP/IP stack of ANS's Interlock Internet
    Firewall product.  Sending the correct series of packet fragments will
    cause the machine to reboot.  Bellow is part of a problem description
    provided by ANS.  A patch is available.
    
    >The 1st fragment contains all (or most) of the packets payload and it
    >incorrectly indicates that no other fragments are coming (the IP
    >more fragment field is not set).  The next fragment is sent with a
    >zero length and uses the same packet identifier (indicating its
    >another part of the earlier packet).  This packet also does not
    >indicate that more fragments are coming.  The result is a zero length
    >fragment arrives at the InterLock and gets processed by the Solaris
    >fragment handling code.  Unfortunately, the Solaris fragment timeout
    >handling code (which gets involved 60 seconds later) doesnt properly
    >handle the zero length fragment and its panics the box during cleanup.
    
            -The Lurker
    



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