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fpf module and packet fragmentation:local/remote DoS.
From: "XR Agent" <prp_sc () antionline org>
Date: Sat, 2 Jun 2001 13:45:26 -0700

Fpf kernel module by |CyRaX| [cyrax () pkcrew org] (www.pkcrew.org) alters linux tcp/ip stack to emulate other OS'es 
against nmap/queso fingerprints using parser by FuSyS that reads nmap-os-fingerprints 
for os emulation choice.

However, attempts to send fragmented packets to local or remote machine with nmap (-sS -f, -sN -f, -sX -f, -sF -f, -sA 
-f) or hping (hping -f) using host with loaded fpf.o lead to kernel panic ("Aiee, killing interrupt handle. Kernel 
panic: Attempted to kill the idle task ! In interrupt handler - not syncing.") if run from console or force immediate 
reboot if the packet sending tool is run from an xterm. When fpf.o - running machine recieves nmap / hping fragmented 
packets from remote hosts system freezes.

Security through obscurity was never a pefect solution, but in the current case there is also a hefty price to pay: 
complete inability of tcp/ip stack of "obscured" machine to deal with packet fragmentation.

Tested on Slackware 7.1 kernel 2.2.16 (i386).

Regards,

      _clf3_                               (PrP_Sc () antionline org)
     
      Veneficio, ergo sum.



   



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