Re: explanation and code for stream.c issues

From: Vladimir Dubrovin (vladat_private)
Date: Sat Jan 22 2000 - 03:14:29 PST

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    Hello Don Lewis,
    
    22.01.00 13:58, you wrote: explanation and code for stream.c issues;
    
    D> } Intruder sends SYN packet and then sends, lets say 1000 ACK packets to
    D> } the  same port from same port and source address. SYN packet will open
    D> } ipfilter  to  pass  all  others  packets.  This  attack  doesn't  need
    D> } randomization for each packet.
    
    D> Instead of producing RST responses, this will produce ACKs. Your earlier
    D> comment about this prompted my comment in another thread about the
    D> possible need to rate limit ACK packets.
    
    This  will  not  produce  ACK packets, if ACK send by intruder doesn't
    conform  sequence  number  in the SYN/ACK response of victim. Original
    stream.c used
    
        packet.tcp.th_ack           = 0;
    
    i changed to
    
        packet.tcp.th_ack = random();
        for ACK packets.
    
    But  it's  not  principial  - victim will reply RST for this packet in
    most cases.
    
    
      +=-=-=-=-=-=-=-=-=+
      |Vladimir Dubrovin|
      | Sandy Info, ISP |
      +=-=-=-=-=-=-=-=-=+
    



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