Re: explanation and code for stream.c issues

[vlad () SANDY RU (Vladimir Dubrovin)]

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.

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  |Vladimir Dubrovin|
  | Sandy Info, ISP |
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