[13509] in bugtraq
Re: explanation and code for stream.c issues
daemon@ATHENA.MIT.EDU (Vladimir Dubrovin)
Sun Jan 23 18:57:45 2000
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Message-Id: <1593.000122@sandy.ru>
Date: Sat, 22 Jan 2000 14:14:29 +0300
Reply-To: Vladimir Dubrovin <vlad@sandy.ru>
From: Vladimir Dubrovin <vlad@SANDY.RU>
X-To: Don Lewis <Don.Lewis@tsc.tdk.com>
To: BUGTRAQ@SECURITYFOCUS.COM
In-Reply-To: <200001221058.CAA16745@salsa.gv.tsc.tdk.com>
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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