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Date:      Thu, 27 Jan 2000 12:56:56 -0500 (EST)
From:      Dug Song <dugsong@monkey.org>
To:        Michael Robinson <robinson@netrinsics.com>
Cc:        freebsd-security@freebsd.org
Subject:   Re: opinions on source quench
Message-ID:  <Pine.BSO.4.10.10001271240480.11540-100000@funky.monkey.org>
In-Reply-To: <200001271256.UAA28713@netrinsics.com>

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On Thu, 27 Jan 2000, Michael Robinson wrote:

> What is the prevailing opinion on accepting ICMP source quench?
> 
> Which is greater, the danger of a spoofed DoS attack, or the danger of
> overloading some hapless downstream network node?

to spoof ICMP source quenches correctly, an attacker must be able to sniff
your packets to quote them in the forged reply. but if they can do this,
they can just as easily forge correct TCP RSTs. see the tcpnice, tcpkill
programs from dsniff for sample code:

	http://www.monkey.org/~dugsong/dsniff/

TCP has its own congestion control, and i don't know of any applications
using UDP that honor source quenches. my guess is that it would probably
be safe to filter them, but YMMV.

-d.

---
http://www.monkey.org/~dugsong/



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