Date: Wed, 21 Apr 2004 06:47:20 -0500 From: "Jacques A. Vidrine" <nectar@FreeBSD.org> To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@des.no> Cc: freebsd-security@freebsd.org Subject: Re: TCP RST attack Message-ID: <20040421114720.GD19738@lum.celabo.org> In-Reply-To: <xzphdve35oa.fsf@dwp.des.no> References: <6.0.3.0.0.20040420125557.06b10d48@209.112.4.2> <xzphdve35oa.fsf@dwp.des.no>
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On Tue, Apr 20, 2004 at 07:44:37PM +0200, Dag-Erling Sm=F8rgrav wrote: > Mike Tancsa <mike@sentex.net> writes: > > http://www.uniras.gov.uk/vuls/2004/236929/index.htm >=20 > The advisory grossly exaggerates the impact and severity of this > fea^H^H^Hbug. The attack is only practical if you already know the > details of the TCP connection you are trying to attack, or are in a > position to sniff it. =20 Well, the whole point is that *although in the past it was widely believed otherwise*, this attack is practical today in some real world situations. It many cases the only unknown is the source port number, and even that can be predictable. [...] > I don't believe BGP sessions are as exposed as the advisory claims > they are, either. The possibility of insertion attacks (which are > quite hard) was predicted six years ago, when RFC 2385 (Protection of > BGP Sessions via the TCP MD5 Signature Option) was written. RST > attacks may cause route flapping, but that can be avoided with a short > hysteresis (though this may be impractical for backbone routers) If the DoS attack causes route flapping, then the attack is a success. > Insertion attacks against SSL connections are practically impossible, > so the only risk there is an RST attack, which most browsers should > handle gracefully. >=20 > DNS connections (even zone transfers) are so short-lived that you > would have to be very, very lucky to pull off an insertion or RST > attack against. Yes, these seem to be stretches. > The most likely attack scenario to come out of this is probably gamers > and IRC weenies kicking eachother off servers (the server's IP address > and port number are known, the servers often reveal client IP > addresses to other clients, and the client often uses a fixed source > port, or one from a relatively small range) Every time someone is kicked off an IRC server (or otherwise restrained from online chat), global productivity rises :-) Cheers, --=20 Jacques Vidrine / nectar@celabo.org / jvidrine@verio.net / nectar@freebsd= .org
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