From: Florian Westphal <fw@strlen.de>
To: Fatih USTA <fatihusta86@gmail.com>
Cc: netfilter@vger.kernel.org
Subject: Re: TCP 4 way handshake or TCP Split Handshake Attack
Date: Fri, 24 Jan 2020 17:24:17 +0100 [thread overview]
Message-ID: <20200124162417.GW795@breakpoint.cc> (raw)
In-Reply-To: <33c1b81b-cb3d-e277-334f-5a8daaf8dd73@gmail.com>
Fatih USTA <fatihusta86@gmail.com> wrote:
> Hello,
> I am trying to protect my network from the tcp split handshake attack!
> (4-way handshake rejection or 3-way handshake enforcement).
> I tested the sample code. (link below) And passed the firewall(iptables).
Why wouldn't it? Its valid tcp, your ruleset allows connections to happen
and there is a socket expecting a connection.
> I can't find any solution on the internet for Linux.
nft add rule filter forward tcp flags & (syn | ack) == syn ct direction reply counter drop
But why would you want to disallow this behaviour?
> Link1: https://tech.labs.oliverwyman.com/blog/2016/11/07/4-way-tcp-handshake-and-firewalls/
This is simultaneous connect, at least thats what can be seen in the
tcpdump, syns cross on wire, both ends send syn/ack. WHy do you
consider this an "attack"?
next prev parent reply other threads:[~2020-01-24 16:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-24 14:26 TCP 4 way handshake or TCP Split Handshake Attack Fatih USTA
2020-01-24 16:24 ` Florian Westphal [this message]
2020-01-24 19:54 ` Fatih USTA
[not found] ` <CAN_K0LR36AZRc55aisesAU0xDrcEgw6e41zwzwHV=zSSOffVAQ@mail.gmail.com>
2020-01-24 23:48 ` Florian Westphal
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