From: Stephen Hemminger <stephen@networkplumber•org>
To: Kees Cook <keescook@chromium•org>
Cc: linux-kernel@vger•kernel.org, Rob Landley <rob@landley•net>,
"David S. Miller" <davem@davemloft•net>,
Alexey Kuznetsov <kuznet@ms2•inr.ac.ru>,
James Morris <jmorris@namei•org>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6•org>,
Patrick McHardy <kaber@trash•net>,
Eric Dumazet <edumazet@google•com>,
Neil Horman <nhorman@tuxdriver•com>,
Yuchung Cheng <ycheng@google•com>,
Shan Wei <davidshan@tencent•com>,
linux-doc@vger•kernel.org, netdev@vger•kernel.org,
Willy Tarreau <w@1wt•eu>
Subject: Re: [PATCH] tcp: sysctl to disable TCP simultaneous connect
Date: Thu, 7 Feb 2013 10:39:50 -0800 [thread overview]
Message-ID: <20130207103950.662698ea@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <20130207175240.GA12520@www.outflux.net>
On Thu, 7 Feb 2013 09:52:40 -0800
Kees Cook <keescook@chromium•org> wrote:
> This is based on Willy Tarreau's patch from 2008[1]. The goal is to
> close a corner-case of TCP that isn't used and poses a small DoS risk.
> For systems that do not want to take any risk at all, this is a desirable
> configuration knob.
>
> It is possible for two clients to connect with crossed SYNs without
> checking sequence numbers. As such, it might be possible to guess a source
> port number to block a system from making connections to well-known
> ports and IP addresses (e.g. auto-update checks) without requiring a
> MiTM position.
>
This patch probably also breaks TCP STUNT that is used by some applications for NAT
traversal.
next prev parent reply other threads:[~2013-02-07 18:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-07 17:52 [PATCH] tcp: sysctl to disable TCP simultaneous connect Kees Cook
2013-02-07 18:15 ` David Miller
2013-02-07 18:39 ` Stephen Hemminger [this message]
2013-02-07 18:44 ` Kees Cook
2013-02-07 19:29 ` H. Peter Anvin
2013-02-07 19:29 ` David Miller
2013-02-15 5:30 ` Eric W. Biederman
2013-02-15 6:41 ` Kees Cook
2013-02-15 7:10 ` Eric W. Biederman
2013-02-15 7:55 ` Willy Tarreau
2013-02-15 10:31 ` Eric W. Biederman
2013-02-15 10:47 ` Willy Tarreau
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