From: Eric Garver <eric@garver.life>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org, Phil Sutter <phil@nwl.cc>
Subject: Re: [PATCH nf] netfilter: nat: force port remap to prevent shadowing well-known ports
Date: Mon, 29 Nov 2021 15:22:26 -0500 [thread overview]
Message-ID: <YaU2gndowxjvV+zn@egarver.remote.csb> (raw)
In-Reply-To: <20211129144218.2677-1-fw@strlen.de>
On Mon, Nov 29, 2021 at 03:42:18PM +0100, Florian Westphal wrote:
> If destination port is above 32k and source port below 16k
> assume this might cause 'port shadowing' where a 'new' inbound
> connection matches an existing one, e.g.
How did you arrive at 16k?
>
> inbound X:41234 -> Y:53 matches existing conntrack entry
> Z:53 -> X:4123, where Z got natted to X.
>
> In this case, new packet is natted to Z:53 which is likely
> unwanted.
>
> We could avoid the rewrite for connections that are not being forwarded,
> but get_unique_tuple() and the callers don't propagate the required hook
> information for this.
>
> Also adjust test case.
>
> Cc: Eric Garver <eric@garver.life>
> Cc: Phil Sutter <phil@nwl.cc>
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
[..]
next prev parent reply other threads:[~2021-11-29 20:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-29 14:42 [PATCH nf] netfilter: nat: force port remap to prevent shadowing well-known ports Florian Westphal
2021-11-29 20:22 ` Eric Garver [this message]
2021-11-29 22:02 ` Florian Westphal
2021-11-30 14:34 ` Eric Garver
2021-12-08 0:28 ` Pablo Neira Ayuso
2021-12-08 10:47 ` Florian Westphal
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