netdev - Re: [PATCH v2] add stealth mode

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Date:	Tue, 7 Jul 2015 17:27:27 +0200
From:	Matteo Croce <matteo@...nwrt.org>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] add stealth mode

2015-07-07 10:07 GMT+02:00 Hannes Frederic Sowa <hannes@...essinduktion.org>:
>
>
> On Mon, Jul 6, 2015, at 21:44, Matteo Croce wrote:
>> 2015-07-06 12:49 GMT+02:00  <Valdis.Kletnieks@...edu>:
>> > On Thu, 02 Jul 2015 10:56:01 +0200, Matteo Croce said:
>> >> Add option to disable any reply not related to a listening socket,
>> >> like RST/ACK for TCP and ICMP Port-Unreachable for UDP.
>> >> Also disables ICMP replies to echo request and timestamp.
>> >> The stealth mode can be enabled selectively for a single interface.
>> >
>> > A few notes.....
>> >
>> > 1) Do you have an actual use case where an iptables '-j DROP' isn't usable?
>>
>> If you mean using a default DROP policy and allowing only the traffic
>> do you want,
>> then the use case is where the port can change at runtime and you may not
>> want
>> to update the firewall every time
>
> Can't you use socket match in netfilter to accomplish exactly that?

You mean the owner --uid match?
Yes  sort of, but my was a different goal, I want just to disable any
kind of reply from a specific interface (usually WAN) unless there is
a listening socket, to mitigate port scanning and flood attacks
without having a firewall.

Obviously you can do it with a firewall,
but why do we have /proc/sys/net/ipv4/icmp_echo_ignore_all when we can
drop ICMP echoes?

-- 
Matteo Croce
OpenWrt Developer
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