From nobody Wed Jun 12 22:05:39 2024 X-Original-To: freebsd-net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4W003Z6BjLz5NXx2 for ; Wed, 12 Jun 2024 22:05:46 +0000 (UTC) (envelope-from bsd-lists@bsdforge.com) Received: from udns.ultimatedns.net (udns.ultimatedns.net [24.113.41.81]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "ultimatedns.net", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4W003Z4Mcnz4S41; Wed, 12 Jun 2024 22:05:46 +0000 (UTC) (envelope-from bsd-lists@bsdforge.com) Authentication-Results: mx1.freebsd.org; none Received: from ultimatedns.net (localhost [127.0.0.1]) by udns.ultimatedns.net (8.16.1/8.16.1) with ESMTP id 45CM5esh018851; Wed, 12 Jun 2024 15:05:46 -0700 (PDT) (envelope-from bsd-lists@bsdforge.com) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=ultimatedns.net; s=mx99; t=1718229946; x=1718230546; r=y; bh=FaP2M6eO7bzOnrXkcNfpZG6k0oTzQ0Q/prS3hcASwbA=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=bLJh3RFTDWV0Dld8qzU6k/tSsAODledgv9GU1LPHM+3erRM+DsLvQHU4xHrf3rX+I kznIvOXh14SAmxvbNTKIHbPX4HKq0khdfnMmVtgAG217oa0QSoLJfhjyKhz8EEThR/ un6T4BlH9S1QqsRkhk6RrbzvlcKqs41IQUyEjdJV1vgZdVXrYRaBwufK5HRRbXb0M7 wqzPyxs77s1HRqRes0VESKlY7oJ+pehiFfrRdaW0QkGyWUgG6gmNGROTVBRxK4Ty4q gqt9gLQ4O7rZA4QmZ+lw0LAzuOKXYOABRLSGoNMjI1n56hS/oQzqwLVa4d/rw6wp79 D5ezbRYbtHSoQ== List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@FreeBSD.org MIME-Version: 1.0 Date: Wed, 12 Jun 2024 15:05:39 -0700 From: Chris To: "Rodney W. Grimes" Cc: Ed Maste , freebsd-net@freebsd.org Subject: Re: Discarding inbound ICMP REDIRECT by default In-Reply-To: <202406122147.45CLlsgN042313@gndrsh.dnsmgr.net> References: <202406122147.45CLlsgN042313@gndrsh.dnsmgr.net> User-Agent: UDNSMS/17.0 Message-ID: <72ceb2fe26812a237a17bd8de4024b7f@bsdforge.com> X-Sender: bsd-lists@bsdforge.com Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-Spamd-Bar: ---- X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:11404, ipnet:24.113.0.0/16, country:US] X-Rspamd-Queue-Id: 4W003Z4Mcnz4S41 On 2024-06-12 14:47, Rodney W. Grimes wrote: >> I propose that we start dropping inbound ICMP REDIRECTs by default, by >> setting the net.inet.icmp.drop_redirect sysctl to 1 by default (and >> changing the associated rc.conf machinery). I've opened a Phabricator >> review at https://reviews.freebsd.org/D45102. > > I propse that we NOT do this. If you need this to protect your end > node your probably doing something really unsafe network wise. The > place that ICMP REDIRECTS should be dropped, and is most places, is > at access routers and firewalls. > > Any one that needs this change to protect there network has larger > issues than an ICMP REDIECT causing some issues. > > ICMP redirectr are very usefull for not having to run routing > protocols on all your end nodes and allowing your edge/access > routers tell your internal hosts via redirects how to get to > places more efficiently. > >> >> ICMP REDIRECTs served a useful purpose in earlier networks, but on > They still serve this very usefull purpose. > >> balance are more likely to represent a security issue today than to >> provide a routing benefit. With the change in review it is of course >> still possible to enable them if desired for a given installation. >> This change would appear in FreeBSD 15.0 and would not be MFC'd. >> >> One question raised in the review is about switching the default to >> YES but keeping the special handling for "auto" (dropping ICMP >> REDIRECT if a routing daemon is in use, honouring them if not). I >> don't think this is particularly valuable given that auto was >> introduced to override the default NO when necessary; there's no need >> for it with the default being YES. That functionality could be >> maintained if there is a compelling use case, though. > > The policy that is there now is exactly how things should be configured > for a host in a network protected by a proper router w/firewall. > The existing "auto" does exactly the right thing. > >> >> If you have any questions or feedback please follow up here or in the >> review. As Rodeney already effectively explains; dropping packets makes routing, and discovery exceedingly difficult. Which is NOT what the average user wants, or expects. I use "set block-policy drop" in pf(4). But as already noted, this is for "filtering" purposes. Your suggestion also has the negative affect of hanging remote ports. Which can result in other negative results by peers. Please don't. :) >> >> --Chris