From nobody Thu Jun 13 13:39:13 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 4W0Nml55CLz5NhKW for ; Thu, 13 Jun 2024 13:39:19 +0000 (UTC) (envelope-from freebsd-rwg@gndrsh.dnsmgr.net) Received: from gndrsh.dnsmgr.net (pdx.rh.CN85.dnsmgr.net [65.75.216.6]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4W0Nmk6PH6z47Xs; Thu, 13 Jun 2024 13:39:18 +0000 (UTC) (envelope-from freebsd-rwg@gndrsh.dnsmgr.net) Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=pass (policy=none) header.from=gndrsh.dnsmgr.net; spf=pass (mx1.freebsd.org: domain of freebsd-rwg@gndrsh.dnsmgr.net designates 65.75.216.6 as permitted sender) smtp.mailfrom=freebsd-rwg@gndrsh.dnsmgr.net Received: from gndrsh.dnsmgr.net (localhost [127.0.0.1]) by gndrsh.dnsmgr.net (8.13.3/8.13.3) with ESMTP id 45DDdD8D044780; Thu, 13 Jun 2024 06:39:13 -0700 (PDT) (envelope-from freebsd-rwg@gndrsh.dnsmgr.net) Received: (from freebsd-rwg@localhost) by gndrsh.dnsmgr.net (8.13.3/8.13.3/Submit) id 45DDdDma044779; Thu, 13 Jun 2024 06:39:13 -0700 (PDT) (envelope-from freebsd-rwg) From: "Rodney W. Grimes" Message-Id: <202406131339.45DDdDma044779@gndrsh.dnsmgr.net> Subject: Re: Discarding inbound ICMP REDIRECT by default In-Reply-To: To: Ed Maste Date: Thu, 13 Jun 2024 06:39:13 -0700 (PDT) CC: freebsd-net@FreeBSD.org X-Mailer: ELM [version 2.4ME+ PL121h (25)] 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 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-Spamd-Bar: --- X-Spamd-Result: default: False [-3.69 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.89)[-0.893]; DMARC_POLICY_ALLOW(-0.50)[gndrsh.dnsmgr.net,none]; R_SPF_ALLOW(-0.20)[+ip4:65.75.216.0/23]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; ASN(0.00)[asn:10494, ipnet:65.75.216.0/23, country:US]; RCPT_COUNT_TWO(0.00)[2]; MID_RHS_MATCH_FROM(0.00)[]; R_DKIM_NA(0.00)[]; MLMMJ_DEST(0.00)[freebsd-net@FreeBSD.org]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_LAST(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_TRACE(0.00)[0:+] X-Rspamd-Queue-Id: 4W0Nmk6PH6z47Xs > 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. > > ICMP REDIRECTs served a useful purpose in earlier networks, but on > 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. > > If you have any questions or feedback please follow up here or in the review. Discarding ICMP redirects on a internet host is non-conformant with STD-3 via rfc-1122. Processing of ICMP rediects is a MUST for hosts. -- Rod Grimes rgrimes@freebsd.org