From owner-freebsd-security Tue Aug 22 21: 2:48 2000 Delivered-To: freebsd-security@freebsd.org Received: from mailhost01.reflexnet.net (mailhost01.reflexnet.net [64.6.192.82]) by hub.freebsd.org (Postfix) with ESMTP id 7570B37B423 for ; Tue, 22 Aug 2000 21:02:41 -0700 (PDT) Received: from 149.211.6.64.reflexcom.com ([64.6.211.149]) by mailhost01.reflexnet.net with Microsoft SMTPSVC(5.5.1877.197.19); Tue, 22 Aug 2000 21:01:31 -0700 Received: (from cjc@localhost) by 149.211.6.64.reflexcom.com (8.9.3/8.9.3) id VAA46337; Tue, 22 Aug 2000 21:02:36 -0700 (PDT) (envelope-from cjc) Date: Tue, 22 Aug 2000 21:02:36 -0700 From: "Crist J . Clark" To: Lowell Gilbert Cc: freebsd-security@FreeBSD.ORG Subject: Re: icmptypes Message-ID: <20000822210236.G28027@149.211.6.64.reflexcom.com> Reply-To: cjclark@alum.mit.edu References: <20000821180351.H57333@jade.chc-chimes.com> <20000821181825.I57333@jade.chc-chimes.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0i In-Reply-To: ; from lowell@world.std.com on Tue, Aug 22, 2000 at 11:17:25AM -0400 Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Tue, Aug 22, 2000 at 11:17:25AM -0400, Lowell Gilbert wrote: > billf@chimesnet.com (Bill Fumerola) writes: > > > On Mon, Aug 21, 2000 at 03:16:03PM -0700, Rodney W. Grimes wrote: > > > > > > example from memory: > > > > # ipfw add unreach filter-prohib icmp from any to any icmptypes 0,8 > > > > > > The 8 case would be okay, but returning an icmp unreach for an icmp echo > > > reply would be a violation of the protocol spec. I would recomend > > > against it. > > > > Yes, unreaching 0 would be nonsense I suppose. > > > > On a side note, RFC and protocol blah blah is nice, but sometimes you > > just have to drop packets and break spec if the machine is a target. > > Dropping packets is never a violation of the protocol spec. Returning > ICMP "unreachable" errors in response to other ICMP packets would be. > This is an important distinction. [It's also what Rodney Grimes > actually said.] Actually, generating an error message in response to an error message violates the RFCs. An error response to a non-error reporting ICMP message is OK... but dropping is OK too. See section 3.2.2 of RFC1122. RFC1122 is one of the most useful ones, I encourage everyone to have a look there when questions like this pop up. -- Crist J. Clark cjclark@alum.mit.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message