From owner-freebsd-questions@FreeBSD.ORG Wed Aug 26 13:30:26 2009 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2A70B106568F for ; Wed, 26 Aug 2009 13:30:26 +0000 (UTC) (envelope-from wmoran@potentialtech.com) Received: from mail.potentialtech.com (internet.potentialtech.com [66.167.251.6]) by mx1.freebsd.org (Postfix) with ESMTP id D0A148FC14 for ; Wed, 26 Aug 2009 13:30:25 +0000 (UTC) Received: from localhost (pr40.pitbpa0.pub.collaborativefusion.com [206.210.89.202]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.potentialtech.com (Postfix) with ESMTPSA id 9564BEBC0A; Wed, 26 Aug 2009 09:30:24 -0400 (EDT) Date: Wed, 26 Aug 2009 09:30:23 -0400 From: Bill Moran To: Adam Vande More Message-Id: <20090826093023.e46f6175.wmoran@potentialtech.com> In-Reply-To: <6201873e0908260620u22eaf1acl3879cc1c77a232b8@mail.gmail.com> References: <4A924601.3000507@lim.nl> <25134277.post@talk.nabble.com> <20090825120504.93a7c51d.wmoran@potentialtech.com> <6201873e0908250921w46000c2by78893a1c5b581e78@mail.gmail.com> <20090825130616.20ab0049.wmoran@potentialtech.com> <6201873e0908251237n5c819d9ag36f867b5e68e258c@mail.gmail.com> <20090825154358.7c792d3a.wmoran@potentialtech.com> <6201873e0908251511q643f3662nc73f264cbfcfe645@mail.gmail.com> <20090826081123.0a06b1c8.wmoran@potentialtech.com> <6201873e0908260620u22eaf1acl3879cc1c77a232b8@mail.gmail.com> Organization: Bill Moran X-Mailer: Sylpheed 2.7.1 (GTK+ 2.16.5; i386-portbld-freebsd7.2) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Paul Schmehl , freebsd-questions@freebsd.org, Colin Brace Subject: Re: what www perl script is running? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Aug 2009 13:30:26 -0000 In response to Adam Vande More : > On Wed, Aug 26, 2009 at 7:11 AM, Bill Moran wrote: > > > Adam Vande More wrote: > > > > > > On Tue, Aug 25, 2009 at 2:43 PM, Bill Moran > >wrote: > > > > > > > In response to Adam Vande More : > > > > > > > > > On Tue, Aug 25, 2009 at 12:06 PM, Bill Moran < > > wmoran@potentialtech.com > > > > >wrote: > > > > > > > > > > > In response to Adam Vande More : > > > > > > > > > > > > > On Tue, Aug 25, 2009 at 11:05 AM, Bill Moran < > > > > wmoran@potentialtech.com > > > > > > >wrote: > > > > > > > > > > > > > > > In response to Paul Schmehl : > > > > > > > > > > > > > > > > > --On Tuesday, August 25, 2009 08:30:17 -0500 Colin Brace < > > > > cb@lim.nl> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Bill Moran wrote: > > > > > > > > > >> > > > > > > > > > >> You can add an ipfw rule to prevent the script from > > calling > > > > home, > > > > > > > > which > > > > > > > > > >> will effectively render it neutered until you can track > > down > > > > and > > > > > > > > actually > > > > > > > > > >> _fix_ the problem. > > > > > > > > > > > > > > > > > > > > Mike Bristow above wrote: "The script is talking to > > > > 94.102.51.57 on > > > > > > > > port > > > > > > > > > > 7000". OK, so I how do I know what port the script is using > > for > > > > > > > > outgoing > > > > > > > > > > traffic on MY box? 7000 is the remote host port, right? > > > > > > > > > > > > > > > > > > > > FWIW, here are my core PF lines: > > > > > > > > > > > > > > > > > > > > pass out quick on $ext_if proto 41 > > > > > > > > > > pass out quick on gif0 inet6 > > > > > > > > > > pass in quick on gif0 inet6 proto icmp6 > > > > > > > > > > block in log > > > > > > > > > > > > > > > > > > > > That is to say: nothing is allowed in unless explicitly > > allowed > > > > > > > > > > Everything allowed out. > > > > > > > > > > (plus some ipv6 stuff I was testing with a tunnel) > > > > > > > > > > > > > > > > > > > > > > > > > > > > The problem with blocking outbound ports is that it breaks > > things > > > > in > > > > > > odd > > > > > > > > ways. > > > > > > > > > For example, your mail server listens on port 25 (and > > possibly > > > > 465 as > > > > > > > > well) but > > > > > > > > > it communicates with connecting clients on whatever ethereal > > port > > > > the > > > > > > > > client > > > > > > > > > decided to use. If the port the client selects happens to be > > in > > > > a > > > > > > range > > > > > > > > that > > > > > > > > > you are blocking, communication will be impossible and the > > client > > > > > > will > > > > > > > > report > > > > > > > > > that your mail server is non-responsive. > > > > > > > > > > > > > > > > You're doing it wrong. Block on the destination port _only_ > > and > > > > you > > > > > > don't > > > > > > > > care about the ephemeral ports. > > > > > > > > > > > > > > What ports would you block then when you're trying to run a > > > > webserver? > > > > > > > > > > > > My point (which is presented in examples below) is that you block > > > > > > everything > > > > > > and only allow what is needed (usually only dns and ntp, possibly > > smtp > > > > if > > > > > > the web server needs to send mail) > > > > > > > > > > > > That single statement above was directed specifically at the > > comment > > > > about > > > > > > it being impossible to predict (and thus block) ephemeral source > > ports. > > > > > > He's > > > > > > right about that, and that's why filtering on the destination port > > is > > > > the > > > > > > more common practice. > > > > > > > > > > > > Of course, that caused me to create an email that seems to > > contradict > > > > > > itself, if you don't notice that it's two answers to two different > > > > > > comments. > > > > > > > > > > My point was that it's unfeasible to block by destination point. You > > can > > > > > only block by destination port if it's a known quantity, and the > > > > destination > > > > > port is ephemeral in the question I posed(which what the OP had an > > issue > > > > > with). > > > > > > > > Please read the entire email before you respond. My last example below > > > > demonstrates how to do what you call "unfeasible". > > > > > > > > > > > > > It's much easier to block outgoing ports for services you > > *don't* > > > > > > want to > > > > > > > > > offer, but, if the service isn't running anyway, blocking the > > > > port is > > > > > > > > > non-productive. > > > > > > > > > > > > > > > > You're obviously misunderstanding me completely. Your not > > blocking > > > > > > > > incoming > > > > > > > > connections, your preventing outgoing ones, which means there > > _is_ > > > > no > > > > > > > > service running on your local machine. > > > > > > > > > > > > > > > > For example, a server that is _only_ web (with SSH for admin) > > could > > > > > > have > > > > > > > > a ruleset like: > > > > > > > > > > > > > > > > pass in quick on $ext_if proto tcp from any to me port > > > > {25,587,465,22} > > > > > > keep > > > > > > > > state > > > > > > > > pass out quick on $ext_if proto tcp from me to any port {25} > > keep > > > > state > > > > > > > > pass out quick on $ext_if proto upd from me to any port > > {53,123} > > > > keep > > > > > > state > > > > > > > > block all > > > > > > > > > > > > > > > > (note that's only an example, there may be some fine points I'm > > > > > > missing) > > > > > > > > > > > > > > > > One thing that had not yet been mentioned when I posted my > > earlier > > > > > > comment, > > > > > > > > is that this system is a combination firewall/web server. That > > > > makes > > > > > > the > > > > > > > > rules more complicated, but the setup is still possible: > > > > > > > > > > > > > > > > pass in quick on $ext_if proto tcp from any to me port {80} > > keep > > > > state > > > > > > > > pass out quick on $ext_if proto upd from me to any port > > {53,123} > > > > keep > > > > > > state > > > > > > > > pass out quick on $ext_if from $internal_network to any all > > keep > > > > state > > > > > > > > block all > > > > > > > > > > > > > > > > Which allows limited outgoing traffic originating from the box > > > > itself, > > > > > > > > but allows unlimited outgoing traffic from systems on > > > > > > $internal_network. > > > > > > > > > > > > > > > > I've done this with great success. In fact, I had a fun time > > where > > > > a > > > > > > > > client in question was infected with viruses out the wazoo, but > > the > > > > > > > > viruses never spread off their local network because I only > > allowed > > > > > > > > SMTP traffic to their SMTP relay, which required SMTP auth > > (thus > > > > the > > > > > > > > viruses couldn't send mail) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > Adam Vande More > > > > > > > _______________________________________________ > > > > > > > freebsd-questions@freebsd.org mailing list > > > > > > > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > > > > > > > To unsubscribe, send any mail to " > > > > > > freebsd-questions-unsubscribe@freebsd.org" > > > > > > > > > > > > > > > > > > -- > > > > > > Bill Moran > > > > > > http://www.potentialtech.com > > > > > > http://people.collaborativefusion.com/~wmoran/ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > Adam Vande More > > > > > > > You said block by destination port. What you presented is not this, > > > although it gives give a functional environment of it. Sorry for the > > > pedantic pursuit here, but IMO terminology is important here. > > > > Both of my examples are filtering based on destination port. In reviewing > > this thread, you make the statement "destination ports are ephemeral" which > > is wrong. I can only assume that your understanding of IP port usage is > > wrong or incomplete. > > > > blocking destination port != keep state Why not? Because you said so? > and destination port are certainly ephemeral simply depends on pov. Your > original statement indicated blocking by port at egress was the way to go. > Your example did no such thing, it tracked state which is completely > different from both a functional and technical standpoint. This paragraph serves to further convince me that you are getting concepts confused. I see no reason for me to continue discussing this. -- Bill Moran http://www.potentialtech.com http://people.collaborativefusion.com/~wmoran/