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Date:      Sat, 14 Sep 2002 20:25:01 +0300
From:      Peter Pentchev <roam@ringlet.net>
To:        Alan E <alane@geeksrus.net>
Cc:        Edwin Groothuis <edwin@mavetju.org>, freebsd-ports@FreeBSD.ORG
Subject:   Re: bash2
Message-ID:  <20020914172501.GB379@straylight.oblivion.bg>
In-Reply-To: <20020914135955.GA50972@wwweasel.geeksrus.net>
References:  <20020912043831.GB69776@k7.mavetju> <200209132223.g8DMNt1a027966@dt.home> <20020914015417.GA1692@gforce.johnson.home> <20020914100207.GA87001@wwweasel.geeksrus.net> <20020914134752.GD69776@k7.mavetju> <20020914135955.GA50972@wwweasel.geeksrus.net>

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On Sat, Sep 14, 2002 at 09:59:55AM -0400, Alan E wrote:
> On Sat, Sep 14, 2002 at 11:47:52PM +1000, Edwin Groothuis wrote:
> >On Sat, Sep 14, 2002 at 06:02:07AM -0400, Alan E wrote:
> >> On Fri, Sep 13, 2002 at 08:54:17PM -0500, Glenn Johnson wrote:
> >> >On Sat, Sep 14, 2002 at 08:23:55AM +1000, Tony Maher wrote:
> >> >> > > Is anyone able to build bash2?  I have not been able to retrieve
> >> >> > > the bash205b-003 patch file for several days.
> >> >>
> >> >> I also could not connect but have traced this to the fact that
> >> >> ftp.cwru.edu tries to used ident.
> >> >>=20
> >> >> Adding 'reset log logamount 100 tcp from any to any 113 in recv rl0'
> >> >> to my firewall rules and I can now get the patches.
> >> >
> >>=20
> >> I think it's an unfair imposition to require a security configurtion
> >> change in my firewall to build a port. Could these patches be also
> >> hosted on a freebsd.org machine?
> >
> >If _your_ host doesn't follow the normal rules of the IP network
> >(i.e. if you send a packet to a port which doesn't have a service
> >bound to it, you send a TCP reset packet) and something goes wrong
> >because of it, it is _you_ who has a problem, not the other side.
>=20
> It's this FBSD 4.7-PRE box, and the ident port is not allowed thruogh
> the ipfw firewall. That's all. I guess FreeBSD has a problem, huh?

This is an issue that comes up often on security-related lists.  Many
people think that unless your server is already under attack or under a
very high normal traffic load, the normal way to 'not allow' an incoming
TCP SYN packet is to send back a RST, not just to drop it on the floor.
This - a 'reset' rule as opposed to a 'deny' rule - lets the peer know
that, yes, you are aware that somebody might attempt connections to this
service, and no, you do not allow them to.  Dropping the SYN packet and
letting the incoming connection time out is generally not considered
friendly neighborhood netizen behavior :)

Of course, if you are under attack, or you have a serious premonition
that you may come to be under attack soon, or if the usual traffic over
your wire stretches the bandwidth almost to its limits, then dropping
incoming connection packets may be a very sensible policy.  However, it
is my personal opinion that for the general case, a 'reset' rule is much
more useful to both you and the Internet as a whole :)

G'luck,
Peter

--=20
Peter Pentchev	roam@ringlet.net	roam@FreeBSD.org
PGP key:	http://people.FreeBSD.org/~roam/roam.key.asc
Key fingerprint	FDBA FD79 C26F 3C51 C95E  DF9E ED18 B68D 1619 4553
Do you think anybody has ever had *precisely this thought* before?

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