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Date:      Sun, 6 Apr 2003 09:27:35 -0700
From:      Sereciya Kurdistani <>
Subject:   Re: Quick IPFW Question Concerning Sendmail
Message-ID:  <>
In-Reply-To: <>
References:  <> <> <> <>

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  Thank you for taking the time to respond to my posting ;)

  Your comments are greatly appreciated.

On Sun, Apr 06, 2003 at 06:18:05PM +0200, clemens fischer wrote:
> Sereciya Kurdistani <>:
> >   vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
> >   ipfw add NNNN check-state
> >   ipfw add NNNN allow      { udp or tcp } from any to any dst-port smtp,auth,smtps out via tun0 keep-state
> >   ipfw add NNNN allow  log   tcp          from any to any dst-port smtp,smtps      in  via tun0
> >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >        
> >   This way, you don't have to allow any ports open for any incoming traffic not matched
> >   by the stateful rules, ;)
> are you sure this does what you want?  i don't see the customary
> anti-spoofing rules and there's a lot to be said for keeping state
> especially on _incoming_ connections.  if these are all your rules,
> then what about incoming SMTP and AUTH on port 113?

  I think this is what I want...
  Would you please show me an example of anti-spoofing rules?  I'd
  greatly appreciate it ;)

  ...Actually, I do have some facility for anti-spoofing rules, here they are:

  ipfw add NNNN skipto NEXT_BLOCK all from     ${myhost} to not ${myhost} out via ${oif_1}
  ipfw add NNNN skipto NEXT_BLOCK all from not ${myhost} to     ${myhost} in  via ${oif_1}

  Do you mean I should check/filter for the private IP Addresses also?

  I'm not opening incoming AUTH because it seems unnecessary ; everything
  is running fine without opening that port.

  Incoming SMTP is handled with a rule like:

  ipfw add NNNN pipe N log tcp from any to any smtp,smtps in via ${oif}

> i imagine your rules allowing _you_ to query others for AUTH data,
> but you don't allow others this privilege.

  That's correct.  Am I breaking a netiquette rule that I may not be
  familiar with?

Thank you for your participation ;)
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