Re: iptables

From: Parker Morse (morse_at_sinauer.com)
Date: 09/29/03

  • Next message: hanfamily_at_earthlink.net: "used 7.3 updates with 7.3" 
    To: rrosa@usp.br
Date: Mon, 29 Sep 2003 13:45:52 -0400

    On Monday, Sep 29, 2003, at 07:12 US/Eastern, rrosa@usp.br wrote:
    > My script is ok now! You are right : I need to accept connection FROM
    > port. But
    > I needed the udp rules to samba because without the liberantion samba
    > udp, it
    > didn't work.
    >
    > Only another question, if I put ACCEPT in OUTPUT, don't make sense if
    > I put:
    > iptables -t filter -A OUTPUT -p tcp --dport 515 -j ACCEPT
    > to only accept the output to the printer port?? And here I had to put
    > ...OUTPUT
    > -p tcp --source-port 515 -j ACCEPT ??? And I have to accept the output
    > to my
    > ssh, ok?

    I'm not the best person to be asking about firewalls, but:

    I think you're confused about the way OUTPUT works. It acts on any
    packets sent out by your system. Unless you are concerned about how
    users of your system are going to be using it, you're creating more
    problems than you're solving by having too many rules on OUTPUT. Unlike
    INPUT, where you don't know what's coming in from outside, you're
    better off with a permissive policy (only blocking ports which cause
    trouble, instead of only opening ports you need) on OUTPUT.

    Someone PLEASE correct me if I've got this wrong.

    See <http://www.tldp.org/HOWTO/Firewall-HOWTO.html> and
    <http://www.tldp.org/HOWTO/IPCHAINS-HOWTO.html> for more information.

    pjm 

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