[NTLUG:Discuss] ftp problems through firewall

Alton R. Pouncey, II alton at trainers-r-us.com
Fri Mar 1 17:30:50 CST 2002 

ftp -p <fqdn or ip address>

On Thu, 2002-02-28 at 21:49, Raymond Norton wrote:
> I'm new. How would I force ftp to run in passive mode?
> 
> 
> > Try allowing port 20 through the firewall in addition to 21.  If that
> > does not work, try running ftp in passive mode.
> >
> > On Thu, 2002-02-28 at 20:59, Raymond Norton wrote:
> >> I have an iptable script running on my RedHat 7.1 box. It works great
> >> running my laptop through it for everything except when I try to
> >> access ftp servers on the outside. I am able to connect, but I cannot
> >> issue any commands with out getting an error: "Cannot connect to
> >> (outside
> >> interface):1294"
> >>
> >> Any ideas how to resolve this? I have attached the script as I run it.
> >> --
> >> Raymond Norton
> >> Little Crow Telemedia Network
> >> 320-234-0270
> >>
> >> ----
> >>
> >
> >> #!/bin/sh
> >> #
> >> # rc.firewall - Initial SIMPLE IP Firewall script for Linux 2.4.x and
> >> iptables #
> >> # Copyright (C) 2001  Oskar Andreasson &lt;blueflux at koffein.net&gt; #
> >> # This program is free software; you can redistribute it and/or modify
> >> # it under the terms of the GNU General Public License as published by
> >> # the Free Software Foundation; version 2 of the License.
> >> #
> >> # This program is distributed in the hope that it will be useful, #
> >> but WITHOUT ANY WARRANTY; without even the implied warranty of #
> >> MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> >> # GNU General Public License for more details.
> >> #
> >> # You should have received a copy of the GNU General Public License #
> >> along with this program or from the site that you downloaded it #
> >> from; if not, write to the Free Software Foundation, Inc., 59 Temple #
> >> Place, Suite 330, Boston, MA  02111-1307   USA
> >> #
> >>
> >>
> ###########################################################################
> >> #
> >> # 1. Configuration options.
> >> #
> >>
> >>
> ###########################################################################
> >> #
> >> # Local Area Network configuration.
> >> #
> >> # your LAN's IP range and localhost IP. /24 means to only use the
> >> first 24  # bits of the 32 bit IP adress. the same as netmask
> >> 255.255.255.0 #
> >>
> >> LAN_IP="192.168.0.1"
> >> LAN_IP_RANGE="192.168.0.0/24"
> >> LAN_BCAST_ADRESS="192.168.255.255"
> >> LAN_IFACE="eth1"
> >>
> >>
> ###########################################################################
> >> #
> >> # Localhost Configuration.
> >> #
> >>
> >> LO_IFACE="lo"
> >> LO_IP="127.0.0.1"
> >>
> >>
> ###########################################################################
> >> #
> >> # Internet Configuration.
> >> #
> >>
> >> INET_IP=""
> >> INET_IFACE="eth0"
> >>
> >>
> ###########################################################################
> >> #
> >> # IPTables Configuration.
> >> #
> >>
> >> IPTABLES="/sbin/iptables"
> >>
> >>
> ###########################################################################
> >> #
> >> # 2. Module loading.
> >> #
> >>
> >> #
> >> # Needed to initially load modules
> >> #
> >> /sbin/depmod -a
> >>
> >> #
> >> # Adds some iptables targets like LOG, REJECT and MASQUARADE.
> >> #
> >> /sbin/modprobe ip_conntrack
> >> /sbin/modprobe ip_tables
> >> /sbin/modprobe iptable_filter
> >> /sbin/modprobe iptable_mangle
> >> /sbin/modprobe iptable_nat
> >> /sbin/modprobe ipt_LOG
> >> #/sbin/modprobe ipt_REJECT
> >> #/sbin/modprobe ipt_MASQUERADE
> >>
> >> #
> >> # Support for owner matching
> >> #
> >> #/sbin/modprobe ipt_owner
> >>
> >> #
> >> # Support for connection tracking of FTP and IRC.
> >> #
> >> /sbin/modprobe ip_conntrack_ftp
> >> /sbin/modprobe ip_conntrack_irc
> >>
> >>
> >>
> ###########################################################################
> >> #
> >> # 3. /proc set up.
> >> #
> >> # Enable ip_forward if you have two or more networks, including the #
> >> Internet, that needs forwarding of packets through this box. This is #
> >> critical since it is turned off as default in Linux.
> >> #
> >>
> >> echo "1" > /proc/sys/net/ipv4/ip_forward
> >>
> >> #
> >> # Dynamic IP users:
> >> #
> >> #echo "1" > /proc/sys/net/ipv4/ip_dynaddr
> >>
> >>
> ###########################################################################
> >> #
> >> # 4. IPTables rules set up.
> >> #
> >> # Set default policies for the INPUT, FORWARD and OUTPUT chains. #
> >>
> >> $IPTABLES -P INPUT DROP
> >> $IPTABLES -P OUTPUT DROP
> >> $IPTABLES -P FORWARD DROP
> >>
> >> #
> >> # bad_tcp_packets chain
> >> #
> >> # Take care of bad TCP packets that we don't want.
> >> #
> >>
> >> $IPTABLES -N bad_tcp_packets
> >> $IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j
> >> LOG \ --log-prefix "New not syn:"
> >> $IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j
> >> DROP
> >>
> >> #
> >> # Do some checks for obviously spoofed IP's
> >> #
> >>
> >> $IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 192.168.0.0/16 -j DROP
> >> $IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 10.0.0.0/8 -j DROP
> >> $IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 172.16.0.0/12 -j DROP
> >>
> >> #
> >> # Enable simple IP Forwarding and Network Address Translation
> >> #
> >>
> >> $IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j SNAT --to-source
> >> $INET_IP
> >>
> >> #
> >> # Bad TCP packets we don't want
> >> #
> >>
> >> $IPTABLES -A FORWARD -p tcp -j bad_tcp_packets
> >>
> >> #
> >> # Accept the packets we actually want to forward
> >> #
> >>
> >> $IPTABLES -A FORWARD -i $LAN_IFACE -j ACCEPT
> >> $IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
> >> $IPTABLES -A FORWARD -m limit --limit 3/minute --limit-burst 3 -j LOG
> >> \ --log-level DEBUG --log-prefix "IPT FORWARD packet died: "
> >>
> >> #
> >> # Create separate chains for ICMP, TCP and UDP to traverse
> >> #
> >>
> >> $IPTABLES -N icmp_packets
> >> $IPTABLES -N tcp_packets
> >> $IPTABLES -N udpincoming_packets
> >>
> >> #
> >> # The allowed chain for TCP connections
> >> #
> >>
> >> $IPTABLES -N allowed
> >> $IPTABLES -A allowed -p TCP --syn -j ACCEPT
> >> $IPTABLES -A allowed -p TCP -m state --state ESTABLISHED,RELATED -j
> >> ACCEPT $IPTABLES -A allowed -p TCP -j DROP
> >>
> >> #
> >> # ICMP rules
> >> #
> >>
> >> # Changed rules totally
> >> $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 8 -j ACCEPT
> >> $IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT
> >>
> >> #
> >> # TCP rules
> >> #
> >>
> >> $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 21 -j allowed
> >> $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 22 -j allowed
> >> $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 80 -j allowed
> >> $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 113 -j allowed
> >>
> >> #
> >> # UDP ports
> >> #
> >>
> >> # nondocumented commenting out of these rules
> >> #$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 53 -j
> >> ACCEPT #$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port
> >> 123 -j ACCEPT $IPTABLES -A udpincoming_packets -p UDP -s 0/0
> >> --source-port 2074 -j ACCEPT $IPTABLES -A udpincoming_packets -p UDP
> >> -s 0/0 --source-port 4000 -j ACCEPT
> >>
> >> ##########################
> >> # INPUT chain
> >> #
> >> # Bad TCP packets we don't want.
> >> #
> >>
> >> $IPTABLES -A INPUT -p tcp -j bad_tcp_packets
> >>
> >> #
> >> # Rules for incoming packets from the internet.
> >> #
> >>
> >> $IPTABLES -A INPUT -p ICMP -i $INET_IFACE -j icmp_packets
> >> $IPTABLES -A INPUT -p TCP -i $INET_IFACE -j tcp_packets
> >> $IPTABLES -A INPUT -p UDP -i $INET_IFACE -j udpincoming_packets
> >>
> >> #
> >> # Rules for special networks not part of the Internet
> >> #
> >>
> >> $IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $LAN_BCAST_ADRESS -j ACCEPT
> >> $IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LO_IP -j ACCEPT
> >> $IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LAN_IP -j ACCEPT
> >> $IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $INET_IP -j ACCEPT
> >> $IPTABLES -A INPUT -p ALL -i $LAN_IFACE -s $LAN_IP_RANGE -j ACCEPT
> >> $IPTABLES -A INPUT -p ALL -d $INET_IP -m state --state
> >> ESTABLISHED,RELATED \ -j ACCEPT
> >> $IPTABLES -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG \
> >> --log-level DEBUG --log-prefix "IPT INPUT packet died: "
> >>
> >> ###############################
> >> # OUTPUT chain
> >> #
> >> #
> >> # Bad TCP packets we don't want.
> >> #
> >>
> >> $IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets
> >>
> >> #
> >> # Special OUTPUT rules to decide which IP's to allow.
> >> #
> >>
> >> $IPTABLES -A OUTPUT -p ALL -s $LO_IP -j ACCEPT
> >> $IPTABLES -A OUTPUT -p ALL -s $LAN_IP -j ACCEPT
> >> $IPTABLES -A OUTPUT -p ALL -s $INET_IP -j ACCEPT
> >>
> >> #
> >> # Log weird packets that don't match the above.
> >> #
> >>
> >> $IPTABLES -A OUTPUT -m limit --limit 3/minute --limit-burst 3 -j LOG \
> >> --log-level DEBUG --log-prefix "IPT OUTPUT packet died: "
> > --
> > Alton R. Pouncey, II
> 
> 
> -- 
> Raymond Norton
> Little Crow Telemedia Network
> 320-234-0270
> 
> 
> 
> _______________________________________________
> http://www.ntlug.org/mailman/listinfo/discuss
> 
-- 
Alton R. Pouncey, II
SCSA, SCNA, CCNA, CIW Associate
Director of Information Services
'print pack("H*","616c746f6e40747261696e6572732d722d75732e636f6d"), $/'
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