#!/bin/sh
#
# ----------------------------------------------------------------------------
# Last modified by Gerhard Mourani: 04-25-2000
# ----------------------------------------------------------------------------
# Copyright (C) 1997, 1998, 1999 Robert L. Ziegler
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for educational, research, private and non-profit purposes,
# without fee, and without a written agreement is hereby granted.
# This software is provided as an example and basis for individual firewall
# development. This software is provided without warranty.
#
# Any material furnished by Robert L. Ziegler is furnished on an
# "as is" basis. He makes no warranties of any kind, either expressed
# or implied as to any matter including, but not limited to, warranty
# of fitness for a particular purpose, exclusivity or results obtained
# from use of the material.
# ----------------------------------------------------------------------------
#
# Invoked from /etc/rc.d/init.d/firewall.
# chkconfig: - 60 95
# description: Starts and stops the IPCHAINS Firewall \
# used to provide Firewall network services.
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
if [ ${NETWORKING} = "no" ]
then
exit 0
fi
if [ ! -x /sbin/ipchains ]; then
exit 0
fi
# See how we were called.
case "$1" in
start)
echo -n "Starting Firewalling Services: "
# Some definitions for easy maintenance.
# ----------------------------------------------------------------------------
# EDIT THESE TO SUIT YOUR SYSTEM AND ISP.
EXTERNAL_INTERFACE="eth0" # Internet connected interface
LOOPBACK_INTERFACE="lo" # Your local naming convention
IPADDR="my.ip.address" # Your IP address
ANYWHERE="any/0" # Match any IP address
NAMESERVER_1="my.name.server.1" # Everyone must have at least one
NAMESERVER_2="my.name.server.2" # Your secondary name server
MY_ISP="my.isp.address.range/24" # ISP & NOC address range
SMTP_SERVER="my.smtp.server" # Your Mail Hub Server.
SYSLOG_SERVER="syslog.internal.server" # Your syslog internal server
SYSLOG_CLIENT="sys.int.client.range/24" # Your syslog internal client range
LOOPBACK="127.0.0.0/8" # Reserved loopback address range
CLASS_A="10.0.0.0/8" # Class A private networks
CLASS_B="172.16.0.0/12" # Class B private networks
CLASS_C="192.168.0.0/16" # Class C private networks
CLASS_D_MULTICAST="224.0.0.0/4" # Class D multicast addresses
CLASS_E_RESERVED_NET="240.0.0.0/5" # Class E reserved addresses
BROADCAST_SRC="0.0.0.0" # Broadcast source address
BROADCAST_DEST="255.255.255.255" # Broadcast destination address
PRIVPORTS="0:1023" # Well known, privileged port range
UNPRIVPORTS="1024:65535" # Unprivileged port range
# ----------------------------------------------------------------------------
# SSH starts at 1023 and works down to 513 for
# each additional simultaneous incoming connection.
SSH_PORTS="1022:1023" # range for SSH privileged ports
# traceroute usually uses -S 32769:65535 -D 33434:33523
TRACEROUTE_SRC_PORTS="32769:65535"
TRACEROUTE_DEST_PORTS="33434:33523"
# ----------------------------------------------------------------------------
# Default policy is DENY
# Explicitly accept desired INCOMING & OUTGOING connections
# Remove all existing rules belonging to this filter
ipchains -F
# Clearing all current rules and user defined chains
ipchains -X
# Set the default policy of the filter to deny.
# Don't even bother sending an error message back.
ipchains -P input DENY
ipchains -P output DENY
ipchains -P forward DENY
# ----------------------------------------------------------------------------
# LOOPBACK
# Unlimited traffic on the loopback interface.
ipchains -A input -i $LOOPBACK_INTERFACE -j ACCEPT
ipchains -A output -i $LOOPBACK_INTERFACE -j ACCEPT
# ----------------------------------------------------------------------------
# Network Ghouls
# Deny access to jerks
# /etc/rc.d/rc.firewall.blocked contains a list of
# ipchains -A input -i $EXTERNAL_INTERFACE -s address -j DENY
# rules to block from any access.
# Refuse any connection from problem sites
#if [ -f /etc/rc.d/rc.firewall.blocked ]; then
# . /etc/rc.d/rc.firewall.blocked
#fi
# ----------------------------------------------------------------------------
# SPOOFING & BAD ADDRESSES
# Refuse spoofed packets.
# Ignore blatantly illegal source addresses.
# Protect yourself from sending to bad addresses.
# Refuse spoofed packets pretending to be from the external address.
ipchains -A input -i $EXTERNAL_INTERFACE -s $IPADDR -j DENY -l
# Refuse packets claiming to be to or from a Class A private network
ipchains -A input -i $EXTERNAL_INTERFACE -s $CLASS_A -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -d $CLASS_A -j DENY -l
ipchains -A output -i $EXTERNAL_INTERFACE -s $CLASS_A -j REJECT -l
ipchains -A output -i $EXTERNAL_INTERFACE -d $CLASS_A -j REJECT -l
# Refuse packets claiming to be to or from a Class B private network
ipchains -A input -i $EXTERNAL_INTERFACE -s $CLASS_B -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -d $CLASS_B -j DENY -l
ipchains -A output -i $EXTERNAL_INTERFACE -s $CLASS_B -j REJECT -l
ipchains -A output -i $EXTERNAL_INTERFACE -d $CLASS_B -j REJECT -l
# Refuse packets claiming to be to or from a Class C private network
# ipchains -A input -i $EXTERNAL_INTERFACE -s $CLASS_C -j DENY -l
# ipchains -A input -i $EXTERNAL_INTERFACE -d $CLASS_C -j DENY -l
# ipchains -A output -i $EXTERNAL_INTERFACE -s $CLASS_C -j REJECT -l
# ipchains -A output -i $EXTERNAL_INTERFACE -d $CLASS_C -j REJECT -l
# Refuse packets claiming to be from the loopback interface
ipchains -A input -i $EXTERNAL_INTERFACE -s $LOOPBACK -j DENY -l
ipchains -A output -i $EXTERNAL_INTERFACE -s $LOOPBACK -j REJECT -l
# Refuse broadcast address SOURCE packets
ipchains -A input -i $EXTERNAL_INTERFACE -s $BROADCAST_DEST -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -d $BROADCAST_SRC -j DENY -l
# Refuse Class D multicast addresses (in.h) (NET-3-HOWTO)
# Multicast is illegal as a source address.
# Multicast uses UDP.
ipchains -A input -i $EXTERNAL_INTERFACE -s $CLASS_D_MULTICAST -j DENY -l
# Refuse Class E reserved IP addresses
ipchains -A input -i $EXTERNAL_INTERFACE -s $CLASS_E_RESERVED_NET -j DENY -l
# refuse addresses defined as reserved by the IANA
# 0.*.*.*, 1.*.*.*, 2.*.*.*, 5.*.*.*, 7.*.*.*, 23.*.*.*, 27.*.*.*
# 31.*.*.*, 37.*.*.*, 39.*.*.*, 41.*.*.*, 42.*.*.*, 58-60.*.*.*
# 65-95.*.*.*, 96-126.*.*.*, 197.*.*.*, 201.*.*.* (?), 217-223.*.*.*
ipchains -A input -i $EXTERNAL_INTERFACE -s 1.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 2.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 5.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 7.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 23.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 27.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 31.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 37.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 39.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 41.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 42.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 58.0.0.0/7 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 60.0.0.0/8 -j DENY -l
#65: 01000001 - /3 includes 64 - need 65-79 spelled out
ipchains -A input -i $EXTERNAL_INTERFACE -s 65.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 66.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 67.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 68.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 69.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 70.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 71.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 72.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 73.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 74.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 75.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 76.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 77.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 78.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 79.0.0.0/8 -j DENY -l
#80: 01010000 - /4 masks 80-95
ipchains -A input -i $EXTERNAL_INTERFACE -s 80.0.0.0/4 -j DENY -l
# 96: 01100000 - /4 makses 96-111
ipchains -A input -i $EXTERNAL_INTERFACE -s 96.0.0.0/4 -j DENY -l
#126: 01111110 - /3 includes 127 - need 112-126 spelled out
ipchains -A input -i $EXTERNAL_INTERFACE -s 112.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 113.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 114.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 115.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 116.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 117.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 118.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 119.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 120.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 121.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 122.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 123.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 124.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 125.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 126.0.0.0/8 -j DENY -l
#217: 11011001 - /5 includes 216 - need 217-219 spelled out
ipchains -A input -i $EXTERNAL_INTERFACE -s 217.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 218.0.0.0/8 -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -s 219.0.0.0/8 -j DENY -l
#223: 11011111 - /6 masks 220-223
ipchains -A input -i $EXTERNAL_INTERFACE -s 220.0.0.0/6 -j DENY -l
# ----------------------------------------------------------------------------
# ICMP
# To prevent denial of service attacks based on ICMP bombs, filter
# incoming Redirect (5) and outgoing Destination Unreachable (3).
# Note, however, disabling Destination Unreachable (3) is not
# advisable, as it is used to negotiate packet fragment size.
# For bi-directional ping.
# Message Types: Echo_Reply (0), Echo_Request (8)
# To prevent attacks, limit the src addresses to your ISP range.
#
# For outgoing traceroute.
# Message Types: INCOMING Dest_Unreachable (3), Time_Exceeded (11)
# default UDP base: 33434 to base+nhops-1
#
# For incoming traceroute.
# Message Types: OUTGOING Dest_Unreachable (3), Time_Exceeded (11)
# To block this, deny OUTGOING 3 and 11
# 0: echo-reply (pong)
# 3: destination-unreachable, port-unreachable, fragmentation-needed, etc.
# 4: source-quench
# 5: redirect
# 8: echo-request (ping)
# 11: time-exceeded
# 12: parameter-problem
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 0 -d $IPADDR -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 3 -d $IPADDR -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 4 -d $IPADDR -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 11 -d $IPADDR -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 12 -d $IPADDR -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $MY_ISP 8 -d $IPADDR -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p icmp \
-s $IPADDR 0 -d $MY_ISP -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p icmp \
-s $IPADDR 3 -d $MY_ISP -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p icmp \
-s $IPADDR 4 -d $ANYWHERE -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p icmp \
-s $IPADDR 8 -d $ANYWHERE -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p icmp \
-s $IPADDR 12 -d $ANYWHERE -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p icmp \
-s $IPADDR 11 -d $MY_ISP -j ACCEPT
# ----------------------------------------------------------------------------
# UDP INCOMING TRACEROUTE
# traceroute usually uses -S 32769:65535 -D 33434:33523
ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
-s $MY_ISP $TRACEROUTE_SRC_PORTS \
-d $IPADDR $TRACEROUTE_DEST_PORTS -j ACCEPT -l
ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
-s $ANYWHERE $TRACEROUTE_SRC_PORTS \
-d $IPADDR $TRACEROUTE_DEST_PORTS -j DENY -l
# ----------------------------------------------------------------------------
# DNS server
# ----------
# DNS: full server
# server/client to server query or response
ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
-s $ANYWHERE $UNPRIVPORTS \
-d $IPADDR 53 -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p udp \
-s $IPADDR 53 \
-d $ANYWHERE $UNPRIVPORTS -j ACCEPT
# DNS client & Zone Transfers (53)
# ---------------
ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
-s $NAMESERVER_1 53 \
-d $IPADDR $UNPRIVPORTS -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p udp \
-s $IPADDR $UNPRIVPORTS \
-d $NAMESERVER_1 53 -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp ! -y \
-s $NAMESERVER_1 53 \
-d $IPADDR $UNPRIVPORTS -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p tcp \
-s $IPADDR $UNPRIVPORTS \
-d $NAMESERVER_1 53 -j ACCEPT
# ----------------------------------------------------------------------------
# TCP accept only on selected ports
# ---------------------------------
# ------------------------------------------------------------------
# SSH server (22)
# ---------------
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
-s $ANYWHERE $UNPRIVPORTS \
-d $IPADDR 22 -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
-s $IPADDR 22 \
-d $ANYWHERE $UNPRIVPORTS -j ACCEPT
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
-s $ANYWHERE $SSH_PORTS \
-d $IPADDR 22 -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
-s $IPADDR 22 \
-d $ANYWHERE $SSH_PORTS -j ACCEPT
# ------------------------------------------------------------------
# AUTH server (113)
# -----------------
# Reject, rather than deny, the incoming auth port. (NET-3-HOWTO)
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
-s $ANYWHERE \
-d $IPADDR 113 -j REJECT
# ------------------------------------------------------------------
# SYSLOG server (514)
# -----------------
# Provides full remote logging. Using this feature you're able to
# control all syslog messages on one host.
# ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
# -s $SYSLOG_CLIENT \
# -d $IPADDR 514 -j ACCEPT
# SYSLOG client (514)
# -----------------
# ipchains -A output -i $EXTERNAL_INTERFACE -p udp \
# -s $IPADDR 514 \
# -d $SYSLOG_SERVER 514 -j ACCEPT
# ------------------------------------------------------------------
# SMTP server (25)
# ----------------
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
-s $ANYWHERE $UNPRIVPORTS \
-d $IPADDR 25 -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
-s $IPADDR 25 \
-d $ANYWHERE $UNPRIVPORTS -j ACCEPT
# SMTP client (25)
# ----------------
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp ! -y \
-s $ANYWHERE 25 \
-d $IPADDR $UNPRIVPORTS -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p tcp \
-s $IPADDR $UNPRIVPORTS \
-d $ANYWHERE 25 -j ACCEPT
# ------------------------------------------------------------------
# IMAP server (143)
# -----------------
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
-s $ANYWHERE $UNPRIVPORTS \
-d $IPADDR 143 -j ACCEPT
ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
-s $IPADDR 143 \
-d $ANYWHERE $UNPRIVPORTS -j ACCEPT
# POP server (110)
# -----------------
# ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
# -s $ANYWHERE $UNPRIVPORTS \
# -d $IPADDR 110 -j ACCEPT
# ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
# -s $IPADDR 110 \
# -d $ANYWHERE $UNPRIVPORTS -j ACCEPT
# ------------------------------------------------------------------
# OUTGOING TRACEROUTE
# -------------------
ipchains -A output -i $EXTERNAL_INTERFACE -p udp \
-s $IPADDR $TRACEROUTE_SRC_PORTS \
-d $ANYWHERE $TRACEROUTE_DEST_PORTS -j ACCEPT
# ----------------------------------------------------------------------------
# Enable logging for selected denied packets
ipchains -A input -i $EXTERNAL_INTERFACE -p tcp \
-d $IPADDR -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
-d $IPADDR $PRIVPORTS -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -p udp \
-d $IPADDR $UNPRIVPORTS -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 5 -d $IPADDR -j DENY -l
ipchains -A input -i $EXTERNAL_INTERFACE -p icmp \
-s $ANYWHERE 13:255 -d $IPADDR -j DENY -l
# ----------------------------------------------------------------------------
;;
stop)
echo -n "Shutting Firewalling Services: "
# Remove all existing rules belonging to this filter
ipchains -F
# Delete all user-defined chain to this filter
ipchains -X
# Reset the default policy of the filter to accept.
ipchains -P input ACCEPT
ipchains -P output ACCEPT
ipchains -P forward ACCEPT
;;
status)
status firewall
;;
restart|reload)
$0 stop
$0 start
;;
*)
echo "Usage: firewall {start|stop|status|restart|reload}"
exit 1
esac
exit 0
|
