# #+----------------------------------------------------------------------------------------+ #!/bin/sh # # rc.firewall-2.4 FWVER=0.73 # # Initial SIMPLE IP Masquerade test for 2.4.x kernels # using IPTABLES. # # Once IP Masquerading has been tested, with this simple # ruleset, it is highly recommended to use a stronger # IPTABLES ruleset either given later in this HOWTO or # from another reputable resource. # # # # Log: # 0.73 - REJECT is not a legal policy yet; back to DROP # 0.72 - Changed the default block behavior to REJECT not DROP # 0.71 - Added clarification that PPPoE users need to use # "ppp0" instead of "eth0" for their external interface # 0.70 - Added commented option for IRC nat module # - Added additional use of environment variables # - Added additional formatting # 0.63 - Added support for the IRC IPTABLES module # 0.62 - Fixed a typo on the MASQ enable line that used eth0 # instead of $EXTIF # 0.61 - Changed the firewall to use variables for the internal # and external interfaces. # 0.60 - 0.50 had a mistake where the ruleset had a rule to DROP # all forwarded packets but it didn't have a rule to ACCEPT # any packets to be forwarded either # - Load the ip_nat_ftp and ip_conntrack_ftp modules by default # 0.50 - Initial draft # echo -e "\n\nLoading simple rc.firewall version $FWVER..\n" # The location of the iptables and kernel module programs # # If your Linux distribution came with a copy of iptables, # most likely all the programs will be located in /sbin. If # you manually compiled iptables, the default location will # be in /usr/local/sbin # # ** Please use the "whereis iptables" command to figure out # ** where your copy is and change the path below to reflect # ** your setup # #IPTABLES=/sbin/iptables IPTABLES=/usr/sbin/iptables DEPMOD=/sbin/depmod INSMOD=/sbin/insmod #Setting the EXTERNAL and INTERNAL interfaces for the network # # Each IP Masquerade network needs to have at least one # external and one internal network. The external network # is where the natting will occur and the internal network # should preferably be addressed with a RFC1918 private address # scheme. # # For this example, "eth0" is external and "eth1" is internal" # # # NOTE: If this doesnt EXACTLY fit your configuration, you must # change the EXTIF or INTIF variables above. For example: # # If you are a PPPoE or analog modem user: # # EXTIF="ppp0" # # EXTIF="eth0" INTIF="eth1" INTIFVPN0="tun0" echo " 1. Internal Interface : $INTIF" echo " VPN0 Interface : $INTIFVPN0" echo " External Interface: $EXTIF" echo -en " loading modules: " # Need to verify that all modules have all required dependencies # echo " - Verifying that all kernel modules are ok" $DEPMOD -a # With the new IPTABLES code, the core MASQ functionality is now either # modular or compiled into the kernel. This HOWTO shows ALL IPTABLES # options as MODULES. If your kernel is compiled correctly, there is # NO need to load the kernel modules manually. # # NOTE: The following items are listed ONLY for informational reasons. # There is no reason to manual load these modules unless your # kernel is either mis-configured or you intentionally disabled # the kernel module autoloader. # # Upon the commands of starting up IP Masq on the server, the # following kernel modules will be automatically loaded: # # NOTE: Only load the IP MASQ modules you need. All current IP MASQ # modules are shown below but are commented out from loading. # =============================================================== echo "----------------------------------------------------------------------" #Load the main body of the IPTABLES module - "iptable" # - Loaded automatically when the "iptables" command is invoked # # - Loaded manually to clean up kernel auto-loading timing issues # echo -en "ip_tables, " $INSMOD ip_tables #Load the IPTABLES filtering module - "iptable_filter" # - Loaded automatically when filter policies are activated #Load the stateful connection tracking framework - "ip_conntrack" # # The conntrack module in itself does nothing without other specific # conntrack modules being loaded afterwards such as the "ip_conntrack_ftp" # module # # - This module is loaded automatically when MASQ functionality is # enabled # # - Loaded manually to clean up kernel auto-loading timing issues # echo -en "ip_conntrack, " $INSMOD ip_conntrack #Load the FTP tracking mechanism for full FTP tracking # # Enabled by default -- insert a "#" on the next line to deactivate # echo -en "ip_conntrack_ftp, " $INSMOD ip_conntrack_ftp #Load the IRC tracking mechanism for full IRC tracking # # Enabled by default -- insert a "#" on the next line to deactivate # echo -en "ip_conntrack_irc, " $INSMOD ip_conntrack_irc #Load the general IPTABLES NAT code - "iptable_nat" # - Loaded automatically when MASQ functionality is turned on # # - Loaded manually to clean up kernel auto-loading timing issues # echo -en "iptable_nat, " $INSMOD iptable_nat #Loads the FTP NAT functionality into the core IPTABLES code # Required to support non-PASV FTP. # # Enabled by default -- insert a "#" on the next line to deactivate # echo -en "ip_nat_ftp, " $INSMOD ip_nat_ftp #Loads the IRC NAT functionality into the core IPTABLES code # Require to support NAT of IRC DCC requests # # Disabled by default -- remove the "#" on the next line to activate # #echo -e "ip_nat_irc" #$INSMOD ip_nat_irc echo "----------------------------------------------------------------------" # Just to be complete, here is a list of the remaining kernel modules # and their function. Please note that several modules should be only # loaded by the correct master kernel module for proper operation. # -------------------------------------------------------------------- # # ipt_mark - this target marks a given packet for future action. # This automatically loads the ipt_MARK module # # ipt_tcpmss - this target allows to manipulate the TCP MSS # option for braindead remote firewalls. # This automatically loads the ipt_TCPMSS module # # ipt_limit - this target allows for packets to be limited to # to many hits per sec/min/hr # # ipt_multiport - this match allows for targets within a range # of port numbers vs. listing each port individually # # ipt_state - this match allows to catch packets with various # IP and TCP flags set/unset # # ipt_unclean - this match allows to catch packets that have invalid # IP/TCP flags set # # iptable_filter - this module allows for packets to be DROPped, # REJECTed, or LOGged. This module automatically # loads the following modules: # # ipt_LOG - this target allows for packets to be # logged # # ipt_REJECT - this target DROPs the packet and returns # a configurable ICMP packet back to the # sender. # # iptable_mangle - this target allows for packets to be manipulated # for things like the TCPMSS option, etc. echo -e " Done loading modules.\n" #CRITICAL: Enable IP forwarding since it is disabled by default since # # Redhat Users: you may try changing the options in # /etc/sysconfig/network from: # # FORWARD_IPV4=false # to # FORWARD_IPV4=true # echo " Enabling forwarding.." echo "1" > /proc/sys/net/ipv4/ip_forward # Dynamic IP users: # # If you get your IP address dynamically from SLIP, PPP, or DHCP, # enable this following option. This enables dynamic-address hacking # which makes the life with Diald and similar programs much easier. # echo " Enabling DynamicAddr.." echo "1" > /proc/sys/net/ipv4/ip_dynaddr # Enable simple IP forwarding and Masquerading # # NOTE: In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT. # # NOTE #2: The following is an example for an internal LAN address in the # 192.168.0.x network with a 255.255.255.0 or a "24" bit subnet mask # connecting to the Internet on external interface "eth0". This # example will MASQ internal traffic out to the Internet but not # allow non-initiated traffic into your internal network. # # # ** Please change the above network numbers, subnet mask, and your # *** Internet connection interface name to match your setup # #Clearing any previous configuration # # Unless specified, the defaults for INPUT and OUTPUT is ACCEPT # The default for FORWARD is DROP (REJECT is not a valid policy) # echo " Clearing any existing rules and setting default policy.." $IPTABLES -F $IPTABLES -F INPUT $IPTABLES -F OUTPUT $IPTABLES -F FORWARD $IPTABLES -t nat -F $IPTABLES -P INPUT ACCEPT $IPTABLES -P OUTPUT ACCEPT $IPTABLES -P FORWARD DROP echo " FWD: Allow all connections OUT and only existing and related ones IN" $IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT $IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT # VPN $IPTABLES -A FORWARD -i $EXTIF -o $INTIFVPN0 -m state --state ESTABLISHED,RELATED -j ACCEPT $IPTABLES -A FORWARD -i $INTIFVPN0 -o $EXTIF -j ACCEPT $IPTABLES -A FORWARD -i $INTIFVPN0 -o $INTIF -j ACCEPT $IPTABLES -A FORWARD -i $INTIF -o $INTIFVPN0 -j ACCEPT $IPTABLES -A FORWARD -j LOG #drop icmp packets $IPTABLES -A INPUT -i $EXTIF -p icmp -j DROP #Denied ports $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 1:24 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 1:24 -j REJECT #SMTP $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 26:79 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 26:79 -j REJECT #http $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 81:442 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 81:442 -j REJECT #https $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 444:1193 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 444:1193 -j REJECT #Openvpn $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 1195:3999 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 1195:3999 -j REJECT #web,ts $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 4050:5221 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 4050:5221 -j REJECT # $IPTABLES -A INPUT -p tcp -i $EXTIF --dport 5224:6600 -j REJECT $IPTABLES -A INPUT -p udp -i $EXTIF --dport 5224:6600 -j REJECT echo " Enabling SNAT (MASQUERADE) functionality on $EXTIF" $IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE $IPTABLES -t nat -A POSTROUTING -o $INTIFVPN0 -j MASQUERADE echo -e "\nrc.firewall-2.4 v$FWVER done.\n" #----------------------------------------------------------------------------------------+$ #rc.firewall-2.4 STOP>