Firewalls: Difference between revisions
→OpenWrt: added information about MSS Clamping |
Mention OpenBSD and PF |
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== Microtik == | == Microtik == | ||
== OpenBSD == | |||
''See the Instructions for [[Setting up a gateway on OpenBSD]].'' | |||
OpenBSD comes with a robust, flexible and highly performant firewall called "PF" that works well on AMPRNet. See https://www.openbsd.org/faq/pf/ for more information. | |||
== OpenWrt == | == OpenWrt == | ||
Latest revision as of 12:12, 4 May 2024
Welcome to the Firewall Wiki.
This page is intended to be edited by the community to add use practices, command syntax, etc. regarding firewalling and security on AMPRNet nodes. While each operator is ultimately responsible for the administration of their node, it is highly suggested amongst the 44Net mailing list Community that nodes be firewalled.
Cisco
DD-WRT
DD-WRT uses an iptables-based firewall (see iptables below). Custom rules can be entered at Administration > Commands > "Save Firewall" on the web GUI.
See:
D-Link
On some D-Link devices, the port forwarding feature allows for the options: TCP, UDP and Other. The "Other" option on these models are capable of Destination NAT of IPENCAP packets.
To enable input of IPENCAP (IP Protocol Number 4) Note: this rule is required for other AMPR nodes to initiate inbound traffic to your node.
In Port Forwarding on the web GUI:
- Create a new Port Forward
- Enter the LAN IP of your AMPR node
- Select "Other"
- Type the number 4 into the field
iptables
NOTE:
- On an iptables-based firewall, you must enable connection tracking on the tunl0 interface in order to enable Stateful Packet Inspection (i.e. a stateful firewall).
- Since the IPENCAP Linux Kernel Module IPIP is in the kernel, you must set the default forwarding policy to DROP or REJECT.
- If you set your default routing policy to ACCEPT, all packets that have not been explicitly DROPped or REJECTed elsewhere, will route, regardless of firewall policies.
- For most embedded devices, it is suggested to use ipset rules instead
General Bogon rules - see: https://en.wikipedia.org/wiki/Bogon_filtering
############################################################ # DROPS IP TRAFFIC THAT'S INVALID ENTERING OR EXITING AMPR # THIS PREVENTS A GENERAL LOOP iptables -I FORWARD -i tunl0 -o tunl0 -j DROP # DROPS OUTBOUND IPs NOT FROM YOUR ALLOCATION (BCP 38) iptables -t raw -I PREROUTING ! -s 44.xxx.xxx.xxx/xx -i br-amprnet -j DROP # DROPS ROGUE INBOUND ASSIGNED IPs FROM LOOPING THROUGH tunl0 VIA IPENCAP iptables -t raw -I PREROUTING -s 44.xxx.xxx.xxx/xx -i tunl0 -j DROP # DROPS OUTBOUND UNASSIGNED IPs FROM LOOPING THROUGH tunl0 VIA IPENCAP # YOU MUST ADD A RULE UNDER THIS LINE TO MAKE EXCEPTIONS (BCP 38) iptables -I FORWARD ! -s 44.xxx.xxx.xxx/xx -o tunl0 -j DROP ############################################################ # DROPS BOGONS ENTERING AMPRNet # SEE http://www.team-cymru.org/Services/Bogons/bogon-bn-nonagg.txt iptables -t raw -I PREROUTING -s 0.0.0.0/8 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 10.0.0.0/8 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 100.64.0.0/10 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 127.0.0.0/8 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 169.254.0.0/16 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 172.16.0.0/12 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 192.0.0.0/24 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 192.0.2.0/24 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 192.168.0.0/16 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 198.18.0.0/15 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 198.51.100.0/24 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 203.0.113.0/24 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 224.0.0.0/4 -i tunl0 -j DROP iptables -t raw -I PREROUTING -s 240.0.0.0/4 -i tunl0 -j DROP # Block of Test AMPRNet Subnet # iptables -t raw -I PREROUTING -s 44.128.0.0/16 -i tunl0 -j DROP # (you can optionally block your subnet) ############################################################ # THIS PREVENTS NESTED IPENCAP (BCP 38) iptables -t raw -I PREROUTING -p 4 -i tunl0 -j DROP
Dynamic IPENCAP Filtering of AMPR Nodes (using iptables)
To enable dynamic filtering of IPENCAP (IP Protocol Number 4)
NOTE:
- This script needs work, see Thu Jan 10 11:09:27 PST 2019 message in the 44Net mailing list archive. Due to extreme overheard running on many devices, the ipset script is suggested instead.
- This rule (or one of the ipset or static rules below) is required for other AMPR nodes to initiate inbound traffic to your node.
REQUIRED: ampr-ripd (using the -x and -d arguments), the diff command from the diffutils package and the sed command.
# Place this rule a the last firewall command # Uncomment sleep command below if the rule does not appear # as load_ipipfilter.sh is still executing # sleep 10 # load ipipfilter list rule iptables -t filter -I INPUT -p 4 -i <INTERFACE OF WAN> -j ipipfilter
#!/bin/sh
# load encap.txt into ipipfilter list
# by Rob, PE1CHL
# load_ipipfilter.sh
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
AMPRGW="<AMPRGW>"
gwfile="/tmp/gw"
cd /var/lib/ampr-ripd || exit 1
# Parse encap.txt for Node IPs and place in /tmp/gw
grep addprivate encap.txt | sed -e 's/.*encap //' | sort -u >$gwfile
# Run command to create CHAIN, IF no system output, CHAIN was created
iptables -N ipipfilter 2>/dev/null
if [ $? -eq 0 ]
# DO NOT PLACE EMPTY LINES BETWEEN THE TWO COMMANDS ABOVE. ###
# THE EQUATION ASKS IF THE LAST SYSTEM COMMAND ENTERED ###
# RETURNS "NOTHING." ADDING A SPACE WILL CHANGE RESULTS OF THE IF COMMAND. ###
##The two lines above replace the line below, which does not work on OpenWRT
# if iptables -N ipipfilter 2>/dev/null
##
# IF no system output, THEN flush the CHAIN and add AMPRGW,
# add nodes in encap.txt and a final DROP rule
then
iptables -F ipipfilter
iptables -A ipipfilter -s $AMPRGW -j ACCEPT
while read ip
do
iptables -A ipipfilter -s $ip -j ACCEPT
done <$gwfile
iptables -A ipipfilter -j DROP
# ELSE, the CHAIN already exists, determine changes
# and INSERT new nodes and DELETE old nodes (excluding AMPRGW)
else
iptables -L ipipfilter -n | grep ACCEPT | fgrep -v $AMPRGW | \
sed -e 's/.*-- //' -e 's/ .*//' | sort | diff - $gwfile | \
while read d ip
do
case "$d" in
">")
iptables -I ipipfilter -s $ip -j ACCEPT
;;
"<")
iptables -D ipipfilter -s $ip -j ACCEPT
;;
*)
;;
esac
done
fi
# Delete /tmp/gw when done
rm -f $gwfile
# The full pathname of this script /usr/local/sbin/load_ipipfilter is passed with the new -x
# option to ampr-ripd. It will load the entire filter the first time, and later it will only update
# the filters that have changed. It is required that the -s option is passed as well, so the
# encap.txt file is created by ampr-ripd.
Static IPENCAP Filtering of AMPR Nodes
To enable input of IPENCAP (IP Protocol Number 4)
Note:
- This rule (the dynamic rule above, or the ipset rules) is required for other AMPR nodes to initiate inbound traffic to your node.
iptables -t filter -I INPUT -p 4 -i <INTERFACE OF YOUR WAN> -j ACCEPT
If your AMPR node is downstream, you will create an INPUT and DNAT forward rule to the destination LAN IP of your AMPR node.
To enable receipt of RIP44
iptables -t filter -I INPUT -p udp -s 44.0.0.1 --sport 520 -d 224.0.0.9 --dport 520 -i tunl0 -j ACCEPT
Masquerade LAN Subnets to AMPRNet
- In this instance, eth1 is your 192.168.1.0/24 LAN - (thanks to Brian, N1URO)
See: https://n1uro.ampr.org/linuxconf/44nat.html
# NAT setup iptables -t nat -A POSTROUTING -s 192.168.0/24 -o tunl0 -j MASQUERADE -d 44.0.0.0/8 iptables -A FORWARD -s 192.168.1/22 -i eth1 -o tunl0 -m state --state RELATED,ESTABLISHED -j ACCEPT -d 44.0.0.0/8 iptables -A FORWARD -s 192.168.1/22 -i eth1 -o tunl0 -j ACCEPT -d 44.0.0.0/8
ipset
General Bogon rules using ipset - see: https://en.wikipedia.org/wiki/Bogon_filtering
#######################BOGON FILTER ######################## ipset create bogons hash:net # BOGON LIST # SEE http://www.team-cymru.org/Services/Bogons/bogon-bn-nonagg.txt ipset -A bogons 0.0.0.0/8 ipset -A bogons 10.0.0.0/8 ipset -A bogons 100.64.0.0/10 ipset -A bogons 127.0.0.0/8 ipset -A bogons 169.254.0.0/16 ipset -A bogons 172.16.0.0/12 ipset -A bogons 192.0.0.0/24 ipset -A bogons 192.0.2.0/24 ipset -A bogons 192.168.0.0/16 ipset -A bogons 198.18.0.0/15 ipset -A bogons 198.51.100.0/24 ipset -A bogons 203.0.113.0/24 ipset -A bogons 224.0.0.0/4 ipset -A bogons 240.0.0.0/4 # Block of your own AMPRNet Subnet # ipset -A bogons 44.xxx.xxx.xxx/xx # Block of Test AMPRNet Subnet # ipset -A bogons 44.128.0.0/16
(you can optionally block your subnet)
Dynamic IPENCAP Filtering of AMPR Nodes (using ipset)
To enable dynamic filtering of IPENCAP (IP Protocol Number 4)
REQUIRED: ampr-ripd (using the -x and -d arguments) and the ipset package.
#!/bin/sh
# load encap.txt into ipipfilter list
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
cd /var/lib/ampr-ripd || exit 1
ipset -N ipipfilter hash:ip 2>/dev/null
ipset flush ipipfilter
ipset -A ipipfilter <AMPRGW>
grep addprivate encap.txt | sed -e 's/.*encap //' | sort -u | while read ip
do
ipset -A ipipfilter $ip
done
Microtik
OpenBSD
See the Instructions for Setting up a gateway on OpenBSD.
OpenBSD comes with a robust, flexible and highly performant firewall called "PF" that works well on AMPRNet. See https://www.openbsd.org/faq/pf/ for more information.
OpenWrt
See: iptables and ipset (above), and the Instructions for setting up a gateway on OpenWRT.
- the Bogon ipset script is added to System > Startup on the web GUI - or into the Unified Configuration Interface (UCI) file /etc/rc.local
- iptables-based scripts are entered at Network > Firewall > Custom Firewall on the LuCI web GUI interface - or into the Unified Configuration Interface (UCI) file /etc/firewall.user
- ipset-based rules are entered on the command line - into the Unified Configuration Interface (UCI) file /etc/config/firewall (OpenWrt syntax must be used in this file!)
- MSS Clamping is enabled in the Firewall Section, you should enable this on both the AMPRLAN and AMPRWAN interfaces
Adding Bogon drop rule to OpenWrt (using ipset)
# in /etc/config/firewall config rule option name 'Drop-Bogons_In_AMPRWAN' option family 'ipv4' option proto 'all' option src 'amprwan' option target 'DROP' option extra '-m set --match-set bogons src'
Adding IPENCAP Filtering of AMPR Nodes to OpenWrt (using ipset)
# in /etc/config/firewall config rule option target 'ACCEPT' option src 'wan' option family 'ipv4' option proto '4' option name 'Allow-AMPR_IPENCAP' option extra '-m set --match-set ipipfilter src'
Adding ICMP Filtering of AMPR Nodes to OpenWrt (using ipset)
# in /etc/config/firewall config rule option target 'ACCEPT' option family 'ipv4' option proto 'icmp' list icmp_type 'echo-request' option src '*' option extra '-m set --match-set ipipfilter src' option name 'Ping_fromIPENCAPS'