Fincer
/
linux-server-setup
mirror of https://github.com/Fincer/linux-server-setup


###############################

# SIMPLE FIREWALL RULES FOR IPTABLES

#

# By Pekka Helenius (~Fincer), 2018

#

# These rules are intended to be used

# without UFW. If you have additional

# firewall settings in your system/iptables,

# take care adapting these rules in to your

# current firewall ruleset.

#

# I do not take responsibility of breaking

# your working firewall configuration!

#

############

#

# The rules in this file do the following:

#

# A) do not respond to incoming ping requests

# Can be used as a replacement for sysctl 'net.ipv4.icmp_echo_ignore_all=1' setting

#

# B) drop all incoming traffic by default, except for

# SSH, HTTP and HTTPS protocols

#

# C) start dropping packets if connection cycle is too intense

# from one client. This setting may be useful against port scanners.

#

# Ruleset C) by Anthony Maro:

# https://www.ossramblings.com/using_iptables_rate_limiting_to_prevent_portscans

#

############

#

# INSTALLATION

#

# NOTE: Intended to be used without UFW or any other

# firewall settings!!

#

# 1) Recommended: Remove existing firewall front-ends such as UFW from your system

#

# 2) Delete all previous firewall rules by issuing

#    sudo iptables --flush && sudo iptables --delete-chain

#

# 3) Check output of 'iptables -S'. It should be

#    -P INPUT ACCEPT

#    -P FORWARD ACCEPT

#    -P OUTPUT ACCEPT

#

# 4) In this file, change SSH, HTTP and HTTPS port numbers to fit your server environment

#

#    Default values are:

#

#        SSH: 22

#        HTTP: 80

#        HTTPS: 443

#

# Default setting for C) is 10 maximum connection attempts in 30 seconds

# Adapt the values to your server environment.

#

# 5) Save this file to /etc/iptables/iptables.rules

#

# 6) Check that it is used by 'iptables-restore' command

#

# In systemd environments, check the value of 'ExecStart' and 'ExecReload'

# in file /lib/systemd/system/iptables.service. The entries should be as follows:

#

#    ExecStart=/usr/bin/iptables-restore /etc/iptables/iptables.rules

#    ExecReload=/usr/bin/iptables-restore /etc/iptables/iptables.rules

#

# 7) Once you have double-checked that the parameters in this file are correct (step 4), run

#    sudo iptables-restore /etc/iptables/iptables.rules

#    sudo systemctl enable iptables && sudo systemctl start iptables

#

# 8) Check that the rules have been applied:

#    sudo iptables -S

#

#

###############################

# USEFUL LINKS

#

# https://www.thegeekstuff.com/scripts/iptables-rules

# https://gist.github.com/thomasfr/9712418

#

###############################

#

# BEGINNING OF FIREWALL RULES

#


*filter


###############################

# DEFAULT POLICY FOR THIS CHAIN - DROP ALL INPUT TRAFFIC

#

# THIS IS A DANGEROUS SETTING. IF YOU DROP ALL INCOMING

# CONNECTIONS, MAKE SURE YOU HAVE ACCEPTED AT LEAST SSH CONNECTION INPUT BELOW

# OTHERWISE YOU WILL BE LOCKED OUT FROM THE SERVER!

#

# DO NOT USE 'REJECT' BECAUSE IT GIVES A RESPONSE TO A HOSTILE CLIENTS (PORT SCANNERS)

# INSTEAD, DROP INCOMING PACKETS AND DO NOT GIVE RESPONSE AT ALL

#


-P INPUT DROP


###############################

# WE ARE NOT A ROUTER, WE DROP ALL (NON-EXISTENT) FORWARD CONNECTIONS

#


-P FORWARD DROP


###############################

# BY DEFAULT, ALL OUTGOING TRAFFIC FROM THE SERVER IS ACCEPTED

#


-P OUTPUT ACCEPT


###############################

# DROP ALL INCOMING PING REQUESTS

#


-A INPUT -p icmp --icmp-type echo-request -j DROP


###############################

# ALLOW LOOPBACK CONNECTIONS

#


-A INPUT -i lo -j ACCEPT

#-A OUTPUT -o lo -j ACCEPT


###############################

# ALLOW INCOMING SSH CONNECTIONS

#


-A INPUT -p tcp --dport 22 -m state --state NEW -j ACCEPT

#-A OUTPUT -p tcp --sport 22 -m state --state NEW -j ACCEPT


###############################

# ALLOW INCOMING HTTP/HTTPS CONNECTIONS

#


-A INPUT -p tcp -m multiport --dports 80,443 -m state --state NEW -j ACCEPT

#-A OUTPUT -p tcp -m multiport --sports 80,443 -m state --state NEW -j ACCEPT


###############################

# ALLOW ESTABLISHED AND RELATED CONNECTIONS

#


-A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

#-A OUTPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT


###############################

# RULESET C)

#

# IF 10 NEW CONNECTIONS TO ANY PORT WITHIN 30 SECONDS IS REQUESTED BY A CLIENT, START DROPPING PACKETS FOR THE CLIENT

#

# SHOULD FREEZE NMAP AND OTHER PORT SCANNERS

#

# Source: https://www.ossramblings.com/using_iptables_rate_limiting_to_prevent_portscans


-A INPUT -i $IFACE -p tcp -m state --state NEW -m recent --set --name DEFAULT --mask 255.255.255.255 --rsource

-A INPUT -i $IFACE -p tcp -m state --state NEW -m recent --update --seconds 30 --hitcount 10 --name DEFAULT --mask 255.255.255.255 --rsource -j DROP


###############################


COMMIT


								# END OF FIREWALL RULES