I am trying to set up a good "template" for iptables. What I have come up with is below, which I admit has been cobbled together from examples and what I've read.
I need to keep open SSH, FTP, HTTP(S), DNS, MySQL and outgoing mail generated by PHP. Also let the server login to an outside SMTP account to send mail when needed. I do need to let MySQL be connected to by another outside server under our control, which is why port 3306 is open.
Are there any glaring mistakes in the below? Any advice would be appreciated.
Code: #!/bin/bash
##########################################################################################################################################
# IPTABLES SETTINGS
##########################################################################################################################################
# Clear old Rules
iptables -F # Flush all current rules from iptables
# Allow SSH connections on tcp port 22
# This is essential when working on remote servers via SSH to prevent locking yourself out of the system
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
# Set default policies for INPUT, FORWARD and OUTPUT chains
iptables -P INPUT DROP # Set default chain policies to DROP
iptables -P FORWARD DROP # Set default chain policies to DROP
iptables -P OUTPUT ACCEPT # Set default chain policies to ACCEPT
# Set access for localhost (loopback)
iptables -A INPUT -i lo -j ACCEPT # Allow loopback access from INPUT
iptables -A OUTPUT -o lo -j ACCEPT # Allow loopback access from OUTPUT
# Allow Established Connections (prevent being dropped from SSH as these commands are typed)
iptables -A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
# BLACKLIST IP's
# iptables -A INPUT -s "BLOCK_THIS_IP" -j DROP # Block a specific ip-address
# iptables -A INPUT -s "BLOCK_THIS_IP" -j DROP # Block a specific ip-address
# iptables -A INPUT -s "BLOCK_THIS_IP" -j DROP # Block a specific ip-address
# iptables -A INPUT -s "BLOCK_THIS_IP" -j DROP # Block a specific ip-address
# WHITELIST IP's
iptables -A INPUT -s 127.0.0.1/32 -j ACCEPT # Allow Anything from localhost
# iptables -A INPUT -s "ALLOW_THIS_IP"/32 -j ACCEPT # Allow Anything from KeyServer
# ALLOWED SERVICES
iptables -A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT # PORT 22 SSH
iptables -A OUTPUT -o eth0 -p tcp --sport 25 -m state --state ESTABLISHED -j ACCEPT # PORT 25 SMTP - Allow connections to outbound
iptables -A OUTPUT -p udp -o eth0 --dport 53 -j ACCEPT # PORT 53 DNS - Allow connections to outbound
iptables -A INPUT -p tcp -m tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT # PORT 80 HTTPD - Allow connections from anywhere
iptables -A INPUT -p tcp --dport 80 -m limit --limit 50/minute --limit-burst 200 -j ACCEPT # PORT 80 HTTPD - Rate Limit from outside (prevent DOS attacks)
iptables -A INPUT -p tcp -m tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT # PORT 443 SSL - Allow connections from anywhere
iptables -A INPUT -p tcp -m tcp --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT # PORT 3306 MySQL - Allow connections from anywhere
# FTP
iptables -A INPUT -p tcp -m state --state NEW,ESTABLISHED -m tcp --dport 65501 -j ACCEPT # PORT 65501 FTP
iptables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -m tcp --sport 65501 -j ACCEPT # PORT 65500 FTP (outgoing messages)
# Active
iptables -A INPUT -p tcp -m state --state NEW,ESTABLISHED -m tcp --dport 20 -j ACCEPT
iptables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED,RELATED -m tcp --sport 20 -j ACCEPT
# Passive
iptables -A INPUT -p tcp -m state --state NEW,RELATED,ESTABLISHED -m tcp --sport 1024: --dport 1024: -j ACCEPT
iptables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -m tcp --sport 1024: --dport 1024: -j ACCEPT
# PING - Allow ICMP (ping) packets
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT
iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT
# Validate packets
iptables -A INPUT -m state --state INVALID -j DROP # Drop invalid packets
iptables -A FORWARD -m state --state INVALID -j DROP # Drop invalid packets
iptables -A OUTPUT -m state --state INVALID -j DROP # Drop invalid packets
iptables -A INPUT -p tcp -m tcp --tcp-flags SYN,FIN SYN,FIN -j DROP # Drop TCP - SYN,FIN packets
iptables -A INPUT -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP # Drop TCP - SYN,RST packets
# Reject Invalid networks (Spoof)
iptables -A INPUT -s 10.0.0.0/8 -j DROP # (Spoofed network)
iptables -a INPUT -s 192.0.0.1/24 -j DROP # (Spoofed network)
iptables -A INPUT -s 169.254.0.0/16 -j DROP # (Spoofed network)
iptables -A INPUT -s 172.16.0.0/12 -j DROP # (Spoofed network)
iptables -A INPUT -s 224.0.0.0/4 -j DROP # (Spoofed network)
iptables -A INPUT -d 224.0.0.0/4 -j DROP # (Spoofed network)
iptables -A INPUT -s 240.0.0.0/5 -j DROP # (Spoofed network)
iptables -A INPUT -d 240.0.0.0/5 -j DROP # (Spoofed network)
iptables -A INPUT -s 0.0.0.0/8 -j DROP # (Spoofed network)
iptables -A INPUT -d 0.0.0.0/8 -j DROP # (Spoofed network)
iptables -A INPUT -d 239.255.255.0/24 -j DROP # (Spoofed network)
iptables -A INPUT -d 255.255.255.255 -j DROP # (Spoofed network)
# CHAINS
# FTP_BRUTE CHAIN
iptables -A INPUT -p tcp -m multiport --dports 20,21 -m state --state NEW -m recent --set --name FTP_BRUTE
iptables -A INPUT -p tcp -m multiport --dports 20,21 -m state --state NEW -m recent --update --seconds 60 --hitcount 4 --rttl --name FTP_BRUTE -j DROP
# SYNFLOOD CHAIN
iptables -A INPUT -m state --state NEW -p tcp -m tcp --syn -m recent --name SYNFLOOD --set
iptables -A INPUT -m state --state NEW -p tcp -m tcp --syn -m recent --name SYNFLOOD --update --seconds 1 --hitcount 20 -j DROP
# Logging CHAIN
iptables -N LOGGING # Create `LOGGING` chain for logging denied packets
iptables -A INPUT -j LOGGING # Create `LOGGING` chain for logging denied packets
iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables Packet Dropped: " --log-level 6 # Log denied packets to /var/log/messages
iptables -A LOGGING -j DROP # Drop everything
# List rules
iptables -L -v
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