#!/bin/sh

# minifirewall is shellscripts for easy firewalling on a standalone server
# we used netfilter/iptables http://netfilter.org/ designed for recent Linux kernel
# See https://gitea.evolix.org/evolix/minifirewall

# Copyright (c) 2007-2020 Evolix
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 3
# of the License.

# Description
# script for standalone server

# Start or stop minifirewall
#

### BEGIN INIT INFO
# Provides:          minfirewall
# Required-Start:
# Required-Stop:
# Should-Start:      $network $syslog $named
# Should-Stop:       $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: start and stop the firewall
# Description:       Firewall designed for standalone server
### END INIT INFO

DESC="minifirewall"
NAME="minifirewall"


# Variables configuration
#########################

# iptables paths
IPT=/sbin/iptables
IPT6=/sbin/ip6tables

# TCP/IP variables
LOOPBACK='127.0.0.0/8'
CLASSA='10.0.0.0/8'
CLASSB='172.16.0.0/12'
CLASSC='192.168.0.0/16'
CLASSD='224.0.0.0/4'
CLASSE='240.0.0.0/5'
ALL='0.0.0.0'
BROAD='255.255.255.255'
PORTSROOT='0:1023'
PORTSUSER='1024:65535'

chain_exists()
{
    local chain_name="$1" ; shift
    [ $# -eq 1 ] && local intable="--table $1"
    iptables $intable -nL "$chain_name" >/dev/null 2>&1
}

# Configuration
oldconfigfile="/etc/firewall.rc"
configfile="/etc/default/minifirewall"

IPV6=$(grep "IPV6=" /etc/default/minifirewall | awk -F '=' -F "'" '{print $2}')
DOCKER=$(grep "DOCKER=" /etc/default/minifirewall | awk -F '='  -F "'" '{print $2}')
INT=$(grep "INT=" /etc/default/minifirewall | awk -F '='  -F "'" '{print $2}')

case "$1" in
 start)

     echo "Start IPTables rules..."

# Stop and warn if error!
set -e
trap 'echo "ERROR in minifirewall configuration (fix it now!) or script manipulation (fix yourself)." ' INT TERM EXIT


# sysctl network security settings
##################################

# Don't answer to broadcast pings
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

# Ignore bogus ICMP responses
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses

# Disable Source Routing
for i in /proc/sys/net/ipv4/conf/*/accept_source_route; do
echo 0 > $i
done

# Enable TCP SYN cookies to avoid TCP-SYN-FLOOD attacks
# cf http://cr.yp.to/syncookies.html
echo 1 > /proc/sys/net/ipv4/tcp_syncookies

# Disable ICMP redirects
for i in /proc/sys/net/ipv4/conf/*/accept_redirects; do
echo 0 > $i
done

for i in /proc/sys/net/ipv4/conf/*/send_redirects; do
echo 0 > $i
done

# Enable Reverse Path filtering : verify if responses use same network interface
for i in /proc/sys/net/ipv4/conf/*/rp_filter; do
echo 1 > $i
done

# log des paquets avec adresse incoherente
for i in /proc/sys/net/ipv4/conf/*/log_martians; do
echo 1 > $i
done

# IPTables configuration
########################

$IPT -N LOG_DROP
$IPT -A LOG_DROP -j LOG  --log-prefix '[IPTABLES DROP] : '
$IPT -A LOG_DROP -j DROP
$IPT -N LOG_ACCEPT
$IPT -A LOG_ACCEPT -j LOG  --log-prefix '[IPTABLES ACCEPT] : '
$IPT -A LOG_ACCEPT -j ACCEPT

if test -f $oldconfigfile; then
    echo "$oldconfigfile is deprecated, rename to $configfile" >&2
    exit 1
fi

if ! test -f $configfile; then
    echo "$configfile does not exist" >&2
    exit 1
fi

tmpfile=`mktemp`
. $configfile 2>$tmpfile >&2
if [ -s $tmpfile ]; then
        echo "$configfile returns standard or error output (see below). Stopping." >&2
        cat $tmpfile
        exit 1
fi
rm $tmpfile

# Trusted ip addresses
$IPT -N ONLYTRUSTED
$IPT -A ONLYTRUSTED -j LOG_DROP
for x in $TRUSTEDIPS
    do
        $IPT -I ONLYTRUSTED -s $x -j ACCEPT
    done

# Privilegied ip addresses
# (trusted ip addresses *are* privilegied)
$IPT -N ONLYPRIVILEGIED
$IPT -A ONLYPRIVILEGIED -j ONLYTRUSTED
for x in $PRIVILEGIEDIPS
    do
        $IPT -I ONLYPRIVILEGIED -s $x -j ACCEPT
    done

# Chain for restrictions (blacklist IPs/ranges)
$IPT -N NEEDRESTRICT

# We allow all on loopback interface
$IPT -A INPUT -i lo -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A INPUT -i lo -j ACCEPT
# if OUTPUTDROP
$IPT -A OUTPUT -o lo -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -o lo -j ACCEPT

# We avoid "martians" packets, typical when W32/Blaster virus
# attacked windowsupdate.com and DNS was changed to 127.0.0.1
# $IPT -t NAT -I PREROUTING -s $LOOPBACK -i ! lo -j DROP
$IPT -A INPUT -s $LOOPBACK ! -i lo -j DROP


if [ "$DOCKER" = "on" ]; then

    $IPT -N MINIFW-DOCKER-TRUSTED
    $IPT -A MINIFW-DOCKER-TRUSTED -j DROP

    $IPT -N MINIFW-DOCKER-PRIVILEGED
    $IPT -A MINIFW-DOCKER-PRIVILEGED -j MINIFW-DOCKER-TRUSTED
    $IPT -A MINIFW-DOCKER-PRIVILEGED -j RETURN

    $IPT -N MINIFW-DOCKER-PUB
    $IPT -A MINIFW-DOCKER-PUB -j MINIFW-DOCKER-PRIVILEGED
    $IPT -A MINIFW-DOCKER-PUB -j RETURN

    # Flush DOCKER-USER if exist, create it if absent
    if chain_exists 'DOCKER-USER'; then
        $IPT -F DOCKER-USER
    else
        $IPT -N DOCKER-USER
    fi;

    # Pipe new connection through MINIFW-DOCKER-PUB
    $IPT -A DOCKER-USER -i $INT -m state  --state NEW -j MINIFW-DOCKER-PUB
    $IPT -A DOCKER-USER -j RETURN

fi


# Local services restrictions
#############################

# Allow services for $INTLAN (local server or local network)
$IPT -A INPUT -s $INTLAN -j ACCEPT

# Enable protection chain for sensible services
for x in $SERVICESTCP1p
    do
        $IPT -A INPUT -p tcp --dport $x -j NEEDRESTRICT
    done

for x in $SERVICESUDP1p
    do
        $IPT -A INPUT -p udp --dport $x -j NEEDRESTRICT
    done

# Public service
for x in $SERVICESTCP1
    do
        $IPT -A INPUT -p tcp --dport $x -j ACCEPT
        [ "$IPV6" != "off" ] && $IPT6 -A INPUT -p tcp --dport $x -j ACCEPT
    done

for x in $SERVICESUDP1
    do
        $IPT -A INPUT -p udp --dport $x -j ACCEPT
        [ "$IPV6" != "off" ] && $IPT6 -A INPUT -p udp --dport $x -j ACCEPT
    done

# Privilegied services
for x in $SERVICESTCP2
    do
        $IPT -A INPUT -p tcp --dport $x -j ONLYPRIVILEGIED
    done

for x in $SERVICESUDP2
    do
        $IPT -A INPUT -p udp --dport $x -j ONLYPRIVILEGIED
    done

# Private services
for x in $SERVICESTCP3
    do
        $IPT -A INPUT -p tcp --dport $x -j ONLYTRUSTED
    done

for x in $SERVICESUDP3
    do
        $IPT -A INPUT -p udp --dport $x -j ONLYTRUSTED
    done


if [ "$DOCKER" = "on" ]; then

    # Public services defined in SERVICESTCP1 & SERVICESUDP1
    for dstport in $SERVICESTCP1
        do
            $IPT -I MINIFW-DOCKER-PUB -p tcp --dport "$dstport" -j RETURN
        done

    for dstport in $SERVICESUDP1
        do
            $IPT -I MINIFW-DOCKER-PUB -p udp --dport "$dstport" -j RETURN
        done

    # Privileged services (accessible from privileged & trusted IPs)
    for dstport in $SERVICESTCP2
        do
            for srcip in $PRIVILEGIEDIPS
                do
                    $IPT -I MINIFW-DOCKER-PRIVILEGED -p tcp -s "$srcip" --dport "$dstport" -j RETURN
                done

            for srcip in $TRUSTEDIPS
                do
                    $IPT -I MINIFW-DOCKER-PRIVILEGED -p tcp -s "$srcip" --dport "$dstport" -j RETURN
                done
        done

    for dstport in $SERVICESUDP2
        do
            for srcip in $PRIVILEGIEDIPS
                do
                    $IPT -I MINIFW-DOCKER-PRIVILEGED -p udp -s "$srcip" --dport "$dstport" -j RETURN
                done

            for srcip in $TRUSTEDIPS
                do
                    $IPT -I MINIFW-DOCKER-PRIVILEGED -p udp -s "$srcip" --dport "$dstport" -j RETURN
                done
        done

    # Trusted services (accessible from trusted IPs)
    for dstport in $SERVICESTCP3
        do
            for srcip in $TRUSTEDIPS
                do
                    $IPT -I MINIFW-DOCKER-TRUSTED -p tcp -s "$srcip" --dport "$dstport" -j RETURN
                done
        done

    for dstport in $SERVICESUDP3
        do
            for srcip in $TRUSTEDIPS
                do
                    $IPT -I MINIFW-DOCKER-TRUSTED -p udp -s "$srcip" --dport "$dstport" -j RETURN
                done
        done
fi

# External services
###################

# DNS authorizations
for x in $DNSSERVEURS
    do
        $IPT -A INPUT -p tcp ! --syn --sport 53 --dport $PORTSUSER -s $x -j ACCEPT
        $IPT -A INPUT -p udp --sport 53 --dport $PORTSUSER -s $x -m state --state ESTABLISHED,RELATED -j ACCEPT
        $IPT -A OUTPUT -o $INT -p udp -d $x --dport 53 --match state --state NEW -j ACCEPT
    done

# HTTP (TCP/80) authorizations
for x in $HTTPSITES
    do
        $IPT -A INPUT -p tcp ! --syn --sport 80 --dport $PORTSUSER -s $x -j ACCEPT
    done

# HTTPS (TCP/443) authorizations
for x in $HTTPSSITES
    do
        $IPT -A INPUT -p tcp ! --syn --sport 443 --dport $PORTSUSER -s $x -j ACCEPT
    done

# FTP (so complex protocol...) authorizations
for x in $FTPSITES
    do
        # requests on Control connection
        $IPT -A INPUT -p tcp ! --syn --sport 21 --dport $PORTSUSER -s $x -j ACCEPT
        # FTP port-mode on Data Connection
        $IPT -A INPUT -p tcp --sport 20 --dport $PORTSUSER -s $x -j ACCEPT
        # FTP passive-mode on Data Connection
        # WARNING, this allow all connections on TCP ports > 1024
        $IPT -A INPUT -p tcp ! --syn --sport $PORTSUSER --dport $PORTSUSER -s $x -j ACCEPT
    done

# SSH authorizations
for x in $SSHOK
        do
                $IPT -A INPUT -p tcp ! --syn --sport 22 -s $x -j ACCEPT
        done

# SMTP authorizations
for x in $SMTPOK
    do
        $IPT -A INPUT -p tcp ! --syn --sport 25 --dport $PORTSUSER -s $x -j ACCEPT
    done

# secure SMTP (TCP/465 et TCP/587) authorizations
for x in $SMTPSECUREOK
    do
        $IPT -A INPUT -p tcp ! --syn --sport 465 --dport $PORTSUSER -s $x -j ACCEPT
        $IPT -A INPUT -p tcp ! --syn --sport 587 --dport $PORTSUSER -s $x -j ACCEPT
    done

# NTP authorizations
for x in $NTPOK
        do
            $IPT -A INPUT -p udp --sport 123 -s $x -j ACCEPT
            $IPT -A OUTPUT -o $INT -p udp -d $x --dport 123 --match state --state NEW -j ACCEPT
        done

# Always allow ICMP
$IPT -A INPUT -p icmp -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A INPUT -p icmpv6 -j ACCEPT


# IPTables policy
#################

# by default DROP INPUT packets
$IPT -P INPUT DROP
[ "$IPV6" != "off" ] && $IPT6 -P INPUT DROP

# by default, no FORWARING (deprecated for Virtual Machines)
#echo 0 > /proc/sys/net/ipv4/ip_forward
#$IPT -P FORWARD DROP
#$IPT6 -P FORWARD DROP

# by default allow OUTPUT packets... but drop UDP packets (see OUTPUTDROP to drop OUTPUT packets)
$IPT -P OUTPUT ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -P OUTPUT ACCEPT
$IPT -A OUTPUT -o $INT -p udp --dport 33434:33523 --match state --state NEW -j ACCEPT
$IPT -A OUTPUT -p udp --match state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -p udp -j DROP
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -o $INT -p udp --dport 33434:33523 --match state --state NEW -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -p udp --match state --state ESTABLISHED,RELATED -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -p udp -j DROP

trap - INT TERM EXIT

    echo "...starting IPTables rules is now finish : OK"
  ;;

  stop)

    echo "Flush all rules and accept everything..."

    # Delete all rules
    $IPT -F INPUT
    $IPT -F OUTPUT
    $IPT -F LOG_DROP
    $IPT -F LOG_ACCEPT
    $IPT -F ONLYTRUSTED
    $IPT -F ONLYPRIVILEGIED
    $IPT -F NEEDRESTRICT
    [ "$DOCKER" = "off" ] && $IPT -t nat -F
    $IPT -t mangle -F
    [ "$IPV6" != "off" ] && $IPT6 -F INPUT
    [ "$IPV6" != "off" ] && $IPT6 -F OUTPUT

    if [ "$DOCKER" = "on" ]; then
        $IPT -F DOCKER-USER
        $IPT -A DOCKER-USER -j RETURN

        $IPT -F MINIFW-DOCKER-PUB
        $IPT -X MINIFW-DOCKER-PUB
        $IPT -F MINIFW-DOCKER-PRIVILEGED
        $IPT -X MINIFW-DOCKER-PRIVILEGED
        $IPT -F MINIFW-DOCKER-TRUSTED
        $IPT -X MINIFW-DOCKER-TRUSTED

    fi

    # Accept all
    $IPT -P INPUT ACCEPT
    $IPT -P OUTPUT ACCEPT
    [ "$IPV6" != "off" ] && $IPT6 -P INPUT ACCEPT
    [ "$IPV6" != "off" ] && $IPT6 -P OUTPUT ACCEPT
    #$IPT -P FORWARD ACCEPT
    #$IPT -t nat -P PREROUTING ACCEPT
    #$IPT -t nat -P POSTROUTING ACCEPT

    # Delete non-standard chains
    $IPT -X LOG_DROP
    $IPT -X LOG_ACCEPT
    $IPT -X ONLYPRIVILEGIED
    $IPT -X ONLYTRUSTED
    $IPT -X NEEDRESTRICT

    echo "...flushing IPTables rules is now finish : OK"
  ;;

  status)

    $IPT -L -n -v --line-numbers
    $IPT -t nat -L -n -v --line-numbers
    $IPT -t mangle -L -n -v --line-numbers
    $IPT6 -L -n -v --line-numbers
    $IPT6 -t mangle -L -n -v --line-numbers
  ;;

  reset)

    echo "Reset all IPTables counters..."

    $IPT -Z
    $IPT -t nat -Z
    $IPT -t mangle -Z
    [ "$IPV6" != "off" ] && $IPT6 -Z
    [ "$IPV6" != "off" ] && $IPT6 -t mangle -Z

    echo "...reseting IPTables counters is now finish : OK"
  ;;

  restart)

    $0 stop
    $0 start
  ;;

  *)

    echo "Usage: $0 {start|stop|restart|status|reset|squid}"
    exit 1
esac

exit 0