#!/bin/sh

# adblocker.sh - by Todd Stein ([email protected]), Saturday, October 25, 2014
# for use on routers running OpenWRT firmware

# Periodically download lists of known ad and malware servers, and prevents traffic from being sent to them.
# This is a complete rewrite of a script originally written by teffalump (https://gist.github.com/teffalump/7227752).


HOST_LISTS="
	http://adaway.org/hosts.txt
	http://www.malwaredomainlist.com/hostslist/hosts.txt
	http://www.mvps.org/winhelp2002/hosts.txt
	http://pgl.yoyo.org/adservers/serverlist.php?hostformat=hosts&showintro=0&startdate%5Bday%5D=&startdate%5Bmonth%5D=&star
"

BLOCKLIST=/tmp/adblocker_hostlist
BLACKLIST=/etc/adblocker_blacklist
WHITELIST=/etc/adblocker_whitelist

# get script's absolute path and escape spaces
cd "${0%/*}"
SCRIPT_NAME="$PWD/${0##*/}"
SCRIPT_NAME="${SCRIPT_NAME// /' '}"
cd "$OLDPWD"

# await internet connectivity before proceeding (in case rc.local executes this script before connectivity is achieved)
until ping -c1 -w3 google.com || ping -c1 -w3 yahoo.com; do
	sleep 5
done &>/dev/null

# initialize block list
>"$BLOCKLIST"

# grab blacklisted domains if any have been specified
[ -s "$BLACKLIST" ] && awk '/^[^#]/ { print "0.0.0.0",$1 }' "$BLACKLIST" >>"$BLOCKLIST"

# grab host lists from the internet
wget -qO- $HOST_LISTS | sed -rn 's/^(127.0.0.1|0.0.0.0)/0.0.0.0/p' | awk '{ print $1,$2 }' | sort -uk2 >>"$BLOCKLIST"

# remove any whitelisted domains from the block list
if [ -s "$WHITELIST" ]; then
	# create a pipe-delimited list of all non-commented words in whitelist
	white_listed_regex=`echo \`grep -o '^[^#]\+' "$WHITELIST"\` | tr ' ' '|'`
	sed -ri "/$white_listed_regex/d" "$BLOCKLIST"
fi

# add IPv6 blocking
sed -ri 's/([^ ]+)$/\1\n::      \1/' "$BLOCKLIST"

# add block list to dnsmasq config if it's not already there
if ! uci get dhcp.@dnsmasq[0].addnhosts | grep -q "$BLOCKLIST"; then
	uci add_list dhcp.@dnsmasq[0].addnhosts="$BLOCKLIST" && uci commit
fi

# restart dnsmasq service
/etc/init.d/dnsmasq restart

# carefully add script to /etc/rc.local if it's not already there
if ! grep -Fq "$SCRIPT_NAME" /etc/rc.local; then
	# using awk and cat ensures that no symlinks (if any exist) are clobbered by BusyBox's feature-poor sed.
	awk -v command="$SCRIPT_NAME" '
		! /^exit( 0)?$/ {
			print $0
		}
		/^exit( 0)?$/ {
			print command "\n" $0
			entry_added=1
		}
		END {
			if (entry_added != 1) {
				print command
			}
		}' /etc/rc.local >/tmp/rc.local.new
	cat /tmp/rc.local.new >/etc/rc.local
	rm -f /tmp/rc.local.new
fi

# add script to root's crontab if it's not already there
grep -Fq "$SCRIPT_NAME" /etc/crontabs/root 2>/dev/null || cat >>/etc/crontabs/root <<-:EOF:
	# Download updated ad and malware server lists every Tuesday at 3 AM
	0 3 * * 2 /bin/sh $SCRIPT_NAME
:EOF: