OpenWRT - firewall.user Script IP blacklisting

#!/bin/sh

# IP blacklisting script for Linux servers
# Pawel Krawczyk 2014-2015
# documentation https://github.com/kravietz/blacklist-scripts

# Emerging Threats lists offensive IPs such as botnet command servers
urls="http://rules.emergingthreats.net/fwrules/emerging-Block-IPs.txt"
# Blocklist.de collects reports from fail2ban probes, listing password brute-forces, scanners and other offenders
urls="$urls https://www.blocklist.de/downloads/export-ips_all.txt"
# badips.com_ssh, from score 0 up
urls="$urls http://www.badips.com/get/list/ssh/0"
# badips.com_http, from score 0 up
urls="$urls http://www.badips.com/get/list/http/0"
# badips.com_nginx-proxy, from score 0 up
urls="$urls https://www.badips.com/get/list/nginxproxy/0"
# badips.com_ftp, from score 0 up
urls="$urls http://www.badips.com/get/list/ftp/0"
# badips.com_squid-proxy, from score 0 up
urls="$urls https://www.badips.com/get/list/squid/0"
# badips.com_dns, from score 0 up
urls="$urls http://www.badips.com/get/list/dns/0"
# CustomList, hosted on dropbox , my sites or whatever...
urls="$urls http://examples.com/ipblocklist/ipblocklist.txt"

blocklist_chain_name=blocklists

if [ -z "$(which ipset 2>/dev/null)" ]; then
    echo "Cannot find ipset"
    echo "Run \"apt-get install ipset\" or \"yum install ipset\""
    exit 1
fi

if [ -z "$(which curl 2>/dev/null)" ]; then
    echo "Cannot find curl"
    echo "Run \"apt-get install curl\" or \"yum install curl\""
    exit 1
fi

if [ "$(which uci 2>/dev/null)" ]; then
    # we're on OpenWRT
    wan_iface=$(uci get network.wan.ifname)
    IN_OPT="-i $wan_iface"
    INPUT=input_rule
    FORWARD=forwarding_rule
    COMPRESS_OPT=""
else
    COMPRESS_OPT="--compressed"
    INPUT=INPUT
    FORWARD=FORWARD
fi


# create main blocklists chain
if ! iptables -L | grep -q "Chain ${blocklist_chain_name}"; then
    iptables -N ${blocklist_chain_name}
fi

# inject references to blocklist in the beginning of input and forward chains
if ! iptables -L ${INPUT} | grep -q ${blocklist_chain_name}; then
  iptables -I ${INPUT} 1 ${IN_OPT} -j ${blocklist_chain_name}
fi
if ! iptables -L ${FORWARD} | grep -q ${blocklist_chain_name}; then
  iptables -I ${FORWARD} 1 ${IN_OPT} -j ${blocklist_chain_name}
fi

# flush the chain referencing blacklists, they will be restored in a second
iptables -F ${blocklist_chain_name}

# create the "manual" blacklist set
set_name="manual-blacklist"
if ! ipset list | grep -q "Name: ${set_name}"; then
    ipset create "${set_name}" hash:net
fi
iptables -A ${blocklist_chain_name} -m set --match-set "${set_name}" src,dst -m limit --limit 10/minute -j LOG --log-prefix "BLOCK ${set_name} "
iptables -A ${blocklist_chain_name} -m set --match-set "${set_name}" src,dst -j DROP

# now process the dynamic blacklists
for url in $urls; do
    # initialize temp files
    unsorted_blocklist=$(mktemp)
    sorted_blocklist=$(mktemp)
    new_set_file=$(mktemp)
    headers=$(mktemp)

    # download the blocklist
    set_name=$(echo "$url" | awk -F/ '{print substr($3,0,21);}') # set name is derived from source URL hostname
    curl -v -s ${COMPRESS_OPT} -k "$url" >"${unsorted_blocklist}" 2>"${headers}"

    # this is required for blocklist.de that sends compressed content if asked for it or not
    if [ -z "$COMPRESS_OPT" ]; then
        if grep -qi 'content-encoding: gzip' "${headers}"; then
            mv "${unsorted_blocklist}" "${unsorted_blocklist}.gz"
            gzip -d "${unsorted_blocklist}.gz"
        fi
    fi

    sort -u <"${unsorted_blocklist}" | egrep "^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$" >"${sorted_blocklist}"

    # calculate performance parameters for the new set
    tmp_set_name="tmp_${RANDOM}"
    new_list_size=$(wc -l "${sorted_blocklist}" | awk '{print $1;}' )
    hash_size=$(expr $new_list_size / 2)

    if ! ipset -q list ${set_name} >/dev/null ; then
        ipset create ${set_name} hash:net family inet
    fi

    # start writing new set file
    echo "create ${tmp_set_name} hash:net family inet hashsize ${hash_size} maxelem ${new_list_size}" >>"${new_set_file}"

    # convert list of IPs to ipset statements
    while read line; do
        echo "add ${tmp_set_name} ${line}" >>"${new_set_file}"
    done <"$sorted_blocklist"

    # replace old set with the new, temp one - this guarantees an atomic update
    echo "swap ${tmp_set_name} ${set_name}" >>"${new_set_file}"

    # clear old set (now under temp name)
    echo "destroy ${tmp_set_name}" >>"${new_set_file}"

    # actually execute the set update
    ipset -! -q restore < "${new_set_file}"

    iptables -A ${blocklist_chain_name} -m set --match-set "${set_name}" src,dst -m limit --limit 10/minute -j LOG --log-prefix "BLOCK ${set_name} "
    iptables -A ${blocklist_chain_name} -m set --match-set "${set_name}" src,dst -j DROP

    # clean up temp files
    rm "${unsorted_blocklist}" "${sorted_blocklist}" "${new_set_file}" "${headers}"
done