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#!/bin/bash
# $Id: alcasar-watchdog.sh 2539 2018-04-30 04:37:54Z tom.houdayer $

# alcasar-watchdog.sh
# by Rexy
# This script is distributed under the Gnu General Public License (GPL)
# - Ce script prévient les usagers de l'indisponibilité de l'accès Internet
# - Il déconnecte les usagers dont les équipements réseau ne répondent plus (leur onglet 'status.php' a été fermé)
# - Il deconnecte les usagers dont les adresses MAC sont usurpées
#
# - This script tells users that Internet access is down
# - It logs out users whose PCs are quiet (their status tab is closed)
# - It logs out users whose MAC address is used by other systems (usurped)

CONF_FILE="/usr/local/etc/alcasar.conf"
EXTIF=`grep ^EXTIF= $CONF_FILE|cut -d"=" -f2`                   # EXTernal InterFace
INTIF=`grep ^INTIF= $CONF_FILE|cut -d"=" -f2`                   # INTernal InterFace
private_ip_mask=`grep ^PRIVATE_IP= $CONF_FILE|cut -d"=" -f2`
private_ip_mask=${private_ip_mask:=192.168.182.1/24}
PRIVATE_IP=`echo "$private_ip_mask" |cut -d"/" -f1`             # @ip du portail (côté LAN)
PRIVATE_IP=${PRIVATE_IP:=192.168.182.1}
current_users_file="/var/tmp/havp/current_users.txt"            # file containing active users with their "status.php" tab open
DIR_WEB="/var/www/html"
Index_Page="$DIR_WEB/index.php"
IPTABLES="/sbin/iptables"
TUNIF="tun0"                                                    # listen device for chilli daemon
OLDIFS=$IFS
IFS=$'\n'

function lan_down_alert ()
# users are redirected on ALCASAR IP address if a LAN problem is detected
{
        case $LAN_DOWN in
        "1")
                logger -t alcasar-watchdog "$EXTIF (WAN card) link down"
                echo "$EXTIF (WAN card) link down"
                /bin/sed -i "s?diagnostic =.*?diagnostic = \"$EXTIF (WAN card) link down\";?g" $Index_Page
                ;;
        "2")
                logger -t alcasar-watchdog "can't contact the default router"
                echo "can't contact the default router"
                /bin/sed -i "s?diagnostic =.*?diagnostic = \"can't contact the default router\";?g" $Index_Page
                ;;
        esac
        net_pb=`grep "network_pb = true;" $Index_Page|wc -l`
        if [ $net_pb = "0" ] # user alert (only the first time)
                then
                /bin/sed -i "s?^\$network_pb.*?\$network_pb = true;?g" $Index_Page
                $IPTABLES -I PREROUTING -t nat -i $TUNIF -p udp --dport domain -j REDIRECT --to-port 56
        fi
}

function lan_test ()
# LAN connectiivity testing
{
        watchdog_process=`ps -C alcasar-watchdog.sh|wc -l`
        if [[ $(expr $watchdog_process) -gt 3 ]]
                then
                echo "ALCASAR watchdog is already running"
                exit 0
        fi
        # EXTIF testing
        LAN_DOWN="0"
        if [ `/sbin/ip link | grep $EXTIF|grep "NO-CARRIER" | wc -l` -eq "1" ]
                then
                LAN_DOWN="1"
        fi
        # Default GW testing
        if [ $LAN_DOWN -eq "0" ]
                then
                IP_GW=`/sbin/ip route list|grep ^default|cut -d" " -f3`
                arp_reply=`/usr/sbin/arping -I$EXTIF -c1 $IP_GW|grep response|cut -d" " -f2`
                if [ $arp_reply -eq "0" ]
                        then
                        LAN_DOWN="2"
                fi
        fi
        # if LAN pb detected, users are warned
        if [ $LAN_DOWN != "0" ]
                then
                        lan_down_alert
        # else switch in normal mode
        else
                echo "Internet access is OK for now"
                net_pb=`grep "network_pb = true;" $Index_Page|wc -l`
                if [ $net_pb != "0" ]
                        then
                        /bin/sed -i "s?^\$network_pb.*?\$network_pb = false;?g" $Index_Page
                        $IPTABLES -D PREROUTING -t nat -i $TUNIF -p udp --dport domain -j REDIRECT --to-port 56
                fi
        fi
}

usage="Usage: alcasar-watchdog.sh {-lt --lan_test}"
case $1 in
        -\? | -h* | --h*)
                echo "$usage"
                exit 0
                ;;
        -lt | --lan_test)
                lan_test
                exit 0
                ;;
        *)
                lan_test
                # We disconnect inactive users (its means that their 'status.php' tab has been closed --> their ip address isn't in $current_users_file)
                # process each equipment known by chilli to check if IP address is usurped (with arping)
                for system in `/usr/sbin/chilli_query list | grep -v "0\.0\.0\.0"`
                do
                        active_ip=`echo $system |cut -d" " -f2`
                        active_session=`echo $system |cut -d" " -f5`
                        active_mac=`echo $system | cut -d" " -f1`
                        active_user=`echo $system |cut -d" " -f6`
                        # We disconnect inactive user here :
                        # We check if the user isn't an auth @MAC and if he is still connected
                        if [ "$active_user" != "$active_mac" ] && [ $(expr $active_session) -eq 1 ]; then
                                if [ -e $current_users_file ]; then
                                        # We check if user @IP is in 'current_users.txt'
                                        cmp_user_ok=$(cat $current_users_file | awk -F':' "\$1 == \"$active_ip\" {print \$2}")
                                        # If not we disconnect this user.
                                        if [ -z "$cmp_user_ok" ]; then
                                                logger -t alcasar-watchdog "$active_ip ($active_mac) can't be contact. We disconnects the user ($active_user)."
                                                /usr/sbin/chilli_query logout $active_mac
                                        elif [ "$cmp_user_ok" == "TEMP" ]; then
                                                # Remove the user's IP from 'current_users.txt'. Every user need to insert their @IP everytime to prove their connectivity.
                                                sed -i "/^$active_ip:$cmp_user_ok\$/d" $current_users_file
                                        fi
                                else # "current_user.txt" does not exists. We disconnect every users.
                                        logger -t alcasar-watchdog "The file /var/tmp/havp/current_users.txt doen't' exist. We disconnects the user $active_user"
                                        /usr/sbin/chilli_query logout $active_mac
                                fi
                        fi
                        # IP usurpation test : process only equipment with an authenticated user
                        if [[ $(expr $active_session) -eq 1 ]]
                        then
                                arp_reply=`/usr/sbin/arping -b -I$INTIF -s$PRIVATE_IP -c1 -w4 $active_ip|grep -c "Unicast reply"`
                                # disconnect users whose equipement is usurped. For example, if there are 2 same @MAC it will make 2 lines in output.
                                if [[ $(expr $arp_reply) -gt 1 ]]
                                        then
                                        echo "[$(date +"%Y-%m-%d %H:%M:%S")] : alcasar-watchdog : $active_ip is usurped ($active_mac). Alcasar disconnect the user ($active_user)." >> /var/Save/security/watchdog.log
                                        logger -t alcasar-watchdog "$active_ip is usurped ($active_mac). Alcasar disconnect the user ($active_user)."
                                        /usr/sbin/chilli_query logout $active_mac
                                        chmod 644 /var/Save/security/watchdog.log
                                fi
                        fi
                done
                ;;
esac
IFS=$OLDIFS