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#!/bin/env bash
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# WAN IP Checker - Whenever server WAN IP address changes, inform admins via email
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# Copyright (C) 2018 Pekka Helenius
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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###########################################################
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# A script for remote server environments which are behind
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# dynamic (non-static) DHCP. Usually these dynamic IPs are
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# used in common household networks in non-corporate
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# environments.
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###########################################################
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# Script requirements
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#
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# SSMTP
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# https://wiki.archlinux.org/index.php/SSMTP
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# Relevant conf files
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# /etc/ssmtp/revaliases
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# /etc/ssmtp/ssmtp.conf
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# Because your email password is stored as cleartext in /etc/ssmtp/ssmtp.conf, it is important that this file
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# is secure. By default, the entire /etc/ssmtp directory is accessible only by root and the mail group.
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# The /usr/bin/ssmtp binary runs as the mail group and can read this file. There is no reason to add
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# yourself or other users to the mail group.
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###########################################################
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# Some lines below are commented out because the timer is handled by systemd service file
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# If you don't use provided systemd service file, re-enable the relevant lines below
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function checkWANIP() {
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# Command to resolve the current IPv4 WAN address
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local WANIP_CURRENT="dig +short myip.opendns.com @resolver1.opendns.com"
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############################
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# If we are connected to internet...
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# There's no point to do WAN IP check if we can't establish connection to WAN/Internet at all
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# In addition, do not generate any network related variables if the connection
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# can't be established. Therefore, include variable defitions inside this if statement.
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if [[ $(printf $(eval ${WANIP_CURRENT} &> /dev/null)$?) -eq 0 ]]; then
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# Check interval in minutes
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# local CHECK_INTERVAL=5
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############################
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# Cache/Log directory of the script
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local WANIP_DIR="$HOME"
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# Log file for checked/resolved IPv4 WAN addresses:
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local WANIP_LOG="$WANIP_DIR/.ip_wan.log"
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if [[ ! -d ${WANIP_DIR} ]]; then
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mkdir -p ${WANIP_DIR}
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fi
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if [[ ! -f ${WANIP_LOG} ]]; then
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printf 'Time\t\t\t\tWAN IPv4\n' > ${WANIP_LOG}
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fi
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############################
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# Log file timestamp format
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local TIMESTAMP=$(date '+%d-%m-%Y, %X')
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############################
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# Email to send notify to
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local EMAIL_RECIPIENT="mymail@hotmail.com"
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# Email subject/title
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local SUBJECT_EMAIL="WAN IP address change (Helsinki, $(tail -1 ${WANIP_LOG} | awk '{print $NF}') -> $(eval ${WANIP_CURRENT}))"
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# Email message/body contents
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local MESSAGE_EMAIL="${TIMESTAMP}: WAN address of the server (Helsinki) has been changed from $(tail -1 ${WANIP_LOG} | awk '{print $NF}') to $(eval ${WANIP_CURRENT})"
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# Message to server stdout
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local MESSAGE_STDOUT="$(echo ${TIMESTAMP}) - WAN address of this server has been changed from $(tail -1 ${WANIP_LOG} | awk '{print $NF}') to $(eval ${WANIP_CURRENT})"
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############################
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# Email send command
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local MAIL_SEND="echo -e \"To: ${EMAIL_RECIPIENT}\nFrom: ${EMAIL_RECIPIENT}\nSubject: ${SUBJECT_EMAIL}\n\n${MESSAGE_EMAIL}\" | sendmail -v ${EMAIL_RECIPIENT}"
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# Log write command
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local LOG_WRITE="printf '%s %s\t\t%s\n' $(echo $TIMESTAMP) $(eval $WANIP_CURRENT) >> $WANIP_LOG"
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############################
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# If the log file has no previous IPv4 entries
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if [[ $(cat $WANIP_LOG | wc -l) -le 1 ]]; then
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eval ${LOG_WRITE}
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fi
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# local i=0
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# while true; do
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# if [[ $i -ne 0 ]]; then
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# sleep $(( ${CHECK_INTERVAL} * 60 ))
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# fi
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# if [[ -f $WANIP_LOG ]]; then
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# The log file must include more than just the header line
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if [[ $(cat $WANIP_LOG | wc -l) -gt 1 ]]; then
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if [[ $(tail -1 $WANIP_LOG | awk '{print $NF}') != $(printf '%s' $(eval $WANIP_CURRENT)) ]]; then
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echo -e ${MESSAGE_STDOUT}
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eval ${MAIL_SEND}
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eval ${LOG_WRITE}
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fi
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fi
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fi
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# let i++
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# done
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}
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############################
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checkWANIP
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