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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) 2019 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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# Log file timestamp format
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local TIMESTAMP=$(date '+%d-%m-%Y, %X')
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############################
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# Email sender
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local EMAIL_SENDER="mailsender@foo.com"
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# Emails to send notification to
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local EMAIL_RECIPIENTS=(
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"whogetsthemail_1@foo.com"
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"whogetsthemail_2@bar.com"
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)
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############################
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# Email send function
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function mailSend {
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echo -e "To: ${1}\nFrom: ${EMAIL_SENDER}\nSubject: ${SUBJECT_EMAIL}\n\n${MESSAGE_EMAIL}" | sendmail -v "${1}"
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}
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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)$?) -eq 0 ]]; then
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############################
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# Cache/Log directory of the script
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local WANIP_DIR="/var/spool/mail"
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# Log file for checked/resolved IPv4 WAN addresses
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local WANIP_LOG="$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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# Email subject/title
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local SUBJECT_EMAIL="WAN IP address changed (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 location (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 ${WANIP_CURRENT})"
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############################
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# Log write command
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local LOG_WRITE=$(printf '%s %s\t\t%s\n' $(echo "${TIMESTAMP}") $(eval "${WANIP_CURRENT}") >> "${WANIP_LOG}")
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############################
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if [[ $(tail -1 "${WANIP_LOG}" | awk '{print $NF}') != $(printf '%s' $(eval "${WANIP_CURRENT}")) ]] || \
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[[ $(cat "${WANIP_LOG}" | wc -l) -le 2 ]] ; then
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echo -e "${MESSAGE_STDOUT}"
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for i in "${EMAIL_RECIPIENTS[@]}"; do
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mailSend "${i}"
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$LOG_WRITE
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done
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fi
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fi
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}
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############################
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checkWANIP
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