freedombone/src/freedombone-utils-cron

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#!/bin/bash
#
# .---. . .
# | | |
# |--- .--. .-. .-. .-.| .-. .--.--. |.-. .-. .--. .-.
# | | (.-' (.-' ( | ( )| | | | )( )| | (.-'
# ' ' --' --' -' - -' ' ' -' -' -' ' - --'
#
# Freedom in the Cloud
#
# Cron functions
#
# License
# =======
#
# Copyright (C) 2014-2016 Bob Mottram <bob@robotics.uk.to>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
function cron_add_mins {
if ! grep -q "${2}" /etc/crontab; then
echo "*/${1} * * * * root ${2}" >> /etc/crontab
systemctl restart cron
fi
}
function randomize_cron {
# The predictable default timing of Debian cron jobs might
# be exploitable knowledge. Avoid too much predictability
# by randomizing the times when cron jobs run
if grep -Fxq "randomize_cron" $COMPLETION_FILE; then
return
fi
# randomize the day on which the weekly cron job runs
randdow=$(($RANDOM%6+1))
sed -i "s|\* \* 7|* * $randdow|g" /etc/crontab
# randomize the time when the weekly cron job runs
randmin=$(($RANDOM%60))
randhr=$(($RANDOM%3+1))
sed -i "s|47 6|$randmin $randhr|g" /etc/crontab
# randomize the time when the daily cron job runs
randmin=$(($RANDOM%60))
randhr=$(($RANDOM%3+4))
sed -i "s|25 6\t\* \* \*|$randmin $randhr\t* * *|g" /etc/crontab
# randomize the time when the hourly cron job runs
randmin=$(($RANDOM%60))
sed -i "s|17 \*\t|$randmin *\t|g" /etc/crontab
# randomize monthly cron job time and day
randmin=$(($RANDOM%60))
randhr=$(($RANDOM%22+1))
randdom=$(($RANDOM%27+1))
sed -i "s|52 6\t|$randmin $randhr\t|g" /etc/crontab
sed -i "s|\t1 \* \*|\t$randdom * *|g" /etc/crontab
systemctl restart cron
echo 'randomize_cron' >> $COMPLETION_FILE
}
# NOTE: deliberately there is no "exit 0"