#! /bin/bash
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 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 General Public License for more details.
#

dir=$1
offset=$2
operation=$3

if [[ $operation == "" ]]
then
	echo
	echo Usage: $0 dir offset \[plus\|minus\]
	echo 
	echo Example for changing UID/GID 0 \(privileged container\) to 300000 \(unprivileged container\) inside a rootfs located in /mnt:
	echo $0 /mnt 300000 plus
	echo
	echo To change UID/GID range from an unprivileged LXC container to another UID/GID non-zero range, first change it to 0, then go for the final unprivileged range.
	echo 
	echo Example for changing an unprivileged container from UID/GID 100000 to 200000:
	echo $0 /mnt 100000 minus
	echo $0 /mnt 200000 plus
	echo
	exit 0
elif [[ $dir == "/" ]]
then
	echo "You really don't want to do this. Target another work dir."
	exit 1
fi


OIFS="$IFS"
IFS="
"
for file in $(find $dir)
do
	stats=$(stat -c '%u %g %a' $file)
	
	uid=$(echo $stats | cut -d' ' -f1)
	gid=$(echo $stats | cut -d' ' -f2)

	if [[ $uid -lt $offset && $operation == "plus" ]]
	then
		uid=$(expr $uid + $offset)

	elif [[ $uid -ge $offset && $operation == "minus" ]]
	then
		uid=$(expr $uid - $offset)
	else
		continue
	fi

  	if [[ $gid -lt $offset && $operation == "plus" ]]
        then
                gid=$(expr $gid + $offset)

	elif [[ $gid -ge $offset && $operation == "minus" ]]
	then
		gid=$(expr $gid - $offset)
	else
		continue
	fi

	echo chown -h $uid:$gid $file
	chown -h $uid:$gid $file

        perms_octal=$(echo $stats | cut -d' ' -f3)
        setuid=$(echo $perms_octal | grep -E '^4[0-9][0-9][0-9]')
        setgid=$(echo $perms_octal | grep -E '^2[0-9][0-9][0-9]')
        setuidgid=$(echo $perms_octal | grep -E '^6[0-9][0-9][0-9]')

	[[ $setuid ]] && chmod u+s $file
	[[ $setgid ]] && chmod g+s $file
	[[ $setuidgid ]] && chmod ug+s $file
done
IFS="$OIFS"