#!/bin/sh
# developed by acidvegas (https://acid.vegas/random)

set -e

CHROOT_BASE="/var/jail"

display_help() {
	echo "usage: mkchroot [option]"
	echo -e "\nexample: mkchroot --create=acidvegas bash cp irssi ls mkdir mv rm screen wget"
	echo -e "\noptions:"
	echo "  -c, --create=USER   <cmds>  create a new chroot jail"
	echo "  -d, --destroy=USER          destroy a chroot jail"
	echo "  -l, --list                  list chroot jails"
	echo "  -h, --help                  display this help and exit"
}

create_jail() {
	[ $EUID -ne 0 ] && echo "insufficent privledges" && exit 1
	if [ ${#1} -ne 2 ]; then
		CHROOT_USER="${1#*=}"
		CHROOT_CMDS="${@:2}"
	else
		CHROOT_USER=$2
		CHROOT_CMDS="${@:3}"
	fi
	CHROOT_DIR="$CHROOT_BASE/$CHROOT_USER"
	CHROOT_PWD="$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 25 | head -n 1)"
	[ -d $CHROOT_DIR ] && echo "chroot jail already exists for $CHROOT_USER at $CHROOT_DIR" && exit 1
	echo "creating initial directory structure..."
	mkdir -v $CHROOT_DIR
	mkdir -pv $CHROOT_DIR/{dev,etc,home,proc,usr}
	mkdir -v $CHROOT_DIR/dev/pts
	mkdir -v $CHROOT_DIR/home/$CHROOT_USER
	mkdir -v $CHROOT_DIR/usr/share
	echo "making required devices nodes..."
	mknod -m 666 $CHROOT_DIR/dev/null c 1 3
	echo "created device node: $CHROOT_DIR/dev/null"
	mknod -m 666 $CHROOT_DIR/dev/tty c 5 0
	echo "created device node: $CHROOT_DIR/dev/tty"
	mknod -m 666 $CHROOT_DIR/dev/random c 1 8
	echo "created device node: $CHROOT_DIR/dev/random"
	mknod -m 666 $CHROOT_DIR/dev/zero c 1 5
	echo "created device node: $CHROOT_DIR/dev/zero"
	echo "copying required shared libraries..."
	for x in ${CHROOT_CMDS[@]}; do
		for y in $(ldd $(which $x)|grep -v dynamic|cut -d " " -f 3|sed 's/://'|sort|uniq); do
			cp --parents -v $y $CHROOT_DIR
		done
	done
	echo "copying additional required files..."
	if [ ! -d $CHROOT_DIR/bin ] && [ -d $CHROOT_DIR/usr/bin ]; then
		cp -r $CHROOT_DIR/usr/bin $CHROOT_DIR/bin	# This can be improved.
	fi
	if [ ! -d $CHROOT_DIR/lib ] && [ -d $CHROOT_DIR/usr/lib ]; then
		cp -r $CHROOT_DIR/usr/lib $CHROOT_DIR/lib	# This can be improved.
	fi
	cp -v /etc/{hosts,ld.so.cache,ld.so.conf,localtime,nsswitch.conf,resolv.conf} $CHROOT_DIR/etc/
	cp -v /lib/ld-linux.so.* $CHROOT_DIR/lib/
	cp -rv /lib/terminfo/ $CHROOT_DIR/lib/
	cp -rv /usr/share/terminfo/ $CHROOT_DIR/usr/share/
	grep $CHROOT_USER /etc/passwd > $CHROOT_DIR/etc/passwd
	grep $CHROOT_USER /etc/group  > $CHROOT_DIR/etc/group
	grep $CHROOT_USER /etc/shadow > $CHROOT_DIR/etc/shadow
	echo -e "[[ \$- != *i* ]] && return\nalias ls='ls --color=auto'\nPS1='\e[1;30mjail\e[0m | \e[1;34m> \e[0;32m\w \e[0;37m: '" > $CHROOT_DIR/home/$CHROOT_USER/.bash_profile
	if ! id $CHROOT_USER >/dev/null 2>&1; then
		useradd -s /bin/bash -M -p $CHROOT_PWD $CHROOT_USER
		echo "added $CHROOT_USER user"
	fi
	if [ ! $(getent group jail) ]; then
		groupadd jail
		echo "added jail group"
	fi
	if ! getent group jail | grep &>/dev/null "\b${CHROOT_USER}\b"; then
		gpasswd -a $CHROOT_USER jail
		echo "added $CHROOT_USER to jail group"
	fi
	echo "setting permissions..."
	chown -v root:root $CHROOT_DIR
	chown -v root:tty $CHROOT_DIR/dev/tty
	chown -v $CHROOT_USER:$CHROOT_USER $CHROOT_DIR/home/$CHROOT_USER
	chmod -Rv 755 $CHROOT_DIR/home/$CHROOT_USER
	chattr +i $CHROOT_DIR/etc/group
	chattr +i $CHROOT_DIR/etc/hosts
	chattr +i $CHROOT_DIR/etc/nsswitch.conf
	chattr +i $CHROOT_DIR/etc/passwd
	chattr +i $CHROOT_DIR/etc/resolv.conf
	chattr +i $CHROOT_DIR/etc/shadow
	echo "mounting pseudoterminal slave device on $CHROOT_DIR/dev/pts"
	if ! grep -q "devpts $CHROOT_DIR/dev/pts devpts rw,noatime,mode=600,ptmxmode=000 0 0" /etc/fstab; then
		echo -e "\ndevpts $CHROOT_DIR/dev/pts devpts rw,noatime,mode=600,ptmxmode=000 0 0" >> /etc/fstab
		mount -av
	fi
	if ! grep -q "proc $CHROOT_DIR/proc proc rw,noatime,gid=26,hidepid=2 0 0" /etc/fstab; then
		echo -e "\nproc $CHROOT_DIR/proc proc rw,noatime,gid=26,hidepid=2 0 0" >> /etc/fstab
		mount -av
	fi
	if grep -q "AuthorizedKeysFile" /etc/ssh/sshd_config; then
		if ! grep -q "AuthorizedKeysFile /etc/ssh/authorized_keys/%u" /etc/ssh/sshd_config; then
			sed 's/AuthorizedKeysFile.*/AuthorizedKeysFile /etc/ssh/authorized_keys/%u/' /etc/ssh/sshd_config > /etc/ssh/sshd_config
			echo "updated sshd_config with AuthorizedKeysFile"
		fi
	else
		sed -i "1iAuthorizedKeysFile /etc/ssh/authorized_keys/%u" /etc/ssh/sshd_config
	fi
	if ! grep $'Match Group jail\n\tChrootDirectory /var/jail/%u' /etc/ssh/sshd_config; then
		echo -e "\nMatch Group jail\n\tChrootDirectory /var/jail/%u" >> /etc/ssh/sshd_config
		echo "updated sshd_config with ChrootDirectory"
	fi
	echo -e "\nchroot jail for $CHROOT_USER created at $CHROOT_DIR"
	echo "password for $CHROOT_USER is: $CHROOT_PWD"
}

destroy_jail() {
	[ $EUID -ne 0 ] && echo "insufficent privledges" && exit 1
	if [[ ${#1} -ne 2 ]]; then
		CHROOT_USER="${1#*=}"
	else
		CHROOT_USER=$2
	fi
	CHROOT_DIR="$CHROOT_BASE/$CHROOT_USER"
	if mount | grep -q "$CHROOT_DIR/dev/pts"; then
		umount -v $CHROOT_DIR/dev/pts
		echo "unmounted pseudoterminal slave device"
	fi
	if mount | grep -q "$CHROOT_DIR/proc"; then
		umount -v $CHROOT_DIR/proc
		echo "unmounted proc device"
	fi
	if [ -d $CHROOT_DIR ]; then
		chattr -i $CHROOT_DIR/etc/*
		rm -rfv $CHROOT_DIR
	fi
	if id $CHROOT_USER >/dev/null 2>&1; then
		userdel -f $CHROOT_USER
		echo "deleted $CHROOT_USER user"
	fi
	echo "jail destroyed"
}

list_jails() {
	CHROOT_DIRS=$(getent group jail | cut -d: -f4 | sed 's/,/ /g')
	for i in ${CHROOT_DIRS[@]}; do
		echo " * $i"
	done
}

[ "$#" -eq 0 ] && echo -e "invalid or missing arguments\n" && display_help && exit 1
case $1 in
	-c|--create=*)  create_jail  "$@" ;;
	-d|--destroy=*) destroy_jail "$@" ;;
	-l|--list)      list_jails        ;;
	-h|--help)      display_help      ;;
	*) echo -e "invalid or missing arguments\n"; display_help ; exit 1;;
esac