chrooter

#!/bin/sh
# Abstract: CHange ROOT into desired directory (chrooter).
# Created by github.com/kreyren under GNUv3 (https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html)

### START OF KREYPI INIT ###
# https://github.com/RXT067/Scripts/tree/kreyren/kreypi

# Do not make additional functions here since we are going to source a library

# Check for root
if [ "$(id -u)" != 0 ]; then
	printf 'FATAL: %s\n' "This script is using KREYPI library which needs to be exported in /lib/shell using root permission"
	exit 3
elif [ "$(id -u)" = 0 ]; then
	# shellcheck disable=SC2154
	[ -n "$debug" ] && printf 'DEBUG: %s\n' "Script executed from an user with ID $(id -u)"
else
	printf 'FATAL: %s\n' "Unexpected happend in KREYPI_INIT for checking root"
	exit 255
fi

# Create a new directory for shell libraries if not present already
if [ ! -e /lib/shell ]; then
	mkdir /lib/shell || { printf 'FATAL: %s\n' "Unable to make a new directory in '/lib/shell', is this non-standard file hierarchy?" ; exit 1 ;}
elif [ -f /lib/shell ]; then
	printf 'FATAL: %s\n' "File '/lib/shell' is a file which is unexpected, expecting directory to export kreypi library"
	exit 1
elif [ -d /lib/shell ]; then
	# shellcheck disable=SC2154
	[ -n "$debug" ] && printf 'DEBUG: %s\n' "Directory '/lib/shell' already exists, no need to make it"
else
	printf 'FATAL: %s\n' "Unexpected result in KREYPI_INIT checking for /lib/shell"
	exit 255
fi

# Fetch the library
if [ -e /lib/shell/kreypi.sh ]; then
	# shellcheck disable=SC2154
	[ -n "$debug" ] && printf 'DEBUG: %s\n' "Directory in '/lib/shell' already exists, skipping fetch"
elif command -v wget >/dev/null; then
	wget https://raw.githubusercontent.com/RXT067/Scripts/kreyren/kreypi/kreypi.sh -O /lib/shell/kreypi.sh || { printf 'FATAL: %s\n' "Unable to fetch kreypi.sh from https://raw.githubusercontent.com/RXT067/Scripts/kreyren/kreypi/kreypi.sh in /lib/shell/kreypi.sh using wget" ; exit 1;}
elif command -v curl >/dev/null; then
	curl https://raw.githubusercontent.com/RXT067/Scripts/kreyren/kreypi/kreypi.sh -o /lib/shell/kreypi.sh || { printf 'FATAL: %s\n' "Unable to fetch kreypi.sh from https://raw.githubusercontent.com/RXT067/Scripts/kreyren/kreypi/kreypi.sh in /lib/shell/kreypi.sh using curl" ; exit 1 ;}
else
	printf 'FATAL: %s\n' "Unable to download kreypi library from 'https://raw.githubusercontent.com/RXT067/Scripts/kreyren/kreypi/kreypi.sh' in '/lib/shell/kreypi.sh'"
	exit 255
fi

# Sanitycheck for /lib/shell
if [ -e /lib/shell ]; then
	# shellcheck disable=SC2154
	[ -n "$debug" ] && printf 'DEBUG: %s\n' "Directory in '/lib/shell' already exists, passing sanity check"
elif [ ! -e /lib/shell ]; then
	printf 'FATAL: %s\n' "Sanitycheck for /lib/shell failed"
	exit 1
else
	printf 'FATAL: %s\n' "Unexpected happend in sanitycheck for /lib/shell"
	exit 255
fi

# Source KREYPI
if [ -e "/lib/shell/kreypi.sh" ]; then
	# 'source' can not be used on POSIX sh
	# shellcheck source="/lib/shell/kreypi.sh"
	. "/lib/shell/kreypi.sh" || { printf 'FATAL: %s\n' "Unable to source '/lib/shell/kreypi.sh'" ; exit 1 ;}
	# shellcheck disable=SC2154
	[ -n "$debug" ] && printf 'DEBUG: %s\n' "Kreypi in '/lib/shell/kreypi.sh' has been successfully sourced"
elif [ ! -e "/lib/shell/kreypi.sh" ]; then
	printf 'FATAL: %s\n' "Unable to source '/lib/shell/kreypi.sh' since path does not exists"
	exit 1
else
	printf 'FATAL: %s\n' "Unexpected happend in sourcing KREYPI_INIT"
	exit 255
fi

### END OF KREYPI INIT ###

# Sanitization for Mount Directory variable
sanitize_mount_directory() {
	destdir_smd="$1"

		# Sanity check for destdir_smd
	if [ -z "$destdir_smd" ]; then
		die 2 "Function 'sanitize_mount_directory' expects argument with path to mount directory which is not provided"

	elif [ -n "$destdir_smd" ]; then
		debug "Variable destdir_smd in function 'sanitize_mount_directory' is set on '$destdir_smd'"

		# Check if destdir_smd is valid directory
		if [ ! -d "$destdir_smd" ]; then
			die 1 "First argument '$destdir_smd' in function 'sanitize_mount_directory' is not a valid directory"
		elif [ -d "$destdir_smd" ]; then
			debug "In function 'sanitize_mount_directory' variable destdir_smd stores a value of valid directory"
		else
			die 255 "sanitize_mount_directory, destdir_smd directory check"
		fi

		# Enforce FSH-3.0
		case "$destdir_smd" in
			/mnt/*) debug "Function 'sanitize_mount_directory' - destdir_smd '$destdir_smd' is valid" ;;
			*) warn "Mount directories should be mounted in /mnt directory not $destdir_smd"
		esac

		if [ ! -e "$destdir_smd/etc" ] && [ -z "$forced" ]; then
			die 1 "Unable to find /etc directory in $destdir_smd directory, assuming invalid mount directory, use --force to override if needed."
		elif [ ! -e "$destdir_smd/etc" ] && [ -n "$forced" ]; then
			warn "Directory '$destdir_smd/etc' is not found, but forced is used"
		elif [ -e "$destdir_smd/etc" ]; then
			debug "Directory '$destdir_smd' is valid directory for chroot assuming checking for '$destdir_smd/etc'"
		else
			die 255 "sanitize_mount_directory, destdir_smd/etc check"
		fi

	else
		die 255 "sanitize_mount_directory, destdir_smd"

	fi

	unset destdir_smd
}

# Mount required filesystems for chrooting
## Reference: https://wiki.gentoo.org/wiki/Chroot#Configuration
mount_required_fs() {
	destdir_mrf="$1"

	# Sanitization - Expecting $destdir_mrf="/mnt/something"
	sanitize_mount_directory "$destdir_mrf"

	# Mount /dev
	if ! grep -qF "$destdir_mrf/dev" /proc/mounts; then
		mount --rbind /dev "$destdir_mrf/dev/" || die 1 "Unable to mount '/dev' as rbind on '$destdir_mrf/dev'"
		mount --make-rslave "$destdir_mrf/dev" || die 1 "Unable to mount '/dev' as '-make-rslave' on '$destdir_mrf/dev'"
	elif grep -qF "$destdir_mrf/dev" /proc/mounts; then
		# FIXME: This may output if --rbind above fails
		debug "Directory '$destdir_mrf/dev' is already mounted"
	else
		die 255 "mount_reguired_fs, dev"
	fi

	# Mount /sys
	if ! grep -qF "$destdir_mrf/sys" /proc/mounts; then
		mount --bind /sys "$destdir_mrf/sys/" || die 1 "Unable to mount '/sys' to '$destdir_mrf/sys' as bind which is required"
	elif grep -qF "$destdir_mrf/sys" /proc/mounts; then
		debug "Directory '$destdir_mrf/sys' is already mounted"
	else
		die 255 "mount_required_fs, sys"
	fi

	# Mount /tmp
	if ! grep -qF "$destdir_mrf/tmp" /proc/mounts; then
		mount --rbind /tmp "$destdir_mrf/tmp" || die 1 "Unable to mount '$destdir_mrf/tmp' as '--bind' on '/tmp'"
		mount --make-rslave "$destdir_mrf/tmp" || die 1 "Unable to mount '/tmp' to '$destdir_mrf/tmp' as '--make-rbind' which is required"
	elif grep -qF "$destdir_mrf/tmp" /proc/mounts; then
		# FIXME: This may trigger if --rbind above failed
		debug "Directory '$destdir_mrf/tmp' is already mounted"
	else
		die 255 "mount_required_fs, tmp"
	fi

	# Mount /proc
	#if ! grep -qF "$destdir_mrf/proc" /proc/mounts;	then { mount --types proc none "$destdir_mrf/proc/" || die 0 "Unable to mount '/proc' on 'none' which is required";}; fi
	# HOTFIX, fuck everything
	# FIXME!
	mount --types proc none "$destdir_mrf/proc/" 2>/dev/null

	unset destdir_mrf
}

# Perform chroot
chrooter() {
	destdir_crt="$1"
	command="$2"

	# Sanitization - Expecting $destdir_crt="/mnt/something"
	sanitize_mount_directory "$destdir_crt"

	# Mount everything in chroot
	# FIXME: Sanitize
	{ chroot "$destdir_crt" mount -a && info "filesystems has been mounted on $destdir_crt" ;} || warn "Unable to mount all filesystems on $destdir_crt"

	# Perform chroot
	if [ -n "$command" ]; then
		chroot "$destdir_crt" "$command" || die 1 "Unable to Change Root from '$destdir_crt' with command '$command'"
	elif [ -z "$command" ]; then
		chroot "$destdir_crt" /bin/bash || die 1 "Unable to Change Root from '$destdir_crt' to /bin/bash"
	fi

	unset destdir_crt command
}

# Take down chroot
kill_chrooter() {
	destdir_kc="$1"

	# Sanitization - Expecting $destdir_kc="/mnt/something"
	sanitize_mount_directory "$destdir_kc"

	if grep -qF $destdir_kc /proc/mounts; then
		fixme "Unable to kill chroot on runtime (/dev preventing umount)"
		umount -R "$destdir_kc" || die 1 "Unable to unmount $destdir_kc"
	elif ! grep -qF "$destdir_kc" /proc/mounts; then
		info "Directory $destdir_kc is already not mounted, skipping.."
		return 0
	else
		die 255 "kill_chrooter, checking for destdir_kc"
	fi
}

# CODE
checkroot "$@"

while [ "$#" -ge 1 ]; do case "$1" in
	-f|--force) export forced="KREYREN"; shift 1 ;;
	-K|--kill) kill_chrooter "$2" ; exit 0 ;;
	/*) # Allow full path only
		mount_required_fs "$1"

		chrooter "$1" "$2"

		if [ -n "$2" ]; then
			shift 2
		elif [ -n "$1" ] && [ -z "$2" ]; then
			shift 1
		else
			die 255 "Arguments, shifting of full unix path"
		fi
	;;
	*) die 2 "Unrecognized argument '$1' was parsed"
esac; done