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#!/usr/bin/env bash
set -euE
# librechroot

# Copyright (C) 2010-2012 Nicolás Reynolds <fauno@parabola.nu>
# Copyright (C) 2011-2012 Joshua Ismael Haase Hernández (xihh) <hahj87@gmail.com>
# Copyright (C) 2012 Michał Masłowski <mtjm@mtjm.eu>
# Copyright (C) 2012-2018 Luke Shumaker <lukeshu@parabola.nu>
# Copyright (C) 2018 Andreas Grapentin <andreas@grapentin.org>
#
# License: GNU GPLv2+
#
# This file is part of Parabola.
#
# Parabola 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.
#
# Parabola 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.
#
# You should have received a copy of the GNU General Public License
# along with Parabola. If not, see <http://www.gnu.org/licenses/>.

# HACKING: if a command is added or removed, it must be changed in 4 places:
#   - the usage() text
#   - the commands=() array
#   - the case statement in main() that checks the number of arguments
#   - the case statement in main() that runs them

. "$(librelib conf)"
. "$(librelib messages)"
. "$(librelib chroot/makechrootpkg)"

shopt -s nullglob
umask 0022

################################################################################
# Wrappers for files in ${pkglibexecdir}/chroot/                               #
################################################################################

readonly _arch_nspawn="$(librelib chroot/arch-nspawn)"
readonly _mkarchroot="$(librelib chroot/mkarchroot)"

arch_nspawn_flags=()
sysd_nspawn_flags=()

hack_arch_nspawn_flags() {
	local copydir="$1"

	local makepkg_conf="$copydir/etc/makepkg.conf"

	OPTIND=1
	set -- ${arch_nspawn_flags+"${arch_nspawn_flags[@]}"}
	while getopts 'hC:M:c:f:s' arg; do
		case "$arg" in
			M) makepkg_conf="$OPTARG" ;;
			*) :;;
		esac
	done

	# Detect the architecture of the chroot
	local CARCH
	if [[ -f "$makepkg_conf" ]]; then
		eval "$(grep -a '^CARCH=' "$makepkg_conf")"
	else
		CARCH="$(uname -m)"
	fi

	local setarch interpreter
	case $CARCH in
		armv7h) setarch=armv7l; interpreter=/usr/bin/qemu-arm-static    ;;
		*)      setarch=$CARCH; interpreter=/usr/bin/qemu-$CARCH-static ;;
	esac
	if ! setarch $setarch /bin/true 2>/dev/null; then
		# We're running a cross-arch chroot

		# Make sure that qemu-static is set up with binfmt_misc
		if [[ -z $(grep -l -xF \
			     -e "interpreter $interpreter" \
			     -r -- /proc/sys/fs/binfmt_misc 2>/dev/null \
			   | xargs -r grep -xF 'enabled') ]]
		then
			error 'Cannot cross-compile for %s on %s' "$CARCH" "$(uname -m)"
			plain 'This requires a binfmt_misc entry for %s.' "$interpreter"
			prose 'Such a binfmt_misc entry is provided by the %s
			       package.  If you have it installed, but still see
			       this message, you may need to restart %s.' \
				qemu-user-static-binfmt systemd-binfmt.service
			return $EXIT_NOTINSTALLED
		fi

		# Let qemu/binfmt_misc do its thing
		arch_nspawn_flags+=(-f "$interpreter" -s)
	fi
}

# Usage: arch-nspawn $copydir $cmd...
arch-nspawn() {
	local copydir=$1; shift
	local cmd=("$@")

	local arch_nspawn_flags=(${arch_nspawn_flags+"${arch_nspawn_flags[@]}"})
	hack_arch_nspawn_flags "$copydir"

	"$_arch_nspawn" \
	    ${arch_nspawn_flags+"${arch_nspawn_flags[@]}"} \
	    "$copydir" \
	    ${sysd_nspawn_flags+"${sysd_nspawn_flags[@]}"} \
	    -- \
	    "${cmd[@]}"
}

# Usage: mkarchroot $copydir $pkgs...
mkarchroot() {
	local copydir=$1; shift
	local pkgs=("$@")

	local arch_nspawn_flags=(${arch_nspawn_flags+"${arch_nspawn_flags[@]}"})
	hack_arch_nspawn_flags "$copydir"

	unshare -m "$_mkarchroot" \
	    ${arch_nspawn_flags+"${arch_nspawn_flags[@]}"} \
	    "$copydir" \
	    "${pkgs[@]}"
}

################################################################################
# Utility functions                                                            #
################################################################################

# Usage: make_empty_repo $copydir
make_empty_repo() {
	local copydir=$1
	mkdir -p "${copydir}/repo"
	bsdtar -czf "${copydir}/repo/repo.db.tar.gz" -T /dev/null
	ln -s "repo.db.tar.gz" "${copydir}/repo/repo.db"
}

# Usage: chroot_add_to_local_repo $copydir $pkgfiles...
chroot_add_to_local_repo() {
	local copydir=$1; shift
	mkdir -p "$copydir/repo"
	local pkgfile
	for pkgfile in "$@"; do
		cp "$pkgfile" "$copydir/repo"
		pushd "$copydir/repo" >/dev/null
		repo-add repo.db.tar.gz "${pkgfile##*/}"
		popd >/dev/null
	done
}

# Print code to set $rootdir and $copydir; blank them on error
calculate_directories() {
	# Don't assume that CHROOTDIR or CHROOT are set,
	# but assume that COPY is set.
	local rootdir copydir

	if [[ -n ${CHROOTDIR:-} ]] && [[ -n ${CHROOT:-} ]]; then
		rootdir="${CHROOTDIR}/${CHROOT}/root"
	else
		rootdir=''
	fi

	if [[ ${COPY:0:1} = / ]]; then
		copydir=$COPY
	elif [[ -n ${CHROOTDIR:-} ]] && [[ -n ${CHROOT:-} ]]; then
		copydir="${CHROOTDIR}/${CHROOT}/${COPY}"
	else
		copydir=''
	fi

	declare -p rootdir
	declare -p copydir
}

check_mountpoint() {
	local file=$1
	local mountpoint mountopts
	mountpoint="$(df -P "$file"|sed '1d;s/.*\s//')"
	mountopts=($(LC_ALL=C mount|awk "{ if (\$3==\"$mountpoint\") { gsub(/[(,)]/, \" \", \$6); print \$6 } }"))
	! in_array nosuid "${mountopts[@]}" && ! in_array noexec "${mountopts[@]}"
}

################################################################################
# Main program                                                                 #
################################################################################

usage() {
	eval "$(calculate_directories)"
	print "Usage: %s [OPTIONS] COMMAND [ARGS...]" "${0##*/}"
	print 'Interacts with an archroot (arch chroot).'
	echo
	prose 'This is configured with `chroot.conf`, either in
	       `/etc/libretools.d/`, or `$XDG_CONFIG_HOME/libretools/`.
	       The variables you may set are $CHROOTDIR, $CHROOT, and
	       $CHROOTEXTRAPKG.'
	echo
	prose 'There may be multiple chroots; they are stored in $CHROOTDIR.'
	echo
	prose 'Each chroot is named; the default is configured with $CHROOT.'
	echo
	prose 'Each named chroot has a master clean copy (named `root`), and any
	       number of other named copies; the copy used by default is the
	       current username (or $SUDO_USER, or `copy` if root).'
	echo
	prose 'The full path to the chroot copy is "$CHROOTDIR/$CHROOT/$COPY",
	       unless the copy name is manually specified as an absolute path,
	       in which case, that path is used.'
	echo
	prose 'The current settings for the above variables are:'
	printf '    CHROOTDIR : %s\n' "${CHROOTDIR:-$(_ 'ERROR: NO SETTING')}"
	printf '    CHROOT    : %s\n' "${CHROOT:-$(_ 'ERROR: NO SETTING')}"
	printf '    COPY      : %s\n' "$COPY"
	printf '    rootdir   : %s\n' "${rootdir:-$(_ 'ERROR')}"
	printf '    copydir   : %s\n' "${copydir:-$(_ 'ERROR')}"
	echo
	prose 'If the chroot or copy does not exist, it will be created
	       automatically.  A chroot by default contains the packages in the
	       group "base-devel" and any packages named in $CHROOTEXTRAPKG.
	       Unless the `-C` or `-M` flags are used, the configuration files
	       that this program installs are the stock versions supplied in the
	       packages, not the versions from your host system.  Other tools
	       (such as libremakepkg) may alter the configuration.'
	echo
	prose 'This command will make the following configuration changes in the
	       chroot:'
	bullet   'overwrite `/etc/libretools.d/chroot.conf`' # libretools/librechroot
	bullet   'overwrite `/etc/pacman.d/mirrorlist`' # devtools/arch-nspawn
	bullet   'set `CacheDir` in `/etc/pacman.conf`' # devtools/arch-nspawn
	prose 'If a new `pacman.conf` is inserted with the `-C` flag, the change
	       is made after the file is copied in; the `-C` flag doesn'"'"'t
	       stop the change from being effective.'
	echo
	prose 'The processor architecture of the chroot is determined
	       by the by `CARCH` variable in the `/etc/makepkg.conf`
	       file inside of the chroot.'
	echo
	prose 'The `-A CARCH` flag is *almost* simply an alias for'
	printf '    %s\n' \
	       '-C "/usr/share/pacman/defaults/pacman.conf.$CARCH" \' \
	       '-M "/usr/share/pacman/defaults/makepkg.conf.$CARCH"'
	prose 'However, before doing that, it actually makes a temporary copy of
	       `pacman.conf`, and sets the `Architecture` line to match the
	       `CARCH` line in `makepkg.conf`.'
	echo
	prose 'Creating a copy, deleting a copy, or syncing a copy can be fairly
	       slow; but are very fast if $CHROOTDIR is on a btrfs partition.'
	echo
	print 'Options:'
	flag "-n <$(_ CHROOT)>" 'Name of the chroot to use'
	flag "-l <$(_ COPY)>"   'Name of, or absolute path to, the copy to use'
	flag '-N'               'Disable networking in the chroot'
	flag "-C <$(_ FILE)>"   'Copy this file to `$copydir/etc/pacman.conf`'
	flag "-M <$(_ FILE)>"   'Copy this file to `$copydir/etc/makepkg.conf`'
	flag "-A <$(_ CARCH)>"  'Set the architecture of the copy; simply an
	                         alias for the `-C` and `-M` flags, see above.'
	flag "-w <$(_ 'PATH[:INSIDE_PATH[:OPTIONS]]')>" 'Bind mount a file or directory, read/write'
	flag "-r <$(_ 'PATH[:INSIDE_PATH[:OPTIONS]]')>" 'Bind mount a file or directory, read-only'
	echo
	print 'Commands:'
	print ' Create/copy/delete:'
	flag 'noop|make'       'Do not do anything, but still creates the chroot
	                        copy if it does not exist'
	flag 'sync'            'Sync the copy with the clean (`root`) copy'
	flag 'delete'          'Delete the chroot copy'
	print ' Dealing with packages:'
	flag "install-file $(_ FILES...)"       'Like `pacman -U FILES...`'
	flag "install-name $(_ NAMES...)"       'Like `pacman -S NAMES...`'
	flag 'update'                           'Like `pacman -Syu`'
	flag 'clean-pkgs'      'Remove all packages from the chroot copy that
	                        are not in base-devel, $CHROOTEXTRAPKG, or named
	                        as a dependency in the file `/startdir/PKGBUILD`
	                        in the chroot copy; and install all packages
	                        that are.'
	print ' Other:'
	flag "run $(_ CMD...)" 'Run CMD in the chroot copy'
	flag 'enter'           'Enter an interactive shell in the chroot copy'
	flag 'clean-repo'      'Clean /repo in the chroot copy'
	flag 'help'            'Show this message'
}
readonly commands=(
	noop make sync delete
	install-file install-name update clean-pkgs
	run enter clean-repo help
)

# Globals: $CHROOTDIR, $CHROOT, $COPY, $rootdir and $copydir
main() {
	COPY=$LIBREUSER
	[[ $COPY != root ]] || COPY=copy

	declare -i retconf=0
	load_conf chroot.conf CHROOTDIR CHROOT || retconf=$?

	local mode=enter opt
	declare -Ai used_opts
	while getopts 'n:l:NC:M:A:w:r:' opt; do
		case $opt in
			n) CHROOT=$OPTARG;;
			l) COPY=$OPTARG;;
			N) sysd_nspawn_flags+=(--private-network);;
			C|M) arch_nspawn_flags+=(-$opt "$OPTARG");;
			A)
				if ! [[ -f "/usr/share/pacman/defaults/pacman.conf.$OPTARG" && -f "/usr/share/pacman/defaults/makepkg.conf.$OPTARG" ]]; then
					error 'Unsupported architecture: %s' "$OPTARG"
					plain 'See the files in %q for valid architectures.' /usr/share/pacman/defaults/
					return $EXIT_INVALIDARGUMENT;
				fi
				trap 'rm -f -- "$tmppacmanconf"' EXIT
				tmppacmanconf="$(mktemp --tmpdir librechroot-pacman.conf.XXXXXXXXXX)"
				< "/usr/share/pacman/defaults/pacman.conf.$OPTARG" sed -r "s|^#?\\s*Architecture.+|Architecture = ${OPTARG}|g" > "$tmppacmanconf"
				arch_nspawn_flags+=(
					-C "$tmppacmanconf"
					-M "/usr/share/pacman/defaults/makepkg.conf.$OPTARG"
				);;
			w) sysd_nspawn_flags+=("--bind=$OPTARG");;
			r) sysd_nspawn_flags+=("--bind-ro=$OPTARG");;
			*) usage >&2; return $EXIT_INVALIDARGUMENT;;
		esac
		used_opts[$opt]+=1
	done
	for opt in n l C M A; do
		if (( ${used_opts[$opt]:-0} > 1 )); then
			error "Option -%s may only be given once" "$opt"
			usage >&2
			return $EXIT_INVALIDARGUMENT
		fi
	done
	if (( ${used_opts[A]:-0} && ( ${used_opts[C]:-0} || ${used_opts[M]:-0} ) )); then
		error "Option -A may not be used together with -C or -M"
		usage >&2
		return $EXIT_INVALIDARGUMENT
	fi
	shift $((OPTIND - 1))
	if [[ $# -lt 1 ]]; then
		error "Must specify a command"
		usage >&2
		return $EXIT_INVALIDARGUMENT
	fi
	mode=$1
	if ! in_array "$mode" "${commands[@]}"; then
		error "Unrecognized command: %s" "$mode"
		usage >&2
		return $EXIT_INVALIDARGUMENT
	fi
	shift
	case "$mode" in
		noop|make|sync|delete|update|enter|clean-pkgs|clean-repo)
			if [[ $# -gt 0 ]]; then
				error 'Command `%s` does not take any arguments: %s' "$mode" "$*"
				usage >&2
				return $EXIT_INVALIDARGUMENT
			fi
			:;;
		install-file)
			if [[ $# -lt 1 ]]; then
				error 'Command `%s` requires at least one file' "$mode"
				usage >&2
				return $EXIT_INVALIDARGUMENT
			else
				local missing=()
				local file
				for file in "$@"; do
					if ! [[ -f $file ]]; then
						missing+=("$file")
					fi
				done
				if [[ ${#missing[@]} -gt 0 ]]; then
					error "%s: file(s) not found: %s" "$mode" "${missing[*]}"
					return $EXIT_INVALIDARGUMENT
				fi
			fi
			:;;
		install-name)
			if [[ $# -lt 1 ]]; then
				error 'Command `%s` requires at least one package name' "$mode"
				usage >&2
				return $EXIT_INVALIDARGUMENT
			fi
			:;;
		run)
			if [[ $# -lt 1 ]]; then
				error 'Command `%s` requires at least one argument' "$mode"
				usage >&2
				return $EXIT_INVALIDARGUMENT
			fi
			:;;
	esac

	if [[ $mode == help ]]; then
		usage
		return $EXIT_SUCCESS
	fi

	[[ $retconf = 0 ]] || exit $retconf
	eval "$(calculate_directories)"

	readonly LIBREUSER LIBREHOME
	readonly CHROOTDIR CHROOT COPY
	readonly rootdir copydir
	readonly mode

	########################################################################

	if (( EUID )); then
		error "This program must be run as root."
		return $EXIT_NOPERMISSION
	fi

	umask 0022

	# Keep this lock for as long as we are running
	# Note that '9' is the same FD number as in mkarchroot et al.
	lock 9 "$copydir.lock" \
		"Waiting for existing lock on chroot copy to be released: [%s]" "$COPY"

	if [[ $mode != delete ]]; then
		if ! check_mountpoint "$copydir.lock"; then
			error "Chroot copy is mounted with nosuid or noexec options: [%s]" "$COPY"
			return $EXIT_FAILURE
		fi

		if [[ ! -d $rootdir ]]; then
			msg "Creating 'root' copy for chroot [%s]" "$CHROOT"
			mkarchroot "$rootdir" base-devel
			make_empty_repo "$rootdir"
		fi

		if [[ ! -d $copydir ]] || [[ $mode == sync ]]; then
			msg "Syncing copy [%s] with root copy" "$COPY"
			sync_chroot "$CHROOTDIR/$CHROOT/root" "$copydir" "$COPY"
		fi

		# Note: the in-chroot pkgconfdir is non-configurable, this is
		# intentionally hard-coded.
		mkdir -p "$copydir/etc/libretools.d"
		{
			if [[ ${#CHROOTEXTRAPKG[*]} -eq 0 ]]; then
				echo 'CHROOTEXTRAPKG=()'
			else
				printf 'CHROOTEXTRAPKG=('
				printf '%q ' "${CHROOTEXTRAPKG[@]}"
				printf ')\n'
			fi
		} > "$copydir"/etc/libretools.d/chroot.conf

		# "touch" the chroot first
		# this will
		#  - overwrite '/etc/pacman.d/mirrorlist'"
		#  - set 'CacheDir' in \`/etc/pacman.conf'"
		#  - apply -C or -M flags
		arch-nspawn "$copydir" true
		if [[ -n ${tmppacmanconf:-} ]]; then
			rm -f -- "$tmppacmanconf"
		fi
		trap EXIT # clear the trap to remove the tmp pacman.conf from -A
		arch_nspawn_flags=() # XXX dirty hack, don't apply -C or -M again
	fi

	########################################################################

	case "$mode" in
		# Creat/copy/delete
		noop|make|sync) :;;
		delete)
			if [[ -d $copydir ]]; then
				delete_chroot "$copydir"
			fi
			;;

		# Dealing with packages
		install-file)
			install_packages         "$copydir" "$@"
			chroot_add_to_local_repo "$copydir" "$@"
			;;
		install-name)
			arch-nspawn "$copydir" pacman -Sy -- "$@"
			;;
		update)
			arch-nspawn "$copydir" pacman -Syu --noconfirm
			;;
		clean-pkgs)
			trap "rm -f -- ${copydir@Q}/{bin/chcleanup,chrootexec}" EXIT
			install -m755 "$(librelib chroot/chcleanup)" "$copydir/bin/chcleanup"
			printf '%s\n' \
				'#!/bin/bash' \
				'mkdir -p /startdir' \
				'cd /startdir' \
				'/bin/chcleanup' \
				> "$copydir/chrootexec"
			chmod 755 "$copydir/chrootexec"
			arch-nspawn "$copydir" /chrootexec
			;;

		# Other
		run)
			arch-nspawn "$copydir" "$@"
			;;
		enter)
			arch-nspawn "$copydir" bash
			;;
		clean-repo)
			rm -rf "${copydir}"/repo/*
			make_empty_repo "$copydir"
			;;
	esac
}

main "$@"