pacwrap/dist/tools/runtime.sh

#!/bin/bash
#
#  pacwrap - runtime.sh
#
#  This script packages the most minimal userspace environment possible 
#  allowing pacwrap's agent binary to execute in an otherwise empty container.
# 
#  Copyright (C) 2023-2024 Xavier Moffett 
#  sapphirus(at)azorium(dot)net
#
#  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, with only version 3 of the License.
#
#  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.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <https://www.gnu.org/licenses/>.

if [[ ! -d "$PWD/dist/tools/" ]]; then echo "This script may only be executed via the workspace root directory."; exit 2; fi
if [[ ! -f ./dist/tools/common.sh ]]; then echo "Common script is missing. Ensure the source tree is intact."; exit 2; fi

source ./dist/tools/common.sh
ACTION_NOUN="Runtime generation"

# 
# Environment variables
#
LIB_DIR="/lib"
BIN_DIR="/bin"
ETC_DIR="/etc"
DEST_DIR="$PWD/dist/runtime"
FAKEROOT="/libfakeroot"
FAKEROOT_DIR="/usr/lib/libfakeroot"
FAKEROOT_SRC="$FAKEROOT_DIR/libfakeroot.so"
FAKEROOT_DEST="$DEST_DIR$LIB_DIR$FAKEROOT"
FAKECHROOT="/fakechroot"
FAKECHROOT_SRC="$FAKEROOT_DIR$FAKECHROOT/libfakechroot.so"
FAKECHROOT_DEST="$DEST_DIR$LIB_DIR$FAKEROOT$FAKECHROOT"
PROFILE_PS1="PS1='$(echo '$USER \\W>\\$') '";

# !! File an issue/PR if there's an incompatibility !!
#
# Array of bin utilities to include within the runtime environment
#
BIN_UTILS="bash busybox faked fakeroot find gpg grep getopt sed"
#
# Array of coreutils to include within the runtime environment
#
COREUTILS="cat chgrp chmod chown chroot cp cut dd df dir du head id install link ln ls mkdir mktemp mv pathchk pwd readlink realpath rm rmdir shred sort split stat sum tail tee touch tr truncate tsort unlink wc"
#
# Array of binaries to derive library paths
#
LIB_BINS="bash ls gpg grep"

#
# Main function
#
main() {	
    validate_args $1
    prepare_and_validate $1 
	populate_lib
	populate_bin
	populate_etc
	busybox_links
	packaged "container runtime [$1]"
}

#
# Validate and prepare staging environment
#
prepare_and_validate() {
    local agent="./target/$1/pacwrap-agent" 

    if [[ ! -f "$agent" ]]; then
        error_fatal "agent binary not built."
    fi

    BIN_PATHS=("$agent")

    clean
    mkdir -p $DEST_DIR$LIB_DIR$FAKEROOT$FAKECHROOT $DEST_DIR$BIN_DIR $DEST_DIR$ETC_DIR

    if [[ ! -d "$DEST_DIR$LIB_DIR" ]] || [[ ! -d $DEST_DIR$BIN_DIR ]]; then
		error_fatal "'$DEST_DIR': directory not found."
	fi

    for bin in $LIB_BINS; do
        local path=$(type -P $bin)

        [[ -z $path ]] && error_fatal "'$bin' dependency not fulfilled"

        BIN_PATHS+=("$path")
    done
}

#
# Clean build artifacts
#
clean() {
	if [[ -d "$DEST_DIR" ]]; then
		rm -r "$DEST_DIR"
		mkdir -p "$DEST_DIR"
		cleaned "container runtime"
	fi
}

#
# Populate libraries for container runtime
#
populate_lib() {
	copy_libs ${BIN_PATHS[@]}
	cp -L $FAKEROOT_SRC $FAKEROOT_DEST
	cp -L $FAKECHROOT_SRC $FAKECHROOT_DEST
	ln -s .$FAKEROOT/libfakeroot.so $DEST_DIR$LIB_DIR/libfakeroot.so
	ln -s .$FAKEROOT$FAKECHROOT/libfakechroot.so $DEST_DIR$LIB_DIR/libfakechroot.so

    # Remove debuglink section, to ensure the Arch Build System doesn't complain
    for lib in $(find $DEST_DIR$LIB_DIR -maxdepth 3 -type f -printf "%p "); do
        objcopy --remove-section=.gnu_debuglink $lib
    done
}

#
# Populate binaries for container runtime 
#
populate_bin() {
	cp ${BIN_PATHS[0]} $DEST_DIR$BIN_DIR/agent
	copy_bins $BIN_UTILS $COREUTILS 
	ln -s bash $DEST_DIR$BIN_DIR/sh
	ln -s ld-linux-x86-64.so.2 $DEST_DIR$BIN_DIR/ld-linux.so.2
	ln -s ../lib64/ld-linux-x86-64.so.2 $DEST_DIR$BIN_DIR/ld.so
}

#
# Populate /etc directory for container runtime
#
populate_etc() {
	echo -e "#\n# /etc/bash.bashrc\n#\n# pacwrap runtime\n#\n\n${PROFILE_PS1}\nbind -x $'\"\\C-l\":clear;'\ncd \$HOME\n" > $DEST_DIR$ETC_DIR/bash.bashrc
	sed -n 12,20p $DIST_SRC/bash.bashrc >> $DEST_DIR$ETC_DIR/bash.bashrc
	echo -e "#\n# /etc/profile - busybox env\n#\n# pacwrap runtime\n#\n\n$PROFILE_PS1\n" > $DEST_DIR$ETC_DIR/profile
	echo -e 'printf "\033]0;%s@%s\007" "${USER}" "${HOSTNAME%%.*}"\ncd $HOME' >> $DEST_DIR$ETC_DIR/profile
}

#
# Populate busybox links
#
busybox_links() {
    for applet in $(busybox --list); do
        if [[ "${COREUTILS[@]}" == *$applet* ]] ||
           [[ "${BIN_UTILS[@]}" == *$applet* ]] ||
           [[ $applet == "busybox" ]]; then
                continue
        fi

		ln -s busybox ./dist/runtime/bin/$applet
	done
}

#
# Copy libraries
#
# $@: takes an array of system library paths
#
copy_libs() {
	for path in ${@}; do 
        ldd $path | sed -e "s/.*=> //g;s/ (.*)//g;s/\t.*//g" | xargs cp -Lt $DEST_DIR$LIB_DIR
    done
}

#
# Copy binaries
#
# $@: takes an array of system binaries located in /usr/bin
#
copy_bins() {
	for bin in ${@}; do 
        cp $(type -P $bin) $DEST_DIR$BIN_DIR/$bin

        if [[ $bin == "fakeroot" ]]; then 
            continue
        fi

        # Remove debuglink section, to ensure the Arch Build System doesn't complain 
        objcopy --remove-section=.gnu_debuglink $DEST_DIR$BIN_DIR/$bin
    done	
}

main $@