fakesudo

#!/bin/bash

if ! [ "x$FAKESUDO" = x ]; then
    [ "x$1" = x ] || exec "$@"
    echo "You are already in a 'fakesudo' environment." 1>&2
    exit 1
fi

if ! [ "$UID" -gt 0 ]; then
    echo "Do not run 'fakesudo' as root." 1>&2
    exit 1
fi

MNT="/tmp/fakesudo.$UID/mnt"
OVER="/tmp/fakesudo.$UID/over"
DATA="$HOME/.fakesudo"

if ! grep -q "$MNT" /proc/mounts; then
    echo "Setting up unionfs at $MNT..." 1>&2

    mkdir -p "$MNT" "$DATA" || exit 1

    rm -rf "$OVER" || true
    mkdir "$OVER"{,/usr,/usr/bin,/bin,/sbin} || exit 1

    ln -s /bin/true "$OVER/sbin/su"
    ln -s /bin/true "$OVER/bin/su"
    ln -s /bin/true "$OVER/usr/bin/su"

    echo '#!/bin/bash
        [ "x$1" = x ] || exec "$@"
        exit 0
    ' > "$OVER/bin/sudo"
    chmod +x "$OVER/bin/sudo"
    ln -s "../../bin/sudo" "$OVER/usr/bin/sudo"

    echo '#!/bin/bash
        LD_TRACE_LOADED_OBJECTS=1 exec "$@"
    ' > "$OVER/usr/bin/ldd"
    chmod +x "$OVER/usr/bin/ldd"

    OPTS="cow,uid=$(id -u),gid=$(id -g),suid,dev"
    if unionfs --help 2>&1 | grep -q symlink_prefix; then
        OPTS="$OPTS,symlink_prefix=$MNT"
    fi
    if ulimit -n 10000 >/dev/null 2>&1; then
        OPTS="$OPTS,max_files=10000"
    fi

    unionfs -o "$OPTS" "$OVER=ro:$DATA=rw:/=ro" "$MNT" || exit 1
fi

function get_excludes() {
    find / -mindepth 1 -maxdepth 1 | \
        grep -E -v '^/(bin|boot|etc|lib|opt|root|run|sbin|usr|var)?($|/)'
    echo /opt/google/chrome/chrome-sandbox
    echo -n /usr/lib/chromium/chromium-sandbox
}

export FAKECHROOT_EXCLUDE_PATH="$(get_excludes | tr $'\n' :)"
export FAKECHROOT_CMD_SUBST="/sbin/ldconfig=$MNT/bin/true"

START_CMD='
cd "$1"
shift
export FAKESUDO=true
exec fakeroot -u -- "$@"
'

exec fakechroot chroot "$MNT" \
    /bin/bash -l -c "$START_CMD" - "$(pwd)" "$@"