usage="
# Create can use an encrypted directory
# realative to the current working directory.
# The mountpoint is entered into /etc/fstab.
#
# All filenames are set in this script (not optional).
#
# Script takes one of three option:
# create : crate a "cryptfile"
# mount  : cryptfile via losetup and /dev/loop0 on cryptdir 
# umount: unmount /dev/loop0 unset loop
"

# Debug what is done.
#set -vx
#echo "parameter: $1"

# Specify the encryption algorithm : "twofish", "AES128", "aes-256" etc
ciphername="twofish256"
# File with encryted data:
cryptfile="cryptfile${USER}"
# mount point:
cryptdir="cryptdir" 
# Size needed for the data in kb:
cryptfilesize=100
# Fs for the cryptfile
filesystemtype=ext2


###################### create ########################

if [ "$1" == "create" ]
    then
    if [ -a "cryptfile" ]
	then
	echo "Cryptfile exists: $cryptfile"
	echo "Delete $cryptfile first."
	exit 1;
    fi

# Check if the mountpoint for the cryptfile exists
    if [ -d "$cryptdir" ]
	then
	echo "$cryptdir exists: ok" 
    else
	echo "mkdir $cryptdir" 
	mkdir $cryptdir
    #chown ${USER}:users $cryptdir
	chmod u=rwX $cryptdir
    fi

# Create a cryptfile that serves as medium for writing (like paper).
# Done only once, the cryprfile can be overrwritten, reused.
# This is where the data is, so do not delete this file later.

    echo "create: cryptfile with size $cryptfilesize K"
    dd if=/dev/urandom of=$cryptfile bs=1024 count=$cryptfilesize
    ll $cryptfile

# Module loop_fish2 has to be loaded.
    if lsmod | grep -q loop_fish2 ; then
	echo "Module loop_fish2 loaded: ok"
    else
	echo "Load module loop_fish2:"
	echo "Root Password (modprobe):"
	su -c "modprobe loop_fish2"
    fi

# Setup the encryption filter on the /dev/loop for read/write.
# The cryptfile serves as medium (like a disk device).
    echo Enter first su passwork than crypt-password:
    echo "Root Password (losetup):"
    su -c "echo \"Crypt Password (min 8)\" ; \
           losetup -d /dev/loop0 2>/dev/null ; \
           losetup -e $ciphername /dev/loop0 $cryptfile ; \
           losetup -a "

# Make a filesystem on the device, hence on the cryptfile.
# Also this is done only once as long as the cryptfile is reused.
# Fix the rights after mkfs, where root owns some dirs.
    echo "Root Password (mkfs):"
    su -c "mkfs.$filesystemtype /dev/loop0 ; \
         mount -t $filesystemtype /dev/loop0 $cryptdir ; \
           chown ${USER}:users -R $cryptdir ; \
           chmod -R go= $cryptdir ; \
	   chmod -R u=rwX $cryptdir;  \
           umount /dev/loop0 ; \
           losetup -d /dev/loop0 "

# You next edit your /etc/fstab to include the following line:
# Options ,uid=$UID,gid=$GROUPS do not work.
    echo add cryptdir to /etc/fstab 
    fstab_line="`pwd`/$cryptfile  `pwd`/$cryptdir auto  defaults,noauto,loop,encryption=$ciphername,user  0   0"
    echo $fstab_line
    echo "Root Password (/etc/fstab):"
    su -c "echo $fstab_line | cat >>/etc/fstab"

    echo "Create done."
    exit 0;
fi

###################### mount ########################

if [ "$1" == "mount" ]
    then
    echo "Mounting $cryptfile at $cryptdir"
# Setup the cryptfile-system as above, 
#    losetup -e $ciphername /dev/loop0 $cryptfile 
# mount the cryptfile with the filesytem via the /dev/loop
# su -c "mount -t $filesystemtype /dev/loop0 $cryptdir"
    
# Use the entry in /etc/fstab:
    mount $cryptdir

# Now IO to the cyptfile-system is open.
#    cd $cryptdir 

    echo "Done."
    exit 0;
fi

###################### umount ########################

if [ "$1" == "umount" ]
    then
    echo "Un-mounting $cryptfile at $cryptdir"
# unmount the /dev/loop 
#su -c "umount /dev/loop0"
# Unset the encrypted connection of /dev/loop to cryptfile.
#    su -c "losetup -d /dev/loop0"

# Use the entry in /etc/fstab:
    umount $cryptdir

    echo "Done."
    exit 0;
fi

###################### default ########################

echo "ERROR: Unknwon option"
printf "$usage\nusage:\n\n  $0 [ create | mount | umount ]\n\n"
exit 1