Tomb/src/tomb

#!/bin/zsh
#
# Tomb
#
# a simple commandline tool to create and operate encrypted storage
#
# Copyleft (C) 2007-2010 Denis Roio <jaromil@dyne.org>
#
# thanks to Gabriele "Asbesto Molesto" Zaverio
# for suggesting the perfect name for this tool.
#
# This source  code is free  software; you can redistribute  it and/or
# modify it under the terms of  the GNU Public License as published by
# the Free  Software Foundation; either  version 3 of the  License, or
# (at your option) any later version.
#
# This source code 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.
# Please refer to the GNU Public License for more details.
#
# You should have received a copy of the GNU Public License along with
# this source code; if not, write to:
# Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

VERSION=0.8
DATE=Aug/2010

# standard output message routines
# it's always useful to wrap them, in case we change behaviour later
notice() { echo "[*] $1"; }
act() { echo " .  $1"; }
error() { echo "[!] $1"; }
func() { if [ $DEBUG ]; then echo "[D] $1"; fi }

# user interface (just to ask the password)
ask_password() {

    xhost 2>/dev/null
    if [ $? = 0 ]; then # we have access to the X display
	
	if [ -x /usr/bin/ssh-askpass ]; then # debian has this
	    export scolopendro="`ssh-askpass "Tomb: provide the password to unlock"`"
	    return
	fi

    else # we'll collect the password from commandline
	
	act "Tomb: provide the password to unlock"
	echo -n " >  "
	read -s scolopendro
	export scolopendro
    fi

    # just in case we'd like to have dialog supported too:
    # 	    dialog --backtitle "This file is encrypted for privacy protection" \
    # 		--title "Security check" --insecure \
    # 		--passwordbox "Enter password:" 10 30 2> /var/run/.scolopendro
	    
}

# checks if a file is writable
# differs from -w coz returns true if does not exist but can be created
is_writable() { # arg: filename

  file=$1
  writable=false

  if [ -r $file ]; then # file exists

    if [ -w $file ]; then writable=true; fi

  else # file does not exist

    touch $file 1>/dev/null 2>/dev/null
    if [ $? = 0 ]; then
      writable=true
      rm $file
    fi 

  fi

  if [ x$writable = xtrue ]; then
    echo "true"
  else
    echo "false"
  fi
}

# appends a new line to a text file, if not duplicate
# it sorts alphabetically the original order of line entries
# defines the APPEND_FILE_CHANGED variable if file changes
append_line() { # args:   file    new-line

    # first check if the file is writable
    # this also creates the file if doesn't exists
    if [ `is_writable $1` = false ]; then
      error "file $1 is not writable"
      error "can't insert line: $2"
      return
    fi

    tempfile="`basename $1`.append.tmp"

    # create a temporary file and add the line there
    cp $1 /tmp/$tempfile
    echo "$2" >> /tmp/$tempfile

    # sort and uniq the temp file to temp.2
    cat /tmp/$tempfile | sort | uniq > /tmp/${tempfile}.2

    SIZE1="`ls -l /tmp/$tempfile | awk '{print $5}'`"
    SIZE2="`ls -l /tmp/${tempfile}.2 | awk '{print $5}'`"
    if [ $SIZE != $SIZE ]; then
      # delete the original
      rm -f $1
      # replace it
      cp -f /tmp/${tempfile}.2 $1
      # signal the change
      APPEND_FILE_CHANGED=true
    fi

    # remove the temporary files
    rm -f /tmp/$tempfile
    rm -f /tmp/${tempfile}.2
     
    # and we are done
}


PATH=/usr/bin:/usr/sbin:/bin:/sbin   

############################
### main()
###

notice "Tomb  -  simple commandline tool for encrypted storage"
act "version $VERSION ($DATE) by Denis J. Roio <jaromil@dyne.org>"
act ""
func "invoked with args \"$*\" "
func "running on `date`"

OPTS=`getopt -o hvs:k: -n 'tomb' -- "$@"`

while true; do
    case "$1" in
	-h)
	    notice "Syntax: tomb [options] command [file] [mountpoint]"
	    act ""
            notice "Options:"
	    act "-h     print this help"
	    act "-v     print out the version information for this tool"
	    act "-s     size of the storage file when creating one (in MBytes)"
	    act "-k     path key to be used for decryption (defaults in ~/.tomb)"
	    act ""
            notice "Commands:"
            act "format     format a PARTITION with NAME and generate keys"
	    act "create     create a new encrypted storage FILE and keys"
	    act "mount      mount an existing storage FILE on MOUNTPOINT"
            act "umount     unmounts a mounted storage MOUNTPOINT"
	    echo; exit 2 ;;
	-v)
	    # print out the GPL license in this file
	    cat $0 | awk '
BEGIN { license=0 }
/^# This source/  { license=1 }
{ if(license==1) print " " $0 }
/MA 02139, USA.$/ { license=0 }
'
	    act ""
	    exit 0 ;;
        -s) SIZE=$2; shift 2 ;;
	-k) KEY=$2; shift 2 ;;
	--) shift; break ;;
	*)  CMD=$1; FILE=$2; MOUNT=$3; break ;;
    esac
done

if [ -z $CMD ]; then
    error "first argument missing, use -h for help"
    exit 0
fi

func "command: $CMD for file $FILE"

tombdir=${HOME}/.tomb
tombtab=${tombdir}/fstab
if ! [ -r ${tombtab} ]; then
    act "creating tomb filesystem tab in your home"
    mkdir -p ${HOME}/.tomb
    echo "# entombed filesystem information, see man tomb" >          ${tombtab}
    echo "# format here is similar to the system wide fstab" >>       ${tombtab}
    echo "# <file system> <mount point> <type> <options> <key>" >>    ${tombtab}
fi

format_tomb() {
    notice "Formatting partition $FILE as an encrypted storage"
    act "give it a name:"
    read -s fsname

    act "  `fdisk -l | grep ${FILE}`"
    mkdir -p /tmp/tomb

    modprobe dm-crypt
    modprobe aes-i586

    act "Generating secret key..."
    key="`basename ${FILE}`"
    mkdir -p ${HOME}/.tomb
    
    cat /dev/urandom | strings | dd bs=1 count=256 of=/tmp/tomb/secret
    notice "Setup your secret key file ${key}.gpg"
	# here user is prompted for password
    gpg -o "${HOME}/.tomb/${key}.gpg" --no-options --openpgp -c -a /tmp/tomb/secret
    while [ $? = 2 ]; do
	gpg -o "${HOME}/.tomb/${key}.gpg" --no-options --openpgp -c -a /tmp/tomb/secret
    done
    
    act "formatting Luks partition"
        # dm-crypt only supports sha1
        # but we can use aes-cbc-essiv with sha256 for better security
        # see http://clemens.endorphin.org/LinuxHDEncSettings
    cryptsetup --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat ${FILE} /tmp/tomb/secret
    if ! [ $? = 0 ]; then
	act "operation aborted."
	exit 0
    fi
   
    
    cryptsetup --key-file /tmp/tomb/secret --batch-mode --cipher aes luksOpen ${FILE} tomb.tmp

    rm -f /tmp/tomb/secret

    cryptsetup luksDump ${FILE}

    mkfs.ext3 -F -L "${fsname}" -j /dev/mapper/tomb.tmp

    if [ $? = 0 ]; then
	act "OK, encrypted partition succesfully formatted with Ext3 filesystem"
    else
	act "error formatting ${FILE} Ext3 filesystem"
    fi

    cryptsetup luksClose tomb.tmp

    notice "done formatting $FILE encrypted partition (using Luks dm-crypt AES/SHA256)"
    act "encrypted key stored in file ${tombdir}/${key}.gpg"
    append_line ${tombtab} \
	"${FILE} ${tombdir}/`basename ${FILE}` aes-cbc-essiv:sha256 none ${tombdir}/${key}.gpg"
}
    
create_tomb() {

    if [ -z $SIZE ]; then
	error "size is not specified, please use -s option when creating a storage file"
	exit 0
    else
	act "size set to $SIZE MB"
    fi
    
    SIZE_4k=`expr \( $SIZE \* 1000 \) / 4`
    notice "generating file of ${SIZE}Mb (${SIZE_4k} blocks of 4Kb)"
    act "dd if=/dev/zero of=${FILE} bs=4k count=$SIZE_4k"
#   now with progress bar!
    dd if=/dev/zero bs=4k count=${SIZE_4k} of=${FILE}
    
    if [ $? = 0 -a -e ${FILE} ]; then
	act "OK: `ls -l ${FILE}`"
    else
	error "Error creating the nest file ${FILE} : (dd if=/dev/zero of=${FILE} bs=4k count=$SIZE_4k)"
	sleep 4
	exit 0
    fi

    mkdir -p /tmp/tomb

    modprobe dm-crypt
    modprobe aes-i586

    nstloop=`losetup -f` # get the number for next loopback device
    losetup -f ${FILE}   # allocates the next loopback for our file

    act "Generating secret key..."
    
    cat /dev/urandom | strings | dd bs=1 count=256 of=/tmp/tomb/secret
    clear
    notice "Setup your secret key file ${FILE}.gpg"
	# here user is prompted for password
    gpg -o "${FILE}.gpg" --no-options --openpgp -c -a /tmp/tomb/secret
    while [ $? = 2 ]; do
	gpg -o "${FILE}.gpg" --no-options --openpgp -c -a /tmp/tomb/secret
    done
    
    act "formatting Luks mapped device"
        # dm-crypt only supports sha1
        # but we can use aes-cbc-essiv with sha256 for better security
        # see http://clemens.endorphin.org/LinuxHDEncSettings
    cryptsetup --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat ${nstloop} /tmp/tomb/secret
    if ! [ $? = 0 ]; then
	act "operation aborted."
	exit 0
    fi
 
    act "formatting Ext3 filesystem"
    
    cryptsetup --key-file /tmp/tomb/secret --batch-mode --cipher aes luksOpen ${nstloop} tomb.tmp

    rm -f /tmp/tomb/secret

    cryptsetup luksDump ${nstloop}

    mkfs.ext3 -F -j -L "dyne:nest" /dev/mapper/tomb.tmp

    if [ $? = 0 ]; then
	act "OK, encrypted storage succesfully formatted with Ext3 filesystem"
    else
	act "error formatting storage file with Ext3 filesystem"
    fi

    cryptsetup luksClose tomb.tmp
    losetup -d ${nstloop}

    notice "done creating $FILE encrypted storage (using Luks dm-crypt AES/SHA256)"
}

# mount_crypto() {
#     if ! [ -r $FILE ]; then
# 	error "file or partition $FILE does not exists"
# 	exit 0
#     fi
#     # check if its a file or partition
#     file ${FILE} | grep block > /dev/null
#     if [ $? = 0 ]; then
# 	act "$FILE is a partition"
# 	mount_crypto_partition
#     else
# 	act "$FILE is a loopback file"
# 	mount_crypto_file
#     fi
# }

mount_tomb() {

    if [ -z $KEY ]; then
	enc_key="~/.tomb/`basename $FILE`"
    else
	enc_key="$KEY"
    fi

    notice "mounting $FILE on mountpoint $MOUNT"
    if [ -z $MOUNT ]; then
	error "you need to specify a MOUNTPOINT for the mount command"
	exit 0
    fi
    if ! [ -x $MOUNT ]; then
	error "mountpoint $MOUNT doesn't exist"
	exit 0
    fi

    nstloop=`losetup -f`
    losetup -f ${FILE}
    
    act "check for a valid LUKS encrypted device"
    cryptsetup isLuks ${nstloop}
    if [ $? = 0 ]; then # it's a LUKS encrypted nest, see cryptsetup(1)
	
        # check if key file is present
	if ! [ -r "${enc_key}" ]; then
	    error "encryption key ${enc_key} not found"
	    error "use -k option to specify which key to use"
	    losetup -d ${nstloop}
	    sleep 5
	    return
	fi
	
	modprobe dm-crypt
	modprobe aes-i586
	
	# save date of mount in minutes since 1970
	mapdate="`date +%s`"
	mapdate="`echo ${mapdate}/60 | bc -l | cut -d. -f1`"

	mapper="tomb.`basename $FILE | cut -d. -f1`.$mapdate.`basename $nstloop`"
	
	notice "Password is required for key ${enc_key}"
	for c in 1 2 3; do
	    
	    ask_password

	    echo "${scolopendro}" \
		| gpg --passphrase-fd 0 --no-tty --no-options \
		      -d "${enc_key}" 2>/dev/null \
		| cryptsetup --key-file - luksOpen ${nstloop} ${mapper}
	    
	    unset scolopendro
	    
	    if [ -r /dev/mapper/${mapper} ]; then
		break;  # password was correct
	    fi
	    
	done
	
	if ! [ -r /dev/mapper/${mapper} ]; then
	    error "failure mounting the encrypted file"
	    tail /var/log/messages
	    losetup -d ${nstloop}
	    return
	fi
	
	act "encrypted storage filesystem check"
	fsck.ext3 -p -C0 /dev/mapper/${mapper}



	mount -t ext3 /dev/mapper/${mapper} ${MOUNT}
# TODO: possible mount options to try out:
#  -o rw,noatime,nodev,data=writeback,commit=30
#  -o rw,noatime,nodev

	notice "encrypted storage $FILE succesfully mounted on $MOUNT"
	append_line /var/run/tombs "${MOUNT} ${mapper} ${nstloop}"

    else
	
	error "$FILE is not a valid Luks encrypted storage file"

    fi
}

umount_tomb() {

    if [ -z $FILE ]; then

	how_many_tombs="`ls /dev/mapper/tomb* 2>/dev/null | wc -w`"
	if [ $how_many_tombs = 0 ]; then
	    error "there is no tomb found to be mounted"
	    return
	elif [ $how_many_tombs = 1 ]; then
	    mapper=`ls /dev/mapper/tomb* 2>/dev/null`
	    FILE=`mount | grep $mapper | awk '{print $3}'`
	fi

    else

	mapper=`mount | grep $FILE | awk '{print $1}'`

    fi

    if [ "$mapper" = "" ]; then
	error "$FILE is not mounted"
	return
    fi

    mapper=`basename $mapper`

    if ! [ -r /dev/mapper/${mapper} ]; then
	error "tomb doesn't seems to be mounted:"
	error "${mapper} is not present in /dev/mapper"
	exit 1
    fi

    umount ${FILE}
    if ! [ $? = 0 ]; then
	error "error occurred in umount ${FILE}"
	exit 0
    fi

    cryptsetup luksClose ${mapper}
    if ! [ $? = 0 ]; then
	error "error occurred in cryptsetup luksClose ${mapper}"
	exit 0
    fi

    losetup -d "/dev/`echo $mapper | cut -d. -f4`"

    # echo ${nstloop} | grep loop 1>/dev/null 2>/dev/null
    # # if it's a loopback then we need to do losetup -d
    # if [ $? = 0 ]; then
    # 	losetup -d ${nstloop}
    # 	if ! [ $? = 0 ]; then
    # 	    error "error occurred in losetup -d ${nstloop}"
    # 	    exit 0
    # 	fi
    # fi

    notice "crypt storage ${mapper} unmounted"
}
	

case "$CMD" in
    create)   create_tomb ;;
    format)   format_tomb ;;
    mount)    mount_tomb  ;;
    umount)   umount_tomb ;;
    unmount)  umount_tomb ;;
    *) error "command \"$CMD\" not recognized"
	act "try -h for help"
	;;
esac