Tomb/src/tomb

#!/bin/bash
#
# Tomb
#
# a simple commandline tool to create and operate encrypted storage
#
# Copyleft (C) 2007-2010 Denis Roio <jaromil@dyne.org>
#
# Tomb development is supported by: NOONE.
# Would you like to support it and engrave your name on this software?
# Contact me!
#
# 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

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

# 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 }

# which dd command to use
which dcfldd > /dev/null
if [ $? = 0 ]; then
    DD="dcfldd"
else
    DD=dd
fi

# which wipe command to use
which wipe > /dev/null
if [ $? = 0 ]; then
    WIPE="wipe -f -s -q"
else
    WIPE="rm -f"
fi

# usb auto detect
# tested on ubuntu 10.04 - please test and patch on other systems if you can
ask_usbkey() {
    notice "looking for key $1 on usb"
    echo -n " .  please insert your usb key "

    plugged=false
    while [ "$plugged" != "true" ]; do
	dmesg | tail -n 12 | grep -q 'new.*USB device'
	if [ $? = 0 ]; then plugged=true; fi
	echo -n "."
	sleep .5
    done

    echo
    echo -n " .  usb key inserted, opening "
    
    attached=false
    while [ "$attached" != "true" ]; do
	dmesg | tail -n 3| grep -q 'Attached.*removable disk'
	if [ $? = 0 ]; then attached=true; fi
	echo -n "."
	sleep  .5
    done

    # get the first partition
    usbpart=`dmesg |tail -n 8 | grep '  sd.:' |cut -d: -f2 |tr -d ' '`

    # what that it is mounted
    mounted=false
    while [ "$mounted" != "true" ]; do
	cat /proc/mounts | tail -n 2 | grep -q $usbpart
	if [ $? = 0 ]; then mounted=true; fi
	echo -n "."
	sleep .5
    done

    # check where it is mounted
    usbmount=`cat /proc/mounts | awk -v p=$usbpart '{ if( $1 == "/dev/" p) print $2 }'`
    echo
    act "usb key mounted on $usbmount"
    export usbkey_mount=$usbmount
    return 0
}

# 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
	    
}



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

notice "Tomb  -  simple commandline tool for encrypted storage"
act "version $VERSION ($DATE) by 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 | size]"
	    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 to the key to use for decryption"
	    act ""
            notice "Commands:"
	    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

id | grep root > /dev/null
if [ $? != 0 ]; then
    error "This program must be run as root to produce results"
    exit 1
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
    
create_tomb() {

    notice "Creating a new tomb in ${FILE}"
    if [ -z $SIZE ]; then
	if [ $MOUNT ]; then
	    SIZE=$MOUNT
	else
	    error "size is not specified, please use -s option when creating a tomb"
	    exit 0
	fi
    fi
    
    SIZE_4k=`expr \( $SIZE \* 1000 \) / 4`
    act "Generating file of ${SIZE}Mb (${SIZE_4k} blocks of 4Kb)"
#   TODO: use dd_rescue and/or dcfldd
    $DD if=/dev/urandom bs=4k count=${SIZE_4k} of=${FILE}
#    dd if=/dev/urandom bs=4k count=${SIZE_4k} of=${FILE}
    
    if [ $? = 0 -a -e ${FILE} ]; then
	act "OK: `ls -lh ${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 ${FILE}   # allocates the next loopback for our file
    keytmp=`tempfile`
    act "Generating secret key..."
    act "this operation takes time, computer use helps to gather more entropy."
    cat /dev/random | dd bs=1 count=256 of=${keytmp}

    notice "Setup your secret key file ${FILE}.gpg"
    # here user is prompted for key password
    gpg -o "${FILE}.gpg" --no-options --openpgp -c -a ${keytmp}
    while [ $? = 2 ]; do
	gpg -o "${FILE}.gpg" --no-options --openpgp -c -a ${keytmp}
    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 --batch-mode \
	--cipher aes-cbc-essiv:sha256 --key-size 256 \
	luksFormat ${nstloop} ${keytmp}

    if ! [ $? = 0 ]; then
	act "operation aborted."
	exit 0
    fi
 
    
    cryptsetup --key-file ${keytmp} --cipher aes luksOpen ${nstloop} tomb.tmp
    $WIPE ${keytmp}

    notice "Your tomb is read on ${FILE} and secured with key ${FILE}.gpg"
    act "now plug an external usb device to save the key separately:"
    ask_usbkey
    if ! [ -w ${usbkey_mount} ]; then
	error "cannot save the key in a separate place, move it yourself later."
    else
	mkdir -p ${usbkey_mount}/.tomb
	cp -v ${FILE}.gpg ${usbkey_mount}/.tomb/
	chmod -R go-rwx ${usbkey_mount}/.tomb
	rm -rf ${FILE}.gpg
    fi

#    cryptsetup luksDump ${nstloop}

    act "formatting your Tomb with Ext4 filesystem"
 
    mkfs.ext4 -q -F -j -L "`hostname`-`date +%s`" /dev/mapper/tomb.tmp

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

    sync

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

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


mount_tomb() {

    if [ -z $KEY ]; then
	enc_key="`basename ${FILE}.gpg`"
    else
	enc_key="$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

    # check if key file is present
    if ! [ -r "${enc_key}" ]; then
	error "encryption key ${enc_key} not found on disk"
	error "use -k option to specify which key to use"
	error "or provide a usb key, or press ctrl-c to abort"
	ask_usbkey
        # returns usbkey_mount, now check if the key is there
	if [ -r ${usbkey_mount}/.tomb/${enc_key} ]; then
	    enc_key=${usbkey_mount}/.tomb/${enc_key}
	    notice "key found on ${enc_key}"
	else
	    error "key is missing."
	    exit 1
	fi
    fi
    
    nstloop=`losetup -f`
    losetup -f ${FILE}
    
    act "check for a valid LUKS encrypted device"
    cryptsetup isLuks ${nstloop}
    if [ $? != 0 ]; then
 # is it a LUKS encrypted nest? see cryptsetup(1)
	error "$FILE is not a valid Luks encrypted storage file"
	exit 0
    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.ext4 -p -C0 /dev/mapper/${mapper}
    
    mount -t ext4 -o rw,noatime,nodev /dev/mapper/${mapper} ${MOUNT}
    
    notice "encrypted storage $FILE succesfully mounted on $MOUNT"
    
}

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}'`
	else
	    error "too many tombs mounted, please specify which to unmount:"
	    ls /dev/mapper/tomb*
	    echo
	    return
	fi

    else

	if ! [ -r $FILE ]; then
	    error "tomb not found: $FILE"
	    error "please specify the full /dev/mapper/tomb* path"
	    return
	fi
	mapper=$FILE
	FILE=`mount | grep $mapper | awk '{print $3}'`

    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