YAD (ex zenity) front-end to mcrypt and mdecrypt

#!/bin/bash

# A Front-End to mcrypt and mdecrypt.
# Store the executable script as xcrr and make a symbolic link
# to the same file as xcrrd.
# xcrr will encrypt, xcrrd will decrypt.

# ©2016 Michael Uplawski <michael.uplawski@uplawski.eu>
# Use at your own risk, modify as you please.

# set your preferred crypto- and hash algorithm. Verify,
# that they are supported by mcrypt
DEF_ALGO='rijndael-256'
DEF_HASH='sha256'

# Some arrays will facilitate adaptations to the current
# version of mcrypt

declare -a FILES
declare -a HASHES
declare -a ALGOS

# get the supported cryptographic algorithms
ALGOS=($(mcrypt --list|cut -d\( -f1|tr -d "[:cntrl:]"))

# get the supported hash algorithms
HASHES=($(mcrypt --list-hash|cut -d':' -f2|tr -d "[:blank:]"|tr "\n" " "))

# set the names of the supported modes in a string
# variable. These values are not yet presented by
# mcrypt itself. CFB is the default, hence the '^'.
MODES="ECB ^CFB OFB nOFB CBX STREAM"

# default action (script xcrr)
ACTION="encrypt"
ICON="encrypt.png"

# modify action do decrypt, if the script is called
# as xcrrd
if [ "xcrrd" == `basename "$0"` ]
then
    ACTION="decrypt"
    ICON="decrypt.png"
fi

# find the default algorithm and mark it
# with '^' for yad
AL=''
for i in `seq 0 50`
do
    if [ ${ALGOS[$i]} != ' ' ]
    then
        a=${ALGOS[$i]}
        if [ "$DEF_ALGO" == $a ]
        then
            a="^$a"
        fi
        AL="$a $AL"
    else
        break
    fi
done

# find the default hash and mark it with '^'
# for yad
HS=''
for i in `seq 0 50`
do
    if [ ${HASHES[$i]} != ' ' ]
    then
        h=${HASHES[$i]}
        if [ "sha256" == $h ]
        then
            h="^$h"
        fi
        HS="$h $HS"
    else
        break
    fi
done

# call yad and present the user-interface
FILES=($(yad --title "$ACTION" --image="$ICON" --window-icon="$ICON" --form --separator=' ' --field="File to $ACTION":FL " " --field="Key file":FL ' ' --field="Algorithm":CB "$AL" --field="Mode":CB "$MODES" --field="Hash":CB "$HS" --item-separator=' ' ))

# extrct the user-provided values
FILE=${FILES[0]}
KFILE=${FILES[1]}
ALGO=${FILES[2]}
MODE=${FILES[3]}
HASH=${FILES[4]}

# verifications and error-handling
if [ ! -e "$FILE" ]
then
    yad --image "dialog-error" --title "ERROR" --text="File $FILE does not exist"
    exit 1
fi

if [ ! -f "$FILE" ]
then
    yad --image "dialog-error" --title "ERROR" --text="$FILE is not a valid file for $ACTIONion! Aborting."
    exit 0
fi

if [ ! -e "$KFILE" ]
then
    yad --image "dialog-error"  --title "ERROR" --text="Key-file $KFILE does not exist"
    exit 1
fi

if [ ! -f "$KFILE" ]
then
    yad --image "dialog-error" --title "ERROR" --text="$KFILE is not a valid key-file! Aborting."
    exit 0
fi

# Do it.
# Remove pre-existing files if we are about to replace them anyway.

if [ "encrypt" == "$ACTION" ]
then
    if [ -e "$FILE".nc ]
    then
        rm -f "$FILE".nc
    fi

    mcrypt -a "$ALGO" -h "$HASH" -m "$MODE" -f "$KFILE" "$FILE"

    if [ -e "$FILE".nc ]
    then
        yad --image "dialog-information" --title "result" --text="encrypted file $FILE.nc has been written"
    else
        yad --image "dialog-warning"  --title "result" --text="An error occured, check console-output"
    fi
elif [ "decrypt" == "$ACTION" ]
then
    dir=`dirname $FILE`
    out=$dir/`basename "$FILE" .nc`

    if [ -e "$out" ]
    then
        rm -f "$out"
    fi
    mdecrypt -a "$ALGO" -h "$HASH" -m "$MODE" -f "$KFILE" "$FILE"

    if [ -e "$out" ]
    then
        yad --image "dialog-information" --title "result" --text="File $out has been written"
    fi
fi

# EOF