#!/usr/local/bin/perl

use diagnostics;
use strict;
use warnings;
use Getopt::Long;
use Crypt::CBC;

my $SRC_RAND = "/dev/urandom";

my ($encrypt, $decrypt, $help, $cipher, $blocksize);

GetOptions("encrypt" => \$encrypt, "decrypt" => \$decrypt,
           "cipher=s" => \$cipher, "blocksize=i" => \$blocksize,
           "help" => \$help);

sub syntax
{
    print "Examples:\n";
    print "$0 --encrypt --cipher=TC18 --blocksize=16 file.txt > ";
    print "file.enc\n";
    print "$0 --decrypt --cipher=TC18 --blocksize=16 file.enc > ";
    print "file.dec\n\n";
    print "$0 -e -c=TC18 -b=16 file.txt > file.txt.enc\n";
    print "$0 -d -c=TC18 -b=16 file.txt.enc > file.txt.dec\n\n";
    print "NOTE: User should know the block size (in bytes) of the ";
    print "cipher being used\n";
    exit 1;
}

sub get_input
{
    my ($message) = @_;
    local $| = 1;
    local *TTY;
    open TTY,"/dev/tty";
    my ($tkey1, $tkey2);
    system "stty -echo </dev/tty";
    do {
        print STDERR "Enter $message: "; chomp($tkey1 = <TTY>);
        print STDERR "\nRe-type $message: "; chomp($tkey2 = <TTY>);
        print STDERR "\n";
        print STDERR "\nThe two $message", "s don't match. ",
            "Please try again.\n\n" unless $tkey1 eq $tkey2;
    } until $tkey1 eq $tkey2;

    system "stty echo </dev/tty";
    close TTY;
    return $tkey1;
}

&syntax() if ($help);

if (!$encrypt and !$decrypt) {
    print "Please specify switch:\n";
    print "  --encrypt (or -e) to encrypt a file\n";
    print "  --decrypt (-d) to decrypt a file\n\n";
    print "Type $0 --help (or $0 -h) for usage examples\n";
    exit 1;
}

if (!$cipher) {
    print "Please provide a block cipher to use\n\n";
    print "Type: $0 --help (or $0 -h) for usage examples\n";
    exit 1;
}

if (!$blocksize) {
    print "Please provide the block size (in bytes)\n\n";
    print "Type $0 --help (or $0 -h) for usage examples\n";
    exit 1;
}

if ($#ARGV < 0) {
    print "Please provide a file to encrypt or decrypt\n\n";
    print "Type $0 --help (or $0 -h) for usage examples\n";
    exit 1;
}

chomp $ARGV[0];
open INFILE, $ARGV[0];
my $key = &get_input("passphrase");

my $IV;

if ($encrypt) {
    open RANDSRC, $SRC_RAND;
    read RANDSRC, $IV, $blocksize;    # generate one-time, random IV
    close RANDSRC;
    print $IV;     # make IV as 1st ciphertext block
} elsif ($decrypt) {
    read INFILE, $IV, $blocksize;
}

my $obj = Crypt::CBC->new({'key' => $key,
                                 'cipher' => $cipher,
                                 'iv' => $IV,
                                 'regenerate_key' => 1,
                                 'padding' => 'standard',
                                 'prepend_iv' => 0
                               });

#$obj->start('encrypt') if ($encrypt);
#$obj->start('decrypt') if ($decrypt);

$encrypt ? $obj->start('encrypt') : $obj->start('decrypt');

while (read(INFILE, my $buffer, 4096)) {
    print $obj->crypt($buffer);
}

close INFILE;

print $obj->finish;

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