#!/usr/local/bin/perl

use diagnostics;
use strict;
use warnings;
use Getopt::Long;
use Crypt::CBC;    # CBC automatically loads Rainbow for us

my ($encrypt, $decrypt, $help);
GetOptions("encrypt" => \$encrypt, "decrypt" => \$decrypt,
    "help" => \$help);

sub usage
{
    print "USAGE:\n";
    print "    $0 --encrypt file1 > outputfile\n";
    print "    $0 --decrypt file1 > outputfile\n\n";
    print "ENCRYPTION EXAMPLE:\n";
    print "    $0 --encrypt cbc-mode > cbc-mode.enc\n\n";
    print "Encrypted file is \"cbc-mode.enc\"\n\n";
    print "DECRYPTION EXAMPLE:\n";
    print "    $0 --decrypt cbc-mode.enc > cbc-mode2\n\n";
    print "Decrypted file is \"cbc-mode2\"\n\n";
    exit 0;
}

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;
}

&usage() if (!$encrypt and !$decrypt);
&usage() if ($help);

my $key = &get_input("password");

# For better security, IV must be randomly
# generated AND must be used ONLY ONCE!
# So, this example is *very* weak!
my $IV = pack "H32", "000102030405060708090a0b0c0d0e0f";

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

local $/ = undef;   # slurp whole file
chomp $ARGV[0];
open INFILE, $ARGV[0];
$_ = <INFILE>;
close INFILE;

my $output;

$output = $cipher->encrypt($_) if ($encrypt);
$output = $cipher->decrypt($_) if ($decrypt);
print $output;    # output to screen