#!/usr/bin/perl
#
# singlepass 1.0
#
# This script will generate passwords given a Single Pass password
# and a Service Name.
#
# Copyright 2012 - Paul E. Jones <paulej@packetizer.com>
# All Rights Reserved
#

use strict;
use IO::Prompt;
use Digest::SHA qw(sha256);

#
# MAIN
#
{
    my ($single_password,
        $service_name,
        $service_password,
        $digest);

    my @pwchars = (
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
        'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
        's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F',
        'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
        'U', 'V', 'W', 'X', 'Y', 'Z'
    );

    binmode(STDIN, ":encoding(UTF-8)");
    $single_password = prompt("Single Password: ", -e => "*");
    $service_name = prompt("Service Name: ");

    if ((length($single_password) == 0) || (length($service_name) == 0))
    {
        die "Invalid input provided\n";
    }

    $digest = sha256($single_password . ":" . $service_name);

    $service_password = "";
    for(my $i=0; $i < 16; $i++)
    {
        my $j = unpack("C", substr($digest, $i, 1));
        $service_password .= $pwchars[$j % 62];
    }

    print "Service Password: $service_password\n";
}