#!/usr/bin/env perl

##
## Author......: See docs/credits.txt
## License.....: MIT
##

use strict;
use warnings;

use Crypt::Mode::CBC;
use Crypt::PBKDF2;
use Digest::SHA qw (sha256 sha256_hex);

sub module_constraints { [[0, 256], [32, 32], [0, 55], [32, 32], [-1, -1]] }

sub module_generate_hash
{
  my $word  = shift;
  my $salt  = shift;
  my $iter  = shift // 100000;
  my $iv    = shift // random_hex_string (2*16);
  my $plain = shift // random_hex_string (2*1024);

  my $b_iv    = pack ('H*', $iv);
  my $b_salt  = pack ('H*', $salt);
  my $b_plain = pack ('H*', $plain);

  my $kdf = Crypt::PBKDF2->new
  (
    hash_class => 'HMACSHA1',
    iterations => $iter,
    output_len => 32
  );

  my $pass_hash = sha256 ($word);
  my $key       = $kdf->PBKDF2 ($b_salt, $pass_hash);
  my $cbc       = Crypt::Mode::CBC->new ('AES', 0);
  my $b_cipher  = $cbc->encrypt ($b_plain, $key, $b_iv);
  my $cipher    = unpack ('H*', $b_cipher);
  my $checksum  = sha256_hex ($b_plain);

  my $hash = '$odf$'."*1*1*$iter*32*$checksum*16*$iv*16*$salt*0*$cipher";

  return $hash;
}

sub module_verify_hash
{
  my $line = shift;

  my ($hash, $word) = split (':', $line);

  return unless defined $hash;
  return unless defined $word;

  $word = pack_if_HEX_notation ($word);

  # tokenize
  my @data = split ('\*', $hash);

  next unless scalar @data == 12;

  my $signature   = shift @data;
  my $cipher_type = shift @data;
  my $cs_type     = shift @data;
  my $iter        = shift @data;
  my $cs_len      = shift @data;
  my $cs          = shift @data;
  my $iv_len      = shift @data;
  my $iv          = shift @data;
  my $salt_len    = shift @data;
  my $salt        = shift @data;
  my $unused      = shift @data;
  my $cipher      = shift @data;

  # validate
  return unless $signature   eq '$odf$';
  return unless $cipher_type eq '1';
  return unless $cs_type     eq '1';
  return unless $cs_len      eq '32';
  return unless $iv_len      eq '16';
  return unless $salt_len    eq '16';
  return unless $unused      eq '0';
  return unless defined $cipher;

  # decrypt
  my $b_iv     = pack ('H*', $iv);
  my $b_salt   = pack ('H*', $salt);
  my $b_cipher = pack ('H*', $cipher);

  my $kdf = Crypt::PBKDF2->new
  (
    hash_class => 'HMACSHA1',
    iterations => $iter,
    output_len => 32
  );

  my $pass_hash = sha256 ($word);
  my $key       = $kdf->PBKDF2 ($b_salt, $pass_hash);
  my $cbc       = Crypt::Mode::CBC->new ('AES', 0);
  my $b_plain   = $cbc->decrypt ($b_cipher, $key, $b_iv);
  my $plain     = unpack ('H*', $b_plain);

  return module_generate_hash ($word, $salt, $iter, $iv, $plain);
}

1;