package Spreadsheet::ParseXLSX::Decryptor::Standard;

use strict;
use warnings;

our $VERSION = '0.33'; # VERSION

# ABSTRACT: standard decryption

use base 'Spreadsheet::ParseXLSX::Decryptor';

sub decrypt {
  my $self = shift;
  my ($encryptedValue) = @_;

  my $key = $self->_generateDecryptionKey("\x00" x 4);
  my $ecb = Crypt::Mode::ECB->new($self->{cipherAlgorithm}, 0);
  return $ecb->decrypt($encryptedValue, $key);
}

sub decryptFile {
  my $self = shift;
  my ($inFile, $outFile, $bufferLength, $fileSize) = @_;

  my $key = $self->_generateDecryptionKey("\x00" x 4);
  my $ecb = Crypt::Mode::ECB->new($self->{cipherAlgorithm}, 0);

  my $inbuf;
  my $i = 0;

  while (($fileSize > 0) && (my $inlen = $inFile->read($inbuf, $bufferLength))) {
    if ($inlen < $bufferLength) {
      $inbuf .= "\x00" x ($bufferLength - $inlen);
    }

    my $outbuf = $ecb->decrypt($inbuf, $key);
    if ($fileSize < $inlen) {
      $inlen = $fileSize;
    }

    $outFile->write($outbuf, $inlen);
    $i++;
    $fileSize -= $inlen;
  }
}

sub _generateDecryptionKey {
  my $self = shift;
  my ($blockKey) = @_;

  my $hash;
  unless ($self->{pregeneratedKey}) {
    $hash = $self->{hashProc}->($self->{salt} . Encode::encode('UTF-16LE', $self->{password}));
    for (my $i = 0 ; $i < $self->{spinCount} ; $i++) {
      $hash = $self->{hashProc}->(pack('L<', $i) . $hash);
    }
    $self->{pregeneratedKey} = $hash;
  }

  $hash = $self->{hashProc}->($self->{pregeneratedKey} . $blockKey);

  my $x1 = $self->{hashProc}->(("\x36" x 64) ^ $hash);
  if (length($x1) >= $self->{keyLength}) {
    $hash = substr($x1, 0, $self->{keyLength});
  } else {
    my $x2 = $self->{hashProc}->(("\x5C" x 64) ^ $hash);
    $hash = substr($x1 . $x2, 0, $self->{keyLength});
  }

  return $hash;
}

sub verifyPassword {
  my $self = shift;
  my ($encryptedVerifier, $encryptedVerifierHash) = @_;

  my $verifier = $self->decrypt($encryptedVerifier);
  my $verifierHash = $self->decrypt($encryptedVerifierHash);

  my $verifierHash0 = $self->{hashProc}->($verifier);

  die "Wrong password: $self" unless ($verifierHash0 eq substr($verifierHash, 0, length($verifierHash0)));
}


1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Spreadsheet::ParseXLSX::Decryptor::Standard - standard decryption

=head1 VERSION

version 0.33

=for Pod::Coverage   decrypt
  decryptFile
  verifyPassword

=head1 AUTHOR

Jesse Luehrs <doy@tozt.net>

=head1 COPYRIGHT AND LICENSE

This software is Copyright (c) 2024 by Jesse Luehrs.

This is free software, licensed under:

  The MIT (X11) License

=cut
