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package File::KDBX::Cipher::Stream;
# ABSTRACT: A cipher stream encrypter/decrypter
use warnings;
use strict;
use Crypt::Digest qw(digest_data);
use File::KDBX::Constants qw(:cipher :random_stream);
use File::KDBX::Error;
use File::KDBX::Util qw(:class);
use Scalar::Util qw(blessed);
use Module::Load;
use namespace::clean;
extends 'File::KDBX::Cipher';
our $VERSION = '0.906'; # VERSION
has 'counter', is => 'ro', default => 0;
has 'offset', is => 'ro';
sub key_size { { Salsa20 => 32, ChaCha => 32 }->{$_[0]->{algorithm} || ''} // 0 }
sub iv_size { { Salsa20 => 8, ChaCha => 12 }->{$_[0]->{algorithm} || ''} // -1 }
sub block_size { 1 }
sub init {
my $self = shift;
my %args = @_;
if (my $uuid = $args{uuid}) {
if ($uuid eq CIPHER_UUID_CHACHA20 && length($args{iv}) == 16) {
# extract the counter
my $buf = substr($self->{iv}, 0, 4, '');
$self->{counter} = unpack('L<', $buf);
}
elsif ($uuid eq CIPHER_UUID_SALSA20) {
# only need eight bytes...
$self->{iv} = substr($args{iv}, 8);
}
}
elsif (my $id = $args{stream_id}) {
my $key_ref = ref $args{key} ? $args{key} : \$args{key};
if ($id == STREAM_ID_CHACHA20) {
($self->{key}, $self->{iv}) = unpack('a32 a12', digest_data('SHA512', $$key_ref));
}
elsif ($id == STREAM_ID_SALSA20) {
($self->{key}, $self->{iv}) = (digest_data('SHA256', $$key_ref), STREAM_SALSA20_IV);
}
}
return $self;
}
sub crypt {
my $self = shift;
my $stream = $self->_stream;
return join('', map { $stream->crypt(ref $_ ? $$_ : $_) } grep { defined } @_);
}
sub keystream {
my $self = shift;
return $self->_stream->keystream(@_);
}
sub dup {
my $self = shift;
my $class = blessed($self);
my $dup = bless {%$self, @_}, $class;
delete $dup->{stream};
return $dup;
}
sub _stream {
my $self = shift;
$self->{stream} //= do {
my $s = eval {
my $pkg = 'Crypt::Stream::'.$self->algorithm;
my $counter = $self->counter;
my $pos = 0;
if (defined (my $offset = $self->offset)) {
$counter = int($offset / 64);
$pos = $offset % 64;
}
load $pkg;
my $s = $pkg->new($self->key, $self->iv, $counter);
# seek to correct position within block
$s->keystream($pos) if $pos;
$s;
};
if (my $err = $@) {
throw 'Failed to initialize stream cipher library',
error => $err,
algorithm => $self->{algorithm},
key_length => length($self->key),
iv_length => length($self->iv),
iv => unpack('H*', $self->iv),
key => unpack('H*', $self->key);
}
$s;
};
}
sub encrypt { goto &crypt }
sub decrypt { goto &crypt }
sub finish { delete $_[0]->{stream}; '' }
1;
__END__
=pod
=encoding UTF-8
=head1 NAME
File::KDBX::Cipher::Stream - A cipher stream encrypter/decrypter
=head1 VERSION
version 0.906
=head1 SYNOPSIS
use File::KDBX::Cipher::Stream;
my $cipher = File::KDBX::Cipher::Stream->new(algorithm => $algorithm, key => $key, iv => $iv);
=head1 DESCRIPTION
A subclass of L<File::KDBX::Cipher> for encrypting and decrypting data using a stream cipher.
=head1 ATTRIBUTES
=head2 counter
$counter = $cipher->counter;
Get the initial counter / block count into the keystream.
=head2 offset
$offset = $cipher->offset;
Get the initial byte offset into the keystream. This has precedence over L</counter> if both are set.
=head1 METHODS
=head2 crypt
$ciphertext = $cipher->crypt($plaintext);
$plaintext = $cipher->crypt($ciphertext);
Encrypt or decrypt some data. These ciphers are symmetric, so encryption and decryption are the same
operation. This method is an alias for both L<File::KDBX::Cipher/encrypt> and L<File::KDBX::Cipher/decrypt>.
=head2 keystream
$stream = $cipher->keystream;
Access the keystream.
=head2 dup
$cipher_copy = $cipher->dup(%attributes);
Get a copy of an existing cipher with the counter reset, optionally applying new attributes.
=head1 BUGS
Please report any bugs or feature requests on the bugtracker website
L<https://github.com/chazmcgarvey/File-KDBX/issues>
When submitting a bug or request, please include a test-file or a
patch to an existing test-file that illustrates the bug or desired
feature.
=head1 AUTHOR
Charles McGarvey <ccm@cpan.org>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2022 by Charles McGarvey.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut
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