package Mail::DKIM::Key;
use strict;
use warnings;
# ABSTRACT: Represents a DKIM Key
our $VERSION = '1.20200907'; # VERSION

# Copyright 2006 Jason Long. All rights reserved.
#
# Copyright (c) 2004 Anthony D. Urso. All rights reserved.
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.

sub cork {
    my $self = shift;

    (@_)
      and $self->{'CORK'} = shift;

    $self->{'CORK'}
      or $self->convert;

    $self->{'CORK'};
}

sub data {
    my $self = shift;

    (@_)
      and $self->{'DATA'} = shift;

    $self->{'DATA'};
}

sub errorstr {
    my $self = shift;

    (@_)
      and $self->{'ESTR'} = shift;

    $self->{'ESTR'};
}

sub size {
    my $self = shift;

    return $self->cork->size * 8;
}

sub type {
    my $self = shift;

    (@_)
      and $self->{'TYPE'} = shift;

    $self->{'TYPE'};
}

sub calculate_EM {
    my ( $digest_algorithm, $digest, $emLen ) = @_;

    # this function performs DER encoding of the algorithm ID for the
    # hash function and the hash value itself
    # It has this syntax:
    #      DigestInfo ::= SEQUENCE {
    #          digestAlgorithm AlgorithmIdentifier,
    #          digest OCTET STRING
    #      }

    # RFC 3447, page 42, provides the following octet values:
    my %digest_encoding = (
        'SHA-1'   => pack( 'H*', '3021300906052B0E03021A05000414' ),
        'SHA-256' => pack( 'H*', '3031300d060960864801650304020105000420' ),
    );

    defined $digest_encoding{$digest_algorithm}
      or die "Unsupported digest algorithm '$digest_algorithm'";

    my $T    = $digest_encoding{$digest_algorithm} . $digest;
    my $tLen = length($T);

    if ( $emLen < $tLen + 11 ) {
        die 'Intended encoded message length too short.';
    }

    my $PS = chr(0xff) x ( $emLen - $tLen - 3 );
    my $EM = chr(0) . chr(1) . $PS . chr(0) . $T;
    return $EM;
}

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Mail::DKIM::Key - Represents a DKIM Key

=head1 VERSION

version 1.20200907

=head1 AUTHORS

=over 4

=item *

Jason Long <jason@long.name>

=item *

Marc Bradshaw <marc@marcbradshaw.net>

=item *

Bron Gondwana <brong@fastmailteam.com> (ARC)

=back

=head1 THANKS

Work on ensuring that this module passes the ARC test suite was
generously sponsored by Valimail (https://www.valimail.com/)

=head1 COPYRIGHT AND LICENSE

=over 4

=item *

Copyright (C) 2013 by Messiah College

=item *

Copyright (C) 2010 by Jason Long

=item *

Copyright (C) 2017 by Standcore LLC

=item *

Copyright (C) 2020 by FastMail Pty Ltd

=back

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.6 or,
at your option, any later version of Perl 5 you may have available.

=cut