package Mail::DKIM::SignerPolicy;
use strict;
use warnings;
our $VERSION = '1.20230911'; # VERSION
# ABSTRACT: determines signing parameters for a message

# Copyright 2005-2006 Messiah College. All rights reserved.
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# Written by Jason Long <jlong@messiah.edu>

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Mail::DKIM::SignerPolicy - determines signing parameters for a message

=head1 VERSION

version 1.20230911

=head1 DESCRIPTION

A "signer policy" is an object, class, or function used by
L<Mail::DKIM::Signer> to determine what signatures to add to the
current message. To take advantage of signer policies, create your
own Perl class that extends the L<Mail::DKIM::SignerPolicy> class.
The only method you need to implement is the apply() method.

The apply() method takes as a parameter the L<Mail::DKIM::Signer> object.
Using this object, it can determine some properties of the message (e.g.
what the From: address or Sender: address is). Then it sets various
signer properties as desired. The apply() method should
return a nonzero value if the message should be signed. If a false value
is returned, then the message is "skipped" (i.e. not signed).

Here is an example of a policy that always returns the same values:

  package MySignerPolicy;
  use base 'Mail::DKIM::SignerPolicy';

  sub apply
  {
      my $self = shift;
      my $signer = shift;
  
      $signer->algorithm('rsa-sha1');
      $signer->method('relaxed');
      $signer->domain('example.org');
      $signer->selector('selector1');
      $signer->key_file('private.key');
  
      return 1;
  }

To use this policy, simply specify the name of the class as the Policy
parameter...

  my $dkim = Mail::DKIM::Signer->new(
                  Policy => 'MySignerPolicy',
             );

=head1 ADVANCED

You can also have the policy actually build the signature for the Signer
to use. To do this, call the signer's add_signature() method from within
your apply() callback. E.g.,

  sub apply
  {
      my $self = shift;
      my $signer = shift;
  
      $signer->add_signature(
              new Mail::DKIM::Signature(
                  Algorithm => $signer->algorithm,
                  Method => $signer->method,
                  Headers => $signer->headers,
                  Domain => $signer->domain,
                  Selector => $signer->selector,
              ));
      return;
  }

Again, if you do not want any signatures, return zero or undef. If you
use add_signature() to create a signature, the default signature will
not be created, even if you return nonzero.

=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
