NAME

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

VERSION

       version 1.20230212

DESCRIPTION

       A "signer policy" is an object, class, or function used by 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 Mail::DKIM::SignerPolicy class.  The only
       method you need to implement is the apply() method.

       The apply() method takes as a parameter the 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',
                    );

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.

AUTHORS

       •   Jason Long <jason@long.name>

       •   Marc Bradshaw <marc@marcbradshaw.net>

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

THANKS

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

COPYRIGHT AND LICENSE

       •   Copyright (C) 2013 by Messiah College

       •   Copyright (C) 2010 by Jason Long

       •   Copyright (C) 2017 by Standcore LLC

       •   Copyright (C) 2020 by FastMail Pty Ltd

       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.