NAME

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

VERSION

version 1.20200513.1

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.