DomainKeys Plugin

[Michael Parker]

Howdy All,

I spent a few minutes this morning working up the start of a
DomainKeys plugin.  It uses the Mail::DomainKeys perl module to
perform the various checks.  Honestly, Mail::DomainKeys may not be the
right direction.  It has zero documentation and some oddities that
might make it difficult to use in the long run.

Anyway, my knowledge of DomainKeys is almost nothing.  The plugin
follows the example of how it is used in qpsmtpd.  So, if anyone would
like to pitch in and polish this off, feel free.

Michael

=head1 NAME

Mail::SpamAssassin::Plugin::DomainKeys

=head1 SYNOPSIS

 loadplugin Mail::SpamAssassin::Plugin::DomainKeys [/path/to/DomainKeys.pm]

 full DOMAINKEY_DOMAIN eval:check_domainkeys_senderdomain()

=head1 DESCRIPTION

XXX

=head1 AUTHOR

Michael Parker <[EMAIL PROTECTED]>

=head1 COPYRIGHT

Copyright (c) 2005 Michael Parker. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0
 
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

=cut

package Mail::SpamAssassin::Plugin::DomainKeys;

use Mail::SpamAssassin::Plugin;
use strict;
use warnings;
use bytes;

use Mail::DomainKeys::Message;
use Mail::DomainKeys::Policy;

use vars qw(@ISA);
@ISA = qw(Mail::SpamAssassin::Plugin);

# constructor: register the eval rule
sub new {
  my $class = shift;
  my $mailsaobject = shift;

  $class = ref($class) || $class;
  my $self = $class->SUPER::new($mailsaobject);
  bless ($self, $class);

  $self->register_eval_rule ("check_domainkeys_senderdomain");
  $self->register_eval_rule ("check_domainkeys_verified");
  $self->register_eval_rule ("check_domainkeys_notsignedok");
  $self->register_eval_rule ("check_domainkeys_testing");
  $self->register_eval_rule ("check_domainkeys_signall");

  return $self;
}


sub check_domainkeys_senderdomain {
  my ($self, $permsgstatus) = @_;

  $self->_check_domainkeys($permsgstatus) unless 
$permsgstatus->{domainkeys_checked};
  
  return $permsgstatus->{domainkeys_found};
}

sub check_domainkeys_verified {
  my ($self, $permsgstatus) = @_;

  $self->_check_domainkeys($permsgstatus) unless 
$permsgstatus->{domainkeys_checked};
  
  return $permsgstatus->{domainkeys_verified};
}

sub check_domainkeys_notsignedok {
  my ($self, $permsgstatus) = @_;

  $self->_check_domainkeys($permsgstatus) unless 
$permsgstatus->{domainkeys_checked};
  
  return $permsgstatus->{domainkeys_notsignedok};
}

sub check_domainkeys_testing {
  my ($self, $permsgstatus) = @_;

  $self->_check_domainkeys($permsgstatus) unless 
$permsgstatus->{domainkeys_checked};
  
  return $permsgstatus->{domainkeys_testing};
}

sub check_domainkeys_signall {
  my ($self, $permsgstatus) = @_;

  $self->_check_domainkeys($permsgstatus) unless 
$permsgstatus->{domainkeys_checked};
  
  return $permsgstatus->{domainkeys_signall};
}



sub _check_domainkeys {
  my ($self, $permsgstatus) = @_;

  my $header = $permsgstatus->{msg}->get_pristine_header();
  my $body = $permsgstatus->{msg}->get_body();

  my $message = Mail::DomainKeys::Message->load(HeadString => $header,
                                                 BodyReference => $body);

  return unless $message;

  $permsgstatus->{domainkeys_checked} = 1;

  # does a sender domain header exist?
  return unless $message->senderdomain();

  $permsgstatus->{domainkeys_found} = 1;

  # verified
  if ($message->signed() && $message->verify()) {
    $permsgstatus->{domainkeys_verified} = 1;
  }

  my $policy = Mail::DomainKeys::Policy->fetch(Policy => 'dns',
                                               Domain => 
$message->senderdomain());

  return unless $policy;

  # not signed and domain doesn't sign all
  if ($policy->signsome() && !$message->signed()) {
    $permsgstatus->{domainkeys_notsignedok} = 1;
  }

  # domain or key testing
  if ($message->testing() || $policy->testing()) {
    $permsgstatus->{domainkeys_testing} = 1;
  }

  # does policy require all mail to be signed
  if ($policy->signall()) {
    $permsgstatus->{domainkeys_signall} = 1;
  }

  return;
}

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