#!/usr/bin/perl -w

=head1 NAME

check_bogus_bounce - Check that a bounce message isn't bogus

=head1 DESCRIPTION

This plugin is designed to reject bogus bounce messages.

In our case a bogus bounce message is defined as a bounce message
which has more than a single recipient.

=head1 CONFIGURATION

Only a single argument is recognized and is assumed to be the default
action.  Valid settings are:

=over 8

=item log

Merely log the receipt of the bogus bounce (the default behaviour).

=item deny

Deny with a hard error code.

=item denysoft

Deny with a soft error code.

=back

=cut

=head1 AUTHOR

Steve Kemp
--
http://steve.org.uk/Software/qpsmtpd/

=cut



=begin doc

Look for our single expected argument and configure "action" appropriately.

=end doc

=cut

sub register
{
    my ( $self, $qp, $arg, @nop ) = (@_);

    #
    #  Default behaviour is to merely log.
    #
    $self->{ _action } = "log";

    #
    #  Unless one was specified
    #
    if ($arg)
    {
        if ( $arg =~ /^(log|deny|denysoft)$/i )
        {
            $self->{ _action } = $arg;
        }
        else
        {
            die "Invalid argument '$arg' - use one of : log, deny, denysoft";
        }
    }
}


=begin doc

Handle the detection of bounces here.

If we find a match then we'll react with our expected action.

=end doc

=cut

sub hook_data_post
{
    my ( $self, $transaction ) = (@_);

    #
    # Find the sender, and return unless it wasn't a bounce.
    #
    my $sender = $transaction->sender->address || undef;
    return DECLINED unless ( $sender =~ /^<>$/ );

    #
    #  Get the recipients.
    #
    my @to = $transaction->recipients || ();
    return DECLINED unless ( scalar @to > 1 );


    #
    #  OK at this point we know:
    #
    #   1.  It is a bounce, via the null-envelope.
    #   2.  It is a bogus bounce, because there are more than one recipients.
    #
    if ( $self->{ _action } =~ /^log$/i )
    {
        $self->log( LOGWARN,
              $self->plugin_name() . " bogus bounce for :" . join( ",", @to ) );
    }
    elsif ( $self->{ _action } =~ /^deny$/i )
    {
        return ( DENY,
               $self->plugin_name() . " determined this to be a bogus bounce" );
    }
    elsif ( $self->{ _action } =~ /^denysoft$/i )
    {
        return ( DENYSOFT,
               $self->plugin_name() . " determined this to be a bogus bounce" );
    }
    else
    {
        $self->log( LOGWARN,
                  $self->plugin_name() . " failed to determine action.  bug?" );
    }

    #
    #  All done; allow this to proceed
    #
    return DECLINED;
}