#!/usr/bin/perl

use Sendmail::Milter;
use Net::DNS;
use Socket;

my %my_milter_callbacks = (
'connect' => \&connect_callback,
'helo' => \&helo_callback,
'envfrom' => \&envfrom_callback,
);

my $res = Net::DNS::Resolver->new;

$| = 1;

sub connect_callback
{
	my $ctx = shift;	# Some people think of this as $self
	my $hostname = shift;
	my $sockaddr_in = shift;

    if ($hostname eq localhost) {
        return SMFIS_ACCEPT;
    }

	#return SMFIS_CONTINUE;

	print "my_connect: hostname($hostname)";

	if (defined $sockaddr_in)
	{
		my ($port, $iaddr) = sockaddr_in($sockaddr_in);
		print " port($port)";
		print " iaddr(" . inet_ntoa($iaddr) . ")";
	}
print "\n";

	return SMFIS_CONTINUE;
}

sub helo_callback
{
    my $ctx = shift;
    my @args = @_;

    printf "helo: '%s'\n",$args[0];
	return SMFIS_CONTINUE;
}


sub envfrom_callback
{
    my $ctx = shift;
    my @args = @_;

    #printf "envfrom: %s\n",$args[0];

# if addr is of the form <>... strip 'em.
# then look for the domain part

    return SMFIS_CONTINUE if $args[0] !~ /\@([^>]*)(\>|$)/;

    $domain = $1;

    my @mx = mx($domain);

    if (@mx) {
	foreach $mx (@mx) {
            my ($name,$aliases,$type,$len,@addrs) = gethostbyname($mx->exchange);
	    foreach $ip (@addrs) {
               $ipstr = join('.',unpack("C4",$ip));
		if ($ipstr eq "127.0.0.1") {
	            printf("%s MX %s %s %s\n",$domain,$mx->preference, $mx->exchange, $ipstr);
		    $ctx->setreply("551","5.7.1","invalid loopback MX detected in return address");
		    return SMFIS_REJECT;
		}

	    }
	}
    }
    else {
            my ($name,$aliases,$type,$len,@addrs) = gethostbyname($domain);
	    foreach $ip (@addrs) {
               $ipstr = join('.',unpack("C4",$ip));
		if ($ipstr eq "127.0.0.1") {
	            printf("%s A %s\n",$domain,$ipstr);
		    $ctx->setreply("551","5.7.1","invalid loopback A detected in return address");
		    return SMFIS_REJECT;
		}

	    }
    }

    return SMFIS_CONTINUE;
}

BEGIN:
{
# Get myfilter's connection information
# from /etc/mail/sendmail.cf

    Sendmail::Milter::auto_setconn("mxmilter");
    Sendmail::Milter::register("mxmilter",
            \%my_milter_callbacks, SMFI_CURR_ACTS);
    Sendmail::Milter::main();

# Never reaches here, callbacks are called from Milter.

}