qpsmtpd/plugins/require_resolvable_fromhost

#!/usr/bin/perl
use Danga::DNS;

my %invalid = ();

sub init {
    my ($self, $qp) = @_;
    foreach my $i ($qp->config("invalid_resolvable_fromhost")) {
	$i =~ s/^\s*//;
	$i =~ s/\s*$//;
	if ($i =~ m#^((\d{1,3}\.){3}\d{1,3})/(\d\d?)#) {
	    $invalid{$1} = $3;
	}
    }
}

sub hook_mail {
    my ($self, $transaction, $sender) = @_;
    return DECLINED
    	if ($self->qp->connection->notes('whitelistclient'));
    
    $self->transaction->notes('resolvable', 1);
    return DECLINED if $sender->format eq "<>";
    return $self->check_dns($sender->host);
}

sub check_dns {
    my ($self, $host) = @_;
    
    # for stuff where we can't even parse a hostname out of the address
    return DECLINED unless $host;
    
    if( $host =~ m/^\[(\d{1,3}\.){3}\d{1,3}\]$/ ) {
        $self->transaction->notes('resolvable', 1);
        return DECLINED;
    }

    my $total_queries = 2;
    my $qp = $self->qp;
    $self->log(LOGDEBUG, "Checking $host for MX record in the background");
    Danga::DNS->new(
        callback => sub { dns_result($qp, @_) },
        finished => sub { $total_queries--; finished($qp, $total_queries) },
        host => $host,
        type => "MX",
        client => $qp->input_sock,
    );
    $self->log(LOGDEBUG, "Checking $host for A record in the background");
    Danga::DNS->new(
        callback => sub { dns_result($qp, @_) },
        finished => sub { $total_queries--; finished($qp, $total_queries) },
        host => $host,
        client => $qp->input_sock,
    );
    return CONTINUATION;
}

sub finished {
    my ($qp, $total_zones) = @_;
    $qp->finish_continuation unless $total_zones;
}

sub dns_result {
    my ($qp, $result, $query) = @_;
    
    if ($result =~ /^[A-Z]+$/) {
        # probably an error
        $qp->log(LOGDEBUG, "DNS error: $result looking up $query");
    } else {
        $qp->transaction->notes('resolvable', 1);
        $qp->log(LOGDEBUG, "DNS lookup $query returned: $result");
    }
}


sub hook_rcpt {
    my ($self, $transaction) = @_;
    
    if (!$transaction->notes('resolvable')) {
        my $sender = $transaction->sender;
        $self->log(LOGDEBUG, "Could not resolve " .$sender->host) if $sender->host;
        return (DENYSOFT, 
		      ($sender->host
    		   ? "Could not resolve ". $sender->host
           	   : "FQDN required in the envelope sender"));
    }
    
    return DECLINED;
}