qpsmtpd/plugins/require_resolvable_fromhost

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use Net::DNS qw(mx);
sub register {
my ($self, $qp) = @_;
$self->register_hook("mail", "mail_handler");
}
sub mail_handler {
my ($self, $transaction, $sender) = @_;
$sender->format ne "<>"
and $self->qp->config("require_resolvable_fromhost")
and !check_dns($sender->host)
and return (DENYSOFT,
($sender->host
? "Could not resolve ". $sender->host
: "FQDN required in the envelope sender"));
return DECLINED;
}
sub check_dns {
my $host = shift;
# for stuff where we can't even parse a hostname out of the address
return 0 unless $host;
return 1 if $host =~ m/^\[(\d{1,3}\.){3}\d{1,3}\]$/;
my $res = new Net::DNS::Resolver;
return 1 if mx($res, $host);
my $query = $res->search($host);
if ($query) {
foreach my $rr ($query->answer) {
return 1 if $rr->type eq "A" or $rr->type eq "MX";
}
}
else {
warn "$$ query for $host failed: ", $res->errorstring, "\n"
unless $res->errorstring eq "NXDOMAIN";
}
return 0;
}