NAME

Net::Server::Mail::ESMTP::XFORWARD - A module to add support to the XFORWARD command in Net::Server::Mail::ESMTP

SYNOPSIS

    use Net::Server::Mail::ESMTP;
    
    my @local_domains = qw(example.com example.org);
    my $server = IO::Socket::INET->new( Listen => 1, LocalPort => 25 );
    
    my $conn;
    while($conn = $server->accept)
    {
        my $esmtp = Net::Server::Mail::ESMTP->new( socket => $conn );
        
        # activate XFORWARD extension if remote client is localhost
        $esmtp->register('Net::Server::Mail::ESMTP::XFORWARD')
           if($server->get_property('peeraddr') =~ /^127/);
        # adding some handlers
        $esmtp->set_callback(RCPT => \&validate_recipient);
        # adding XFORWARD handler
        $esmtp->set_callback(XFORWARD => \&xforward);
        $esmtp->process();
        $conn->close();
    }
    
    sub xforward {
        my $self = shift;
        # Reject non IPV4 addresses
        return 0 unless( $self->get_forwarded_address =~ /^\d+\.\d+\.\d+\.\d+$/ );
        1;
    }
    
    sub validate_recipient
    {
        my($session, $recipient) = @_;
        my $domain;
        if($recipient =~ /\@(.*)>\s*$/)
        {
            $domain = $1;
        }
        if(not defined $domain)
        {
            return(0, 513, 'Syntax error.');
        }
        elsif(not(grep $domain eq $_, @local_domains) && $session->get_forwarded_addr != "10.1.1.1")
        {
            return(0, 554, "$recipient: Recipient address rejected: Relay access denied");
        }
    
        return(1);
    }

DESCRIPTION

When using a Net::Server::Mail::ESMTP script inside a MTA and not in front of Internet, values like client IP address are not accessible to the script and when the script returns mail to another instance of smtpd daemon, it logs "localhost" as incoming address. To solve this problem, some administrators use the XFORWARD command. This module gives the ability to read and store XFORWARD information.

METHODS

These methods return the values set by the upstream MTA without modifying them so they can be set to undef or "[UNVAILABLE]". See Postfix documentation for more.

get_forwarded_values : returns a hash reference containing all values forwarded (keys in lower case).
get_forwarded_name : returns the up-stream hostname. The hostname may be a non-DNS hostname.
get_forwarded_address : returns the up-stream network address. Address information is not enclosed with []. The address may be a non-IP address.
get_forwarded_source : returns LOCAL or REMOTE.
get_forwarded_helo : returns the hostname that the up-stream host announced itself. It may be a non-DNS hostname.
get_forwarded_proto : returns the mail protocol for receiving mail from the up-stream host. This may be an SMTP or non-SMTP protocol name of up to 64 characters.

AUTHOR

Xavier Guimard, <x.guimard@free.fr>

COPYRIGHT AND LICENSE

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.6.4 or, at your option, any later version of Perl 5 you may have available.

2019-08-17