port-forwarding

forward.pl

use warnings;
use strict;

use IO::Socket::INET;
use IO::Select;

my @allowed_ips = ('all', '10.10.10.5');
my $ioset = IO::Select->new;
my %socket_map;

my $debug = 1;

sub new_conn {
    my ($host, $port) = @_;
    return IO::Socket::INET->new(
        PeerAddr => $host,
        PeerPort => $port
    ) || die "Unable to connect to $host:$port: $!";
}

sub new_server {
    my ($host, $port) = @_;
    my $server = IO::Socket::INET->new(
        LocalAddr => $host,
        LocalPort => $port,
        ReuseAddr => 1,
        Listen    => 100
    ) || die "Unable to listen on $host:$port: $!";
}

sub new_connection {
    my $server = shift;
    my $remote_host = shift;
    my $remote_port = shift;

    my $client = $server->accept;
    my $client_ip = client_ip($client);

    unless (client_allowed($client)) {
        print "Connection from $client_ip denied.\n" if $debug;
        $client->close;
        return;
    }
    print "Connection from $client_ip accepted.\n" if $debug;

    my $remote = new_conn($remote_host, $remote_port);
    $ioset->add($client);
    $ioset->add($remote);

    $socket_map{$client} = $remote;
    $socket_map{$remote} = $client;
}

sub close_connection {
    my $client = shift;
    my $client_ip = client_ip($client);
    my $remote = $socket_map{$client};

    $ioset->remove($client);
    $ioset->remove($remote);

    delete $socket_map{$client};
    delete $socket_map{$remote};

    $client->close;
    $remote->close;

    print "Connection from $client_ip closed.\n" if $debug;
}

sub client_ip {
    my $client = shift;
    return inet_ntoa($client->sockaddr);
}

sub client_allowed {
    my $client = shift;
    my $client_ip = client_ip($client);
    return grep { $_ eq $client_ip || $_ eq 'all' } @allowed_ips;
}

die "Usage: $0 <local port> <remote_host:remote_port>" unless @ARGV == 2;

my $local_port = shift;
my ($remote_host, $remote_port) = split ':', shift();


print "Starting a server on 0.0.0.0:$local_port\n";
my $server = new_server('0.0.0.0', $local_port);
$ioset->add($server);

while (1) {
    for my $socket ($ioset->can_read) {
        if ($socket == $server) {
            new_connection($server, $remote_host, $remote_port);
        }
        else {
            next unless exists $socket_map{$socket};
            my $remote = $socket_map{$socket};
            my $buffer;
            my $read = $socket->sysread($buffer, 4096);
            if ($read) {
                $remote->syswrite($buffer);
            }
            else {
                close_connection($socket);
            }
        }
    }
}

port-forwarding

#! /bin/sh
### BEGIN INIT INFO
# Provides:          port-forwarding
# Required-Start:    $local_fs $network $named $time $syslog
# Required-Stop:     $local_fs $network $named $time $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Description:       Simple TCP port forwarding in Debian
### END INIT INFO

#
#   To install this, run as root:
#   export SERVICE_NAME="port-forwarding"; curl "https://gist.githubusercontent.com/caHarkness/f30a064416292b9c686258f856ec5aaa/raw/port-forwarding" > /etc/init.d/$SERVICE_NAME; chmod +x /etc/init.d/$SERVICE_NAME; ln -s /etc/init.d/$SERVICE_NAME /etc/rc2.d/S99$SERVICE_NAME; nano /etc/init.d/$SERVICE_NAME; sleep 3; systemctl daemon-reload
#

WORKING_DIRECTORY="/opt/port-forwarding"

forward_port () {
    LISTEN_PORT="$1"
    DESTINATION="$2"
    PERL_SCRIPT=$(curl -k "https://gist.githubusercontent.com/caHarkness/f30a064416292b9c686258f856ec5aaa/raw/forward.pl")

    perl -e "$PERL_SCRIPT" "$LISTEN_PORT" "$DESTINATION" &

    PERL_PROCESS="$!"

    touch $WORKING_DIRECTORY/pids/$PERL_PROCESS
    echo $DESTINATION > $WORKING_DIRECTORY/ports/$LISTEN_PORT
}

start_forwarding () {
    mkdir $WORKING_DIRECTORY
    mkdir $WORKING_DIRECTORY/pids
    mkdir $WORKING_DIRECTORY/ports

    forward_port 54303 192.168.1.10:54303
}

list_forwarded_ports () {
    for i in "$WORKING_DIRECTORY/ports/"*
    do
        PORT=$(basename $i)
        DEST=$(< $i)
        echo "$PORT $DEST"
    done
}

stop_forwarding () {
    for i in "$WORKING_DIRECTORY/pids/"*
    do
        KPID=$(basename $i)
        kill $KPID
    done

    for i in "$WORKING_DIRECTORY/ports/"*
    do
        rm "$i"
    done
}

edit_service () {
    SERVICE_NAME=$(basename $0)
    nano /etc/init.d/$SERVICE_NAME
    sleep 3
    systemctl daemon-reload
}

uninstall_service () {
    SERVICE_NAME=$(basename $0)
    rm /etc/init.d/$SERVICE_NAME
    rm /etc/rc2.d/S99$SERVICE_NAME
    echo "Service uninstalled."
}

PATH=/sbin:/usr/sbin:/bin:/usr/bin

. /lib/lsb/init-functions

case "$1" in
    start)
        start_forwarding
    ;;

    stop)
        stop_forwarding
    ;;

    restart)
        stop_forwarding
        sleep 3
        start_forwarding
        ;;

    list)
        list_forwarded_ports
        ;;

    edit)
        edit_service
        ;;

    uninstall)
        uninstall_service
        ;;

    *)
        echo "Usage: $0 {start|stop|restart|list|edit|uninstall}"
        ;;
esac