Securing your connection to myServer using OpenVPN technology

*** Document Still in Development ***

Introduction:

This document provides one example of how to implement the OpenVPN software to allow for a more "secure" network connection to the myServer installation from the Internet. The OpenVPN technology and software may be downloaded from the OpenVPN, Inc portal and must be used in accordance of their terms of use and license agreement. Please see https://openvpn.net/index.php/terms-of-use.html for more information.

Portions of this document are contents of the how to guide from the OpenVPN portal. We have identified several inconsistencies in the published documentation with the latest OpenVPN software in regards to the Windows operating system. We have made an attempt to correct as necessary. For further detailed information, please reference the OpenVPN Community information located at https://openvpn.net/index.php/open-source.html

Assumptions / Requirements:

  • All software is licensed according to Allonis, llc and OpenVPN, Inc license regulations.
  • Person(s) following this help guide are familiar and have sufficient skills to perform appropriate software installation and networking configuration.
  • Person(s) following this help guide will assume all risks associated with connecting computing equipment to the Internet and associating networks. Keep in mind that any time a computer is connected to a network or Internet, said devices are exposed to the potential vulnerabilities that exist in any computing platform. If you are not willing to accept this risk, then never connect a computing device to subsequent networks.
  • You will assume responsibility to confirm that resulting client connections will achieve a secured connection. If you are unfamilar with this process, then consult your network systems administrator or trusted network professional. 
  • OpenVPN software will be installed on myServer hardware. myServer hardware is behind firewall. Firewall is connected to active Internet connection. You will need to configure your Internet connection/firewall to pass UDP port 1194 traffic from the Internet to myServer where the OpenVPN server software will be executed. Should you decide to utilize an alternative port, then translate all references to 1194 to your desired port throughout this document. 
  • Base myServer installation is already installed and fully functioning.
  • OpenVPN server/client software - available from OpenVPN site (https://openvpn.net/index.php/download/community-downloads.html). Note:  MacOS, IOS and Android client software is available via respective platform APP store.
  • Your server will need to have a static internet IP or Domain Name to be accessible over the long term. One solution is to sign up for an account with DynDNS (or similar technology) and install the respective updater software on your server. When signing up you will determine the static Domain Name of your server. (For example, "myserver.dyndns.org") You will use this Domain Name in the client configuration files as part of the "remote" directive.
  • All clients connecting to the myServer via the OpenVPN technology must utilize the VPN tunnel for secure communications. There must not be an alternative "unsecured" connection to myServer. Individuals that previously "port forwarded" the client connection from their firewall to myServer must deinstall those firewall configuration rules. Failure to do so will result in potential continued unsecure connection, and associating risk exposure.

Client   ->   Internet   ->  Cable Modem/DSL Router/Firewall -> myServer
X========================== VPN Tunnel ================================X

Downloading and Installing OpenVPN software: 

  1. Install base installation of the OpenVPN software on myServer computer and on any desired client device. Please make sure that the option/check box for the easy-rsa scripts is checked.  Please note that the base installation will need to configured following the directions below.
  2. Install OpenVPN on each client. (This step can be skipped for now and done at any convenient time).  
  3. Configure your Internet connection/firewall to pass UDP port 1194 traffic from external devices on the Internet to myServer where the OpenVPN server software will be executed. Should you decide to utilize an alternative port, then translate all references to 1194 to your desired port throughout this document.

Configuring OpenVPN Software:

Certificates and Keys - Preparatory Steps

  1. Navigate to the C:\Program Files\OpenVPN\easy-rsa folder in the command prompt:
    1. Open Command Prompt (Press Windows Key + R )
    2. Type "cmd.exe" and press Enter:
      cmd.exe
    3. Navigate to the correct folder:
      cd "C:\Program Files\OpenVPN\easy-rsa"
    4. Important: If "keys" directory is not already created, then create the directory where the keys will be stored. Failure to do this will result in file creation errors when the keys are being generated in the next steps:

mkdir keys

  1. Initialize the OpenVPN configuration. NOTE: Only run init-config once, during installation.:
    init-config
  1. Open the vars.bat file in a text editor:
    notepad vars.bat
  2. Edit the following lines in vars.bat, replacing "US", "CA," etc. with your company's information:
    set KEY_COUNTRY=US
    set KEY_PROVINCE=CA
    set KEY_CITY=SanFrancisco
    set KEY_ORG=OpenVPN
    set KEY_EMAIL=This email address is being protected from spambots. You need JavaScript enabled to view it.
  3. Save the file and exit notepad.
  4. Run the following commands from the command prompt:
    vars

    clean-all

Certificates and Keys - Building Certificates and Keys

  1. The certificate authority (CA) certificate and key:
    build-ca
    • When prompted, enter your country, etc. These will have default values, which appear in brackets. For your "Common Name," a good choice is to pick a name to identify your company's Certificate Authority. For example, "OpenVPN-CA":
      Country Name (2 letter code) [US]:
      State or Province Name (full name) [CA]:
      Locality Name (eg, city) [SanFrancisco]:
      Organization Name (eg, company) [OpenVPN]:
      Organizational Unit Name (eg, section) []:
      Common Name (eg, your name or your server's hostname) []:OpenVPN-CA
      Email Address [This email address is being protected from spambots. You need JavaScript enabled to view it.]:
  2. The server certificate and key:
    build-key-server server
    • When prompted, enter the "Common Name" as "server"
    • When prompted to sign the certificate, enter "y"
    • When prompted to commit, enter "y"
  3. Client certificates and keys:
    1. For each client, choose a name to identify that computer, such as "mike-laptop" in this example. When prompted, enter the "Common Name" as the name you have chosen (e.g. "mike-laptop") 

build-key mike-laptop

  1. Repeat this step for each client computer that will connect to the VPN. 
  1. Generate Diffie Hellman parameters (This is necessary to set up the encryption). Depending on the speed of your computer, this may take several to many hours. Let it run, don't stop it or else the rest of this process will not work! You will get a screen similar to the following below:
    build-dh

C:\Program Files\OpenVPN\easy-rsa>build-dh
WARNING: can't open config file: /etc/ssl/openssl.cnf
Generating DH parameters, 4096 bit long safe prime, generator 2
This is going to take a long time (like a few hours or more)
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Configuration Files

Using Windows Explorer - Find the OpenVPN installation folder and sample configuration files: Start Menu -> All Programs -> OpenVPN -> OpenVPN Sample Configuration Files  

Edit - Server Config File 

  1. Open server.ovpn
  2. Find the following lines:
    ca ca.crt
    cert server.crt
    key server.key

    dh dh1024.pem (in the later versions this file may be named dh4096.pem)
  3. Edit them as follows: (make sure that you correctly reference the name the dh1024.pem or dh4096.pem file)
    ca "C:\\Program Files\\OpenVPN\\config\\ca.crt"
    cert "C:\\Program Files\\OpenVPN\\config\\server.crt"
    key "C:\\Program Files\\OpenVPN\\config\\server.key"

    dh "C:\\Program Files\\OpenVPN\\config\\dh1024.pem" (may need to be dh4096.pem)
  4. Save the file as C:\Program Files\OpenVPN\easy-rsa\server.ovpn 

Edit - Client Config Files 

This is similar to the server configuration. If the client.ovpn file does not exist then copy the contents of the server.ovpn file as a baseline.

  1. Open client.ovpn
  2. Find the following lines:
    ca ca.crt
    cert client.crt
    key client.key
  3. Edit them as follows:
    ca "C:\\Program Files\\OpenVPN\\config\\ca.crt"
    cert "C:\\Program Files\\OpenVPN\\config\\mike-laptop.crt"
    key "C:\\Program Files\\OpenVPN\\config\\mike-laptop.key"
    • Notice that the name of the client certificate and key files depends upon the Common Name of each client.
    • You can also include the ca, cert and key content in the client file. You have to copy the file content inside the tag <ca></ca>, <cert></cert> and <key></key>.
  4. Edit the following line, replacing "my-server-1" with your server's public Internet IP Address or Domain Name. If the following keyword (or directive in OpenVPN speak) is not in the file, then add it at the bottom of the file in a new line.
    remote my-server-1 1194
  5. Save the file as C:\Program Files\OpenVPN\easy-rsa\mike-laptop.ovpn (in this example. Each client will need a different, but similar, config file depending upon that client's Common Name.)   

Important: Copying the Server and Client Files to Their Appropriate Directories 

  1. Copy these files from C:\Program Files\OpenVPN\easy-rsa\ or C:\Program Files\OpenVPN\easy-rsa\keys\  to C:\Program Files\OpenVPN\config\ on the server:
    ca.crt
    dh1024.pem (in the later versions this file may be named dh4096.pem)
    server.crt
    server.key
    server.ovpn
  2. Copy these files from C:\Program Files\OpenVPN\easy-rsa\ on the server to C:\Program Files\OpenVPN\config\ on each client (mike-laptop, in this example):
    ca.crt
    mike-laptop.crt
    mike-laptop.key
    mike-laptop.ovpn
  3. Enclosed is a picture of the C:\Program Files\OpenVPN\Config folder which contains both the server and client configuration files. Note: client configuration files are not necessary on the server installation.

Executing OpenVPN Software: 

  1. Start the OpenVPN server from Start Menu -> All Programs -> OpenVPN -> OpenVPN GUI
  2. Double-click the icon which shows up in the system tray (lower left corner) to initiate the connection. The resulting dialog should close upon a successful start.

Further Considerations / Troubleshooting:

Firewall Configuration

If you have connection problems, make sure to set a rule on your server's firewall allowing incoming traffic on UDP port 1194.

Port Forwarding

If your server is behind a router, you will need to forward the port chosen for OpenVPN (in this example UDP 1194) to the server. Consult your router's documentation for details on this.

To set up port forwarding, you will likely need to set up the server with a static local IP address instead of the default dynamic (changing) IP. Instructions for Windows XP may be found here. Make sure to choose a static IP address that is not in the range your router might assign as a dynamic IP, but is within the router's subnet (usually 192.168.0.xxx , 10.0.0.xxx , or similar).

Static Internet IP

Your server will need to have a static internet IP or Domain Name to be accessible over the long term. One solution is to sign up for an account with DynDNS and install the DynDNS Updater on your server. When signing up you will determine the static Domain Name of your server. (For example, "myserver.dyndns.org") You will use this Domain Name in the client configuration files as part of the "remote" directive.

Running OpenVPN as a Service

You may configure the OpenVPN server to run as a Windows service. From the Windows Service Administration tool, find the OpenVPN Service and configure the startup type to "automatic".

Security Tips

  1. Transmit all needed files to the client computers using a secure means such as a USB drive (email is not always a secure means).
  2. Choose a port other than UDP 1194, and replace the port number wherever this guide mentions UDP port 1194. 

Sample Server.OVPN File:

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca "c:\\program files\\OpenVpn\\config\\ca.crt"
cert "c:\\program files\\OpenVPN\\Config\\server.crt"
key "c:\\program files\\OpenVPN\\Config\\server.key"  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
dh "c:\\program files\\openvpn\\config\\dh4096.pem"

# Network topology
# Should be subnet (addressing via IP)
# unless Windows clients v2.0.9 and lower have to
# be supported (then net30, i.e. a /30 per client)
# Defaults to net30 (not recommended)
;topology subnet

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
;push "dhcp-option DNS 208.67.222.222"
;push "dhcp-option DNS 208.67.220.220"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
;tls-auth ta.key 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
# Note that 2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-CBC

# Enable compression on the VPN link and push the
# option to the client (2.4+ only, for earlier
# versions see below)
;compress lz4-v2
;push "compress lz4-v2"

# For compression compatible with older clients use comp-lzo
# If you enable it here, you must also
# enable it in the client config file.
;comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

# Notify the client that when the server restarts so it
# can automatically reconnect. Do not use
;explicit-exit-notify 1

Sample client.OVPN File:

##############################################
# Sample client-side OpenVPN 2.0 config file #
# for connecting to multi-client server.     #
#                                            #
# This configuration can be used by multiple #
# clients, however each client should have   #
# its own cert and key files.                #
#                                            #
# On Windows, you might want to rename this  #
# file so it has a .ovpn extension           #
##############################################
# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
client
# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun
# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one.  On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
;dev-node MyTap
# Are we connecting to a TCP or
# UDP server?  Use the same setting as
# on the server.
;proto tcp
proto udp
# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote MyServerAddress 2592
;remote my-server-2 1194
# Choose a random host from the remote
# list for load-balancing.  Otherwise
# try hosts in the order specified.
;remote-random
# Keep trying indefinitely to resolve the
# host name of the OpenVPN server.  Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
resolv-retry infinite
# Most clients don't need to bind to
# a specific local port number.
nobind
# Downgrade privileges after initialization (non-Windows only)
;user nobody
;group nobody
# Try to preserve some state across restarts.
persist-key
persist-tun
# If you are connecting through an
# HTTP proxy to reach the actual OpenVPN
# server, put the proxy server/IP and
# port number here.  See the man page
# if your proxy server requires
# authentication.
;http-proxy-retry # retry on connection failures
;http-proxy [proxy server] [proxy port #]
# Wireless networks often produce a lot
# of duplicate packets.  Set this flag
# to silence duplicate packet warnings.
;mute-replay-warnings
# SSL/TLS parms.
# See the server config file for more
# description.  It's best to use
# a separate .crt/.key file pair
# for each client.  A single ca
# file can be used for all clients.
ca ca.crt
cert client.crt
key client.key
# Verify server certificate by checking that the
# certicate has the correct key usage set.
# This is an important precaution to protect against
# a potential attack discussed here:
http://openvpn.net/howto.html#mitm
#
# To use this feature, you will need to generate
# your server certificates with the keyUsage set to
#   digitalSignature, keyEncipherment
# and the extendedKeyUsage to
#   serverAuth
# EasyRSA can do this for you.
remote-cert-tls server
# If a tls-auth key is used on the server
# then every client must also have the key.
tls-auth ta.key 1
# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-CBC
# Enable compression on the VPN link.
# Don't enable this unless it is also
# enabled in the server config file.
#comp-lzo
# Set log file verbosity.
verb 3
# Silence repeating messages
;mute 20

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Another Sample implementation:

Objective: Network connect a RV / Boat / Secondary residence to your primary home's network.

Strategy: Add a myFirewall2 to both the RV and the home.  Configure the Home's PFSense firewall to host an OpenVPN Server, and configure the RV's PFSense firewall to host an OpenVPN Client.  Route all packets inbetween each other to create one large network when both are in connection to each other.  Allow both networks to work independently of each other when not in connection.

The myFirewall2 is an inexpensive yet highly capable firewall that is the key to success.  You can purchase it here.  Allonis can be retained to also custom configure the firewall to your requirements, like to implement this objective.