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Make your own VPN server

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Christophe NUNES edited this page Apr 5, 2017 · 28 revisions

Introduction

In this tutorial I will show you how to make your own VPN (Virtual Private Network) server. This VPN will not allow you to download illegally without sending your IP. It's totally the opposite, cause it will use your home IP address. The principle of this type of VPN which I'm introducing you, is to use your own home IP address, instead of using public like in a Wi-fi hotspot or any other public network. Or, if you are travelling in foreign countries, it allows you to get an IP address from your country, and allows watching videos and webpages which are censored by authorities. It also permits you to access to your other devices in local, without opening any ports on it to internet. It is usefull.

The principle of OpenVPN, is to make a tunnel between your computer, to your server, and go to internet through the server and your router. At the end of this tutorial, you will test and check your IP address will change to your home IP address, by testing with your phone as modem.

To encapsulate our data, I am using a Diffie-Hellman encryption, and to authenticate server to client, and client to server, a Master CA that will sign both client and server private key. We will generate these keys and certificate on the server, and you must transfer the client key from the server to client with USB key by preference, to make sure your data was not sniffed by Man-in-the-Middle attack.

If you want more information about Diffie-Hellman encryption take a look here :

1rst step

To make this tutorial, I used a server with Debian LITE Jessie distribution, and a client with Ubuntu:16.04 LTS. Make this first step on both client and server.

Make sure your repositories are updated and upgraded :

sudo apt-get update
sudo apt-get upgrade

and also your distribution :

sudo apt-get dist-upgrade

Installing and configuring OpenVPN

On the server, we need to install some components to generate Master CA and keys for both server and client :

sudo apt-get install openvpn easy-rsa openssl

Create an easy-rsa directory in OpenVPN, and copy all easy-rsa original scripts in :

sudo mkdir /etc/openvpn/easy-rsa
sudo mkdir /etc/openvpn/easy-rsa/keys
sudo cp /usr/share/easy-rsa/* /etc/openvpn/easy-rsa

We must change the directory and sub-directory rights of easy-rsa to your actual user (a sudoer so...):

sudo chown -R $USER /etc/openvpn/easy-rsa

Edit vars file from easy-rsa. I use vim as text editor, so you can also use nano :

sudo vim /etc/openvpn/easy-rsa/vars

Make changes you need to generate the certificate and keys, in my case, I live in Paris, so I made changes like :

# easy-rsa parameter settings

# NOTE: If you installed from an RPM,
# don't edit this file in place in
# /usr/share/openvpn/easy-rsa --
# instead, you should copy the whole
# easy-rsa directory to another location
# (such as /etc/openvpn) so that your
# edits will not be wiped out by a future
# OpenVPN package upgrade.

# This variable should point to
# the top level of the easy-rsa
# tree.
export EASY_RSA="`pwd`"

#
# This variable should point to
# the requested executables
#
export OPENSSL="openssl"
export PKCS11TOOL="pkcs11-tool"
export GREP="grep"


# This variable should point to
# the openssl.cnf file included
# with easy-rsa.
export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`

# Edit this variable to point to
# your soon-to-be-created key
# directory.
#
# WARNING: clean-all will do
# a rm -rf on this directory
# so make sure you define
# it correctly!
export KEY_DIR="$EASY_RSA/keys"

# Issue rm -rf warning
echo NOTE: If you run ./clean-all, I will be doing a rm -rf on $KEY_DIR

# PKCS11 fixes
export PKCS11_MODULE_PATH="dummy"
export PKCS11_PIN="dummy"

# Increase this to 2048 if you
# are paranoid.  This will slow
# down TLS negotiation performance
# as well as the one-time DH parms
# generation process.
export KEY_SIZE=2048

# In how many days should the root CA key expire?
export CA_EXPIRE=3650

# In how many days should certificates expire?
export KEY_EXPIRE=3650

# These are the default values for fields
# which will be placed in the certificate.
# Don't leave any of these fields blank.
export KEY_COUNTRY="FR"
export KEY_PROVINCE="IDF"
export KEY_CITY="PARIS"
export KEY_ORG="NONE"
export KEY_EMAIL="[email protected]"
export KEY_OU="MyOrganizationalUnit"

# X509 Subject Field
export KEY_NAME="EasyRSA"

# PKCS11 Smart Card
# export PKCS11_MODULE_PATH="/usr/lib/changeme.so"
# export PKCS11_PIN=1234

# If you'd like to sign all keys with the same Common Name, uncomment the KEY_CN export below
# You will also need to make sure your OpenVPN server config has the duplicate-cn option set
# export KEY_CN="CommonName"

Don't change any path, all is already configured by creating previous directories. You can decrease KEY_SIZE value for Diffie-Hellman (DH) but I advise you not to. More security is preferable. You do not want that someone connects on your VPN and use your home IP address no?

Generate Master CA, server and clients keys :

Change directory into easy-rsa :

cd /etc/openvpn/easy-rsa

Now, launch the vars script, if you got some difficulties by generating next scripts, make sure you got $USER rights in easy-rsa and sub-directory :

. ./vars

Yes, the command is well : Point --> Space --> Point --> Slash --> vars

./clean-all
./build-ca

Ok your Master CA is now built. OpenVPN works on PKI (Public Key Infrastructure). It means that server and all clients owns a certificate (or Public Key) and a Private Key. A Master CA and a Private Key are used to sign server and clients certificates. The Master CA permits a bidirectional authentication : each server and client mutually authenticate, verifying if the certificate that each propose to the other were signed by Master CA. This medium is a good defense against Man-in-the-Middle attack.

This script made certificate ca.crt and key ca.key lets take a look inside our keys directory :

ls -l /etc/openvpn/easy-rsa/keys

Ok, now we will create our server and clients keys. In my case, I only use one client. It is my personal VPN. If you need more client, just repeat the client key generating commands for each client you need. Just don't forget to name your client keys (client1, client2,client3 and so on...)

On the following commands, you can choose any name for your server. But I advise you to use your server hostname for more clarity. Each time this name is required, you must give it.

Server keys :

./build-key-server your_server_name

  • As we ever edited the vars file, normally all information between [ ] must be correct, so just press ENTER. When common-name is required just type your_server_name you previously typed on last command line.

  • sign the certificate? : yes

  • 1 out of 1 certificate requests certificated, commit : yes

This script made your_server_name.crt and your_server_name.key in our keys directory :

ls -l /etc/openvpn/easy-rsa/keys

Now we will generate clients keys. As I told you previously, I only use one client in this conf. Repeat the next command line for each client you need. I also put a passphrase in my client key, I advise you to do the same for more security.

Generate client key with passphrase :

./build-key-pass client1

With no passphrase :

./build-key client1

You can change client1 by other name. Just don't forget the names you inquired for each client key generated.

  • common-name : inquire the name you previously typed for key generating

  • sign the certificate? : yes

  • 1 out of 1 certificate requests certificated, commit : yes

Generate Diffie-Hellman encryption protocol :

Diffie-Hellman parameters are generated using :

./build-dh

This command line can take several minutes to generate a 2048 bits encryption file. It depends your computer's configuration.

It results a dh2048.pem file, let check :

ls -l /etc/openvpn/easy-rsa/keys

OK, all our VPN security is ready, now we can configure our server and OpenVPN client.

OpenVPN Server configuration

In this part, we will configure the server, giving the pathes to Master CA and both server and client keys. Also, we will configure max client number. In my case, I wish to be the only VPN user. I also created a SSH connection with RSA security to got a power on my server if for example, someone cracked my VPN, I can connect on my server and poweroff immediatly if necessary. We need to configure the VPN IP address, and DNS (VPN rules like a DHCP for clients) and allow clients to connect on internet, getting home IP address. We must configure IP forwarding and POSTROUTING at end of this tutorial.

Now, we need to copy config files into our OpenVPN directory. For the server conf :

sudo cp /usr/share/doc/openvpn/examples/sample-config-files/server.conf.gz /etc/openvpn/

Client conf :

cp /usr/share/doc/openvpn/examples/sample-config-files/client.conf /etc/openvpn/

Change directory into :

cd /etc/openvpn

Extract the server.conf file :

sudo gunzip server.conf.gz

If it does not work, make sure you got gunzip package :

sudo apt-get install gunzip

Now, edit server.conf file :

sudo vim server.conf

You can use my server.conf from this repository just right here</a href> just changing pathes for certificates and file name (server_name.key) and other, as you wish.

My server conf :

#################################################
# 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 your_local_IP_address

# 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 /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/server.crt
key /etc/openvpn/easy-rsa/keys/server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh1024.pem 1024
# Substitute 2048 for 1024 if you are using
# 2048 bit keys. 
dh /etc/openvpn/easy-rsa/keys/dh2048.pem

# 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 192.168.10.1 255.255.255.0"
;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.
;cipher BF-CBC        # Blowfish (default)
cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES

# Enable compression on the VPN link.
# 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 1

# 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 nogroup

# 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 5

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

You can modify certificate and keys files paths as you wish. Don't forget to move these files from their actual directory so.

Explanation

In fact, you just need to read the conf file, everything is clearly explained. But I will explain some parts, and choices I made in this configuration :

  • proto tcp : the protocol I use to communicate is TCP

  • dev tun : tun, is a routed VPN configuration. we use it to can connect into our VPN from outside our local network. In the case of a Local Network VPN architecture, you can use tap for a bridged VPN.

  • ca/cert/key : are the paths to reach Master CA, Certificate and Key files in the server.

  • dh : the path to reach the Diffie-Hellman parameters file.

  • 10.8.0.0 255.255.255.0 : the VPN subnetID. Your VPN server will start with 10.8.0.1 IP address. Other connected devices will get other IP addresses from this subnetID like a DHCP role (example : 10.8.0.5 and so on...)

  • push "redirect-gateway def1 bypass-dhcp" : to allow our client to reach internet through the server.

  • push "dhcp-option DNS 208.67.222.222" : as I told you previously, VPN work like a DHCP, so it attributes an IP address and DNS address too. Here, these addresses are Cisco's DNS.

  • cipher AES-128-CBC # AES : a simple 128 bits cryptographic cipher.

  • max client : the max number of client you want to use your VPN, in my case, just me, so one.

  • status openvpn-status.log : status log file can be reached in /etc/openvpn (others log files too).

  • verb 5 : level 5 verbosity can allow you to fix bugs, or connection problem easily, it will give you a lot of information about VPN status.

OK, our server configuration is now finished. If you want to enable OpenVPN at start :

sudo systemctl enable openvpn

To disable :

sudo systemctl disable openvpn

Now restart openVPN service :

sudo service openvpn restart

Let see if our VPN works :

ifconfig

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet addr:10.8.0.1  P-t-P:10.8.0.2  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:86954 errors:0 dropped:0 overruns:0 frame:0
          TX packets:82883 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:20088544 (19.1 MiB)  TX bytes:8915053 (8.5 MiB)

Wonderfull, it works!

OpenVPN Client configuration

----------TO BE CONTINUED----------

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