Installing OpenVPN on Ubuntu 17.10

#1: Installing OpenVPN

We can start with installing using terminal, install open vpsn and easy-rsa

$ sudo apt-get update
$ sudo apt-get install openvpn easy-rsa

# 2: Setting Certificate
We need to setup certificate on our server, also manage this certificates

$ make-cadir ~/openvpn-ca
$ cd ~/openvpn-ca

Edit vars using nano editor other editior

$ nano vars

change key name, following below

export KEY_COUNTRY="US"
export KEY_PROVINCE="CA"
export KEY_CITY="Tustin"
export KEY_ORG="SSD Nodes"
export KEY_EMAIL="[email protected]"
export KEY_OU="Marketing"

# X509 Subject Field
export KEY_NAME="vpnserver"

you can get this result, No other errors you have

$ source vars
NOTE: If you run ./clean-all, I will be doing a rm -rf on /home/user/openvpn-ca/keys

Then clean and build new environment

$ ./clean-all
$ ./build-ca

 

Next up, you need to create the server certificate and key pair. When you run the below command you can change [server] to the name of your choice. Later, you’ll need to reference this name. For the sake of this tutorial, we’re choosing with vpnserver.

Note: When prompted, do not enter a password.

Finally, you’ll be asked two questions about signing the certificate and committing it. Hit y and then Enter for both, and you’ll be done.

$ ./build-key-server [server]

Next, you need to build Diffie-Hellman keys.

$ ./build-dh

Finally, you need to generate an HMAC signature to strengthen the certificate.

$ openvpn --genkey --secret keys/ta.key

Step 4: Create the client public/private keys

This process will create a single client key and certificate. If you have multiple users, you’ll want to create multiple pairs.

When running the below command, hit Enter to confirm the variables we set and then leave the password field blank.

$ source vars
$ ./build-key client1

If you want to create password-protected credentials, use build-key-pass instead:

$ source vars
$ ./build-key-pass client1

Step 5: Configure the OpenVPN server

First, you need to copy the keyfiles we created in ~/openvpn-ca into the /etc/openvpn directory. Note: change the vpnserver.crt and vpnserver.key files according to the [server] name you chose earlier.

$ cd ~/openvpn-ca/keys
$ sudo cp ca.crt ca.key vpnserver.crt vpnserver.key ta.key dh2048.pem /etc/openvpn

Now, extract a sample OpenVPN configuration to the default location.

$ gunzip -c /usr/share/doc/openvpn/examples/sample-config-files/server.conf.gz | sudo tee /etc/openvpn/server.conf

We now need to make some edits to the configuration file.

$ sudo nano /etc/openvpn/server.conf

First, let’s ensure that OpenVPN is looking for the right .crt and .key files.

Before:

ca ca.crt
cert server.crt
key server.key  # This file should be kept secret

After (change according to the [server] name you chose earlier):

ca ca.crt
cert vpnserver.crt
key vpnserver.key  # This file should be kept secret

Next, enforce identical HMAC between clients and the server.

Before:

;tls-auth ta.key 0 # This file is secret

After:

tls-auth ta.key 0 # This file is secret
key-direction 0

Because we are going to use this VPN to route our traffic to the internet, we need to uncomment a few lines to help us establish DNS. You should also remove bypass-dhcp from the first line in question.

If you would prefer to use a DNS other than opendns, you should change the two lines that begin with push "dhcp-option.

Before:

# 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"

After:

# 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"

# 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"

Then we need to select the ciphers to use. Uncomment the AES cipher and change it to 256, and then add auth SHA512 at the bottom of the block.

Before:

# 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

After:

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC        # Blowfish (default)
cipher AES-256-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES
auth SHA512

Finally, let’s have OpenVPN use a non-privileged user account instead of root, which isn’t particularly secure.

user openvpn
group nogroup

You can now save and close this file in order to create that user:

$ sudo adduser --system --shell /usr/sbin/nologin --no-create-home openvpn

The OpenVPN server should now be set up!

Step 6: Start up the OpenVPN server

Before we configure our clients, let’s make sure the OpenVPN server is running as we hope it will.

Make sure to turn on TUN/TAP in the SSD Nodes dashboard.

$ sudo systemctl enable openvpn@server
$ sudo systemctl start openvpn@server

You can double-check that OpenVPN is running with the systemctl status command:

$ sudo systemctl status openvpn@server

If you’re having problems getting OpenVPN to start, commenting out the LimitNPROC in /lib/systemd/system/[email protected], as discovered in this Ask Ubuntu thread may be useful. You’ll then need to run sudo systemctl daemon-reload and then sudo systemctl start openvpn@server.

You will also need to set up iptables to properly direct traffic. First, look for the default interface.

$ sudo ip route | grep default
default dev venet0  scope link

The venet0 field is what we’re looking for. And then we set up iptables. In order to ensure this rule is persistent between reboots, isntall the iptables-persistent package, which will prompt you to save existing rules. Choose Yes and your rules will be persisted movign forward.

$ sudo iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j MASQUERADE
$ sudo apt-get install iptables-persistent

Step 7: Configure clients

Lastly, you need to create client configurations. You can store these in any folder you’d like—they don’t need to be kept secret—as long as it isn’t the /etc/openvpn folder. We’ll create a directory in home for this purpose.

$ cd ~
$ mkdir openvpn-clients
cd openvpn-clients

Now, copy the sample client configuration into this new directory, and then open it in nano for editing.

$ cp /usr/share/doc/openvpn/examples/sample-config-files/client.conf ~/openvpn-clients/base.conf
$ nano base.conf

Look for the following block of lines. You’ll need to change the my-server-1 to the public IP address of this VPS. You can find this information in the SSD Nodes dashboard, or by typing in the ifconfig command and looking for the inet field that does not look like 127.0.0.x.

# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote my-server-1 1194
;remote my-server-2 1194

Next, uncomment the following two lines by removing the semicolon.

Before:

# Downgrade privileges after initialization (non-Windows only)
;user nobody
;group nogroup

After:

# Downgrade privileges after initialization (non-Windows only)
user nobody
group nogroup

Because we’ll be adding keys and certificates directly into the .ovpn file, let’s comment out the following lines by adding semicolons to the beginning.

Before:

# 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

After:

# 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

Finally, jump to the bottom of the file and add the following lines. The first two mirror the cipher/auth options we added to the server.conf file earlier, and the third establishes that this files will be used to connect to the server, not the other way around.

We’re also adding three commented-out files that should be uncommented for Linux-based systems that use update-resolv-conf.

# Added lines via SSD Nodes tutorial
cipher AES-256-CBC
auth SHA512
key-direction 1

# script-security 2
# up /etc/openvpn/update-resolv-conf
# down /etc/openvpn/update-resolv-conf

Finally, you need to embed the keys and certificates into an .ovpn file using base.conf as a framework. Copy this entire command and execute it to embed the keys and create a final client1.ovpn file.

$ cat base.conf 
  <(echo -e '<ca>') ~/openvpn-ca/keys/ca.crt <(echo -e '</ca>') 
  <(echo -e '<cert>') ~/openvpn-ca/keys/client1.crt <(echo -e '</cert>n') 
  <(echo -e '<key>') ~/openvpn-ca/keys/client1.key <(echo -e '</key>n') 
  <(echo -e '<tls-auth>') ~/openvpn-ca/keys/ta.key <(echo -e '</tls-auth>') 
  >> client1.ovpn

This tutorial won’t cover client configurations in detail, but we’ll share one easy way to transfer the .ovpn file to your Linux or OS X client. This command will ssh into your VPS, and then use cat to write a new client1.ovpn file on your local machine.

$ ssh USER@SERVER-IP "cat ~/openvpn-clients/client1.ovpn" > client1.ovpn

Once you configure your client, you should be able to connect to the VPN and access the wider internet through it. Congratulations!


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