How to install and configure OpenVPN on OpenSUSE Leap 42.1

VPN or Virtual Private Network is a secure private network over a public network like the internet. A VPN is a secure tunnel trough the internet which protects your data traffic and increases internet privacy and security. Access to the VPN is restricted by secure authentication methods.

OpenVPN is an open source software to build virtual private networks, it uses the OpenSSL library to encrypt the tunneled data and supports UDP or TCP transports. OpenVPN can use pre-shared keys, certificate based and username/password based authentication mechanisms.

In this tutorial, I will show you how to implement a virtual private network using OpenVPNvpn under the Linux operating system OpenSUSE Leap 42.1.

Prerequisites

  • OpenSUSE Leap 42.1 - 64bit
  • Root privileges
  • TUN/TAP enabled

Step 1 - Checking if TUN/TAP is enabled

If you want to create a VPN on your server, make sure TUN/TAP is installed and enabled. You can check that with the command below:

cat /dev/net/tun

The result should be:

cat: /dev/net/tun: File descriptor in bad state

Step 2 - Install OpenVPN

OpenVPN is available in the OpenSUSE repository. You can install it using the zypper command:

zypper in openvpn

Step 3 - Easy-RSA Setup

Next, download easy-rsa to generate a certificate file. The easy-rsa is a utility to manage certificates, you can create the root certificate authority with it and request and sign certificates.

Go to the OpenVPN directory and download easy-rsa with the wget command:

cd /etc/openvpn/
wget https://github.com/OpenVPN/easy-rsa/archive/release/2.x.zip

Extract the archive and move the easy-rsa directory:

unzip 2.x.zip
mv easy-rsa-release-2.x/easy-rsa/ /etc/openvpn/
rm -rf easy-rsa-release-2.x/

Configure the Key

Go to the easy-rsa directory and edit the vars file to configure the key and certificate:

cd easy-rsa/2.0/
vim vars

Line 53 - If you are really paranoid, you can increase the key size.

export KEY_SIZE=2048

Line 56 and 59 - In how many days the key and certificate will expire.

export CA_EXPIRE=3650
export KEY_EXPIRE=3650

Line 64 - 72 - Change the default value of the key and certificate information.

export KEY_COUNTRY="US"
export KEY_PROVINCE="California"
export KEY_CITY="SanFrancisco"
export KEY_ORG="Fort-Funston"
export KEY_EMAIL="[email protected]"
export KEY_OU="MyOrganizationalUnit"
export KEY_NAME="EasyRSA"

Save the file and exit.

Initialize the PKI

Next, initialize the PKI (Public Key Infrastructure):

source ./vars && ./clean-all && ./build-ca

We will leave the default value, just press "Enter".

Initialize the pki.

Generate Diffie Hellman Parameters

Run the command below:

./build-dh

You will see the output:

Generating DH parameters, 2048 bit long safe prime, generator 2
This is going to take a long time
..................................

Generate the Server Private Key

Generate the private key with the name "server":

./build-key-server server

Press enter and type "y" to confirm to generate the key.

Generate the server key.

Generate Key and Certificate for the Client

Generate the client key and certificate with name "client1":

./build-key client1

Press enter and type "y" to confirm the key generation.

Generate the client cert and key.

The key and certificate have been generated in the directory "keys". Now make a copy of the "keys" directory and put it in the "openvpn" directory.

cp -r keys/ /etc/openvpn/

Step 4 - Configure OpenVPN

In this step, we will configure OpenVPN to run on UDP protocol, using port 2034 for the client connection. Create the new configuration file server.conf in the OpenVPN directory.

cd /etc/openvpn/
vim server.conf

Paste the configuration below:

#change with your port
port 2034

#You can use udp or tcp
proto udp

# "dev tun" will create a routed IP tunnel.
dev tun

#Certificate Configuration

#ca certificate
ca /etc/openvpn/keys/ca.crt

#Server Certificate
cert /etc/openvpn/keys/server.crt

#Server Key and keep this is secret
key /etc/openvpn/keys/server.key

#See the size a dh key in /etc/openvpn/keys/
dh /etc/openvpn/keys/dh2048.pem

#Internal IP will get when already connect
server 10.10.2.0 255.255.255.0

#this line will redirect all traffic through our OpenVPN
push "redirect-gateway def1"

#Provide DNS servers to the client, you can use goolge DNS
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"

#Enable multiple client to connect with same key
duplicate-cn

keepalive 20 60
comp-lzo
persist-key
persist-tun
daemon

#openvpn status log
status /var/log/openvpn/openvpn-status.log

#enable log
log-append /var/log/openvpn/openvpn.log

#Log Level
verb 3

Save the file and exit the editor.

Next, create a new directory and file for the openvpn log:

mkdir -p /var/log/openvpn/
touch /var/log/openvpn/{openvpn,openvpn-status}.log

Step 5 - Configure SuSEfirewall2

SuSEfirewall2 is a script for generating iptables rules based on the file "/etc/sysconfig/SuSEfirewall2". We will install SuSEfirewall2 and then configure the port to access OpenVPN, then we will enable NAT with an iptables script for OpenVPN.

Install SuSEfirewall2 with the zypper command:

zypper in SuSEfirewall2

Now, go to the sysconfig directory, and edit the SuSEfirewall2 configuration file:

cd /etc/sysconfig/
vim SuSEfirewall2

Line 134 - Enable route.

FW_ROUTE="yes"

Line 253 - Enable TCP port 22 for SSH access from outside the network.

FW_SERVICES_EXT_UDP="22"

Line 267 - Enable udp port for openvpn client access - port 2034.

FW_SERVICES_EXT_UDP="2034"

Line 877 - Enable custom rules SuSEfirewall2.

FW_CUSTOMRULES="/etc/sysconfig/scripts/SuSEfirewall2-custom"

Save and exit.

Next, edit the SuSEfirewall2 custom rules in the scripts directory.

cd /etc/sysconfig/scripts/
vim SuSEfirewall2-custom

Inside of the "fw_custom_after_chain_creation" directive, paste the new iptables rules for OpenVPN:

iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -s 10.10.2.0/24 -j ACCEPT
iptables -A FORWARD -j REJECT
iptables -t nat -A POSTROUTING -s 10.10.2.0/24 -o eth0 -j MASQUERADE

Save and exit.

Note:

IP 10.10.2.0/24 is the network from the server.conf OpenVPN configuration file.

Now we can enable forwarding by adding this new configuration line to the sysctl.conf file.

vim /etc/sysctl.conf

Paste configuration below:

net.ipv4.ip_forward = 1

Save and exit.

Note:

If you have the line already in the file, change the value from "0" to "1" instead of adding a new line.

Now run the command below to apply the configuration change.

sysctl -p

Start SuSEfirewall2 and OpenVPN server:

systemctl start SuSEfirewall2
systemctl start [email protected]

If you have an error, you can see the detailed error message in the OpenVPN log.

Add all services to the system startup:

systemctl enable SuSEfirewall2
systemctl enable [email protected]

Step 5 - Configure the Client

Download the client key and certificate from the keys directory to your local computer. You can use the scp command or sftp, I'm here using scp:

Command that has to be run on the local computer.

scp [email protected]:~/etc/openvpn/keys/ca.crt ~/myvpn/
scp [email protected]:~/etc/openvpn/keys/client1.crt ~/myvpn/
scp [email protected]:~/etc/openvpn/keys/client1.key ~/myvpn/

In the myvpn directory, create a new configuration file for the client "client1.ovpn".

cd ~/myvpn/
vim client1.ovpn

Paste the configuration below:

client
dev tun
proto udp

#Server IP and Port
remote SERVERIP 2034

resolv-retry infinite
nobind
persist-key
persist-tun
mute-replay-warnings
ca ca.crt
cert client1.crt
key client1.key
ns-cert-type server
comp-lzo

Save and exit.

To connect to our VPN, you can install a VPN client or if you are using Linux, you can use the "Network-Manager". If you want to test the VPN with a terminal, you can use the command below:

cd ~/myvpn/
sudo openvpn --config client1.ovpn

Connect with the OpenVPN command.

Reference

https://en.opensuse.org/SDB:OpenVPN_Installation_and_Setup

https://www.howtoforge.com/tutorial/how-to-install-openvpn-on-centos-7/

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2 Comment(s)

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Comments

From: Zane Hale at: 2016-06-15 12:56:59

This how to fails for me at step 4 with an error at "systemctl start [email protected]"

with the error statement "Failed to start OpenVPN tunneling daemon instance using /etc/openvpn/server.conf."

Apparently the command should be "systemctl start [email protected]" but his fails as well.

There appears to be a typo in your instructions in step 5 configuring the firewall TCP. Are there possibly others?

From: akame at: 2016-06-15 15:07:31

Check your openvpn log on "/var/log/openvpn/openvpn.log" to see the error.