-----

Install and Configure an OpenVPN Server on CentOS 6

This guide will provide you with all the steps necessary to install a simple OpenVPN server on CentOS 6.

First, login to the SolusVM control panel for your VPS and enable TUN/TAP from the settings menu.

Now, SSH into your VPS where you'll need to install the Enterprise Linux (EPEL) repository:

yum install -y epel-release

Then install OpenVPN:

yum install -y openvpn easy-rsa

Copy the sample configs to make editing it easier:

cp /usr/share/doc/openvpn-*/sample/sample-config-files/server.conf /etc/openvpn

Open the config file to edit with the required settings:

vi /etc/openvpn/server.conf

- To enable editing in vi, just hit the "i" key on your keyboard.

Find this line and uncomment it by removing the ; at beginning of the line:

push "redirect-gateway def1 bypass-dhcp"

Now scroll down a bit to uncomment these lines:

push "dhcp-option DNS 208.67.222.222"

push "dhcp-option DNS 208.67.220.220"

Then scroll down further to uncomment these lines:

user nobody

group nobody

Once the edits are done, save the file and exit vi.

- To save and exit in vi, just hit the "ESC" key on your keyboard to exit editing mode, then type ":x" (without quotes) and hit enter.

Generate RSA Keys and Certificates Using easy-rsa

OpenVPN requires keys and certificates to authenticate users, so follow these steps to do so:

mkdir -p /etc/openvpn/easy-rsa/keys cp -r /usr/share/easy-rsa/2.0/* /etc/openvpn/easy-rsa

Copy the OpenSSL configuration file to the easy-rsa folder:

cp /etc/openvpn/easy-rsa/openssl-1.0.0.cnf /etc/openvpn/easy-rsa/openssl.cnf

Now we'll start the build process for the key/certificate. You will be asked to enter various information, so just fill them out to your liking.

# cd /etc/openvpn/easy-rsa

 source ./vars

 ./clean-all

 ./build-ca

 ./build-key-server server

Then generate the Diffie Hellman key exchange files:

./build-dh

cd /etc/openvpn/easy-rsa/keys

cp dh2048.pem ca.crt server.crt server.key /etc/openvpn

Now create the client ceritificates to allow clients to authenticate with the server:

cd /etc/openvpn/easy-rsa

./build-key client

Configuring iptables and sysctl:

Now to configure your iptables and sysctl to function properly with the VPN:

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -j SNAT --to-source 104.168.100.156

iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT

service iptables save

Enable IP forwarding:

vi /etc/sysctl.conf

Set this setting equal to 1:

# net.ipv4.ip_forward = 1

Apply the sysctl settings and start up OpenVPN as well as set it to start up on boot:

sysctl -p

service openvpn start

chkconfig openvpn on

OpenVPN Client for Windows

With your OpenVPN server now online, you'll need to configure your OpenVPN client. You can download it here:

https://openvpn.net/index.php/open-source/downloads.html

First, find the certificate and key files on your server:

Navigate to this directory to find them:

/etc/openvpn/easy-rsa/keys/

These are the files you need:

ca.crt

client.crt

client.key

You will need to paste the contents of each file for the next step. To view each file, simply use the command "vi filename" to view them.

Now create a file on your computer named "client.ovpn" and fill in the following:

- "client" is the name of the user (from when you created the key/certificate)

- replace x.x.x.x with your BeastNode VPS IP

- paste the entire contents of each crt and key file from above as specified in the config

client

dev tun

proto udp

remote x.x.x.x 1194

resolv-retry infinite

nobind

persist-key

persist-tun

comp-lzo

verb 3

<ca>

Contents of ca.crt

</ca>

<cert>

Contents of client.crt

</cert>

<key>

Contents of client.key

</key>

Now all you need to do to connect to your VPN is to go into the OpenVPN client and do the following:

1. Click on the + (plus) symbol next to "Connection Profiles", select "Local file", click on Import, and navigate to the client.ovpn file you made previously.

2. Enter your desired name for the profile and make sure "Completely trust this profile" is checked, then click Save.

3. You should see the newly added profile in the client window - simply click on it to connect to your VPN and you're all done!

------------     --------X ------------------

OpenVPN Server On CentOS 6.5

To enable EPEL repository On CentOS, refer the following link.

• Install EPEL Repository On CentOS / RHEL / Scientific Linux 6

Also, update the system using the following command:

yum update

Install OpenVPN Software

Install the OpenVPN software using the following command:

yum install openvpn easy-rsa

The easy-rsa scripts are located by default in the /usr/share/easy-rsa/ directory. Make a directory /easy-rsa/keys inside the /etc/openvpn directory and copy the scripts to that directory as shown below:

mkdir -p /etc/openvpn/easy-rsa/keys cp -rf /usr/share/easy-rsa/2.0/* /etc/openvpn/easy-rsa/

Generate CA Certificate and CA key

Edit file /etc/openvpn/easy-rsa/2.0/vars,

vi /etc/openvpn/easy-rsa/vars

And, change the values that matches with your country, state, city, mail id etc.

[...] # Don't leave any of these fields blank. export KEY_COUNTRY="IN" export KEY_PROVINCE="TN" export KEY_CITY="Erode" export KEY_ORG="Unixmen" export KEY_EMAIL="sk@unixmen.com" export KEY_OU="server" [...]

Go to the openvpn/easy-rsa directory:

cd /etc/openvpn/easy-rsa/

Enter the following commands one by one to initialize the certificate authority:

cp openssl-1.0.0.cnf openssl.cnf source ./vars ./clean-all

Then, run the following command to generate CA certificate and CA key:

./build-ca

Sample output:

Generating a 2048 bit RSA private key ......................................................+++ ............................................................+++ writing new private key to 'ca.key' ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [IN]: ----> Press Enter State or Province Name (full name) [TN]: ----> Press Enter Locality Name (eg, city) [Erode]: ----> Press Enter Organization Name (eg, company) [Unixmen]: ----> Press Enter Organizational Unit Name (eg, section) [server]: ----> Press Enter Common Name (eg, your name or your server's hostname) [Unixmen CA]: ----> Press Enter Name [EasyRSA]: ----> Press Enter Email Address [sk@unixmen.com]: ----> Press Enter

We have now generated the CA certificate and CA key. Then create certificate and key for server using the following command:

./build-key-server server

Sample output:

Generating a 2048 bit RSA private key ....................+++ .............+++ writing new private key to 'server.key' ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [IN]: ----> Press Enter State or Province Name (full name) [TN]: ----> Press Enter Locality Name (eg, city) [Erode]: ----> Press Enter Organization Name (eg, company) [Unixmen]: ----> Press Enter Organizational Unit Name (eg, section) [server]: ----> Press Enter Common Name (eg, your name or your server's hostname) [server]: ----> Press Enter Name [EasyRSA]: ----> Press Enter Email Address [sk@unixmen.com]: ----> Press Enter  Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: ----> Press Enter       An optional company name []: ----> Press Enter Using configuration from /etc/openvpn/easy-rsa/openssl-1.0.0.cnf Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows countryName           :PRINTABLE:'IN' stateOrProvinceName   :PRINTABLE:'TN' localityName          :PRINTABLE:'Erode' organizationName      :PRINTABLE:'Unixmen' organizationalUnitName:PRINTABLE:'server' commonName            :PRINTABLE:'server' name                  :PRINTABLE:'EasyRSA' emailAddress          :IA5STRING:'sk@unixmen.com' Certificate is to be certified until Mar 23 12:21:34 2024 GMT (3650 days) Sign the certificate? [y/n]:y ----> Type Y and Press Enter  1 out of 1 certificate requests certified, commit? [y/n]y ----> Type Y and Press Enter Write out database with 1 new entries Data Base Updated

Create certificate and key for VPN clients using the following command:

./build-key client

If you want to create certificate and key files for each client, you should replace the clientparameter with an unique identifier.

Sample output:

Generating a 2048 bit RSA private key .......+++ ..................................................................................................+++ writing new private key to 'client.key' ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [IN]: ----> Press Enter State or Province Name (full name) [TN]: ----> Press Enter Locality Name (eg, city) [Erode]: ----> Press Enter Organization Name (eg, company) [Unixmen]: ----> Press Enter Organizational Unit Name (eg, section) [server]: ----> Press Enter Common Name (eg, your name or your server's hostname) [client]: ----> Press Enter Name [EasyRSA]: ----> Press Enter Email Address [sk@unixmen.com]: ----> Press Enter  Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: ----> Press Enter An optional company name []: ----> Press Enter Using configuration from /etc/openvpn/easy-rsa/openssl-1.0.0.cnf Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows countryName           :PRINTABLE:'IN' stateOrProvinceName   :PRINTABLE:'TN' localityName          :PRINTABLE:'Erode' organizationName      :PRINTABLE:'Unixmen' organizationalUnitName:PRINTABLE:'server' commonName            :PRINTABLE:'client' name                  :PRINTABLE:'EasyRSA' emailAddress          :IA5STRING:'sk@unixmen.com' Certificate is to be certified until Mar 23 12:23:44 2024 GMT (3650 days) Sign the certificate? [y/n]:y ----> Type Y and Press Enter  1 out of 1 certificate requests certified, commit? [y/n]y ----> Type Y and Press Enter Write out database with 1 new entries Data Base Updated

Generate Diffie Hellman Parameter

Enter the following command to generate DH parameter.

./build-dh

Sample output:

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

The necessary keys and certificates will be generated in the /etc/openvpn/easy-rsa/keys/directory. Copy the following certificate and key files to the /etc/openvpn/ directory.

• ca.crt

• dh2048.pem

• server.crt

• server.key

Go to the directory /etc/openvpn/easy-rsa/keys/ and enter the following command to transfer the above files to /etc/openvpn/ directory.

cd /etc/openvpn/easy-rsa/keys/ cp dh2048.pem ca.crt server.crt server.key /etc/openvpn/

And then, you must copy all client certificates and keys to the remote VPN clients in order to authenticate to the VPN server. In our case, we have generated certificates and keys to only one client, so we have to copy the following files to the VPN client.

• ca.crt

• client.crt

• client.key

As I mentioned before, I have another system running with CentOS 6.5 that acts as my VPN client. Make sure you have installed openvpn package on your client systems. Then, copy the above files to your VPN client system, using the following command:

scp ca.crt client.crt client.key root@192.168.1.101:/etc/openvpn

Copy the keys with caution. If anyone have chances to get the keys, they can easily intrude and get full access to your virtual private network.

Remove Client access to VPN server

If you want to remove a user’s access to the VPN server, enter the following command:

. /etc/openvpn/easy-rsa/2.0/vars . /etc/openvpn/easy-rsa/2.0/revoke-full client

The above commands remove the user who have the certificate to access the VPN server.

Configuring VPN Server

Now, we have to configure our VPN server. Copy the file server.conf file to /etc/openvpn/ directory.

cp /usr/share/doc/openvpn-2.3.2/sample/sample-config-files/server.conf /etc/openvpn/

Edit file server.conf,

vi /etc/openvpn/server.conf

Find and uncomment the following lines to route client systems traffic through OpenVPN server.

[...]  # Substitute 2048 for 1024 if you are using # 2048 bit keys. dh dh2048.pem  [...]  push "redirect-gateway def1 bypass-dhcp"  [...]

Also, Uncomment and change the DNS servers to reflect your own DNS values. Here I am using Google public DNS servers.

[...]  push "dhcp-option DNS 8.8.8.8" push "dhcp-option DNS 8.8.4.4"  [...]

Uncomment the following lines:

[...]  user nobody group nobody  [...]

Save and close the file.

Then we need to copy and edit the client.conf file. We need this file to be transferred to the VPN clients. First copy the file to any location (ex. /home directory).

cp /usr/share/doc/openvpn-2.3.2/sample/sample-config-files/client.conf /home/

Edit file client.conf,

vi /home/client.conf

Set the VPN server host name/IP address:

# The hostname/IP and port of the server. # You can have multiple remote entries # to load balance between the servers.

remote  192.168.1.2 1194

Here 192.168.1.2 is my VPN server IP address. Next, Copy the client.conf file to your client system.

scp /home/client.conf root@192.168.1.101:/etc/openvpn

IP forwarding and routing Configuration

Edit sysctl.conf file,

vi /etc/sysctl.conf

Find the following line and set value “1” to enable IP forwarding.

# Controls IP packet forwarding

net.ipv4.ip_forward = 1

Run the following command to apply the sysctl changes.

sysctl -p

Adjust iptables to forward traffic through VPN properly.

Enter the following commands one by one:

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

Save the iptables changes using command:

service iptables save

service iptables restart

Finally, start openvpn service and make it to start automatically on every reboot using the following commands:

service openvpn start

chkconfig openvpn on

At this time, you should have a working OpenVPN server. Next, let us move to client side configuration.

Verify if VPN interface(tun0) is created using ifconfig command:

ifconfig

Sample output:

eth0      Link encap:Ethernet  HWaddr 08:00:27:46:36:62  

          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0

          inet6 addr: fe80::a00:27ff:fe46:3662/64 Scope:Link

          RX packets:604 errors:0 dropped:0 overruns:0 frame:0

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX bytes:44166 (43.1 KiB)  TX bytes:14434 (14.0 KiB)

          TX packets:100 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000

          UP LOOPBACK RUNNING  MTU:16436  Metric:1

lo        Link encap:Local Loopback  

          inet addr:127.0.0.1  Mask:255.0.0.0

          inet6 addr: ::1/128 Scope:Host

          collisions:0 txqueuelen:0

          RX packets:0 errors:0 dropped:0 overruns:0 frame:0

          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

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:0 errors:0 dropped:0 overruns:0 frame:0

          collisions:0 txqueuelen:100

          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

Part Two – VPN Client side configuration

Here, I use CentOS 6.5 as my VPN client system. And, it’s actual IP address is 192.168.1.101/24.

Install OpenVPN

Enter the following command from the Terminal to install openvpn package.

yum install openvpn

After installing openvpn, start the service and make it to run automatically on every reboot.

service openvpn start

chkconfig openvpn on

Now, check if tun0(VPN interface) is created.

ifconfig

Sample output:

eth0      Link encap:Ethernet  HWaddr 08:00:27:BE:25:49  

          inet addr:192.168.1.101  Bcast:192.168.1.255  Mask:255.255.255.0

          inet6 addr: fe80::a00:27ff:febe:2549/64 Scope:Link

          RX packets:537 errors:0 dropped:0 overruns:0 frame:0

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX bytes:52177 (50.9 KiB)  TX bytes:50170 (48.9 KiB)

          TX packets:387 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000

          UP LOOPBACK RUNNING  MTU:16436  Metric:1

lo        Link encap:Local Loopback  

          inet addr:127.0.0.1  Mask:255.0.0.0

          inet6 addr: ::1/128 Scope:Host

          collisions:0 txqueuelen:0

          RX packets:0 errors:0 dropped:0 overruns:0 frame:0

          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  

          inet addr:10.8.0.6  P-t-P:10.8.0.5  Mask:255.255.255.255

          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1

          RX packets:0 errors:0 dropped:0 overruns:0 frame:0

          collisions:0 txqueuelen:100

          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

As you see in the above output, the VPN server has automatically assigned IP address 10.8.0.6 to my VPN client.

Check if you can ping your VPN server from client system.

ping 10.8.0.1

10.8.0.1 is my VPN server tun0 address.

Sample output:

PING 10.8.0.1 (10.8.0.1) 56(84) bytes of data. 64 bytes from 10.8.0.1: icmp_seq=1 ttl=64 time=9.61 ms 64 bytes from 10.8.0.1: icmp_seq=2 ttl=64 time=7.17 ms 64 bytes from 10.8.0.1: icmp_seq=3 ttl=64 time=4.87 ms

That’s it. Now the VPN server and client are ready. Connect to your VPN server securely. Happy VPNing!

                                         -------------------------------X----------------------------------------

ll

ll

ll

                                                                       ------------------------X--------------------------

                                           -------------------------X--------------------------------

---------------------------------------------------------------------------------------------------------------------------------------------------

Installation and configuration of OpenVPN server on Centos 6.8

This blog will help you with the installation and configuration of OpenVPN server on centos 6.8 on DigitalOcean

OpenVPN server version : 2.3.14

CentOS Version : CentOS 6.8

1. Login to server and switch as root user

$ sudo su –

or

$ su –

2. Install EPEL repository

# rpm -Uivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

3. Update and install openvpn-server related packages

# yum update && yum -y install openvpn easy-rsa

4. Generate required certificates and key

# mkdir -p /etc/openvpn/easy-rsa/keys

# cp -r /usr/share/easy-rsa/2.0/* /etc/openvpn/easy-rsa/

# cd /etc/openvpn/easy-rsa

# source ./vars

# ./clean-all

# ./build-ca

The above command will create ca certificate, and it will be prompted for some values. Please see the below image  for sample values :

# ./build-key-server server

The above command will create server certificate, and it will be prompted for some values. Please see the below image for sample values :

# ./build-dh

NOTE : All keys and certs will be saved in /etc/openvpn/easy-rsa/keys folder

5. copy all  keys and certificates to /etc/openvpn folder

# cd /etc/openvpn/easy-rsa/keys

# cp dh2048.pem ca.crt server.crt server.key /etc/openvpn/

6. Create a new file in /etc/openvpn/ folder with the name server.conf , and add the following lines

port 1194

proto udp

dev tun

ca ca.crt

cert server.crt

key server.key

dh dh2048.pem

server 10.8.0.0 255.255.255.0

ifconfig-pool-persist ipp.txt

push "redirect-gateway def1 bypass-dhcp"

push "dhcp-option DNS 8.8.8.8"

push "dhcp-option DNS 8.8.4.4"

keepalive 10 120

comp-lzo

max-clients 100

user nobody

group nobody

persist-key

persist-tun

status /var/log/openvpn-status.log

log-append /var/log/openvpn.log

verb 3

7. Enable IP forwarding. Open /etc/sysctl.conf and change the line

from

net.ipv4.ip_forward =  0

to

net.ipv4.ip_forward = 1

8. Add  iptables rules for proper routing

# iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT

# iptables -A FORWARD -m state –state RELATED,ESTABLISHED -j ACCEPT

# iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

9. Save and Restart iptables

# service iptables save

# service iptables restart

10. Start openvpn server

# service openvpn start

# chkconfig openvpn on

11. Disable all other ports except 22 (ssh) and 1194  (openvpn).

This is optional, and you do this only if you are running openvpn server on your machine.

Note : On my server, the default chain policy is ACCEPT

# iptables -A INPUT -p tcp –dport 22 -j ACCEPT

# iptables -A OUTPUT -p tcp –sport 22 -j ACCEPT

# iptables -A INPUT -p udp –dport 1194 -j ACCEPT

# iptables -A OUTPUT -p udp –sport 1194 -j ACCEPT

# iptables -A INPUT -j DROP

# iptables -A OUTPUT -j DROP

Done !!.

Click Here to configure OpenVPN client on Windows and Linux machine.

---------------------------------------------------------------------------------------------------------------------------------------------------

##########################################################X

###############################################

---