Centos-7

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Install OpenVPN to Configure Virtual Private Network.

This example is based on the environment like follows.

By settings of OpenVPN Server/Client, [tun] interface will be configured automatically and when connecting with VPN from Client to Server, Client can access to the the local network of the Server.

On this example, it needs to set IP Masquerading on Router, too.

+----------------------+ | [ OpenVPN Server ] |192.168.100.1 | dlp.srv.world +--------+ | |tun | +-----------+----------+ | eth0|10.0.0.29 | | | | Local Network | 10.0.0.1| | +------+-----+ | -------| Router |-------------|----- +------+-----+ | | | | Internet | --------------+-------------------|----- | | | Local Network | 192.168.0.100| | +-----------+----------+ | | |tun | | VPN Client +--------+ | |192.168.100.x +----------------------+

[1]

Install OpenVPN.

# install from EPEL

[root@dlp ~]# dnf --enablerepo=epel -y install openvpn easy-rsa net-tools

[2]

Create CA and Certificates.

[root@dlp ~]# cd /usr/share/easy-rsa/3

# initialize

[root@dlp 3]# ./easyrsa init-pki

init-pki complete; you may now create a CA or requests. Your newly created PKI dir is: /usr/share/easy-rsa/3/pki

# create CA

[root@dlp 3]# ./easyrsa build-ca

Using SSL: openssl OpenSSL 1.1.1c FIPS 28 May 2019 # set any pass-phrase Enter New CA Key Passphrase: Re-Enter New CA Key Passphrase: Generating RSA private key, 2048 bit long modulus (2 primes) .......+++++ ...........................................+++++ e is 65537 (0x010001) # OK to ignore the error below Can't load /usr/share/easy-rsa/3/pki/.rnd into RNG 139779519366976:error:2406F079:random number generator:RAND_load_file:Cannot open file:crypto/rand/randfile.c:98:Filename=/usr/share/easy-rsa/3/pki/.rnd 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. ----- # set any name Common Name (eg: your user, host, or server name) [Easy-RSA CA]:Server-CA CA creation complete and you may now import and sign cert requests. Your new CA certificate file for publishing is at: /usr/share/easy-rsa/3/pki/ca.crt

# create server certificates

# any name is OK for [server1] name

# (it is set for file name of certs or commonName)

[root@dlp 3]# ./easyrsa build-server-full server1 nopass

Using SSL: openssl OpenSSL 1.1.1c FIPS 28 May 2019 Generating a RSA private key ..................................+++++ ...................................+++++ writing new private key to '/usr/share/easy-rsa/3/pki/private/server1.key.Mxv13uLARL' ----- Using configuration from /usr/share/easy-rsa/3/pki/safessl-easyrsa.cnf # answer with pass-phrase set on CA Enter pass phrase for /usr/share/easy-rsa/3/pki/private/ca.key: Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows commonName :ASN.1 12:'server1' Certificate is to be certified until Jan 25 03:52:49 2023 GMT (1080 days) Write out database with 1 new entries Data Base Updated

# create client certificates

# any name is OK for [client1] name

# (it is set for file name of certs or commonName)

[root@dlp 3]# ./easyrsa build-client-full client1 nopass

Using SSL: openssl OpenSSL 1.1.1c FIPS 28 May 2019 Generating a RSA private key .............+++++ ................+++++ writing new private key to '/usr/share/easy-rsa/3/pki/private/client1.key.JZkbIpNr3Y' ----- Using configuration from /usr/share/easy-rsa/3/pki/safessl-easyrsa.cnf # answer with pass-phrase set on CA Enter pass phrase for /usr/share/easy-rsa/3/pki/private/ca.key: Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows commonName :ASN.1 12:'client1' Certificate is to be certified until Jan 25 03:54:36 2023 GMT (1080 days) Write out database with 1 new entries Data Base Updated

# generate Diffie Hellman ( DH ) parameter

[root@dlp 3]# ./easyrsa gen-dh

Using SSL: openssl OpenSSL 1.1.1c FIPS 28 May 2019 Generating DH parameters, 2048 bit long safe prime, generator 2 This is going to take a long time ............++*++*++*++* DH parameters of size 2048 created at /usr/share/easy-rsa/3/pki/dh.pem

# create TLS-Auth key

[root@dlp 3]# openvpn --genkey --secret ./pki/ta.key

# copy generated certs

[root@dlp 3]# cp -pR /usr/share/easy-rsa/3/pki/{issued,private,ca.crt,dh.pem,ta.key} /etc/openvpn/server/

[3]

Enable IP forwarding.

[root@dlp ~]# vi /etc/sysctl.d/10-ipv4_forward.conf

# create new

net.ipv4.ip_forward = 1

[root@dlp ~]# sysctl --system

[4]

Configure OpenVPN.

# copy sample configuration

[root@dlp ~]# cp /usr/share/doc/openvpn/sample/sample-config-files/server.conf /etc/openvpn/server/

[root@dlp ~]# vi /etc/openvpn/server/server.conf

# line 32: change if need (listening port of OpenVPN)

port 1194

# line 35: change if need

;proto tcp

proto udp

# line 78: specify certificates

ca ca.crt

cert issued/server1.crt

key private/server1.key

# line 85: specify DH file

dh dh.pem

# line 101: specify network to be used on VPN

# any network are OK except your local network

server 192.168.100.0 255.255.255.0

# line 142: uncomment and change to your local network

push "route 10.0.0.0 255.255.255.0"

# line 231: keepalive settings

keepalive 10 120

# line 244: specify TLS-Auth key

tls-auth ta.key 0

# line 263: uncomment (enable compress)

comp-lzo

# line 281: enable persist options

persist-key

persist-tun

# line 287: change log path

status /var/log/openvpn-status.log

# line 296: change log path

log /var/log/openvpn.log log-append /var/log/openvpn.log

# line 306: specify log level (0 - 9, 9 means debug lebel)

verb 3

[root@dlp ~]# systemctl enable --now openvpn-server@server

[5]

If Firewalld is running, allow service port.

[root@dlp ~]# firewall-cmd --add-port=1194/udp --permanent

[root@dlp ~]# firewall-cmd --reload

[6]

Transfer certs follows you generated to Client Host you'd like to connect with VPN.

It's OK all for VPN Server settings.

* /etc/openvpn/server/ca.crt

* /etc/openvpn/server/ta.key

* /etc/openvpn/server/issued/client1.crt

* /etc/openvpn/server/private/client1.key

Configure VPN Client

Configure VPN Client. This example is on Windows 10.

This example is based on the environment like follows.

By settings of OpenVPN Server/Client, tun interface will be configured automatically and when connecting with VPN from Client to Server, Client can access to the the local network of the Server.

On this example, it needs to set IP Masquerading on Router, too.

+----------------------+ | [ OpenVPN Server ] |192.168.100.1 | dlp.srv.world +--------+ | |tun | +-----------+----------+ | eth0|10.0.0.29 | | | | Local Network | 10.0.0.1| | +------+-----+ | -------| Router |-------------|----- +------+-----+ | | | | Internet | --------------+-------------------|----- | | | Local Network | 192.168.0.100| | +-----------+----------+ | | |tun | | VPN Client +--------+ | |192.168.100.x +----------------------+

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

Download OpenVPN client from the site below and install it.

⇒ https://openvpn.net/community-downloads/

After installing OpenVPN client, copy the file [client.ovpn] which is under the [C:Program FilesOpenVPNsample-config] into [C:Program FilesOpenVPN.nfig] and rename it to the name which you named when created client certificates on the VPN Server. Furthermore, copy files [ca.crt], [client1.crt], [client1.key] which you created on the server to the same folder like follows.