OpenVPN is an SSL/TLS VPN solution. It is able to traverse NAT connections and firewalls. This page explain briefly how to configure a VPN with OpenVPN, from both server-side and client-side.
Install the openvpn package on both client and server.
# apt-get install openvpn
To enable OpenVPN in the Gnome NetworkManager, the additional package network-manager-openvpn-gnome has to be installed:
# apt-get install network-manager-openvpn-gnome
OpenVPN can authenticate users via user/pass, pre-shared key, certificates, etc.
Test a raw connection.
From a server shell, run
# openvpn --remote CLIENT_IP --dev tun1 --ifconfig 10.9.8.1 10.9.8.2
if your client has a static IP#; otherwise, run
# openvpn --dev tun1 --ifconfig 10.9.8.1 10.9.8.2
You should see console output resembling
Wed Mar 7 06:03:03 2012 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables Wed Mar 7 06:03:03 2012 ******* WARNING *******: all encryption and authentication features disabled -- all data will be tunnelled as cleartext Wed Mar 7 06:03:03 2012 TUN/TAP device tun1 opened ...
While openvpn is running, check your network configuration with sudo ifconfig -a. Output should include
tun1 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.9.8.1 P-t-P:10.9.8.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:13 errors:0 dropped:0 overruns:0 frame:0 TX packets:16 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:2262 (2.2 KiB) TX bytes:1819 (1.7 KiB)
Note that, if you kill openvpn (e.g., with Control-c in its console), you will not see the above network interface.
# openvpn --remote SERVER_IP --dev tun1 --ifconfig 10.9.8.2 10.9.8.1 ... Wed Mar 7 18:05:30 2012 Peer Connection Initiated with [AF_INET]SERVER_IP:PORT Wed Mar 7 18:05:30 2012 Initialization Sequence Completed ...
You may also test with ping.
In the server's /etc/openvpn directory, run the following command to generate a static key:
# openvpn --genkey --secret static.key
Copy this static key to the clients /etc/openvpn directory using a secure channel like scp or sftp.
On the server, create a new /etc/openvpn/tun0.conf file and add the following:
dev tun0 ifconfig 10.9.8.1 10.9.8.2 secret /etc/openvpn/static.key
Where 10.9.8.x is your VPN subnetwork, 10.9.8.1 will be IP of the server, 10.9.8.2 is IP of client.
On the client, copy /etc/openvpn/static.key from server and create a new /etc/openvpn/tun0.conf file and add the following:
remote your-server.org dev tun0 ifconfig 10.9.8.2 10.9.8.1 secret /etc/openvpn/static.key
On the server's firewall, open up UDP 1194 (default port).
If you are using ?shorewall, on both devices, add a new VPN zone to represent tun0 and create a default policy for it. This means adding something to the following files in /etc/shorewall:
Bear in mind that 90% of all connection problems encountered by new OpenVPN users are firewall-related.
Start OpenVPN by hand on both sides with the following command:
# openvpn --config /etc/openvpn/tun0.conf --verb 6 // verbose output.
You should probably configure your route at this step.
To verify that the VPN is running, you should be able to ping 10.9.8.2 from the server and 10.9.8.1 from the client.
In server, copy key generating script from openvpn example to /etc/openvpn and add executable permission:
# cd /etc/openvpn # mkdir easy-rsa
In Jessie and above easy-rsa is a separate package. So you'll have to install that in addition to openvpn.
# cp -R /usr/share/doc/openvpn/examples/easy-rsa/2.0/* easy-rsa/
On Jessie and above:
# apt-get install easy-rsa # make-cadir easy-rsa/
Edit /etc/openvpn/easy-rsa/vars bottom according to your organization.
export KEY_COUNTRY="US" export KEY_PROVINCE="CA" export KEY_CITY="SanFrancisco" export KEY_ORG="Fort-Funston" export KEY_EMAIL="mail@domain"
Execute the following command:
# cd easy-rsa/ # . ./vars # set environment variables # ./clean-all
Create a symbolic link of the OpenSSL config file with the correct version, so it can be used by the commands of Easy-RSA. In Debian Stretch, it can be done by executing the following command:
# ln -s openssl-1.0.0.cnf openssl.cnf
- only .key files should be kept confidential.
- .crt and .csr files can be sent over insecure channels such as plaintext email.
- do not need to copy a .key file between computers.
- each computer will have its own certificate/key pair.
Generate CERTIFICATE AUTHORITY (CA) CERTIFICATE/KEY:
It will generate ca.crt and ca.key in /etc/openvpn/easy-rsa/keys/ directory.
Generate BUILD AN INTERMEDIATE CERTIFICATE AUTHORITY CERTIFICATE/KEY (optional):
# ./build-key-server server
It will generate server.crt and server.key in /etc/openvpn/easy-rsa/keys/, and signed with your root certificate.
Generate BUILD DIFFIE-HELLMAN PARAMETERS (necessary for the server end of a SSL/TLS connection):
Generate key for each client: Use one of the two (build-key or build-key-pass). You'll be asked for "Enter PEM pass phrase", this is the passphrase you'll need to login at the client.
Generate key with password (this protect the key and request the password every time that you connect to the server), for each client:
It will generate keys in /etc/openvpn/easy-rsa/keys/
Copy the ca.crt, clientname.crt, clientname.key from Server to Client /etc/openvpn/easy-rsa/keys/ directory.
Test the connectivity from command line.
openvpn --dev tun1 --ifconfig 10.9.8.1 10.9.8.2 --tls-server --dh /etc/openvpn/easy-rsa/keys/dh2048.pem --ca /etc/openvpn/easy-rsa/keys/ca.crt --cert /etc/openvpn/easy-rsa/keys/server.crt --key /etc/openvpn/easy-rsa/keys/server.key --reneg-sec 60 --verb 5
openvpn --remote SERVER_IP --dev tun1 --ifconfig 10.9.8.2 10.9.8.1 --tls-client --ca /etc/openvpn/easy-rsa/keys/ca.crt --cert /etc/openvpn/easy-rsa/keys/clientname.crt --key /etc/openvpn/easy-rsa/keys/clientname.key --reneg-sec 60 --verb 5
If the connection is successful create file configuration.
In Server create /etc/openvpn/server.conf as follows:
port 1194 proto udp dev tun ca /etc/openvpn/easy-rsa/keys/ca.crt # generated keys cert /etc/openvpn/easy-rsa/keys/server.crt key /etc/openvpn/easy-rsa/keys/server.key # keep secret dh /etc/openvpn/easy-rsa/keys/dh2048.pem server 10.9.8.0 255.255.255.0 # internal tun0 connection IP ifconfig-pool-persist ipp.txt keepalive 10 120 comp-lzo # Compression - must be turned on at both end persist-key persist-tun status log/openvpn-status.log verb 3 # verbose mode client-to-client
Create log directory:
# cd /etc/openvpn # mkdir -p log/ # touch log/openvpn-status.log
# service openvpn restart
Note that the /etc/init.d/openvpn script will start an openvpn server for every .conf file in /etc/openvpn/, so if you still have the tun0.conf file from above, rename it to something else than *.conf. In the case of systemd only one openvpn server is started by default.
In Client create /etc/openvpn/client.conf as follows:
(note: you may use graphical vpn tool network-manager UI by providing the key and certificates)
client dev tun port 1194 proto udp remote VPNSERVER_IP 1194 # VPN server IP : PORT nobind ca /etc/openvpn/easy-rsa/keys/ca.crt cert /etc/openvpn/easy-rsa/keys/clientname.crt key /etc/openvpn/easy-rsa/keys/clientname.key comp-lzo persist-key persist-tun verb 3
# service openvpn restart
Debian Server with Android / iOS devices
OpenVPN can be configured to use with Android / iOS devices.
In Debian Server, create required certificates if you have a fresh installation of ?OpenVpn:
# cd /usr/share/doc/openvpn/examples/easy-rsa/2.0 # . ./vars # ./clean-all # ./build-ca # ./build-key-server server # ./build-key client # ./build-dh # cd keys # mv *.pem *.crt *.csr *.key /etc/openvpn # cd /usr/share/doc/openvpn/examples/sample-config-files # gunzip -c server.conf.gz > /etc/openvpn/server.conf
Modify below lines in /etc/openvpn/server.conf:
... proto tcp push "redirect-gateway def1 bypass-dhcp" push "dhcp-option DNS 220.127.116.11" user nobody group nogroup ...
18.104.22.168 is Google DNS server. You may change to your preferred DNS server.
When completed, restart OpenVPN server to use the new configuration:
# /etc/init.d/openvpn restart
Or on systems using systemd:
# service openvpn restart
Create client profile file /etc/openvpn/client.ovpn and attach certificates to it:
# cd /etc/openvpn # cp /usr/share/doc/openvpn/examples/sample-config-files/client.conf client.ovpn # echo "key-direction 1" >> client.ovpn # echo "<ca>" >> client.ovpn # cat ca.crt | grep -A 100 "BEGIN CERTIFICATE" | grep -B 100 "END CERTIFICATE" >> client.ovpn # echo "</ca>" >> client.ovpn # echo "<cert>" >> client.ovpn # cat client.crt | grep -A 100 "BEGIN CERTIFICATE" | grep -B 100 "END CERTIFICATE" >> client.ovpn # echo "</cert>" >> client.ovpn # echo "<key>" >> client.ovpn # cat client.key | grep -A 100 "BEGIN PRIVATE KEY" | grep -B 100 "END PRIVATE KEY" >> client.ovpn # echo "</key>" >> client.ovpn
Modify below lines in client profile file /etc/openvpn/client.ovpn:
... proto tcp remote YourServerIp YourServerPort mute-replay-warnings # ca ca.crt # cert client.crt # key client.key key-direction 1 ...
where ?YourServerIp and ?YourServerPort should be changed to your server. Three lines (#ca, #cert, #key) are remarked as the required certificates were attached to the profile file instead of individual files.
e-mail or upload the client configuration file /etc/openvpn/client.ovpn to google drive in order to download to iPhone.
For iOS devices, install OpenVPN Connect client. Then transfer the client configuration file /etc/openvpn/client.ovpn to the device by e-mail or by Google Drive. Open the configuration file in Mail apps or Google Drive apps.
For Android devices, install OpenVPN Connect client. Then copy the client configuration file /etc/openvpn/client.ovpn to the storage of the device. Open the configuration file in OpenVPN apps.
Forward traffic via VPN
In Server enable runtime IP forwarding:
echo 1 > /proc/sys/net/ipv4/ip_forward
Edit /etc/sysctl.conf uncomment the following line to make it permanent:
net.ipv4.ip_forward = 1
Execute the following command in server for testing:
iptables -A FORWARD -i eth0 -o tun0 -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -s 10.9.8.0/24 -o eth0 -j ACCEPT iptables -t nat -A POSTROUTING -s 10.9.8.0/24 -o eth0 -j MASQUERADE
You may also use the rc.firewall-iptables script from TLDP Masquerade as an alternative.
# ip route add VPNSERVER_IP via LOCALGATEWAY_IP dev eth0 proto static # ip route change default via 10.9.8.5 dev tun0 proto static //client tun0 10.9.8.5
If you use graphical client generally you may not need to execute these command.
If everying is working fine, save the iptables rules:
# iptables-save > /etc/iptables.up.rules
# iptables-restore < /etc/iptables.up.rules
add this to startup script. Debian wiki iptables page for details.
By default, all configured VPNs are started during system boot. Edit /etc/default/openvpn to start specific VPNs or to disable this behavior. Systemd users may need to run systemctl daemon-reload once to enable new VPNs.
openvpn ifupdown hooks are also available for starting/stopping tunnels using /etc/network/interfaces, e.g.:
auto dsl iface dsl inet ppp provider dsl-provider openvpn work_vpn
See /usr/share/doc/openvpn/README.Debian.gz for more information.
To automatically start a VPN located in /etc/openvpn/client/ or /etc/openvpn/server/, enable openvpn-client@<name>.service or openvpn-server@<name>.service. For instance, a client configuration located in /etc/openvpn/client/vpn0.conf would be automatically started by enabling firstname.lastname@example.org.
Application to a VPN passing through a http proxy
This part describe how to configure a VPN to pass through a http proxy, which allow only trafic on port 443 (and 80). This use the http_proxy of OpenVPN.
- First of all, check that the port 443 isn't already used by another service on your server.
Configure OpenVPN on server side by adding port 443 and proto tcp-server to the configuration file.
Configure OpenVPN on the client side by adding port 443, proto tcp-client and http-proxy 22.214.171.124 8080 to the configuration file.
Where 126.96.36.199 and 8080 are IP and port of your proxy.
- Now you should launch OpenVPN on the server and next on the client.
- At this time, you should configure routes to use the VPN tunnel:
Remove the default route through the proxy: route del default eth0
Add default route through your VPN: route add default gw 10.9.8.1 dev tun0
You should keep the route to the proxy with: route add 188.8.131.52 eth0
Update your /etc/resolv.conf according to your needs.
Explain how to enable the management interface (http://openvpn.net/index.php/open-source/documentation/miscellaneous/79-management-interface.html)