OpenVPN
Maintainer
This howto has been developed by Jesper Knudsen (username Knuddi) which can be reached via email at mailto:contribs@swerts-knudsen.dk Website http://sme.swerts-knudsen.dk
Description
OpenVPN is an excellent way to provide remote access to users from home or on the road.OpenVPN provides a complete replacement of the time to time unreliable PPTP VPN which is a part of the standard SME distribution. This Howto is focused on using OpenVPN as a Windows 2k/XP/Vista Client to Server VPN connection. The installation consists of two steps, first the the portion which resides on the server and then the Client. I the following setup it is assumed that the local IP range for the private network is 192.168.1.0/24 and that the tunneled VPN network will be 192.168.100.0/24.
OpenVPN Server Configuration
First Collect and install the rpm`s as indicated below. The RPM are taken from DAG's repository which is pretty extensive.
cd /root mkdir openvpn cd openvpn wget http://dag.wieers.com/rpm/packages/lzo2/lzo2-2.02-3.el4.rf.i386.rpm wget http://dag.wieers.com/rpm/packages/openvpn/openvpn-2.0.9-1.el4.rf.i386.rpm rpm -Uvh *.rpm
Now its time to create the keys. The openvpn configs live in /etc/openvpn. First we need to edit the file with default values to match our installation. Open the file "vars" and Edit the default values to reflect your setup at the bottom of the file (KEY_COUNTRY, KEY_PROVINCE, KEY_CITY, KEY_ORG, KEY_EMAIL). Default we use 1024 bit Diffie Hellman but this can be changed to 2048 or even 4096 bit keys (depending of your paranoia level..)
cd /usr/share/doc/openvpn-2.0.9/easy-rsa pico vars
Now we can create the master certificate. Choose the defaults as entered into the vars file. You will need to enter values for the "Organizational Unit Name" which you can set to "VPN" and"Common Name" could be set to "Server"
source vars sh clean-all sh build-ca
Now we can build the certificate/private-key pairs for both the server and clients. Again choose choose "Organizational Unit Name" and "Common Name" as above. Do not add "A Challenge password" when asked, just press <ENTER>. The same goes for "An optional company name". Sign the certificate in the end.
sh build-key server
Now its time for the Client certificate which is pretty much the same as before. Use "Client" as "Common Name" and "VPN" for "Organizational Unit Name". Do not add "A Challenge password" when asked, just press <ENTER>. The same goes for "An optional company name". Sign the certificate in the end.
sh build-key client
Finally we build the Diffie Hellman parameters.
sh build-dh Generating DH parameters, 1024 bit long safe prime, generator 2 This is going to take a long time ..................
And it can take a long time. Your generated keys will be in /usr/share/doc/openvpn-2.0.9/easy-rsa/keys. The key names - "Server" and "Client" are simply descriptive. Choose names that suit your setup. You can create as many keys as you like using the above method. clean-all will clean out your keys directory - so be careful.
The newly generated keys needs to be copied to the the OpenVPN directory.
cp keys/ca.crt /etc/openvpn cp keys/server.crt /etc/openvpn cp keys/server.key /etc/openvpn cp keys/dh1024.pem /etc/openvpn
The OpenVPN configuration along with authentication scripts file can be downloaded from my site. Download them and make the executable for root. There will be log files created in /var/log/openvpn indicating when users have logged in and out as well as login failures. Only users that have VPN Client Access enabled in Server-Manager will be allowed to VPN.
cd /etc/openvpn mkdir -p /var/log/openvpn wget -N http://sme.swerts-knudsen.com/downloads/OpenVPN/server.conf wget -N http://sme.swerts-knudsen.com/downloads/OpenVPN/logoff.sh wget -N http://sme.swerts-knudsen.com/downloads/OpenVPN/logoff_user.pl wget -N http://sme.swerts-knudsen.com/downloads/OpenVPN/validate.sh wget -N http://sme.swerts-knudsen.com/downloads/OpenVPN/validate_user.pl wget -N http://sme.swerts-knudsen.com/downloads/OpenVPN/openvpn.up chmod 755 *.pl chmod 755 *.sh chmod 700 *.up
Now you need to make a few changes to the /etc/openvpn/server.conf. Change the domain name listed as yourdomain.com, ensure that the DNS server pushed to the clients is correct (dhcp-option DNS 192.168.1.1) and lastly the route net pushed (route 192.168.1.0).
port 1194 dev tap tls-server dh dh1024.pem ca ca.crt cert server.crt key server.key auth-user-pass-verify ./validate.sh via-env client-disconnect ./logoff.sh up ./openvpn.up mode server duplicate-cn ifconfig 192.168.100.1 255.255.255.0 ifconfig-pool 192.168.100.100 192.168.100.200 255.255.255.0 # IP range for OpenVPN clients mtu-test tun-mtu 1500 tun-mtu-extra 32 mssfix 1450 ping 10 ping-restart 120 push "ping 10" push "ping-restart 60" push "dhcp-option DOMAIN yourdomain.com" # push the DNS domain suffix push "dhcp-option DNS 192.168.1.1" # push primary DNS entry to the openvpn clients. push "route 192.168.1.0 255.255.255.0 192.168.100.1" # add route to to protected network comp-lzo status-version 2 status openvpn-status.log verb 3
If you are running this server is "server-gateway mode" you now need to open port 1194 for UDP traffic as this is the default tunnel for OpenVPN. Now go into the Server Manager panel under port forwarding and forward UDP/1194 to "localhost". If your server is in "server mode" nothing needs to be done here.
You now need to add the VPN address range as a local networks in the server-manager under the Security section.
The last thing you need to do before the installation is complete is to do a small change in the /etc/openvpn/openvpn.up file. Change the 192.168.1.1 value to match router you used when adding a local network.
#!/bin/sh route del -net 192.168.100.0 netmask 255.255.255.0 gw 192.168.1.1 route del -net 192.168.100.0 netmask 255.255.255.0 dev tap0 route add -net 192.168.100.0 netmask 255.255.255.0 gw 192.168.100.1
When you have changed the file to match your network we start the service.
/etc/init.d/openvpn start
Verify that the service is running correctly by issuing an "ifconfig" and see the new "tap0" device
tap0 Link encap:Ethernet HWaddr 00:FF:A3:3C:75:18
inet addr:192.168.100.1 Bcast:192.168.100.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:178204868 errors:0 dropped:0 overruns:0 frame:0
TX packets:192915252 errors:0 dropped:1880 overruns:0 carrier:0
collisions:0
RX bytes:1802570258 (1719.0 Mb) TX bytes:1338165457 (1276.1 Mb)
Now you want to ensure the the OpenVPN service starts every time you reboot your SME server.
ln -s /etc/rc.d/init.d/openvpn /etc/rc7.d/S99OpenVPN
OpenVPN Client Configuration
The Win2k/XP/Vista client installation is quite simple and pretty much only require the Windows GUI and a configuration file. The Windows GUI can be downloaded from openvpn.net. If you run Vista you need to use the 2.1 Release Candidate (today RC9) http://openvpn.net/release/openvpn-2.1_rc9-install.exe to get it to work. Windows 2K/XP users can use the stable version http://openvpn.net/release/openvpn-2.0.9-install.exe
When the GUI has been installed you need to create a configuration file for your VPN tunnel. Create a file in "C:/Program Files/OpenVPN/config" called VPN.ovpn with the following content and where you change the vpn.yourdomain.com to match your configuration.
port 1194 dev tap remote vpn.yourdomain.com tls-client auth-user-pass ca ca.crt cert client.crt key client.key mtu-test tun-mtu 1500 tun-mtu-extra 32 mssfix 1450 pull comp-lzo verb 4
You now need to copy the Client keys you generated during the Server installation to the same directory on the Win2k/XP/Vista client. The following keys and certificates must be copied to the "C:/Program Files/OpenVPN/config" folder.
* ca.crt * client.crt * client.key
The Client installation is now complete and the user will be prompted upon login for the username and passwords.
FAQ
When running the OpenVPN Client on MS Vista it fails updating routes
You need to make sure you run the OpenVPN GUI as administrator. See this page on details how to do that http://www.howtogeek.com/howto/windows-vista/always-start-an-application-in-administrator-mode-on-windows-vista/