The OpenVPN client is great because it automatically reconnects when your iPhone wakes from sleep, do you don't have to manually reconnect.
So this is how to quickly setup your own OpenVPN server and hook up your iPhone.
How It Works
OpenVPN is an SSL-based VPN solution. SSL-based VPNs are cool because if you set it up properly, you will never be blocked by any firewall as long as TCP-port 443 is accessible. Standard, OpenVPN uses UDP as a transport at port 1194, but you can switch to TCP to increase the chance that your traffic will not be blocked.
Authentication is performed based on public/private key cryptography. The OpenVPN server is similar to an HTTPS server. The client however, does not authenticate with a username and password but you use a client certificate.
So before you can setup an actual VPN configuration with OpenVPN, you need to setup a Certificate Authority.
With the CA you can create the server certificate and then generate all client certificates for authentication. Clients use the CA certificate to validate the server.
OpenVPN is often standard on most common Linux Distros. apt-get install openvpn for any Debian or Ubuntu version is all you need to install OpenVPN.
Or take a look here
Creating a certificate authority.
I assume that you will create a configuration in /etc/openvpn. But before you can setup the configuration, you need to create a certificate authority. I used the folder /etc/openvpn/easy-rsa for this.
This is no coincidence, as we use the easy-rsa scripts as part of OpenVPN to quickly setup our certificate authority.
We start with copying all these files to this new directory:
cp -R /usr/share/doc/openvpn/examples/easy-rsa/2.0* /etc/openvpn/easy-rsa
Next, we cd to this directory and edit the 'vars' file. The following instructions are straight from the OpenVPN howto.
export KEY_COUNTRY="US" export KEY_PROVINCE="California" export KEY_CITY="San Fransisco" export KEY_ORG="My Company" export KEY_EMAIL="email@example.com" export KEY_CN=server export KEY_NAME=server export KEY_OU=home
Then I had to copy openssl-1.0.0.cnf to openssl.cnf because the 'vars' script complained that it couldn't find the latter file.
cp openssl-1.0.0.cnf openssl.cnf
Then we 'source' var and run two additional commands that actually generate the certificate authority.
. ./vars ./clean-all ./build-ca
You will have to confirm the values or change them if necessary.
Now we have a certificate authority and we can create new certificates that will be signed by this authority.
WARNING: be extremely careful with all key files, they should be kept private.
Creating the Server Certificate
First we create the server certificate:
It's up to you to come up with an alternative for 'server'. This is the file name under which the key files and certificates are stored.
All files that are generated can be found in the '/etc/openvpn/easy-rsa/keys' directory.
Creating the Client Certificate
Now that we have a server certificate, we are going to create a certificate for our iPhone (or any other iOS device).
Last, we must generate Diffie-Helman parameters like this:
So now we have everything in place to start creating an OpenVPN configuration. We must create a configuration for the server and the client. Those configurations are based on the examples that can be find in /usr/share/doc/openvpn/examples/.
Example Server configuration
This is my server configuration which is operational. It is stored in /etc/openvpn/iphone.conf
dev tun2 tls-server dh easy-rsa/keys/dh1024.pem ca easy-rsa/keys/ca.crt cert easy-rsa/keys/server.crt key easy-rsa/keys/server.key server 10.0.0.0 255.255.255.0 log /var/log/openvpn-iphone.log comp-lzo script-security 2 route-up "/sbin/ifconfig tun2 up" port 443 proto tcp-server keepalive 30 120 push "redirect-gateway def1 bypass-dhcp" push "dhcp-option DNS 188.8.131.52"
I use TCP-port 443 as this destination port is almost never blocked as this would break most internet connectivity. The downside is that I can no longer host any secure web site on this IP-address.
I'm aware that you now know that I'm running OpenVPN on this box and you will be able to talk to this service, however, as it uses certificates for authentication, security will be sufficient, unless OpenVPN itself is vulnerable.
The keepalive parameter prevents your phone from reconnecting every 40 seconds by default, as I experienced.
Change any parameters if required and then start or restart the OpenVPN service:
Make sure that the server is running properly in /var/log/openvpn-iphone.log
If you want to use your VPN to browse the internet, we still need to configure a basic firewall setup.
I'm assuming that you already have some kind of IPtables file wall running. If not, you might want to look at LIFS, a powerful Linux firewall script. So I assume that you already have a secure IPtables configuration, you only need to add some stuff.
Assuming that you will - for example - use the 10.0.0.0/24 network for VPN clients such as your iPhone, you must also create a NAT rule so VPN clients can use the IP-address of the Linux server to access Internet.
iptables -t nat -A POSTROUTING -s "10.0.0.0/24" -o "eth0" -j MASQUERADE
Please note that you must change eth0 with the appropriate interface of your router. Change the IP-address range according to your own situation. It should not conflict with your existing network.
iptables -A FORWARD -p tcp -s 10.0.0.0/24 -d 0.0.0.0/0 -j ACCEPT
Please note that I haven't tested these rules, as I have a different setup. But this should be sufficient. And make sure that forwarding is enabled like this:
echo 1 > /proc/sys/net/ipv4/ip_forward
Example Client configuration
Create a file called iphone.ovpn and configure it like this:
tls-client remote <some domain name or IP address> ca ca.crt cert iphone.crt key iphone.key comp-lzo port 443 proto tcp
Setting up your iPhone
You need to get the following files on your iOS device:
iphone.ovpn ca.crt iphone.crt iphone.key
The safest way is to use iTunes and connect your device with a cable, although I believe that iCloud stuff works too.
- Open iTunes
- Select your device at the top right
- Go to the Apps tab
- Scroll to the file sharing section
- Select the OpenVPN application
- Add all mentioned files at the right side
- Sync your device
Test your iPhone
Open the OpenVPN client. You will see a notice that a new configuration has been imported and you need to accept this configuration. As it might not work straight away, you need to monitor /var/log/openvpn-iphone.log on the server to watch for any errors.
Now try to connect and enjoy.
Updated 20130123 with keepalive option. Updated 20130801 with extra server push options for traffic redirection and DNS configuration