I wanted to setup OpenVPN with a VPS server so my laptop could have a secure connection when I’m traveling or at the library.
First off I downloaded Easyrsa3 from https://github.com/OpenVPN/easy-rsa and put it on a “controlled” computer, or “keyserver” as I’ll call it. The VPS isn’t totally under my control, and I didn’t want to have the main key on it. The keyserver doesn’t have to have internet or an connection to any of the other computers. But you will have to be able to transfer the files to and from the other computers.
You’ll want to edit the vars file with your own values. We using to have to load it into the system, (. ./vars) but we don’t do it that way anymore.
So on the keyserver, in the extracted easyrsa3 folder, you initiate the CA. This is your main keys and certificate files.
./easyrsa init-pki ./easyrsa build-ca
It will ask you for a password. I would recommend this for the CA key. If you want to not provide the password, add the argument “nopass” to the end of the command. And remember, you loose your password, you will have to rebuild it. There’s no way to get it back.
On all the computers I will tell it not to use a password, otherwise it will prompt for the password on each time OpenVPN starts.
Build the Keys
Now, there are two ways to build the keys and certificate for the server and clients. You can either generate the keys on the computers themselves or you can generate them on the keyserver and then move them over.
Generate on the computers themselves
To make the keys on the computers themselves, download the Easyrsa3 onto the computer, and run this:
For a server or client:
./easyrsa init-pki ./easyrsa gen-req <client-name>
Then copy the result
./easyrsa import-req /path/to/request.req <client-name> ./easyrsa sign-req [server|client] <client-name>
Make sure you specify if it’s a ‘server’ or a ‘client’. Then copy the
You can verify certs using:
openssl verify -CAfile ca.crt <client-name>.crt
or Generate keys on the keyserver then move
This way is simpler. But less secure.
For the server, do this:
./easyrsa build-server-full server nopass
For each client do this:
./easyrsa build-client-full <Client Name> nopass
Then copy over the needed keys and crt files.
This is what gives the server some extra encryption data. You can do this on the keyserver and move it over, or you can generate it on the server if you have the Easyrsa3 on it:
Then put it in the /etc/openvpn folder.
As a side note, the nice things about using a CA setup is if you ever loose a computer or otherwise need to keep one key from being able to access your VPN network, use (on keyserver):
./easyrsa revoke <Client Name>
Then run this:
And copy the output to the server. No need to copy to the clients.
Now to the actual meat of it. Install OpenVPN, and put the following files in it:
You’ll put this in the openvpn config:
Make sure these keys are owned by root and with the perms 600 or 400.
TA key for more security
For extra security you can generate a ta.key:
openvpn --genkey --secret ta.key
And add it to the config as (the ‘1’ is for clients, set to ‘0’ on the server): tls-auth keys/ta.key 1
This file can help on (D)DOS attacks and brute force attacks, as the server won’t even respond if it’s not provided.
Other config items
For extra security, run openvpn without privledges.
user nobody group nobody # make sure this group exists persist-key persist-tun nobind
Use udp for faster connections and keep on trying:
proto udp resolv-retry infinite keepalive 10 120
Use better encryption
tls-client # or tls-server on the server cipher AES-256-CBC # Use 'openvpn --show-ciphers' and 'openvpn --show-tls' remote-cert-tls server # checks the server's cert, to protect against man-in-the-middle attacks
Routing the Traffic
Now that OpenVPN is installed, we configure it to send all the internet traffic to it.
There’s two ways to do this. The simplest way is to have the server push everything to it.
push "redirect-gateway def1" push "remote-gateway <vpn server ip>" push "dhcp-option DNS <vpn server ip>"
Or you can add this to each client:
redirect-gateway def1 route 10.172.172.1 gateway
Either of these will create a route on the client that will make the traffic go to the server. But we have to tell the server what to do with it. So we add a iptables firewall to redirect the traffic:
iptables -I FORWARD -i tun+ -o eth0 \ -s 10.x.x.0/24 -m conntrack --ctstate NEW -j ACCEPT iptables -I FORWARD -m conntrack --ctstate RELATED,ESTABLISHED \ -j ACCEPT iptables -t nat -I POSTROUTING -o eth0 \ -s 10.x.x.0/24 -j MASQUERADE echo 1 > /proc/sys/net/ipv4/ip_forward
Now all the traffic should be working. Just note that DNS may still be going the regular way if you have something like ‘192.168.0.1’ in your /etc/resolv.conf file. You can change it to OpenDNS or Google so it’ll go through the vpn.
You can use OpenVPN’s scripting to set this if you’d like. Add this to the bottom of the OpenVPN config file:
script-security 2 up /etc/openvpn/up-script down "/usr/bin/sudo /etc/openvpn/down-script"
These are just example files. I use dnsmasq to cache dns lookups, which talks to the dns caching server on the vpn, so I just pipe it there. You’ll notice that I had to use sudo on it as OpenVPN runs as nobody and can’t change the file without sudo.
#!/bin/bash echo nameserver [vpn server ip] > /etc/resolv.dnsmasq.conf
#!/bin/bash echo "# OpenDNS IPv4 and IPv6 nameservers nameserver 184.108.40.206 nameserver 2620:0:ccc::2 nameserver 220.127.116.11 nameserver 2620:0:ccd::2 nameserver 18.104.22.168 nameserver 22.214.171.124" > /etc/resolv.dnsmasq.conf exit 0
Verify Certs forums.openvpn.net/topic8258.html (broken link)
tls-version-min 1.2 # haven't tried this, as some clients can't use it.