Sometimes it can be useful to be able to connect back to your home network to access some internal resources. I’ll share how I set up a WireGuard server on OpenWRT.

First install some WireGuard packages.

$ opkg update
$ opkg install kmod-wireguard luci-app-wireguard luci-proto-wireguard wireguard wireguard-tools

Next go to https://openwrt/cgi-bin/luci/admin/network/iface_add, name the VPN interface wg0, select WireGuard VPN for Protocol of the new interface and press submit.

We need to generate some keypairs for the server and clients. Make sure to keep them safe.

$ mkdir -p /etc/wireguard
$ wg genkey | tee /etc/wireguard/server-privatekey | wg pubkey > /etc/wireguard/server-publickey
$ wg genkey | tee client-privatekey | wg pubkey > client-publickey

Head to the configuration page of wg0 interface (https://openwrt/cgi-bin/luci/admin/network/network/wg0). In General Setup tab, paste the content of /etc/wireguard/server-privatekey into Private Key. You can change Listen Port to any unused port you like. In IP Addresses, choose a subnet IP CIDR, for example 10.200.200.1/24. This will be the subnet of the VPN.

Next, let’s configure some peers. Some backgrounds here. First, WireGuard does not have the concept of server/client, instead, every WireGuard device is regarded as a peer to each other. Before establishing a successful connection, a proper config setup on both side is required.

Add a peer using the Add button. The peer we’re configuring here will be the “client”. In * Public Key*, paste the content of /etc/wireguard/client-publickey. In Allowed IPs, enter a random IP address in the subnet you previously chose, for example 10.200.200.2/24. This will be the client’s internal IP address.

Next, make sure Route Allowed IPs is checked. You most likely won’t need to configure Endpoint Host and Endpoint Port as we will be manually connecting to the OpenWRT WireGuard device on the client, instead of having OpenWRT aggressively establishing a connection. Put the recommended value 25 into Persistent Keep Alive.

In Firewall Settings tab, assign lan zone for the interface.

Hit Save & Apply.

Next run the following to make a new Traffic Rule in OpenWRT firewall. Make sure to change 99999 to your previously chosen port for WireGuard interface.

uci add firewall rule
uci set [email protected][-1].src="*"
uci set [email protected][-1].target="ACCEPT"
uci set [email protected][-1].proto="udp"
uci set [email protected][-1].dest_port="99999"
uci set [email protected][-1].name="Allow-Wireguard-Inbound"
uci commit firewall
/etc/init.d/firewall restart

The router side is done, I’ll demonstrate how to set up WireGuard on iOS. Download WireGuard app at https://itunes.apple.com/us/app/wireguard/id1441195209?mt=8. Open the app, press the + button on the top-right side and choose Create from scratch. Put any name you like on the Name field. Paste the keypairs of the client into their respective fields. In Addresses, put the exact same of what you specified in Allowed IPs of the client peer, e.g. 10.200.200.2/24. In DNS servers, put the router’s LAN IP address in. Don’t touch Listen port and MTU unless you know what you’re doing.

Add a new peer down below, and paste the server’s public key into Public key. Leave Preshared key field empty. In Endpoint, specify the router’s IP address or a domain name, ending with :port. For example vpn.foobar.dev:1234. Put 0.0.0.0/0 into Allowed IPs. Leave the rest default and hit save. Connect to the server and you should be able to access your home’s internal network on the public Internet.