Wireguard

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Introduction

As of Linux 5.6 wireguard is included in the Linux kernel. Due to the use of Systemd, installation of the tools package will only be required on a single machines in order to generate keys.

Wireguard Installation

Install the wireguard-tools package on the machine that will manage the entire VPN.

# pikaur -S wireguard-tools

Key Generation

Each machine (server & client included) will need to have a private and public key generated for it.

# wg genkey | tee privatekey | wg pubkey > publickey

A preshared key is needed for each connection.

# wg genpsk > preshared-server-client

Server Setup

On the server (or internet facing machine) enable IP forwarding on boot.

# echo "net.ipv4.ip_forward=1" | sudo tee --append /etc/sysctl.d/50-security.conf

Enable IP forwarding currently as well.

# sudo sysctl -w net.ipv4.ip_forward=1

Systemd-Networkd

Create the wireguard interface for systemd-networkd. The example uses a single server and a single client, specific external ports on the server are being forwarded (via the wireguard network) to the client. Your IPs may vary, for this setup the 10.2.0.0/24 network is being used.

filename: /etc/systemd/network/wg0.netdev

[NetDev] Name=wg0 Kind=wireguard [WireGuard] ListenPort=51820 PrivateKey=<PRIVATE_KEY_SERVER> [WireGuardPeer] PublicKey=<PUBLIC_KEY_CLIENT1> PresharedKey=<PRESHARED_KEY_SERVER_CLIENT1> AllowedIPs=10.2.0.2/32

 

filename: /etc/systemd/networkd/wg0.network

[Match] Name=wg0 [Network] Address=10.2.0.1/32 [Route] Gateway=10.2.0.1 Destination=10.2.0.0/24

Since these files contain keys, you will not want other users viewing them.

# sudo chown root:systemd-network /etc/systemd/network/* # sudo chmod 640 /etc/systemd/network/*

Restart systemd-networkd in order to create the interface.

# sudo systemctl restart systemd-networkd

Nftables

With the WireGuard interface online and accepting connections the firewall needs to be addressed. Open up the configuration for editing.

# sudoedit /etc/nftables.conf

Add a line to the chain input for your ipv4 filter to accept udp connections.

# allow wireguard traffic udp dport 51820 accept