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Global Socket WireGuard Example

Connect two firewalled hosts with wireGuard (Virtual Private Network)

Problem
ALICE and BOB are on two different networks behind NAT/Firewall. Neither of them can reach the other. A WireGuard VPN can not be established (ALICE and BOB are both firewalled).

Objective
Create a WireGuard Virtual Private Network between ALICE and BOB (without tampering with the firewall, NAT or router settings).

Solution
Redirect the WireGuard traffic via the Global Socket Relay Network.

ALICE -> WireGuard -> Global Socket Relay Network -> WireGuard -> BOB

On workstation "ALICE":

a@ALICE:~ $ wg-quick up ./wg0-server.conf

On workstation "BOB":

b@BOB:~ $ wg-quick up ./wg0-client.conf

Test the WireGuard VPN:

b@BOB:~ $ ping 10.37.0.1
PING 10.37.0.1 (10.37.0.1) 56(84) bytes of data.
64 bytes from 10.37.0.1: icmp_seq=1 ttl=64 time=46.96 ms
[...]

Explanation

Let's take a look at wg-server.conf (ALICE)

[Interface]
# Server
Address = 10.37.0.1/24
ListenPort = 51820
PrivateKey = 4E48vR7v8OUJO5OEYkOUUZmF55UOYVqo9l9w2eRS50k=
PostUp = sysctl -w net.ipv4.ip_forward=1
PreUp = gs-netcat -s ExampleSecretChangeMe -Culq -d 127.0.0.1 -p 51820 &
PostDOwn = killall -g gs-netcat

[Peer]
# Client #1
PublicKey = KRYz7Jsbu1pS6ALHLqCUqG4KsFh9GcK3II+3bFscYUU=
AllowedIPs = 10.37.0.2/32

This is a default WireGuard configuration file for a server. The only change is:

PreUp = gs-netcat -s ExampleSecretChangeMe -Culq -d 127.0.0.1 -p 51820 &

This starts a gs-netcat process and redirects any traffic from the Global Socket ExampleSecretChangeMe to the default WireGuard port (51820). -u specifies UDP protocol and -q to be quiet.

Let's take a look at wg-client.conf (BOB):

[Interface]
# client. ME
Address = 10.37.0.2/32
PrivateKey = SOnUcf+KuXIWXfhpZpHtTC097ihBNUXT2igp5IuJsWY=
# Make gs-netcat listen on UDP 31337
PreUp = gs-netcat -s ExampleSecretChangeMe -Cuq -p 31337 &
PostDown = killall -g gs-netcat

[Peer]
# server
Endpoint = 127.0.0.1:31337
PublicKey = gjBE/V1pGdIu7yTGWtZvObxIf9+ErH9aRP+jsBuiXC4=
AllowedIPs = 10.37.0.0/24
PersistentKeepalive = 25

The only change is:

PreUp = gs-netcat -s ExampleSecretChangeMe -Cuq -p 31337 &
[...]
EndPoint = 127.0.0.1:31337

The PreUp-line redirects any UDP traffic from port 31337 to the Global Socket ExampleSecretChangeMe. The new Endpoint instructs WireGuard to send all WireGuard traffic to the UDP port where gs-netcat is listening (31337). Any UDP traffic received by gs-netcat is forwarded (via the Global Socket Relay Network) to the other gs-netcat running on ALICE.

Notes
The gs-netcat secret ExampleSecretChangeMe is chosen at random but has to be identical on ALICE and BOB. This string is used by the Global Socket Relay Network to connect ALICE and BOB. Use gs-netcat -g to generate a new random string for your own use (do not use the example).

Create your own private/public WireGuard keys (do not use the example):

$ wg genkey | tee server-privatekey | wg pubkey > server-publickey
$ wg genkey | tee client-privatekey | wg pubkey > client-publickey

Many more gs-netcat options are available: For example -T to connect WireGuard via TOR or -L for log-output. See the manual page for gs-netcat.