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WireGuard Key Exchange

wgkex is a WireGuard key exchange and management tool designed and run by FFMUC.

Overview

WireGuard Key Exchange is a tool consisting of two parts: a frontend (broker) and a backend (worker). These components communicate to each other via MQTT - a messaging bus.

graph TD;
	A{"client"} -->|"RESTful API"| G("WGKex Broker")
	G -->|"publish"| B("Mosquitto")
	C("WGKex Worker") -->|"Subscribe"| B
	C -->|"Route Injection"| D["netlink (pyroute2)"]
	C -->|"Peer Creation"| E["wireguard (pyroute2)"]
	C -->|"VxLAN FDB Entry"| F["VXLAN FDB (pyroute2)"]
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Frontend broker

The frontend broker is where the client can push (register) its key before connecting. These keys are then pushed into an MQTT bus for all workers to consume.

The frontend broker exposes the following API endpoints for use:

/api/v1/wg/key/exchange
/api/v2/wg/key/exchange

The listen address and port for the Flask server can be configured in wgkex.yaml under the broker_listen key:

broker_listen:
  # host defaults to 127.0.0.1 if unspecified
  host: 0.0.0.0
  # port defaults to 5000 if unspecified
  port: 5000

POST /api/v1/wg/key/exchange

JSON POST'd to this endpoint should be in this format:

{
  "domain": "CONFIGURED_DOMAIN",
  "public_key": "PUBLIC_KEY"
}

The broker will validate the domain and public key, and if valid, will push the key onto the MQTT bus.

POST /api/v2/wg/key/exchange

JSON POST'd to this endpoint should be in this format:

{
  "domain": "CONFIGURED_DOMAIN",
  "public_key": "PUBLIC_KEY"
}

The broker will validate the domain and public key, and if valid, will push the key onto the MQTT bus. Additionally it chooses a worker (aka gateway, endpoint) that the client should connect to. The response is JSON data containing the connection details for the chosen gateway:

{
  "Endpoint": {
    "Address": "GATEWAY_ADDRESS",
    "Port": "GATEWAY_WIREGUARD_PORT",
    "AllowedIPs": [
      "GATEWAY_WIREGUARD_INTERFACE_ADDRESS"
    ],
    "PublicKey": "GATEWAY_PUBLIC_KEY"
  }
}

Backend worker

The backend (worker) waits for new keys to appear on the MQTT message bus. Once a new key appears, the worker performs validation task on the key, then injects those keys into a WireGuard instance(While also updating the VxLAN FDB). It reports metrics like number of connected peers and instance data like local address, WG listening port and external domain name (configured in config.yml) back to the broker. Each worker must run on a machine with a unique hostname, as it is used for separation of metrics.

This tool is intended to facilitate running BATMAN over VXLAN over WireGuard as a means to create encrypted high-performance mesh links.

For further information, please see this presentation on the architecture

Installation

  • TBA

Configuration

  • Configuration file

The wgkex configuration file defaults to /etc/wgkex.yaml (Sample configuration file), however can also be overwritten by setting the environment variable WGKEX_CONFIG_FILE.

Running the broker and worker

Build using Bazel

Worker:

# defaults to /etc/wgkex.yaml if not set
export WGKEX_CONFIG_FILE=/opt/wgkex/wgkex.yaml
bazel build //wgkex/worker:app
# Artifact will now be placed into ./bazel-bin/wgkex/worker/app
./bazel-bin/wgkex/worker/app

Broker:

# defaults to /etc/wgkex.yaml if not set
export WGKEX_CONFIG_FILE=/opt/wgkex/wgkex.yaml
bazel build //wgkex/broker:app
# Artifact will now be placed into ./bazel-bin/wgkex/broker/app
./bazel-bin/wgkex/broker/app

Run using Python

Broker: (Using Flask development server)

FLASK_ENV=development FLASK_DEBUG=1 FLASK_APP=wgkex/broker/app.py python3 -m flask run

Worker:

python3 -c 'from wgkex.worker.app import main; main()'

Development

Unit tests

The test can be run using bazel test ... --test_output=all or python3 -m unittest discover -p '*_test.py'.

Client

The client can be used via CLI:

$ wget -q  -O- --post-data='{"domain": "ffmuc_welt","public_key": "o52Ge+Rpj4CUSitVag9mS7pSXUesNM0ESnvj/wwehkg="}'   --header='Content-Type:application/json'   'http://127.0.0.1:5000/api/v2/wg/key/exchange'
{
  "Endpoint": {
    "Address": "gw04.ext.ffmuc.net:40011",
    "LinkAddress": "fe80::27c:16ff:fec0:6c74",
    "PublicKey": "TszFS3oFRdhsJP3K0VOlklGMGYZy+oFCtlaghXJqW2g="
  },
  "Message": "OK"
}

Or via python:

import requests
key_data = {"domain": "ffmuc_welt","public_key": "o52Ge+Rpj4CUSitVag9mS7pSXUesNM0ESnvj/wwehkg="}
broker_url = "http://127.0.0.1:5000"
push_key = requests.get(f'{broker_url}/api/v2/wg/key/exchange', json=key_data)
print(f'Key push was: {push_key.json().get("Message")}')

Worker

You can set up dummy interfaces for the worker using this script:

interface_linklocal() {
  # We generate a predictable v6 address
  local macaddr="$(echo $1 | wg pubkey |md5sum|sed 's/^\(..\)\(..\)\(..\)\(..\)\(..\).*$/02:\1:\2:\3:\4:\5/')"
  local oldIFS="$IFS"; IFS=':'; set -- $macaddr; IFS="$oldIFS"
  echo "fe80::$1$2:$3ff:fe$4:$5$6"
}

sudo ip link add wg-welt type wireguard
wg genkey | sudo wg set wg-welt private-key /dev/stdin
sudo wg set wg-welt listen-port 51820
addr=$(interface_linklocal $(sudo wg show wg-welt private-key))
sudo ip addr add $addr dev wg-welt
sudo ip link add vx-welt type vxlan id 99 dstport 0 local $addr dev wg-welt
sudo ip addr add fe80::1/64 dev vx-welt
sudo ip link set wg-welt up
sudo ip link set vx-welt up

MQTT topics

  • Publishing keys broker->worker: wireguard/{domain}/{worker}
  • Publishing metrics worker->broker: wireguard-metrics/{domain}/{worker}/connected_peers
  • Publishing worker status: wireguard-worker/{worker}/status
  • Publishing worker data: wireguard-worker/{worker}/{domain}/data

Contact

Freifunk Munich Mattermost