Headscale

An open source, self-hosted implementation of the Tailscale coordination server.

Overview

Tailscale is a modern VPN built on top of Wireguard. It works like an overlay network between the computers of your networks - using all kinds of NAT traversal sorcery.

Everything in Tailscale is Open Source, except the GUI clients for proprietary OS (Windows and macOS/iOS), and the 'coordination/control server'.

The control server works as an exchange point of Wireguard public keys for the nodes in the Tailscale network. It also assigns the IP addresses of the clients, creates the boundaries between each user, enables sharing machines between users, and exposes the advertised routes of your nodes.

Headscale implements this coordination server.

Status

• Base functionality (nodes can communicate with each other)
• Node registration through the web flow
• Network changes are relied to the nodes
• Namespace support (~equivalent to multi-user in Tailscale.com)
• Routing (advertise & accept, including exit nodes)
• Node registration via pre-auth keys (including reusable keys, and ephemeral node support)
• JSON-formatted output
• ACLs
• Share nodes between users namespaces
• DNS

Roadmap 🤷

We are now focusing on adding integration tests with the official clients.

Suggestions/PRs welcomed!

Running it

1. Download the Headscale binary https://github.com/juanfont/headscale/releases, and place it somewhere in your PATH

2. (Optional, you can also use SQLite) Get yourself a PostgreSQL DB running

docker run --name headscale -e POSTGRES_DB=headscale -e \
  POSTGRES_USER=foo -e POSTGRES_PASSWORD=bar -p 5432:5432 -d postgres

3. Set some stuff up (headscale Wireguard keys & the config.json file)

wg genkey > private.key
wg pubkey < private.key > public.key  # not needed

# Postgres
cp config.json.postgres.example config.json
# or
# SQLite
cp config.json.sqlite.example config.json

4. Create a namespace (a namespace is a 'tailnet', a group of Tailscale nodes that can talk to each other)

headscale namespaces create myfirstnamespace

5. Run the server

headscale serve

6. If you used tailscale.com before in your nodes, make sure you clear the tailscaled data folder

systemctl stop tailscaled
rm -fr /var/lib/tailscale
systemctl start tailscaled 

7. Add your first machine

tailscale up -login-server YOUR_HEADSCALE_URL

8. Navigate to the URL you will get with tailscale up, where you'll find your machine key.

9. In the server, register your machine to a namespace with the CLI

headscale -n myfirstnamespace node register YOURMACHINEKEY

Alternatively, you can use Auth Keys to register your machines:

1. Create an authkey

   headscale -n myfirstnamespace preauthkeys create --reusable --expiration 24h
   

2. Use the authkey from your machine to register it

   tailscale up -login-server YOUR_HEADSCALE_URL --authkey YOURAUTHKEY
   

If you create an authkey with the --ephemeral flag, that key will create ephemeral nodes. This implies that --reusable is true.

Please bear in mind that all the commands from headscale support adding -o json or -o json-line to get a nicely JSON-formatted output.

Configuration reference

Headscale's configuration file is named config.json or config.yaml. Headscale will look for it in /etc/headscale, ~/.headscale and finally the directory from where the Headscale binary is executed.

    "server_url": "http://192.168.1.12:8080",
    "listen_addr": "0.0.0.0:8080",
    "ip_prefix": "100.64.0.0/10"

server_url is the external URL via which Headscale is reachable. listen_addr is the IP address and port the Headscale program should listen on. ip_prefix is the IP prefix (range) in which IP addresses for nodes will be allocated.

    "private_key_path": "private.key",

private_key_path is the path to the Wireguard private key. If the path is relative, it will be interpreted as relative to the directory the configuration file was read from.

    "derp_map_path": "derp.yaml",

derp_map_path is the path to the DERP map file. If the path is relative, it will be interpreted as relative to the directory the configuration file was read from.

    "ephemeral_node_inactivity_timeout": "30m",

ephemeral_node_inactivity_timeout is the timeout after which inactive ephemeral node records will be deleted from the database. The default is 30 minutes. This value must be higher than 65 seconds (the keepalive timeout for the HTTP long poll is 60 seconds, plus a few seconds to avoid race conditions).

    "db_host": "localhost",
    "db_port": 5432,
    "db_name": "headscale",
    "db_user": "foo",
    "db_pass": "bar",

The fields starting with db_ are used for the PostgreSQL connection information.

Running the service via TLS (optional)

    "tls_cert_path": ""
    "tls_key_path": ""

Headscale can be configured to expose its web service via TLS. To configure the certificate and key file manually, set the tls_cert_path and tls_cert_path configuration parameters. If the path is relative, it will be interpreted as relative to the directory the configuration file was read from.

    "tls_letsencrypt_hostname": "",
    "tls_letsencrypt_listen": ":http",
    "tls_letsencrypt_cache_dir": ".cache",
    "tls_letsencrypt_challenge_type": "HTTP-01",

To get a certificate automatically via Let's Encrypt, set tls_letsencrypt_hostname to the desired certificate hostname. This name must resolve to the IP address(es) Headscale is reachable on (i.e., it must correspond to the server_url configuration parameter). The certificate and Let's Encrypt account credentials will be stored in the directory configured in tls_letsencrypt_cache_dir. If the path is relative, it will be interpreted as relative to the directory the configuration file was read from. The certificate will automatically be renewed as needed.

Challenge type HTTP-01

The default challenge type HTTP-01 requires that Headscale is reachable on port 80 for the Let's Encrypt automated validation, in addition to whatever port is configured in listen_addr. By default, Headscale listens on port 80 on all local IPs for Let's Encrypt automated validation.

If you need to change the ip and/or port used by Headscale for the Let's Encrypt validation process, set tls_letsencrypt_listen to the appropriate value. This can be handy if you are running Headscale as a non-root user (or can't run setcap). Keep in mind, however, that Let's Encrypt will only connect to port 80 for the validation callback, so if you change tls_letsencrypt_listen you will also need to configure something else (e.g. a firewall rule) to forward the traffic from port 80 to the ip:port combination specified in tls_letsencrypt_listen.

Challenge type TLS-ALPN-01

Alternatively, tls_letsencrypt_challenge_type can be set to TLS-ALPN-01. In this configuration, Headscale listens on the ip:port combination defined in listen_addr. Let's Encrypt will only connect to port 443 for the validation callback, so if listen_addr is not set to port 443, something else (e.g. a firewall rule) will be required to forward the traffic from port 443 to the ip:port combination specified in listen_addr.

Policy ACLs

Headscale implements the same policy ACLs as Tailscale.com, adapted to the self-hosted environment.

For instance, instead of referring to users when defining groups you must use namespaces (which are the equivalent to user/logins in Tailscale.com).

Please check https://tailscale.com/kb/1018/acls/, and ./tests/acls/ in this repo for working examples.

Disclaimer

1. We have nothing to do with Tailscale, or Tailscale Inc.
2. The purpose of writing this was to learn how Tailscale works.

More on Tailscale

• https://tailscale.com/blog/how-tailscale-works/
• https://tailscale.com/blog/tailscale-key-management/
• https://tailscale.com/blog/an-unlikely-database-migration/