Configuring Headscale to use OIDC authentication

In order to authenticate users through a centralized solution one must enable the OIDC integration.

Known limitations:

No dynamic ACL support
OIDC groups cannot be used in ACLs

Basic configuration

In your config.yaml, customize this to your liking:

oidc:
  # Block further startup until the OIDC provider is healthy and available
  only_start_if_oidc_is_available: true
  # Specified by your OIDC provider
  issuer: "https://your-oidc.issuer.com/path"
  # Specified/generated by your OIDC provider
  client_id: "your-oidc-client-id"
  client_secret: "your-oidc-client-secret"
  # alternatively, set `client_secret_path` to read the secret from the file.
  # It resolves environment variables, making integration to systemd's
  # `LoadCredential` straightforward:
  #client_secret_path: "${CREDENTIALS_DIRECTORY}/oidc_client_secret"
  # If provided, the name of a custom OIDC claim for specifying user groups. 
  # The claim value is expected to be a string or array of strings.
  groups_claim: groups
  # The OIDC claim to use as the email.
  email_claim: email
  # The OIDC claim to use as the username.
  email_claim: preferred_username

  # Customize the scopes used in the OIDC flow, defaults to "openid", "profile" and "email" and add custom query
  # parameters to the Authorize Endpoint request. Scopes default to "openid", "profile" and "email".
  scope: ["openid", "profile", "email", "custom"]
  # Optional: Passed on to the browser login request – used to tweak behaviour for the OIDC provider
  extra_params:
    domain_hint: example.com

  # Optional: List allowed principal domains and/or users. If an authenticated user's domain is not in this list,
  # the authentication request will be rejected.
  allowed_domains:
    - example.com
  # Optional. Note that groups from Keycloak have a leading '/'.
  allowed_groups:
    - /headscale
  # Optional.
  allowed_users:
    - alice@example.com

  # By default, Headscale will use the OIDC email address claim to determine the username.
  # OIDC also returns a `preferred_username` claim.
  #
  # If `use_username_claim` is set to `true`, then the `preferred_username` claim will
  # be used instead to set the Headscale username.
  # If `use_username_claim` is set to `false`, then the `email` claim will be used
  # to derive the Headscale username (as modified by the `strip_email_domain` entry).

  use_username_claim: false

  # If `strip_email_domain` is set to `true`, the domain part of the username email address will be removed.
  # This will transform `first-name.last-name@example.com` to the user `first-name.last-name`
  # If `strip_email_domain` is set to `false` the domain part will NOT be removed resulting to the following
  # user: `first-name.last-name.example.com`
  strip_email_domain: true

Azure AD example

In order to integrate Headscale with Azure Active Directory, we'll need to provision an App Registration with the correct scopes and redirect URI. Here with Terraform:

resource "azuread_application" "headscale" {
  display_name = "Headscale"

  sign_in_audience = "AzureADMyOrg"
  fallback_public_client_enabled = false

  required_resource_access {
    // Microsoft Graph
    resource_app_id = "00000003-0000-0000-c000-000000000000"

    resource_access {
      // scope: profile
      id   = "14dad69e-099b-42c9-810b-d002981feec1"
      type = "Scope"
    }
    resource_access {
      // scope: openid
      id   = "37f7f235-527c-4136-accd-4a02d197296e"
      type = "Scope"
    }
    resource_access {
      // scope: email
      id   = "64a6cdd6-aab1-4aaf-94b8-3cc8405e90d0"
      type = "Scope"
    }
  }
  web {
    # Points at your running Headscale instance
    redirect_uris = ["https://headscale.example.com/oidc/callback"]

    implicit_grant {
      access_token_issuance_enabled = false
      id_token_issuance_enabled = true
    }
  }

  group_membership_claims = ["SecurityGroup"]
  optional_claims {
    # Expose group memberships
    id_token {
      name = "groups"
    }
  }
}

resource "azuread_application_password" "headscale-application-secret" {
  display_name          = "Headscale Server"
  application_object_id = azuread_application.headscale.object_id
}

resource "azuread_service_principal" "headscale" {
  application_id = azuread_application.headscale.application_id
}

resource "azuread_service_principal_password" "headscale" {
  service_principal_id = azuread_service_principal.headscale.id
  end_date_relative    = "44640h"
}

output "headscale_client_id" {
  value = azuread_application.headscale.application_id
}

output "headscale_client_secret" {
  value = azuread_application_password.headscale-application-secret.value
}

And in your Headscale config.yaml:

oidc:
  issuer: "https://login.microsoftonline.com/<tenant-UUID>/v2.0"
  client_id: "<client-id-from-terraform>"
  client_secret: "<client-secret-from-terraform>"

  # Optional: add "groups"
  scope: ["openid", "profile", "email"]
  extra_params:
    # Use your own domain, associated with Azure AD
    domain_hint: example.com
    # Optional: Force the Azure AD account picker
    prompt: select_account

Google OAuth Example

In order to integrate Headscale with Google, you'll need to have a Google Cloud Console account.

Google OAuth has a verification process if you need to have users authenticate who are outside of your domain. If you only need to authenticate users from your domain name (ie @example.com), you don't need to go through the verification process.

However if you don't have a domain, or need to add users outside of your domain, you can manually add emails via Google Console.

Steps

Go to Google Console and login or create an account if you don't have one.
Create a project (if you don't already have one).
On the left hand menu, go to APIs and services -> Credentials
Click Create Credentials -> OAuth client ID
Under Application Type, choose Web Application
For Name, enter whatever you like
Under Authorised redirect URIs, use https://example.com/oidc/callback, replacing example.com with your Headscale URL.
Click Save at the bottom of the form
Take note of the Client ID and Client secret, you can also download it for reference if you need it.
Edit your headscale config, under oidc, filling in your client_id and client_secret:

oidc:
  issuer: "https://accounts.google.com"
  client_id: ""
  client_secret: ""
  scope: ["openid", "profile", "email"]

You can also use allowed_domains and allowed_users to restrict the users who can authenticate.

Authelia Example

In order to integrate Headscale with your Authelia instance, you need to generate a client secret add your Headscale instance as a client.

First, generate a client secret. If you are running Authelia inside docker, prepend docker-compose exec <authelia_container_name> before these commands:

authelia crypto hash generate pbkdf2 --variant sha512 --random --random.length 72

This will return two strings, a "Random Password" which you will fill into Headscale, and a "Digest" you will fill into Authelia.

In your Authelia configuration, add Headscale under the client section:

clients:
  - id: headscale
    description: Headscale
    secret: "DIGEST_STRING_FROM_ABOVE"
    public: false
    authorization_policy: two_factor
    redirect_uris:
      - https://your.headscale.domain/oidc/callback
    scopes:
      - openid
      - profile
      - email
      - groups

In your Headscale config.yaml, edit the config under oidc, filling in the client_id to match the id line in the Authelia config and filling in client_secret from the "Random Password" output. You may want to tune the expiry, only_start_if_oidc_available, and other entries. The following are only the required entries.

oidc:
  issuer: "https://your.authelia.domain"
  client_id: "headscale"
  client_secret: "RANDOM_PASSWORD_STRING_FROM_ABOVE"
  scope: ["openid", "profile", "email", "groups"]
  allowed_groups:
    - authelia_groups_you_want_to_limit

In particular, you may want to set use_username_claim: true to use Authelia's preferred_username grant to set Headscale usernames.

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