Django app for City of Helsinki user infrastructure

Django-helusers is your friendly app for bolting authentication into Django projects for City of Helsinki. Authentication schemes are based on OAuth2 and OpenID Connect (OIDC).

A baseline User model is provided that can be used with the various authentication use cases that are supported. The model supports mapping from AD groups to Django groups based on the authentication data.

Additionally, there are optional functionalities that can be used as needed.

Functionalities for server needing (API) access token verification:

• For servers using Django REST Framework
• For servers not using Django REST Framework

Functionalities for server needing to authenticate against OIDC or OAuth2 server:

• support Django session login against OIDC or OAuth2 server, including Helsinki Tunnistus service and Azure AD
• augmented login template for Django admin, adding OIDC/OAuth2 login button

Adding django-helusers your Django project

Add django-helusers in your project's dependencies.

Some optional features of django-helusers have additional dependencies. These are mentioned in their relevant sections.

Adding django-helusers Django apps

Django-helusers provides two Django apps: HelusersConfig provides the models and templates needed for helusers to work and HelusersAdminConfig reconfigures Django admin to work with helusers.

Before adding the apps, you will need to remove django.contrib.admin, as HelusersAdminConfig is implementation of same functionality. You will get django.core.exceptions.ImproperlyConfigured: Application labels aren't unique, duplicates: admin-error, if you forget this step.

Then proceed by adding these apps to your INSTALLED_APPS in settings.py:

INSTALLED_APPS = (
    'helusers.apps.HelusersConfig',
    'helusers.apps.HelusersAdminConfig',
    ...
)

Us usual with INSTALLED_APPS, ordering matters. HelusersConfig must come before HelusersAdminConfig and anything else providing admin templates. Unless, of course, you wish to override the admin templates provided here.

One possible gotcha is, if you've added custom views to admin without forwarding context from each_context to the your template. Helusers templates expect variables from each_context and will break if they are missing.

Adding user model

helusers provides a baseline user model adding fields for Helsinki specific information. As per Django best practice you should subclass this model to make future customization easier:

# users/models.py

from helusers.models import AbstractUser


class User(AbstractUser):
    pass

and reference it in settings.py:

# myproject/settings.py

AUTH_USER_MODEL = 'users.User'

Optional features

Django REST Framework API authentication using JWT

If you have a REST API implemented using Django REST Framework and you want to authorize access to your API using JWTs, then this might be useful to you.

API token authentication is a stateless authentication method, where every request is authenticated by checking the signature of the included JWT token. It still creates a persistent Django user, which is updated with the information from the token with every request.

• Include drf-oidc-auth in your project's dependencies.
• Configure REST framework to use the ApiTokenAuthentication class in settings.py:

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'helusers.oidc.ApiTokenAuthentication',
    ),
}

• Set your deployment-specific variables in local_settings.py, e.g.:

OIDC_API_TOKEN_AUTH = {
    # Audience that must be present in the token for the request to be
    # accepted. Value must be agreed between your SSO service and your
    # application instance. Essentially this allows your application to
    # know that the token in meant to be used with it.
    'AUDIENCE': 'https://api.hel.fi/auth/projects',
    # Who we trust to sign the tokens. The library will request the
    # public signature keys from standard locations below this URL
    'ISSUER': 'https://api.hel.fi/sso/openid'
    # The following can be used if you need certain OAuth2 scopes
    # for any functionality of the API. The request will be denied
    # if scopes starting with API_SCOPE_PREFIX are not present
    # in the token claims. Usually this is not needed, as checking
    # the audience is enough.
    'REQUIRE_API_SCOPE_FOR_AUTHENTICATION': True,
    'API_SCOPE_PREFIX': 'projects',
}

API authentication using JWT in any setup

If you want to authorize access to your API using JWTs, but you are not using Django REST Framework, then this might be useful to you.

API token authentication is a stateless authentication method, where every request is authenticated by checking the signature of the included JWT token. It still creates a persistent Django user, which is updated with the information from the token with every request.

Django-helusers contains a helusers.oidc.RequestJWTAuthentication class. It has a method called authenticate that takes a Django HttpRequest as an argument, looks for a JWT from that request and performs authentication. User of this class can use it in any way they need to perform authentication and/or authorization. Check the class documentation for more details.

Some settings are needed (and some are optional) that affect how the RequestJWTAuthentication class works.

OIDC_API_TOKEN_AUTH = {
    # Audience that must be present in the token for it to be
    # accepted. Value must be agreed between your SSO service and your
    # application instance. Essentially this allows your application to
    # know that the token is meant to be used with it.
    # RequestJWTAuthentication supports multiple acceptable audiences,
    # so this setting can also be a list of strings.
    # This setting is required.
    'AUDIENCE': 'https://api.hel.fi/auth/projects',

    # Who we trust to sign the tokens. The library will request the
    # public signature keys from standard locations below this URL.
    # RequestJWTAuthentication supports multiple issuers, so this
    # setting can also be a list of strings.
    # Default is https://tunnistamo.hel.fi.
    'ISSUER': 'https://api.hel.fi/sso/openid'

    # The following can be used if you need certain scopes for any
    # functionality of the API. Usually this is not needed, as checking
    # the audience is enough. Default is False.
    'REQUIRE_API_SCOPE_FOR_AUTHENTICATION': True,
    # The name of the claim that is used to read in the scopes from the JWT.
    # Default is https://api.hel.fi/auth.
    'API_AUTHORIZATION_FIELD': 'scope_field',
    # The request will be denied if scopes don't contain anything starting
    # with the value provided here.
    'API_SCOPE_PREFIX': 'projects',

    # In order to do the authentication RequestJWTAuthentication needs
    # some facts from the authorization server, mainly its public keys for
    # verifying the JWT's signature. This setting controls the time how long
    # authorization server configuration and public keys are "remembered".
    # The value is in seconds. Default is 24 hours.
    'OIDC_CONFIG_EXPIRATION_TIME': 600,
}

OIDC back channel logout endpoint

Django-helusers provides an OIDC back channel logout endpoint implementation.

By default the OIDC back channel logout endpoint is disabled. You can enable it in your project's settings:

# myproject/settings.py
HELUSERS_BACK_CHANNEL_LOGOUT_ENABLED = True

# These settings specify which authentication server(s) are trusted
# to send back channel logout requests.
OIDC_API_TOKEN_AUTH = {
    # Who we trust to sign the logout tokens. The library will request
    # the public signature keys from standard locations below this URL.
    # Multiple issuers are supported, so this setting can also be a list
    # of strings. Default is https://tunnistamo.hel.fi.
    'ISSUER': 'https://api.hel.fi/sso/openid'

    # Audience that must be present in the logout token for it to
    # be accepted. Value must be agreed between your SSO service
    # and your application instance. Essentially this allows your
    # application to know that the token is meant to be used with
    # it. Multiple acceptable audiences are supported, so this
    # setting can also be a list of strings. This setting is required.
    'AUDIENCE': 'https://api.hel.fi/auth/projects',
}

You will also need to add Django-helusers URLs to your URL dispatcher configuration:

# myproject/urls.py
urlpatterns = [
    ...
    # You can adjust the prefix as you want
    path('helauth/', include('helusers.urls')),
    ...
]

With these settings your project now provides an endpoint at https://<your-domain>/helauth/logout/oidc/backchannel/ that responds to the OIDC back channel logout requests.

When the endpoint receives a valid request, it stores information about the logout event to the database. This information is used when authentication for other requests is performed. The helusers.oidc.RequestJWTAuthentication class that performs authentication based on a JWT bearer token, checks if the token's session has been terminated (by a logout event), and if that's the case, it doesn't authenticate the caller.

Logout event callback

The project using the OIDC back channel logout functionality has an option to attach a callback into the logout event handler. This is done by telling Django-helusers where this callback is located. Configure it in your project's settings:

# myproject/settings.py
HELUSERS_BACK_CHANNEL_LOGOUT_CALLBACK = "myproject.utils.logout_callback"

When a valid logout event is received, the callback is called. The callback receives two keyword arguments:

• request: the HttpRequest object describing the request to the logout endpoint
• jwt: a helusers.jwt.JWT instance of the logout token

The callback can affect the result of the back channel logout event handling by returning an HttpResponse instance with a status code between 400 and 599 inclusive. If such a response object is returned by the callback, the logout event handling is terminated and the response is sent to the requester. Any other kind of return value from the callback is ignored.

Adding Tunnistamo authentication

django-helusers ships with backend for authenticating against Tunnistamo using OIDC. Configuring this includes a Tunnistamo login button to the admin login screen.

There is also a deprecated legacy OAuth2 backend using allauth framework.

Include social-auth-app-django in your project's dependencies.

Add social_django into your INSTALLED_APPS setting:

# myproject/settings.py
INSTALLED_APPS = (
    ...
    'social_django',
    ...
)

Typically you would want to support authenticating using both OIDC and local database tables. Local users are useful for initial django admin login, before you've delegated permissions to users coming through OIDC.

Add backend configuration to your settings.py:

AUTHENTICATION_BACKENDS = [
    'helusers.tunnistamo_oidc.TunnistamoOIDCAuth',
    'django.contrib.auth.backends.ModelBackend',
]
LOGIN_REDIRECT_URL = '/'
LOGOUT_REDIRECT_URL = '/'

LOGIN_REDIRECT_URL is the default landing URL after succesful login, if your form did not specify anything else.

LOGOUT_REDIRECT_URL is the same for logout. django-helusers requires this to be set.

You will also need to add URLs for social_django & helusers to your URL dispatcher configuration (urls.py):

urlpatterns = [
    ...
    path('pysocial/', include('social_django.urls', namespace='social')),
    path('helauth/', include('helusers.urls')),
    ...
]

You can change the paths if they conflict with your application.

Finally, you will need to configure your SESSION_SERIALIZER. helusers stores the access token expiration time as a datetime which is not serializable to JSON, so Django needs to be configured to use the built-in PickleSerializer:

SESSION_SERIALIZER = 'django.contrib.sessions.serializers.PickleSerializer'

Django session login

Django session login is the usual login to Django that sets up a session and is typically implemented using a browser cookie. This is usually done using form with username & password fields. Django-helusers adds another path that delegates the login to an OIDC provider. User logs in at the provider and, upon successful return, a Django session is created for them. For us, the main use case has been allowing logins to Django admin.

To support session login Django-helusers needs three settings that must be configured both at Helsinki OIDC provider and your project instance. The settings are:

• client ID
• client secret
• Tunnistamo OIDC endpoint

Client is OAuth2 / OIDC name for anything wanting to authenticate users. Thus your application would be a client

Additionally you will need to provide your "callback URL" to the folks configuring Tunnistamo. This is implemented by python-social-auth and will, by default, be https://app.domain/auth/complete/tunnistamo/. During development on your own laptop your app.domain would be localhost.

After you've received your client ID, client secret and Tunnistamo OIDC endpoint you would configure them as follows:

SOCIAL_AUTH_TUNNISTAMO_KEY = 'https://i/am/clientid/in/url/style'
SOCIAL_AUTH_TUNNISTAMO_SECRET = 'iamyoursecret'
SOCIAL_AUTH_TUNNISTAMO_OIDC_ENDPOINT = 'https://tunnistamo.example.com/'

Note that client ID becomes KEY and client secret becomes SECRET.

Active Directory groups

Helusers can sync users AD groups to local Django groups when using an AD login method in Tunnistamo. To enable groups sync you should add "ad_groups" scope to the Tunnistamo OIDC authorize call. It can be done by adding the following to the settings:

SOCIAL_AUTH_TUNNISTAMO_SCOPE = 'ad_groups'

That setting will add "ad_groups" scope to the default social auth scopes "openid profile email". If you would like to modify the default social auth scopes you can set all of the scopes in the SOCIAL_AUTH_TUNNISTAMO_SCOPE setting and set SOCIAL_AUTH_TUNNISTAMO_IGNORE_DEFAULT_SCOPE to True.

Additionally, the client in Tunnistamo should be configured with AD groups enabled.

When the users returns from Tunnistamo with "ad_groups" claim set Helusers will add all of the groups as an instance of ADGroup model to the database.

Then, Helusers will add any missing ADGroups to the users' ad_groups-relation and remove any ADGroups the user is not a member of anymore.

To use groups in Django permissions, you should use the Django admin view (HELSINKI USERS > AD Group Mappings) to set mappings between ADGroups and Groups. Helusers will then add the user to Django groups that are mapped to their AD Groups.

Note that after creating mappings you cannot manually add a user to a mapped group if they are not a member of the corresponding AD group because the group will be removed the next time the user logs in.

Adding tunnistamo URL to template context

If you need to access the Tunnistamo API from your JS code, you can include the Tunnistamo base URL in your template context using helusers's context processor:

TEMPLATES = [
    {
        'OPTIONS': {
            'context_processors': [
                'helusers.context_processors.settings'
            ]
        }
    }
]

Carrying language preference from your application to Tunnistamo

Tunnistamo (per the OIDC specs) allows clients to specify the language used for the login process. This allows you to carry your applications language setting to the login screens presented by Tunnistamo.

Configure python-social-auth to pass the necessary argument through its login view:

SOCIAL_AUTH_TUNNISTAMO_AUTH_EXTRA_ARGUMENTS = {'ui_locales': 'fi'}

fi there is the language code that will be used when no language is requested, so change it if you you prefer some other default language. If you don't want to set a default language at all, use an empty string "" as the language code.

When this setting is in place, languages can be requested using query param ui_locales=<language code> when starting the login process, for example in your template

<a href="{% url 'helusers:auth_login' %}?next=/foobar/&ui_locales=en">Login in English</a>

Disabling password logins

If you're not allowing users to log in with passwords, you may disable the username/password form from Django admin login page by setting HELUSERS_PASSWORD_LOGIN_DISABLED to True.

Development

Virtual Python environment can be used. For example:

python3 -m venv .venv
source .venv/bin/activate

Install package requirements:

pip install -e .

Install development requirements:

pip install -r requirements-test.txt

Running tests

pytest

You can run the tests against multiple environments by using tox. Install tox globally and run:

tox