Writing an authentication plugin

An authentication plugin allows you to add a new way to allow users to log in to your pretalx instance. This can be useful if you want to integrate with an existing user database, or if you want to use a different authentication method.

In this document, we will walk through the creation of an authentication plugin step by step.

If you’d like to look at a completed working authentication provider, take a look at pretalx-social-auth, which also provides a framework for adding custom OAuth2 providers.

Please read Creating a plugin first, if you haven’t already.

Authentication registration

The Pretalx auth plugin system is based around Django’s authentication backends, with a couple of signals to integrate with the Pretalx interface.

First, follow Django’s documentation on writing an authentication backend, which must have the methods get_user(user_id) and authenticate(request, **credentials).

To add your the backend to Pretalx, it needs to be added authentication section of the pretalx.cfg file, in addition to the standard plugin registration e.g.:

[authentication]
additional_auth_backends=my_auth_plugin.auth.MyAuthBackend

[project.entry-points."pretalx.plugin"]
my_auth_plugin = "my_auth_plugin:PretalxPluginMeta"

The main signal used for authentication plugins (that require visiting a custom view) is the pretalx.common.signals.auth_html signal. This adds additional HTML to the login page, for example to add a login link to your custom authentication method. It also provides a next_url parameter, which is the path the user should be redirected to after logging in.:

from django.dispatch import receiver
from django.utils.safestring import mark_safe

from pretalx.common.signals import auth_html

@receiver(auth_html)
def render_login_auth_options(sender, request, next_url=None, **kwargs):
   login_url = reverse("plugins:my_auth_plugin:do_login")
   if next_url:
       login_url = f"{login_url}?next={next_url}"

   button = mark_safe(f"<a class="btn btn-lg btn-info btn-block" href="{login_url}">Sign in with Plugin</a>)
   return button

The do_login view should be implemented in your plugin, and should handle the actual authentication process.

Most authentication plugins will store data against a user in the Pretalx database (e.g. third-party ID), so you will need to create a model to store this data. To ensure this is removed when the user is deleted, your plugin should listen for the delete_user signal and remove any associated data for the user parameter.:

from django.dispatch import receiver

from pretalx.common.signals import delete_user

@receiver(delete_user)
def delete_user_data(sender, user, **kwargs):
   MyModel.objects.filter(user=user).delete()