Custom authentication backend. Django

Question

I would like to create an authentication backend that allows users to log_in only using their email (no username, no password).

Here is what I tried.

backends.py:

from django.conf import settings from django.contrib.auth.models import User class EmailAuthBackend(object): def authenticate(self, username=None, password=None): try: user = User.objects.get(email=username) if user: return user except User.DoesNotExist: return None

settings.py:

 AUTHENTICATION_BACKENDS = ( 'path_to.backends.EmailAuthBackend', 'django.contrib.auth.backends.ModelBackend', )

html:

 <form method="post" action="{% url myproject.views.test %}"> {% csrf_token %} <input type="text" name="email" value=""/> <button type="submit">Valider</button> </form>

view:

 def test(request): email = '' if 'email' in request.POST: email = request.POST.get('email') if not User.objects.filter(email=email): User.objects.create(email=email) user = authenticate(username=email) if user is not None: if user.is_active: auth_login(request, user) return HttpResponseRedirect(reverse('home'))

It doesn't work, the user is not authenticated. And I also have this error when I go to the /admin:

 AttributeError at /admin/logout/ 'EmailAuthBackend' object has no attribute 'get_user'

Sabito · Accepted Answer · 2021-07-22 11:23:55Z

For each custom backend in Django, you need to specify the get_user function. See the documentation. The get_user implementation can simply use the existing User table, like you are:

def get_user(self, user_id): try: return User.objects.get(pk=user_id) except User.DoesNotExist: return None

The reason this is required is for situations where you'd need to fetch the User via its primary key from a different source.

Sabito · Accepted Answer · 2021-08-16 04:19:09Z

While Bartek's answer is the correct one I'll just provide an example of another way to solve the problem by inheriting the ModelBackend.

from django.contrib.auth.backends import ModelBackend class EmailAuthBackend(ModelBackend): def authenticate(self, username=None, password=None, **kwargs): try: user = User.objects.get(email=username) if user.check_password(password): return user except ObjectDoesNotExist: # Run the default password hasher once to reduce the timing # difference between an existing and a non-existing user (#20760). User().set_password(password)

The get_user is already implemented by the ModelBackend and you get the permission methods along with it.

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