Source code for django_cas_ng.backends

"""CAS authentication backend"""

from typing import Mapping, Optional

from django.conf import settings
from django.contrib.auth import get_user_model
from django.contrib.auth.backends import ModelBackend
from django.contrib.auth.models import User
from django.core.exceptions import ImproperlyConfigured
from django.http import HttpRequest

from django_cas_ng.signals import cas_user_authenticated

from .utils import get_cas_client

__all__ = ['CASBackend']

[docs]class CASBackend(ModelBackend): """CAS authentication backend"""
[docs] def authenticate(self, request: HttpRequest, ticket: str, service: str) -> Optional[User]: """ Verifies CAS ticket and gets or creates User object :returns: [User] Authenticated User object or None if authenticate failed. """ client = get_cas_client(service_url=service, request=request) username, attributes, pgtiou = client.verify_ticket(ticket) if attributes and request: request.session['attributes'] = attributes if settings.CAS_USERNAME_ATTRIBUTE != 'cas:user' and settings.CAS_VERSION != 'CAS_2_SAML_1_0': if attributes: username = attributes.get(settings.CAS_USERNAME_ATTRIBUTE) else: return None if not username: return None user = None username = self.clean_username(username) if attributes: reject = self.bad_attributes_reject(request, username, attributes) if reject: return None # If we can, we rename the attributes as described in the settings file # Existing attributes will be overwritten for cas_attr_name, req_attr_name in settings.CAS_RENAME_ATTRIBUTES.items(): if cas_attr_name in attributes and cas_attr_name is not req_attr_name: attributes[req_attr_name] = attributes[cas_attr_name] attributes.pop(cas_attr_name) UserModel = get_user_model() # Note that this could be accomplished in one try-except clause, but # instead we use get_or_create when creating unknown users since it has # built-in safeguards for multiple threads. if settings.CAS_CREATE_USER: user_kwargs = { UserModel.USERNAME_FIELD: username } if settings.CAS_CREATE_USER_WITH_ID: user_kwargs['id'] = self.get_user_id(attributes) user, created = UserModel._default_manager.get_or_create(**user_kwargs) if created: user = self.configure_user(user) else: created = False try: if settings.CAS_LOCAL_NAME_FIELD: user_kwargs = { settings.CAS_LOCAL_NAME_FIELD: username } user = UserModel._default_manager.get(**user_kwargs) else: user = UserModel._default_manager.get_by_natural_key(username) except UserModel.DoesNotExist: pass if not self.user_can_authenticate(user): return None if pgtiou and settings.CAS_PROXY_CALLBACK and request: request.session['pgtiou'] = pgtiou if settings.CAS_APPLY_ATTRIBUTES_TO_USER and attributes: # If we are receiving None for any values which cannot be NULL # in the User model, set them to an empty string instead. # Possibly it would be desirable to let these throw an error # and push the responsibility to the CAS provider or remove # them from the dictionary entirely instead. Handling these # is a little ambiguous. user_model_fields = UserModel._meta.fields for field in user_model_fields: # Handle null -> '' conversions mentioned above if not field.null: try: if attributes[] is None: attributes[] = '' except KeyError: continue # Coerce boolean strings into true booleans if field.get_internal_type() == 'BooleanField': try: boolean_value = attributes[] == 'True' attributes[] = boolean_value except KeyError: continue user.__dict__.update(attributes) # If we are keeping a local copy of the user model we # should save these attributes which have a corresponding # instance in the DB. if settings.CAS_CREATE_USER: # send the `cas_user_authenticated` signal cas_user_authenticated.send( sender=self, user=user, created=created, username=username, attributes=attributes, pgtiou=pgtiou, ticket=ticket, service=service, request=request ) return user
[docs] def get_user_id(self, attributes: Mapping[str, str]) -> str: """ For use when CAS_CREATE_USER_WITH_ID is True. Will raise ImproperlyConfigured exceptions when a user_id cannot be accessed. This is important because we shouldn't create Users with automatically assigned ids if we are trying to keep User primary key's in sync. :returns: [string] user id. """ if not attributes: raise ImproperlyConfigured("CAS_CREATE_USER_WITH_ID is True, but " "no attributes were provided") user_id = attributes.get('id') if not user_id: raise ImproperlyConfigured("CAS_CREATE_USER_WITH_ID is True, but " "`'id'` is not part of attributes.") return user_id
[docs] def clean_username(self, username: str) -> str: """ Performs any cleaning on the ``username`` prior to using it to get or create the user object. By default, changes the username case according to `settings.CAS_FORCE_CHANGE_USERNAME_CASE`. :param username: [string] username. :returns: [string] The cleaned username. """ username_case = settings.CAS_FORCE_CHANGE_USERNAME_CASE if username_case == 'lower': username = username.lower() elif username_case == 'upper': username = username.upper() elif username_case is not None: raise ImproperlyConfigured( "Invalid value for the CAS_FORCE_CHANGE_USERNAME_CASE setting. " "Valid values are `'lower'`, `'upper'`, and `None`.") return username
[docs] def configure_user(self, user: User) -> User: """ Configures a user after creation and returns the updated user. This method is called immediately after a new user is created, and can be used to perform custom setup actions. :param user: User object. :returns: [User] The user object. By default, returns the user unmodified. """ return user
[docs] def bad_attributes_reject(self, request: HttpRequest, username: str, attributes: Mapping[str, str]) -> bool: """ Rejects a user if the returned username/attributes are not OK. :returns: [boolean] ``True/False``. Default is ``False``. """ return False