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import inspect
import re
from django.apps import apps as django_apps
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured, PermissionDenied
from django.middleware.csrf import rotate_token
from django.utils.crypto import constant_time_compare
from django.utils.module_loading import import_string
from django.utils.translation import LANGUAGE_SESSION_KEY
from .signals import user_logged_in, user_logged_out, user_login_failed
SESSION_KEY = '_auth_user_id'
BACKEND_SESSION_KEY = '_auth_user_backend'
HASH_SESSION_KEY = '_auth_user_hash'
REDIRECT_FIELD_NAME = 'next'
def load_backend(path):
return import_string(path)()
def _get_backends(return_tuples=False):
backends = []
for backend_path in settings.AUTHENTICATION_BACKENDS:
backend = load_backend(backend_path)
backends.append((backend, backend_path) if return_tuples else backend)
if not backends:
raise ImproperlyConfigured(
'No authentication backends have been defined. Does '
'AUTHENTICATION_BACKENDS contain anything?'
)
return backends
def get_backends():
return _get_backends(return_tuples=False)
def _clean_credentials(credentials):
"""
Cleans a dictionary of credentials of potentially sensitive info before
sending to less secure functions.
Not comprehensive - intended for user_login_failed signal
"""
SENSITIVE_CREDENTIALS = re.compile('api|token|key|secret|password|signature', re.I)
CLEANSED_SUBSTITUTE = '********************'
for key in credentials:
if SENSITIVE_CREDENTIALS.search(key):
credentials[key] = CLEANSED_SUBSTITUTE
return credentials
def _get_user_session_key(request):
# This value in the session is always serialized to a string, so we need
# to convert it back to Python whenever we access it.
return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
def authenticate(**credentials):
"""
If the given credentials are valid, return a User object.
"""
for backend, backend_path in _get_backends(return_tuples=True):
try:
inspect.getcallargs(backend.authenticate, **credentials)
except TypeError:
# This backend doesn't accept these credentials as arguments. Try the next one.
continue
try:
user = backend.authenticate(**credentials)
except PermissionDenied:
# This backend says to stop in our tracks - this user should not be allowed in at all.
return None
if user is None:
continue
# Annotate the user object with the path of the backend.
user.backend = backend_path
return user
# The credentials supplied are invalid to all backends, fire signal
user_login_failed.send(sender=__name__,
credentials=_clean_credentials(credentials))
def login(request, user):
"""
Persist a user id and a backend in the request. This way a user doesn't
have to reauthenticate on every request. Note that data set during
the anonymous session is retained when the user logs in.
"""
session_auth_hash = ''
if user is None:
user = request.user
if hasattr(user, 'get_session_auth_hash'):
session_auth_hash = user.get_session_auth_hash()
if SESSION_KEY in request.session:
if _get_user_session_key(request) != user.pk or (
session_auth_hash and
request.session.get(HASH_SESSION_KEY) != session_auth_hash):
# To avoid reusing another user's session, create a new, empty
# session if the existing session corresponds to a different
# authenticated user.
request.session.flush()
else:
request.session.cycle_key()
request.session[SESSION_KEY] = user._meta.pk.value_to_string(user)
request.session[BACKEND_SESSION_KEY] = user.backend
request.session[HASH_SESSION_KEY] = session_auth_hash
if hasattr(request, 'user'):
request.user = user
rotate_token(request)
user_logged_in.send(sender=user.__class__, request=request, user=user)
def logout(request):
"""
Removes the authenticated user's ID from the request and flushes their
session data.
"""
# Dispatch the signal before the user is logged out so the receivers have a
# chance to find out *who* logged out.
user = getattr(request, 'user', None)
if hasattr(user, 'is_authenticated') and not user.is_authenticated():
user = None
user_logged_out.send(sender=user.__class__, request=request, user=user)
# remember language choice saved to session
language = request.session.get(LANGUAGE_SESSION_KEY)
request.session.flush()
if language is not None:
request.session[LANGUAGE_SESSION_KEY] = language
if hasattr(request, 'user'):
from django.contrib.auth.models import AnonymousUser
request.user = AnonymousUser()
def get_user_model():
"""
Returns the User model that is active in this project.
"""
try:
return django_apps.get_model(settings.AUTH_USER_MODEL)
except ValueError:
raise ImproperlyConfigured("AUTH_USER_MODEL must be of the form 'app_label.model_name'")
except LookupError:
raise ImproperlyConfigured(
"AUTH_USER_MODEL refers to model '%s' that has not been installed" % settings.AUTH_USER_MODEL
)
def get_user(request):
"""
Returns the user model instance associated with the given request session.
If no user is retrieved an instance of `AnonymousUser` is returned.
"""
from .models import AnonymousUser
user = None
try:
user_id = _get_user_session_key(request)
backend_path = request.session[BACKEND_SESSION_KEY]
except KeyError:
pass
else:
if backend_path in settings.AUTHENTICATION_BACKENDS:
backend = load_backend(backend_path)
user = backend.get_user(user_id)
# Verify the session
if ('django.contrib.auth.middleware.SessionAuthenticationMiddleware'
in settings.MIDDLEWARE_CLASSES and hasattr(user, 'get_session_auth_hash')):
session_hash = request.session.get(HASH_SESSION_KEY)
session_hash_verified = session_hash and constant_time_compare(
session_hash,
user.get_session_auth_hash()
)
if not session_hash_verified:
request.session.flush()
user = None
return user or AnonymousUser()
def get_permission_codename(action, opts):
"""
Returns the codename of the permission for the specified action.
"""
return '%s_%s' % (action, opts.model_name)
def update_session_auth_hash(request, user):
"""
Updating a user's password logs out all sessions for the user if
django.contrib.auth.middleware.SessionAuthenticationMiddleware is enabled.
This function takes the current request and the updated user object from
which the new session hash will be derived and updates the session hash
appropriately to prevent a password change from logging out the session
from which the password was changed.
"""
if hasattr(user, 'get_session_auth_hash') and request.user == user:
request.session[HASH_SESSION_KEY] = user.get_session_auth_hash()
default_app_config = 'django.contrib.auth.apps.AuthConfig'
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