nk20/apps/permission/backends.py

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# Copyright (C) 2018-2021 by BDE ENS Paris-Saclay
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# SPDX-License-Identifier: GPL-3.0-or-later
from datetime import date
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from django.contrib.auth.backends import ModelBackend
from django.contrib.auth.models import User
from django.contrib.contenttypes.models import ContentType
from django.db.models import Q, F
from django.utils import timezone
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from note.models import Note, NoteUser, NoteClub, NoteSpecial
from note_kfet.middlewares import get_current_request
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from member.models import Membership, Club
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from .decorators import memoize
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from .models import Permission
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class PermissionBackend(ModelBackend):
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"""
Manage permissions of users
"""
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supports_object_permissions = True
supports_anonymous_user = False
supports_inactive_user = False
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@staticmethod
@memoize
def get_raw_permissions(user, t):
"""
Query permissions of a certain type for a user, then memoize it.
:param user: The owner of the permissions
:param t: The type of the permissions: view, change, add or delete
:return: The queryset of the permissions of the user (memoized) grouped by clubs
"""
if not user.is_authenticated:
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# Unauthenticated users have no permissions
return Permission.objects.none()
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memberships = Membership.objects.filter(user=user).all()
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perms = []
for membership in memberships:
for role in membership.roles.all():
for perm in role.permissions.filter(
type=t, mask__rank__lte=get_current_request().session.get("permission_mask", -1)).all():
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if not perm.permanent:
if membership.date_start > date.today() or membership.date_end < date.today():
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continue
perm.membership = membership
perms.append(perm)
return perms
@staticmethod
def permissions(user, model, type):
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"""
List all permissions of the given user that applies to a given model and a give type
:param user: The owner of the permissions
:param model: The model that the permissions shoud apply
:param type: The type of the permissions: view, change, add or delete
:return: A generator of the requested permissions
"""
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for permission in PermissionBackend.get_raw_permissions(user, type):
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if not isinstance(model.model_class()(), permission.model.model_class()) or not permission.membership:
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continue
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membership = permission.membership
club = membership.club
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permission = permission.about(
user=user,
club=club,
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membership=membership,
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User=User,
Club=Club,
Membership=Membership,
Note=Note,
NoteUser=NoteUser,
NoteClub=NoteClub,
NoteSpecial=NoteSpecial,
F=F,
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Q=Q,
now=timezone.now(),
today=date.today(),
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)
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yield permission
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@staticmethod
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@memoize
def filter_queryset(request, model, t, field=None):
"""
Filter a queryset by considering the permissions of a given user.
:param request: The current request
:param model: The concerned model of the queryset
:param t: The type of modification (view, add, change, delete)
:param field: The field of the model to test, if concerned
:return: A query that corresponds to the filter to give to a queryset
"""
user = request.user
if user is None or not user.is_authenticated:
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# Anonymous users can't do anything
return Q(pk=-1)
if user.is_superuser and get_current_request().session.get("permission_mask", -1) >= 42:
# Superusers have all rights
return Q()
if not isinstance(model, ContentType):
model = ContentType.objects.get_for_model(model)
# Never satisfied
query = Q(pk=-1)
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perms = PermissionBackend.permissions(user, model, t)
for perm in perms:
if perm.field and field != perm.field:
continue
if perm.type != t or perm.model != model:
continue
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perm.update_query()
query = query | perm.query
return query
@staticmethod
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@memoize
def check_perm(request, perm, obj=None):
"""
Check is the given user has the permission over a given object.
The result is then memoized.
Exception: for add permissions, since the object is not hashable since it doesn't have any
primary key, the result is not memoized. Moreover, the right could change
(e.g. for a transaction, the balance of the user could change)
"""
user_obj = request.user
if user_obj is None or not user_obj.is_authenticated:
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return False
sess = request.session
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if user_obj.is_superuser and sess.get("permission_mask", -1) >= 42:
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return True
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if obj is None:
return True
perm = perm.split('.')[-1].split('_', 2)
perm_type = perm[0]
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perm_field = perm[2] if len(perm) == 3 else None
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ct = ContentType.objects.get_for_model(obj)
if any(permission.applies(obj, perm_type, perm_field)
for permission in PermissionBackend.permissions(user_obj, ct, perm_type)):
return True
return False
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def has_perm(self, user_obj, perm, obj=None):
# Warning: this does not check that user_obj has the permission,
# but if the current request has the permission.
# This function is implemented for backward compatibility, and should not be used.
return PermissionBackend.check_perm(get_current_request(), perm, obj)
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def has_module_perms(self, user_obj, app_label):
return False
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def get_all_permissions(self, user_obj, obj=None):
ct = ContentType.objects.get_for_model(obj)
return list(self.permissions(user_obj, ct, "view"))