#20218: Default authorization backend returns False when queried for object 
level
permissions
------------------------------+------------------------------------
     Reporter:  soren@…       |                    Owner:  nobody
         Type:  Bug           |                   Status:  new
    Component:  contrib.auth  |                  Version:  1.5
     Severity:  Normal        |               Resolution:
     Keywords:  auth          |             Triage Stage:  Accepted
    Has patch:  0             |      Needs documentation:  0
  Needs tests:  0             |  Patch needs improvement:  0
Easy pickings:  0             |                    UI/UX:  0
------------------------------+------------------------------------

Comment (by Jamie Bliss):

 Replying to [ticket:20218 soren@…]:
 > Ticket #12462 suggests this is intentional, but doesn't give much of a
 rationale. It seems to me that if you don't want a user to be able to edit
 all objects of type XXX, don't give them the "app.change_XXX"?

 I think the rationale is that the current behavior handles the general
 permissions case (no object) while still falling through and allowing
 another provider to handle the object-specific case.

 The snippet to I used to work around this.

 {{{#!python
 class UseGeneralPermissions:
     """
     Permissions provider that does object-level permissions by using
 general permissions.
     """
     def has_perm(self, user_obj, perm, obj=None):
         if obj is None:
             return False
         else:
             # Retry using general permissions
             return user_obj.has_perm(perm)
 }}}

 As to how general and object-level permissions interact? That is
 completely unspecified, and there isn't a clear answer how it should be.
 1. A general given overrides an object-level ungiven, 2. A general ungiven
 overrides an object-level given. 1 still allows efficient bulk operations
 but UIs must check permissions on each object to know to display actions.
 2 allows UIs to display actions optimistically, but can prevent efficient
 bulk operations.

--
Ticket URL: <https://code.djangoproject.com/ticket/20218#comment:7>
Django <https://code.djangoproject.com/>
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