#29012: Coordination of Authorization Backends in Permission Checking
-------------------------------+--------------------------------------
Reporter: Mehmet Dogan | Owner: nobody
Type: Uncategorized | Status: new
Component: contrib.auth | Version: 2.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Mehmet Dogan:
Old description:
> Long story here: https://github.com/django-guardian/django-
> guardian/issues/49
>
> Short story: for authorization backends checking object level permissions
> (like guardian) usually requires calling the django's default
> authorization backend as a fallback to the more general set of
> permissions:
>
> {{{
> if user.has_perm('foo.change_bar', obj=bar) and
> user.has_perm('foo.change_bar'):
> ...
>
> }}}
>
> However, this not only looks ugly, but also requires polling of all the
> backends twice, and thus, is a performance loss.
>
> First, and possibly the best, solution to this is that, django does not
> deny permission if obj argument is provided, but just ignores it. This
> way by properly ordering backends in the settings, it could be a fallback
> solution for the lower level checkers. This might be the move in the
> right direction, although it is backwards incompatible.
>
> A second solution is a keyword argument, such as fallback_to_model=False,
> that will allow lower-level checkers mimic the model level permissions
> that django does. Although this looks not DRY at first, it would give
> other backends more control whether to fallback to django or not (in case
> first solution is also accepted of course, otherwise, this is needed to
> get the necessary permissions with one round of polling).
New description:
Long story here: https://github.com/django-guardian/django-
guardian/issues/49
Short story: for authorization backends checking object level permissions
(like guardian) usually requires calling the django's default
authorization backend as a fallback to the more general set of
permissions:
{{{
if user.has_perm('foo.change_bar', obj=bar) or
user.has_perm('foo.change_bar'):
...
}}}
However, this not only looks ugly, but also requires polling of all the
backends twice, and thus, is a performance loss.
First, and possibly the best, solution to this is that, django does not
deny permission if obj argument is provided, but just ignores it. This way
by properly ordering backends in the settings, it could be a fallback
solution for the lower level checkers. This might be the move in the right
direction, although it is backwards incompatible.
A second solution is a keyword argument, such as fallback_to_model=False,
that will allow lower-level checkers mimic the model level permissions
that django does. Although this looks not DRY at first, it would give
other backends more control whether to fallback to django or not (in case
first solution is also accepted of course, otherwise, this is needed to
get the necessary permissions with one round of polling).
--
--
Ticket URL: <https://code.djangoproject.com/ticket/29012#comment:1>
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