How to setup Django permissions to be specific to a certain model's instances?

Please consider a simple Django app containing a central model called Project. Other resources of this app are always tied to a specific Project.

Exemplary code:

class Project(models.Model):
    pass

class Page(models.Model):
    project = models.ForeignKey(Project)

I'd like to leverage Django's permission system to set granular permissions per existing project. In the example's case, a user should be able to have a view_page permission for some project instances, and don't have it for others.

In the end, I would like to have a function like has_perm that takes the permission codename and a project as input and returns True if the current user has the permission in the given project.

Is there a way to extend or replace Django's authorization system to achieve something like this?

I could extend the user's Group model to include a link to Project and check both, the group's project and its permissions. But that's not elegant and doesn't allow for assigning permissions to single users.

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Somewhat related questions on the Django forum can be found here:

• Authorization on sets of resources
• How are you handling user permissions in more complex projects?

from How to setup Django permissions to be specific to a certain model's instances?