Django REST framework: Check user is in group

Question

I was wondering the best way to create a custom permission that checks if a user is in a particular group. Previously, I had a decorator I could use on a view to pass in a tuple of group names along with the user object and then check if that user was in the groups specified.

Ie:

def in_group_views(*group_names):
    """Requires user membership in at least one of the groups passed in."""

    def in_groups(u):
        if u.is_authenticated():
            if bool(u.groups.filter(name__in=group_names)) | u.is_superuser:
                return True
        return False

    return user_passes_test(in_groups)

How would I do this for DRF for a viewset, taking into account I need to check for different group memberships for different actions (POST,PUT,GET) etc.

Many thanks, Ben

Answer 1

The sensible way to parameterize permission classes is to put the parameters on the view class. That'll let you change the behaviour from view to view.

Here's an example:

# permissions.py
from django.contrib.auth.models import Group
from rest_framework import permissions

def is_in_group(user, group_name):
    """
    Takes a user and a group name, and returns `True` if the user is in that group.
    """
    try:
        return Group.objects.get(name=group_name).user_set.filter(id=user.id).exists()
    except Group.DoesNotExist:
        return None

class HasGroupPermission(permissions.BasePermission):
    """
    Ensure user is in required groups.
    """

    def has_permission(self, request, view):
        # Get a mapping of methods -> required group.
        required_groups_mapping = getattr(view, "required_groups", {})

        # Determine the required groups for this particular request method.
        required_groups = required_groups_mapping.get(request.method, [])

        # Return True if the user has all the required groups or is staff.
        return all([is_in_group(request.user, group_name) if group_name != "__all__" else True for group_name in required_groups]) or (request.user and request.user.is_staff)

You could then use the HasGroupPermission class like so:

# views.py
class MyView(APIView):
     permission_classes = [HasGroupPermission]
     required_groups = {
         'GET': ['moderators', 'members'],
         'POST': ['moderators', 'someMadeUpGroup'],
         'PUT': ['__all__'],
     }

     ...