Returning custom message when a permission is denied in DRF

Question

Django REST Framework has an excellent piece of documentation about permissions. I\'ve been able to use pre-made permission classes and also built my own.

However, there

Answer 1

By default, it is handled by default exception handler, and it is raising a standard message - https://github.com/tomchristie/django-rest-framework/blob/2eb9107b875972e442ed73eef0e653fd4480d873/rest_framework/views.py#L82

But, you can set own EXCEPTION_HANDLER in settings of DRF, and handle PermissionDenied exception to return message you want.

See description at http://www.django-rest-framework.org/api-guide/settings/

Answer 2

I faced the same problem using DRF 3.9.4. As a workaround I defined just a simple message property in the custom permission class and it works. You can also use getattr with the same result I guess.

class IPWhitelistPermission(permissions.BasePermission):

    def __init__(self):
        super(IPWhitelistPermission, self).__init__()
        self._client_ip = None

    def has_permission(self, request, view):
        ip = get_client_ip(request)
        ret = IPWhitelist.is_whitelisted(ip)

        if not ret:
            logger = logging.getLogger('access')
            logger.warn("Unauthorized access from IP %s" % ip)
            self._client_ip = ip
        return ret

    @property
    def message(self):
        return "This IP is not whitelisted [{}]".format(self._client_ip)

Answer 3

when permission isn't granted, I will raise a exception which custom response. It works on djangorestframewor(3.10.1) and django(2.2.3).

from rest_framework.permissions import BasePermission
from rest_framework.exceptions import APIException
from rest_framework import status


class IsLogin(BasePermission):
    """
    Allows access only to authenticated users.
    """

    def has_permission(self, request, view):
        if request.email:
            return True
        raise NeedLogin()


class NeedLogin(APIException):
    status_code = status.HTTP_403_FORBIDDEN
    default_detail = {'error': True, 'message': 'need login'}
    default_code = 'not_authenticated'

Answer 4

Building on Aysennoussi’s answer:

from rest_framework import permissions
From django.utils import timezone

class CustomerAccessPermission(permissions.BasePermission):
    message = 'Adding customers not allowed.'

    def has_permission(self, request, view): 
        if request.user.has_expired:
            self.message = “Your account has expired.”
            return False
        elif request.user.has_access:
            return True
        else:
            return False

Answer 5

From DRF

you can simply add message attribute.

from rest_framework import permissions

class IsSuperUserPermission(permissions.BasePermission):
    message = 'User is not superuser'

    def has_permission(self, request, view):
        return self.request.user.is_superuser

It will return a dict with key detail, something like this:

{
    'detail': 'User is not superuser'
}

But what if you want for example that the dict key not to be detail but errors for example, it will be the same how return errors DRF.

We can set message attribute not to string but to dict, something like this:

class IsSuperUserPermission(permissions.BasePermission):
    message = {'errors': ['User is not a superuser']}

    def has_permission(self, request, view):
        self.message['errors'].clear()
        return self.request.user.is_superuser

In this case the error will be:

{
    'errors': ['User is not a superuser']
}

Answer 6

You can send more than a single customized message if you want to. You can do it using GenericAPIException.

Step 1: Create a permissions.py file and write this code.

class Check_user_permission(permissions.BasePermission):
def has_permission(self, request, view):
    if request.method in permissions.SAFE_METHODS:
        return True
    else:
        response ={
            "success": "false",
            'message': "Post request is not allowed for user from admin group",
            "status_code":403,
        }
        raise GenericAPIException(detail=response, status_code=403)

Here, response is the JSON response you want to send.

Step 2: Go to view.py file and add the class Check_user_permission in the permission_classes list this way:

class UserList(APIView):
    permission_classes = (IsAuthenticated, Check_user_permission)
    authentication_class = JSONWebTokenAuthentication
    ... 
    ...

Now if you go to the endpoint and send a POST request you'll get this response.

{
"success": "false",
"message": "Post request is not allowed!",
"status_code": 403
}