Token Authentication for RESTful API: should the token be periodically changed?

Question

I'm building a RESTful API with Django and django-rest-framework.

As authentication mechanism we have chosen "Token Authentication" and I have already implemented it following Django-REST-Framework's documentation, the question is, should the application renew / change the Token periodically and if yes how? Should it be the mobile app that requires the token to be renewed or the web-app should do it autonomously?

What is the best practice?

Anybody here experienced with Django REST Framework and could suggest a technical solution?

(the last question has lower priority)

Answer 1

It is good practice to have mobile clients periodically renew their authentication token. This of course is up to the server to enforce.

The default TokenAuthentication class does not support this, however you can extend it to achieve this functionality.

For example:

from rest_framework.authentication import TokenAuthentication, get_authorization_header
from rest_framework.exceptions import AuthenticationFailed

class ExpiringTokenAuthentication(TokenAuthentication):
    def authenticate_credentials(self, key):
        try:
            token = self.model.objects.get(key=key)
        except self.model.DoesNotExist:
            raise exceptions.AuthenticationFailed('Invalid token')

        if not token.user.is_active:
            raise exceptions.AuthenticationFailed('User inactive or deleted')

        # This is required for the time comparison
        utc_now = datetime.utcnow()
        utc_now = utc_now.replace(tzinfo=pytz.utc)

        if token.created < utc_now - timedelta(hours=24):
            raise exceptions.AuthenticationFailed('Token has expired')

        return token.user, token

It is also required to override the default rest framework login view, so that the token is refreshed whenever a login is done:

class ObtainExpiringAuthToken(ObtainAuthToken):
    def post(self, request):
        serializer = self.serializer_class(data=request.data)
        if serializer.is_valid():
            token, created =  Token.objects.get_or_create(user=serializer.validated_data['user'])

            if not created:
                # update the created time of the token to keep it valid
                token.created = datetime.datetime.utcnow()
                token.save()

            return Response({'token': token.key})
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

obtain_expiring_auth_token = ObtainExpiringAuthToken.as_view()

And don't forget to modify the urls:

urlpatterns += patterns(
    '',
    url(r'^users/login/?$', '<path_to_file>.obtain_expiring_auth_token'),
)