Ratelimiting registration form validation end point.

This patch would ratelimit registration form validation
endpoint for anonymous user based on his/her ip.

LEARNER-3810

lms/envs/common.py

@@ -2333,6 +2333,7 @@ REST_FRAMEWORK = {
     'DEFAULT_THROTTLE_RATES': {
         'user': '60/minute',
         'service_user': '120/minute',
+        'registration_validation': '30/minute',
     },
 }
 

lms/envs/test.py

@@ -574,6 +574,11 @@ ACTIVATION_EMAIL_FROM_ADDRESS = 'test_activate@edx.org'
 
 TEMPLATES[0]['OPTIONS']['debug'] = True
 
+########################### DRF default throttle rates ############################
+# Increasing rates to enable test cases hitting registration view succesfully.
+# Lower rate is causing view to get blocked, causing test case failure.
+REST_FRAMEWORK['DEFAULT_THROTTLE_RATES']['registration_validation'] = '100/minute'
+
 ########################## VIDEO TRANSCRIPTS STORAGE ############################
 VIDEO_TRANSCRIPTS_SETTINGS = dict(
     VIDEO_TRANSCRIPTS_MAX_BYTES=3 * 1024 * 1024,    # 3 MB

openedx/core/djangoapps/user_api/validation/tests/test_views.py

@@ -9,11 +9,13 @@ import ddt
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.urls import reverse
+from django.test.utils import override_settings
 from six import text_type
 
 from openedx.core.djangoapps.user_api import accounts
 from openedx.core.djangoapps.user_api.accounts.tests import testutils
 from openedx.core.lib.api import test_utils
+from openedx.core.djangoapps.user_api.validation.views import RegistrationValidationThrottle
 from util.password_policy_validators import password_max_length, password_min_length
 
 
@@ -199,3 +201,24 @@ class RegistrationValidationViewTests(test_utils.ApiTestCase):
             {"username": "somephrase", "password": "somephrase"},
             {"username": "", "password": u"Password cannot be the same as the username."}
         )
+
+    @override_settings(
+        CACHES={
+            'default': {
+                'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+                'LOCATION': 'registration_proxy',
+            }
+        }
+    )
+    def test_rate_limiting_registration_view(self):
+        """
+        Confirm rate limits work as expected for registration
+        end point /api/user/v1/validation/registration/. Note
+        that drf's rate limiting makes use of the default cache
+        to enforce limits; that's why this test needs a "real"
+        default cache (as opposed to the usual-for-tests DummyCache)
+        """
+        for _ in range(RegistrationValidationThrottle().num_requests):
+            self.request_without_auth('post', self.path)
+        response = self.request_without_auth('post', self.path)
+        self.assertEqual(response.status_code, 429)

openedx/core/djangoapps/user_api/validation/views.py

@@ -5,6 +5,7 @@ An API for client-side validation of (potential) user data.
 
 from rest_framework.response import Response
 from rest_framework.views import APIView
+from rest_framework.throttling import AnonRateThrottle
 
 from openedx.core.djangoapps.user_api.accounts.api import (
     get_email_validation_error,
@@ -16,6 +17,20 @@ from openedx.core.djangoapps.user_api.accounts.api import (
     get_username_validation_error,
     get_username_existence_validation_error
 )
+from ipware.ip import get_ip
+
+
+class RegistrationValidationThrottle(AnonRateThrottle):
+    """
+    Custom throttle rate for /api/user/v1/validation/registration
+    endpoint's use case.
+    """
+
+    scope = 'registration_validation'
+
+    def get_ident(self, request):
+        client_ip = get_ip(request)
+        return client_ip
 
 
 class RegistrationValidationView(APIView):
@@ -106,6 +121,7 @@ class RegistrationValidationView(APIView):
 
     # This end-point is available to anonymous users, so no authentication is needed.
     authentication_classes = []
+    throttle_classes = (RegistrationValidationThrottle,)
 
     def name_handler(self, request):
         name = request.data.get('name')