Add validation of configuration model to enforce absolute URLs

Meant to avoid infinite redirect when matching the redirected URL with
the current URL.

splash/models.py

@@ -47,3 +47,8 @@ class SplashConfig(ConfigurationModel):
             return []
 
         return [name.strip() for name in self.unaffected_usernames.split(',')]  # pylint: disable=no-member
+
+    def save(self, *args, **kwargs):
+        """Call `full_clean` before saving to ensure proper validation of configuration values"""
+        self.full_clean()
+        super(SplashConfig, self).save(*args, **kwargs)

splash/tests.py

@@ -3,6 +3,7 @@ Splash - Tests
 """
 
 from django.contrib.auth.models import AnonymousUser, User
+from django.core.exceptions import ValidationError
 from django.test import TestCase
 from django.test.client import RequestFactory
 
@@ -22,7 +23,7 @@ class SplashMiddlewareTestCase(TestCase):
         Init
         """
         self.splash_middleware = SplashMiddleware()
-        self.request_factory = RequestFactory()
+        self.request_factory = RequestFactory(SERVER_NAME='example.org')
         SplashConfig().save()
 
     def build_request(self, username=None, cookies=None):
@@ -159,9 +160,18 @@ class SplashMiddlewareTestCase(TestCase):
         """
         SplashConfig(
             enabled=True,
-            redirect_url='http://testserver/somewhere'
+            redirect_url='http://example.org/somewhere'
         ).save()
 
         request = self.build_request()
         response = self.splash_middleware.process_request(request)
         self.assertEquals(response, None)
+
+    def test_set_non_absolute_url(self):
+        """
+        Make sure the URL is absolute, to make sure we can compare it
+        to the current URL
+        Should not validate with a non-absolute URL
+        """
+        config = SplashConfig(redirect_url='/somewhere')
+        self.assertRaises(ValidationError, config.save)