Add full URLs in exercises to ensure they always load

kolibri/core/content/test/test_zipcontent.py

@@ -5,6 +5,7 @@
 
 from django.test import Client
 from django.test import TestCase
+from le_utils.constants import exercises
 
 from ..models import LocalFile
 from ..utils.paths import get_content_storage_file_path
@@ -22,6 +23,8 @@ class ZipContentTestCase(TestCase):
     test_str_1 = "This is a test!"
     test_name_2 = "testfile2.txt"
     test_str_2 = "And another test..."
+    test_name_3 = "testfile3.json"
+    test_str_3 = "A test of image placeholder replacement ${placeholder}".format(placeholder=exercises.IMG_PLACEHOLDER)
 
     def setUp(self):
 
@@ -41,6 +44,7 @@ def setUp(self):
         with zipfile.ZipFile(self.zip_path, "w") as zf:
             zf.writestr(self.test_name_1, self.test_str_1)
             zf.writestr(self.test_name_2, self.test_str_2)
+            zf.writestr(self.test_name_3, self.test_str_3)
 
         self.zip_file_obj = LocalFile(id=self.hash, extension=self.extension, available=True)
         self.zip_file_base_url = self.zip_file_obj.get_storage_url()
@@ -82,6 +86,10 @@ def test_content_security_policy_header(self):
         response = self.client.get(self.zip_file_base_url + self.test_name_1)
         self.assertEqual(response.get("Content-Security-Policy"), "default-src 'self' 'unsafe-inline' 'unsafe-eval' data: http://testserver")
 
+    def test_content_security_policy_header_http_referer(self):
+        response = self.client.get(self.zip_file_base_url + self.test_name_1, HTTP_REFERER="http://testserver")
+        self.assertEqual(response.get("Content-Security-Policy"), "default-src 'self' 'unsafe-inline' 'unsafe-eval' data: http://testserver")
+
     def test_access_control_allow_origin_header(self):
         response = self.client.get(self.zip_file_base_url + self.test_name_1)
         self.assertEqual(response.get("Access-Control-Allow-Origin"), "*")
@@ -98,3 +106,13 @@ def test_access_control_allow_headers(self):
         self.assertEqual(response.get("Access-Control-Allow-Headers", ""), headerval)
         response = self.client.get(self.zip_file_base_url + self.test_name_1, HTTP_ACCESS_CONTROL_REQUEST_HEADERS=headerval)
         self.assertEqual(response.get("Access-Control-Allow-Headers", ""), headerval)
+
+    def test_json_image_replacement_http_referer_header(self):
+        server_name = "http://testserver"
+        response = self.client.get(self.zip_file_base_url + self.test_name_3, HTTP_REFERER=server_name)
+        self.assertEqual(response.content, self.test_str_3.replace("$" + exercises.IMG_PLACEHOLDER, (server_name + self.zip_file_base_url).strip("/")))
+
+    def test_json_image_replacement_no_http_referer_header(self):
+        server_name = "http://testserver"
+        response = self.client.get(self.zip_file_base_url + self.test_name_3)
+        self.assertEqual(response.content, self.test_str_3.replace("$" + exercises.IMG_PLACEHOLDER, (server_name + self.zip_file_base_url).strip("/")))

kolibri/core/content/views.py

@@ -6,9 +6,12 @@
 from django.http import HttpResponse
 from django.http.response import FileResponse
 from django.http.response import HttpResponseNotModified
+from django.urls import reverse
 from django.views.decorators.clickjacking import xframe_options_exempt
 from django.views.generic.base import View
 from le_utils.constants import exercises
+from six.moves.urllib.parse import urlparse
+from six.moves.urllib.parse import urlunparse
 
 from .api import cache_forever
 from .utils.paths import get_content_storage_file_path
@@ -27,6 +30,35 @@ def _add_access_control_headers(request, response):
         response["Access-Control-Allow-Headers"] = requested_headers
 
 
+def get_referrer_url(request):
+    if request.META.get('HTTP_REFERER'):
+        # If available user HTTP_REFERER to infer the host as that will give us more
+        # information if Kolibri is behind a proxy.
+        return urlparse(request.META.get('HTTP_REFERER'))
+
+
+def generate_image_prefix_url(zipped_filename, parsed_referrer_url):
+    # Remove trailing slash
+    zipcontent = reverse(
+        'kolibri:core:zipcontent',
+        kwargs={
+            "zipped_filename": zipped_filename,
+            "embedded_filepath": ''
+        })[:-1]
+    if parsed_referrer_url:
+        # Reconstruct the parsed URL using only the scheme(0) and host + port(1)
+        zipcontent = urlunparse((parsed_referrer_url[0], parsed_referrer_url[1], zipcontent, '', '', ''))
+    return zipcontent.encode()
+
+
+def get_host(request, parsed_referrer_url):
+    if parsed_referrer_url:
+        host = urlunparse((parsed_referrer_url[0], parsed_referrer_url[1], '', '', '', ''))
+    else:
+        host = request.build_absolute_uri(OPTIONS['Deployment']['URL_PATH_PREFIX'])
+    return host.strip("/")
+
+
 class ZipContentView(View):
 
     @xframe_options_exempt
@@ -59,6 +91,8 @@ def get(self, request, zipped_filename, embedded_filepath):
         if request.META.get('HTTP_IF_MODIFIED_SINCE'):
             return HttpResponseNotModified()
 
+        parsed_referrer_url = get_referrer_url(request)
+
         with zipfile.ZipFile(zipped_path) as zf:
 
             # if no path, or a directory, is being referenced, look for an index.html file
@@ -79,11 +113,11 @@ def get(self, request, zipped_filename, embedded_filepath):
                 response = FileResponse(zf.open(info), content_type=content_type)
                 file_size = info.file_size
             else:
+                image_prefix_url = generate_image_prefix_url(zipped_filename, parsed_referrer_url)
                 # load the stream from json file into memory, replace the path_place_holder.
                 content = zf.open(info).read()
                 str_to_be_replaced = ('$' + exercises.IMG_PLACEHOLDER).encode()
-                zipcontent = ('/' + request.resolver_match.url_name + "/" + zipped_filename).encode()
-                content_with_path = content.replace(str_to_be_replaced, zipcontent)
+                content_with_path = content.replace(str_to_be_replaced, image_prefix_url)
                 response = HttpResponse(content_with_path, content_type=content_type)
                 file_size = len(content_with_path)
 
@@ -99,7 +133,7 @@ def get(self, request, zipped_filename, embedded_filepath):
 
         # restrict CSP to only allow resources to be loaded from the Kolibri host, to prevent info leakage
         # (e.g. via passing user info out as GET parameters to an attacker's server), or inadvertent data usage
-        host = request.build_absolute_uri(OPTIONS['Deployment']['URL_PATH_PREFIX']).strip("/")
+        host = get_host(request, parsed_referrer_url)
         response["Content-Security-Policy"] = "default-src 'self' 'unsafe-inline' 'unsafe-eval' data: " + host
 
         return response