From: Tom Hacohen <tasn@users.noreply.github.com>
Date: Fri, 4 Jan 2019 02:21:55 +0000
Subject: Fixed #30070,
 CVE-2019-3498 -- Fixed content spoofing possiblity in the default 404 page.

Co-Authored-By: Tim Graham <timograham@gmail.com>
Backport of 1ecc0a395be721e987e8e9fdfadde952b6dee1c7 from master.
---
 django/views/defaults.py |  8 +++++---
 tests/handlers/tests.py  | 12 ++++++++----
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/django/views/defaults.py b/django/views/defaults.py
index 348837e..5ec9ac8 100644
--- a/django/views/defaults.py
+++ b/django/views/defaults.py
@@ -2,6 +2,7 @@ from django import http
 from django.template import Context, Engine, TemplateDoesNotExist, loader
 from django.utils import six
 from django.utils.encoding import force_text
+from django.utils.http import urlquote
 from django.views.decorators.csrf import requires_csrf_token
 
 ERROR_404_TEMPLATE_NAME = '404.html'
@@ -21,7 +22,8 @@ def page_not_found(request, exception, template_name=ERROR_404_TEMPLATE_NAME):
     Templates: :template:`404.html`
     Context:
         request_path
-            The path of the requested URL (e.g., '/app/pages/bad_page/')
+            The path of the requested URL (e.g., '/app/pages/bad_page/'). It's
+            quoted to prevent a content injection attack.
         exception
             The message from the exception which triggered the 404 (if one was
             supplied), or the exception class name
@@ -37,7 +39,7 @@ def page_not_found(request, exception, template_name=ERROR_404_TEMPLATE_NAME):
         if isinstance(message, six.text_type):
             exception_repr = message
     context = {
-        'request_path': request.path,
+        'request_path': urlquote(request.path),
         'exception': exception_repr,
     }
     try:
@@ -50,7 +52,7 @@ def page_not_found(request, exception, template_name=ERROR_404_TEMPLATE_NAME):
             raise
         template = Engine().from_string(
             '<h1>Not Found</h1>'
-            '<p>The requested URL {{ request_path }} was not found on this server.</p>')
+            '<p>The requested resource was not found on this server.</p>')
         body = template.render(Context(context))
         content_type = 'text/html'
     return http.HttpResponseNotFound(body, content_type=content_type)
diff --git a/tests/handlers/tests.py b/tests/handlers/tests.py
index 9f01cb2..50a3488 100644
--- a/tests/handlers/tests.py
+++ b/tests/handlers/tests.py
@@ -2,6 +2,7 @@
 
 from __future__ import unicode_literals
 
+import sys
 import unittest
 
 from django.core.exceptions import ImproperlyConfigured
@@ -19,6 +20,8 @@ try:
 except ImportError:  # Python < 3.5
     HTTPStatus = None
 
+PY37 = sys.version_info >= (3, 7, 0)
+
 
 class HandlerTests(SimpleTestCase):
 
@@ -180,16 +183,17 @@ class HandlerRequestTests(SimpleTestCase):
 
     def test_invalid_urls(self):
         response = self.client.get('~%A9helloworld')
-        self.assertContains(response, '~%A9helloworld', status_code=404)
+        self.assertEqual(response.status_code, 404)
+        self.assertEqual(response.context['request_path'], '/~%25A9helloworld' if PY37 else '/%7E%25A9helloworld')
 
         response = self.client.get('d%aao%aaw%aan%aal%aao%aaa%aad%aa/')
-        self.assertContains(response, 'd%AAo%AAw%AAn%AAl%AAo%AAa%AAd%AA', status_code=404)
+        self.assertEqual(response.context['request_path'], '/d%25AAo%25AAw%25AAn%25AAl%25AAo%25AAa%25AAd%25AA')
 
         response = self.client.get('/%E2%99%E2%99%A5/')
-        self.assertContains(response, '%E2%99\u2665', status_code=404)
+        self.assertEqual(response.context['request_path'], '/%25E2%2599%E2%99%A5/')
 
         response = self.client.get('/%E2%98%8E%E2%A9%E2%99%A5/')
-        self.assertContains(response, '\u260e%E2%A9\u2665', status_code=404)
+        self.assertEqual(response.context['request_path'], '/%E2%98%8E%25E2%25A9%E2%99%A5/')
 
     def test_environ_path_info_type(self):
         environ = RequestFactory().get('/%E2%A8%87%87%A5%E2%A8%A0').environ