[1.7.x] Fixed #24193 -- Prevented unclosed file warnings in static.serve()

This regression was caused by 818e59a3f0. The patch is a partial
backport of the new FileResponse class available in later Django
versions.
Thanks Raphaël Hertzog for the report, and Tim Graham and Collin
Anderson for the reviews.

5 files changed, 30 insertions, 11 deletions

diff --git a/django/http/__init__.py b/django/http/__init__.py
index fc5bd180ad..99a5233b07 100644
--- a/django/http/__init__.py
+++ b/django/http/__init__.py
@@ -1,7 +1,8 @@
 from django.http.cookie import SimpleCookie, parse_cookie
 from django.http.request import (HttpRequest, QueryDict,
     RawPostDataException, UnreadablePostError, build_request_repr)
-from django.http.response import (HttpResponse, StreamingHttpResponse,
+from django.http.response import (
+    HttpResponse, StreamingHttpResponse, FileResponse,
     HttpResponseRedirect, HttpResponsePermanentRedirect,
     HttpResponseNotModified, HttpResponseBadRequest, HttpResponseForbidden,
     HttpResponseNotFound, HttpResponseNotAllowed, HttpResponseGone,
@@ -16,5 +17,5 @@ __all__ = [
     'HttpResponseBadRequest', 'HttpResponseForbidden', 'HttpResponseNotFound',
     'HttpResponseNotAllowed', 'HttpResponseGone', 'HttpResponseServerError',
     'Http404', 'BadHeaderError', 'fix_location_header', 'JsonResponse',
-    'conditional_content_removal',
+    'FileResponse', 'conditional_content_removal',
 ]
diff --git a/django/http/response.py b/django/http/response.py
index b3f44cdf92..06126eda67 100644
--- a/django/http/response.py
+++ b/django/http/response.py
@@ -382,6 +382,9 @@ class StreamingHttpResponse(HttpResponseBase):
 
     @streaming_content.setter
     def streaming_content(self, value):
+        self._set_streaming_content(value)
+
+    def _set_streaming_content(self, value):
         # Ensure we can never iterate on "value" more than once.
         self._iterator = iter(value)
         if hasattr(value, 'close'):
@@ -391,6 +394,21 @@ class StreamingHttpResponse(HttpResponseBase):
         return self.streaming_content
 
 
+class FileResponse(StreamingHttpResponse):
+    """
+    A streaming HTTP response class optimized for files.
+    """
+    block_size = 4096
+
+    def _set_streaming_content(self, value):
+        if hasattr(value, 'read'):
+            self._iterator = iter(lambda: value.read(self.block_size), b'')
+            if hasattr(value, 'close'):
+                self._closable_objects.append(value)
+        else:
+            super(FileResponse, self)._set_streaming_content(value)
+
+
 class HttpResponseRedirectBase(HttpResponse):
     allowed_schemes = ['http', 'https', 'ftp']
 
diff --git a/django/views/static.py b/django/views/static.py
index 0ce00a9963..19f57b72c1 100644
--- a/django/views/static.py
+++ b/django/views/static.py
@@ -11,14 +11,12 @@ import posixpath
 import re
 
 from django.http import (Http404, HttpResponse, HttpResponseRedirect,
-    HttpResponseNotModified, StreamingHttpResponse)
+    HttpResponseNotModified, FileResponse)
 from django.template import loader, Template, Context, TemplateDoesNotExist
 from django.utils.http import http_date, parse_http_date
 from django.utils.six.moves.urllib.parse import unquote
 from django.utils.translation import ugettext as _, ugettext_lazy
 
-STREAM_CHUNK_SIZE = 4096
-
 
 def serve(request, path, document_root=None, show_indexes=False):
     """
@@ -63,9 +61,7 @@ def serve(request, path, document_root=None, show_indexes=False):
         return HttpResponseNotModified()
     content_type, encoding = mimetypes.guess_type(fullpath)
     content_type = content_type or 'application/octet-stream'
-    f = open(fullpath, 'rb')
-    response = StreamingHttpResponse(iter(lambda: f.read(STREAM_CHUNK_SIZE), b''),
-                                     content_type=content_type)
+    response = FileResponse(open(fullpath, 'rb'), content_type=content_type)
     response["Last-Modified"] = http_date(statobj.st_mtime)
     if stat.S_ISREG(statobj.st_mode):
         response["Content-Length"] = statobj.st_size
diff --git a/docs/releases/1.7.4.txt b/docs/releases/1.7.4.txt
index 5f10e5e8c6..0d53459068 100644
--- a/docs/releases/1.7.4.txt
+++ b/docs/releases/1.7.4.txt
@@ -17,3 +17,6 @@ Bugfixes
 
 * Fixed a migration crash on MySQL when migrating from a ``OneToOneField`` to a
   ``ForeignKey`` (:ticket:`24163`).
+
+* Prevented the ``static.serve`` view from producing ``ResourceWarning``\s in
+  certain circumstances (security fix regression, :ticket:`24193`).
diff --git a/tests/view_tests/tests/test_static.py b/tests/view_tests/tests/test_static.py
index c7a36ce743..1f1ca44c83 100644
--- a/tests/view_tests/tests/test_static.py
+++ b/tests/view_tests/tests/test_static.py
@@ -5,10 +5,10 @@ from os import path
 import unittest
 
 from django.conf.urls.static import static
-from django.http import HttpResponseNotModified
+from django.http import FileResponse, HttpResponseNotModified
 from django.test import SimpleTestCase, override_settings
 from django.utils.http import http_date
-from django.views.static import was_modified_since, STREAM_CHUNK_SIZE
+from django.views.static import was_modified_since
 
 from .. import urls
 from ..urls import media_dir
@@ -37,10 +37,11 @@ class StaticTests(SimpleTestCase):
         "The static view should stream files in chunks to avoid large memory usage"
         response = self.client.get('/%s/%s' % (self.prefix, 'long-line.txt'))
         first_chunk = next(response.streaming_content)
-        self.assertEqual(len(first_chunk), STREAM_CHUNK_SIZE)
+        self.assertEqual(len(first_chunk), FileResponse.block_size)
         second_chunk = next(response.streaming_content)
         # strip() to prevent OS line endings from causing differences
         self.assertEqual(len(second_chunk.strip()), 1449)
+        response.close()
 
     def test_unknown_mime_type(self):
         response = self.client.get('/%s/file.unknown' % self.prefix)