Resolved #1299 - Allow StaticRoute to follow symlinks

CHANGES.rst

@@ -47,7 +47,7 @@ CHANGES
 
 - Added save and load functionality for `CookieJar` #1219
 
--
+- Added option on `StaticRoute` to follow symlinks #1299
 
 -
 

aiohttp/web_urldispatcher.py

@@ -335,7 +335,7 @@ class StaticResource(PrefixResource):
     def __init__(self, prefix, directory, *, name=None,
                  expect_handler=None, chunk_size=256*1024,
                  response_factory=StreamResponse,
-                 show_index=False):
+                 show_index=False, follow_symlinks=False):
         super().__init__(prefix, name=name)
         try:
             directory = Path(directory)
@@ -351,6 +351,7 @@ def __init__(self, prefix, directory, *, name=None,
         self._file_sender = FileSender(resp_factory=response_factory,
                                        chunk_size=chunk_size)
         self._show_index = show_index
+        self._follow_symlinks = follow_symlinks
 
         self._routes = {'GET': ResourceRoute('GET', self._handle, self,
                                              expect_handler=expect_handler),
@@ -397,7 +398,8 @@ def _handle(self, request):
         filename = unquote(request.match_info['filename'])
         try:
             filepath = self._directory.joinpath(filename).resolve()
-            filepath.relative_to(self._directory)
+            if not self._follow_symlinks:
+                filepath.relative_to(self._directory)
         except (ValueError, FileNotFoundError) as error:
             # relatively safe
             raise HTTPNotFound() from error
@@ -709,7 +711,7 @@ def add_route(self, method, path, handler,
 
     def add_static(self, prefix, path, *, name=None, expect_handler=None,
                    chunk_size=256*1024, response_factory=StreamResponse,
-                   show_index=False):
+                   show_index=False, follow_symlinks=False):
         """Add static files view.
 
         prefix - url prefix
@@ -725,7 +727,8 @@ def add_static(self, prefix, path, *, name=None, expect_handler=None,
                                   expect_handler=expect_handler,
                                   chunk_size=chunk_size,
                                   response_factory=response_factory,
-                                  show_index=show_index)
+                                  show_index=show_index,
+                                  follow_symlinks=follow_symlinks)
         self._reg_resource(resource)
         return resource
 

docs/spelling_wordlist.txt

@@ -174,6 +174,8 @@ subprotocol
 subprotocols
 subtype
 Svetlov
+symlink
+symlinks
 syscall
 syscalls
 TCP

docs/web.rst

@@ -348,6 +348,11 @@ instead could be enabled with ``show_index`` parameter set to ``True``::
 
    app.router.add_static('/prefix', path_to_static_folder, show_index=True)
 
+When a symlink from the static directory is accessed, the server responses to
+client with ``HTTP/404 Not Found`` by default. To allow the server to follow
+symlinks, parameter ``follow_symlinks`` should be set to ``True``::
+
+   app.router.add_static('/prefix', path_to_static_folder, follow_symlinks=True)
 
 Template Rendering
 ------------------

docs/web_reference.rst

@@ -1464,7 +1464,8 @@ Router is any object that implements :class:`AbstractRouter` interface.
    .. method:: add_static(prefix, path, *, name=None, expect_handler=None, \
                           chunk_size=256*1024, \
                           response_factory=StreamResponse, \
-                          show_index=False)
+                          show_index=False, \
+                          follow_symlinks=False)
 
       Adds a router and a handler for returning static files.
 
@@ -1520,6 +1521,10 @@ Router is any object that implements :class:`AbstractRouter` interface.
                               by default it's not allowed and HTTP/403 will
                               be returned on directory access.
 
+      :param bool follow_symlinks: flag for allowing to follow symlinks from
+                              a directory, by default it's not allowed and
+                              HTTP/404 will be returned on access.
+
    :returns: new :class:`StaticRoute` instance.
 
    .. coroutinemethod:: resolve(request)

tests/test_web_urldispatcher.py

@@ -75,6 +75,36 @@ def test_access_root_of_static_handler(tmp_dir_path, loop, test_client,
     yield from r.release()
 
 
+@pytest.mark.parametrize('data', ['hello world'])
+@asyncio.coroutine
+def test_follow_symlink(tmp_dir_path, loop, test_client, data):
+    """
+    Tests the access to a symlink, in static folder
+    """
+    my_dir_path = os.path.join(tmp_dir_path, 'my_dir')
+    os.mkdir(my_dir_path)
+
+    my_file_path = os.path.join(my_dir_path, 'my_file_in_dir')
+    with open(my_file_path, 'w') as fw:
+        fw.write(data)
+
+    my_symlink_path = os.path.join(tmp_dir_path, 'my_symlink')
+    os.symlink(my_dir_path, my_symlink_path)
+
+    app = web.Application(loop=loop)
+
+    # Register global static route:
+    app.router.add_static('/', tmp_dir_path, follow_symlinks=True)
+    client = yield from test_client(app)
+
+    # Request the root of the static directory.
+    r = yield from client.get('/my_symlink/my_file_in_dir')
+    assert r.status == 200
+    assert (yield from r.text()) == data
+
+    yield from r.release()
+
+
 @pytest.mark.parametrize('dir_name,filename,data', [
     ('', 'test file.txt', 'test text'),
     ('test dir name', 'test dir file .txt', 'test text file folder')