Disable http_proxy_to_wsgi middleware by default

Having this middleware as default is very convenient for deployments,
since this enables the application to handle the appropriate headers
correctly in order to deal with SSL, which is nice to have out of the
box. Heat, for instance, has already taken this middleware as default.

However, having this act on the headers by default may not be so
desirable, as the application may not be in front of a proxy, and thus
will have nothing that parses or strips the X-Forwarded-* headers.
Which can lead to security problems.

Thus, this patch proposes the enabling of this functionality through a
configuration option. This will enable more projects to take this
middleware into use by default, and the deployer would only need to
change one configuration file; while leaving the paste configuration
intact.

Change-Id: I50a70d477613025d3e54e4ee773bbb1d6fcf2e68
SecurityImpact

oslo_middleware/http_proxy_to_wsgi.py

@@ -12,9 +12,19 @@
 # implied. See the License for the specific language governing permissions and
 # limitations under the License.
 from debtcollector import removals
+from oslo_config import cfg
 from oslo_middleware import base
 
 
+OPTS = [
+    cfg.BoolOpt('enable_proxy_headers_parsing',
+                default=False,
+                help="Wether the application is behind a proxy or not. "
+                     "This determines if the middleware should parse the "
+                     "headers or not.")
+]
+
+
 class HTTPProxyToWSGI(base.ConfigurableMiddleware):
     """HTTP proxy to WSGI termination middleware.
 
@@ -23,6 +33,10 @@ class HTTPProxyToWSGI(base.ConfigurableMiddleware):
 
     """
 
+    def __init__(self, application, *args, **kwargs):
+        super(HTTPProxyToWSGI, self).__init__(application, *args, **kwargs)
+        self.oslo_conf.register_opts(OPTS, group='oslo_middleware')
+
     @staticmethod
     def _parse_rfc7239_header(header):
         """Parses RFC7239 Forward headers.
@@ -40,6 +54,8 @@ class HTTPProxyToWSGI(base.ConfigurableMiddleware):
         return result
 
     def process_request(self, req):
+        if not self._conf_get('enable_proxy_headers_parsing'):
+            return
         fwd_hdr = req.environ.get("HTTP_FORWARDED")
         if fwd_hdr:
             proxies = self._parse_rfc7239_header(fwd_hdr)

oslo_middleware/tests/test_http_proxy_to_wsgi.py

@@ -29,6 +29,10 @@ class TestHTTPProxyToWSGI(test_base.BaseTestCase):
             return util.application_uri(req.environ)
 
         self.middleware = http_proxy_to_wsgi.HTTPProxyToWSGI(fake_app)
+        self.middleware.oslo_conf.set_override('enable_proxy_headers_parsing',
+                                               True,
+                                               group='oslo_middleware',
+                                               enforce_type=True)
         self.request = webob.Request.blank('/foo/bar', method='POST')
 
     def test_backward_compat(self):
@@ -98,3 +102,30 @@ class TestHTTPProxyToWSGI(test_base.BaseTestCase):
         self.request.headers['X-Forwarded-Prefix'] = "/bla"
         response = self.request.get_response(self.middleware)
         self.assertEqual(b"https://example.com:8043/bla", response.body)
+
+
+class TestHTTPProxyToWSGIDisabled(test_base.BaseTestCase):
+
+    def setUp(self):
+        super(TestHTTPProxyToWSGIDisabled, self).setUp()
+
+        @webob.dec.wsgify()
+        def fake_app(req):
+            return util.application_uri(req.environ)
+
+        self.middleware = http_proxy_to_wsgi.HTTPProxyToWSGI(fake_app)
+        self.middleware.oslo_conf.set_override('enable_proxy_headers_parsing',
+                                               False,
+                                               group='oslo_middleware',
+                                               enforce_type=True)
+        self.request = webob.Request.blank('/foo/bar', method='POST')
+
+    def test_no_headers(self):
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"http://localhost:80/", response.body)
+
+    def test_url_translate_ssl_has_no_effect(self):
+        self.request.headers['X-Forwarded-Proto'] = "https"
+        self.request.headers['X-Forwarded-Host'] = "example.com:123"
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"http://localhost:80/", response.body)