Introduce HTTP Proxy to WSGI middleware

This middleware is supposed to be placed in front of any WSGI
application. It will translate the WSGI environment to an environment
mimicking the environment of the reverse proxy placed in front of it.

It supports translating:
- Protocol via X-Forwarded-Proto
- Host via X-Forwarded-Host
- Prefix via X-Forwarded-Prefix (not standard, but already used in other
  projects)
- Forwarded header (RFC7239)

Change-Id: I9e66e17a343fc454016415375bcd5a1285334f5a

2 files changed, 161 insertions, 0 deletions

diff --git a/oslo_middleware/http_proxy_to_wsgi.py b/oslo_middleware/http_proxy_to_wsgi.py
new file mode 100644
index 0000000..425f414
--- /dev/null
+++ b/oslo_middleware/http_proxy_to_wsgi.py
@@ -0,0 +1,70 @@
+# -*- encoding: utf-8 -*-
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied. See the License for the specific language governing permissions and
+# limitations under the License.
+
+from oslo_middleware import base
+
+
+class HTTPProxyToWSGIMiddleware(base.ConfigurableMiddleware):
+    """HTTP proxy to WSGI termination middleware.
+
+    This middleware overloads WSGI environment variables with the one provided
+    by the remote HTTP reverse proxy.
+
+    """
+
+    @staticmethod
+    def _parse_rfc7239_header(header):
+        """Parses RFC7239 Forward headers.
+
+        e.g. for=192.0.2.60;proto=http, for=192.0.2.60;by=203.0.113.43
+
+        """
+        result = []
+        for proxy in header.split(","):
+            entry = {}
+            for d in proxy.split(";"):
+                key, _, value = d.partition("=")
+                entry[key.lower()] = value
+            result.append(entry)
+        return result
+
+    def process_request(self, req):
+        fwd_hdr = req.environ.get("HTTP_FORWARDED")
+        if fwd_hdr:
+            proxies = self._parse_rfc7239_header(fwd_hdr)
+            # Let's use the value from the first proxy
+            if proxies:
+                proxy = proxies[0]
+
+                forwarded_proto = proxy.get("proto")
+                if forwarded_proto:
+                    req.environ['wsgi.url_scheme'] = forwarded_proto
+
+                forwarded_host = proxy.get("host")
+                if forwarded_host:
+                    req.environ['HTTP_HOST'] = forwarded_host
+
+        else:
+            # World before RFC7239
+            forwarded_proto = req.environ.get("HTTP_X_FORWARDED_PROTO")
+            if forwarded_proto:
+                req.environ['wsgi.url_scheme'] = forwarded_proto
+
+            forwarded_host = req.environ.get("HTTP_X_FORWARDED_HOST")
+            if forwarded_host:
+                req.environ['HTTP_HOST'] = forwarded_host
+
+        v = req.environ.get("HTTP_X_FORWARDED_PREFIX")
+        if v:
+            req.environ['SCRIPT_NAME'] = v + req.environ['SCRIPT_NAME']
diff --git a/oslo_middleware/tests/test_http_proxy_to_wsgi.py b/oslo_middleware/tests/test_http_proxy_to_wsgi.py
new file mode 100644
index 0000000..bbd3601
--- /dev/null
+++ b/oslo_middleware/tests/test_http_proxy_to_wsgi.py
@@ -0,0 +1,91 @@
+# Copyright (c) 2015 Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+from wsgiref import util
+
+from oslotest import base as test_base
+import webob
+
+from oslo_middleware import http_proxy_to_wsgi
+
+
+class TestHTTPProxyToWSGI(test_base.BaseTestCase):
+
+    def setUp(self):
+        super(TestHTTPProxyToWSGI, self).setUp()
+
+        @webob.dec.wsgify()
+        def fake_app(req):
+            return util.application_uri(req.environ)
+
+        self.middleware = http_proxy_to_wsgi.HTTPProxyToWSGIMiddleware(
+            fake_app)
+        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(self):
+        self.request.headers['X-Forwarded-Proto'] = "https"
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"https://localhost:80/", response.body)
+
+    def test_url_translate_ssl_port(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"https://example.com:123/", response.body)
+
+    def test_url_translate_host_ipv6(self):
+        self.request.headers['X-Forwarded-Proto'] = "https"
+        self.request.headers['X-Forwarded-Host'] = "[f00:b4d::1]:123"
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"https://[f00:b4d::1]:123/", response.body)
+
+    def test_url_translate_base(self):
+        self.request.headers['X-Forwarded-Prefix'] = "/bla"
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"http://localhost:80/bla", response.body)
+
+    def test_url_translate_port_and_base_and_proto_and_host(self):
+        self.request.headers['X-Forwarded-Proto'] = "https"
+        self.request.headers['X-Forwarded-Prefix'] = "/bla"
+        self.request.headers['X-Forwarded-Host'] = "example.com:8043"
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"https://example.com:8043/bla", response.body)
+
+    def test_rfc7239_invalid(self):
+        self.request.headers['Forwarded'] = (
+            "iam=anattacker;metoo, I will crash you!!P;m,xx")
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"http://localhost:80/", response.body)
+
+    def test_rfc7239_proto(self):
+        self.request.headers['Forwarded'] = (
+            "for=foobar;proto=https, for=foobaz;proto=http")
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"https://localhost:80/", response.body)
+
+    def test_rfc7239_proto_host(self):
+        self.request.headers['Forwarded'] = (
+            "for=foobar;proto=https;host=example.com, for=foobaz;proto=http")
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"https://example.com/", response.body)
+
+    def test_rfc7239_proto_host_base(self):
+        self.request.headers['Forwarded'] = (
+            "for=foobar;proto=https;host=example.com:8043, for=foobaz")
+        self.request.headers['X-Forwarded-Prefix'] = "/bla"
+        response = self.request.get_response(self.middleware)
+        self.assertEqual(b"https://example.com:8043/bla", response.body)