Improve handling of pseudo-headers

- The canonical source for :method, :scheme and :path are the .method, .scheme
and .path attributes on the request object.
- These pseudo-headers are stripped after reading the request, and re-inserted
just before sending.
- The :authority header remains, and should be handled analagously to the Host
header in HTTP1 with respect to display and user interaction.

mitmproxy/protocol/http2.py

@@ -306,6 +306,9 @@ class Http2SingleStreamLayer(_HttpTransmissionLayer, threading.Thread):
         method = self.request_headers.get(':method', 'GET')
         scheme = self.request_headers.get(':scheme', 'https')
         path = self.request_headers.get(':path', '/')
+        self.request_headers.clear(":method")
+        self.request_headers.clear(":scheme")
+        self.request_headers.clear(":path")
         host = None
         port = None
 
@@ -362,10 +365,15 @@ class Http2SingleStreamLayer(_HttpTransmissionLayer, threading.Thread):
             self.server_stream_id = self.server_conn.h2.get_next_available_stream_id()
             self.server_to_client_stream_ids[self.server_stream_id] = self.client_stream_id
 
+            headers = message.headers.copy()
+            headers.insert(0, ":path", message.path)
+            headers.insert(0, ":method", message.method)
+            headers.insert(0, ":scheme", message.scheme)
+
             self.server_conn.h2.safe_send_headers(
                 self.is_zombie,
                 self.server_stream_id,
-                message.headers
+                headers
             )
         self.server_conn.h2.safe_send_body(
             self.is_zombie,

netlib/http/http2/connections.py

@@ -98,6 +98,11 @@ class HTTP2Protocol(object):
         method = headers.get(':method', 'GET')
         scheme = headers.get(':scheme', 'https')
         path = headers.get(':path', '/')
+
+        headers.clear(":method")
+        headers.clear(":scheme")
+        headers.clear(":path")
+
         host = None
         port = None
 
@@ -202,12 +207,9 @@ class HTTP2Protocol(object):
 
         if ':authority' not in headers:
             headers.insert(0, b':authority', authority.encode('ascii'))
-        if ':scheme' not in headers:
-            headers.insert(0, b':scheme', request.scheme.encode('ascii'))
-        if ':path' not in headers:
-            headers.insert(0, b':path', request.path.encode('ascii'))
-        if ':method' not in headers:
-            headers.insert(0, b':method', request.method.encode('ascii'))
+        headers.insert(0, b':scheme', request.scheme.encode('ascii'))
+        headers.insert(0, b':path', request.path.encode('ascii'))
+        headers.insert(0, b':method', request.method.encode('ascii'))
 
         if hasattr(request, 'stream_id'):
             stream_id = request.stream_id

netlib/multidict.py

@@ -171,6 +171,14 @@ class _MultiDict(MutableMapping, Serializable):
         else:
             return super(_MultiDict, self).items()
 
+    def clear(self, key):
+        """
+            Removes all items with the specified key, and does not raise an
+            exception if the key does not exist.
+        """
+        if key in self:
+            del self[key]
+
     def to_dict(self):
         """
         Get the MultiDict as a plain Python dict.

test/netlib/http/http2/test_connections.py

@@ -312,7 +312,10 @@ class TestReadRequest(tservers.ServerTestBase):
         req = protocol.read_request(NotImplemented)
 
         assert req.stream_id
-        assert req.headers.fields == ((b':method', b'GET'), (b':path', b'/'), (b':scheme', b'https'))
+        assert req.headers.fields == ()
+        assert req.method == "GET"
+        assert req.path == "/"
+        assert req.scheme == "https"
         assert req.content == b'foobar'