[sans-io] websockets: fix bugs, 100% test coverage 🎉

mitmproxy/proxy2/layers/http/__init__.py

@@ -297,7 +297,12 @@ class HttpStream(layer.Layer):
         yield SendHttp(ResponseEndOfMessage(self.stream_id), self.context.client)
 
         if self.flow.response.status_code == 101:
-            if self.flow.response.headers.get("upgrade", "").strip().lower() == "websocket":
+            is_websocket = (
+                    self.flow.response.headers.get("upgrade", "").lower() == "websocket"
+                    and
+                    self.flow.request.headers.get("Sec-WebSocket-Version", "") == "13"
+            )
+            if is_websocket:
                 self.child_layer = websocket.WebsocketLayer(self.context, self.flow)
             else:
                 self.child_layer = tcp.TCPLayer(self.context)

mitmproxy/proxy2/layers/websocket.py

@@ -69,6 +69,9 @@ class WebsocketConnection(wsproto.Connection):
         data = super().send(event)
         return commands.SendData(self.conn, data)
 
+    def __repr__(self):
+        return f"WebsocketConnection<{self.state.name}, {self.conn}>"
+
 
 class WebsocketLayer(layer.Layer):
     """
@@ -92,7 +95,7 @@ class WebsocketLayer(layer.Layer):
         # Parse extension headers. We only support deflate at the moment and ignore everything else.
         ext_header = self.flow.handshake_flow.response.headers.get("Sec-WebSocket-Extensions", "")
         if ext_header:
-            for ext in wsproto.utilities.split_comma_header(ext_header):
+            for ext in wsproto.utilities.split_comma_header(ext_header.encode("ascii", "replace")):
                 ext_name = ext.split(";", 1)[0].strip()
                 if ext_name == wsproto.extensions.PerMessageDeflate.name:
                     client_deflate = wsproto.extensions.PerMessageDeflate()
@@ -109,7 +112,7 @@ class WebsocketLayer(layer.Layer):
 
         yield WebsocketStartHook(self.flow)
 
-        if self.flow.stream:
+        if self.flow.stream:  # pragma: no cover
             raise NotImplementedError("WebSocket streaming is not supported at the moment.")
 
         self._handle_event = self.relay_messages
@@ -130,10 +133,8 @@ class WebsocketLayer(layer.Layer):
         if isinstance(event, events.DataReceived):
             src_ws.receive_data(event.data)
         elif isinstance(event, events.ConnectionClosed):
-            if src_ws.state not in {ConnectionState.OPEN, ConnectionState.LOCAL_CLOSING}:
-                return
             src_ws.receive_data(None)
-        else:
+        else:  # pragma: no cover
             raise AssertionError(f"Unexpected event: {event}")
 
         for ws_event in src_ws.events():
@@ -143,14 +144,10 @@ class WebsocketLayer(layer.Layer):
                 if ws_event.message_finished:
                     if isinstance(ws_event, wsproto.events.TextMessage):
                         frame_type = Opcode.TEXT
-                        content = ""
+                        content = "".join(src_ws.frame_buf)
                     else:
                         frame_type = Opcode.BINARY
-                        content = b""
+                        content = b"".join(src_ws.frame_buf)
-                    try:
-                        content = content.join(src_ws.frame_buf)
-                    except TypeError:
-                        return self.handle_protocol_error(src_ws, "mixed text and binary fragments")
 
                     fragmentizer = Fragmentizer(src_ws.frame_buf)
                     src_ws.frame_buf.clear()
@@ -166,8 +163,8 @@ class WebsocketLayer(layer.Layer):
 
             elif isinstance(ws_event, (wsproto.events.Ping, wsproto.events.Pong)):
                 yield commands.Log(
-                    f"Received WebSocket {event.__class__.__name__.lower()} from {from_str} "
+                    f"Received WebSocket {ws_event.__class__.__name__.lower()} from {from_str} "
-                    f"(payload: {ws_event.payload!r})"
+                    f"(payload: {bytes(ws_event.payload)!r})"
                 )
                 yield dst_ws.send(ws_event)
             elif isinstance(ws_event, wsproto.events.CloseConnection):
@@ -175,7 +172,7 @@ class WebsocketLayer(layer.Layer):
                 self.flow.close_code = ws_event.code
                 self.flow.close_reason = ws_event.reason
 
-                for ws in [self.client_ws, self.server_ws]:
+                for ws in [self.server_ws, self.client_ws]:
                     if ws.state in {ConnectionState.OPEN, ConnectionState.REMOTE_CLOSING}:
                         # response == original event, so no need to differentiate here.
                         yield ws.send(ws_event)
@@ -185,17 +182,9 @@ class WebsocketLayer(layer.Layer):
                 else:
                     self.flow.error = flow.Error(f"WebSocket Error: {format_close_event(ws_event)}")
                     yield WebsocketErrorHook(self.flow)
-                yield commands.CloseConnection(self.context.client)
-            else:
-                raise AssertionError(f"Unexpected WebSocket event: {ws_event}")
-
-    def handle_protocol_error(self, ws: WebsocketConnection, message=None):
-        self.flow.error = flow.Error(f"WebSocket Error: {human.format_address(ws.conn.peername)} {message}")
-        yield WebsocketErrorHook(self.flow)
-        if ws.state in {ConnectionState.OPEN, ConnectionState.REMOTE_CLOSING}:
-            yield ws.send(wsproto.events.CloseConnection(CloseReason.PROTOCOL_ERROR, message))
-        yield commands.CloseConnection(self.context.client)
                 self._handle_event = self.done
+            else:  # pragma: no cover
+                raise AssertionError(f"Unexpected WebSocket event: {ws_event}")
 
     @expect(events.DataReceived, events.ConnectionClosed)
     def done(self, _) -> layer.CommandGenerator[None]:
@@ -219,7 +208,7 @@ class Fragmentizer:
        meaning.  An intermediary might coalesce and/or split frames, [...]
 
     Practice:
-        Some WebSocket servers reject large payload sizes. ¯\_(ツ)_/¯
+        Some WebSocket servers reject large payload sizes.
 
     As a workaround, we either retain the original chunking or, if the payload has been modified, use ~4kB chunks.
     """

test/mitmproxy/proxy2/layers/test_websocket.py

@@ -0,0 +1,334 @@
+import secrets
+from dataclasses import dataclass
+
+import pytest
+
+import wsproto
+import wsproto.events
+from mitmproxy.http import HTTPFlow
+from mitmproxy.net.http import Request, Response
+from mitmproxy.proxy.protocol.http import HTTPMode
+from mitmproxy.proxy2.commands import SendData, CloseConnection, Log
+from mitmproxy.proxy2.context import Server, ConnectionState
+from mitmproxy.proxy2.events import DataReceived, ConnectionClosed
+from mitmproxy.proxy2.layers import http, websocket
+from mitmproxy.websocket import WebSocketFlow
+from test.mitmproxy.proxy2.tutils import Placeholder, Playbook, reply
+
+
+@dataclass
+class _Masked:
+    unmasked: bytes
+
+    def __eq__(self, other):
+        other = bytearray(other)
+        assert other[1] & 0b1000_0000  # assert this is actually masked
+        other[1] &= 0b0111_1111  # remove mask bit
+        assert other[1] < 126  # (we don't support extended payload length here)
+        mask = other[2:6]
+        payload = bytes([x ^ mask[i % 4] for i, x in enumerate(other[6:])])
+        return self.unmasked == other[:2] + payload
+
+
+# noinspection PyTypeChecker
+def masked(unmasked: bytes) -> bytes:
+    return _Masked(unmasked)  # type: ignore
+
+
+def masked_bytes(unmasked: bytes) -> bytes:
+    header = bytearray(unmasked[:2])
+    assert header[1] < 126  # assert that this is neither masked nor extended payload
+    header[1] |= 0b1000_0000
+    mask = secrets.token_bytes(4)
+    masked = bytes([x ^ mask[i % 4] for i, x in enumerate(unmasked[2:])])
+    return bytes(header + mask + masked)
+
+
+def test_masking():
+    m = masked(b"\x02\x03foo")
+    assert m == b"\x02\x83\x1c\x96\xd4\rz\xf9\xbb"
+    assert m == masked_bytes(b"\x02\x03foo")
+
+
+def test_upgrade(tctx):
+    """Test a HTTP -> WebSocket upgrade"""
+    tctx.server.address = ("example.com", 80)
+    tctx.server.state = ConnectionState.OPEN
+    http_flow = Placeholder(HTTPFlow)
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            Playbook(http.HttpLayer(tctx, HTTPMode.transparent))
+            >> DataReceived(tctx.client,
+                            b"GET / HTTP/1.1\r\n"
+                            b"Connection: upgrade\r\n"
+                            b"Upgrade: websocket\r\n"
+                            b"Sec-WebSocket-Version: 13\r\n"
+                            b"\r\n")
+            << http.HttpRequestHeadersHook(http_flow)
+            >> reply()
+            << http.HttpRequestHook(http_flow)
+            >> reply()
+            << SendData(tctx.server, b"GET / HTTP/1.1\r\n"
+                                     b"Connection: upgrade\r\n"
+                                     b"Upgrade: websocket\r\n"
+                                     b"Sec-WebSocket-Version: 13\r\n"
+                                     b"\r\n")
+            >> DataReceived(tctx.server, b"HTTP/1.1 101 Switching Protocols\r\n"
+                                         b"Upgrade: websocket\r\n"
+                                         b"Connection: Upgrade\r\n"
+                                         b"\r\n")
+            << http.HttpResponseHeadersHook(http_flow)
+            >> reply()
+            << http.HttpResponseHook(http_flow)
+            >> reply()
+            << SendData(tctx.client, b"HTTP/1.1 101 Switching Protocols\r\n"
+                                     b"Upgrade: websocket\r\n"
+                                     b"Connection: Upgrade\r\n"
+                                     b"\r\n")
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.client, masked_bytes(b"\x81\x0bhello world"))
+            << websocket.WebsocketMessageHook(flow)
+            >> reply()
+            << SendData(tctx.server, masked(b"\x81\x0bhello world"))
+            >> DataReceived(tctx.server, b"\x82\nhello back")
+            << websocket.WebsocketMessageHook(flow)
+            >> reply()
+            << SendData(tctx.client, b"\x82\nhello back")
+    )
+    assert flow().handshake_flow == http_flow()
+    assert len(flow().messages) == 2
+    assert flow().messages[0].content == "hello world"
+    assert flow().messages[0].from_client
+    assert flow().messages[1].content == b"hello back"
+    assert flow().messages[1].from_client is False
+
+
+@pytest.fixture()
+def ws_testdata(tctx):
+    tctx.server.address = ("example.com", 80)
+    tctx.server.state = ConnectionState.OPEN
+    flow = HTTPFlow(
+        tctx.client,
+        tctx.server
+    )
+    flow.request = Request.make("GET", "http://example.com/", headers={
+        "Connection": "upgrade",
+        "Upgrade": "websocket",
+        "Sec-WebSocket-Version": "13",
+    })
+    flow.response = Response.make(101, headers={
+        "Connection": "upgrade",
+        "Upgrade": "websocket",
+    })
+    return tctx, Playbook(websocket.WebsocketLayer(tctx, flow))
+
+
+def test_modify_message(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.server, b"\x81\x03foo")
+            << websocket.WebsocketMessageHook(flow)
+    )
+    flow().messages[-1].content = flow().messages[-1].content.replace("foo", "foobar")
+    assert (
+            playbook
+            >> reply()
+            << SendData(tctx.client, b"\x81\x06foobar")
+    )
+
+
+def test_drop_message(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.server, b"\x81\x03foo")
+            << websocket.WebsocketMessageHook(flow)
+    )
+    flow().messages[-1].content = ""
+    assert (
+            playbook
+            >> reply()
+            << None
+    )
+
+
+def test_fragmented(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.server, b"\x01\x03foo")
+            >> DataReceived(tctx.server, b"\x80\x03bar")
+            << websocket.WebsocketMessageHook(flow)
+            >> reply()
+            << SendData(tctx.client, b"\x01\x03foo")
+            << SendData(tctx.client, b"\x80\x03bar")
+    )
+    assert flow().messages[-1].content == "foobar"
+
+
+def test_protocol_error(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.server, b"\x01\x03foo")
+            >> DataReceived(tctx.server, b"\x02\x03bar")
+            << SendData(tctx.server, masked(b"\x88/\x03\xeaexpected CONTINUATION, got <Opcode.BINARY: 2>"))
+            << CloseConnection(tctx.server)
+            << SendData(tctx.client, b"\x88/\x03\xeaexpected CONTINUATION, got <Opcode.BINARY: 2>")
+            << CloseConnection(tctx.client)
+            << websocket.WebsocketErrorHook(flow)
+            >> reply()
+
+    )
+    assert not flow().messages
+
+
+def test_ping(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.client, masked_bytes(b"\x89\x11ping-with-payload"))
+            << Log("Received WebSocket ping from client (payload: b'ping-with-payload')")
+            << SendData(tctx.server, masked(b"\x89\x11ping-with-payload"))
+            >> DataReceived(tctx.server, b"\x8a\x11pong-with-payload")
+            << Log("Received WebSocket pong from server (payload: b'pong-with-payload')")
+            << SendData(tctx.client, b"\x8a\x11pong-with-payload")
+    )
+    assert not flow().messages
+
+
+def test_close_normal(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    masked_close = Placeholder(bytes)
+    close = Placeholder(bytes)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.client, masked_bytes(b"\x88\x00"))
+            << SendData(tctx.server, masked_close)
+            << CloseConnection(tctx.server)
+            << SendData(tctx.client, close)
+            << CloseConnection(tctx.client)
+            << websocket.WebsocketEndHook(flow)
+            >> reply()
+    )
+    # wsproto currently handles this inconsistently, see
+    # https://github.com/python-hyper/wsproto/pull/153/files
+    assert masked_close() == masked(b"\x88\x02\x03\xe8") or masked_close() == masked(b"\x88\x00")
+    assert close() == b"\x88\x02\x03\xe8" or close() == b"\x88\x00"
+
+    assert flow().close_code == 1005
+
+
+def test_close_disconnect(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> ConnectionClosed(tctx.server)
+            << CloseConnection(tctx.server)
+            << SendData(tctx.client, b"\x88\x02\x03\xe8")
+            << CloseConnection(tctx.client)
+            << websocket.WebsocketErrorHook(flow)
+            >> reply()
+            >> ConnectionClosed(tctx.client)
+    )
+    assert "ABNORMAL_CLOSURE" in flow().error.msg
+
+
+def test_close_error(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            >> DataReceived(tctx.server, b"\x88\x02\x0f\xa0")
+            << SendData(tctx.server, masked(b"\x88\x02\x0f\xa0"))
+            << CloseConnection(tctx.server)
+            << SendData(tctx.client, b"\x88\x02\x0f\xa0")
+            << CloseConnection(tctx.client)
+            << websocket.WebsocketErrorHook(flow)
+            >> reply()
+    )
+    assert "UNKNOWN_ERROR=4000" in flow().error.msg
+
+
+def test_deflate(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    # noinspection PyUnresolvedReferences
+    http_flow: HTTPFlow = playbook.layer.flow.handshake_flow
+    http_flow.response.headers["Sec-WebSocket-Extensions"] = "permessage-deflate; server_max_window_bits=10"
+    assert (
+            playbook
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+            # https://tools.ietf.org/html/rfc7692#section-7.2.3.1
+            >> DataReceived(tctx.server, bytes.fromhex("c1 07 f2 48 cd c9 c9 07 00"))
+            << websocket.WebsocketMessageHook(flow)
+            >> reply()
+            << SendData(tctx.client, bytes.fromhex("c1 07 f2 48 cd c9 c9 07 00"))
+    )
+    assert flow().messages[0].content == "Hello"
+
+
+def test_unknown_ext(ws_testdata):
+    tctx, playbook = ws_testdata
+    flow = Placeholder(WebSocketFlow)
+    # noinspection PyUnresolvedReferences
+    http_flow: HTTPFlow = playbook.layer.flow.handshake_flow
+    http_flow.response.headers["Sec-WebSocket-Extensions"] = "funky-bits; param=42"
+    assert (
+            playbook
+            << Log("Ignoring unknown WebSocket extension 'funky-bits'.")
+            << websocket.WebsocketStartHook(flow)
+            >> reply()
+    )
+
+
+def test_websocket_connection_repr(tctx):
+    ws = websocket.WebsocketConnection(wsproto.ConnectionType.SERVER, conn=tctx.client)
+    assert repr(ws)
+
+
+class TestFragmentizer:
+    def test_empty(self):
+        f = websocket.Fragmentizer([b"foo"])
+        assert list(f(b"")) == []
+
+    def test_keep_sizes(self):
+        f = websocket.Fragmentizer([b"foo", b"bar"])
+        assert list(f(b"foobaz")) == [
+            wsproto.events.Message(b"foo", message_finished=False),
+            wsproto.events.Message(b"baz", message_finished=True),
+        ]
+
+    def test_rechunk(self):
+        f = websocket.Fragmentizer([b"foo"])
+        f.FRAGMENT_SIZE = 4
+        assert list(f(b"foobar")) == [
+            wsproto.events.Message(b"foob", message_finished=False),
+            wsproto.events.Message(b"ar", message_finished=True),
+        ]

test/mitmproxy/proxy2/tutils.py

@@ -72,7 +72,7 @@ def _merge_sends(lst: typing.List[commands.Command], ignore_hooks: bool, ignore_
     current_send = None
     for x in lst:
         if isinstance(x, commands.SendData):
-            if current_send is None:
+            if current_send is None or current_send.connection != x.connection:
                 current_send = x
                 yield x
             else: