Refactor forwarded header handling into opt-in kaya-forwarded package with trusted CIDRs

packages/kaya-core/src/kaya/core/__init__.py

@@ -1,6 +1,6 @@
 from ._app import AbstractKayaApp, KayaApp
 from ._http_method import HttpMethod
-from ._http_context import HttpContext, resolve_client
+from ._http_context import HttpContext
 from ._mixin import KayaMixin
 from ._tree import Tree, PathIterator
 from ._path_handler import PathHandler, Matches
@@ -13,7 +13,6 @@ __all__ = [
     'KayaApp',
     'KayaMixin',
     'HttpContext',
-    'resolve_client',
     'Tree',
     'PathHandler',
     'Matches',

packages/kaya-core/src/kaya/core/_asgi.py

@@ -16,7 +16,7 @@ from typing import (
 from pwo import Maybe
 from pathlib import Path
 from ._http_method import HttpMethod
-from ._http_context import HttpContext, resolve_client
+from ._http_context import HttpContext
 from ._websocket import WebSocket, WebSocketMessage
 from ._types import StrOrStrings
 from ._types.asgi import HTTPScope, WebSocketScope
@@ -84,9 +84,9 @@ class AsgiContext(HttpContext):
         self.query_string = scope['query_string'].decode()
         self.method = HttpMethod(scope['method'])
         self.scheme = scope.get('scheme', 'http')
-        self.headers = decode_headers(scope['headers'])
-        self.client = resolve_client(self.headers, scope['client'])
+        self.client = scope['client']
         self.server = scope['server']
+        self.headers = decode_headers(scope['headers'])
         self.request_body = request_body_iterator
         self.session = (scope.get('state') or {}).get('kaya_session')
 
@@ -169,9 +169,9 @@ class AsgiWebSocket(WebSocket):
         self.path = scope['path']
         self.query_string = scope['query_string'].decode()
         self.scheme = scope.get('scheme', 'ws')
-        self.headers = decode_headers(scope['headers'])
-        self.client = resolve_client(self.headers, scope['client'])
+        self.client = scope['client']
         self.server = scope['server']
+        self.headers = decode_headers(scope['headers'])
 
     async def accept(self, headers: Optional[Mapping[str, StrOrStrings]] = None) -> None:
         message: Dict[str, Any] = {'type': 'websocket.accept'}

packages/kaya-core/src/kaya/core/_http_context.py

@@ -16,83 +16,6 @@ from ._http_method import HttpMethod
 from ._types.base import StrOrStrings
 
 
-def _split_host_port(value: str) -> Tuple[str, Optional[int]]:
-    if value.startswith('['):
-        # bracketed IPv6 address, optionally followed by :port
-        closing = value.find(']')
-        if closing == -1:
-            return value, None
-        host = value[1:closing]
-        rest = value[closing + 1:]
-        if rest.startswith(':'):
-            try:
-                return host, int(rest[1:])
-            except ValueError:
-                return host, None
-        return host, None
-    if value.count(':') == 1:
-        host, _, port_str = value.rpartition(':')
-        try:
-            return host, int(port_str)
-        except ValueError:
-            return value, None
-    return value, None
-
-
-def _first_header_value(headers: Mapping[str, Sequence[str]], name: str) -> Optional[str]:
-    values = headers.get(name)
-    if not values:
-        return None
-    first = values[0].split(',')[0].strip()
-    return first or None
-
-
-def resolve_client(headers: Mapping[str, Sequence[str]],
-                   client: Optional[Tuple[str, int]]) -> Optional[Tuple[str, int]]:
-    """
-    Resolve the client (host, port) pair, honoring forwarded headers.
-
-    Resolution order:
-      1. the ``for=`` parameter of the first entry of the RFC 7239 ``Forwarded`` header
-         (a ``:port`` suffix, if present, also populates the port)
-      2. the first entry of ``X-Forwarded-For``
-      3. the first entry of ``X-Forwarded-Host``
-      4. the socket peer address (``client``), returned unchanged
-
-    In the ``X-Forwarded-*`` cases the port is taken from ``X-Forwarded-Port``
-    when present and valid, otherwise the socket port is kept.
-    """
-    socket_port = client[1] if client is not None else 0
-
-    forwarded_values = headers.get('forwarded')
-    if forwarded_values:
-        for raw_value in forwarded_values:
-            first_entry = raw_value.split(',')[0]
-            for param in first_entry.split(';'):
-                key, sep, value = param.partition('=')
-                if sep and key.strip().lower() == 'for':
-                    for_value = value.strip().strip('"')
-                    if for_value and for_value.lower() != 'unknown':
-                        forwarded_host, forwarded_port = _split_host_port(for_value)
-                        if forwarded_host:
-                            return (forwarded_host,
-                                    forwarded_port if forwarded_port is not None else socket_port)
-
-    for header_name in ('x-forwarded-for', 'x-forwarded-host'):
-        host = _first_header_value(headers, header_name)
-        if host is not None:
-            port = socket_port
-            x_forwarded_port = _first_header_value(headers, 'x-forwarded-port')
-            if x_forwarded_port is not None:
-                try:
-                    port = int(x_forwarded_port)
-                except ValueError:
-                    pass
-            return host, port
-
-    return client
-
-
 class HttpContext(ABC):
     pathsend: bool
     receive: Callable[[], Awaitable[Any]]

packages/kaya-core/tests/test_asgi.py

@@ -62,11 +62,6 @@ class AsgiTest(unittest.TestCase):
         async def handle_request(ctx: HttpContext, _: List[str]) -> None:
             await ctx.stream_body(200, (chunk async for chunk in ctx.request_body))
 
-        @self.app.GET('/client-ip')
-        async def handle_request(ctx: HttpContext) -> None:
-            host, port = ctx.client if ctx.client is not None else (None, None)
-            await ctx.send_str(200, json.dumps({'host': host, 'port': port}))
-
     @async_test
     async def test_hello(self):
         transport = httpx.ASGITransport(app=self.app)
@@ -195,60 +190,6 @@ class AsgiTest(unittest.TestCase):
                 'employee_id': 101325
             }, response)
 
-    @async_test
-    async def test_client_ip_forwarded(self):
-        transport = httpx.ASGITransport(app=self.app)
-
-        async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as client:
-            # socket peer, no forwarded headers
-            r = await client.get("/client-ip")
-            socket_client = json.loads(r.text)
-            self.assertEqual('127.0.0.1', socket_client['host'])
-
-            # RFC 7239 Forwarded header, with port
-            r = await client.get("/client-ip", headers={'Forwarded': 'for=203.0.113.5:1234'})
-            self.assertEqual({'host': '203.0.113.5', 'port': 1234}, json.loads(r.text))
-
-            # RFC 7239 Forwarded header, bracketed IPv6 with port
-            r = await client.get("/client-ip", headers={'Forwarded': 'for="[2001:db8::1]:4711"'})
-            self.assertEqual({'host': '2001:db8::1', 'port': 4711}, json.loads(r.text))
-
-            # RFC 7239 Forwarded header without port keeps the socket port
-            r = await client.get("/client-ip", headers={'Forwarded': 'for=203.0.113.5'})
-            self.assertEqual({'host': '203.0.113.5', 'port': socket_client['port']}, json.loads(r.text))
-
-            # Forwarded with for=unknown falls through to X-Forwarded-For
-            r = await client.get("/client-ip", headers={
-                'Forwarded': 'for=unknown',
-                'X-Forwarded-For': '198.51.100.7',
-            })
-            self.assertEqual('198.51.100.7', json.loads(r.text)['host'])
-
-            # Forwarded takes precedence over X-Forwarded-For
-            r = await client.get("/client-ip", headers={
-                'Forwarded': 'for=203.0.113.5',
-                'X-Forwarded-For': '198.51.100.7',
-            })
-            self.assertEqual('203.0.113.5', json.loads(r.text)['host'])
-
-            # X-Forwarded-For: first entry of the chain, port from X-Forwarded-Port
-            r = await client.get("/client-ip", headers={
-                'X-Forwarded-For': '203.0.113.5, 70.41.3.18',
-                'X-Forwarded-Port': '8443',
-            })
-            self.assertEqual({'host': '203.0.113.5', 'port': 8443}, json.loads(r.text))
-
-            # X-Forwarded-Host fallback
-            r = await client.get("/client-ip", headers={'X-Forwarded-Host': '198.51.100.7'})
-            self.assertEqual('198.51.100.7', json.loads(r.text)['host'])
-
-            # invalid X-Forwarded-Port is ignored, socket port is kept
-            r = await client.get("/client-ip", headers={
-                'X-Forwarded-For': '203.0.113.5',
-                'X-Forwarded-Port': 'not-a-port',
-            })
-            self.assertEqual({'host': '203.0.113.5', 'port': socket_client['port']}, json.loads(r.text))
-
     @async_test
     async def test_nested_param_routes(self):
         app = KayaApp()

packages/kaya-core/tests/test_websocket.py

@@ -132,37 +132,6 @@ class WebSocketTest(unittest.TestCase):
         self.assertEqual(1, len(sent_messages))
         self.assertEqual({'type': 'websocket.accept'}, sent_messages[0])
 
-    @async_test
-    async def test_client_forwarded_header(self):
-        async def send(message):
-            pass
-
-        async def receive():
-            return {'type': 'websocket.connect'}
-
-        scope = {
-            'type': 'websocket',
-            'path': '/echo',
-            'query_string': b'',
-            'scheme': 'ws',
-            'client': ('127.0.0.1', 12345),
-            'server': ('127.0.0.1', 80),
-            'headers': [(b'forwarded', b'for=203.0.113.5:1234')],
-        }
-        ws = AsgiWebSocket(scope, receive, send)
-        self.assertEqual(('203.0.113.5', 1234), ws.client)
-
-        scope['headers'] = [
-            (b'x-forwarded-for', b'203.0.113.5, 70.41.3.18'),
-            (b'x-forwarded-port', b'8443'),
-        ]
-        ws = AsgiWebSocket(scope, receive, send)
-        self.assertEqual(('203.0.113.5', 8443), ws.client)
-
-        scope['headers'] = []
-        ws = AsgiWebSocket(scope, receive, send)
-        self.assertEqual(('127.0.0.1', 12345), ws.client)
-
     @async_test
     async def test_websocket_scope_without_scheme(self):
         # Daphne omits the optional `scheme` key from websocket scopes.