Fix non-ASCII headers in the legacy HTTP parser

docs/project/changelog.rst

@@ -44,6 +44,12 @@ Improvements
 * :func:`~asyncio.client.connect` now closes connections with close code 1011
   (internal error) when exiting the context manager with an exception.
 
+Bug fixes
+.........
+
+* Fixed a regression from 16.1 where the legacy implementation rejected
+  non-ASCII headers.
+
 .. _17.1:
 
 17.1

src/websockets/legacy/http.py

@@ -175,7 +175,9 @@ async def read_headers(stream: asyncio.StreamReader) -> Headers:
 
         name = raw_name.decode("ascii")  # guaranteed to be ASCII at this point
         value = raw_value.decode("ascii", "surrogateescape")
-        headers[name] = value
+
+        # Since we just validated raw_value, we don't need to revalidate it.
+        headers.set_insecure(name, value)
 
     else:
         raise SecurityError("too many HTTP headers")

src/websockets/sync/server.py

@@ -544,8 +544,8 @@ def handler(websocket):
         with serve(handler, ...) as server:
             server.serve_forever()
 
-        To stop the server gracefully, call its :meth:`~Server.shutdown` method
-        from another thread.
+    To stop the server gracefully, call its :meth:`~Server.shutdown` method from
+    another thread.
 
     Args:
         handler: Connection handler. It receives the WebSocket connection,

tests/legacy/test_http.py

@@ -152,12 +152,18 @@ async def test_read_response_invalid_header(self):
             "invalid HTTP header line: Oops",
         )
 
-    async def test_header_name(self):
+    async def test_iso_8859_1_header_value(self):
+        self.stream.feed_data(b"X-Drink: caf\xe9\r\n\r\n")
+        headers = await read_headers(self.stream)
+        # Non-ASCII characters are represented with surrogate escapes.
+        self.assertEqual(headers["X-Drink"], "caf\udce9")
+
+    async def test_invalid_header_name(self):
         self.stream.feed_data(b"foo bar: baz qux\r\n\r\n")
         with self.assertRaises(ValueError):
             await read_headers(self.stream)
 
-    async def test_header_value(self):
+    async def test_invalid_header_value(self):
         self.stream.feed_data(b"foo: \x00\x00\x0f\r\n\r\n")
         with self.assertRaises(ValueError):
             await read_headers(self.stream)