Add support for HTTP/1.0 proxies.

It is legal to answer an HTTP/1.1 request with an HTTP/1.0 response.

Fix #1609.

Author: aaugustin

Diff for: docs/project/changelog.rst

@@ -32,6 +32,11 @@ notice.
 
 *In development*
 
+Improvements
+............
+
+* Added support for HTTP/1.0 proxies.
+
 15.0.1
 ------
 

Diff for: src/websockets/asyncio/client.py

@@ -755,6 +755,7 @@ def __init__(
             self.reader.read_exact,
             self.reader.read_to_eof,
             include_body=False,
+            allow_http10=True,
         )
 
         loop = asyncio.get_running_loop()

Diff for: src/websockets/http11.py

@@ -214,6 +214,7 @@ def parse(
         read_exact: Callable[[int], Generator[None, None, bytes]],
         read_to_eof: Callable[[int], Generator[None, None, bytes]],
         include_body: bool = True,
+        allow_http10: bool = False,
     ) -> Generator[None, None, Response]:
         """
         Parse a WebSocket handshake response.
@@ -249,10 +250,17 @@ def parse(
             protocol, raw_status_code, raw_reason = status_line.split(b" ", 2)
         except ValueError:  # not enough values to unpack (expected 3, got 1-2)
             raise ValueError(f"invalid HTTP status line: {d(status_line)}") from None
-        if protocol != b"HTTP/1.1":
-            raise ValueError(
-                f"unsupported protocol; expected HTTP/1.1: {d(status_line)}"
-            )
+        if allow_http10:  # some proxies still use HTTP/1.0
+            if protocol not in [b"HTTP/1.1", b"HTTP/1.0"]:
+                raise ValueError(
+                    f"unsupported protocol; expected HTTP/1.1 or HTTP/1.0: "
+                    f"{d(status_line)}"
+                )
+        else:
+            if protocol != b"HTTP/1.1":
+                raise ValueError(
+                    f"unsupported protocol; expected HTTP/1.1: {d(status_line)}"
+                )
         try:
             status_code = int(raw_status_code)
         except ValueError:  # invalid literal for int() with base 10

Diff for: src/websockets/sync/client.py

@@ -499,6 +499,7 @@ def read_connect_response(sock: socket.socket, deadline: Deadline) -> Response:
         reader.read_exact,
         reader.read_to_eof,
         include_body=False,
+        allow_http10=True,
     )
     try:
         while True:

Diff for: tests/test_http11.py

@@ -333,6 +333,23 @@ def test_parse_without_body(self):
         response = self.assertGeneratorReturns(self.parse(include_body=False))
         self.assertEqual(response.body, b"")
 
+    def test_parse_http10(self):
+        self.reader.feed_data(b"HTTP/1.0 200 OK\r\n\r\n")
+        response = self.assertGeneratorReturns(self.parse(allow_http10=True))
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.reason_phrase, "OK")
+        self.assertEqual(response.body, b"")
+
+    def test_parse_http10_unsupported_protocol(self):
+        self.reader.feed_data(b"HTTP/1.2 400 Bad Request\r\n\r\n")
+        with self.assertRaises(ValueError) as raised:
+            next(self.parse(allow_http10=True))
+        self.assertEqual(
+            str(raised.exception),
+            "unsupported protocol; expected HTTP/1.1 or HTTP/1.0: "
+            "HTTP/1.2 400 Bad Request",
+        )
+
     def test_serialize(self):
         # Example from the protocol overview in RFC 6455
         response = Response(