Validate chunk size in Chunked Encoding are HEXDIG

RFC7230 states that a chunk-size should be 1*HEXDIG, this is now
validated before passing the resulting string to int() which would also
parse other formats for hex, such as: `0x01` as `1` and `+0x01` as `1`.
This would lead to a potential for a frontend proxy server and waitress
to disagree on where a chunk started and ended, thereby potentially
leading to request smuggling.

With the increased validation if the size is not just hex digits,
Waitress now returns a Bad Request and stops processing the request.

2 files changed, 34 insertions, 0 deletions

diff --git a/tests/test_functional.py b/tests/test_functional.py
index 9e33fc0..60eb24a 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -364,6 +364,28 @@ class EchoTests:
             self.send_check_error(to_send)
             self.assertRaises(ConnectionClosed, read_http, fp)
 
+    def test_broken_chunked_encoding_invalid_hex(self):
+        control_line = b"0x20\r\n"  # 20 hex = 32 dec
+        s = b"This string has 32 characters.\r\n"
+        to_send = b"GET / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n"
+        to_send += control_line + s + b"\r\n"
+        self.connect()
+        self.sock.send(to_send)
+        with self.sock.makefile("rb", 0) as fp:
+            line, headers, response_body = read_http(fp)
+            self.assertline(line, "400", "Bad Request", "HTTP/1.1")
+            cl = int(headers["content-length"])
+            self.assertEqual(cl, len(response_body))
+            self.assertIn(b"Invalid chunk size", response_body)
+            self.assertEqual(
+                sorted(headers.keys()),
+                ["connection", "content-length", "content-type", "date", "server"],
+            )
+            self.assertEqual(headers["content-type"], "text/plain")
+            # connection has been closed
+            self.send_check_error(to_send)
+            self.assertRaises(ConnectionClosed, read_http, fp)
+
     def test_broken_chunked_encoding_invalid_extension(self):
         control_line = b"20;invalid=\r\n"  # 20 hex = 32 dec
         s = b"This string has 32 characters.\r\n"
diff --git a/tests/test_receiver.py b/tests/test_receiver.py
index a3b6f99..8e43cc8 100644
--- a/tests/test_receiver.py
+++ b/tests/test_receiver.py
@@ -262,6 +262,18 @@ class TestChunkedReceiverParametrized:
         assert result == len(data)
         assert inst.error == None
 
+    @pytest.mark.parametrize("invalid_size", [b"0x04", b"+0x04", b"x04", b"+04"])
+    def test_received_invalid_size(self, invalid_size):
+        from waitress.utilities import BadRequest
+
+        buf = DummyBuffer()
+        inst = self._makeOne(buf)
+        data = invalid_size + b"\r\ntest\r\n"
+        result = inst.received(data)
+        assert result == len(data)
+        assert inst.error.__class__ == BadRequest
+        assert inst.error.body == "Invalid chunk size"
+
 
 class DummyBuffer:
     def __init__(self, data=None):