PYTHON-4874 - Add KMS support for async Windows (mongodb#1939)

Author: NoahStapp

pymongo/network_layer.py

@@ -205,7 +205,7 @@ async def _async_sendall_ssl(
             total_sent += sent
 
     async def _async_receive_ssl(
-        conn: _sslConn, length: int, dummy: AbstractEventLoop
+        conn: _sslConn, length: int, dummy: AbstractEventLoop, once: Optional[bool] = False
     ) -> memoryview:
         mv = memoryview(bytearray(length))
         total_read = 0
@@ -215,6 +215,9 @@ async def _async_receive_ssl(
         while total_read < length:
             try:
                 read = conn.recv_into(mv[total_read:])
+                # KMS responses update their expected size after the first batch, stop reading after one loop
+                if once:
+                    return mv[:read]
                 if read == 0:
                     raise OSError("connection closed")
             except BLOCKING_IO_ERRORS: