Add max_receive_message_length param

README.md

@@ -91,6 +91,16 @@ This new version comes with flexibility to use any prefix for the server URLs an
 
 If you want to use the server and clients of v5, then use the [0.0.1](https://github.com/verloop/twirpy/releases/tag/0.0.1) release.
 
+### Message Body Length
+
+Currently, message body length limit is set to 100kb, you can override this by passing `max_receive_message_length` to `TwirpASGIApp` constructor.
+
+```python
+# this sets max message length to be 10 bytes
+app = TwirpASGIApp(max_receive_message_length=10)
+
+```
+
 ## Support and community
 Python: [#twirp](https://python-community.slack.com/messages/twirp). Join Python community slack [here](https://pythoncommunity.herokuapp.com)
 

twirp/asgi.py

@@ -58,6 +58,7 @@ async def __call__(self, scope, receive, send):
 
             endpoint = self._get_endpoint(scope['path'])
             headers = {k.decode('utf-8'): v.decode('utf-8') for (k,v) in scope['headers']}
+            self.validate_content_length(headers=headers)
             encoder, decoder = self._get_encoder_decoder(endpoint, headers)
 
             # add headers from request into context
@@ -157,4 +158,27 @@ async def _recv_all(self, receive):
             message = await receive()
             body += message.get('body', b'')
             more_body = message.get('more_body', False)
+
+            # the body length exceeded than the size set, raise a valid exception
+            # so that proper error is returned to the client
+            if self._max_receive_message_length < len(body):
+                raise exceptions.TwirpServerException(
+                    code=errors.Errors.InvalidArgument,
+                    message=F"message body exceeds the specified length of {self._max_receive_message_length} bytes"
+                )
+
         return body
+
+    # we will check content-length header value and make sure it is
+    # below the limit set
+    def validate_content_length(self, headers):
+        try:
+            content_length = int(headers.get('content-length'))
+        except (ValueError, TypeError):
+            return
+
+        if self._max_receive_message_length < content_length:
+            raise exceptions.TwirpServerException(
+                code=errors.Errors.InvalidArgument,
+                message=F"message body exceeds the specified length of {self._max_receive_message_length} bytes"
+            )

twirp/base.py

@@ -18,9 +18,10 @@
 
 
 class TwirpBaseApp(object):
-    def __init__(self, *middlewares, hook=None, prefix="", ctx_class=None):
+    def __init__(self, *middlewares, hook=None, prefix="", max_receive_message_length=1024*100*100, ctx_class=None):
         self._prefix = prefix
         self._services = {}
+        self._max_receive_message_length = max_receive_message_length
         if ctx_class is None:
             ctx_class = context.Context
         assert issubclass(ctx_class, context.Context)