Adding support for gRPC messages

extender.py

@@ -2,6 +2,7 @@
 import subprocess
 import inspect
 import base64
+from struct import pack
 
 from burp import IBurpExtender
 from burp import IHttpListener
@@ -66,12 +67,11 @@ def json_to_protobuf_in_python3(self, json_body):
         except subprocess.CalledProcessError as e:
             print("Subprocess exited with error (status code {}):".format(e.returncode))
             print(e.output.decode())
-
         output = output.decode("utf-8").strip()
         protobuf = base64.b64decode(output)
 
         return protobuf
-
+    
     # Implement IHttpListener methods
     def processHttpMessage(self, toolFlag, messageIsRequest, messageInfo):
         # Only continue if the extension is enabled
@@ -103,7 +103,20 @@ def processHttpMessage(self, toolFlag, messageIsRequest, messageInfo):
         json_body = json.loads(body_string)
         # Convert the JSON to Protobuf
         protobuf = self.json_to_protobuf_in_python3(json_body)
+
+        #For header value that contains application/grpc content type
+        if any("application/grpc" in header.lower() for header in headers):
+            # Calculate the length of the serialized message.
+            message_length = len(protobuf)
+
+            # Create the gRPC message header.
+            # It consists of a compressed flag (0 for uncompressed) and the message length.
+            grpc_header = pack('>B', 0) + pack('>I', message_length)
+
+            # Concatenate the header and the serialized message.
+            protobuf = grpc_header + protobuf
+
         # Create a new HTTP message with the Protobuf body
         new_message = self._helpers.buildHttpMessage(headers, protobuf)
         # Update the request in the messageInfo object
-        messageInfo.setRequest(new_message)
+        messageInfo.setRequest(new_message)

json-generator.py

@@ -71,7 +71,7 @@ def generate_example_json(protobuf_module, message_name):
     set_placeholder_values(message)
 
     # Convert the protobuf message to a JSON string and return it
-    return MessageToJson(message, including_default_value_fields=True)
+    return MessageToJson(message, preserving_proto_field_name=True)
 
 def main():
     try: