custom stub not working

[johnRiddler]

I want to use a custom stub for example adding some functionality (like decrypting, ...) to the stub. but the default stub is base64 binary and obviously can't edit it. there is a folder named stub in the repo that contains the C source of a simple stub. I compiled it and gave it to amber but the generated file doesn't work. so I appreciate it if you give me the source of the b64 default stub or tell me why the C stub doesn't work.
thank you