Hi Bilal,
With console access to the server, try a code search like this:
frappe@ubuntu:~/frappe-bench$ find . -name '*.py' | xargs grep 'permission'
The above expression reports all the Python files that contain ‘permission’.
To view the files, use Unix less or an editor, or from a web browser view the files on github.com
More search examples here Where do I go to setup Backups in new v8 - #19 by clarkej