During my last internship, I took an open source tool and enhanced it as a part of my project. Because of my growing interest in that tool, I took it home and added some more functionalities to make it more useful for others outside and then thought of publishing it.

The original source code is available in public domain without any restrictions, but since I worked on this tool during my internship, I wanted to know whether I have to take permission from my employer before publishing it.

Although I want to publish it, my mind tells me NO, as the code is now a property of my employer.

Edit 1:

This is what the original tool writer says about the code: 
"This code is released into the public domain without restriction"