How to draw a square selection?

After picking the Rectangle mask tool, I tried dragging the cursor with the following keys/combinations TNA:



Ctrl + Shift

Ctrl + Alt

Shift + Alt

Ctrl + Shift + Alt

In CorelDRAW all I have to do is hold Ctrl while dragging the cursor to draw a regular square. And can do the same in Photo-Paint. But how to get the same constraint for a regular square selection?