How to calibrate current transformer such as SCT-013 without having to actually generate the actual current?
All equipment i have access to is a DC bench power supply, Digital
  Oscilloscope, and a function generator.


Use your signal generator set at 50 Hz or 60 Hz and, through the primary hole wind ten turns (or more) but note the number. Drive current through those ten turns and monitor that current using your multimeter. If you can get 100 mA RMS through 20 turns, that's equivalent to 2 A RMS in a single primary wire. If that isn't enough, wind more primary turns (say 100) or, build a little DC power amplifier to produce more current into the home-spun winding.