i wouldent say its a bypass but more of a glitch, homefront is extremley glitched out but i never bought the online pass, but if you kill someone who has a glitched account you will rank up past 5 and to another rank and i guess you are trying to hit 45 so what happend to me is i killed a few people and restarted the game and i was at rank 30 but i kept online on and played till i hit 45 non stop and i got the trophy. or you could just suck your pride up and spend the 5$ on the pass.

Oh and a little advice, if you are going for the plat, i HIGHLY advise you to copy your save file EVERY time you quit playing to protect you from losing your online stats. so make a backup file. i actually olmost lost all of my stats when i was going for plat.