guys stop. Sasuke isn't immune to IT. His Susanoo is his shield. If he is not inside his Susanoo then he too is susceptible. As for Naruto? Nobody is immune to IT except the one who castes it and I guess Black Zetsu and, by that extent Kaguya perhap? So no Naruto is not immune nor resistant either.
It's the ultimate genjutsu which requires a ton of prep and almost impossible requirements too achieve. That's why it's so OP.
his rinnegan is what helps him counter IT, bz clearly implies that and sasuke further states its possible for rinnegan to dispel a genjutsu formed with another rinnegan. he used soosano method so as to extend the protection to team 7 who would have been caught otherwise. Rinnegan counters IT so yes sasuke is immuneYeah I edited to include Black Zetsu. I don't know if the Rinnegan was what made Sasuke's Susanoo immune to IT but I don't find that far fetched. I figured it was his Rikudo chakra mixed in with his Susanoo but sure Ronnegan can counter it if that is the case. It doesn't make him immune though.
If you break his Susanoo while IT is active than Sauce is caught too. Fortunately getting through his Susanoo isn't an easy task unless you're Kaguya.