Board Thread:Theories and Speculation/@comment-28819877-20170515143845/@comment-734582-20170515152156

Ravenlot 27 wrote: Well, at least Sharingan is surely required, otherwise Naruto would've awakened his own Rinnegan after receiving Hagoromo's chakra had it been the only requiremed. I don't think we should attach much value to Hagoromo's shenanigans. The guy created entire new entities with unique powers and personalities. We saw him do stuff previously thought impossible. Ensuring that Naruto doesn't get Rinnegan (and Sasuke only one) is pretty much one of the least insane Hagoromo feats.

That being said, Naruto and Sasuke didn't 'just' get some chakra, because else Sasuke would have twin Rinnegan just like Naruto. There are multiple explanations, but the simplest is that Naruto doesn't have Indra flesh. He cooperated with Sasuke with Majestic Attire which likely mixed some chakra, and together with the Beasts that recreated Hagoromo's chakra, leading to the meeting. Sasuke similarly met the requirements by being touched by Naruto for FTG purposes. Not nearly enough for any genetic changes (we saw with Madara that even implanted flesh will take a lot of time to evolve Hagoromo's powers), but enough to meet the conditions. This is unlike Madara, who didn't have the three chakras to bring about a meeting with Hagoromo. Sasuke also got some Hashi (or more probable: Zetsu) cells, which meant that at the moment of restoration both exactly met their requirements.

Also note that both probably met the requirements for their respective powers, since Sasuke has Hashi cells + Indra chakra and Naruto has Pseudojuubi + Sage Mode.