How did Orochimaru know Obito's true identity?

[Zol]

He already knows that Tobi isn't Madara, not that big of a stretch.

The big question here is does Sasuke know that Tobi was Obito the entire time?

That's no big question at all. He didn't know.

 

[Zol]

Thats not necessarily the case. One, we know during their time working together Tobi switched mask. Also, Orochimaru seemed to have figured this oit long ago. Tobi constantly cursed his name for a reason

Obito switched masks while Kabuto caught Yamato...

 

[vasu 32]

listen,he learned on ariving at the battle field off screen via hokages or sasuke told him,as sasuke hypnotysed zetsu clone and got entire information.

 

[Lightbringer]

did people forget that Ino connected everyone's minds together with her jutsu?

 

[Kanaxai]

Orochimaru is the Aizen of Bleach.

You mean Aizen of Naruto.

 

[johnny335704]

May Be Oro came to know about it from combination of "information retrieved from Kabuto's mind" & "recovered Kages on the way or when Oro arrived to help injured Kages".

 

[itach15]

Orochimaru > Shinju, Sage of the Six Paths ,Kaguya ...U_U