He seemed pretty suspicious and be stated that he never considered Madara an ally. Which is why I think Obito knows that Madara is behind it. It's clear that Obito had absolutely no intentions to revive Madara which is why he fixated more on Sasuke. I believe it will ultimately come down to Madara VS Obito for the Juubi's power.
Do you think Obito knows Madara could have been behind Rin's death?