Iirc, the middle node never has access to the data being sent.

I think only the last node might, and that is because they have to be able to send and receive it, and if the website you are connecting to doesn't support ssl or anything, then there's no way the exit node can send the information it needs to send , without having access to it.

But I think the entry and middle node have no information about the content (other than some bounds on its length)