Is is legal to convert iTunes' rental movies?

Recently I saw my freind using a software to convert iTunes' rental movies to MP4 format. It seems that he could keep them forever. But is it ok to convert these rental things? Tell me if you know, please.
Asked Mar 18, 2016

TIP: If it's not your answer to this question, please click "Leave a Comment" button under the question to communicate with the question owner.