Is it ever okay to ask your bf’s friends for information on your bf?

I’m suspecting my bf does drugs but he won’t say he does, he says he contacted his friend who sells for his other friend who doesn’t have the guy’s #. So hooking him up basically. I met some of his friends long before I met him. I’m talking about years (childhood) before. We’re not close but we’re also not just strangers. Should I ask them? Or should I just keep bugging my bf until he admits it. The only proof I have is the message he sent a friend asking for some & a picture of his friend doing it but from months ago. I don’t want to be with a person who does drugs. Idc if he knows or befriends drug dealers since they’re everywhere & even I have friends who are but I don’t want him doing it & he knows better than that.