Are Naruto and Gaara friends

Yes, they are. It happened after their battle when they were 12 years old and Naruto knocked some sense into Gaara. Since then, Kishimoto (the manga's author) revealed a lot of information about Naruto and Gaara that made them have even more and more in common, and not just for being Jinchuuriki. Gaara has also adapted Naruto's philosophy and seems to be having the same morality/ethic/code as him even though they don't really get to see and communicate with each other very often. They're just "natural" friends, so to say.