Was the Soviet Union an ally of the U.S.A. during the Winter War?

I know they were an ally in World War II, but I don’t know if they became an ally before or after the Winter War. I believe that the Soviet Union fought for unjust reasons in the Winter War and that Finland fought for just reasons. I want the question above answered because I want to know whether I can say that ‘I believe all military operations in the past 100 years by the U.S. and its allies were justified’ or not. If the Soviet Union was an ally during the Winter War then it would be the only exception.