Fair grabbed six rebounds and helped turn back a late St. John's rally with three jumpers from the right baseline over the final 6:53.
Ennis, meanwhile, went 10-of-10 from the free throw line as the Orange (10-0) remained unbeaten.
Jerami Grant chipped in 14 points.
The Red Storm (6-3) dropped a ninth straight against Syracuse despite 21 points from D'Angelo Harrison.
Rysheed Jordan added 13 points and Jakarr Sampson provided 12 for St. John's.
Susan Sarandon 'very excited' about daughter's pregnancy
Teacher apologizes for showing sexual image of herself in class