It's a 4-chorder, I,IV, V, II. In C:

C - F C F C D G <(verse)

C - F C F C G C

F - C - G - C C7 <(chorus)

F - C - G - C -

G7 can be used instead of G, and D7 can be used instead of D. I worked this out in my head, and I sure hope I got it right, otherwise I'll look pretty foolish.