The Constitution itself is silent on the subject, but since secession was an established right, it didnt have to be reaffirmed. More telling still, even the bitterest opponents of the Constitution never accused it of denying the right of secession. Three states ratified the Constitution with the provision that they could later secede if they chose; the other ten states accepted this condition as valid.
I believe New York was one of the states that reserved all rights of secession, and the Federalists HAD to accept it, because they needed New York.