  We give a microscopic two dimensional ${\cal N}=(2,2)$ gauge theory
description of arbitrary M2-branes ending on $N_f$ M5-branes wrapping a
punctured Riemann surface. These realize surface operators in four dimensional
${\cal N}=2$ field theories. We show that the expectation value of these
surface operators on the sphere is captured by a Toda CFT correlation function
in the presence of an additional degenerate vertex operator labelled by a
representation ${\cal R}$ of $SU(N_f)$, which also labels M2-branes ending on
M5-branes. We prove that symmetries of Toda CFT correlators provide a geometric
realization of dualities between two dimensional gauge theories, including
${\cal N}=(2,2)$ analogues of Seiberg and Kutasov--Schwimmer dualities. As a
bonus, we find new explicit conformal blocks, braiding matrices, and fusion
rules in Toda CFT.
