  We calculate the leading-twist, helicity-independent generalized parton
distributions (GPDs) of the proton, at finite skewness, in the
Nambu--Jona-Lasinio (NJL) model of quantum chomodynamics (QCD). The NJL model
reproduces low-energy characteristics of QCD, including dynamical chiral
symmetry breaking (DCSB). The proton bound-state amplitude is solved for using
the Faddeev equation in a quark-diquark approximation, including both dynamical
scalar and axial vector diquarks. GPDs are calculated using a dressed non-local
correlator, consistent with DCSB, which is obtained by solving a Bethe-Salpeter
equation. The model and approximations used observe Lorentz covariance, and as
a consequence the GPDs obey polynomiality sum rules. Extractions of
electromagnetic and gravitational form factors are performed. We find a D-term
of $-1.08$ when the non-local correlator is properly dressed, and $0.85$ when
the bare correlator is used instead, suggesting that within this framework
proton stability requires the constituent quarks to be dressed consistently
with DCSB. We also find that the anomalous gravitomagnetic vanishes, as
required by Poincar\'{e} symmetry.
