  The latest years have seen steady progresses in WIMP dark matter (DM)
searches, with hints of possible signals suggested by both direct and indirect
detection experiments. Antiprotons can play a key role validating those
interpretations since they are copiously produced by WIMP annihilations in the
Galactic halo, and the secondary antiproton background produced by Cosmic Ray
(CR) interactions is predicted with fair accuracy and matches the observed
spectrum very well. Using the publicly available numerical DRAGON code, we
reconsider antiprotons as a tool to constrain DM models discussing its power
and limitations. We provide updated constraints on a wide class of annihilating
DM models by comparing our predictions against the most up-to-date ap
measurements, taking also into account the latest spectral information on the
p, He and other CR nuclei fluxes. Doing that, we probe carefully the
uncertainties associated to both secondary and DM originated antiprotons, by
using a variety of distinctively different assumptions for the propagation of
CRs and for the DM distribution in the Galaxy. We find that the impact of the
astrophysical uncertainties on constraining the DM properties can be much
stronger, up to a factor of ~50, than the one due to uncertainties on the DM
distribution (~2-6). Remarkably, even reducing the uncertainties on the
propagation parameters derived by local observables, non-local effects can
still change DM model constraints even by 50%. Nevertheless, current ap data
place tight constraints on DM models, excluding some of those suggested in
connection with indirect and direct searches. Finally we discuss the power of
upcoming CR spectral data from the AMS-02 observatory to drastically reduce the
uncertainties discussed in this paper and estimate the expected sensitivity of
this instrument to some sets of DM models.
