By Caroline Stauffer SAO PAULO (Reuters) - A federal judge in Brazil overseeing a sweeping corruption investigation said on Tuesday there were signs that President Dilma Rousseff's former chief of staff had received bribes. Judge Sergio Moro asked the Supreme Court to authorize an investigation into whether a graft case involving Brazil's planning ministry may have benefited Gleisi Hoffmann, now a senator and still personally close to the president. Hoffmann has not been formally charged with any wrongdoing.