Goldman Sachs Group, already under fire for its actions leading up to the financial crisis, came under attack from a federal commission that accused it of refusing to divulge information, including documents detailing its controversial bets on the mortgage market. Saying it had been stonewalled, the federal commission investigating the financial crisis on Monday took the unusual step of issuing a subpoena to Goldman that demanded information about the investment bank’s role before and during the mortgage meltdown and credit crunch.