"And don't forget the Buran was virtually a carbon-copy of the Shuttle. Its engines--the RD-0120 (not to be confused with the RD-120) were copies of the SSME with a slightly larger nozzle and a slightly lower thrust. The Russians filed Freedom of Information Act requests (through their embassy) and were given the blueprints, reports, and other documents."
This applies to the vehicle, tiles, tankage, and all other major components, not just the engines.
--Boris