Fluid on the firewall and/or around the outside of the master cylinder is a sure sign of leakage and the need for overhaul or replacement. Disassemble the cylinder and replace the rubber cups (if you can find them). You should clean everything well and hone the cylinder bore with a brake cylinder hone. Use only brake fluid to lubricate the hone stones, nothing petroleum based. Clean the cylinder again and reassemble, bleed the system and use top quality brake fluid. I've had good luck over the years rebuilding brake cylinders but parts are becoming rare so a replacement cylinder, if available, might be the way to go.
--
Roy Olson