While I cannot speak to during the war, afterwards obviously many documents were collected and cataloged, including the entire complete minutes from the Wannsee Conference, where the Final Solution as first laid out at a large staff meeting headed by Heydrech and Eichmann.

English Translation: http://avalon.law.yale.edu/imt/wannsee.asp

Not necessarily after we broke the codes but it was talked about flat out bombing the concentration camps in order to stop the killings that were taking place there. Churchill also discussed bombing them as well. So yes the Allies certainly knew about them prior to their liberation.

Einsat Reinhard was also uncoded by the Allies but they had no idea what the operation was truly about.