By 1945, the Holocaust and it's various instruments was an open secret in Germany. Everyone knew that that the Jews, Homosexuals, Communists etc who were being deported in vast quantities to the East were not coming back. However, most Germans who were not directly involved with the process were appalled by the scale of the atrocities committed in the camps when being toured around them at the end of the war.

In regards to the atrocities committed closer to the front, as the SS Einsatzgruppen (task groups) (the Wehrmacht also are responsible for war crimes, but we'll focus on the SS here) swept through the occupied territories, most notably in Russia, the nature of their method of "liquidation"(or even more vague "evacuation") which can hardly be described as subtle led to rumors circulating among soldiers and civilians alike. Eventually in some shape or form, these rumors made there back to the Old Reich.

So too say that your average German was completely oblivious to the various atrocities the Third Reich committed would not be true, but it's certainly possible that he/she could have been in denial or skeptical is also a possibility, and this was common enough until the sheer volume of evidence began to surface at the end of the war.

(Sources The Third Reich at War by Richard.J.Evans)