How did Sasuke get his curse mark?

Orochimaru gave it to him. He bit Sasuke's neck in the Forest of Death but at the time Sasuke didn't want it. Orochimaru gave it to him to give Sasuke a LITTLE taste of Orochimaru's power. When Sasuke started using the curse mark's power he absolutely loved it and that is why he went to Orochimaru in the first place (WHY OH WHY DID IT HAVE TO HAPPEN?

Yes, that is true butt for those who don't know the only reason that Sasuke went to him for the power is to get enough skill and power to kill his brother Itachi Uchia who is very strong and Orochimaru wants his body because he needs it for his immortality Jutsu which he just switches body's, but what I didn't get is when old man Hokaga died, he made sure Orochimaru couldn't use his hands butt still he can?

Sasuke is a backstabber