Iran is in Group C along with Malaysia, Uzbekistan and China.
Here are the groups:
Group A: Thailand, Australia, Oman, Iraq
Group B: Vietnam, Japan, Qatar, UAE
Group C: Malaysia, Iran, Uzbekistan, China
Group D: Indonesia, South Korea , Saudi Arabia, Bahrain
The toughest group is Group D with two traditional powerhouses of South Korea and Saudi Arabia along with an emerging Bahrain as a strong Asian team. Groups A and B are equally strong in my opinion. Group C is the easiest group.
Here is the link to Asian Football Confederation's media release: