Iran has definitely provided weapons either directly or indirectly to Hamas and Hezbollah. That being said neither the US nor Israel believe that Iran had anything to do with this operation, despite what some senior (IIRC) Hamas officials have said.

That Iran denies operational involvement is not surprising. The Iranian government is (IMO) not the most trust-worthy source, but their denial does carry at least some weight.

Based on the above, I think it is incorrect to call this "Iranian state sponsored terrorism."