It's unclear, and information is still coming out about U.S. involvement in Afghanistan.

One of the most recent sources has been the memoir of Robert Gates, From the Shadows. Gates worked for the CIA in late 1979 through 1989, until he moved on to positions at the National Security Council and the Defense Department.

Both Robert Gates in his memoir and former National Security Adviser Zbigniew Brzezinski in interviews have acknowledged sending financial aid and non-weapon supplies through the CIA to the mujahideen six months prior to the formal Soviet invasion of Afghanistan. However both also state that there was already a covert Soviet presence in Afghanistan (special forces, intelligence). The CIA was not initially authorized to provide the mujahideen with weapons directly, but financial assistance was given so that they could secure weapons from other countries.

Once the Soviets formally invaded Afghanistan, the CIA was subsequently authorized by the Reagan administration to provide the Afghans with Stinger surface-to-air missiles. Most CIA aid was given through Pakistan's Inter-Services Intelligence agency, which was coordinating support not just from the U.S., but also from Britain, the PRC, Saudi Arabia, and Egypt. The CIA also gave money and weapons to the Pakistanis, with the unstated assumption that they would be distributed to the Afghans.

The total amount of money given to Pakistan or through Pakistan to the mujahideen was $20 billion or more.

from the book the looming tower it appears that while the CIA was involved we can overstate their importance given the large amount of Saudi funds which were funneled into the country