My understanding is the ball is in play until it comes to a natural stop or goes out of play. The striker can only touch the ball once but there isn't a rule on the keeper - for example the keeper could tip it on on to the post but it rebounds back towards the keeper who can palm it away from the goal line
That would certainly make sense given it counts if it rebounds off the post, hits the keeper and goes in, that counts as a goal in a shootout.