"By definition, if can't fit into a single Sprint, then you cannot do it"
But it works both ways: if there are things that cannot be fitted into a sprint, your sprints are too short.
Nobody is telling that a sprint have to be two weeks long. Sprints should be as long or short as to be able to accomodate a significant result. Sometimes this means one week, sometimes three months, sometimes this needs to change from sprint to sprint or at least to product-livecycle phase to phase. The only requirement is for the sprint's duration to be fixed beforehand.
"The report is required to be done by Dec 1"
That's an OK bussiness need -at least, when it really is a bussiness need and not just a date to add pressure to your team, but one that some if not most of agile *methodologies* (no a problem with agilism by itself) can cope with.
This only means that most probably this single request needs to be handed in a custom way: if the feature set is clear and fixed (and it probably is) even the charicaturesque version of waterfall-as-an-antipattern can perfectly work: you get the requirements, design the solution, asign a team for the expected time, test and deliver. I don't see what the problem can be with that -except, maybe, that the team needs to come from somewhere, probably the same team doing everything else, which would mean, say, no sprints for the next month, or a negotiation to push forward stories that don't requiere to be delivered by the people now reassigned to the report and if that's really the problem you are again failing on agilism, since one of its tenets is "Customer collaboration over contract negotiation": obviously, putting people to do "this" makes it impossible for that people doing "that" at the same time, so the customer needs to make up his priorities, or the team to be expanded at the risk of falling in "the mithycal man-month" trap.
"Our board has directed that we are required to do Agile, and the certified scrum master they hired wouldn't let us start on the report."
You see, "scrum" is not "agile" but an "agile methodology". Your "scrum master" looks to me more of a "scumbag master" than anything else, since he failed twofold:
1) Within scrum, "The Scrum Master serves as a facilitator for both the Product Owner and the team", which he obviously failed to be.
2) In the overall context of agilism: being scrum an *agile* methodology is naturally driven by agilism first, and that means "Working software" as well as "Responding to change" and he failed in both fields.