This is the most common type of undercover police operation occurring at Burning Man, and fits the general understanding of entrapment.
Police officers in groups no fewer than two, costumed in a manner calculated to blend in, will attempt to gain your trust. They will likely spend many hours socializing with you, perhaps over more than one day, and when they think they’ve built enough confidence (or you are sufficiently inebriated), they will ask you for drugs. It can be direct or indirect, but it will be clear.
Single males particularly are targeted by provocatively dressed, flirtatious, young female confederates insinuating (or outright promising) sexual contact should mind altering substances be provided. Once the target produces a substance resembling illegal contraband, they will promptly be arrested by backup units positioned nearby.
If anyone you do not know asks you for drugs, they are a cop.
If you met them this year, you do not know them. They are cops.
In the likely event this happens to you, do not do anything to provoke them, or even let on that you know they are cops. Extricate yourself from the situation as inconspicuously as possible, remember their physical description, and tell your camp because they may try to leverage your name to gain trust.
It would be best not to consume or possess illegal drugs, but if choose to, be aware.