no_permission when creating user through mobile API

[elieseif]

I tried logging in as Administrator after api.init and before api.save, and got both session and cpsession hashes so login was successful, but api.save still gives no_permission.
I also tried calling api.init again after user.login2, no change.

That said, whenever I include api_c in login2 or save method calls, I get "invalid_api_signature". If I remove api_c and keep api_s, api_sig and api_v, I am able to login, but user.save gives the no_permission error.

At this point, I'm out of ideas.