Iterating through all members of a variable?

I'm looking for a way to run a white_list helper on all fields returned
from a form. I want to do it in the controller (and not in the view),
and do not want to specify the field names but to it dynamically.

Is there a way to achieve that?

params.each_pair do |k,v|
  ....
end

I would guess, but I haven't tried it.