How do i add default data in rails strong params?

Lets say if i want to generate and set default password for user while creating them in admin.

and i want to do something like this,

 def user_params
    params.require(:user).permit(:first_name, :last_name, :email, :password=> @default_generated_password, :password_confirmation => @default_generated_password)
end

I am using sorcery for User Authentication. I am having a feeling that this is completely wrong way, But how do i do it?

Merge them in after

params
 .require(:user)
 .permit(:first_name, :last_name)
 .merge(password: @default_generated_password, password_confirmation: @default_generated_password)

Or if you need it just in one action (create for example)

def create
  # password generation code...
  # ...

  @user = User.new(user_params.merge(password: @default_generated_password, password_confirmation: @default_generated_password))

  if @user.save
   redirect_to ...
  else
   flash[:error] = "Did not save"
   render :new
  end
end

private 

def user_params
  params.require(:user).permit(:first_name, :last_name)
end