This is my first question here in Information Security SE. Is there a recommendation to help telling the scenarios where authentication should precede authorization from the ones where authorization comes first?
I experienced both situations at different workplaces (the situation was very similar, switching to a system user with a certain set of privileges in Unix command line). When does authorization need to come first to spare the authentication? When should it authenticate first so as to not to tell a potential intruder that the user impersonated would not be entitled for the current operation?
Are there situation specific generic guidelines or rules for this?
OK, let me come up with a specific situation. Logged in with own employee user ID, SUing to another user. I mistyped the system user I was about to switch to, but the other is also an existing user in our environment. Before asking for password, I got rejected saying I wasn't authorized to perform this operation.
Given that I just finished an anti-social engineering course today, I wondered whether it was a good idea to tell me I wasn't authorized (even this may be a useful piece of information for someone trying to impersonate me in the corporate network).