Do you want the user's Apple ID password, to get access to their Apple account, or to try the same email/password combination on different web services? Just ask your users politely, they'll probably just hand over their credentials, as they're trained to do so 👌
iOS asks the user for their iTunes password for many reasons, the most common ones are recently installed iOS operating system updates, or iOS apps that are stuck during installation.
As a result, users are trained to just enter their Apple ID password whenever iOS prompts you to do so. However, those popups are not only shown on the lock screen, and the home screen, but also inside random apps, e.g. when they want to access iCloud, GameCenter or In-App-Purchases.
This could easily be abused by any app, just by showing an UIAlertController, that looks exactly like the system dialog.
Even users who know a lot about technology have a hard time detecting that those alerts are phishing attacks.
This is just a proof of concept, phishing attacks are illegal! Don't use this in any of your apps. The goal of this blog post is to close the loophole that has been there for many years, and hasn't been addressed yet. For moral reasons, I decided not to include the actual source code of the popup, however it was shockingly easy to replicate the system dialog.