Security implications of storing a password in Settings.bundle and getting with CFPreferencesCopyAppValue

Question

Hello,

Apologies for the seeming obviousness of this question, but for whatever reason I haven't been able to find a definitive answer in the Apple documentation about where and how Settings.bundle password info is stored. My question: if I need to store some credentials for an app, and I use a Settings.bundle so that the password is entered into a PSTextFieldSpecifier textfield in Apple's Settings area with IsSecure = YES, and then I access the value from my app using CFPreferencesCopyAppValue, never writing it out to NSUserDefaults and only sending it over the network securely, how secure is that storage and retrieval method when compared to storing and retrieving the password using the keychain in my own app settings? Thanks for your input.

Answer 1

CFPreferencesCopyAppValue is just the Core Foundation way of accessing the same information you get when using NSUserDefaults. In terms of security, the features are exactly the same. That is, it's not encrypted. It's secure only in the sense that it's obscured. The "correct" answer is to use the keychain.

The counter to that is that many applications use NSUserDefaults to store passwords. You could argue that unless the password controls access to information of any value then it's not worth the effort in trying to use the keychain. Which brings me to the second argument in favour of using a secure field in the Settings application: the keychain API is hideous and, in my experience at least, writing error-free code is tricky.

Answer 2

Keychain on the iPhone is going to be the most secure, unless you're using custom encryption, which is very difficult to do (and export). NSUserDefaults isn't considered secure.