Lockbox is an Objective-C utility class for storing data securely in the keychain. Use it to store small, sensitive bits of data securely.
There are some bits of data that an app sometimes needs to store that are sensitive:
- In-App Purchase unlocked feature bits
- and anything else that, if in the wrong hands, would be B-A-D.
The thing to realize is that data stored in
NSUserDefaults is stored in the clear! For that matter, most everything stored in your app's sandbox is also there in the clear.
Surprisingly, new and experienced app developers alike often do not realize this, until it's too late.
The Lockbox class methods make it easy to store and retrieve
NSDates into and from the key chain. You are spared having to deal with the keychain APIs directly!
For greater security, and to avoid possible collisions between data stored by your app with data stored by other apps (yours or other developers), the keys you provide in the class methods for storing and retrieving data are prefixed with your app's bundle id. The class methods provide some convenience by simplifying the use of Lockbox. But if you need to be able to access a comment set of keys between your app, and say, an iOS8 extension, you may need to override the key prefix. For that, you can instantiate your own instance of Lockbox, providing your custom key prefix, and call the same methods (as instance methods) as you would call on the class. (The signatures are the same between class and instance methods. In fact, the class methods operation on a class static Lockbox instance.)
The one caveat to keep in mind is that the keychain is really not meant to store large chunks of data, so don't try and store a huge array of data with these APIs simply because you want it secure. In this case, consider alternative encryption techniques.
As of v2.0, Lockbox is ARC-only. For non-ARC support, use v1.4.9.
Lockbox includes the following methods, shown here as class methods. The same methods (as instance methods) may be called on your own Lockbox instances.
setXxx methods return
BOOL, indicating if the keychain operation succeeded or failed. The
xxxForKey methods return a non-
nil value on success, or
nil on failure.
setXxx methods will overwrite values for keys that already exist in the keychain, or simply add a keychain entry for the key/value pair if it's not already there.
In all the methods you can use a simple key name, like "MyKey", but know that under the hood Lockbox is prefixing that key with your app's bundle id (if you are using the Class methods, your own key if you are using a Lockbox instance). So the actual key used to store and retrieve the data looks more like "com.mycompany.myapp.MyKey" or "my.custom.key.MyKey". This ensures that your app, and only your app, has access to your data.
The methods with an
accessibility argument take a Keychain Item
can use this to control when your keychain item should be readable. For
kSecAttrAccessibleWhenUnlockedThisDeviceOnly will make
it accessible only while the device is unlocked, and will not migrate this
item to a new device or installation. The methods without a specific
accessibility argument will use
kSecAttrAccessibleWhenUnlocked, the default in recent iOS versions.
Requirements & Limitations
To use this class you will need to add the
Security framework to your project.
This class was written for use under Cocoa Touch and iOS. The code and tests run fine in the iOS simulator under Mac OS. But there are some issues using this class under Cocoa and Mac OS. There are some keychain API differences between the 2 platforms, as it happens. Feel free to fork this repo to make it work for both Cocoa and Cocoa Touch and I'll be happy to consider your pull request!
Note on running unittests on device
If you experience SecItemCopyMatching errors with code 34018 on Lockbox methods while running your app unit tests target on device, your can avoid these by code signing your unit tests .xcttest folder.
Add Run Script phase to your unit tests target Build Phases with:
codesign --verify --force --sign "$CODE_SIGN_IDENTITY" "$CODESIGNING_FOLDER_PATH"
Link to latest CocoaDocs: cocoadocs.org/docsets/Lockbox/
See the LICENSE file for details.