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Keychain Item Invalidation After Interrupted Face ID Reset on iOS 18.3.1
I am working on improving Keychain item storage secured with Face ID using SecAccessControlCreateWithFlags. The implementation uses the .biometryAny flag as shown below: SecAccessControlCreateWithFlags( kCFAllocatorDefault, kSecAttrAccessibleWhenUnlockedThisDeviceOnly, .biometryAny, &error ) While this approach generally works as expected, I encountered a specific edge case during testing. On iOS 18.3.1 with Xcode 15.4, the following sequence causes the Keychain item to become inaccessible: Navigate to Settings > Face ID & Passcode and select Reset Face ID. Before setting up a new Face ID, tap the Back button to exit the setup process. Reopen the Face ID setup and complete the enrollment. Return to the app—previously stored Keychain items protected by .biometryAny are no longer available. This behavior appears to be a change introduced in recent iOS versions. In versions prior to iOS 15, resetting or deleting Face ID entries did not invalidate existing Keychain items protected by .biometryAny. This difference in behavior between iOS versions raises questions about the changes to biometric protection handling. Any suggestions are welcomed that might shine a light on what the best practice to use keychain access control and prevent the data to become unavailable.
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