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iosswiftsecuritykeychain

IOS not able to create privatekey if only devicecode is set on device?

Im trying to generate a privatekey that only is accessible when either devicecode or current set of biometrics( that is already registered on device) is used.

It works when i have a finger registered on device, then its all good. But if i delete my registered "touchid-finger", and try to generate a new key, then it returns nil

Errorcode is -25293

Code example:

func generateKey() -> SecKey?{
    var error: Unmanaged<CFError>?
    let accessControl = SecAccessControlCreateWithFlags(
            kCFAllocatorDefault,
            kSecAttrAccessibleWhenUnlockedThisDeviceOnly,
            [.devicePasscode,.or,.biometryCurrentSet],
            nil)

    let attributes:[String : Any] = [kSecAttrType as String: kSecAttrKeyTypeRSA,
    kSecAttrKeySizeInBits as String:4096,
    kSecPrivateKeyAttrs as String: [
      kSecAttrIsPermanent:true,
      kSecAttrCanSign: true,
      kSecAttrApplicationTag: "yes.its.my.tag",
      kSecAttrAccessControl:accessControl!]]
      let privateKey = SecKeyCreateRandomKey(attributes as CFDictionary, &error)
     if(error != nil || privateKey == nil) {
      fatalError("explode Kittens")
     }
     return privateKey
}

fyi.Its actually works on simulators but not on real devices.

Am i doing something wrong? Is this working as intended? is it a bug? (sooo many questions :D )

Solution

  • "The problem relates to how the item is /created/, and that’s not what these flags control.

    Indeed, for .biometryCurrentSet to have any meaning at the time of use, there must actually be a current set of biometrics at the time of creation, and I think that’s the source of the errSecAuthFailed.

    My recommendation is manually fall back to using just .devicePasscode if there’s no biometrics available. Two ways: A. Catch the error and retry B. Preflight the request using the LocalAuthentication framework."

    Apple says no can do :D