CODEWITHSUNDEEP
iosobjective-ciphonefingerprinttouch-id
Max
Max

Reputation: 2299

how to check No Fingerprints added for Touch ID in iOS

I am integrating Touch ID access in one of my app. I have successfully integrated it. Here is that code:

    dispatch_queue_t highPriorityQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 0.75 * NSEC_PER_SEC), highPriorityQueue, ^{

        dispatch_async(dispatch_get_main_queue(), ^{

            LAContext *context = [[LAContext alloc] init];
            isTouchExists = [context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:nil];
            if (isTouchExists) {
                NSString * keychainItemIdentifier;

                NSString * keychainItemServiceName;
                keychainItemIdentifier = @"fingerprintKeychainEntry";
                keychainItemServiceName = [[NSBundle mainBundle] bundleIdentifier];
                NSData * pwData = [@"the password itself does not matter" dataUsingEncoding:NSUTF8StringEncoding];
                NSMutableDictionary * attributes = [[NSMutableDictionary alloc] initWithObjectsAndKeys:
                                                    (__bridge id)(kSecClassGenericPassword), kSecClass,
                                                    keychainItemIdentifier, kSecAttrAccount,
                                                    keychainItemServiceName, kSecAttrService, nil];
                CFErrorRef accessControlError = NULL;
                SecAccessControlRef accessControlRef = SecAccessControlCreateWithFlags(
                                                                                       kCFAllocatorDefault,
                                                                                       kSecAttrAccessibleWhenUnlockedThisDeviceOnly,
                                                                                       kSecAccessControlUserPresence,
                                                                                       &accessControlError);
                if (accessControlRef == NULL || accessControlError != NULL)
                {
                    NSLog(@"Cannot create SecAccessControlRef to store a password with identifier “%@” in the key chain: %@.", keychainItemIdentifier, accessControlError);
                }

                attributes[(__bridge id)kSecAttrAccessControl] = (__bridge id)accessControlRef;
                attributes[(__bridge id)kSecUseNoAuthenticationUI] = @YES;
                attributes[(__bridge id)kSecValueData] = pwData;

                CFTypeRef result;
                OSStatus osStatus = SecItemAdd((__bridge CFDictionaryRef)attributes, &result);

                if (osStatus != noErr)
                {
                    NSError * error = [[NSError alloc] initWithDomain:NSOSStatusErrorDomain code:osStatus userInfo:nil];
                    NSLog(@"Adding generic password with identifier “%@” to keychain failed with OSError %d: %@.", keychainItemIdentifier, (int)osStatus, error);
                }
                //other my code for success
           }
        });
    });

Now, If I remove all the fingerprints from settings in iPhone, This code will work and ask for passcode. So My question is:

how can I come to know that there is no any fingerprints added for Touch ID?

I don't want to show iOS device passcode screen as I have already built passcode screen for my app security. So is there any option to check device have atleast one fingerprint available for Touch ID access?

Thanks in advance.

======== EDIT 1 ===========

It is working on my side also. The issue is I need to check it each time when I am asking for Touch ID. I need to fetch status in viewWillAppear or in applicationDidBecomeActive each time whenever I want to use Touch ID access in app, as I am removing fingers run time, it may not reflecting in my code so I need to fetch each time.

Upvotes: 3

Views: 3123

Answers (2)

Lal Krishna
Lal Krishna

Reputation: 16160

canEvaluatePolicy:error: will be Error : LAErrorTouchIDNotEnrolled

Authentication could not start because Touch ID has no enrolled fingers.

APPLE DOC Ref.

Try:

LAContext *context = [[LAContext alloc] init];
    NSError *error;
    if ([context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error]) {
        [context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:@"My Reason" reply:^(BOOL success, NSError * _Nullable error) {

        }];
    }else{
        if (error.code == LAErrorTouchIDNotEnrolled) {
            NSLog(@"Error: %@", error.localizedDescription);
        }
    }

Upvotes: 5

Horia
Horia

Reputation: 26

If there are no fingerprints registered, canEvaluatePolicy should return false.

Source : https://developer.apple.com/documentation/localauthentication/lacontext/1514149-canevaluatepolicy?language=objc

Upvotes: 1

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