How to preserve identifierForVendor in ios after uninstalling ios app on device?

Question

I am developing an iOS app which calls web-service for login and at that time i send login credentials to web server along with vendor identifier (identifierForVendor),to identify device uniquely for those credentials.So user can have only one device and one credential.

I got identifierForVendor with

NSString *uuid = [[UIDevice currentDevice] identifierForVendor].UUIDString

This identifier will then store in database of web server and also in device database.Next time when user opens application and will try to download data from web server firstly local identifierForVendor on users device will compare with identifier stored on web server.

Problem occurs when user uninstall app and reinstall it, I found that identifierForVendor is changed. So user cannot proceed further.

I read apple documentation UIDevice Documentation

As mention there, if all app from same vendor uninstalls from device then at time of new installation of any app from that vendor will take new identifierForVendor.

So how to deal with this in my case ?

Answer 1

You may keep it in KeyChain

-(NSString *)getUniqueDeviceIdentifierAsString
{

 NSString *appName=[[[NSBundle mainBundle] infoDictionary] objectForKey:(NSString*)kCFBundleNameKey];

 NSString *strApplicationUUID = [SSKeychain passwordForService:appName account:@"incoding"];
 if (strApplicationUUID == nil)
 {
    strApplicationUUID  = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
    [SSKeychain setPassword:strApplicationUUID forService:appName account:@"incoding"];
 }

 return strApplicationUUID;
}

Answer 2

Generally, don't use identifierForVendor. Instead, use NSUUID to generate a custom UUID and store that in the keychain (because the keychain isn't deleted if the app is deleted and reinstalled).

Answer 3

Addition to @nerowolfe's answer.

SSKeychain uses kSecAttrSynchronizableAny as a default synchronization mode. You probably don't want identifierForVendor to be synced across multiple devices so here is a code:

// save identifierForVendor in keychain without sync
NSError *error = nil;
SSKeychainQuery *query = [[SSKeychainQuery alloc] init];
query.service = @"your_service";
query.account = @"your_account";
query.password = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
query.synchronizationMode = SSKeychainQuerySynchronizationModeNo;
[query save:&error];

Answer 4

You can try use KeyChain to save your VendorIdentifier, that will exist till your device is reset, even if you uninstall your app.

Answer 5

Ok. I didn't want to use a third party - namely SSKeychain. So this is the code I tried, fairly simple and works well:

    NSString *bundleId = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleIdentifier"];

KeychainItemWrapper *keychainItem = [[KeychainItemWrapper alloc] initWithIdentifier:bundleId accessGroup:nil];
if(![keychainItem objectForKey:(__bridge id)(kSecValueData)]){
    NSString *idfa = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
    [keychainItem setObject:idfa forKey:(__bridge id)(kSecValueData)];
    NSLog(@"saving item %@", [keychainItem objectForKey:(__bridge id)(kSecValueData)]);
}else{
    NSLog(@"saved item is %@", [keychainItem objectForKey:(__bridge id)(kSecValueData)]);
}

Answer 6

Swift version

func UUID() -> String {

    let bundleName = NSBundle.mainBundle().infoDictionary!["CFBundleName"] as! String
    let accountName = "incoding"

    var applicationUUID = SAMKeychain.passwordForService(bundleName, account: accountName)

    if applicationUUID == nil {

        applicationUUID = UIDevice.currentDevice().identifierForVendor!.UUIDString

        // Save applicationUUID in keychain without synchronization
        let query = SAMKeychainQuery()
        query.service = bundleName
        query.account = accountName
        query.password = applicationUUID
        query.synchronizationMode = SAMKeychainQuerySynchronizationMode.No

        do {
            try query.save()
        } catch let error as NSError {
            print("SAMKeychainQuery Exception: \(error)")
        }
    }

    return applicationUUID
}

Answer 7

There is no definite way to link a unique number to a device any more, this is not allowed with the Apple privacy guidelines.

You can try to save your own Unique ID in the keychain, but if the user clear his device this ID is also gone.

Generally is it just wrong to link a device to a user, since you are not longer identifying users but devices. So you should just change your API so that the user can re-login and that the vendor ID is bound to the users account.

Also what happens when the user has more then one device, like an iPhone and iPad, and uses you app on both? Since you authentication is based an unique ID this can not be done.

Answer 8

I had used KeychainAccess pod for this problem.

In your pod file :

pod 'KeychainAccess', '~> 2.4' //If you are using Swift 2.3 
pod 'KeychainAccess' //Defaults to 3.0.1 which is in Swift 3

Import KeychainAccess module in file where you want to set UUID in keychain

import KeychainAccess

Use below code to set and get UUID from keychain :

Note : BundleId is key and UUID is value

var bundleID = NSBundle.mainBundle().bundleIdentifier
    var uuidValue = UIDevice.currentDevice().identifierForVendor!.UUIDString

 //MARK: - setVenderId and getVenderId
    func setVenderId() {

        let keychain = Keychain(service: bundleID!)

        do {
            try keychain.set(venderId as String, key: bundleID!)
            print("venderId set : key \(bundleID) and value: \(venderId)")
        }
        catch let error {
            print("Could not save data in Keychain : \(error)")
        }
    }

    func getVenderId() -> String {
        let keychain = Keychain(service: bundleID!)
        let token : String = try! keychain.get(bundleID!)!
        return token
    }