在 iOS 刪除 App 後不會刪除 keychain 內的資料

不過理論上 App 不能存取別其它 App 的 keychain 資料, 所以這勉強不算安全漏洞吧。若希望使用者重新安裝 App 時, 不會用到之前存在 keychain 的資料, 可在安裝後第一次啟動時先刪除 keychain 資料:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    //Clear keychain on first run in case of reinstallation
    if (![[NSUserDefaults standardUserDefaults] objectForKey:@"FirstRun"]) {
        // Delete values from keychain here
        NSArray *secItemClasses = @[(__bridge id)kSecClassGenericPassword,
                               (__bridge id)kSecClassInternetPassword,
                               (__bridge id)kSecClassCertificate,
                               (__bridge id)kSecClassKey,
                               (__bridge id)kSecClassIdentity];
        for (id secItemClass in secItemClasses) {
            NSDictionary *spec = @{(__bridge id)kSecClass: (__bridge id)secItemClass};
            SecItemDelete((__bridge CFDictionaryRef)spec);
        }
        [[NSUserDefaults standardUserDefaults] setValue:@"1strun" forKey:@"FirstRun"];
    }

    //...Other stuff that usually happens in didFinishLaunching
}

參考資料:

• http://stackoverflow.com/questions/4747404/delete-iphone-keychain-items-when-application-uninstall
• http://stackoverflow.com/questions/14086085/how-to-delete-all-keychain-items-accessible-to-an-app