Apple's two-factor authentication system does not protect users' private files backed up to the iCloud, it is claimed.
Fanbois have been able to secure their Apple accounts with a two-step login process since March: these accounts are important because they are used to bung or retrieve backups into and out of Cupertino's iCloud storage system, download software from the app store, and buy songs, movies, and TV shows for iTunes, among other things. Enabling the technology - which is available in the US, UK, Australia, Ireland, Germany and Italy - links an Apple ID username to a registered iPhone or iPad.
When a user wants to log into their account, a passcode is sent to this named device, and the user must submit this code in addition to their regular password to gain access. Of course, this should make life harder for account hijackers, because they must somehow steal the iPhone or iPad as well as obtaining a victim's password in order to compromise an account.
But according to research from security biz Elcomsoft, Apple did a "half-hearted job" of implementing its verification system, "leaving ways for the intruder to access users’ personal information, bypassing the (optionally enabled) two-factor authentication".
Specifically iOS Backups and iCloud data is not protected by two-factor authentication.
"In its current implementation, Apple’s two-factor authentication does not prevent anyone from restoring an iOS backup onto a new (not trusted) device," explained Vladimir Katalov, chief exec of ElcomSoft in a blog post. "In addition, and this is much more of an issue, Apple’s implementation does not apply to iCloud backups, allowing anyone and everyone knowing the user’s Apple ID and password to download and access information stored in the iCloud."
iPush less secure than SMS for 2FA
iCloud has been exploited in the past and nothing Apple has done in introducing two-factor authentication will stop it being exploited in the future, according to Elcomsoft. This is because Apple made a string of mistakes in rolling-out the technology.
For one thing the verification code appears on the lock screen if sent to an iPhone, so it can be accessed without entering the correct passcode. This is not a text message, but rather a push notification delivered via the Find My Phone protocol service. The approach means that Wi-Fi only iPads and iPods can be used as a registered device even though they don't support SMS.
Only if the Find My Phone service is disabled would a verification code be sent as a text message to a registered iPhone.
Worse still, providing an attacker has a valid Apple ID and password combination - something that might be obtained through a phishing attack or similar - they do not need this authentication code to get at backups, according to ElcomSoft.
Regardless of two-step authentication settings, backups and documents are still accessible from anywhere.
"We can restore an offline or iCloud backup onto a new Apple device (or use Elcomsoft Phone Password Breaker to download and access on the computer) without being requested or entering the second passcode," Katalov explained.
"All you need is some software that can browse and analyze offline iTunes backups, such as iBackupBot or more advanced Oxygen Forensic Suite," he added.
If an attacker just wanted to restore everything from the iCloud onto a new device then all they need is a user's loginID and password.
"No two-factor authentication kicks in during the process," according to Katalov.
ElcomSoft's blog post features screen shots illustrating this security shortcoming.
Independent security advisor Per Thorsheim, founder and organizer of the annual Passwords conference, who alerted us to Elcomsoft's research, confirmed the Russian security firm's findings. He said that though Apple's two factor-authentication would block unauthorised purchases it doesn't protect data.
"People expect a 2FA solution to add additional security in order to protect their data, but in contrast to Dropbox & Google, Apple doesn't really do that," Thorsheim explains. "It's the 'weakest' 2FA solution launched so far by the big & well-known services, it will only add an additional layer of false security to people's minds - which may have dangerous results.
"As it's done now, their 2FA doesn't protect my data at all, they only protect my account with Apple from being exploited in terms of direct financial loss (unauthorised purchases, password change etc). In my opinion that is not enough," he added.
Elcomsoft's Katalov concludes that Apple’s approach in implementing two-factor authorisation "does not look like a finished product".
"It’s not flawed or anything," Katalov writes. "It does everything that it claims to be doing. What it doesn’t do, however, is protect users’ personal information stored in the iCloud from unauthorized access. It’s not on the spec list, either.
"In addition, the choice of the Find My iPhone service, while understandable, is clearly an afterthought, as supposedly secure verification codes are displayed in plain view on the lock screen," he adds.
Despite his reservation about Apple's implementation, Katalov recommends applying two-factor authentication on Apple accounts nonetheless.
Sean Sullivan, a security adviser at F-Secure, agreed with Katalov's assessment of Apple's two-factor implementation while taking issue with the idea that users ought always to enable it anyway.
"I would disagree with the idea that 'it is a good idea to enable 2FA on all your accounts'. I think it depends on the type and purpose of the account," Sullivan told El Reg.
Last week Sullivan criticised Twitter's newly introduced, much anticipated two-factor authentication, because it was possible to add a phone number without said number being verified. All the web giants are rolling out two-factor authentication thanks to the growing realisation that passwords alone are fundamentally weak. Social engineering, keyloggers, Trojans, password re-use, rainbow tables and other factors contribute to the growing number of accounts compromised every month, resulting in Twitter hijacks of high-profile media accounts and other more serious (if less visible) problems.
Sullivan is more positive about the Google and Microsoft approach to introducing this technology.
"I think the Google and Microsoft Authenticator apps offer a nice approach," he told El Reg. ®