Apple to fix backup security vulnerability in iOS 10

Apple plans to fix a vunerability in iOS 10 discovered by controversial Russian forensics company Elcomsoft that puts iPhones’ security at risk.

Apple added an alternative password verification mechanism to iOS 10, inadvertently weakening the security of local backups, the company said.

Elcomsoft, which produces iPhone probing tools that are available to any buyer, claims to have discovered a “major security flaw” in the iOS 10 backup protection mechanism.

According to security researcher Per Thorsheim , the mechanism uses a simpler algorithm than the previous password-based key derivation function 2 (PBKDF2) with SHA1 (secure hash algorithm), which uses 10,000 iterations to obfuscate credentials.

The new password verification method in iOS 10 uses a single-iteration password protection function with 256-bit SHA2 , which has made brute-force credentials cracking significantly easier, he said.

Elcomsoft claims to have exploited the weakness to develop an attack that is able to bypass certain security checks when enumerating passwords protecting local iTunes backups made by iOS 10 devices.

“The impact of this security weakness is severe. An early CPU-only implementation of this attack gives a 40-times performance boost compared with a fully optimised GPU-assisted attack on iOS 9 backups,” Elcomsoft’s Oleg Afonin wrote in a blog post .

The brute force attack enabled the Elcomsoft’s developers to try passwords around 2,500 times faster than iOS 9 if a CPU-only version of the attack is used in both cases.

Afonin said the “new” password verification method exists in parallel with the “old” method, which continues to work with the same slow speeds as before.

According to Afonin, this approach is the most logical for hackers because iPhones and iOS are secure and are becoming increasingly more difficult to hack.

“With no jailbreak available for iOS 10, physical acquisition is out of the question even on older devices and even if you know the passcode,” he wrote.

“Cloud acquisition is only possible if you know the user’s Apple ID and password or have access to the user’s computer with iCloud Control Panel (to extract an authentication token), but even then you won’t be able to decrypt the keychain.”

Forcing an iPhone or iPad to produce an offline backup and analysing resulting data is one of the very few acquisition options available for devices running iOS 10, he said.

According to Afonin, local backups are easy to produce if the iPhone is unlocked, buthackers may be able to produce a local backup even if the phone is locked by using a pairing record extracted from a trusted computer.

“If you are able to break the password, you’ll be able to decrypt the entire content of the backup, including the keychain. At this time, logical acquisition remains the only acquisition option available for iPhone 5s, 6/6Plus, 6s/6sPlus and 7/7Plus running iOS 10 that offers access to device keychain,” he wrote.

The keychain is Apple’s protected storage that is additionally encrypted on a file level on top of the already active full-disk encryption that works on a block level. While stored on the device, the keychain is encrypted with a key that is buried deep in Secure Enclave.

According to Afonin, logical acquisition through password-protected iTunes backups is currently the only way to extract and decrypt keychain data out of an iOS 10 device.

A hacker who succeeds in doing so, added Afonin, gains access to saved passwords or authentication tokens to applications requesting secure storage for authentication credentials, Safari logins and passwords, credit card information, Wi-Fi network information, and any data that third-party app developers consider worthy of extra protection.

Apple said in a statement that company is aware of the issue that affects the encryption strength for back ups of devices on iOS 10 when backing up to iTunes on the Mac or PC and will address it in a security update.