Apple: Hardware vulnerability in the T2 security chip for MacOS

The new generations of MacOS devices introduced from 2018 onwards possess the Apple T2 security chip, based on the A10 system on a chip of iPhones. Recently a group of hackers found a vulnerability that allows you to easily obtain root permissions, modify processes, access even encrypted data, insert malware.

The attack on MacOS devices is accessible by exploiting two vulnerabilities present in the A10 chips of iPhones: Checkm8 and Blackbird, two vulnerabilities already known to Apple for almost a year. Two questions arise: Why are MacOS vulnerabilities related to iPhone? Why hasn't Apple fixed the vulnerabilities? The T2 chip of the new MacOS is based on the A10 chip of the iPhones, which is why MacOS and iPhones have hardware and software in common, including vulnerabilities. Apple's research team has tried to fix these vulnerabilities but it seems that the only solution is to create a new security chip.

The checkm8

Checkm8 (read checkmate) is a vulnerability in some Apple devices that allows bootrom memory to be exploited. Bootrom memories are a type of ROM memory that intervenes at boot time and contains the code to start the device . The fact that this memory is vulnerable or contains bugs, implies that not only can it be read but also written, therefore changing the startup procedure of Apple devices.

According to some researchers, modifying the bootrom can create new boot processes, some dangerous and "personalize" your MacOS. Being a read-only memory error, there is no firmware update by definition. The only way to write to the bootrom is to exploit this vulnerability which would make it even more exposed to attacks by other people or malware. The only solution therefore remains a hardware update of the device.

The blackbird vulnerability

Blackbird is an exploit written for the SEPROM memory vulnerability of Apple devices. SEPROM memories are Apple proprietary used by A7 chips onwards to save biometric keys and important data, inaccessible to other proprietary and non-proprietary hardware . These memories are read-only, so it is not possible to perform a software update but a hardware update of the SEP chip is required.

By combining the bootrom vulnerability using the checkm8 exploit, the IO registry can bypass the hardware protection of the SEPROM and modify the data it contains. To do this, however, it is necessary to initially unlock the device by knowing the password or biometric data. By modifying the SEPROM data it is possible not to authorize access to the legitimate owner. Not all Apple devices with A7 + chip are vulnerable in the SEPROM, you can also attack only those vulnerable even at the bootrom.

T2 the (in) security chip

The T2 chip is designed directly by Apple with ARM Instruction Set Architecture for Mac devices to offer a new level of security to devices. A coprocessor secures Touch ID data, while also allowing for encrypted storage and secure boot. T2 also offers several tone mapping and face detection features.

You recently bought a MacOS, how to understand if your new MacOS has the T2 chip and therefore be vulnerable to cyber attacks? Look in your Mac's settings if you find “Apple chip T2” among the Controllers.

The T2 chip runs bridgeOS, a particular operating system developed by Apple for its hardware devices , used not only in the T-series of security chips but also in the AppleWatch to manage sensitive, encrypted data and access to cameras and microphones. Being a security chip, T2 handles important data such as biometric data or passwords for authentication in the device. For this reason T2 is equipped with a particular memory (SEPROM) in which to store the device authentication data.

The vulnerabilities of the T2 chip

After discovering the vulnerabilities used to attack the MacOS T2 chip, let's dive into some details about its vulnerability. According to some researchers, in Apple devices with T2 chips it is very easy to enter DFU mode without any authentication . Device Firmware Update (DFU) mode is indispensable when you want to reset your Apple device and it does not respond to commands, allowing you to restore the software to previous versions without errors, or to factory settings.

DFU mode is not just for this, it has many other features available if you have the Apple signature, which can be obtained by applying the checkm8 exploit. Exploiting T2 with checkm8 and blackbird we enter DFU mode where it is possible to enable the debug interface thus having full root access and kernel execution privileges . In this way it is possible to access any data and modify it, even the data encrypted with File Vault can be accessed by injecting a keylogger.

With full root access it is therefore possible to access even encrypted files, modify startup processes, inject malware. To do this, being a very long process, the attacker must physically have the Apple device. At the moment it has not been proven that this procedure can also be carried out with indirect attacks such as phishing, USB, trojan … The best defense technique seems to be not entrusting your MacOS to anyone . Currently, there seems to be a single solution available to restore the computer under attack, namely the restoration of the T2 chip (solution not yet verified).

At this point, many may think that Apple is not working on a solution for the vulnerabilities of its devices. A few months ago a program was launched to find all the bugs present in Apple devices . As for the T2 vulnerability of MacOS devices, as previously mentioned, the only solution is a hardware update with the possible development of a less vulnerable T3 chip.

The Apple article : Hardware Vulnerability in T2 Security Chip for MacOS comes from TechCuE .