A company selling password-cracking tools says that a newly-discovered T2 Mac security vulnerability allows it to crack passwords on these machines, bypassing the lockouts.
The method used is far slower than conventional password-cracking tools, but although the total time needed could run into thousands of years, that could fall to as little as 10 hours when the Mac owner has used a more typical password…
Background: The T2 chip
Apple introduced the T2 security chip in 2018, and it was used to provide a secure boot-up feature to Intel Macs from that year on.
The key to T2 security is that the chip contains both an SSD controller and a crypto engine, allowing it to instantly decrypt and encrypt data on the fly. This is similar to FileVault, but even more secure as only the T2 chip can do the decryption – and security features on the chip prevent an attacker from modifying macOS to gain access. Here’s how Apple describes the protection:
At the time that software is downloaded and prepared to install, it is personalised with a signature that includes the Exclusive Chip Identification (ECID) — a unique ID specific to the T2 chip in this case — as part of the signing request. The signature given back by the signing server is then unique and usable only by that particular T2 chip. The UEFI firmware is designed to ensure that when the Full Security policy is in effect, a given signature isn’t just signed by Apple but is signed for this specific Mac, essentially tying that version of macOS to that Mac. This helps prevent rollback attacks.
T2 Mac security vulnerability
Passware was already able to crack passwords and decrypt FileVault-protected drives on older Macs without the T2 chip. This uses GPU acceleration to achieve brute-force attacks of literally tens of thousands of passwords per second, making it a trivial task to break into these Macs.
Until recently, however, it wasn’t practical to mount brute-force attacks on Macs with a T2 chip. This is because the Mac password is not stored on the SSD, and the chip limits the number of password attempts that can be made, so you’d instead have to brute-force the decryption key, and that is so long it would take millions of years.
