Apple's T2 custom secure boot chip is not only insecure – it cannot be fixed without replacing the silicon
- Reference: 1602155049
- News link: https://www.theregister.co.uk/2020/10/08/apple_t2_security_chip/
- Source link:
Over the past three years, a handful of hackers have delved into the inner workings of the custom silicon, fitted inside recent Macs, and found that they can use an exploit developed for iPhone jailbreaking, [1]checkm8 , in conjunction with a memory controller vulnerability known as [2]blackbird , to compromise the T2 on macOS computers.
The primary researchers involved – @h0m3us3r, @mcmrarm, @aunali1 and Rick Mark (@su_rickmark) – expanded on the work @axi0mX did to create checkm8 and adapted it to target the T2, in conjunction with a group that built checkm8 into their [3]checkra1n jailbreaking software. Mark on Wednesday published a [4]timeline of relevant milestones.
The T2, which contains a so-called secure enclave processor (SEP) intended to safeguard Touch ID data, encrypted storage, and secure boot capabilities, was announced in 2017. Based on the Arm-compatible A10 processor used in the iPhone 7, the T2 first appeared in devices released in 2018, including MacBook Pro, MacBook Air, and Mac mini. It has also shown up in the iMac Pro and was added to the Mac Pro in 2019, and the iMac in 2020.
The [5]checkm8 exploit , which targets a use-after-free() vulnerability, allows an attacker to run unsigned code during recovery mode, or Device Firmware Update (DFU) mode. It has been modified to enable a tethered debug interface that can be used to subvert the T2 chip.
Turn on, tune in, drop out: Apple's whizz-bang T2 security chips hit a bum note for Mac audio [6]READ MORE
So with physical access to your T2-equipped macOS computer, and an appropriate USB-C cable and checkra1n 0.11, you – or a miscreant in your position – can obtain root access and kernel execution privileges on a T2-defended Mac. This allows you to alter macOS, loading arbitrary kernel extensions, and expose sensitive data.
According to Belgian security biz [7]ironPeak , it also means that firmware passwords and remote device locking capabilities, instituted via MDM or the FindMy app, can be undone.
Compromising the T2 doesn't dissolve macOS FileVault2 disk encryption but it would allow someone to install a keylogger to obtain the encryption key or to attempt to crack the key using a brute-force attack.
Currently, there's no known way to conduct this attack remotely, so the T2's fragility is mainly a matter of concern to those traveling with macOS laptops who want to protect their data at border crossing and in areas like hotel rooms that may be subject to "evil maid" attacks. The chip's weakness also gives law enforcement another forensic option for probing cyber-crime.
While such threats are quite uncommon, the T2's shortcomings represent a black eye for Apple, which developed the chip at no small cost specifically to enhance device security.
Unfortunately, it appears the T2 cannot be fixed. "Apple uses SecureROM in the early stages of boot," explained Rick Mark in a [8]blog post on Monday. "ROM cannot be altered after fabrication and is done so to prevent modifications. This usually prevents an attacker from placing malware at the beginning of the boot chain, but in this case also prevents Apple from fixing the SecureROM."
While Apple cannot fix the flaw in its T2, Mark says it should be possible to restore a compromised device that's still bootable into DFU by attaching it to a trustworthy second device.
Apple did not respond to a request for comment. ®
Get our [9]Tech Resources
[1] https://github.com/axi0mX/ipwndfu
[2] https://github.com/windknown/presentations/blob/master/Attack_Secure_Boot_of_SEP.pdf
[3] https://checkra.in/
[4] https://blog.t8012.dev/on-bridgeos-t2-research/
[5] https://twitter.com/axi0mX/status/1177544539046703104
[6] https://www.theregister.com/2019/02/19/apple_mac_audio/
[7] https://ironpeak.be/blog/crouching-t2-hidden-danger/
[8] https://blog.rickmark.me/checkra1n-and-the-t2/
[9] https://whitepapers.theregister.com/
Re: Physical access required, is T1 also compromised?
Is it really better than nothing, though? If you can drop the machine into DFU mode, you can install a basically undetectable keylogger that can completely compromise the machine.
I'm not aware of an exploit that allows you to do that on a Mac without one.
Surprised?
I'm certainly not. Given and local access to a machine that has a recovery mode, then exploits are inevitable and Apple must be aware of this.
But the main reason for them using such chips is not to prevent hackers from breaking in, but to prevent users from making changes such as installing other OSes or removing some of the many restrictions in IOS that we'll no doubt soon also see in MacOS.
Re: Surprised?
Interesting. Apple prevents users from installing other OSes, eh? Looks at iMac running Ubuntu. Looks at other iMac running Win 7, though admittedly putting Win 7 on it was a struggle, neither Apple nor Microsoft supports anything but Win 10. And admittedly Boot Camp is going to go away in ARM based Macs. It’s not gone yet.
And, of course, there are the various other Macs with Parallels VMs of older versions of macOS, various Windows installs, and various Linux installs, usually some variation on Ubuntu going back to 18.04.
Tell me more about the world you live in. What colour is the sky there?
I love my iMac...
...and now, thanks to Apple, everyone else can too!
Bigly win for the people!
While Apple cannot fix the flaw in its T2, Mark says it should be possible to restore a compromised device that's still bootable into DFU by attaching it to a trustworthy second device.
What if newer malware versions will be able to spread from compromised devices to uncompromised devices?
/inserts brrr.gif
I need your clothes, boots and your motorcycle
Listen, and understand. That T2 is out there. It can’t be bargained with. It can’t be reasoned with. It doesn’t feel pity, or remorse, or fear. And it absolutely will not be patched, ever, until your Macbook is dead.
Re: I need your clothes, boots and your motorcycle
What worries me is that the Cyberdyne Corporation actually exists.
You gat a beer for the excellent reference ———->
This could be good news!
Louis Rossmann has a video on youtube explaining the perils of having secure boot enabled on an apple PC with the T2 chip. Basically, if the T2 chip's firmware is corrupted, there is no way to update the firmware without deleting your data, and no access to your data without updating the firmware. You definitely want to be religious about backing up your PC. Maybe this security blunder will provide a work around!
https://www.youtube.com/watch?v=6dwqxsDHkKQ
Physical access required, is T1 also compromised?
So this exploit requires physical access to the device and could be used to install a key logger to decrypt the disk.
Definitely exploited but still better than with no T2.
Lastly is T1 exploited too?