'Secure Boot'-Enabled Windows Devices May Be Permanently Vulnerable Due To 'Golden Key' Backdoor, Say Researchers (Updated)

Updated, 9/11/2016, 11:20am PT: Microsoft sent us a statement shortly after we published this article. The statement is below, and we've adjusted the article copy to reflect the new information.

“The jailbreak technique described in the researchers’ report on August 10 does not apply to desktop or enterprise PC systems. It requires physical access and administrator rights to ARM and RT devices and does not compromise encryption protections," said a Microsoft spokesperson.

Two security researchers, MY123 and Slipstream, uncovered multiple security vulnerabilities in Microsoft’s Secure Boot policies on Windows 8, Windows 8.1, and Windows 10 devices. The flaws can now allow anyone to unlock devices that were supposed to load only the signed Windows operating system. Because Secure Boot can now be bypassed, it also means the devices are vulnerable to bootkit and rootkit types of malware, much like PCs were in the pre-Secure Boot era.

Windows’ “Golden Key" Backdoor

The researchers described the vulnerabilities as a “golden key” backdoor that Microsoft created, supposedly to allow developers to debug the devices. However, as expected with any type of backdoor, once it’s created, anyone that discovers it gets access whether they're supposed to or not.

This seems to be the point the researchers were also trying to make:

“A backdoor, which MS put in to Secure Boot because they decided to not let the user turn it off in certain devices, allows for Secure Boot to be disabled everywhere! You can see the irony. Also the irony in that MS themselves provided us several nice 'golden keys' (as the FBI would say) for us to use for that purpose,” wrote the security researchers on their website.“About the FBI: are you reading this? If you are, then this is a perfect real world example about why your idea of backdooring cryptosystems with a 'secure golden key' is very bad! Smarter people than me have been telling this to you for so long, it seems you have your fingers in your ears.You seriously don't understand still? Microsoft implemented a 'secure golden key' system. And the golden keys got released from MS['s] own stupidity. Now, what happens if you tell everyone to make a 'secure golden key' system? Hopefully you can add 2+2....,” they added.

A Backdoor That Can’t Be Closed

To make matters worse, according to the researchers, this isn’t even a backdoor that can be closed. That means Windows devices that have a locked Secure Boot, such as smartphones and tablets, may have become permanently vulnerable to physical unlocking or to bootkits and rootkits.

The security researchers said that it would be "impossible in practise [sp] for MS to revoke every bootmgr earlier than a certain point, as they'd break install media, recovery partitions, backups, etc."

Microsoft Hasn’t Tackled The Issue Head-On

The two researchers discovered the vulnerabilities in March of this year and alerted Microsoft about them soon after. However, according to the researchers, Microsoft didn’t seem too responsive to these bug reports, but it eventually awarded them the bug bounties in June. Microsoft then followed up with a few patches in July and August, in the latest "Patch Tuesday" update.

The security researchers noted that these patches don’t do much at all to resolve the issue. According to them, Microsoft blacklisted most of the Secure Boot policies that made the boot process vulnerable in the first place, but not all of them. Also, before the blacklist file is loaded, the boot process loads up a vulnerable Secure Boot policy, so the fix isn’t much of a fix right now.

On the latest Windows 10 build 1607 (Anniversary Update), an attacker would have to replace the existing boot manager with an older boot manager for the attack to work. That should be relatively easy, though, if the attacker has physical access to the device.

Lucian Armasu
Lucian Armasu is a Contributing Writer for Tom's Hardware US. He covers software news and the issues surrounding privacy and security.
  • Jeff Fx
    So we're back to where we were with totally open PCs. Is this supposed to be bad?
  • captaincharisma
    still better than a mac
  • JakeWearingKhakis
    Umm the update is from the future!!!!!!

    "Updated 9/11/2016
  • Rhinofart
    Just wondering, how is that better than a Mac? They are all about the same these days. Mac, Win, *nix same as Ford, Dodge, Chevy.
  • abbadon_34
    ""A backdoor, which MS put in to Secure Boot because they decided to not let the user turn it off in certain devices, allows for Secure Boot to be disabled everywhere!""

    So does mean we can truely disable all the datamining and spyware in Win 10 ? Maybe it is finally safe to upgrade. Just waiting on a nice open source utility.
  • Darkk
    JAKEWEARINGKHAKIS Aug 11, 2016, 3:34 PM
    Umm the update is from the future!!!!!!

    "Updated 9/11/2016"

    TIME WARP!!!
  • memadmax
    Friends don't let friends run Win8/10...

    No, I don't care that MS came out and said it doesn't apply to desktop machines...

    My trust meter with MS is at: -3
  • virtualban
    one key feature (not bug) shown, 99 still remaining
    (and, why am I having trouble posting here? had to logout relogin and still brings me to the next article, witcher3 when clicking comments on the same tab)
  • kungpaoshizi
    Are you using Chrome Virtualban? I'm using IE (because my work is stupid and won't use Edge) and I have no issues.
    Otherwise this really isn't news. They would say the same thing about a POS system that has no ports and it would qualify because you could break it open and connect to jumpers inside.. There's not a single machine that has un-exploitable setup, in existence, when it comes to physical access.
  • godmodder
    If the attacker has physical access, then all bets are off anyway.