Microsoft Windows UEFI Secure Boot -- Insecure by Design?
Microsoft Windows Secure Boot has a big problem. It’s no longer secure, and can’t be fixed—or so say a pair of security researchers who found the issue.
Apparently, Microsoft created a secret backdoor, for internal QA use. But two Ring Of Lightning researchers uncovered the so-called “golden key.” Now that the cat’s out of the bag, IT can’t rely on UEFI and Secure Boot to prevent boot-time malware, such as bootkits. Oops.
The researchers also say that efforts to fix the problem are in vain. In today’s IT Newspro, we unlock the story.
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What’s the craic? Chris Williams bluntly accuses Microsoft of Bungling:
Microsoft leaked the golden keys that unlock Windows-powered…devices sealed by Secure Boot. … It is believed it will be impossible…to undo.
At the heart of this [are] Secure Boot policies. … That stops you from booting up any OS you want on your Windows RT tablet [or] Windows Phone. … Microsoft created and signed a special…policy that disables the…checks, presumably to allow programmers to…boot anything…like a shim that loads a Linux kernel. Now that golden policy has leaked onto the internet. [It] is universal. … It works on x86 and ARM.
People are particularly keen to unlock their ARM-powered [tablets] because Microsoft has all but abandoned the platform. [It] can be used to unlock Windows Phone handsets, too.
If you’re an IT admin who is relying on Secure Boot to prevent…rootkits and bootkits, [this] is going to worry you. … We asked Microsoft for comment, [but] a spokesperson was not immediately available.
What a débâcle. Charlie Osborne effects a story of security panic:
Microsoft has accidentally leaked the keys to the kingdom. … Microsoft’s Secure Boot…is meant to ensure each component of the system boot process is…validated.
For testing…purposes, Microsoft has one particular boot policy [that] disables operating system checks. [The] problem has emerged due to design flaws in the policy loading system.
The researchers reportedly informed Microsoft of their findings between March and April this year. [Microsoft] originally declined to fix the issue. [But] between June and July, Microsoft…awarded a bug bounty.
Can Microsoft patch the issue? One of the Ring Of Lightning researchers, slipstream, tweeted Secure Boot is dead. Here’s why:
bootmgr.efi loads “legacy” policies. … It then loads, checks and merges in the supplemental policies.
The “supplemental” policy does NOT contain a DeviceID. And…they don’t contain any BCD rules either, [so] you can enable testsigning…to load a…self-signed…efi (ie bootkit)!!!
This is very bad!! … A perfect real-world example about why [the FBI’s] idea of backdooring cryptosystems…is very bad!
MS’s first patch attempt…doesn’t do anything useful. … An attacker can just replace a later bootmgr with an earlier one. … It’d be impossible…to revoke every bootmgr…as they’d break install media, recovery partitions, backups, etc.
So what about that government-backdoor angle? Joe “Netflix and” Uchill muses thuswise: [You’re fired -Ed.]
[The] researchers…say their discovery is proof that…backdoors do not work. FBI Director James Comey has been non-committal if he wants a golden key [or] a split key. … But reverse engineering the…keys from this design flaw would be largely the same no matter which method was used.
Meanwhile, stand by for bombastic celebrations in penguin-land. This “Anonymous Coward” quips, Surely you don’t believe the “security” excuse?:
Secure Boot was never really conceived as a way to protect YOU, it merely used the security excuse to protect the one thing Microsoft cares about: Microsoft. … It wasn’t an accident that it…prevented the installation of…Linux, of course, also the reason for MS going for UEFI.
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You have been reading IT Newspro by Richi Jennings, who curates the best bloggy bits, finest forums, and weirdest websites… so you don’t have to. Hatemail may be directed to @RiCHi or [email protected]. Ask your doctor before reading. Your mileage may vary. E&OE.
Main image credit: Francis Flinch (cc:by)