Sunday, November 20th 2011
Windows 8 Secure Boot Feature: Not So Secure?
We have brought you the potential perils of the upcoming UEFI Forum-implemented - www.uefi.org - Windows 8 secure boot feature here, here and here. However, it appears that it may not be so 'secure' after all, since there appears to be a surefire way to circumvent it, at least for the moment, while it's in development.
Softpedia has scored an exclusive interview with security researcher Peter Kleissner, who has created various Windows (XP, Server 2003 etc) "bootkits", which allow OS infection at the highest privilege level, giving unrestricted access to the whole of the PC. His latest one, called Stoned Lite, shows how the Windows 8 secure boot process, still in development, can be subverted, as it stands. He is planning to release details of how the code works at the upcoming International Malware Conference (MalCon) - malcon.org - that will take place in India on November 25th. It appears that the real vulnerability exists in the legacy BIOS boot procedure, not in Microsoft's implementation of secure boot, as Kleissner said:
And as Softpedia put it:
Still, it makes Microsoft's bold claim in September, that:
Note that Kleissner will not be at MalCon in person, because he will be attending another conference held on the same day, the European Bitcoin Conference in Prague, where he will show "how to re-direct locally initiated BitCoin transactions, but also show how the BitCoin wallet can be secured better against theft." Therefore, someone else will go in his place to deliver the message, or he may pre-record it.
Finally, while this is a big step forward for PC security, like every other security improvement, there's always a hack to get around it with time somehow, somewhere, which can then be patched and hacked and patched... However, in this case, when the secure boot system goes live and a core vulnerability is found in the UEFI or some other low level component, patching won't be so simple, or maybe even impossible, due to its low level nature. So, once again the suspicion remains that this whole 'initiative' is a backdoor to locking out competing operating systems such as Linux and to DRM your whole PC to 'protect' the profits of big content, in a similar way they already do on games consoles.
There's a lot of big corporate interests riding on secure boot, so do not ever rule out the possibility that it will be subverted to further them.
Softpedia has scored an exclusive interview with security researcher Peter Kleissner, who has created various Windows (XP, Server 2003 etc) "bootkits", which allow OS infection at the highest privilege level, giving unrestricted access to the whole of the PC. His latest one, called Stoned Lite, shows how the Windows 8 secure boot process, still in development, can be subverted, as it stands. He is planning to release details of how the code works at the upcoming International Malware Conference (MalCon) - malcon.org - that will take place in India on November 25th. It appears that the real vulnerability exists in the legacy BIOS boot procedure, not in Microsoft's implementation of secure boot, as Kleissner said:
The problem with the legacy startup is that no one verifies the MBR, which makes it the vulnerable point. With UEFI and secure boot, all the boot applications and drivers have to be signed (otherwise they won't be loaded). You can compare it to TPM, although Arie van der Hoeven from Microsoft announced that the secure boot feature is mandatory for OEMs who want to be UEFI certified. It is a good message that security is not an option.
And as Softpedia put it:
Stoned Lite actually works by infecting the MBR, while storing its components "outside the normal file system." Startup files are "hooked" and "patched" before Windows starts, these files being changed in Windows 7.Kleissner explained that the basic way Stoned Lite works is by using command line escalation:
As payload I use the command line privilege escalation. Once whoami.exe is launched, it elevates the cmd.exe process rights to SYSTEM by overwriting its security token with a duplicated system process one.So, this problem is only present if someone has physical access to the computer and is able to boot off a CD or USB stick. Therefore, this security vulnerability will have no impact in many scenarios where the threat of this kind of attack is very low. Examples include the home environment (usually) and data centres with very good physical security and the other measures they have in place. The most likely place for problems could be in workplaces where someone boots a PC after hours and installs a keylogger or other malware on the system. A significant threat, to be sure. However, despite this vulnerability, secure boot still makes conventional malware attacks useless, such as drive-by downloads from malicious or hacked websites and opening attachments from spam emails, among the many infection vectors around.
Additionally it will patch the password validation function (MsvpPasswordValidate) so you can use any password for any local user account to log on. You will be able to start Stoned Lite from a USB flash drive or CD where it will be only active in memory.
Still, it makes Microsoft's bold claim in September, that:
Secured boot stops malware in its tracks and makes Windows 8 significantly more resistant to low-level attacks. Even when a virus has made it onto your PC, Windows will authenticate boot components to prevent any attempt to start malware before the operating system is up and running.a little less reassuring, doesn't it?
Note that Kleissner will not be at MalCon in person, because he will be attending another conference held on the same day, the European Bitcoin Conference in Prague, where he will show "how to re-direct locally initiated BitCoin transactions, but also show how the BitCoin wallet can be secured better against theft." Therefore, someone else will go in his place to deliver the message, or he may pre-record it.
Finally, while this is a big step forward for PC security, like every other security improvement, there's always a hack to get around it with time somehow, somewhere, which can then be patched and hacked and patched... However, in this case, when the secure boot system goes live and a core vulnerability is found in the UEFI or some other low level component, patching won't be so simple, or maybe even impossible, due to its low level nature. So, once again the suspicion remains that this whole 'initiative' is a backdoor to locking out competing operating systems such as Linux and to DRM your whole PC to 'protect' the profits of big content, in a similar way they already do on games consoles.
There's a lot of big corporate interests riding on secure boot, so do not ever rule out the possibility that it will be subverted to further them.
35 Comments on Windows 8 Secure Boot Feature: Not So Secure?
"The researcher claims that the real issue exists in legacy boot procedures, not in the Redmond company's new feature." debunks this whole 'article' and the Softpedia headline is sensational driven by speculation.
- Linux
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- Linux
- Oh and OSX
Here is a statement from a Kernal Developer at Red Hat:I'm not sure this exploits the legacy BIOS but rather it exploits the legacy boot method on MBR drives, injecting a signed key before the OS boots, which you are correct in that it has nothing to do with Windows 8. And the simplest fix would just be to require boot drives use GPT when Secure Boot is enabled in UEFI.But sheesh, I didn't think I hated the whole IT industry? :eek: :)
The vulnerability isn't in the OS itself. From the looks of it, the UEFI still contains legacy BIOS code that's causing the problem, as the MBR isn't checked. Once that code is updated, this vulnerability will be fixed. Therefore, it's fair to say that any OS, Linux etc at this point would be vulnerable to Stoned Lite.
Hopefully you're right about all this being an overreaction. Only time will tell for sure, but in the meantime, the previous stories I linked to explain why it's a potential problem and people shouldn't be complacent about it.
Secure boot also sounds like it will make security software redundant, doesn't it? I suspect that it won't in practice, though.