Microsoft Secure Boot Firmware may Block Linux Booting

Computer scientists warn that proposed changes in firmware specifications may make it impossible to run “unauthorised” operating systems such as Linux and FreeBSD on PCs.

Proposed changes to the Unified Extensible Firmware Interface (UEFI) firmware specifications would mean PCs would only boot from a digitally signed image derived from a keychain rooted in keys built into the PC. Microsoft is pushing to make this mandatory in a move that could not be overridden by users and would effectively exclude alternative operating systems, according to Professor Ross Anderson of Cambridge University and other observers.

UEFI is a successor to the BIOS ROM firmware designed to shorten boot times and improve security. The framework, a key part of Windows 8, is designed to work on a variety of CPU architectures.

If the draft for UEFI is adopted without modification, then any system that ships with only OEM and Microsoft keys will not boot a generic copy of Linux. A signed version of Linux would work, but this poses problems, as tech blogger Matthew Garrett explains.

Garrett writes:

Firstly, we'd need a non-GPL bootloader. Grub 2 is released under the GPLv3, which explicitly requires that we provide the signing keys. Grub is under GPLv2 which lacks the explicit requirement for keys, but it could be argued that the requirement for the scripts used to control compilation includes that. It's a grey area, and exploiting it would be a pretty good show of bad faith.

Secondly, in the near future the design of the kernel will mean that the kernel itself is part of the bootloader. This means that kernels will also have to be signed. Making it impossible for users or developers to build their own kernels is not practical. Finally, if we self-sign, it's still necessary to get our keys included by ever OEM.

There's no indication that Microsoft will prevent vendors from providing firmware support for disabling this feature and running unsigned code. However, experience indicates that many firmware vendors and OEMs are interested in providing only the minimum of firmware functionality required for their market.

Garrett concluded that there is no need to panic just yet.

The upshot of the changes is that considerable roadblocks might be placed in the way of running alternative operating systems on PCs. Anderson describes this as a return to the rejected Trusted Computing architecture – which at that point involved force-feeding DRM copy-protection restrictions – which may be far worse than its predecessor.

The professor said:

These issues last arose in 2003, when we fought back with the Trusted Computing FAQ and economic analysis. That initiative petered out after widespread opposition. This time round the effects could be even worse, as 'unauthorised' operating systems like Linux and FreeBSD just won’t run at all. On an old-fashioned Trusted Computing platform you could at least run Linux – it just couldn’t get at the keys for Windows Media Player.

The extension of Microsoft’s OS monopoly to hardware would be a disaster, with increased lock-in, decreased consumer choice and lack of space to innovate.

Anderson concludes that the technology might violate EU competition law in a rallying call on Cambridge University's Light Blue Touchpaper blog here.