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Could secure boot lead to Linux v Linux strife?

Could Microsoft's implementation of secure boot be, one day, the reason why Linux vendors get into strife with each other? Could Oracle one day go to Microsoft in order to get a key issued to Red Hat by Microsoft revoked?

Kernel developer Matthew Garrett raised this possibility last year, within the context of a discussion that focused on the additional measures that have to be implemented for Linux systems to satisfy all the requirements of secure boot, so that there is no door left open for Microsoft to revoke the key issued to any Linux distribution.

Secure boot is a feature of the Unified Extensible Firmware Interface, the replacement for the motherboard firmware or BIOS. It has been implemented by Microsoft in a manner that effectively prevents easy booting of other operating systems on machines which have secure boot enabled.

An exchange of cryptographic keys takes place at boot-time so that a system can verify that the operating system attempting to boot is a genuine one, and not malware. There are further key exchanges along the way. Microsoft controls the key-signing authority, and thus anyone who wishes to boot an operating system on hardware certified for Windows 8 has to buy a Microsoft key.

In order to satisfy Microsoft's requirements, there should be no possibility of using Linux to attack a Windows 8 system on the same machine, and while the discussion centred on this, Garrett, at the time an employee of Red Hat, wrote: "Linux vendors may care about Linux on Linux attacks. It's all fun and games until Oracle get Microsoft to revoke Red Hat's signature."

Earlier in the discussion, developer Eric Paris had raised the possibility of Linux on Linux attacks, to which another developer, James Bottomley, who is also affiliated with the Linux Foundation, wrote: "Microsoft doesn't really care about Linux on Linux attacks, so preventing or allowing them isn't going to get a distro key revoked."

In response to Garrett, Bottomley said: "I agree that's a possibility. However, I think the court of public opinion would pillory the first Commercial Linux Distribution that went to Microsoft for the express purpose of revoking their competition's right to boot. It would be commercial suicide."

Garrett elaborated on his point by saying: "Oracle are something of a vexatious litigant as far as the court of public opinion is concerned, but even without that it could be a customer who complains. If you're personally comfortable with a specific level of security here, that's fine - but it's completely reasonable for others to feel that there are valid technical and commercial concerns to do this properly."

Senior Linux developer Alan Cox did not think much of Garrett's comments, responding to the first post with "Fear uncertainty and doubt (and if you think Oracle are going to do that I suspect your lawyers should deal with it)".

Oracle Unbreakable Linux - the company's slogan for selling the operating system - is not a distribution per se. Oracle does what CentOS does - take Red Hat Enterprise Linux, strip out the trademarks and then provide it to customers.

When Garrett responded, claiming "Lawyers won't remove blacklist entries," Cox reiterated his statement, adding a friendly warning to Garrett: "Fear Uncertainty and Doubt. Courts do, injunctions do, the possibility of getting caught with theirs (sic) hands in the till does. But I suspect your lawyers should also deal with public comments about Oracle such as the one you've made before you make them in public 8)."

Meanwhile, the process of satisfying Microsoft's secure boot requirements is continuing to make demands on developers. Two recent moves have been the release of patches for disabling hibernation in the kernel and also disabling kexec.

Hibernation needs to be disabled because the Linux image that returns from such a state cannot be verified; this is a requirement of the secure boot security model. And kexec needs to be disabled because it is a system call that can replace the running kernel with a different program.

These patches will have to be the default for Linux distributions that want to conform to the requirements of secure boot and not get the keys they buy from Microsoft blacklisted.

In short, Microsoft is asking Linux developers to jump and they are merely asking, "how high?"

As senior Debian developer and veteran sysadmin Craig Sanders put it to Garret on another discussion forum: "You mean well and have good intentions, but you are enabling Microsoft in their aim to be gatekeeper of what software is permitted to execute.

"Aside from the old adage about the road to hell, the trouble with your work is that it is short-sighted and short-term pragmatism (you have what appears to be a technical problem and want to solve it now) with no regard for the long-term consequences. One day you will realise exactly what you have enabled and come to bitterly regret it. Unfortunately, you won't be the only one to suffer the consequences."

Both efforts to create a first-stage bootloader for Linux on secure boot-enabled machines - Garrett's shim and Bottomley's effort on behalf of the Linux Foundation - appear to be driven by corporate needs. As Sanders put it, "Appeasement on the secureboot issue may be good, cheap, and convenient policy for RH and other corporate linux vendors. Not for anyone else."

Bottomley, meanwhile, after failing to get his initial code submission for a first-stage bootloader through the Microsoft bureaucracy, has recrafted the solution and submitted it to Microsoft on January 21. Bottomley wrote in his own blog that the solution had to be recrafted so that it would work with the Gummiboot simple UEFI boot manager. The Linux Foundation's goal is to provide a first-stage bootloader that works with all distributions. Bottomley expects the recrafted solution to be available soon after it is passed by Microsoft.

It is slowly becoming apparent that appeasing Microsoft is not a one-day or one-month or even a one-year affair. It is a shameful state to be in, but the Linux community seems incapable of feeling shame anymore.


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Sam Varghese

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A professional journalist with decades of experience, Sam for nine years used DOS and then Windows, which led him to start experimenting with GNU/Linux in 1998. Since then he has written widely about the use of both free and open source software, and the people behind the code. His personal blog is titled Irregular Expression.


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