Secure OS Qubes fixes security bugs, confirms no government backdoors

Qubes. a Fedora-based OS that aims to improve desktop security through virtualised isolated environments, has released two fixes for “security problems” and its first statement confirming that it hasn’t been ordered by a government to install a backdoor.

Running a highly secure desktop OS that's difficult to manage might not be everyone’s cup of tea, but in a world where there are reasons to fear government-ordered backdoors, such an OS could be useful.

Qubes OS was launched in 2012 by Polish security firm Invisible Things Lab, led by virtualisation buff Joanna Rutkowska, offering users a way to run applications inside separate Xen-based virtualised “security domains”. In practice, that means, for example, running different instances (VMs) of the same browser for personal, work and banking security domains.

While the design allows users to run activities which have different risk profiles in a different domain, in the name of usability, Qubes lets users copy and paste data from one domain to another.

Security researcher Jann Horn recently found that this process, handled in Qubes’ clipboard feature — which lets users move data between “AppVMs” — is vulnerable to timing attacks that could allow an attacker to surreptitiously inject false contents in the clipboard or steal data that has been pasted to the clipboard.

While Rutkowska believes Jann’s discoveries are “theoretical”, on Monday she nonetheless urged users to apply updates that fix the “subtle race condition” affecting Qubes’ global clipboard management.

According to Rutkowska, both attacks would be difficult to pull off because they require precise timing. Additionally, the first attack depends on the ability of the attacker “to observe any relevant events in the system outside of the attacker’s AppVM” while in the second scenario, the attacker can’t force a user to copy information to Qubes’ “global clipboard”, she said.

“Additional complication for the 1st attack (clipboard injection) is that the attacker has typically no way of knowing what application the user intends to paste the buffer to, nor its state,” she noted.

“Additional complication for the 2nd attack (clipboard stealing) is freezing of all the AppVMs windows for the whole period while the attacker is waiting for the user to issue copy operation to the global clipboard in another AppVM.”

She said both issues have been resolved.

A second attack compromises the Qubes Core API and could impact programs that use the API incorrectly, according to Rutkowska,

Again, Rutkowska believes the risks are theoretical but still advised users to patch the issue.

Qubes core developers also signed its first so-called “warrant canary”, which is a statement of assurance, usually by internet-based service providers, to users that their product hasn’t been tampered with at the request of government authorities.

“Even though we're not providing any kind of services (such as e.g. email hosting), that could be searched or tapped by authorities, there are other possibilities that worry us, in the light of various recent law "developments", such as those that might be coercing people to hand over their private keys to authorities,” wrote Rutkowska.

In the name of transparency, Qubes also provided a disclaimer noting that the warrant canary scheme could be undermined despite its best efforts.

“Although signing the declaration makes it very difficult for a third party to produce arbitrary declarations, it does not prevent them from using force, or other means like blackmail, or compromise of the signers' laptops, to coerce us to produce false declarations.”

Qubes' next canary statement will be published in the first week of March 2015.

This article is brought to you by Enex TestLab, content directors for CSO Australia.

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Tags AppVMsPolish securitywarrant canaryXen-based virtualiseJoanna RutkowskaSecurity researcherRutkowskagovernment-ordered backdoorsJann Hornsecurity bugsOS Qubes

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