Open source luminary Ian Jackson has hit back at criticism of the Xen Project's security.

The project last week nixed nine nasties, including a seven-year-old guest-host escape, and has patched a string of bugs this year including some that threatened to disrupt cloud services.

The many bug squashed of late has seen some rumblings, and this rather strident effort from Marek Marczykowski-Góreck of InvisbleThings Lab takes things to a new level with some strongly-worded criticism:

“... it is really shocking that such a bug has been lurking in the core of the hypervisor for so many years. In our opinion the Xen project should rethink their coding guidelines and try to come up with practices and perhaps additional mechanisms that would not let similar flaws to plague the hypervisor ever again (assert-like mechanisms perhaps?). Otherwise the whole project makes no sense, at least to those who would like to use Xen for security-sensitive work.

Jackson's a Gandalf-grade open source developer: he wrote dpkg , among other fine pieces of code, and has served in very senior roles in open source development efforts. He now works for Citrix and works on the Xen security team. In the latter role he felt sufficiently moved by Marczykowski-Góreck's to take to the Xen blog with a personal response.

The thrust of Jackson's argument is that everything is insecure, but the Xen Project treats its code with the best known remedy: sunlight.

“Unlike almost all corporations, and even most Free Software projects, the Xen Project properly discloses, via an advisory, every vulnerability discovered in supported configurations. We also often publish advisories about vulnerabilities in other relevant projects, such as Linux and QEMU.”

“When I worked for a security hardware vendor I was constantly under pressure to explain why we needed to do a formal advisory for our bugs,” he adds. “That is what security-conscious users expect, but our competitors’ salesfolk would point to our advisories and say that our products were full of bugs. Their products had no publicly disclosed security bugs, so they would tell naive customers that their products had no bugs.”

Jackson also wrote that “over the last few years the Xen Project’s code review process has become a lot more rigorous” and says “I do think Xen probably has fewer critical security bugs than other hypervisors (whether Free or proprietary). It’s the best available platform for building high security systems. The Xen Project’s transparency is very good for Xen’s users.”

“Ultimately, of course, a Free Software project like Xen is what the whole community makes it,” he continues. “In the project as a whole we get a lot more submissions of new functionality than we get submissions aimed at improving the security.”

“So personally, I very much welcome the contributions made by security-focused contributors – even if that includes criticism.”

Jackson's post is yours to read, here. ®