As industry responds to the Spectre and Meltdown cyber vulnerabilities, issuing microcode patches and restructuring the way high-performance microprocessors handle speculative execution, the broader fallout remains unclear: How will IT customers respond?
The realization that virtually every server installed over the past decade, along with millions of iPhones, laptops and other devices are exposed is one thing; the risk that hackers can exploit these techniques to leak passwords, encryption keys or other data across virtual security barriers in cloud-based systems, is another.
For a federal IT community racing to modernize, shut down legacy data centers and migrate government systems to the cloud, worries about data leaks raise new questions about the security of placing data in shared public clouds.
“It is likely that Meltdown and Spectre will reinforce concerns among those worried about moving to the cloud,” said Michael Daniel, president of the Cyber Threat Alliance who was a special assistant to President Obama and the National Security Council’s cybersecurity coordinator until January 2017.
“But the truth is that while those vulnerabilities do pose risks – and all clients of cloud service providers should be asking those providers how they intend to mitigate those risks – the case for moving to the cloud remains overwhelming. Overall, the benefits still far outweigh the risks.”
Adi Gadwale, chief enterprise architect for systems integrator General Dynamics Information Technology (GDIT), says the risks are greater in public cloud environments where users’ data and applications can be side by side with that of other, unrelated users. “Most government entities use a government community cloud where there are additional controls and safeguards and the only other customers are public sector entities,” he says. “This development does bring out some of the deepest cloud fears, but the vulnerability is still in the theoretical stage. It’s important not to overreact.”
How Spectre and Meltdown Work
Spectre and Meltdown both take advantage of speculative execution, a technique designed to speed up computer processing by allowing a processor to start executing instructions before completing the security checks necessary to ensure the action is allowed, Gadwale says.
“Imagine we’re in a track race with many participants,” he explains. “The gun goes off, and some runners start too quickly, just before the gun goes off. We have two options: Stop the runners, review the tapes and disqualify the early starters, which might be the right thing to do but would be tedious. Or let the race complete and then afterward, discard the false starts.
“Speculative execution is similar,” Gadwale continues. “Rather than leave the processor idle, operations are completed while memory and security checks happen in parallel. If the process is allowed, you’ve gained speed; if the security check fails, the operation is discarded.”
This is where Spectre and Meltdown come in. By executing code speculatively and then exploiting what happens by means of shared memory mapping, hackers can get a sneak peek into system processes, potentially exposing very sensitive data.
“Every time the processor discards an inappropriate action, the timing and other indirect signals can be exploited to discover memory information that should have been inaccessible,” Gadwale says. “Meltdown exposes kernel data to regular user programs. Spectre allows programs to spy on other programs, the operating system and on shared programs from other customers running in a cloud environment.”
The technique was exposed by a number of different research groups all at once, including Jann Horn, a researcher with Google’s Project Zero, at Cyberus Technology, Graz University of Technology, the University of Pennsylvania, the University of Maryland and the University of Adelaide.
The fact that so many researchers were researching the same vulnerability at once – studying a technique that has been in use for nearly 20 years – “raises the question of who else might have found the attacks before them – and who might have secretly used them for spying, potentially for years,” writes Andy Greenberg in Wired. But speculation that the National Security Agency might have utilized the technique was shot down last week when former NSA offensive cyber chief Rob Joyce (Daniel’s successor as White House cybersecurity coordinator) said NSA would not have risked keeping hidden such a major flaw affecting virtually every Intel processor made in the past 20 years.
The Vulnerability Notes Database operated by the CERT Division of the Software Engineering Institute, a federally funded research and development center at Carnegie Mellon University sponsored by the Department of Homeland Security, calls Spectre and Meltdown “cache side-channel attacks.” CERT explains that Spectre takes advantage of a CPU’s branch prediction capabilities. When a branch is incorrectly predicted, the speculatively executed instructions will be discarded, and the direct side-effects of the instructions are undone. “What is not undone are the indirect side-effects, such as CPU cache changes,” CERT explains. “By measuring latency of memory access operations, the cache can be used to extract values from speculatively-executed instructions.”
Meltdown, on the other hand, leverages an ability to execute instructions out of their intended order to maximize available processor time. If an out-of-order instruction is ultimately disallowed, the processor negates those steps. But the results of those failed instructions persist in cache, providing a hacker access to valuable system information.
It’s important to understand that there are no verified instances where hackers actually used either technique. But with awareness spreading fast, vendors and operators are moving as quickly as possible to shut both techniques down.
“Two weeks ago, very few people knew about the problem,” says CTA’s Daniel. “Going forward, it’s now one of the vulnerabilities that organizations have to address in their IT systems. When thinking about your cyber risk management, your plans and processes have to account for the fact that these kinds of vulnerabilities will emerge from time to time and therefore you need a repeatable methodology for how you will review and deal with them when they happen.”
The National Cybersecurity and Communications Integration Center, part of the Department of Homeland Security’s U.S. Computer Emergency Readiness Team, advises close consultation with product vendors and support contractors as updates and defenses evolve.
“In the case of Spectre,” it warns, “the vulnerability exists in CPU architecture rather than in software, and is not easily patched; however, this vulnerability is more difficult to exploit.”
Vendors Weigh In
Closing up the vulnerabilities will impact system performance, with estimates varying depending on the processor, operating system and applications in use. Intel reported Jan. 10 that performance hits were relatively modest – between 0 and 8 percent – for desktop and mobile systems running Windows 7 and Windows 10. Less clear is the impact on server performance.
Amazon Web Services (AWS) recommends customers patch their instance operating systems to prevent the possibility of software running within the same instance leaking data from one application to another.
GDIT’s Gadwale said performance penalties may be short lived, as cloud vendors and chipmakers respond with hardware investments and engineering changes. “Servers and enterprise class software will take a harder performance hit than desktop and end-user software,” he says. “My advice is to pay more attention to datacenter equipment. Those planning on large investments in server infrastructure in the next few months should get answers to difficult questions, like whether buying new equipment now versus waiting will leave you stuck with previous-generation technology. Pay attention: If the price your vendor is offering is too good to be true, check the chipset!”
Bypassing Conventional Security
The most ominous element of the Spectre and Meltdown attack vectors is that they bypass conventional cybersecurity approaches. Because the exploits don’t have to successfully execute code, the hackers’ tracks are harder to exploit.
Says CTA’s Daniel: “In many cases, companies won’t be able to take the performance degradation that would come from eliminating speculative processing. So the industry needs to come with other ways to protect against that risk.” That means developing ways to “detect someone using the Spectre exploit or block the exfiltration of information gleaned from using the exploit,” he added.
Longer term, Daniel suggested that these latest exploits could be a catalyst for moving to a whole different kind of processor architecture. “From a systemic stand-point,” he said, “both Meltdown and Spectre point to the need to move away from the x86 architecture that still undergirds most chips, to a new, more secure architecture.”