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Thursday, 16 August 2018 06:31

OpenBSD chief slams Intel, says more CPU flaws likely to be found Featured

Theo de Raadt: "We asked repeatedly, but Intel provided no advance notice. We did not even receive replies to our requests for dialogue." Theo de Raadt: "We asked repeatedly, but Intel provided no advance notice. We did not even receive replies to our requests for dialogue." Supplied

The head of the OpenBSD project, Theo de Raadt, has warned that more flaws related to speculative execution in Intel CPUs are likely to be found and that the two vulnerabilities found by Intel, as a result of examining the Foreshadow bug — found by two independent teams — are cause for much worry.

De Raadt told iTWire that Foreshadow was "the wrong name. It is one of three side effects of a very poor Intel decision".

And he added in a mailing list post, "CVE-2018-3615 (Foreshadow) is by receiving the most press which is amazing considering it is by far the most boring of the 3, since very few few people give a rat's ass about SGX – who cares if SGX is broken when the CPU can't run your OS safely? Some convincing press agencies were hired, I guess, and have performed a masterful job of distracting."

Of the other two flaws, he said: "CVE-2018-3620 and CVE-2018-3646 are huge, and affect everyone with an OS which wasn't already paranoid."

In a post to one of the OpenBSD mailing lists, de Raadt said: "We had some idea this class of problem was coming, through hints we received from others and an extremely cynical perspective that has developed.

"We believe Intel CPUs do almost no security checks up-front, but defer checks until instruction retire. As a result we believe similar issues will be coming in the future.

"We asked repeatedly, but Intel provided no advance notice. We did not even receive replies to our requests for dialogue."

On Wednesday, Intel released details of three vulnerabilities in its Core and Xeon processor lines, all of which involve exploiting the feature known as speculative execution where processors attempt to anticipate and execute instructions.

While investigating the first, known as Foreshadow, Intel discovered two additional vulnerabilities. The original flaw — CVE-2018-3615 — allows for the extraction of data from software guard extension enclaves.

"On a side note, AMD CPUs are not vulnerable to this problem. Currently it is believed their address translation layer works according to spec," de Raadt said.

In June, in what now appears to be a very wise decision, he announced that OpenBSD would be disabling hyperthreading support for Intel CPUS due to fear of data leaks in a manner similar to that caused by the Spectre flaws in Intel processors announced earlier this year.

De Raadt said the original flaw — Foreshadow — was "boring, because only a few people use SGX. The Foreshadow guys found the artefact of a problem, which ends up affecting general OS operations".

The other two flaws affect virtual machines, hypervisors, operating system kernel memory, and system management mode memory.

Two separate advisories were issued for these flaws: CVE-2018-3620 (for operating systems and SMM) and CVE-2018-3646 (for virtualisation).

Intel revealed details of two flaws, named Meltdown and Spectre, which used speculative execution to attack systems, in January. At the time, it was thought that SGX was immune to speculative execution attacks.

De Raadt said: "CVE-2018-3620 matters for the host OS. We have reviewed our pmap module and it appears like we never invalidate a PTE by clearing the 'valid' bit alone, we always clear the PTE to 0 entirely. Page 0 of physical memory is unused. As well, we don't support Wine (which has VA 0 / PA 0 issues); we don't support 32-bit emulation in 64-bit mode which makes things trickier, and we have SMT disabled by default which reduces the risk patterns further.

"CVE-2018-3646 relates to the same bug, but considers the cross-domain impact upon entering VMs, which obviously run in different security domains. A patch should arrive soon to flush the L1 cache before vmenter, so that an incorrectly accessed PTE can't read data from another domain. Another aspect of the risk in this area goes away if SMT is disabled, so keep it disabled!"

When Meltdown and Spectre were announced, de Raadt slammed Google and Intel for handling the disclosure "in an incredibly bad way".

"Only Tier-1 companies received advance information, and that is not responsible disclosure – it is selective disclosure," he told iTWire at the time. "Everyone below Tier-1 has just gotten screwed."

OpenBSD has an enviable reputation for security and runs some of the public servers with the longest uptimes.

De Raadt himself is obsessed with security, and has as his aim the provision of an operating system that has a secure default install. OpenBSD has had only two remote vulnerabilities in its default install since the project forked from NetBSD in 1996.

Google and Microsoft have issued their own advisories about the vulnerabilities. Intel's advisory is here.

Videos: courtesy Intel and Foreshadow vulnerability researchers

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Sam Varghese

Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.

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