New Spectre attack enables secrets to be leaked over a network

Enlarge (credit: Pete)

When the Spectre and Meltdown attacks were disclosed earlier this year, the initial exploits required an attacker to be able to run code of their choosing on a victim system. This made browsers vulnerable, as suitably crafted…

Enlarge (credit: Pete)

When the Spectre and Meltdown attacks were disclosed earlier this year, the initial exploits required an attacker to be able to run code of their choosing on a victim system. This made browsers vulnerable, as suitably crafted JavaScript could be used to perform Spectre attacks. Cloud hosts were susceptible, too. But outside these situations, the impact seemed relatively limited.

That impact is now a little larger. Researchers from Graz University of Technology, including one of the original Meltdown discoverers, Daniel Gruss, have described NetSpectre: a fully remote attack based on Spectre. With NetSpectre, an attacker can remotely read the memory of a victim system without running any code on that system.

All the variants of the Spectre attacks follow a common set of principles. Each processor has an architectural behavior (the documented behavior that describes how the instructions work and that programmers depend on to write their programs) and a microarchitectural behavior (the way an actual implementation of the architecture behaves). These can diverge in subtle ways. For example, architecturally, a program that loads a value from a particular address in memory will wait until the address is known before trying to perform the load. Microarchitecturally, however, the processor might try to speculatively guess at the address so that it can start loading the value from memory (which is slow) even before it's absolutely certain of which address it should use.

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New Spectre-like attack uses speculative execution to overflow buffers

Enlarge (credit: Aurich Lawson / Getty Images)

When the Spectre and Meltdown attacks were disclosed earlier this year, the expectation was that these attacks would be the first of many, as researchers took a closer look at the way that the speculat…

Enlarge (credit: Aurich Lawson / Getty Images)

When the Spectre and Meltdown attacks were disclosed earlier this year, the expectation was that these attacks would be the first of many, as researchers took a closer look at the way that the speculative execution in modern processors could be used to leak sensitive information and undermine the security of software running on those processors. In May, we saw the speculative store bypass, and today we have a new variant on this theme: speculative buffer overflows, discovered by Vladimir Kiriansky at MIT and independent researcher Carl Waldspurger.

All the attacks follow a common set of principles. Each processor has an architectural behavior (the documented behavior that describes how the instructions work and that programmers depend on to write their programs) and a microarchitectural behavior (the way an actual implementation of the architecture behaves). These can diverge in subtle ways. For example, architecturally, a program that loads a value from a particular address in memory will wait until the address is known before trying to perform the load. Microarchitecturally, however, the processor might try to speculatively guess at the address so that it can start loading the value from memory (which is slow) even before it's absolutely certain of which address it should use.

If the processor guesses wrong, it will ignore the guessed-at value and perform the load again, this time with the correct address. The architecturally defined behavior is thus preserved. But that faulty guess will disturb other parts of the processor—in particular the contents of the cache. These microarchitectural disturbances can be detected and measured, allowing a malicious program to make inferences about the values stored in memory.

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AMD systems gain Spectre protection with latest Windows fixes

Enlarge / An AMD Ryzen. (credit: Fritzchens Fritz)
The latest Windows 10 fixes, released as part of yesterday’s Patch Tuesday, enable protection against the Spectre variant 2 attacks on systems with AMD processors.
Earlier this year, attacks that ex…

Enlarge / An AMD Ryzen. (credit: Fritzchens Fritz)

The latest Windows 10 fixes, released as part of yesterday's Patch Tuesday, enable protection against the Spectre variant 2 attacks on systems with AMD processors.

Earlier this year, attacks that exploit the processor's speculative execution were published with the names Meltdown and Spectre, prompting a reaction from hardware and software companies. AMD chips are immune to Meltdown but have some vulnerability to the two Spectre variants. Spectre variant 1 requires application-level fixes; variant 2 requires operating system-level alterations.

Both Intel and AMD have released microcode updates to alter their processor behavior to give operating systems the control necessary to protect against Spectre variant 2. Microsoft has been shipping the Intel microcode, along with the operating system changes necessary to use the microcode's new features, for several weeks now; with yesterday's patch, similar protections are now enabled on AMD machines.

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AMD promises firmware fixes for security processor bugs

Enlarge / AMD’s Ryzen die. Threadripper has two of these in a multi-chip module. Epyc has four of them. (credit: AMD)
AMD has responded to the reports last week of a range of security flaws affecting its Platform Security Processor (PSP) and chipset…

Enlarge / AMD's Ryzen die. Threadripper has two of these in a multi-chip module. Epyc has four of them. (credit: AMD)

AMD has responded to the reports last week of a range of security flaws affecting its Platform Security Processor (PSP) and chipset. The company acknowledges the bugs and says that, in coming weeks, it will have new firmware available to resolve the PSP bugs. These firmware fixes will also mitigate the chipset bugs.

Israeli firm CTS identified four separate flaw families, naming them Masterkey (affecting Ryzen and Epyc processors), Ryzenfall (affecting Ryzen, Ryzen Pro, and Ryzen Mobile), Fallout (hitting only Epyc), and Chimera (applying to Ryzen and Ryzen Pro systems using the Promonotory chipset).

Masterkey, Ryzenfall, and Fallout are all problems affecting the Platform Security Processor (PSP), a small ARM core that's integrated into the chips to provide certain additional features such as a firmware-based TPM security module. The PSP has its own firmware and operating system that runs independently of the main x86 CPU. Software running on the x86 CPU can access PSP functionality using a device driver, though this access is restricted to administrator/root-level accounts.

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