3 ms·

> The researchers said that it’s capable of locating and leaking a Linux computer’s root password hash from physical memory in about 28 minutes when running the

> The researchers said that it’s capable of locating and leaking a Linux computer’s root password hash from physical memory in about 28 minutes when running the Intel CPUs and in about 6 minutes for AMD CPUs. Given this attack vector, it makes some sense for relatively static secrets like these to be moved into something like the Secure Enclave where the CPU can perform signature verification but never store the secret itself in memory or cache. I know other ARM-based SoCs have these too. So presumably Intel and AMD offer something like this in their latest-generation CPUs?

kramerger 4y ago
Maybe... AMD has the Secure Processor (an ARM), but it has other duties right now, such as system and VM memory encryption.
saagarjha 4y ago
Putting something in an enclave doesn’t magically make it impervious to side-channel attacks.
- nomel 4y ago
  > doesn’t magically I would say "by design" is much easier to achieve since physical space, slow interconnects, and "dumb" logic can be put between the two.
- wyldfire 4y ago
  Here's how Apple describes their design of the Secure Enclave. I'd figure that Qualcomm, NXP, AMD, etc have a similar design. > The Secure Enclave Processor provides the main computing power for the Secure Enclave. To provide the strongest isolation, the Secure Enclave Processor is dedicated solely for Secure Enclave use. This helps prevent side-channel attacks that depend on malicious software sharing the same execution core as the target software under attack. > The Secure Enclave Processor runs an Apple-customized version of the L4 microkernel. It’s designed to operate efficiently at a lower clock speed that helps to protect it against clock and power attacks. The Secure Enclave Processor, starting with the A11 and S4, includes a memory-protected engine and encrypted memory with anti-replay capabilities, secure boot, a dedicated random number generator, and its own AES engine.
jeroenhd 4y ago
Intel's Software Guard Extensions were supposed to run at a higher, inaccessible privilege level on consumer CPUs and that turned out to be susceptible to side channel attacks. ARM TrustZone was defeated through cache latency measurements on Android in 2016, though that specific flaw might have been patched since. Perhaps with an entirely separate chip running its own OS with its own RAM and IO, you could work with secrets, but traditional secure chips have so far been far from a silver bullet. I think the Intel Management Engine is close enough to the system CPU that it is probably affected by side channel attacks, but perhaps AMD's PSP is removed far enough to nullify the effect.
- mike_hearn 4y ago
  SGX was patched to solve those issues though. This is one of the issues with the security and side channels space: often there are mitigations powerful enough to stop attacks, but people don't remember them being rolled out. They recall the attack, say "oh well that is broken forever" and never re-visit the issue. As I mention elsewhere, an enclave is a good construct to use here because you're explicitly signalling to the CPU that the memory space has unusually sensitive secrets and you're willing to lose performance to protect them.
  - jeroenhd 4y ago
    That's true, but the point is that simply relying on security extensions is no guarantee for safety. If it was broken before, the theoretical separation isn't complete enough to guarantee it won't be broken again. SGX is already being phased out by Intel for consumer/workstation products so I think they've given up on the concept themselves. I don't think they're supporting an alternative on consumer products either. Even if their server/enterprise implementation is secure enough, it won't protect against developers having their SSH keys exfiltrated by a game running in their browser during their downtime. I think externalising the security mechanism is a good idea, but the current implementations simply aren't good enough to combat this issue.
    - mike_hearn 4y ago

kramerger 4y ago

Maybe... AMD has the Secure Processor (an ARM), but it has other duties right now, such as system and VM memory encryption.

saagarjha 4y ago

Putting something in an enclave doesn’t magically make it impervious to side-channel attacks.

nomel 4y ago
> doesn’t magically I would say "by design" is much easier to achieve since physical space, slow interconnects, and "dumb" logic can be put between the two.
wyldfire 4y ago
Here's how Apple describes their design of the Secure Enclave. I'd figure that Qualcomm, NXP, AMD, etc have a similar design. > The Secure Enclave Processor provides the main computing power for the Secure Enclave. To provide the strongest isolation, the Secure Enclave Processor is dedicated solely for Secure Enclave use. This helps prevent side-channel attacks that depend on malicious software sharing the same execution core as the target software under attack. > The Secure Enclave Processor runs an Apple-customized version of the L4 microkernel. It’s designed to operate efficiently at a lower clock speed that helps to protect it against clock and power attacks. The Secure Enclave Processor, starting with the A11 and S4, includes a memory-protected engine and encrypted memory with anti-replay capabilities, secure boot, a dedicated random number generator, and its own AES engine.

jeroenhd 4y ago

Intel's Software Guard Extensions were supposed to run at a higher, inaccessible privilege level on consumer CPUs and that turned out to be susceptible to side channel attacks. ARM TrustZone was defeated through cache latency measurements on Android in 2016, though that specific flaw might have been patched since. Perhaps with an entirely separate chip running its own OS with its own RAM and IO, you could work with secrets, but traditional secure chips have so far been far from a silver bullet. I think the Intel Management Engine is close enough to the system CPU that it is probably affected by side channel attacks, but perhaps AMD's PSP is removed far enough to nullify the effect.

mike_hearn 4y ago
SGX was patched to solve those issues though. This is one of the issues with the security and side channels space: often there are mitigations powerful enough to stop attacks, but people don't remember them being rolled out. They recall the attack, say "oh well that is broken forever" and never re-visit the issue. As I mention elsewhere, an enclave is a good construct to use here because you're explicitly signalling to the CPU that the memory space has unusually sensitive secrets and you're willing to lose performance to protect them.
- jeroenhd 4y ago
  That's true, but the point is that simply relying on security extensions is no guarantee for safety. If it was broken before, the theoretical separation isn't complete enough to guarantee it won't be broken again. SGX is already being phased out by Intel for consumer/workstation products so I think they've given up on the concept themselves. I don't think they're supporting an alternative on consumer products either. Even if their server/enterprise implementation is secure enough, it won't protect against developers having their SSH keys exfiltrated by a game running in their browser during their downtime. I think externalising the security mechanism is a good idea, but the current implementations simply aren't good enough to combat this issue.
  - mike_hearn 4y ago