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It makes sense for server security as discussed by the same source as the op https://www.servethehome.com/amd-psb-vendor-locks-epyc-cpus-for-enhanced-security-a

It makes sense for server security as discussed by the same source as the op https://www.servethehome.com/amd-psb-vendor-locks-epyc-cpus-for-enhanced-security-at-a-cost/ https://www.servethehome.com/amd-psb-vendor-locks-epyc-cpus-...

captainmuon 5y ago
That link doesn't explain how it improves security, as all mainboards of the vendor have the same key. All it does is prevent somebody from sneakily replacing the mainboard with a different brand! It would make more sense if the board was bound to the specific CPU (assuming the CPU is the root of trust). But then you could just encase it in some kind of thermal epoxy... It's obvious that this is supposed to limit the second hand server parts market.
- YXNjaGVyZWdlbgo 5y ago
  If you read the two pages and you concluded that both AMD with their statement on Page 1 nor servethehome on Page 1 and Page 2 provided any information about how PSB works I can't help you.
  - monocasa 5y ago
    Or that commenter read and understood the description of how it works, and failed to see how it increases security in a meaningful way. I also struggle to think of a threat model that this protects against.
    - YXNjaGVyZWdlbgo 5y ago
      If something is not on your level of expertise you can always have a look for people that have the required level. It's just one search away. https://blog.cloudflare.com/anchoring-trust-a-hardware-secure-boot-story/ https://blog.cloudflare.com/anchoring-trust-a-hardware-secur...
      - monocasa 5y ago
        I'm a security researcher. PSB as described there is orthogonal to the specific policy of tying the board to a specific CPU key, as you can tell from per CPU keys not being in the hardware root of trust as described by cloudflare. In fact you can swap the CPUs across boards from different ODMs in your most recent citation, since the root is an AMD key that then verifies the off chip ODM cert in flash. I stand by my orignal statements.
        YXNjaGVyZWdlbgo 5y ago
        If you really think PSB doesn't provide any security benefit or "improves security in a meaningful way" you should do more security research.
        monocasa 5y ago
        I was pretty sure that I made it clear that the concept under discussion was using a hardware root of trust scheme like PSB to tie a specific CPU to a particular vendor's boards. As an aside I'm putting a lot of effort into staying civil; I'd appreciate seeing that effort be a bit more reciprocal.
        YXNjaGVyZWdlbgo 5y ago
        PSB is there to protect you from a compromised motherboard it protects you from malware in your UEFI firmware. It's not even a vendor lock in it's signing key lock in that is used in that manner by AWS, Gcloud and Azure. Compromised UEFI Firmware is a constant point of failure in pentesting of the secure chain of trust. That you as a security researcher are dismissing the fact is honestly just unbelievable.
        monocasa 5y ago
        > It's not even a vendor lock in it's signing key lock in that is used in that manner by AWS, Gcloud and Azure. Which is not the mechanism under discussion.

captainmuon 5y ago

That link doesn't explain how it improves security, as all mainboards of the vendor have the same key. All it does is prevent somebody from sneakily replacing the mainboard with a different brand! It would make more sense if the board was bound to the specific CPU (assuming the CPU is the root of trust). But then you could just encase it in some kind of thermal epoxy... It's obvious that this is supposed to limit the second hand server parts market.

YXNjaGVyZWdlbgo 5y ago
If you read the two pages and you concluded that both AMD with their statement on Page 1 nor servethehome on Page 1 and Page 2 provided any information about how PSB works I can't help you.
- monocasa 5y ago
  Or that commenter read and understood the description of how it works, and failed to see how it increases security in a meaningful way. I also struggle to think of a threat model that this protects against.
  - YXNjaGVyZWdlbgo 5y ago
    If something is not on your level of expertise you can always have a look for people that have the required level. It's just one search away. https://blog.cloudflare.com/anchoring-trust-a-hardware-secure-boot-story/ https://blog.cloudflare.com/anchoring-trust-a-hardware-secur...
    - monocasa 5y ago
      I'm a security researcher. PSB as described there is orthogonal to the specific policy of tying the board to a specific CPU key, as you can tell from per CPU keys not being in the hardware root of trust as described by cloudflare. In fact you can swap the CPUs across boards from different ODMs in your most recent citation, since the root is an AMD key that then verifies the off chip ODM cert in flash. I stand by my orignal statements.
      - YXNjaGVyZWdlbgo 5y ago
        If you really think PSB doesn't provide any security benefit or "improves security in a meaningful way" you should do more security research.
        monocasa 5y ago
        I was pretty sure that I made it clear that the concept under discussion was using a hardware root of trust scheme like PSB to tie a specific CPU to a particular vendor's boards. As an aside I'm putting a lot of effort into staying civil; I'd appreciate seeing that effort be a bit more reciprocal.
        YXNjaGVyZWdlbgo 5y ago
        PSB is there to protect you from a compromised motherboard it protects you from malware in your UEFI firmware. It's not even a vendor lock in it's signing key lock in that is used in that manner by AWS, Gcloud and Azure. Compromised UEFI Firmware is a constant point of failure in pentesting of the secure chain of trust. That you as a security researcher are dismissing the fact is honestly just unbelievable.
        monocasa 5y ago
        > It's not even a vendor lock in it's signing key lock in that is used in that manner by AWS, Gcloud and Azure. Which is not the mechanism under discussion.