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Reversing the AMD Secure Processor (PSP) – Part 2: Cryptographic Co-Processor

112 points by vngzs 2y ago

dtx1 2y ago
I never understood why AMD is not at least making the source of these available. I would actually really like a secure cryptographic processor that's been extensively vetted and trustworthy.
- DaSHacka 2y ago
  The common assumption is that their hands are tied on that matter.
  - transpute 2y ago
    Like OpenSIL, AMD could start a long-term project to replace the closed ASP with an open alternative. The industry now has Calpitra (AMD contributes), OpenTitan, TockOS (used by Pluton) and other open hardware and software projects for security enclaves.
- rajeshr 2y ago
  They did publish the source: https://github.com/amd/AMD-ASPFW https://github.com/amd/AMD-ASPFW This was the PR(!): https://ir.amd.com/news-events/press-releases/detail/1154/amd-shares-the-technical-details-of-technology-powering https://ir.amd.com/news-events/press-releases/detail/1154/am... I wonder if the reported exploits forced them to publish the source.
  - shrubble 2y ago
    That is only the part that allows encrypted virtual machines on EPYC cpus. The PSP in some form is on all AMD processors since about 2013/2014.
    - tonetegeatinst 2y ago
      Encrypted vm's? On epyc? What's the performance penalty for that?
      - toast0 2y ago
        I don't know the performance implications, but the brief description of the feature is that guest memory is encrypted with a key that the host doesn't know, so the host can't observe the contents of guest memory.
      - bobbiechen 2y ago
        In benchmarks from Microsoft Azure and Google Cloud, 1-8% overhead for throughput. Microsoft Azure: https://community.amd.com/t5/epyc-processors/microsoft-azure-confidential-computing-powered-by-3rd-gen-epyc/ba-p/497796 https://community.amd.com/t5/epyc-processors/microsoft-azure... Google Cloud: https://www.amd.com/content/dam/amd/en/documents/epyc-business-docs/performance-briefs/confidential-computing-performance-sev-snp-google-n2d-instances.pdf https://www.amd.com/content/dam/amd/en/documents/epyc-busine...
      - strstr 2y ago
        For CPU bound work loads, pretty low, but not low enough that it's free (~5%). For devices (especially latency sensitive workloads), it's quite bad. Device accesses have to be bounce-buffered. You can't do anything vaguely zero copy, since the device can't DMA to or from the VM. Future hardware support will mitigate that (mutually attested VM/Device interactions), but no real world devices support it yet.
- shrubble 2y ago
  Many believe it was not added as a result of customer requirements, but that the government leaned on them to add it as a tool of surveillance.
- gchadwick 2y ago
  That's exactly what we're doing with OpenTitan: https://opentitan.org/ https://opentitan.org/ Which Google will be using in Chromebook for it's security chip https://lowrisc.org/news/nuvoton-develops-opentitan-based-security-chip-as-next-gen-security-solution-for-chromebooks/ https://lowrisc.org/news/nuvoton-develops-opentitan-based-se...
  - arresin 2y ago
    Very cool. Bookmarked.
- password4321 2y ago
  "AMD Confirms It Won't Opensource EPYC's Platform Security Processor Code" https://hothardware.com/news/amd-confirms-it-will-not-be-opensourcing-epycs-platform-security-processor-code https://hothardware.com/news/amd-confirms-it-will-not-be-ope... (2017) > Dr. Lisa Su gave some hope that something would be done when she said she'd discuss things internally as the result of a recent reddit AMA question. Ultimately, though, it turns out that AMD is not opening up the PSP https://www.twitch.tv/videos/160097335?t=00h35m35s https://www.twitch.tv/videos/160097335?t=00h35m35s
mrweasel 2y ago
How popular is AMDs PSP, or Intels IME for that matter, in the real world. I've never seen either used at all.
- transpute 2y ago
  In addition to system launch integrity, they are likely used by streaming video DRM, e.g. Netflix.
  - mrweasel 2y ago
    Ah, I always understood them to be mostly for remote management.
    - iforgotpassword 2y ago
      That's AMT/vPro in Intels case. Gives you things like vnc access from the moment the machine turns on.
  - compsciphd 2y ago
    SGX was used by video DRM on intel platforms. As SGX no longer exists in modern intel processors, its not really doable anymore. netflix drm and the like are probably done on gpu, not on cpu (but I could be wrong) It's actually impossible to have a "legal"/commercial 4k bluray setup today on modern PCs/CPUs, as they will only license it to players that can use SGX and as noted SGX no longer exists. (of course this doesn't prevent one from using vlc / libaacs and the like).
    - jrpelkonen 2y ago
      I believe Xeons still include SGX even today. You’re correct about the consumer CPUs not supporting it anymore.
      - Teever 2y ago
        Any idea why Xeons would still contain this feature? Is it for backwards compatibility for their corporate customers or are there reasons that someone would still use it in modern applications in 2024?
eqvinox 2y ago
(genuine question, sorry -) is it just me or does anyone else have problems reading the text with the font the webpage uses? It kinda blurs away from "text" into kind of a grey block. I think it might be the very small vertical line to line spacing?
- zote 2y ago
  It's the contrast!, all the code blocks do not meet the WCAG standards for accessible text, especially the second one, which as the hardest one for me to read.
- kdbg 2y ago
  Author of the site here (though not this specific post). Any chance you could take a screenshot of what your seeing? The other commenter mentioned the contract of comment s in code blocks which I've already noted to fix.
  - eqvinox 2y ago
    > Any chance you could take a screenshot of what your seeing? I don't think it's a rendering issue, but sure: https://postimg.cc/ygsNzMhX https://postimg.cc/ygsNzMhX I looked into the CSS and removing the "line-height:1.15" makes it massively more readable for me personally. I have no idea about any science of human perception but I think the font is too "dense" with that reduced line spacing. (It's hard to self-observe this but I believe my eyes are slipping off between lines. Character width might be a factor too.) (To clarify, my issue is with the main text itself, not code blocks.)

112 points by vngzs 2y ago

dtx1 2y ago

I never understood why AMD is not at least making the source of these available. I would actually really like a secure cryptographic processor that's been extensively vetted and trustworthy.

DaSHacka 2y ago
The common assumption is that their hands are tied on that matter.
- transpute 2y ago
  Like OpenSIL, AMD could start a long-term project to replace the closed ASP with an open alternative. The industry now has Calpitra (AMD contributes), OpenTitan, TockOS (used by Pluton) and other open hardware and software projects for security enclaves.
rajeshr 2y ago
They did publish the source: https://github.com/amd/AMD-ASPFW https://github.com/amd/AMD-ASPFW This was the PR(!): https://ir.amd.com/news-events/press-releases/detail/1154/amd-shares-the-technical-details-of-technology-powering https://ir.amd.com/news-events/press-releases/detail/1154/am... I wonder if the reported exploits forced them to publish the source.
- shrubble 2y ago
  That is only the part that allows encrypted virtual machines on EPYC cpus. The PSP in some form is on all AMD processors since about 2013/2014.
  - tonetegeatinst 2y ago
    Encrypted vm's? On epyc? What's the performance penalty for that?
    - toast0 2y ago
      I don't know the performance implications, but the brief description of the feature is that guest memory is encrypted with a key that the host doesn't know, so the host can't observe the contents of guest memory.
    - bobbiechen 2y ago
      In benchmarks from Microsoft Azure and Google Cloud, 1-8% overhead for throughput. Microsoft Azure: https://community.amd.com/t5/epyc-processors/microsoft-azure-confidential-computing-powered-by-3rd-gen-epyc/ba-p/497796 https://community.amd.com/t5/epyc-processors/microsoft-azure... Google Cloud: https://www.amd.com/content/dam/amd/en/documents/epyc-business-docs/performance-briefs/confidential-computing-performance-sev-snp-google-n2d-instances.pdf https://www.amd.com/content/dam/amd/en/documents/epyc-busine...
    - strstr 2y ago
      For CPU bound work loads, pretty low, but not low enough that it's free (~5%). For devices (especially latency sensitive workloads), it's quite bad. Device accesses have to be bounce-buffered. You can't do anything vaguely zero copy, since the device can't DMA to or from the VM. Future hardware support will mitigate that (mutually attested VM/Device interactions), but no real world devices support it yet.
shrubble 2y ago
Many believe it was not added as a result of customer requirements, but that the government leaned on them to add it as a tool of surveillance.
gchadwick 2y ago
That's exactly what we're doing with OpenTitan: https://opentitan.org/ https://opentitan.org/ Which Google will be using in Chromebook for it's security chip https://lowrisc.org/news/nuvoton-develops-opentitan-based-security-chip-as-next-gen-security-solution-for-chromebooks/ https://lowrisc.org/news/nuvoton-develops-opentitan-based-se...
- arresin 2y ago
  Very cool. Bookmarked.
password4321 2y ago
"AMD Confirms It Won't Opensource EPYC's Platform Security Processor Code" https://hothardware.com/news/amd-confirms-it-will-not-be-opensourcing-epycs-platform-security-processor-code https://hothardware.com/news/amd-confirms-it-will-not-be-ope... (2017) > Dr. Lisa Su gave some hope that something would be done when she said she'd discuss things internally as the result of a recent reddit AMA question. Ultimately, though, it turns out that AMD is not opening up the PSP https://www.twitch.tv/videos/160097335?t=00h35m35s https://www.twitch.tv/videos/160097335?t=00h35m35s

mrweasel 2y ago

How popular is AMDs PSP, or Intels IME for that matter, in the real world. I've never seen either used at all.

transpute 2y ago
In addition to system launch integrity, they are likely used by streaming video DRM, e.g. Netflix.
- mrweasel 2y ago
  Ah, I always understood them to be mostly for remote management.
  - iforgotpassword 2y ago
    That's AMT/vPro in Intels case. Gives you things like vnc access from the moment the machine turns on.
- compsciphd 2y ago
  SGX was used by video DRM on intel platforms. As SGX no longer exists in modern intel processors, its not really doable anymore. netflix drm and the like are probably done on gpu, not on cpu (but I could be wrong) It's actually impossible to have a "legal"/commercial 4k bluray setup today on modern PCs/CPUs, as they will only license it to players that can use SGX and as noted SGX no longer exists. (of course this doesn't prevent one from using vlc / libaacs and the like).
  - jrpelkonen 2y ago
    I believe Xeons still include SGX even today. You’re correct about the consumer CPUs not supporting it anymore.
    - Teever 2y ago
      Any idea why Xeons would still contain this feature? Is it for backwards compatibility for their corporate customers or are there reasons that someone would still use it in modern applications in 2024?

eqvinox 2y ago

(genuine question, sorry -) is it just me or does anyone else have problems reading the text with the font the webpage uses? It kinda blurs away from "text" into kind of a grey block. I think it might be the very small vertical line to line spacing?

zote 2y ago
It's the contrast!, all the code blocks do not meet the WCAG standards for accessible text, especially the second one, which as the hardest one for me to read.
kdbg 2y ago
Author of the site here (though not this specific post). Any chance you could take a screenshot of what your seeing? The other commenter mentioned the contract of comment s in code blocks which I've already noted to fix.
- eqvinox 2y ago
  > Any chance you could take a screenshot of what your seeing? I don't think it's a rendering issue, but sure: https://postimg.cc/ygsNzMhX https://postimg.cc/ygsNzMhX I looked into the CSS and removing the "line-height:1.15" makes it massively more readable for me personally. I have no idea about any science of human perception but I think the font is too "dense" with that reduced line spacing. (It's hard to self-observe this but I believe my eyes are slipping off between lines. Character width might be a factor too.) (To clarify, my issue is with the main text itself, not code blocks.)