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marcan42's profile
Hector Martin
Hector Martin
Hector Martin
@marcan42

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Hector Martin

@marcan42

If it ain't broke, I'll fix it! I'm porting Linux to Apple Silicon Macs at @AsahiLinux. http://patreon.com/marcan  | http://github.com/sponsors/marcan 

Tokyo, Japan
marcan.st
Joined May 2009

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    1. Hector Martin‏ @marcan42 9 Jun 2020
      • Report Tweet
      • Report NetzDG Violation

      Intel: "Hey, you know what would be a great idea? If we reused the same shared buffer for CPUID and RDRAND output, and shared it across all cores, and always loaded the whole thing, not just requested data." Their security incompetence truly knows no bounds.pic.twitter.com/nBtfGLEroj

      11 replies 129 retweets 368 likes
      Show this thread
    2. Andrew Wygle‏ @awygle 9 Jun 2020
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      Replying to @marcan42

      I mean this in all sincerity - why is this a problem?

      2 replies 0 retweets 3 likes
    3. Hector Martin‏ @marcan42 9 Jun 2020
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      Replying to @awygle

      Because now you're broadcasting extremely sensitive data (as in: all your private keys are belong to us) intended for one core to all cores. That breaks down the core isolation boundary, making the security as weak as hyperthread isolation. And we know that one is really weak.

      2 replies 2 retweets 37 likes
    4. Hector Martin‏ @marcan42 9 Jun 2020
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      Replying to @marcan42 @awygle

      It's been this story time and time and time again. Intel CPUs have *no* security boundaries in speculation. Their only security boundary is instruction retirement. They have zero compartmentalization or defense in depth. It's insane.

      1 reply 3 retweets 24 likes
    5. Hector Martin‏ @marcan42 9 Jun 2020
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      Replying to @marcan42 @awygle

      Like, this is the moral equivalent of running your web Javascript VM interpreter in kernel mode - no, better, inside the hypervisor outside the guest running Chrome, because surely it has no bugs and why would you ever need any other security layers or defense mechanisms?

      1 reply 0 retweets 24 likes
    6. Hector Martin‏ @marcan42 9 Jun 2020
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      Replying to @marcan42 @awygle

      This is how we got "let's read data from kernel address space in user mode, who cares", "let's interpret guest virtual addresses as physical addresses when they fault, who cares", "let's feed random leftover/uninitialized buffer data into registers, who cares", all in speculation

      1 reply 0 retweets 23 likes
    7. Hector Martin‏ @marcan42 9 Jun 2020
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      Replying to @marcan42 @awygle

      This is just the latest instance in "Intel CPUs are information soup, and enforce zero security or data privacy boundaries anywhere, until instruction retirement".

      2 replies 1 retweet 19 likes
    8. Andrew Wygle‏ @awygle 10 Jun 2020
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      Replying to @marcan42

      I get the pattern as a problem obviously. I don't understand why "rdrand and cpuid share a buffer" equals "all your keys are belong to us". Surely key generation is more than `rdrand rax`?

      1 reply 0 retweets 0 likes
      Hector Martin‏ @marcan42 10 Jun 2020
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      Replying to @awygle

      Nah, that's a perfectly valid way of generating keys. It's also a perfectly valid way of generating random nonces for ECDSA, which, if compromised, also reveal the private key (see: PS3)

      1:28 AM - 10 Jun 2020
      • 5 Likes
      • nota 🦈 Donald “chronos” King 🏳️‍🌈 Jon Roelofs Stephen Kraus - Hyperconverged Spicy Rocks🔑☢️⚛️ Jesse V. Burke
      2 replies 0 retweets 5 likes
        1. New conversation
        2. Andrew Wygle‏ @awygle 10 Jun 2020
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          Replying to @marcan42

          OK, I do see how that could be an issue. I will do my level best to care about this.

          1 reply 0 retweets 1 like
        3. Hector Martin‏ @marcan42 10 Jun 2020
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          Replying to @awygle

          I mean it just boils down to rdrand data should be private to the core that requests it, so sending it to other cores too is a bad idea (as proven here where people found a way to get at it). Doesn't really matter how bad the practical attack scenario is :)

          2 replies 0 retweets 5 likes
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