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RichFelker's profile
Rich Felker
Rich Felker
Rich Felker
@RichFelker

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Rich Felker

@RichFelker

Yeah, I do @musllibc, FOSS & infosec stuff. But now is not the time for a mostly-/only-tech Twitter feed.

musl-libc.org
Joined March 2014

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    1. Rich Felker‏ @RichFelker Apr 12
      Replying to @chadloder @CopperheadOS @matthew_d_green

      There's no reason the data lines couldn't be electronically gated to a dumb charging controller chip while locked. Would eliminate non-invasive physical attacks.

      2 replies 0 retweets 1 like
    2. Chad Loder  ❇️‏ @chadloder Apr 12
      Replying to @RichFelker @CopperheadOS @matthew_d_green

      I’ve seen USB driver code at both the OS and micro-controller level - it’s not pretty. You’d be surprised how many special cases are required just to negotiate charging.

      1 reply 5 retweets 21 likes
    3. Rich Felker‏ @RichFelker Apr 12
      Replying to @chadloder @CopperheadOS @matthew_d_green

      Yes but that logic has no need to interact with OS or security processor logic. Can be completely isolated.

      1 reply 0 retweets 1 like
    4. Chad Loder  ❇️‏ @chadloder Apr 12
      Replying to @RichFelker @CopperheadOS @matthew_d_green

      That would be interesting, and it would also be something not called USB.

      2 replies 0 retweets 1 like
    5. Rich Felker‏ @RichFelker Apr 12
      Replying to @chadloder @CopperheadOS @matthew_d_green

      Sure it's USB (or rather USB over lightning). It's just 2+ separate logical USB devices, and which is connected is gated by lock state of the phone.

      1 reply 0 retweets 0 likes
    6. Chad Loder  ❇️‏ @chadloder Apr 12
      Replying to @RichFelker @CopperheadOS @matthew_d_green

      This starts to become a highly specialized phone that is useless when locked. Might as well turn off bluetooth, wifi, and push notifications while locked. How is this isolated set of chips going to know when the phone is unlocked? Who is going to signal it?

      1 reply 0 retweets 2 likes
    7. Rich Felker‏ @RichFelker Apr 12
      Replying to @chadloder @CopperheadOS @matthew_d_green

      Software can switch it all when entering locked state. I've actually never used my phone's USB port for anything but charging & initial OS install so it hardly seems "useless" to me.

      2 replies 0 retweets 0 likes
    8. Chad Loder  ❇️‏ @chadloder Apr 12
      Replying to @RichFelker @CopperheadOS @matthew_d_green

      You’re mixed up. You’d introduce a hardware isolation gate to protect the OS from port access while phone is locked, but the signal controlling the gate (“user unlocks phone with PIN”) has to come from the OS side of the boundary. How does that help?

      1 reply 0 retweets 0 likes
    9. Rich Felker‏ @RichFelker Apr 12
      Replying to @chadloder

      Not going to continue responding with your condescension.

      1 reply 0 retweets 0 likes
    10. Chad Loder  ❇️‏ @chadloder Apr 12
      Replying to @RichFelker

      I’m sorry - I didn’t mean to be condescending.

      1 reply 0 retweets 0 likes
      Rich Felker‏ @RichFelker Apr 12
      Replying to @chadloder

      Apology accepted. Idea above is that you can (modulo very different classes of attack) assume the OS is uncompressed as long as the interface surface to it is mostly or entirely cut off.

      9:09 PM - 12 Apr 2018
      2 replies 0 retweets 0 likes
        1. New conversation
        2. Chad Loder  ❇️‏ @chadloder Apr 12
          Replying to @RichFelker

          The interface meaning the message passing system between OS and hardware DMZ? Or between OS and user?

          1 reply 0 retweets 0 likes
        3. Rich Felker‏ @RichFelker Apr 12
          Replying to @chadloder

          Between OS and attacker. Interesting case is when phone is already locked & has (hypothetically) disabled data on the port.

          1 reply 0 retweets 0 likes
        4. Chad Loder  ❇️‏ @chadloder Apr 12
          Replying to @RichFelker

          The thing is, the OS has to do all kinds of stuff when locked: LTE, wifi, bluetooth, GPS, reminders, push notifications, polling for email/calendar invites. I think the idea of a meaningful boundary is impractical.

          1 reply 0 retweets 0 likes
        5. Rich Felker‏ @RichFelker Apr 12
          Replying to @chadloder

          Yes, but those have not been historic sources of OS-compromising remote vulnerabilities on iOS, have they?

          1 reply 0 retweets 0 likes
        6. Chad Loder  ❇️‏ @chadloder Apr 12
          Replying to @RichFelker

          Oh god yes they have. The NSA had a couple nice ones.

          0 replies 0 retweets 0 likes
        7. End of conversation
        1. Rich Felker‏ @RichFelker Apr 12
          Replying to @RichFelker @chadloder

          Lightning port is by far the biggest attack surface while the phone is locked without physically opening or damaging the phone.

          0 replies 0 retweets 0 likes
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