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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 @CopperheadOS @matthew_d_green @chadloder

      Seems doubtful that they have more than one that works without even taking apart the phone. This one is really bad and Apple should be able to figure it out without seeing it...

      2 replies 0 retweets 4 likes
    2. Rich Felker‏ @RichFelker Apr 12
      Replying to @RichFelker @CopperheadOS and

      Of course they likely know they have an utterly wrong hardware topology in that the lightning port has any kind of access to the locked-down chips, but that's probably not easy for them to fix...

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

      It probably doesn't have direct access. They could be exploiting the OS and then escalating to SEP access with another exploit. It's impossible to know exactly what they're doing. SEP provides a lot more than the disk encryption hardware support so there's other attack surface.

      2 replies 0 retweets 4 likes
    4. Rich Felker‏ @RichFelker Apr 12
      Replying to @CopperheadOS @matthew_d_green @chadloder

      Seems like the port shouldn't even be active for data (charging only) when the phone is locked. Anyone wanna bet they enabled it for headphones since they removed the headphone jack? ;-)

      2 replies 0 retweets 3 likes
    5. CopperheadOS‏ @CopperheadOS Apr 12
      Replying to @RichFelker @matthew_d_green @chadloder

      It definitely supports more than charging in that case, as do Android phones. The move to Lightning / USB C headphones does genuinely make it less convenient to do something like https://github.com/CopperheadOS/platform_frameworks_base/commit/7b811853c5d2b05ec5db11786ab3f4b6a079e1a1 … but there are a lot of other reasons for them using data at that point.

      1 reply 0 retweets 2 likes
    6. CopperheadOS‏ @CopperheadOS Apr 12
      Replying to @CopperheadOS @RichFelker and

      One simple example is supporting USB keyboards and various accessibility technology. Some of that may be needed by someone to unlock the screen. Accessibility support often ends up being a security problem, not familiar with how accessibility services work on iOS though.

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

      Seems they could/should only support Bluetooth, and only devices that are already paired when unlocked. Lightning is a much much bigger attack surface.

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

      This logic requires code to execute, and that is likely where the flaw lives.

      1 reply 0 retweets 0 likes
    9. 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
    10. 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
      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.

      5:07 PM - 12 Apr 2018
      • 1 Like
      • Matthew Green
      1 reply 0 retweets 1 like
        1. New conversation
        2. 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
        3. 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
        4. 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
        5. 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
        6. 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
        7. Rich Felker‏ @RichFelker Apr 12
          Replying to @chadloder

          Not going to continue responding with your condescension.

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

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

          1 reply 0 retweets 0 likes
        9. 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.

          2 replies 0 retweets 0 likes
        10. 5 more replies

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