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tehjh's profile
Jann Horn
Jann Horn
Jann Horn
@tehjh

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Jann Horn

@tehjh

works at Google Project Zero. personal account.

Joined August 2011

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    1. Jann Horn‏ @tehjh 3 Nov 2017
      • Report Tweet
      • Report NetzDG Violation
      Replying to @tehjh @ewindisch @SwiftOnSecurity

      just look at the commit you linked. they have a big blacklist of known ways to bypass their protections, and they missed one file.

      2 replies 0 retweets 0 likes
    2. Jann Horn‏ @tehjh 3 Nov 2017
      • Report Tweet
      • Report NetzDG Violation
      Replying to @tehjh @ewindisch @SwiftOnSecurity

      the kernel has an API for giving containers fake root, and that is user namespaces. and if you don't want to use that, at least whitelist.

      2 replies 0 retweets 1 like
    3. Erica Windisch‏ @ewindisch 3 Nov 2017
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      Replying to @tehjh @SwiftOnSecurity

      The sysctl are an exception, yes, but many other files in proc that check CAP_SYS_ADMIN.

      1 reply 0 retweets 1 like
    4. Jann Horn‏ @tehjh 3 Nov 2017
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      Replying to @ewindisch @SwiftOnSecurity

      you could argue that these checks are inconsistent; but OTOH, there are users who actually want to be able to chown files in /proc

      1 reply 0 retweets 0 likes
    5. Jann Horn‏ @tehjh 3 Nov 2017
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      Replying to @tehjh @ewindisch @SwiftOnSecurity

      for example, Android chowns /proc/sysrq-trigger to root:system so that system_server can use it (or at least Android used to do that)

      1 reply 0 retweets 0 likes
    6. Jann Horn‏ @tehjh 3 Nov 2017
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      Replying to @tehjh @ewindisch @SwiftOnSecurity

      if you did a capability check in sysrq-trigger, the kernel API would lose this flexibility

      2 replies 0 retweets 0 likes
    7. Erica Windisch‏ @ewindisch 3 Nov 2017
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      Replying to @tehjh @SwiftOnSecurity

      Yes, users in Docker can also chmod most files in proc currently, too :(

      1 reply 0 retweets 1 like
    8. Jann Horn‏ @tehjh 3 Nov 2017
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      Replying to @ewindisch @SwiftOnSecurity

      my point is that not having capability checks on files on procfs (unless those files directly lead to root-equivalent access) is useful

      1 reply 0 retweets 0 likes
    9. Erica Windisch‏ @ewindisch 3 Nov 2017
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      Replying to @tehjh @SwiftOnSecurity

      This specific proc file makes sense to have a CAP_SYS_ADMIN restriction IMHO; however, I don't really care anymore. 🤷🏼‍♀️

      1 reply 0 retweets 1 like
    10. Aaron Grattafiori‏ @dyn___ 3 Nov 2017
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      Replying to @ewindisch @tehjh @SwiftOnSecurity

      The capability model was such an after thought, plus no procfs namespace. It's a mess. I want a new microkernel for TCB bootstrap limux ABI.

      2 replies 0 retweets 0 likes
      Jann Horn‏ @tehjh 3 Nov 2017
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      Replying to @dyn___ @ewindisch @SwiftOnSecurity

      I think microkernels are called "hypervisors" nowadays :P

      10:09 PM - 3 Nov 2017
      • 11 Retweets
      • 19 Likes
      • Sophisticated Chameleon Markus Wennrich Topper Bowers Artem Shishkin Grandmaster Clock 😷 🇪🇺 isis agora lovecruft (they/them) jakob Joanna Rutkowska datenwolf - flausching the curve
      2 replies 11 retweets 19 likes
        1. New conversation
        2. Aaron Grattafiori‏ @dyn___ 3 Nov 2017
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          Replying to @tehjh @ewindisch @SwiftOnSecurity

          Well, yes. Clear Linux and all that... Still so rarely used outside of maybe that psycho @jessfraz 's desktop and Qubes. The model is solid.

          1 reply 0 retweets 1 like
        3. Aaron Grattafiori‏ @dyn___ 3 Nov 2017
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          Replying to @dyn___ @tehjh and

          ARM hypervisors are still rare too :(.... At least the gaming industry gets it ;)

          0 replies 0 retweets 0 likes
        4. End of conversation
        1. Stefan Jon Silverman‏ @sjs_sf 4 Nov 2017
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          Replying to @tehjh @rootkovska and

          there are subtle differences in how the stacks on top are put together after booting on bare iron but point taken...

          0 replies 0 retweets 0 likes
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