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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. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      the catch here is: doing the load puts that data in the cache. so... imagine you're not supposed to be able to know "b" because it's in kernel memory. it'll load b, and then load z[b] to get c. then at some point it will fail and roll back.

      2 replies 17 retweets 147 likes
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    2. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      but this will have a side effect: the chunk of memory containing "c" will end up getting loaded into cache. the rollback *isn't total*. it's like the CPU went ahead to the next page of an assignment before it was supposed to, but didn't completely hide that fact.

      8 replies 24 retweets 197 likes
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    3. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      and given the right circumstances, you can use this to recover "b", one bit at a time.

      4 replies 15 retweets 134 likes
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    4. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      you can now recover arbitrary data from any memory in the system. you win.

      2 replies 22 retweets 187 likes
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    5. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      (there's other variants that use branch prediction, etc to apply the approximate same attack. but the core idea is the same: construct a case where the CPU leaves a visible trail of its speculative execution)

      1 reply 9 retweets 129 likes
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    6. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      someone who read more of the article than me tell me if i'm wrong tho

      10 replies 2 retweets 84 likes
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    7. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      oh, and one last thing: the thing that gets me most about this exploit is it isn't really a single exploit, it's a whole *category* of exploits. verifying that no further attacks exist sounds EXTREMELY hard.

      2 replies 90 retweets 380 likes
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    8. Fiora @ mandatory homestuck!‏ @FioraAeterna 3 Jan 2018
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      i kinda get why they had to use such a big software hammer on this: i'd be reaaallllyyy nervous about some clever trick solution purporting to patch up an infinity of tiny holes

      3 replies 12 retweets 166 likes
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    9. czub / ズー‏ @mczub 3 Jan 2018
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      Replying to @FioraAeterna

      what i really like is that 'oh yeah we broke the fuck out of KASLR' is just a footnote in one of the papers

      2 replies 11 retweets 86 likes
    10. czub / ズー‏ @mczub 3 Jan 2018
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      Replying to @mczub @FioraAeterna

      also 'oh yeah we reverse engineered all of haswell's branch predictor, no biggie'

      3 replies 35 retweets 187 likes
      Jann Horn‏ @tehjh 3 Jan 2018
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      Replying to @mczub @FioraAeterna

      not *all* of it

      4:23 PM - 3 Jan 2018
      • 6 Retweets
      • 80 Likes
      • Triglypton ashley Wil Lee 🏳️‍🌈 social distancer ˈɛmə ˈwɛlkəːr ck Meredith L. Patterson James Troup Jérémy Jaussaud
      1 reply 6 retweets 80 likes
        1. Amber Yust‏ @Aiiane 3 Jan 2018
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          Replying to @tehjh @mczub @FioraAeterna

          Humblebrag of the century (not that you don't deserve it)

          0 replies 1 retweet 17 likes
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