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kees_cook's profile
𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔
𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔
𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔
@kees_cook

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𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔

@kees_cook

Free Software Hacker

Portland, OR, USA
outflux.net/blog
Joined February 2010

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    1. 𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔‏ @kees_cook 14 Sep 2017

      𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔 Retweeted LinuxSecuritySummit

      Slides for the LSS 2017 update on KSPP: https://outflux.net/slides/2017/lss/kspp.pdf …https://twitter.com/LinuxSecSummit/status/908399454515994624 …

      𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔 added,

      LinuxSecuritySummit @LinuxSecSummit
      @kees_cook presenting an update on the Linux Kernel Self Protection Project at #LinuxSecuritySummit 2017 pic.twitter.com/JunFfoI9zU
      1 reply 31 retweets 27 likes
    2. Mathias Krause‏ @_minipli 20 Sep 2017
      Replying to @kees_cook

      Does the RLIMIT_STACK bug you're hinting at has any real-life relevance for @grsecurity kernels?

      1 reply 0 retweets 0 likes
    3. 𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔‏ @kees_cook 20 Sep 2017
      Replying to @_minipli

      I didn't try, but it should make Stack Clash easier to hit on old grsecurity since the memory layout becomes controllable again

      2 replies 0 retweets 0 likes
    4. Mathias Krause‏ @_minipli 20 Sep 2017
      Replying to @kees_cook

      Actually, what memory layout becomes controllable again?

      1 reply 0 retweets 0 likes
    5. 𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔‏ @kees_cook 20 Sep 2017
      Replying to @_minipli

      legacy bottom-up vs regular top-down mmap layout, see IV.1.1, IV.1.4, IV.1.5. IV.1.6 misses this, so the analysis is incomplete.

      1 reply 0 retweets 0 likes
    6. Mathias Krause‏ @_minipli 21 Sep 2017
      Replying to @kees_cook

      Well, IV.1.1-5 of the Qualys analysis covers the behaviour of *vanilla* Linux, not grsec. Don't mix that up!

      1 reply 1 retweet 0 likes
    7. Mathias Krause‏ @_minipli 21 Sep 2017
      Replying to @_minipli @kees_cook

      All of the described attacks require passing large argv[] + envp[] to the SUID binary. However, grsec limits them to 512kB.

      1 reply 0 retweets 0 likes
    8. Mathias Krause‏ @_minipli 21 Sep 2017
      Replying to @_minipli @kees_cook

      For the sudo vulnerability (allowing to work-around even this restriction) the advisory states an "exploitation [is] impossible".

      1 reply 0 retweets 0 likes
    9. Mathias Krause‏ @_minipli 21 Sep 2017
      Replying to @_minipli @kees_cook

      So even without the 8 MB RLIMIT_STACK restriction in place, grsec has other mechanisms making 'Stack Clash' kind of attacks infeasible:pic.twitter.com/GZA1uDElZI

      1 reply 1 retweet 0 likes
      𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔‏ @kees_cook 21 Sep 2017
      Replying to @_minipli

      my point was grsec's "8MB setuid stack limit" didn't work as intended; upstreaming those kinds of ideas requires time/effort.

      9:59 AM - 21 Sep 2017
      1 reply 0 retweets 0 likes
        1. New conversation
        2. Mathias Krause‏ @_minipli 21 Sep 2017
          Replying to @kees_cook

          Indeed it does! However, in grsec's case it doesn't/didn't matter much as other mechanisms ensure "defense in depth" still stands.

          1 reply 1 retweet 1 like
        3. 𝙺𝚎𝚎𝚜 𝙲𝚘𝚘𝚔‏ @kees_cook 21 Sep 2017
          Replying to @_minipli

          Yup, agreed. That's why I worked on getting it upstreamed (along with other accounting fixes/limits). Defense in depth FTW!

          0 replies 1 retweet 1 like
        4. End of conversation

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