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taviso's profile
Tavis Ormandy
Tavis Ormandy
Tavis Ormandy
Verified account
@taviso

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Tavis OrmandyVerified account

@taviso

Vulnerability researcher at Google. This is a personal stream, opinions expressed are mine.

California
taviso.decsystem.org
Joined April 2008

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    1. Tavis Ormandy‏Verified account @taviso 24 Sep 2018
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      I finally wrote a small tool I've wanted for a long time: A parallel testcase minimizer. It's called halfempty, and I'm already finding it useful as part of my fuzzing workflow. /cc @lcamtuf https://github.com/googleprojectzero/halfempty …pic.twitter.com/qleqrRbTDy

      22 replies 433 retweets 1,296 likes
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    2. Tillery (they/them) in isolation‏ @AreTillery 24 Sep 2018
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      Replying to @taviso @lcamtuf

      Other than parallelization is your bisectional method significantly different than Delta Debugging?

      1 reply 0 retweets 0 likes
    3. Tavis Ormandy‏Verified account @taviso 24 Sep 2018
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      Replying to @AreTillery @tomastillery @lcamtuf

      No, parallelization is the main new contribution. I do have some ideas for other strategies though, but I guess we'll see how well they work when I finish writing them 🙂

      1 reply 0 retweets 3 likes
    4. Tillery (they/them) in isolation‏ @AreTillery 24 Sep 2018
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      Replying to @taviso @lcamtuf

      Do you have any thoughts regarding debugger instrumentation? One of the strengths of delta debugging over afl-tmin (and the reason we use it) is that you can write debugger-driventest funcs rather than a pass/fail on crash or exit code.

      1 reply 0 retweets 0 likes
    5. Tavis Ormandy‏Verified account @taviso 24 Sep 2018
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      Replying to @AreTillery @tomastillery @lcamtuf

      Hmm, do you have an example testfunc you use? In general, I automate gdb for things like that, which can be used with afl-tmin or halfempty.

      1 reply 0 retweets 0 likes
    6.  ☣Adam‏ @AdamOfDc949 24 Sep 2018
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      Replying to @taviso @tomastillery @lcamtuf

      Yeah we have a bunch of examples here: https://github.com/grimm-co/delta-debugging/tree/master/scripts … Specifically, in the first sqlite example we were interested in minimizing the input for find bug A, but removing bytes would sometimes trigger bug B (which was something lame, like a NPE).

      1 reply 1 retweet 8 likes
    7. Tavis Ormandy‏Verified account @taviso 24 Sep 2018
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      Replying to @AdamOfDc949 @tomastillery @lcamtuf

      I run into that problem as well, I have an example in the halfempty docs here: https://github.com/googleprojectzero/halfempty#verifying-crashes …. You could use your script with afl-tmin or halfempty too though, right?

      1 reply 0 retweets 1 like
    8.  ☣Adam‏ @AdamOfDc949 24 Sep 2018
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      Replying to @taviso @tomastillery @lcamtuf

      🤔 Are you suggesting running halfempty on a Python script which runs the target executable under gdb, analyzes the gdb output (registers, stacktraces, etc.) and then chooses a return code to signal whether it was the "correct" crash or not? Hmm, yeah, that should work.

      1 reply 0 retweets 1 like
    9.  ☣Adam‏ @AdamOfDc949 24 Sep 2018
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      Replying to @AdamOfDc949 @taviso and

      In my experience, afl-tmin gets inputs down to size faster than delta-debugging, and it has been the same file size in the end. On the other hand, delta-debugging works on things like end-to-end browser crashes, which AFL wasn't designed for GUI apps.

      1 reply 0 retweets 0 likes
    10.  ☣Adam‏ @AdamOfDc949 24 Sep 2018
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      Replying to @AdamOfDc949 @taviso and

      I'd be interested in seeing real-world metrics on how much faster halfempty is over delta-debugging and whether it achieves the same size file in the end. I'll eventually run some comparison tests myself, but I have many other higher priorities for the next few months.

      1 reply 0 retweets 0 likes
      Tavis Ormandy‏Verified account @taviso 24 Sep 2018
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      Replying to @AdamOfDc949 @tomastillery @lcamtuf

      Targets like browsers that take 10s of seconds to reproduce is exactly the use case I had in mind, halfempty will be significantly faster (maybe by hours). If the final output isn't as good, I would consider that a bug and fix it 🙂

      4:52 PM - 24 Sep 2018
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      • Rene Freingruber ☣Adam
      0 replies 0 retweets 2 likes

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