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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 May 25
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      Replying to @halvarflake @dEnergy_dTime and

      It doesn't matter - you *have* trusted binaries, you were going to build them anyway. Codesigning is only relevant for people who don't have trusted binaries, but do have a vendor they trust, right?

      1 reply 0 retweets 2 likes
    2. halvarflake‏ @halvarflake May 25
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      Replying to @taviso @dEnergy_dTime and

      I am not sure you are engaging with my argument. To repeat: I like deterministic builds because they may surface use of compromised signing keys. I don't think you get to decide that I should not care because I can build my own (trusted) binaries.

      1 reply 1 retweet 14 likes
    3. Tavis Ormandy‏Verified account @taviso May 25
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      Replying to @halvarflake @dEnergy_dTime and

      We agree that you can check if a build server is compromised or not with reproducible builds. I'm not saying you can't enjoy doing that if you like, but I am saying there's no security benefit over just open source.

      4 replies 0 retweets 1 like
    4. mik‏ @mik235 May 25
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      Replying to @taviso @halvarflake and

      Reproducible builds help glue together software supply chain security - eg. how do you know which versions of dependencies are included, was it built from a two-party approved commit, etc.

      1 reply 0 retweets 2 likes
    5. Tavis Ormandy‏Verified account @taviso May 25
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      Replying to @mik235 @halvarflake and

      Easy: You already have to build the software yourself in order to verify it reproduces, so then you use that build. Then it doesn't matter if they're bit-for-bit identical or not.

      2 replies 0 retweets 1 like
    6. Todor Genov‏ @tgenov May 25
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      Replying to @taviso @mik235 and

      You are assuming that I have an in-house build/package/deploy system. Google does. Most places don't. There's a fleet size N (N > 1, N < ???) where I don't want to compile MySQL from source on every host.

      1 reply 0 retweets 1 like
    7. Tavis Ormandy‏Verified account @taviso May 25
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      Replying to @tgenov @mik235 and

      Then how are you going to verify the build reproduces?

      1 reply 0 retweets 0 likes
    8. Todor Genov‏ @tgenov May 25
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      Replying to @taviso @mik235 and

      I'll verify it on 1 host. Verify the binary checksum. Use the binary on the other 100.

      1 reply 0 retweets 1 like
    9. Tavis Ormandy‏Verified account @taviso May 25
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      Replying to @tgenov @mik235 and

      You said you don't "have an in-house build". So I guess you do now, then why can't you distribute that build? That doesn't require reproducible builds, and has the same security benefits.

      2 replies 0 retweets 1 like
    10. mik‏ @mik235 May 25
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      Replying to @taviso @tgenov and

      how do you know the in house build server is ok?

      1 reply 0 retweets 1 like
      Tavis Ormandy‏Verified account @taviso May 25
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      Replying to @mik235 @tgenov and

      how do you know anything isn't compromised? Are we going to discuss "reflections on trusting trust", or are we going to talk about reproducible builds?

      2:57 PM - 25 May 2020
      • 3 Likes
      • Matt Denton Yanai Moyal
      2 replies 0 retweets 3 likes
        1. New conversation
        2. Jannis Harder‏ @jix_ May 25
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          Replying to @taviso

          I'd actually be interested if you're also disagreeing with David A. Wheelers thesis on countering trusting trust (especially sec. 4.6, 6, 8.8 & 8.9), which makes use of reproducible builds: https://dwheeler.com/trusting-trust/  It also considers compromise of build env other than the compiler.

          1 reply 0 retweets 0 likes
        3. Tavis Ormandy‏Verified account @taviso May 25
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          Replying to @jix_

          The only claim i'm disagreeing with is that build reproducibility prevents backdoors. People are claiming that it can detect tainted output from *trusted* but compromised build infra, and they're correct. I'm saying that you can already do that today.

          2 replies 0 retweets 1 like
        4. 7 more replies
        1. mik‏ @mik235 May 25
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          Replying to @taviso

          You've done plenty of IR, surely you've had to ask "where did this binary come from?" in many different ways. Software supply chain is a little complex to discuss here, but I really recommend catching up with the folks on the EIP team that work on this.

          0 replies 0 retweets 1 like
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