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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.  😷 Juliano Rizzo‏ @julianor May 23
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      Replying to @taviso @halvarflake and

      It must be automated IMO.

      1 reply 0 retweets 0 likes
    2. Tavis Ormandy‏Verified account @taviso May 23
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      Replying to @julianor @halvarflake and

      Maybe, but you *have* to trust the vendor anyway, and if you don't trust them to tell the truth that they're checking the build server, then you can't trust them not to insert bugdoors... right? 😛

      2 replies 0 retweets 0 likes
    3. Nathan Cook‏ @coolhandle01 May 23
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      Replying to @taviso @julianor and

      So are you advocating for all software companies to hack their build infra...?

      2 replies 0 retweets 0 likes
    4.  😷 Juliano Rizzo‏ @julianor May 23
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      Replying to @coolhandle01 @taviso and

      looks like I'm having some trouble understanding today. I think supply chain attacks are the most effective (i.e. hack the world) and reproducible builds + m of N signatures are a good defense tool.

      3 replies 0 retweets 3 likes
    5. Tavis Ormandy‏Verified account @taviso May 23
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      Replying to @julianor @coolhandle01 and

      I don't see how a supply chain attack is relevant. I think reproducible builds prove your build server isn't compromised and nothing else, it doesn't reduce the need to trust the vendor. As you already trust the vendor, what's wrong with codesigning or similar?

      3 replies 0 retweets 0 likes
    6. halvarflake‏ @halvarflake May 23
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      Replying to @taviso @julianor and

      Is there value in being able to state "this binary is derived from that source code"? I think yes, independently of whether I am the vendor or user. But I won't argue that repro builds solve backdoors.

      1 reply 1 retweet 5 likes
    7. halvarflake‏ @halvarflake May 23
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      Replying to @halvarflake @taviso and

      Fwiw it's a bit sad that repro builds even need discussing; imo deterministic repro builds should be about as exotic as a working "ls".

      2 replies 0 retweets 11 likes
    8. halvarflake‏ @halvarflake May 23
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      Replying to @halvarflake @taviso and

      They don't do anything except establish a clear checkable source-to-binary link; but that seems like such a fundamental thing?

      1 reply 0 retweets 6 likes
    9. Tavis Ormandy‏Verified account @taviso May 25
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      Replying to @halvarflake @julianor and

      Hmm, but why? You have the source code and a binary that someone you trust says is the output from compiling that code. You trust them, but think their build infra might be compromised... So why not just build the binary and use that one? Doesn't that make the issue irrelevant?

      2 replies 0 retweets 1 like
    10. Rene Mayrhofer‏ @rene_mobile May 25
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      Replying to @taviso @halvarflake and

      Because the original binary is typically signed by the vendor, and you may not be able to run it on the same platform without that signature. With a repro build, you can use the original binary and have (a degree of) certainty it matches the source. Even better are multi-sigs.

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

      The threat model is: You have a platform where you can't install any software unless it's signed by the vendor, but it's open source, and you think that vendor's build server is compromised? Which platform are we talking about, this seems like a fantasy threat model, no?

      12:06 PM - 25 May 2020
      2 replies 0 retweets 0 likes
        1. New conversation
        2. Rene Mayrhofer‏ @rene_mobile May 25
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          Replying to @taviso @halvarflake and

          https://wiki.debian.org/SecureBoot#Supported_architectures_and_packages … https://wiki.debian.org/SecureBoot/Discussion … https://wiki.debian.org/ReproducibleBuilds …

          2 replies 0 retweets 0 likes
        3. Tavis Ormandy‏Verified account @taviso May 25
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          Replying to @rene_mobile @halvarflake and

          I know how secure boot works Rene.

          0 replies 0 retweets 0 likes
        4. End of conversation
        1.  😷 Juliano Rizzo‏ @julianor May 25
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          Replying to @taviso @rene_mobile and

          looks like I missed the 1 signature requirement of the platform but anyway I don't see why this isn't a realistic risk if developers sign binaries using hard to protect systems and the private keys are exposed.

          0 replies 0 retweets 0 likes
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