Post AXAHMlUUokeiKTcsGe by sam@queernerds.social
 (DIR) More posts by sam@queernerds.social
 (DIR) Post #AXAGaBrjy3ZTwLKuKO by mjg59@nondeterministic.computer
       2023-06-28T22:53:04Z
       
       0 likes, 0 repeats
       
       Quiz! Why is it bad if a measured boot implementation allows you to use the attestation signing keys to sign arbitrary material?
       
 (DIR) Post #AXAGlKDvEZIh2x1MhM by gwync@mastodon.coffee
       2023-06-28T22:54:53Z
       
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       @mjg59 ...the answer is in the question?
       
 (DIR) Post #AXAGwpsJtWGcOiPC9g by natanbc@uwu.social
       2023-06-28T22:55:15Z
       
       0 likes, 0 repeats
       
       @mjg59 use fake measurements as the material, boot whatever you want and pretend to be something else
       
 (DIR) Post #AXAH7bPM1W0kiJzUkS by leo@60228.dev
       2023-06-28T22:55:26Z
       
       0 likes, 0 repeats
       
       @mjg59 because you could just sign a fake attestation?
       
 (DIR) Post #AXAH7i8F1XTvZH2QXw by leo@60228.dev
       2023-06-28T22:56:06Z
       
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       @mjg59 is this going to be a "congratulations! all replies were better at security than vendor" thing
       
 (DIR) Post #AXAHMlUUokeiKTcsGe by sam@queernerds.social
       2023-06-28T23:00:25Z
       
       0 likes, 0 repeats
       
       @mjg59 Oh no
       
 (DIR) Post #AXAJgsl5hpx0ZN6n7g by penguin42@mastodon.org.uk
       2023-06-28T23:29:48Z
       
       0 likes, 0 repeats
       
       @mjg59 Because you might sign something that looks strangely similar to an attestation?
       
 (DIR) Post #AXAKd9ztlpZopYp8JU by adb@infosec.exchange
       2023-06-28T23:37:45Z
       
       0 likes, 0 repeats
       
       @mjg59 It becomes ... unmeasured.
       
 (DIR) Post #AXALFLgGmQtq4PqtTk by LucasWerkmeister@wikis.world
       2023-06-28T23:45:51Z
       
       0 likes, 0 repeats
       
       @mjg59 sure, I’ll join the party. because you can have it sign a fake boot sequence and present that to a remote party instead of the real boot sequence (which the implementation also signed), rendering the attestation useless
       
 (DIR) Post #AXARJTlvErl031qguu by mjg59@nondeterministic.computer
       2023-06-29T00:53:51Z
       
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       Framing the question this way does make the answer a little more obvious, but well done everyone! If an attestation key can sign arbitrary material, it can sign a fake set of measurements. This means it's also necessary to make it clear what sort of attestation an attestation key is signing - if I can construct a key that looks like a measurement and then attest to ownership of that key, whatever is consuming that attestation may mistake it for a legitimate measurement
       
 (DIR) Post #AXGOr9qOhbq7At4M3U by socrates1024@cryptodon.lol
       2023-07-01T21:51:11Z
       
       0 likes, 0 repeats
       
       @mjg59 on the other hand, if domain separators are inserted by the platform in a sensible way, you can sign arbitrary messages after a session-specific separator