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Comment by emmelaich | Hacker News Reader

Surely the opposite? If everything was very pedantic and strict, the 'net would be so brittle as to be non-functional.

You're imagining a world where things get specified and implemented completely correctly. Which does not exist and probably can't!

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That's what Postel thought. He was wrong. Allowing everything creates a brittle system because the system has to accept all the undocumented behaviour that other broken systems emit. If broken files were rejected quickly, nobody would generate them.

There's a difference between unknown extensions following a known format, and data that's simply broken (e.g. offset pointer past end of data).

You're not accounting for the incorrectly rejected file / protocols. And incomplete protocol specifications.

And generally I think critics of Postel are lacking the context in which they were made. You and probably others would actually make similar decisions than Postel for many particular issues.

I disagree that I'd make similar decisions. Postel's Law is a big part of the reason Bleichenbacher attacks (adaptive chosen-ciphertext attacks)[1] stayed so common for so long. As an engineer responsible for the security I absolutely reject malformed inputs.

https://en.wikipedia.org/wiki/Adaptive_chosen-ciphertext_att...

But that's what I'm saying; Postel may well have ALSO rejected malformed inputs in this particular case.

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