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Being liberal in what you accept is fine, iff strictly define the variations in the grammar. Meredith and Sergey's outstanding talk about properly parsing all
by pdkl95 11y ago
Being liberal in what you accept is fine, iff strictly define the variations in the grammar.
Meredith and Sergey's outstanding talk about properly parsing all input discusses this update to how Postel's Law should be interpreted.
https://media.ccc.de/v/28c3-4763-en-the_science_of_insecurit https://media.ccc.de/v/28c3-4763-en-the_science_of_insecurit
- quanticle 11y agoI would argue that if you're strictly defining the accepted variations in the grammar, then all you've done is define a new grammar that you're conservatively adhering to. And that's fine! There's no rule that says that standards cannot evolve to match new use cases. However, I would argue that having a strictly defined (yet evolving) standard is much different than the common interpretation of Postel's Law, which is that undefined behavior should "do the right thing", with the specific interpretation of "the right thing" being left to the implementers. Predictably, different implementers interpret that in different ways, which leads to security holes. But if the specification defines what the right thing to do is, then the behavior is no longer undefined, and therefore Postel's Law no longer applies.
- VMG 11y agoThanks! The link is missing a trailing `y`.