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Comment by hansifer | Hacker News Reader

At their peril, because any set of rules, no matter how seemingly simple, has edge cases that only become apparent once we take on the task of implementing them at the code level into a functioning app. And that's assuming specs have been written up by someone who has made every effort to consider every relevant condition, which is never the case.

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And in the example of "why" this 401 is happening that's another one of those. The spec might have said to return a 401 for both not being authenticated and for not having enough privileges.

But that's just plain wrong and a proper developer would be allowed to change that. If you're not authenticating properly, you get a 401. That means you can't prove you're who you say you are.

If you are past that, i.e. we know that you are who you say you are, then the proper return code is 403 for saying "You are not allowed to access what you're trying to access, given who you are".

Which funnily enough seems to be a very elusive concept to many humans as well, never mind an LLM.

...then there are the other fun ones, like not wanting to tell people things exist that they don't have access to, like Github returning 404 errors for private repositories you know exist when you aren't logged into an account that has access to them.

That one at least makes sense if you ask me. It's not just Github doing it. On the web side of things you'd return the same "no such thing here" page whether you don't have access or it really doesn't exist as well. So leaking more info than the page you return to users in the browser would show via the status code would not be good.

I.e. that would be the appropriate thing to do if you're trying to prevent leakage of information i.e. enumeration of resources. But you should not return 401 for this still. A 404 is the appropriate response for pretending that "it's just not there" if you ask me. You can't return 404 when it's not there and a 403 when you have no access if enumeration is bad.

So for example, if you don't have access to say the settings of a repo you have access to, a 403 is OK. No use pretending with a 404, because we all know the settings are just a feature of Github.

However, pretending that a repo you don't have access to but exists isn't there with a 404 is appropriate because otherwise you could prove the existence of "superSecretRepo123" simply by guessing and getting a 403 instead of a 404.

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