Wheeler: Fixing Unix/Linux/POSIX Filenames [LWN.net]

Wheeler: Fixing Unix/Linux/POSIX Filenames

Posted Mar 29, 2009 21:58 UTC (Sun) by clugstj (subscriber, #4020)
In reply to: Wheeler: Fixing Unix/Linux/POSIX Filenames by epa
Parent article: Wheeler: Fixing Unix/Linux/POSIX Filenames

No, it is very possible to write such a function. The character encoding issue only prevents you from assuring that the string matches what the file's creator thought it should be. This doesn't represent a security problem.

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Wheeler: Fixing Unix/Linux/POSIX Filenames

Posted Mar 29, 2009 22:37 UTC (Sun) by epa (subscriber, #39769) [Link]

No, it is very possible to write such a function. The character encoding issue only prevents you from assuring that the string matches what the file's creator thought it should be.

Well, yeah. If you allow the function to return the wrong answer, then it is easy to write. But it is not possible to in all cases return the correct filename to the user, matching the original one chosen by the user. If you pick a known encoding everywhere (UTF-8 being the obvious choice) then the problem goes away.

This doesn't represent a security problem.

Correct (at least none that I can think of). The security issue is with special characters and control characters in filenames, and is separate to the issue of how to encode characters that don't fit in ASCII.