Messages in this thread | | | Date | Tue, 17 Feb 2004 19:53:48 +0000 | From | viro@parcelfa ... | Subject | Re: UTF-8 practically vs. theoretically in the VFS API (was: Re: JFS default behavior) |
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On Tue, Feb 17, 2004 at 07:29:18PM +0000, Jamie Lokier wrote: > What happens is that one program or library checks an incoming path > for ".." components - that code knows nothing about UTF-8 of course. > > Then it passes the string to another program which assumes the path > has been subject to appropriate security checks, munges it in UTF-8, > and eventually does a file operation with it. The munging generates > ".." components from non-minimal UTF-8 forms - if it's not obeying the > Unicode rejection requirement (which wasn't in earlier versions), that is. Why the hell would it _ever_ do such normalization?
> A realistic example is where the second program reads files whose > paths are mentioned in a text file which is parsed as UTF-8, after the > first program has done a security check by grepping for ".." > components. > > Unicode says the second program shouldn't accept malformed UTF-8, > precisely because in real scenarios (like this one) there's a mix of > programs and libraries, some aware of UTF-8, some not, and the latter > are involved in security decisions. > > Here on linux-kernel we're saying that if the second program accepts > any old byte sequence in a filename, it should preserve the byte > sequence exactly. But any program whose parser-tokeniser is scanning > UTF-8 is very unlikely to do that - it's just too complicated to say > some bits of a text stream must be remembered as literal bytes, and > others must be scanned as multibyte characters.
So what you are saying is that conversion of invalid multibyte sequences into non-error wide chars followed by conversion back into UTF-8 can lead to trouble? *DUH*
> The holes only arise because software which is interpreting UTF-8 is > mixed with software which isn't. That's one of the most useful > features of UTF-8, after all - that's why we use it for filenames.
The holes only arise because software which is interpreting UTF-8 doesn't care to do it properly. Software that doesn't interpret it (including the kernel) doesn't enter the picture at all. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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