sammccall added inline comments.
================ Comment at: clang-tools-extra/trunk/clangd/SourceCode.cpp:38 + // 0xxx is ASCII, handled above. 10xxx is a trailing byte, invalid here. + // 11111xxx is not valid UTF-8 at all. Assert because it's probably our bug. + assert((UTF8Length >= 2 && UTF8Length <= 4) && ---------------- benhamilton wrote: > sammccall wrote: > > benhamilton wrote: > > > This is user input, right? Have we actually checked for valid UTF-8, or > > > do we just assume it's valid? > > > > > > If not, it seems like an assertion is not the right check, but we should > > > reject it when we're reading the input. > > > > > Yeah, I wasn't sure about this, offline discussion tentatively concluded we > > wanted an assert, but I'm happy to switch to something else. > > > > We don't validate the code on the way in, so strings are "bytes of > > presumed-UTF8". This is usually not a big pain actually. But we > > could/should certainly make the JSON parser validate the UTF-8. (If we want > > to go this route, D45753 should be resolved first). > > > > There's two ways the assertion could fire: the code is invalid UTF-8, or > > there's a bug in the unicode logic here. I thought the latter was more > > likely at least in the short-term :) and this is the least invasive way to > > catch it. And if a developer build (assert-enabled) crashes because an > > editor feeds it invalid bytes, then that's probably better than doing > > nothing (though not as good as catching the error earlier). > The problem with not validating is it's easy to cause OOB memory access (and > thus security issues) if someone crafts malicious UTF-8 and makes us read off > the end of a string. > > We should be clear about the status of all strings in the documentation to > APIs. You still have to find/write a UTF-8 decoder that doesn't check bounds, which is (hopefully!) the harder part of writing that bug :-) But I agree in principle, there's more subtle attacks too, like `C08A` which is invalid but non-validating decoders will treat as a newline. I have a nearly-finished patch to add real validation to the JSON library, I'll copy you on it. Repository: rL LLVM https://reviews.llvm.org/D46035 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
