daniellehmann

6 ms·

1.
by daniellehmann 5y ago
This is not correct, it is not necessary to specify a maximum memory size. See the WebAssembly specification https://webassembly.github.io/spec/core/syntax/modules.html#... . Due to 32-bit address space, the m
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by daniellehmann 5y ago
Very cool, thanks a lot for the example!
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by daniellehmann 5y ago
My reading of the article is not that it promotes "anti-intellectualism" or that it argues to remove all implicit precedence or associativity rules. I think it actually gives a nuanced answer to your question "where do you dr
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by daniellehmann 5y ago
I don't know Swift, but does this mean there are expressions in Swift where the compiler returns an error, because the expression is ambiguous without additional parentheses? (My understanding of the article is that it mainly argues fo
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by daniellehmann 5y ago
See e.g. https://www.digwebinterface.com/?hostnames=facebook.com&ns=a... for responses from different nameservers.
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by daniellehmann 5y ago
Thanks. You are referring to the example exploit in section 5.3, right? Please note that this example is for a standalone VM, not inside the browser (where JavaScript programs -- and by extension, WebAssembly modules -- do not have direct a
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by daniellehmann 5y ago
I don't think that's a fair assessment, and it is also not fair to the designers of WebAssembly. They certainly have spent a lot of thoughts on protecting the host (e.g., browser, underlying OS) from _malicious_ WebAssembly code.
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by daniellehmann 5y ago
Thanks a lot for the additional background, and also for all the work on WebAssembly. It is a very cool language and having it available with linear memory now is much better than if it were still in the works due to figuring out page prote
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by daniellehmann 5y ago
Good summary and clarification. Yes, we do not aim to break out of the (browser) sandbox, and yes the example exploits only use functions that are already imported into the vulnerable WebAssembly module. However, I would draw a bit more att
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by daniellehmann 5y ago
Daniel here, one of the authors. You are right, some of the issues highlighted in the paper could be solved by compilers targeting WebAssembly. One such mitigation that is (currently) missing are stack canaries. In contrast, stack canaries
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by daniellehmann 5y ago
Daniel [1], one of the authors here. Feel free to ask also technical questions, I'll try my best to answer them. If you don't feel like reading the whole paper, there is also a short (~10 min) video on the conference website [2],
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by daniellehmann 6y ago
> This doesn't really seem to offer anything useful, or even contain new information. You are right in that we do not try to attack a concrete host implementation or aim to break out of the sandbox. I disagree, however, that securit
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by daniellehmann 6y ago
Excellent explanations. > C++ compiled to WebAssembly generally manages its own parallel "shadow stack" in linear memory In the paper, we call the compiler-organized stack in linear memory the "unmanaged stack", to di
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by daniellehmann 6y ago
> Do some of the safety measures you consider translate well in this model? Yes, I think several mitigations could be deployed without requiring a change to the language, only by changing compilers and runtime libraries: * Stack canaries
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by daniellehmann 6y ago
> some C library you have compiled to WASM: wrap that functionality up with an interface, compile that to WASM, and only pass it the image data you're happy for it to see That is good advice. Separately compiling C code into individ
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by daniellehmann 6y ago
I am not sure I understand the sentence "limiting the WA spec to only try to sandbox the WA binary from outside memory". I would not say that we (as in: the authors of the paper) are trying to limit the spec, or that we tried to o
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by daniellehmann 6y ago
Hi everyone, Daniel here (one of the authors, I am the PhD student in the video). Great to see the paper submitted and discussed :-) Sorry for being a bit late to the discussion, I will try to answer the questions in detail that were asked
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by daniellehmann 8y ago
Thanks for the warm words, happy to hear that others are interested in this project and WebAssembly in general! Regarding your question: No, I have not yet contacted the WebAssembly people at Mozilla. But it's definitely a good idea to
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by daniellehmann 8y ago
Daniel here, PhD student working on this. Ask away if you have any questions :) For now, this is in an early stage, so probably mostly interesting to researchers or as inspiration. But I am working on making it more usable (adding documenta