Hacker News Reader

Comment by spacechild1 | Hacker News Reader

> Sure enough, the function StrAppend potentially overflows a size_t size

How should this happen in practice? The three strings would have to be larger than the available address space...

Yeah. The function in question is called in only one place. It would seem you’d need to send the web server more than a size_t of data for this to be an issue.

Exactly. In a single file C nobody can expect to get universal library functions that work in any possible imaginable context. The only relevant context is the code the function is in. And in that context, the function is doing enough.

Yes, absolutely. If the webserver is compiled 32-bit, that is only 4GB of data, which might be feasible? I don't know enough to say. Assuming a hacker kindly won't overflow your buffer is never a good idea.

However, the presence of one piece of code that is not integer-overflow safe definitely makes me nervous. This is just the one I found in 5 minutes, what else is in there?

None that stand out to me, including what you posted. Do you have a real example?

It's not an integer overflow that would be needed but an unsigned overflow. The way I see it, on 32-bits, that means that the size HTTP request would have to be bigger than what's available to both user application and the OS together. In short, one just can't get the input request that big. Of course, if you manage that, you'll disprove this claim.

MAX_CONTENT_LENGTH is 250MB. You won’t be able to send 4GB of data.

In most places it uses int for string and buffer sizes lengths. It wouldn't surprize me if 2GiB of data could trigger several overflows.

And there's only one call to StrAppend() which is easily verified as safe.

Reply on news.ycombinator.com