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Althttpd: Simple webserver in a single C file

sqlite.org

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Re: Althttpd: Simple webserver in a single C file

#261

Post by ectospheno »

spacechild1 wrote: post #260
geoffdunbar wrote: post #258

Earlier quoted context omitted.

I love C, but it's pretty scary sometime. 5 minutes ago, "I wonder if I can find a potential memory overwrite in 5 minutes?" Sure enough, the function StrAppend potentially overflows a size_t size (without checking), and then writes into memory could be past the end of the allocated buffer. Given 5 minutes, I didn't look thoroughly if this is actually exploitable, but it's definitely a red-flag for the code. Be caref…

> 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.

Re: Althttpd: Simple webserver in a single C file

#262

Post by yawaramin »

tyingq wrote: post #151
geocrasher wrote: post #146

I have yet to try running this for anything, but I do appreciate how it really sticks to the "do one thing well" ethos. Modern web servers can be extremely complicated with a lot of moving parts. This boils it down to just one thing and lets a person focus on the project instead of the infrastructure. Granted, it's very simplistic, but that's its strength.

I do respect the technical chops around sqlite. However, I think a "fork for every single http request" server isn't really useful in many situations. That the sqlite website is able to run this way is more a testament to Linux's work on a lightweight/fast fork() than anything else. This would perform terribly on a more traditional Unix.

But pretty much nobody is is running a more traditional Unix nowadays. Almost everyone uses Linux for web servers. So let's judge the tool based on its actual context, not on an unrealistic one.

Re: Althttpd: Simple webserver in a single C file

#263

Post by jackewiehose »

spacechild1 wrote: post #260
geoffdunbar wrote: post #258

Earlier quoted context omitted.

I love C, but it's pretty scary sometime. 5 minutes ago, "I wonder if I can find a potential memory overwrite in 5 minutes?" Sure enough, the function StrAppend potentially overflows a size_t size (without checking), and then writes into memory could be past the end of the allocated buffer. Given 5 minutes, I didn't look thoroughly if this is actually exploitable, but it's definitely a red-flag for the code. Be caref…

> 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...

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

Re: Althttpd: Simple webserver in a single C file

#264

Post by acqq »

ectospheno wrote: post #261
spacechild1 wrote: post #260

Earlier quoted context omitted.

> 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.

Re: Althttpd: Simple webserver in a single C file

#265

Post by wubawam »

40four wrote: post #259
ankurpatel wrote: post #150

Performance is really bad. This is good for running a small HTTP server on an embedded device but if plan is to use it for HTTP server to serve production web traffic performance is really bad. Below is report of running the server and hitting a minimal index.html page and hitting it with artillery. All virtual users finished Summary report @ 09:39:57(-0400) 2021-06-08 Scenarios launched: 33645 Scenarios completed: 2…

Fair enough, but when considering the reasons and decisions behind using this server from the developers, isn’t your point kind of moot? It’s not optimized for high ‘performance’. It’s optimized for low resource usage, and the ability to reliably serve large amounts of requests on a small budget, right? They state that the website is currently serving 500K requests & 50GB of bandwidth per day. Respectfully, this is q…

That's not a lot of requests.

My hobby website serves more traffic for a 1/4 of the cost and is easy to configure.

Re: Althttpd: Simple webserver in a single C file

#266

Post by geoffdunbar »

ectospheno wrote: post #261
spacechild1 wrote: post #260

Earlier quoted context omitted.

> 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.

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?

Re: Althttpd: Simple webserver in a single C file

#267

Post by tyingq »

yawaramin wrote: post #262
tyingq wrote: post #151

Earlier quoted context omitted.

I do respect the technical chops around sqlite. However, I think a "fork for every single http request" server isn't really useful in many situations. That the sqlite website is able to run this way is more a testament to Linux's work on a lightweight/fast fork() than anything else. This would perform terribly on a more traditional Unix.

But pretty much nobody is is running a more traditional Unix nowadays. Almost everyone uses Linux for web servers. So let's judge the tool based on its actual context, not on an unrealistic one.

I'm saying it's not terribly interesting or broadly useful, unlike the rest of sqlite, which is. There are other minimal http servers that are vastly more efficient without being much more complicated.

Re: Althttpd: Simple webserver in a single C file

#268

Post by SQLite »

GordonS wrote: post #241
0xbadcafebee wrote: post #135

> As of 2018, the althttpd instance for sqlite.org answers about 500,000 HTTP requests per day (about 5 or 6 per second) delivering about 50GB of content per day (about 4.6 megabits/second) on a $40/month Linode. The load average on this machine normally stays around 0.1 or 0.2 Interesting. If the load avg is consistently low, it could mean they're over-paying for CPU. If this was a non-dedicated AWS instance you mig…

> I'm also curious how much of that bandwidth couldn't be offset by a CDN or mirrors As you say, at $40/m it's academic for a lot of people, but AFAIK, the whole site is static, so presumably if you put it behind Cloudflare’s free tier it would serve all but the file downloads from the edge. A pure guess, but I'd imagine that would mean serving 75% of requests from the edge.

Look again. The entire Althttpd website is 100% dynamic. Notice that the hyperlink at the very top of this HN article is to a Markdown file (althttpd.md). A CGI runs to convert this into HTML for your web-browser.

The core SQLite website has a lot of static content, but there are dynamic elements, such as Search (https://www.sqlite.org/search?s=d&q=sqlite) and the source code repository (https://www.sqlite.org/src/timeline?n=100&y=ci).

So far today, 23.48% of HTTP requests to the sqlite.org domain are for dynamic content, according to server logs.

Re: Althttpd: Simple webserver in a single C file

#269

Post by sangnoir »

IanCal wrote: post #242
sangnoir wrote: post #168

Earlier quoted context omitted.

> Having commits that do not build represents the history more accurately. Sure it does, but sometimes that level of detail in history is not helpful. Individual keystrokes are an even finer/"more accurate" representation of history; but who wants that? At some point, having more granular detail becomes noise - the root of the disconnect is that people have a difference in opinion on which level that is: for some (li…

Can you not just skip all non-merge commits?

Sure, I can - but should I? That's the fundamental difference in opinion (which I don't think can be reconciled). I don't need to know what the developer was thinking or follow the individual steps when they developing a feature or fixing a bug, for me, the merge is the fundamental unit of work, and not individual commits. Caveat: I'm the commit-as-you-go type of developer, as most developers are (branching really is cheap in Git). If everyone was disciplined enough not to make commits out of WIP code, and every commit was self-contained and complete, I'd be all for taking commits as the fundamental unit of code change

If the author did something edgy or hard-to-understand with the change-set, I expect to see an explanation why it was done that way as a comment near the code in question, rather than as a sequence of commit-messages, that is the last place I will look - but that's just me

Re: Althttpd: Simple webserver in a single C file

#270

Post by ectospheno »

geoffdunbar wrote: post #266
ectospheno wrote: post #261

Earlier quoted context omitted.

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.

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?
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