This pops up just a little over three years since we reached our first 1,000 forks. Also, 10,000 stars no too long ago.
A typical reason why people fork a project on GitHub, is so that they can make a change in their own copy of the source code and then suggest that change to the project in the form of a pull-request.
The curl project has almost 700 individual commit authors, which makes at least 2,300 forks done who still haven’t had their pull-requests accepted! Of course those are 700 contributors who actually managed to work all the way through to inclusion. We can imagine that there is a huge number of people who only ever thought about doing a change, some who only ever just started to do it, many who ditched the idea before it was completed, some who didn’t actually manage to implement it properly, some who got their idea and suggestion shut down by the project and of course, lots of people still have their half-finished change sitting there waiting for inspiration.
Then there are people who just never had the intention of sending any change back. Maybe they just wanted to tinker with the code and have fun. Some want to do private changes they don’t want to offer or perhaps they already know the upstream project won’t accept.
We just can’t tell.
Is 3,000 forks a lot or a little? Both. It is certainly more forks than we’ve ever had before in this project. But compared to some of the most popular projects on GitHub, even comparing to some other C projects (on GitHub the most popular projects are never written in C) our numbers are dwarfed by the really popular ones. You can probably guess which ones they are.
In the end, this number is next to totally meaningless as it doesn’t say anything about the project nor about what contributions we get or will get in the future. It tells us we have (or had) the attention of a lot of users and that’s about it.
I will continue to try to make sure we’re worth the attention, both now and going forward!
We announced our glorious return to the “bug bounty club” (projects that run bug bounties) a month ago, and with the curl 7.65.0 release today on May 22nd of 2019 we also ship fixes to security vulnerabilities that were reported within this bug bounty program.
Even before we publicly announced the program, it was made public on the Hackerone site. That was obviously enough to get noticed by people and we got the first reports immediately!
We have received 19 reports so far.
Quite clearly some people have some scripts laying around and they do some pretty standard things on projects that pop up on hackerone. We immediately got a number of reports that reported variations of the same two things repeatedly:
Our wiki is world editable. In my world I’ve lived under the assumption that this is how a wiki is meant to be but we ended up having to specifically mention this on curl’s hackerone page: yes it is open for everyone on purpose.
Sending emails forging them to look like the come from the curl web site might work since our DNS doesn’t have SPF, DKIM etc setup. This is a somewhat better report, but our bounty program is dedicated for and focused on the actual curl and libcurl products. Not our infrastructure.
Within two days of the program’s life time, the first legit report had been filed and then within a few more days a second arrived. They are CVE-2019-5435 and CVE-2019-5436, explained somewhat in my curl 7.65.0 release post but best described in their individual advisories, linked to below.
I’m thrilled to report that these two reporters were awarded money for their findings:
Wenchao Li was awarded 150 USD for finding and reporting CVE-2019-5435.
l00p3r was awarded 200 USD for finding and reporting CVE-2019-5436.
Both these issues were rated severity level “Low” and we consider them rather obscure and not likely to hurt very many users.
Donate to help us fund this!
Please notice that we are entirely depending on donated funds to be able to run this program. If you use curl and benefit from a more secure curl, please consider donating a little something for the cause!
After another eight week cycle was been completed, curl shipped a new release into the world. 7.65.0 brings some news and some security fixes but is primarily yet again a set of bug-fixes bundled up. Remember 7.64.1?
CURLOPT_MAXAGE_CONN is a new option that controls how long to keep a live connection in the connection cache for reuse.
This release comes with fixes for two separate security problems. Both rated low risk. Both reported via the new bug bounty program.
CVE-2019-5435 is an issue in the recently introduced URL parsing API. It is only a problem in 32 bit architectures and only if an application can be told to pass in ridiculously long (> 2GB) strings to libcurl. This bug is similar in nature to a few other bugs libcurl has had in the past, and to once and for all combat this kind of flaw libcurl now (in 7.65.0 and forward) has a “maximum string length” limit for strings that you can pass to it using its APIs. The maximum size is 8MB. (The reporter was awarded 150 USD for this find.)
CVE-2019-5436 is a problem in the TFTP code. If an application decides to uses a smaller “blksize” than 504 (default is 512), curl would overflow a buffer allocated on the heap with data received from the server. Luckily, very few people actually download data from unknown or even remote TFTP servers. Secondly, asking for a blksize smaller than 512 is rather pointless and also very rare: the primary point in changing that size is to enlarge it. (The reporter was awarded 200 USD for this find.)
Over one hundred bug-fixes landed in this release, but some of my favorites from release cycle include…
mark connection for close on TLS close_notify
close_notify is a message in the TLS protocol that means that this connection is about to close. In most circumstances that message doesn’t actually provide information to curl that is needed, but in the case the connection is closed prematurely, understanding that this message preceded the closure helps curl act appropriately. This change was done for the OpenSSL backend only as that’s where we got the bug reported and worked on it this time, but I think we might have reasons to do the same for other backends going forward!
show port in the verbose “Trying …” message
The verbose message that says “Trying 18.104.22.168…” means that curl has sent started a TCP connect attempt to that IP address. This message has now been modified to also include the target port number so when using -v with curl 7.65.0, connecting to that same host for HTTPS will instead say “Trying 22.214.171.124:443…”.
To aid debugging really. I think it gives more information faster at a place you’re already looking.
new SOCKS 4+5 test server
The test suite got a brand new SOCKS server! Previously, all SOCKS tests for both version 4 and version 5 were done by firing up ssh (typically openssh). That method was decent but made it hard to do a range of tests for bad behavior, bad protocol replies and similar. With the new custom test server, we can basically add whatever test we want and we’ve already extended the SOCKS testing to cover more code and use cases than previously.
SOCKS5 user name and passwords must be shorter than 256
curl allows user names and passwords provided in URLs and as separate options to be more or less unrestricted in size and that include if the credentials are used for SOCKS5 authentication – totally ignoring the fact that the protocol SOCKS5 has a maximum size of 255 for the fields. Starting now, curl will return an error if the credentials for SOCKS5 are too long.
Warn if curl and libcurl versions do not match
The command line tool and the library are independent and separable, as in you can run one version of the curl tool with another version of the libcurl library. The libcurl API is solid enough to allow it and the tool is independent enough to not restrict it further.
We always release curl the command line tool and libcurl the library together, using the same version number – with the code for both shipped in the same single file.
There should rarely be a good reason to actually run curl and libcurl with different versions. Starting now, curl will show a little warning if this is detected as we have learned that this is almost always a sign of an installation or setup mistake. Hopefully this message will aid people to detect the mistake earlier and easier.
Better handling of “–no-” prefixed options
curl’s command line parser allows users to switch off boolean options by prefixing them with dash dash no dash. For example we can switch off compressed responses by using “–no-compression” since there regular option “–compression” switches it on.
It turned out we stripped the “–no-” thing no regarding if the option was boolean or not and presumed the logic to handle it – which it didn’t. So users could actually pass a proxy string to curl with the regular option “–proxy” as well as “–no-proxy”. The latter of course not making much sense and was just due to an oversight.
In 7.65.0, only actual boolean command line options can be used with “–no-“. Trying it on other options will cause curl to report error for it.
Add CURLUPART_ZONEID to the URL API
Remember when we added a new URL parsing API to libcurl back in 7.62.0? It wasn’t even a year ago! When we did this, we also changed the internals to use the same code. It turned out we caused a regression when we parsed numerical IPv6 addresses that provide the zone ID within the string. Like this: “https://[ffe80::1%25eth0]/index.html”
Starting in this release, you can both set and get the zone ID in a URL using the API, but of course setting it doesn’t do anything unless the host is a numeric IPv6 address.
parse proxy with the URL parser API
We removed the separate proxy string parsing logic and instead switched that over to more appropriately use the generic URL parser for this purpose as well. This move reduced the code size, made the code simpler and makes sure we have a unified handling of URLs! Everyone is happy!
longer URL schemes
I naively wrote the URL parser to handle scheme names as long as the longest scheme we support in curl: 8 bytes. But since the parser can also be asked to parse URLs with non-supported schemes, that limit was a bit too harsh. I did a quick research, learned that the longest currently registered URI scheme is 36 characters (“microsoft.windows.camera.multipicker”). Starting in this release , curl accepts URL schemes up to 40 bytes long.
Coming up next
There’s several things brewing in the background that might be ready to show in next release. Parallel transfers in the curl tool and deprecating PolarSSL support seem likely to happen for example. Less likely for this release, but still being worked on slowly, is HTTP/3 support.
We’re also likely to get a bunch of changes and fine features we haven’t even thought about from our awesome contributors. In eight weeks I hope to write another one of these blog posts explaining what went into that release…
For the 6th consecutive year, the curl project is running a “user survey” to learn more about what people are using curl for, what think think of curl, what the need of curl and what they wish from curl going forward.
curl, or libcurl specifically, is probably the world’s most popular and widely used HTTP client side library counting more than six billion installs.
curl is a rock solid and feature-packed library that supports a huge amount of protocols and capabilities that surpass most competitors. But this comes at a cost: it is not the smallest library you can find.
Within a 100K
Instead of being happy with getting told that curl is “too big” for certain use cases, I set a goal for myself: make it possible to builda version of curl that can do HTTPS and fit in 100K (including the wolfSSL TLS library) on a typical 32 bit architecture.
As a comparison, the tiny-curl shared library when built on an x86-64 Linux, is smaller than 25% of the size as the default Debian shipped library is.
But let’s not stop there. Users with this kind of strict size requirements are rarely running a full Linux installation or similar OS. If you are sensitive about storage to the exact kilobyte level, you usually run a more slimmed down OS as well – so I decided that my initial tiny-curl effort should be done on FreeRTOS. That’s a fairly popular and free RTOS for the more resource constrained devices.
This port is still rough and I expect us to release follow-up releases soon that improves the FreeRTOS port and ideally also adds support for other popular RTOSes. Which RTOS would you like to support for that isn’t already supported?
Offer the libcurl API for HTTPS on FreeRTOS, within 100 kilobytes.
I strongly believe that the power of having libcurl in your embedded devices is partly powered by the libcurl API. The API that you can use for libcurl on any platform, that’s been around for a very long time and for which you can find numerous examples for on the Internet and in libcurl’s extensive documentation. Maintaining support for the API was of the highest priority.
My secondary goal was to patch as clean as possible so that we can upstream patches into the main curl source tree for the changes makes sense and that aren’t disturbing to the general code base, and for the work that we can’t we should be able to rebase on top of the curl code base with as little obstruction as possible going forward.
Keep the HTTPS basics
I just want to do HTTPS GET
That’s the mantra here. My patch disables a lot of protocols and features:
No protocols except HTTP(S) are supported
No cookie support
No date parsing
No HTTP authentication
No .netrc parsing
No HTTP multi-part formposts
No shuffled DNS support
No built-in progress meter
Although they’re all disabled individually so it is still easy to enable one or more of these for specific builds.
Most of the patches in tiny-curl are being upstreamed into curl in the #3844 pull request. I intend to upstream most, if not all, of the tiny-curl work over time.
The FreeRTOS port of tiny-curl is licensed GPLv3 and not MIT like the rest of curl. This is an experiment to see how we can do curl work like this in a sustainable way. If you want this under another license, we’re open for business over at wolfSSL!
As some of you already found out, I’ve tried live-streaming curl development recently. If you want to catch previous and upcoming episodes subscribe on my twitch page.
For the fun of it. I work alone from home most of the time and this is a way for me to interact with others.
To show what’s going on in curl right now. By streaming some of my development I also show what kind of work that’s being done, showing that a lot of development and work are being put into curl and I can share my thoughts and plans with a wider community. Perhaps this will help getting more people to help out or to tickle their imagination.
For the feedback and interaction. It is immediately notable that one of the biggest reasons I enjoy live-streaming is the chat with the audience and the instant feedback on mistakes I do or thoughts and plans I express. It becomes a back-and-forth and it is not at all just a one-way broadcast. The more my audience interact with me, the more fun I have! That’s also the reason I show the chat within the stream most of the time since parts of what I say and do are reactions and follow-ups to what happens there.
I can only hope I get even more feedback and comments as I get better at this and that people find out about what I’m doing here.
And really, by now I also think of it as a really concentrated and devoted hacking time. I can get a lot of things done during these streaming sessions! I’ll try to keep them going a while.
I decided to go with twitch simply because it is an established and known live-streaming platform. I didn’t do any deeper analyses or comparisons, but it seems to work fine for my purposes. I get a stream out with video and sound and people seem to be able to enjoy it.
As of this writing, there are 1645 people following me on twitch. Typical recent live-streams of mine have been watched by over a hundred simultaneous viewers. I also archive all past streams on Youtube, so you can get almost the same experience my watching back issues there.
I announce my upcoming streaming sessions as “events” on Twitch, and I announce them on twitter (@bagder you know). I try to stick to streaming on European day time hours basically because then I’m all alone at home and risk fewer interruptions or distractions from family members or similar.
It’s not as easy as it may look trying to write code or debug an issue while at the same time explaining what I do. I learnt that the sessions get better if I have real and meaty issues to deal with or features to add, rather than to just have a few light-weight things to polish.
I also quickly learned that it is better to now not show an actual screen of mine in the stream, but instead I show a crafted set of windows placed on the output to look like it is a screen. This way there’s a much smaller risk that I actually show off private stuff or other content that wasn’t meant for the audience to see. It also makes it easier to show a tidy, consistent and clear “desktop”.
Streaming makes me have to stay focused on the development and prevents me from drifting off and watching cats or reading amusing tweets for a while
So far we’ve been spared from the worst kind of behavior and people. We’ve only had some mild weirdos showing up in the chat and nothing that we couldn’t handle.
Equipment and software
I do all development on Linux so things have to work fine on Linux. Luckily, OBS Studio is a fine streaming app. With this, I can setup different “scenes” and I can change between them easily. Some of the scenes I have created are “emacs + term”, “browser” and “coffee break”.
When I want to show off me fiddling with the issues on github, I switch to the “browser” scene that primarily shows a big browser window (and the chat and the webcam in smaller windows).
When I want to show code, I switch to “emacs + term” that instead shows a terminal and an emacs window (and again the chat and the webcam in smaller windows), and so on.
OBS has built-in support for some of the major streaming services, including twitch, so it’s just a matter of pasting in a key in an input field, press ‘start streaming’ and go!
The rest of the software is the stuff I normally use anyway for developing. I don’t fake anything and I don’t make anything up. I use emacs, make, terminals, gdb etc. Everything this runs on my primary desktop Debian Linux machine that has 32GB of ram, an older i7-3770K CPU at 3.50GHz with a dual screen setup. The video of me is captured with a basic Logitech C270 webcam and the sound of my voice and the keyboard is picked up with my Sennheiser PC8 headset.
(This is a repost of the answer I posted on stackoverflow for this question. This answer immediately became my most ever upvoted answer on stackoverflow with 516 upvotes during the 48 hours it was up before a moderator deleted it for unspecified reasons. It had then already been marked “on hold” for being “primarily opinion- based” and then locked but kept: “exists because it has historical significance”. But apparently that wasn’t good enough. I’ve saved a screenshot of the deletion. Debated on meta.stackoverflow.com. Status now: it was brought back but remains locked.)
I’m Daniel Stenberg.
I made curl
I founded the curl project back in 1998, I wrote the initial curl version and I created libcurl. I’ve written more than half of all the 24,000 commits done in the source code repository up to this point in time. I’m still the lead developer of the project. To a large extent, curl is my baby.
I shipped the first version of curl as open source since I wanted to “give back” to the open source world that had given me so much code already. I had used so much open source and I wanted to be as cool as the other open source authors.
Thanks to it being open source, literally thousands of people have been able to help us out over the years and have improved the products, the documentation. the web site and just about every other detail around the project. curl and libcurl would never have become the products that they are today were they not open source. The list of contributors now surpass 1900 names and currently the list grows with a few hundred names per year.
Thanks to curl and libcurl being open source and liberally licensed, they were immediately adopted in numerous products and soon shipped by operating systems and Linux distributions everywhere thus getting a reach beyond imagination.
Thanks to them being “everywhere”, available and liberally licensed they got adopted and used everywhere and by everyone. It created a defacto transfer library standard.
At an estimated six billion installations world wide, we can safely say that curl is the most widely used internet transfer library in the world. It simply would not have gone there had it not been open source. curl runs in billions of mobile phones, a billion Windows 10 installations, in a half a billion games and several hundred million TVs – and more.
Should I have released it with proprietary license instead and charged users for it? It never occured to me, and it wouldn’t have worked because I would never had managed to create this kind of stellar project on my own. And projects and companies wouldn’t have used it.
Why do I still work on curl?
Now, why do I and my fellow curl developers still continue to develop curl and give it away for free to the world?
I can’t speak for my fellow project team members. We all participate in this for our own reasons.
I think it’s still the right thing to do. I’m proud of what we’ve accomplished and I truly want to make the world a better place and I think curl does its little part in this.
There are still bugs to fix and features to add!
curl is free but my time is not. I still have a job and someone still has to pay someone for me to get paid every month so that I can put food on the table for my family. I charge customers and companies to help them with curl. You too can get my help for a fee, which then indirectly helps making sure that curl continues to evolve, remain free and the kick-ass product it is.
curl was my spare time project for twenty years before I started working with it full time. I’ve had great jobs and worked on awesome projects. I’ve been in a position of luxury where I could continue to work on curl on my spare time and keep shipping a quality product for free. My work on curl has given me friends, boosted my career and taken me to places I would not have been at otherwise.
I would not do it differently if I could back and do it again.
Am I proud of what we’ve done?
Yes. So insanely much.
But I’m not satisfied with this and I’m not just leaning back, happy with what we’ve done. I keep working on curl every single day, to improve, to fix bugs, to add features and to make sure curl keeps being the number one file transfer solution for the world even going forward.
We do mistakes along the way. We make the wrong decisions and sometimes we implement things in crazy ways. But to win in the end and to conquer the world is about patience and endurance and constantly going back and reconsidering previous decisions and correcting previous mistakes. To continuously iterate, polish off rough edges and gradually improve over time.
Never give in. Never stop. Fix bugs. Add features. Iterate. To the end of time.
Yeah. For real.
Do I ever get tired? Is it ever done?
Sure I get tired at times. Working on something every day for over twenty years isn’t a paved downhill road. Sometimes there are obstacles. During times things are rough. Occasionally people are just as ugly and annoying as people can be.
But curl is my life’s project and I have patience. I have thick skin and I don’t give up easily. The tough times pass and most days are awesome. I get to hang out with awesome people and the reward is knowing that my code helps driving the Internet revolution everywhere is an ego boost above normal.
curl will never be “done” and so far I think work on curl is pretty much the most fun I can imagine. Yes, I still think so even after twenty years in the driver’s seat. And as long as I think it’s fun I intend to keep at it.
As a reader of my blog you know curl. You also most probably already
know why you would use curl and if I’m right, you’re also a fan of using
the right tool for the job. But do you know why others use
curl and why they switch from other solutions to relying on curl for
their current and future data transfers? Let me tell you the top reasons
I’m told by users.
Logging and exact error handling
What exactly happened in the transfer and why are terribly important
questions to some users, and with curl you have the tools to figure that
out and also be sure that curl either returns failure or the command
worked. This clear and binary distinction is important to users for whom
that single file every transfer is important. For example, some of the
largest and most well-known banks in the world use curl in their
back-ends where each file transfer can mean a transfer of extremely
large sums of money.
A few years ago I helped a money transaction service switch to curl
to get that exact line in the sand figured out. To know exactly and with
certainty if money had been transferred – or not – for a given
operation. Vital for their business.
curl does not have the browsers’ lenient approach of “anything goes
as long as we get something to show” when it comes to the Internet
curl’s verbose output options allow users to see exactly what curl sends and receives in a quick and non-complicated way. This is invaluable for developers to figure out what’s happening and what’s wrong, in either end involved in the data transfer.
curl’s verbose options allows developers to see all sent and received data even when encryption is used. And if that is not enough, its SSLKEYLOGFILE support allows you to take it to the next level when you need to!
Same behavior over time
Users sometimes upgrade their curl installations after several years
of not having done so. Bumping a software’s version after several years
and many releases, any software really, can be a bit of a journey and
adventure many times as things have changed, behavior is different and
things that previously worked no longer do etc.
With curl however, you can upgrade to a version that is a decade
newer, with lots of new fancy features and old crummy bugs fixed, only
to see that everything that used to work back in the day still works –
the same way. With curl, you can be sure that there’s an enormous focus on maintaining old functionality when going forward.
Present on all platforms
The fact that curl is highly portable, our users can have curl and
use curl on just about any platform you can think of and use it with the
same options and behaviors across them all. Learn curl on one platform,
then continue to use it the same way on the next system. Platforms and
their individual popularity vary over time and we enjoy to allow users
to pick the ones they like – and you can be sure that curl will run on
When doing the occasional file transfer every once in a while, raw
transfer performance doesn’t matter much. Most of the time will then
just be waiting on network anyway. You can easily get away with your
Python and java frameworks’ multiple levels of overhead and excessive
Users who scan the Internet or otherwise perform many thousands of
transfers per second from a large number of threads and machines realize
that they need fewer machines that spend less CPU time if they build
their file transfer solutions on top of curl. In curl we have a focus on
only doing what’s required and it’s a lean and trimmed solution with a
well-documented API built purely for Internet data transfers.
The features you want
The author of a banking application recently explained for us that
one of the top reasons why they switched to using curl for doing their
Internet data transfers, is curl’s ability to keep the file name from
curl is a feature-packed tool and library that most likely already
support the protocols you need and provide the power features you want.
With a healthy amount of “extension points” where you can extend it or
hook in your custom extra solution.
Support and documentation
No other tool or library for internet transfers have even close to
the same amount of documentation, examples available on the net,
existing user base that can help out and friendly users to support you
when you run into issues. Ask questions on the mailing lists, post a bug
on the bug tracker or even show your non-working code on stackoverflow
to further your project.
curl is really the only Internet transfer option available to get something that’s old and battle-proven proven by the giants of the industry, that is trustworthy, high-performing and yet for which you can also buy commercial support for, today.
There seems to be no end to updated posts about bug bounties in the curl project these days. Not long ago I mentioned the then new program that sadly enough was cancelled only a few months after its birth.
Now we are back with a new and refreshed bug bounty program! The curl bug bounty program reborn.
This new program, which hopefully will manage to survive a while, is setup in cooperation with the major bug bounty player out there: hackerone.
If you find or suspect a security related issue in curl or libcurl, report it! (and don’t speak about it in public at all until an agreed future date.)
You’re entitled to ask for a bounty for all and every valid and confirmed security problem that wasn’t already reported and that exists in the latest public release.
The curl security team will then assess the report and the problem and will then reward money depending on bug severity and other details.
We will of course also greatly appreciate any direct sponsorships from companies for this program. You can help curl getting even better by adding funds to the bounty program and help us reward hard-working researchers.
Why bounties at all?
We compete for the security researchers’ time and attention with other projects, both open and proprietary. The projects that can help put food on these researchers’ tables might have a better chance of getting them to use their tools, time, skills and fingers to find our problems instead of someone else’s.
Finding and disclosing security problems can be very time and resource consuming. We want to make it less likely that people give up their attempts before they find anything. We can help full and part time security engineers sustain their livelihood by paying for the fruits of their labor. At least a little bit.
Only released code?
The state of the code repository in git is not subject for bounties. We need to allow developers to do mistakes and to experiment a little in the git repository, while we expect and want every actual public release to be free from security vulnerabilities.
So yes, the obvious downside with this is that someone could spot an issue in git and decide not to report it since it doesn’t give any money and hope that the flaw will linger around and ship in the release – and then reported it and claim reward money. I think we just have to trust that this will not be a standard practice and if we in fact notice that someone tries to exploit the bounty in this manner, we can consider counter-measures then.
How about money for the patches?
There’s of course always a discussion as to why we should pay anyone for bugs and then why just pay for reported security problems and not for heroes who authored the code in the first place and neither for the good people who write the patches to fix the reported issues. Those are valid questions and we would of course rather pay every contributor a lot of money, but we don’t have the funds for that. And getting funding for this kind of dedicated bug bounties seem to be doable, where as a generic pay contributors fund is trickier both to attract money but it is also really hard to distribute in an open project of curl’s nature.
How much money?
At the start of this program the award amounts are as following. We reward up to this amount of money for vulnerabilities of the following security levels:
We’re running a short poll asking people about where and how we should organize curl up 2020 – our annual curl developers conference. I’m not making any promises, but getting people’s opinions will help us when preparing for next year.