I’m happy to announce that curl now supports a third SSH library option: wolfSSH. Using this, you can build curl and libcurl to do SFTP transfers in a really small footprint that’s perfectly suitable for embedded systems and others. This goes excellent together with the tiny-curl effort.
The initial merge of this functionality only provides SFTP ability and not SCP. There’s really no deeper thoughts behind this other than that the work has been staged and the code is smaller for SFTP-only and it might be that users on these smaller devices are happy with SFTP-only.
Work on adding SCP support for the wolfSSH backend can be done at a later time if we feel the need. Let me know if you’re one such user!
Build time selection
You select which SSH backend to use at build time. When you invoke the configure script, you decide if wolfSSH, libssh2 or libssh is the correct choice for you (and you need to have the correct dev version of the desired library installed).
The initial SFTP and SCP support was added to curl in November 2006, powered by libssh2 (the first release to ship it was 7.16.1). Support for getting those protocols handled by libssh instead (which is a separate library, they’re just named very similarly) was merged in October 2017.
WolfSSH uses WolfSSL functions
If you decide to use the wolfSSH backend for SFTP, it is also possibly a good idea to go with WolfSSL for the TLS backend to power HTTPS and others.
A plethora of third party libs
WolfSSH becomes the 32nd third party component that curl can currently be built to use. See the slide below and click on it to get the full resolution version.
I, Daniel, wrote the initial new wolfSSH backend code. Merged in this commit.
I’m please to invite you to our live webinar, “Why everyone is using curl and you should too!”, hosted by wolfSSL. Daniel Stenberg (me!), founder and Chief Architect of curl, will be live and talking about why everyone is using curl and you should too!
This is planned to last roughly 20-30 minutes with a following 10 minutes Q&A.
Space is limited so please register early!
When: Jan 14, 2020 08:00 AM Pacific Time (US and Canada) (16:00 UTC)
Register in advance for this webinar!
After registering, you will receive a confirmation email containing information about joining the webinar.
Not able to attend? Register now and after the event you will receive an email with link to the recorded presentation.
2019 is special in my heart. 2019 was different than many other years to me in several ways. It was a great year! This is what 2019 was to me.
curl and wolfSSL
I quit Mozilla last year and in the beginning of the year I could announce that I joined wolfSSL. For the first time in my life I could actually work with curl on my day job. As the project turned 21 I had spent somewhere in the neighborhood of 15,000 unpaid spare time hours on it and now I could finally do it “for real”. It’s huge.
Just in November 2018 the name HTTP/3 was set and this year has been all about getting it ready. I was proud to land and promote HTTP/3 in curl just before the first browser (Chrome) announced their support. The standard is still in progress and we hope to see it ship not too long into next year.
Focusing on curl full time allows a different kind of focus. I’ve landed more commits in curl during 2019 than any other year going back all the way to 2005. We also reached 25,000 commits and 3,000 forks on github.
We’ve added HTTP/3, alt-svc, parallel transfers in the curl tool, tiny-curl, fixed hundreds of bugs and much, much more. Ten days before the end of the year, I’ve authored 57% (over 700) of all the commits done in curl during 2019.
We also (re)started our own curl Bug Bounty in 2019 together with Hackerone and paid over 1000 USD in rewards through-out the year. It was so successful we’re determined to raise the amounts significantly going into 2020.
I’ve done 28 talks in six countries. A crazy amount in front of a lot of people.
When Github had their Github Universe event in November and talked about their new sponsors program on stage (which I am part of, you can sponsor me) this huge quote of mine was shown on the big screen.
Maybe not media, but in no less than two Mr Robot episodes we could see curl commands in a TV show!
The Internet Museum translated to Swedish becomes “internetmuseum“. It is a digital, online-only, museum that collects Internet- and Web related historical information, especially focused on the Swedish angle to all of this. It collects stories from people who did the things. The pioneers, the ground breakers, the leaders, the early visionaries. Most of their documentation is done in the form of video interviews.
I was approached and asked to be part of this – as an Internet Pioneer. Me? Internet Pioneer, really?
I’m humbled and honored to be considered and I certainly had a lot of fun doing this interview. To all my friends not (yet) fluent in Swedish: here’s your grand opportunity to practice, because this is done entirely in this language of curl founders and muppet chefs.
Back in the morning of October 18th 2019, two guys showed up as planned at my door and I let them in. One of my guests was a photographer who set up his gear in my living room for the interview, and then me and and guest number two, interviewer Jörgen, sat down and talked for almost an hour straight while being recorded.
The result can be seen here below.
The Science museum was first
This is in fact the second Swedish museum to feature me.
I have already been honored with a display about me, at the Tekniska Museet in Stockholm, the “Science museum” which has an exhibition about past Polhem Prize award winners.
Six weeks after our previous bug-fix release, we ship a second release in a row with nothing but bug-fixes. We call it 7.65.2. We decided to go through this full release cycle with a focus on fixing bugs (and not merge any new features) since even after 7.65.1 shipped as a bug-fix only release we still seemed to get reports indicating problems we wanted fixed once and for all.
Also, I personally had a vacation already planned to happen during this period (and I did) so it worked out pretty good to take this cycle as a slightly calmer one.
Of the numbers below, we can especially celebrate that we’ve now received code commits by more than 700 persons!
the 183rd release 0 changes 42 days (total: 7,789) 76 bug fixes (total: 5,259) 113 commits (total: 24,500) 0 new public libcurl function (total: 80) 0 new curl_easy_setopt() option (total: 267) 0 new curl command line option (total: 221) 46 contributors, 25 new (total: 1,990) 30 authors, 19 new (total: 706) 1 security fix (total: 90) 200 USD paid in Bug Bounties
Since the previous release we’ve shipped a security fix. It was special in the way that it wasn’t actually a bug in the curl source code, but in the build procedure for how we made curl builds for Windows. For this report, we paid out a 200 USD bug bounty!
Bug-fixes of interest
As usual I’ve carved out a list with some of the bugs since the previous release that I find interesting and that could warrant a little extra highlighting. Check the full changelog on the curl site.
bindlocal: detect and avoid IP version mismatches in bind
It turned out you could ask curl to connect to a IPv4 site and if you then asked it to bind to an interface in the local end, it could actually bind to an ipv6 address (or vice versa) and then cause havok and fail. Now we make sure to stick to the same IP version for both!
configure: more –disable switches to toggle off individual features
As part of the recent tiny-curl effort, more parts of curl can be disabled in the build and now all of them can be controlled by options to the configure script. We also now have a test that verifies that all the disabled-defines are indeed possible to set with configure!
(A future version could certainly get a better UI/way to configure which parts to enable/disable!)
http2: call done_sending on end of upload
Turned out a very small upload over HTTP/2 could sometimes end up not getting the “upload done” flag set and it would then just linger around or eventually cause a time-out…
libcurl: Restrict redirect schemes to HTTP(S), and FTP(S)
As a stronger safety-precaution, we’ve now made the default set of protocols that are accepted to redirect to much smaller than before. The set of protocols are still settable by applications using the CURLOPT_REDIR_PROTOCOLS option.
multi: enable multiplexing by default (again)
Embarrassingly enough this default was accidentally switched off in 7.65.0 but now we’re back to enabling multiplexing by default for multi interface uses.
multi: fix the transfer hashes in the socket hash entries
The handling of multiple transfers on the same socket was flawed and previous attempts to fix them were incorrect or simply partial. Now we have an improved system and in fact we now store a separate connection hash table for each internal separate socket object.
openssl: fix pubkey/signature algorithm detection in certinfo
The CURLINFO_CERTINFO option broke with OpenSSL 1.1.0+, but now we have finally caught up with the necessary API changes and it should now work again just as well independent of which version you build curl to use!
runtests: keep logfiles around by default
Previously, when you run curl’s test suite, it automatically deleted the log files on success and you had to use runtests.pl -k to prevent it from doing this. Starting now, it will erase the log files on start and not on exit so they will now always be kept on exit no matter how the tests run. Just a convenience thing.
runtests: report single test time + total duration
The output from runtests.pl when it runs each test, one by one, will now include timing information about each individual test. How long each test took and how long time it has spent on the tests so far. This will help us detect if specific tests suddenly takes a very long time and helps us see how they perform in the remote CI build farms etc.
I truly think we’ve now caught up with the worst problems and can now allow features to get merged again. We have some fun ones in the pipe that I can’t wait to put in the hands of users out there…
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!
I view myself as primarily a software developer. Perhaps secondary as someone who’s somewhat knowledgeable in networking and is participating in protocol development and discussions. I do not regularly proclaim myself to be a “speaker” or someone who’s even very good at talking in front of people.
Time to wake up and face reality? I’m slowly starting to realize that I’m actually doing more presentations than ever before in my life and I’m enjoying it.
Since October 2015 I’ve done 53 talks and presentations in front of audiences – in ten countries. That’s one presentation done every 25 days on average. (The start date of this count is a little random but it just happens that I started to keep a proper log then.) I’ve talked to huge audiences and to small. I done presentations that were appreciated and I’ve done some that were less successful.
My increased frequency in speaking engagements coincides with me starting to work full-time from home back in 2014. Going to places to speak is one way to get out of the house and see the “real world” a little bit and see what the real people are doing. And a chance to hang out with humans for a change. Besides, I only ever talk on topics that are dear to me and that I know intimately well so I rarely feel pressure when delivering them. 2014 – 2015 was also the time frame when HTTP/2 was being finalized and the general curiosity on that new protocol version helped me find opportunities back then.
Public speaking is like most other things: surprisingly enough, practice actually makes you better at it! I still have a lot to learn and improve, but speaking many times has for example made me better at figuring out roughly how long time I need to deliver a particular talk. It has taught me to “find myself” better when presenting and be more relaxed and the real me – no need to put up a facade of some kind or pretend. People like seeing that there’s a real person there.
I’m not even getting that terribly nervous before my talks anymore. I used to really get a raised pulse for the first 45 talks or so, but by doing it over and over and over I think the practice has made me more secure and more relaxed in my attitude to the audience and the topics. I think it has made me a slightly better presenter and it certainly makes me enjoy it more.
I’m not “a good presenter”. I can deliver a talk and I can do it with dignity and I think the audience is satisfied with me in most cases, but by watching actual good presenters talk I realize that I still have a long journey ahead of me. Of course, parts of the explanation is that, to connect with the beginning of this post, I’m a developer. I don’t talk for a living and I actually very rarely practice my presentations very much because I don’t feel I can spend that time.
Some of the things that are still difficult include:
The money issue. I actually am a developer and that’s what I do for a living. Taking time off the development to prepare a presentation, travel to a distant place, sacrifice my spare time for one or more days and communicating something interesting to an audience that demands and expects it to be both good and reasonably entertaining takes time away from that development. Getting travel and accommodation compensated is awesome but unfortunately not enough. I need to insist on getting paid for this. I frequently turn down speaking opportunities when they can’t pay me for my time.
Saying no. Oh my god do I have a hard time to do this. This year, I’ve been invited to so many different conferences and the invitations keep flying in. For every single received invitation, I get this warm and comfy feeling and I feel honored and humbled by the fact that someone actually wants me to come to their conference or gathering to talk. There’s the calendar problem: I can’t be in two places at once. Then I also can’t plan events too close to each other in time to avoid them holding up “real work” too much or to become too much of a nuisance to my family. Sometimes there’s also the financial dilemma: if I can’t get compensation, it gets tricky for me to do it, no matter how good the conference seems to be and the noble cause they’re working for.
Feedback. To determine what parts of the presentation that should be improved for the next time I speak of the same or similar topic, which parts should be removed and if something should be expanded, figuring what works and what doesn’t work is vital. For most talks I’ve done, there’s been no formal way to provide or receive this feedback, and for the small percentage that had a formal feedback form or a scoring system or similar, taking care of a bunch of distributed grades (for example “your talk was graded 4.2 on a scale between 1 and 5”) and random comments – either positive or negative – is really hard… I get the best feedback from close friends who dare to tell me the truth as it is.
Conforming to silly formats. Slightly different, but some places want me to send me my slides in, either a long time before the event (I’ve had people ask me to provide way over a week(!) before), or they dictate that the slides should be sent to them using Microsoft Powerpoint, PDF or some other silly format. I want to use my own preferred tools when designing presentations as I need to be able to reuse the material for more and future presentations. Sure, I can convert to other formats but that usually ruins formatting and design. Then a lot the time and sweat I put into making a fine and good-looking presentation is more or less discarded! Fortunately, most places let me plug in my laptop and everything is fine!
As a little service to potential audience members and conference organizers, I’m listing all my upcoming speaking engagements on a dedicated page on my web site:
I try to keep that page updated to reflect current reality. It also shows that some organizers are forward-planning waaaay in advance…
Invite someone like me to talk?
Here’s some advice on how to invite a speaker (like me) with style:
Ask well in advance (more than 2-3 months preferably, probably not more than 9). When I agree to a talk, others who ask for talks in close proximity to that date will get declined. I get a surprisingly large amount of invitations for events just a month into the future or so, and it rarely works for me to get those into my calendar in that time frame.
Do not assume for-free delivery. I think it is good tone of you to address the price/charge situation, if not in the first contact email at least in the following discussion. If you cannot pay, that’s also useful information to provide early.
If the time or duration of the talk you’d like is “unusual” (ie not 30-60 minutes) do spell that out early on.
Surprisingly often I get invited to talk without a specified topic or title. The inviter then expects me to present that. Since you contact me you clearly had some kind of vision of what a talk by me would entail, it would make my life easier if that vision was conveyed as it could certainly help me produce a talk subject that will work!
What I bring
To every presentation I do, I bring my laptop. It has HDMI and USB-C ports. I also carry a HDMI-to-VGA adapter for the few installations that still use the old “projector port”. Places that need something else than those ports tend to have their own converters already since they’re then used with equipment not being fitted for their requirements.
I always bring my own clicker (the “remote” with which I can advance to next slide). I never use the laser-pointer feature, but I like being able to move around on the stage and not have to stand close to the keyboard when I present.
I never create my presentations with video or sound in them, and I don’t do presentations that need Internet access. All this to simplify and to reduce the risk of problems.
I work hard on limiting the amount of text on each slide, but I also acknowledge that if a slide set should have value after-the-fact there needs to be a certain amount. I’m a fan of revealing the text or graphics step-by-step on the slides to avoid having half the audience reading ahead on the slide and not listening.
I’ve settled on 16:9 ratio for all presentations. Luckily, the remaining 4:3 projectors are now scarce.
I always make and bring a backup of my presentations in PDF format so that basically “any” computer could display that in case of emergency. Like if my laptop dies. As mentioned above, PDF is not an ideal format, but as a backup it works.
(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.
One year ago today. On the sunny Tuesday of April 17th 2018 I visited the US embassy in Stockholm Sweden and applied for a visa. I’m still waiting for them to respond.
My days-since-my-visa-application counter page is still counting. Technically speaking, I had already applied but that was the day of the actual physical in-person interview that served as the last formal step in the application process. Most people are then getting their visa application confirmed within weeks.
Initially I emailed them a few times after that interview since the process took so long (little did I know back then), but now I haven’t done it for many months. Their last response assured me that they are “working on it”.
During this year I missed out on a Mozilla all-hands, I’ve been invited to the US several times to talk at conferences that I had to decline and a friend is getting married there this summer and I can’t go. And more.
Going forward I will miss more interesting meetings and speaking opportunities and I have many friends whom I cannot visit. This is a mild blocker to things I would want to do and it is an obstacle to my profession and career.
I guess I might get my rejection notice before my counter reaches two full years, based on stories I’ve heard from other people in similar situations such as mine. I don’t know yet what I’ll do when it eventually happens. I don’t think there are any rules that prevent me from reapplying, other than the fact that I need to pay more money and I can’t think of any particular reason why they would change their minds just by me trying again. I will probably give it a rest a while first.
I’m lucky and fortunate that people and organizations have adopted to my situation – a situation I of course I share with many others so it’s not uniquely mine – so lots of meetings and events have been held outside of the US at least partially to accommodate me. I’m most grateful for this and I understand that at times it won’t work and I then can’t attend. These days most things are at least partly accessible via video streams etc, repairing the harm a little. (And yes, this is a first-world problem and I’m fortunate that I can still travel to most other parts of the world without much trouble.)
Finally: no, I still have no clue as to why they act like this and I don’t have any hope of ever finding out.