Monthly Archives: May 2016

cURL and libcurl, Development, Open Source

On billions and “users”

At times when I’ve gone out (yes it happens), faced an audience and talked about my primary spare time project curl, I’ve said a few times in the past that we have one billion users.

Users?

many devices

OK, as this is open source I’m talking about, I can’t actually count my users and what really constitutes “a user” anyway?

If the same human runs multiple copies of curl (in different devices and applications), is that human then counted once or many times? If a single developer writes an application that uses libcurl and that application is used by millions of humans, is that one user or are they millions of curl users?

What about pure machine “users”? In the subway in one of the world’s largest cities, there’s an automated curl transfer being done for every person passing the ticket check point. Yet I don’t think we can count the passing (and unknowing) passengers as curl users…

I’ve had a few people approach me to object to my “curl has one billion users” statement. Surely not one in every seven humans on earth are writing curl command lines! We’re engineers and we’re picky with the definitions.

Because of this, I’m trying to stop talking about “number of users”. That’s not a proper metric for a project whose primary product is a library that is used by applications or within devices. I’m instead trying to assess the number of humans that are using services, tools or devices that are powered by curl. Fun challenge, right?

Who isn’t using?

a userI’ve tried to imagine of what kind of person that would not have or use any piece of hardware or applications that include curl during a typical day. I certainly can’t properly imagine all humans in this vast globe and how they all live their lives, but I quite honestly think that most internet connected humans in the world own or use something that runs my code. Especially if we include people who use online services that use curl.

curl is used in basically all modern TVs, a large percentage of all car infotainment systems, routers, printers, set top boxes, mobile phones and apps on them, tablets, video games, audio equipment, Blu-ray players, hundreds of applications, even in fridges and more. Apple alone have said they have one billion active devices, devices that use curl! Facebook uses curl extensively and they have 1.5 billion users every month. libcurl is commonly used by PHP sites and PHP empowers no less than 82% of the sites w3techs.com has figured out what they run (out of the 10 million most visited sites in the world).

There are about 3 billion internet users worldwide. I seriously believe that most of those use something that is running curl, every day. Where Internet is less used, so is of course curl.

Every human in the connected world, use something powered by curl every day

Frigging Amazing

It is an amazing feeling when I stop and really think about it. When I pause to let it sink in properly. My efforts and code have spread to almost every little corner of the connected world. What an amazing feat and of course I didn’t think it would reach even close to this level. I still have hard time fully absorbing it! What a collaborative success story, because I could never have gotten close to this without the help from others and the community we have around the project.

But it isn’t something I think about much or that make me act very different in my every day life. I still work on the bug reports we get, respond to emails and polish off rough corners here and there as we go forward and keep releasing new curl releases every 8 weeks. Like we’ve done for years. Like I expect us and me to continue doing for the foreseeable future.

It is also a bit scary at times to think of the massive impact it could have if or when a really terrible security flaw is discovered in curl. We’ve had our fair share of security vulnerabilities so far through our history, but we’ve so far been spared from the really terrible ones.

So I’m rich, right?

coins

If I ever start to describe something like this to “ordinary people” (and trust me, I only very rarely try that), questions about money is never far away. Like how come I give it away free and the inevitable “what if everyone using curl would’ve paid you just a cent, then…“.

I’m sure I don’t need to tell you this, but I’ll do it anyway: I give away curl for free as open source and that is a primary reason why it has reached to the point where it is today. It has made people want to help out and bring the features that made it attractive and it has made companies willing to use and trust it. Hadn’t it been open source, it would’ve died off already in the 90s. Forgotten and ignored. And someone else would’ve made the open source version and instead filled the void a curlless world would produce.

cURL and libcurl, Mozilla, Network, Open Source, Web

everybody runs this code all the time

I was invited to talk about curl at the recent FOSS North conference in Gothenburg on May 26th. It was the first time the conference ran, but I think it went smooth and the ~110 visitors seemed to have a good time. It was a single track and there was a fairly good and interesting mix of talkers and subjects I think. They’re already planning to make it return again in spring 2017, so if you’re into FOSS and you’re in the Nordic region, consider this event next year…

I took on the subject of talking about my hacker ring^W^Wcurl project insights. Here’s my slide set:

At the event I sat down and had a chat with Simon Campanello, a reporter at IDG Techworld here in Sweden who subsequently posted this article about curl (in Swedish) and how our code has ended up getting used so widely.

photo of me from the Techworld article

cURL and libcurl, Development

curl user poll 2016

It is time for our annual survey on how you use curl and libcurl. Your chance to tell us how you think we’ve done and what we should do next. The survey will close on midnight (central European time) May 27th, 2016.

If you use curl or libcurl from time to time, please consider helping us out with providing your feedback and opinions on a few things:

http://goo.gl/forms/e4CoSDEKde

It’ll take you a couple of minutes and it’ll help us a lot when making decisions going forward. Thanks a lot!

The poll is hosted by Google and that short link above will take you to:

https://docs.google.com/forms/d/1JftlLZoOZLHRZ_UqigzUDD0AKrTBZqPMpnyOdF2UDic/viewform

cURL and libcurl, Mozilla, Network, Web

My URL isn’t your URL

24 Comments

URLs

When I started the precursor to the curl project, httpget, back in 1996, I wrote my first URL parser. Back then, the universal address was still called URL: Uniform Resource Locators. That spec was published by the IETF in 1994. The term “URL” was then used as source for inspiration when naming the tool and project curl.

The term URL was later effectively changed to become URI, Uniform Resource Identifiers (published in 2005) but the basic point remained: a syntax for a string to specify a resource online and which protocol to use to get it. We claim curl accepts “URLs” as defined by this spec, the RFC 3986. I’ll explain below why it isn’t strictly true.

There was also a companion RFC posted for IRI: Internationalized Resource Identifiers. They are basically URIs but allowing non-ascii characters to be used.

The WHATWG consortium later produced their own URL spec, basically mixing formats and ideas from URIs and IRIs with a (not surprisingly) strong focus on browsers. One of their expressed goals is to “Align RFC 3986 and RFC 3987 with contemporary implementations and obsolete them in the process“. They want to go back and use the term “URL” as they rightfully state, the terms URI and IRI are just confusing and no humans ever really understood them (or often even knew they exist).

The WHATWG spec follows the good old browser mantra of being very liberal in what it accepts and trying to guess what the users mean and bending backwards trying to fulfill. (Even though we all know by now that Postel’s Law is the wrong way to go about this.) It means it’ll handle too many slashes, embedded white space as well as non-ASCII characters.

From my point of view, the spec is also very hard to read and follow due to it not describing the syntax or format very much but focuses far too much on mandating a parsing algorithm. To test my claim: figure out what their spec says about a trailing dot after the host name in a URL.

On top of all these standards and specs, browsers offer an “address bar” (a piece of UI that often goes under other names) that allows users to enter all sorts of fun strings and they get converted over to a URL. If you enter “http://localhost/%41” in the address bar, it’ll convert the percent encoded part to an ‘A’ there for you (since 41 in hex is a capital A in ASCII) but if you type “http://localhost/A A” it’ll actually send “/A%20A” (with a percent encoded space) in the outgoing HTTP GET request. I’m mentioning this since people will often think of what you can enter there as a “URL”.

The above is basically my (skewed) perspective of what specs and standards we have so far to work with. Now we add reality and let’s take a look at what sort of problems we get when my URL isn’t your URL.

So what  is a URL?

Or more specifically, how do we write them. What syntax do we use.

I think one of the biggest mistakes the WHATWG spec has made (and why you will find me argue against their spec in its current form with fierce conviction that they are wrong), is that they seem to believe that URLs are theirs to define and work with and they limit their view of URLs for browsers, HTML and their address bars. Sure, they are the big companies behind the browsers almost everyone uses and URLs are widely used by browsers, but URLs are still much bigger than so.

The WHATWG view of a URL is not widely adopted outside of browsers.

colon-slash-slash

If we ask users, ordinary people with no particular protocol or web expertise, what a URL is what would they answer? While it was probably more notable years ago when the browsers displayed it more prominently, the :// (colon-slash-slash) sequence will be high on the list. Seeing that marks the string as a URL.

Heck, going beyond users, there are email clients, terminal emulators, text editors, perl scripts and a bazillion other things out there in the world already that detects URLs for us and allows operations on that. It could be to open that URL in a browser, to convert it to a clickable link in generated HTML and more. A vast amount of said scripts and programs will use the colon-slash-slash sequence as a trigger.

The WHATWG spec says it has to be one slash and that a parser must accept an indefinite amount of slashes. “http:/example.com” and “http:////////////////////////////////////example.com” are both equally fine. RFC 3986 and many others would disagree. Heck, most people I’ve confronted the last few days, even people working with the web, seem to say, think and believe that a URL has two slashes. Just look closer at the google picture search screen shot at the top of this article, which shows the top images for “URL” google gave me.

We just know a URL has two slashes there (and yeah, file: URLs most have three but lets ignore that for now). Not one. Not three. Two. But the WHATWG doesn’t agree.

“Is there really any reason for accepting more than two slashes for non-file: URLs?” (my annoyed question to the WHATWG)

“The fact that all browsers do.”

The spec says so because browsers have implemented the spec.

No better explanation has been provided, not even after I pointed out that the statement is wrong and far from all browsers do. You may find reading that thread educational.

In the curl project, we’ve just recently started debating how to deal with “URLs” having another amount of slashes than two because it turns out there are servers sending back such URLs in Location: headers, and some browsers are happy to oblige. curl is not and neither is a lot of other libraries and command line tools. Who do we stand up for?

Spaces

A space character (the ASCII code 32, 0x20 in hex) cannot be part of a URL. If you want it sent, you percent encode it like you do with any other illegal character you want to be part of the URL. Percent encoding is the byte value in hexadecimal with a percent sign in front of it. %20 thus means space. It also means that a parser that for example scans for URLs in a text knows that it reaches the end of the URL when the parser encounters a character that isn’t allowed. Like space.

Browsers typically show the address in their address bars with all %20 instances converted to space for appearance. If you copy the address there into your clipboard and then paste it again in your text editor you still normally get the spaces as %20 like you want them.

I’m not sure if that is the reason, but browsers also accept spaces as part of URLs when for example receiving a redirect in a HTTP response. That’s passed from a server to a client using a Location: header with the URL in it. The browsers happily allow spaces in that URL, encode them as %20 and send out the next request. This forced curl into accepting spaces in redirected “URLs”.

Non-ASCII

Making URLs support non-ASCII languages is of course important, especially for non-western societies and I’ve understood that the IRI spec was never good enough. I personally am far from an expert on these internationalization (i18n) issues so I just go by what I’ve heard from others. But of course users of non-latin alphabets and typing systems need to be able to write their “internet addresses” to resources and use as links as well.

In an ideal world, we would have the i18n version shown to users and there would be the encoded ASCII based version below, to get sent over the wire.

For international domain names, the name gets converted over to “punycode” so that it can be resolved using the normal system name resolvers that know nothing about non-ascii names. URIs have no IDN names, IRIs do and WHATWG URLs do. curl supports IDN host names.

WHATWG states that URLs are specified as UTF-8 while URIs are just ASCII. curl gets confused by non-ASCII letters in the path part but percent encodes such byte values in the outgoing requests – which causes “interesting” side-effects when the non-ASCII characters are provided in other encodings than UTF-8 which for example is standard on Windows…

Similar to what I’ve written above, this leads to servers passing back non-ASCII byte codes in HTTP headers that browsers gladly accept, and non-browsers need to deal with…

No URL standard

I’ve not tried to write a conclusive list of problems or differences, just a bunch of things I’ve fallen over recently. A “URL” given in one place is certainly not certain to be accepted or understood as a “URL” in another place.

Not even curl follows any published spec very closely these days, as we’re slowly digressing for the sake of “web compatibility”.

There’s no unified URL standard and there’s no work in progress towards that. I don’t count WHATWG’s spec as a real effort either, as it is written by a closed group with no real attempts to get the wider community involved.

My affiliation

I’m employed by Mozilla and Mozilla is a member of WHATWG and I have colleagues working on the WHATWG URL spec and other work items of theirs but it makes absolutely no difference to what I’ve written here. I also participate in the IETF and I consider myself friends with authors of RFC 1738, RFC 3986 and others but that doesn’t matter here either. My opinions are my own and this is my personal blog.

cURL and libcurl

A book status update

6 Comments

— How’s Daniel’s curl book going?

I can hear absolutely nobody asking. I’ll just go ahead and tell you anyway since I had a plan to get a first version “done” by “the summer” (of 2016). I’m not sure I believe in that time frame anymore.

everything-curl-coverI’m now north of 40,000 words with a bunch of new chapters and sections added recently and I’m now generating an index that looks okay. The PDF version is exactly 200 pages now.

The index part is mainly interesting since the platform I use to write the book on, gitbook.com, doesn’t offer any index functionality of its own so I  had to hack one up and add. That’s just one additional beauty of having the book made entirely in markdown.

Based on what I’ve written so far and know I still have outstanding, I am about 70% done, indicating there are about 17,000 words left for me. At this particular point in time. The words numbers tend to grow over time as the more I write (and the completion level is sort of stuck), the more I think of new sections that I should add and haven’t yet written…

On this page you can get the latest book stats, right off the git repo.

c-ares, cURL and libcurl, Open Source

No more heartbleeds please

caution-quarantine-areaAs a reaction to the whole Heartbleed thing two years ago, The Linux Foundation started its Core Infrastructure Initiative (CII for short) with the intention to help track down well used but still poorly maintained projects or at least detect which projects that might need help. Where the next Heartbleed might occur.

A bunch of companies putting in money to improve projects that need help. Sounds almost like a fairy tale to me!

Census

In order to identify which projects to help, they run their Census Project: “The Census represents CII’s current view of the open source ecosystem and which projects are at risk.”

The Census automatically extracts a lot of different meta data about open source projects in order to deduce a “Risk Index” for each project. Once you’ve assembled such a great data trove for a busload of projects, you can sort them all based on that risk index number and then you basically end up with a list of projects in a priority order that you can go through and throw code at. Or however they deem the help should be offered.

Which projects will fail?

The old blog post How you know your Free or Open Source Software Project is doomed to FAIL provides such a way, but it isn’t that easy to follow programmatically. The foundation has its own 88 page white paper detailing its methods and algorithm.

Risk Index

  • A project without a web site gets a point
  • If the project has had four or more CVEs (publicly disclosed security vulnerabilities) since 2010, it receives 3 points and if fewer than four there’s a diminishing scale.
  • The number of contributors the last 12 months is a rather heavy factor, which thus could make the index grow old fairly quick. 3 contributors still give 4 points.
  • Popular packages based on Debian’s popcon get points.
  • If the project’s main language is C or C++, it gets two points.
  • Network “exposed” projects get points.
  • some additional details like dependencies and how many outstanding patches not accepted upstream that exist

All combined, this grades projects’ “risk” between 0 and 15.

Not high enough resolution

Assuming that a larger number of CVEs means anything bad is just wrong. Even the most careful and active projects can potentially have large amounts of CVEs. It means they disclose what they find and that people are actually reviewing code, finding problems and are reporting problems. All good things.

Sure, security problems are not good but the absence of CVEs in a project doesn’t say that the project is one bit more secure. It could just mean that nobody ever looked closely enough or that the project doesn’t deal with responsible disclosure of the problems.

When I look through the projects they have right now, I get the feeling the resolution (0-15) is too low and they’ve shied away from more aggressively handing out penalty based on factors we all recognize in abandoned/dead projects (some of which are decently specified in Tom Calloway’s blog post mentioned above).

The result being that the projects get a score that is mostly based on what kind of project it is.

But this said, they have several improvements to their algorithm already suggested in their issue tracker. I firmly believe this will improve over time.

The riskiest ?

The top three projects, the only ones that scores 13 right now are expat, procmail and unzip. All of them really small projects (source code wise) that have been around since a very long time.

curl, being the project I of course look out for, scores a 9: many CVEs (3), written in C (2), network exposure (2), 5+ apps depend on it (2). Seriously, based on these factors, how would you say the project is situated?

In the sorted list with a little over 400 projects, curl is rated #73 (at the time of this writing at least). Just after reportbug but before libattr1. [curl summary – which is mentioning a very old curl release]

But the list of projects mysteriously lack many projects. Like I couldn’t find neither c-ares nor libssh2. They may not be super big, but they’re used by a bunch of smaller and bigger projects at least, including curl itself.

The full list of projects, their meta-data and scores are hosted in their repository on github.

Benefits for projects near me

I can see how projects in my own backyard have gotten some good out of this effort.

I’ve received some really great bug reports and gotten handed security problems in curl by an individual who did his digging funded by this project.

I’ve seen how the foundation sponsored a test suite for c-ares since the project lacked one. Now it doesn’t anymore!

Badges!

In addition to that, the Linux Foundation has also just launched the CII Best Practices Badge Program, to allow open source projects to fill in a bunch of questions and if meeting enough requirements, they will get a “badge” to boast to the world as a “well run project” that meets current open source project best practices.

I’ve joined their mailing list and provided some of my thoughts on the current set of questions, as I consider a few of them to be, well, lets call them “less than optimal”. But then again, which project doesn’t have bugs? We can fix them!

curl is just now marked as “100% compliance” with all the best practices listed. I hope to be able to keep it like that even with future and more best practices added.