Daniel’s weekly report

March 25, 2022

Happened this week


On March 20, 2022 the curl project turned 24 years old. On that birthday, curl was a little over 2,000 lines of code and the command line tool (there was no library yet) featured 24 command line options.

I figured I would not write a humongous birthday blog post this year. I save that for next year.

Merged headers API

After having spent just 9 calendar days since I wrote the first line of code, I merged the headers API pull-request commits into curl’s master branch, to be part of the next release. The API is still marked experimental so it will be disabled by default. I still hope a few will enable it, try it and tell me what they think!

curl -w headers

As part of the headers API PR, I added header-picking support to curl’s -w option. It provides two new ways for the tool to extract contents of HTTP headers. I think especially the %{header_json} thing has a chance of hitting it with some users as it will make curl a whole lot better to integrate into a JSON speaking world.

A ghost CVE

I spent some time early this week chasing and investigating the details around an Apple ghost CVE. I never got any explanation from Apple.

curl presentation

I did an online presentation about curl for Fyndiq I called Let me tell you about curl.

libcurl on WinCE

I had a productive meeting with a potential new customer. I will help them get libcurl with wolfSSL to build and run proper on an old WinCE on ARM platform…

Podcast published

The Swedish-speaking podcast Trevlig Mjukvara published the episode I was a guest at and recorded last week.

Hyper progress

After Sean’s call for help to work on the hyper integration that I mentioned last week, there has been more hyper related activity in several areas. We are now down to a mere 17 disabled test cases in hyper builds, and there are several open issues for remaining work. (Unfortunately this was partly done by adding “no support for clear-text upgrade to HTTP/2” as a known restriction.)


I’m running a Twitter poll on how to spell backend, back-end or back end as a follow-up from discussions on how we should write the word in everything curl.

Getting started with libcurl video

The video from my webinar from last week went up and I update my blog post about it to also feature the video now.

Blog posts

Coming up

  • curl enters feature-freeze on Wednesday March 30
  • European daylight saving time switch on Sunday
  • work with two potential security vulnerabilities
  • libcurl on WinCE


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Daniel’s weekly report

March 18, 2022

Happened this week


I cheated a little and started working on implementing the new proposed header API for libcurl already last weekend. I’ve then continued and spent a majority of my curl time this week on it.

While we had a pretty good proposal already before I wrote any code for it, it was of course not good enough once I started to actually get into the specifics and details around how it should work and how to provide all the headers in the most flexible and reliable way for applications using libcurl. I think I refined the API at least 4 or 5 times during the week, mostly because working on the code made me think harder about the problems but also because of good feedback from contributors when I got back with my new lessons learned. The get headers v2 wiki page has been updated accordingly to make it easier for outsiders to see the API. (I will remove that wiki page once the man pages get merged into git so that we rather have the API docs in a single place.)

This API work is almost complete and still lives in PR 8593.

cmdline header options

While working on the header API I wanted to add another test case and I figured it would be easier to do that if I first made the command line tool able to output the headers. Using the tool in test cases is often easier and quicker than testing libcurl functions.

This was also a great first use case for the new header API. It took me less than an hour of work to make a first shot at providing headers for command line users with two new extensions to the -w option. Then it took me a little longer to figure out JSON syntax and how to format the output properly.

Right now, this is how they work:

Individual headers

$ curl -w '%header{date}\n' -o savefile curl.se
Thu, 17 Mar 2022 16:59:24 GMT

All headers output as JSON

$ curl -sw '%{header_json}\n' -o savefile curl.se | jq
  "Date": [
    "Tue, 09 Nov 2010 14:49:00 GMT"
  "Server": [
  "Last-Modified": [
    "Tue, 13 Jun 2000 12:10:00 GMT"
  "ETag": [
  "Accept-Ranges": [
  "Set-Cookie": [
    "firstcookie=want; path=/",
    "2cookie=want; path=/",
    "cookie3=want; path=/"
  "Content-Length": [
  "Connection": [


My blog post about curl-minimal made it into a quote on lwn.net:

It is really hard for packagers to know what curl features that are used and not used. There simply is no way to find out, besides shipping a version and listening to the screams of users in pain when things break. It will also force them into line-drawing decisions such as “only N users seem to use feature Z so let’s keep that in the full package” and figuring out the N number is a fuzzy estimate at best.

Mystery CVE

Apple posted a macOS security update in which they refer to curl CVE that doesn’t exist: CVE-2022-22623. Several sites have already speculated wildly what this flaw is. I’m in touch with the mother-ship now to figure out what they actually meant.

24,000 stars

Just days before curl’s 24th birthday we reached 24,000 stars on the curl GitHub repository. Seems fitting.


I ran a webinar called getting started with libcurl on Thursday. The video recording is not yet available.

Sean’s hyper blog post

Sean McArthur blogged Help stabilize hyper in curl - about how help out to get the final tests in curl still don’t worth with hyper fixed.

Podcast recording

I recorded a podcast episode with the awesome hosts of the podcast Trevlig mjukvara - in Swedish. Supposed to be published soon.

Podcast publication

Cybersecurity: Amplified and Intensified #57 was published, where I guested the podcast and talked curl, money, open source and supply chain.

Blog posts

Coming up

  • curl’s 24th birthday
  • landing PR 8593?


Comment here

March 11, 2022

Happened this week


I didn’t do any weekly report last week because I was on vacation. I went up north a bit in Sweden (~500km from my house) and enjoyed downhill skiing with the family for a few days. Snow, sun and lots of time outdoors. Good times.


Due to the above mentioned ski-trip, I delayed the 7.82.0 release three days and instead did it when I got back home. A curl release on a Saturday probably hasn’t happen in over decade or so.

We have had a few regressions reported already, but none of them have been deemed important enough to warrant a panic follow-up patch release. On March 10 we opened the feature window and we have already merged news that will make the next version to become 7.83.0. I intend to do separate blog posts for each new “thing” introduced…


I brought up the question if BearSSL is still a library to recommend since they haven’t had a commit in over a year and is still lacking major features such as TLS 1.3.

I didn’t get a whole lot of feedback, although the author seems to think it is fine. I’m not convinced, but I might leave it for now and give it another deeper look in six months or so.

Two-letter options

After another Twitter discussion I brought a crazy idea of how curl could introduce two-letter options to the curl-users mailing list. Consider this mostly food for thoughts and a way to bounce around some ideas on the topic. I don’t think anyone thinks we should run ahead and implement it exactly as stated there.

Server hiccup

Our main server which runs the curl web site, mailing lists, DNS server and a lot of other things ran into some minor problems this week (Tuesday around 15:30 UTC) which a few people noticed when some web pages started to not show correctly on curl.se and daniel.haxx.se. The problems were mostly hidden from the world thanks to the sites being fronted by Fastly, and after a quick “rescue operation” from Haxx colleagues and myself, we had it up again in no time.


Over on lwn.net, an article brought my attention (still paywalled at the time of this writing) to a Fedora discussion where they are consider shipping a stripped down “curl-minimal” package by default, to reduce the “security surface”. There are some interesting comments and details in that discussion.

I’ll keep my opinions about the main topic to myself until asked.

curl up 2022

I started the discussion about what and how to make curl up 2022 happen.

Blog posts

Coming up

  • get started on implementing headers API v2 proposal
  • work with PR authors and merge some pending ones


Comment here

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