Tag Archives: HTTP/3

curl 7.66.0 – the parallel HTTP/3 future is here

I personally have not done this many commits to curl in a single month (August 2019) for over three years. This increased activity is of course primarily due to the merge of and work with the HTTP/3 code. And yet, that is still only in its infancy…

Download curl here.

Numbers

the 185th release
6 changes
54 days (total: 7,845)

81 bug fixes (total: 5,347)
214 commits (total: 24,719)
1 new public libcurl function (total: 81)
1 new curl_easy_setopt() option (total: 269)

4 new curl command line option (total: 225)
46 contributors, 23 new (total: 2,014)
29 authors, 14 new (total: 718)
2 security fixes (total: 92)
450 USD paid in Bug Bounties

Two security advisories

TFTP small blocksize heap buffer overflow

(CVE-2019-5482) If you told curl to do TFTP transfers using a smaller than default “blocksize” (default being 512), curl could overflow a heap buffer used for the protocol exchange. Rewarded 250 USD from the curl bug bounty.

FTP-KRB double-free

(CVE-2019-5481) If you used FTP-kerberos with curl and the server maliciously or mistakenly responded with a overly large encrypted block, curl could end up doing a double-free in that exit path. This would happen on applications where allocating a large 32 bit max value (up to 4GB) is a problem. Rewarded 200 USD from the curl bug bounty.

Changes

The new features in 7.66.0 are…

HTTP/3

This experimental feature is disabled by default but can be enabled and works (by some definition of “works”). Daniel went through “HTTP/3 in curl” in this video from a few weeks ago:

Parallel transfers

You can now do parallel transfers with the curl tool’s new -Z / –parallel option. This is a huge change that might change a lot of use cases going forward!

Retry-after

There’s a standard HTTP header that some servers return when they can’t or won’t respond right now, which indicates after how many seconds or at what point in the future the request might be fulfilled. libcurl can now return that number easily and curl’s –retry option makes use of it (if present).

curl_multi_poll

curl_multi_poll is a new function offered that is very similar to curl_multi_wait, but with one major benefit: it solves the problem for applications of what to do for the occasions when libcurl has no file descriptor at all to wait for. That has been a long-standing and perhaps far too little known issue.

SASL authzid

When using SASL authentication, curl and libcurl now can provide the authzid field as well!

Bug-fixes

Some interesting bug-fixes included in this release..

.netrc and .curlrc on Windows

Starting now, curl and libcurl will check for and use the dot-prefixed versions of these files even on Windows and only fall back and check for and use the underscore-prefixed versions for compatibility if the dotted one doesn’t exist. This unifies curl’s behavior across platforms.

asyn-thread: create a socketpair to wait on

With this perhaps innocuous-sounding change, libcurl on Linux and other Unix systems will now provide a file descriptor for the application to wait on while name resolving in a background thread. This lets applications know better when to call libcurl again and avoids having to just blindly wait and retry. A performance gain.

Credentials in URL when using HTTP proxy

We found and fixed a regression that made curl not use credentials properly from the URL when doing multi stage authentication (like HTTP Digest) with a proxy.

Move code into vssh for SSH backends

A mostly janitor-style fix that also now abstracted away more SSH-using code to not know what particular SSH backend that is being used while at the same time making it easier to write and provide new SSH backends in the future. I’m personally working a little slowly on one, to be talked about at a later point.

Disable HTTP/0.9 by default

If you want libcurl to accept and deliver HTTP/0.9 responses to your application, you need to tell it to do that. Starting in this version, curl will consider those invalid HTTP responses by default.

alt-svc improvements

We introduced alt-svc support a while ago but as it is marked experimental and nobody felt a strong need to use it, it clearly hasn’t been used or tested much in real life. When we’ve worked on using alt-svc to bootstrap into HTTP/3 we found and fixed a whole range of little issues with the alt-svc support and it is now in a much better shape. However, it is still marked experimental.

IPv6 addresses in URLs

It was reported that the URL parser would accept malformatted IPv6 addresses that subsequently and counter-intuitively would get resolved as a host name internally! An example URL would be “https://[ab.de]/’ – where all the letters and symbols within the brackets are individually allowed components of a IPv6 numerical address but it still isn’t a valid IPv6 syntax and instead is a legitimate and valid host name.

Going forward!

We recently ran a poll among users of what we feel are the more important things to work on, and with that the rough roadmap has been updated. Those are things I want to work on next but of course I won’t guarantee anything and I will greatly appreciate all help and assistance that I can get. And sure, we can and will work on other things too!

First HTTP/3 with curl

In the afternoon of August 5 2019, I successfully made curl request a document over HTTP/3, retrieve it and then exit cleanly again.

(It got a 404 response code, two HTTP headers and 10 bytes of content so the actual response was certainly less thrilling to me than the fact that it actually delivered that response over HTTP version 3 over QUIC.)

The components necessary for this to work, if you want to play along at home, are reasonably up-to-date git clones of curl itself and the HTTP/3 library called quiche (and of course quiche’s dependencies too, like boringssl), then apply pull-request 4193 (build everything accordingly) and run a command line like:

curl --http3-direct https://quic.tech:8443

The host name used here (“quic.tech”) is a server run by friends at Cloudflare and it is there for testing and interop purposes and at the time of this test it ran QUIC draft-22 and HTTP/3.

The command line option --http3-direct tells curl to attempt HTTP/3 immediately, which includes using QUIC instead of TCP to the host name and port number – by default you should of course expect a HTTPS:// URL to use TCP + TLS.

The official way to bootstrap into HTTP/3 from HTTP/1 or HTTP/2 is via the server announcing it’s ability to speak HTTP/3 by returning an Alt-Svc: header saying so. curl supports this method as well, it just needs it to be explicitly enabled at build-time since that also is still an experimental feature.

To use alt-svc instead, you do it like this:

curl --alt-svc altcache https://quic.tech:8443

The alt-svc method won’t “take” on the first shot though since it needs to first connect over HTTP/2 (or HTTP/1) to get the alt-svc header and store that information in the “altcache” file, but if you then invoke it again and use the same alt-svc cache curl will know to use HTTP/3 then!

Early days

Be aware that I just made this tiny GET request work. The code is not cleaned up, there are gaps in functionality, we’re missing error checks, we don’t have tests and chances are the internals will change quite a lot going forward as we polish this.

You’re of course still more than welcome to join in, play with it, report bugs or submit pull requests! If you help out, we can make curl’s HTTP/3 support better and getting there sooner than otherwise.

QUIC and TLS backends

curl currently supports two different QUIC/HTTP3 backends, ngtcp2 and quiche. Only the latter currently works this good though. I hope we can get up to speed with the ngtcp2 one too soon.

quiche uses and requires boringssl to be used while ngtcp2 is TLS library independent and will allow us to support QUIC and HTTP/3 with more TLS libraries going forward. Unfortunately it also makes it more complicated to use…

The official OpenSSL doesn’t offer APIs for QUIC. QUIC uses TLS 1.3 but in a way it was never used before when done over TCP so basically all TLS libraries have had to add APIs and do some adjustments to work for QUIC. The ngtcp2 team offers a patched version of OpenSSL that offers such an API so that OpenSSL be used.

Draft what?

Neither the QUIC nor the HTTP/3 protocols are entirely done and ready yet. We’re using the protocols as they are defined in the 22nd version of the protocol documents. They will probably change a little more before they get carved in stone and become the final RFC that they are on their way to.

The libcurl API so far

The command line options mentioned above of course have their corresponding options for libcurl using apps as well.

Set the right bit with CURLOPT_H3 to get direct connect with QUIC and control how to do alt-svc using libcurl with CURLOPT_ALTSVC and CURLOPT_ALTSVC_CTRL.

All of these marked EXPERIMENTAL still, so they might still change somewhat before they become stabilized.

Update

Starting on August 8, the option is just --http3 and you ask libcurl to use HTTP/3 directly with CURLOPT_HTTP_VERSION.

Workshop Season 4 Finale

The 2019 HTTP Workshop ended today. In total over the years, we have now done 12 workshop days up to now. This day was not a full day and we spent it on only two major topics that both triggered long discussions involving large parts of the room.

Cookies

Mike West kicked off the morning with his cookies are bad presentation.

One out of every thousand cookie header values is 10K or larger in size and even at the 50% percentile, the size is 480 bytes. They’re a disaster on so many levels. The additional features that have been added during the last decade are still mostly unused. Mike suggests that maybe the only way forward is to introduce a replacement that avoids the issues, and over longer remove cookies from the web: HTTP state tokens.

A lot of people in the room had opinions and thoughts on this. I don’t think people in general have a strong love for cookies and the way they currently work, but the how-to-replace-them question still triggered lots of concerns about issues from routing performance on the server side to the changed nature of the mechanisms that won’t encourage web developers to move over. Just adding a new mechanism without seeing the old one actually getting removed might not be a win.

We should possibly “worsen” the cookie experience over time to encourage switch over. To cap allowed sizes, limit use to only over HTTPS, reduce lifetimes etc, but even just that will take effort and require that the primary cookie consumers (browsers) have a strong will to hurt some amount of existing users/sites.

(Related: Mike is also one of the authors of the RFC6265bis draft in progress – a future refreshed cookie spec.)

HTTP/3

Mike Bishop did an excellent presentation of HTTP/3 for HTTP people that possibly haven’t kept up fully with the developments in the QUIC working group. From a plain HTTP view, HTTP/3 is very similar feature-wise to HTTP/2 but of course sent over a completely different transport layer. (The HTTP/3 draft.)

Most of the questions and discussions that followed were rather related to the transport, to QUIC. Its encryption, it being UDP, DOS prevention, it being “CPU hungry” etc. Deploying HTTP/3 might be a challenge for successful client side implementation, but that’s just nothing compared the totally new thing that will be necessary server-side. Web developers should largely not even have to care…

One tidbit that was mentioned is that in current Firefox telemetry, it shows about 0.84% of all requests negotiates TLS 1.3 early data (with about 12.9% using TLS 1.3)

Thought-worthy quote of the day comes from Willy: “everything is a buffer”

Future Workshops

There’s no next workshop planned but there might still very well be another one arranged in the future. The most suitable interval for this series isn’t really determined and there might be reasons to try tweaking the format to maybe change who will attend etc.

The fact that almost half the attendees this time were newcomers was certainly good for the community but that not a single attendee traveled here from Asia was less good.

Thanks

Thanks to the organizers, the program committee who set this up so nicely and the awesome sponsors!

The HTTP Workshop 2019 begins

The forth season of my favorite HTTP series is back! The HTTP Workshop skipped over last year but is back now with a three day event organized by the very best: Mark, Martin, Julian and Roy. This time we’re in Amsterdam, the Netherlands.

35 persons from all over the world walked in the room and sat down around the O-shaped table setup. Lots of known faces and representatives from a large variety of HTTP implementations, client-side or server-side – but happily enough also a few new friends that attend their first HTTP Workshop here. The companies with the most employees present in the room include Apple, Facebook, Mozilla, Fastly, Cloudflare and Google – having three or four each in the room.

Patrick Mcmanus started off the morning with his presentation on HTTP conventional wisdoms trying to identify what have turned out as successes or not in HTTP land in recent times. It triggered a few discussions on the specific points and how to judge them. I believe the general consensus ended up mostly agreeing with the slides. The topic of unshipping HTTP/0.9 support came up but is said to not be possible due to its existing use. As a bonus, Anne van Kesteren posted a new bug on Firefox to remove it.

Mark Nottingham continued and did a brief presentation about the recent discussions in HTTPbis sessions during the IETF meetings in Prague last week.

Martin Thomson did a presentation about HTTP authority. Basically how a client decides where and who to ask for a resource identified by a URI. This triggered an intense discussion that involved a lot of UI and UX but also trust, certificates and subjectAltNames, DNS and various secure DNS efforts, connection coalescing, DNSSEC, DANE, ORIGIN frame, alternative certificates and more.

Mike West explained for the room about the concept for Signed Exchanges that Chrome now supports. A way for server A to host contents for server B and yet have the client able to verify that it is fine.

Tommy Pauly then talked to his slides with the title of Website Fingerprinting. He covered different areas of a browser’s activities that are current possible to monitor and use for fingerprinting and what counter-measures that exist to work against furthering that development. By looking at the full activity, including TCP flows and IP addresses even lots of our encrypted connections still allow for pretty accurate and extensive “Page Load Fingerprinting”. We need to be aware and the discussion went on discussing what can or should be done to help out.

The meeting is going on somewhere behind that red door.

Lucas Pardue discussed and showed how we can do TLS interception with Wireshark (since the release of version 3) of Firefox, Chrome or curl and in the end make sure that the resulting PCAP file can get the necessary key bundled in the same file. This is really convenient when you want to send that PCAP over to your protocol debugging friends.

Roberto Peon presented his new idea for “Generic overlay networks”, a suggested way for clients to get resources from one out of several alternatives. A neighboring idea to Signed Exchanges, but still different. There was an interested to further and deepen this discussion and Roberto ended up saying he’d at write up a draft for it.

Max Hils talked about Intercepting QUIC and how the ability to do this kind of thing is very useful in many situations. During development, for debugging and for checking what potentially bad stuff applications are actually doing on your own devices. Intercepting QUIC and HTTP/3 can thus also be valuable but at least for now presents some challenges. (Max also happened to mention that the project he works on, mitmproxy, has more stars on github than curl, but I’ll just let it slide…)

Poul-Henning Kamp showed us vtest – a tool and framework for testing HTTP implementations that both Varnish and HAproxy are now using. Massaged the right way, this could develop into a generic HTTP test/conformance tool that could be valuable for and appreciated by even more users going forward.

Asbjørn Ulsberg showed us several current frameworks that are doing GET, POST or SEARCH with request bodies and discussed how this works with caching and proposed that SEARCH should be defined as cacheable. The room mostly acknowledged the problem – that has been discussed before and that probably the time is ripe to finally do something about it. Lots of users are already doing similar things and cached POST contents is in use, just not defined generically. SEARCH is a already registered method but could get polished to work for this. It was also suggested that possibly POST could be modified to also allow for caching in an opt-in way and Mark volunteered to author a first draft elaborating how it could work.

Indonesian and Tibetan food for dinner rounded off a fully packed day.

Thanks Cory Benfield for sharing your notes from the day, helping me get the details straight!

Diversity

We’re a very homogeneous group of humans. Most of us are old white men, basically all clones and practically indistinguishable from each other. This is not diverse enough!

A big thank you to the HTTP Workshop 2019 sponsors!


The future of HTTP Symposium

This year’s version of curl up started a little differently: With an afternoon of HTTP presentations. The event took place the same week the IETF meeting has just ended here in Prague so we got the opportunity to invite people who possibly otherwise wouldn’t have been here… Of course this was only possible thanks to our awesome sponsors, visible in the image above!

Lukáš Linhart from Apiary started out with “Web APIs: The Past, The Present and The Future”. A journey trough XML-RPC, SOAP and more. One final conclusion might be that we’re not quite done yet…

James Fuller from MarkLogic talked about “The Defenestration of Hypermedia in HTTP”. How HTTP web technologies have changed over time while the HTTP paradigms have survived since a very long time.

I talked about DNS-over-HTTPS. A presentation similar to the one I did before at FOSDEM, but in a shorter time so I had to talk a little faster!

Mike Bishop from Akamai (editor of the HTTP/3 spec and a long time participant in the HTTPbis work) talked about “The evolution of HTTP (from HTTP/1 to HTTP/3)” from HTTP/0.9 to HTTP/3 and beyond.

Robin Marx then rounded off the series of presentations with his tongue in cheek “HTTP/3 (QUIC): too big to fail?!” where we provided a long list of challenges for QUIC and HTTP/3 to get deployed and become successful.

We ended this afternoon session with a casual Q&A session with all the presenters discussing various aspects of HTTP, the web, REST, APIs and the benefits and deployment challenges of QUIC.

I think most of us learned things this afternoon and we could leave the very elegant Charles University room enriched and with more food for thoughts about these technologies.

We ended the evening with snacks and drinks kindly provided by Apiary.

(This event was not streamed and not recorded on video, you had to be there in person to enjoy it.)


alt-svc in curl

The RFC 7838 was published already in April 2016. It describes the new HTTP header Alt-Svc, or as the title of the document says HTTP Alternative Services.

HTTP Alternative Services

An alternative service in HTTP lingo is a quite simply another server instance that can provide the same service and act as the same origin as the original one. The alternative service can run on another port, on another host name, on another IP address, or over another HTTP version.

An HTTP server can inform a client about the existence of such alternatives by returning this Alt-Svc header. The header, which has an expiry time, tells the client that there’s an optional alternative to this service that is hosted on that host name, that port number using that protocol. If that client is a browser, it can connect to the alternative in the background and if that works out fine, continue to use that host for the rest of the time that alternative is said to work.

In reality, this header becomes a little similar to the DNS records SRV or URI: it points out a different route to the server than what the A/AAAA records for it say.

The Alt-Svc header came into life as an attempt to help out with HTTP/2 load balancing, since with the introduction of HTTP/2 clients would suddenly use much more persistent and long-living connections instead of the very short ones used for traditional HTTP/1 web browsing which changed the nature of how connections are done. This way, a system that is about to go down can hint the clients on how to continue using the service, elsewhere.

Alt-Svc: h2="backup.example.com:443"; ma=2592000;

HTTP upgrades

Once that header was published, the by then already existing and deployed Google QUIC protocol switched to using the Alt-Svc header to hint clients (read “Chrome users”) that “hey, this service is also available over gQUIC“. (Prior to that, they used their own custom alternative header that basically had the same meaning.)

This is important because QUIC is not TCP. Resources on the web that are pointed out using the traditional HTTPS:// URLs, still imply that you connect to them using TCP on port 443 and you negotiate TLS over that connection. Upgrading from HTTP/1 to HTTP/2 on the same connection was “easy” since they were both still TCP and TLS. All we needed then was to use the ALPN extension and voila: a nice and clean version negotiation.

To upgrade a client and server communication into a post-TCP protocol, the only official way to it is to first connect using the lowest common denominator that the HTTPS URL implies: TLS over TCP, and only once the server tells the client what more there is to try, the client can go on and try out the new toys.

For HTTP/3, this is the official way for HTTP servers to tell users about the availability of an HTTP/3 upgrade option.

curl

I want curl to support HTTP/3 as soon as possible and then as I’ve mentioned above, understanding Alt-Svc is a key prerequisite to have a working “bootstrap”. curl needs to support Alt-Svc. When we’re implementing support for it, we can just as well support the whole concept and other protocol versions and not just limit it to HTTP/3 purposes.

curl will only consider received Alt-Svc headers when talking HTTPS since only then can it know that it actually speaks with the right host that has the authority enough to point to other places.

Experimental

This is the first feature and code that we merge into curl under a new concept we do for “experimental” code. It is a way for us to mark this code as: we’re not quite sure exactly how everything should work so we allow users in to test and help us smooth out the quirks but as a consequence of this we might actually change how it works, both behavior and API wise, before we make the support official.

We strongly discourage anyone from shipping code marked experimental in production. You need to explicitly enable this in the build to get the feature. (./configure –enable-alt-svc)

But at the same time we urge and encourage interested users to test it out, try how it works and bring back your feedback, criticism, praise, bug reports and help us make it work the way we’d like it to work so that we can make it land as a “normal” feature as soon as possible.

Ship

The experimental alt-svc code has been merged into curl as of commit 98441f3586 (merged March 3rd 2019) and will be present in the curl code starting in the public release 7.64.1 that is planned to ship on March 27, 2019. I don’t have any time schedule for when to remove the experimental tag but ideally it should happen within just a few release cycles.

alt-svc cache

The curl implementation of alt-svc has an in-memory cache of known alternatives. It can also both save that cache to a text file and load that file back into memory. Saving the alt-svc cache to disk allows it to survive curl invokes and to truly work the way it was intended. The cache file stores the expire timestamp per entry so it doesn’t matter if you try to use a stale file.

curl –alt-svc

Caveat: I now talk about how a feature works that I’ve just above said might change before it ships. With the curl tool you ask for alt-svc support by pointing out the alt-svc cache file to use. Or pass a “” (empty name) to make it not load or save any file. It makes curl load an existing cache from that file and at the end, also save the cache to that file.

curl also already since a long time features fancy connection options such as –resolve and –connect-to, which both let a user control where curl connects to, which in many cases work a little like a static poor man’s alt-svc. Learn more about those in my curl another host post.

libcurl options for alt-svc

We start out the alt-svc support for libcurl with two separate options. One sets the file name to the alt-svc cache on disk (CURLOPT_ALTSVC), and the other control various aspects of how libcurl should behave in regards to alt-svc specifics (CURLOPT_ALTSVC_CTRL).

I’m quite sure that we will have reason to slightly adjust these when the HTTP/3 support comes closer to actually merging.

My 10th FOSDEM

I didn’t present anything during last year’s conference, so I submitted my DNS-over-HTTPS presentation proposal early on for this year’s FOSDEM. Someone suggested it was generic enough I should rather ask for main track instead of the DNS room, and so I did. Then time passed and in November 2018 “HTTP/3” was officially coined as a real term and then, after the Mozilla devroom’s deadline had been extended for a week I filed my second proposal. I might possibly even have been an hour or two after the deadline. I hoped at least one of them would be accepted.

Not only were both my proposed talks accepted, I was also approached and couldn’t decline the honor of participating in the DNS privacy panel. Ok, three slots in the same FOSDEM is a new record for me, but hey, surely that’s no problems for a grown-up..

HTTP/3

I of coursed hoped there would be interest in what I had to say.

I spent the time immediately before my talk with a coffee in the awesome newly opened cafeteria part to have a moment of calmness before I started. I then headed over to the U2.208 room maybe half an hour before the start time.

It was packed. Quite literally there were hundreds of persons waiting in the area outside the U2 rooms and there was this totally massive line of waiting visitors queuing to get into the Mozilla room once it would open.

The “Sorry, this room is FULL” sign is commonly seen on FOSDEM.

People don’t know who I am by my appearance so I certainly didn’t get any special treatment, waiting for my talk to start. I waited in line with the rest and when the time for my presentation started to get closer I just had to excuse myself, leave my friends behind and push through the crowd. I managed to get a “sorry, it’s full” told to me by a conference admin before one of the room organizers recognized me as the speaker of the next talk and I could walk by a very long line of humans that eventually would end up not being able to get in. The room could fit 170 souls, and every single seat was occupied when I started my presentation just a few minutes late.

This presentation could have filled a much larger room. Two years ago my HTTP/2 talk filled up the 300 seat room Mozilla had that year.

Video

Video from my HTTP/3 talk. Duration 1 hour.

The slides from my HTTP/3 presentation.

DNS over HTTPS

I tend to need a little “landing time” after having done a presentation to cool off an come back to normal senses and adrenaline levels again. I got myself a lunch, a beer and chatted with friends in the cafeteria (again). During this conversation, it struck me I had forgotten something in my coming presentation and I added a slide that I felt would improve it (the screenshot showing “about:networking#dns” output with DoH enabled). In what felt like no time, it was again to move. I walked over to Janson, the giant hall that fits 1,470 persons, which I entered a few minutes ahead of my scheduled time and began setting up my machine.

I started off with a little technical glitch because the projector was correctly detected and setup as a second screen on my laptop but it would detect and use a too high resolution for it, but after just a short moment of panic I lowered the resolution on that screen manually and the image appeared fine. Phew! With a slightly raised pulse, I witnessed the room fill up. Almost full. I estimate over 90% of the seats were occupied.

The DNS over HTTPS talk seen from far back. Photo by Steve Holme.

This was a brand new talk with all new material and I performed it for the largest audience I think I’ve ever talked in front of.

Video

Video of my DNS over HTTPS presentation. Duration 50 minutes.

To no surprise, my talk triggered questions and objections. I spent a while in the corridor behind Janson afterward, discussing DoH details, the future of secure DNS and other subtle points of the different protocols involved. In the end I think I manged pretty good, and I had expected more arguments and more tough questions. This is after all the single topic I’ve had more abuse and name-calling for than anything else I’ve ever worked on before in my 20+ years in Internet protocols. (After all, I now often refer to myself and what I do as webshit.)

My DNS over HTTPS slides.

DNS Privacy panel

I never really intended to involve myself in DNS privacy discussions, but due to the constant misunderstandings and mischaracterizations (both on purpose and by ignorance) sometimes spread about DoH, I’ve felt a need to stand up for it a few times. I think that was a contributing factor to me getting invited to be part of the DNS privacy panel that the organizers of the DNS devroom setup.

There are several problems and challenges left to solve before we’re in a world with correctly and mostly secure DNS. DoH is one attempt to raise the bar. I was content to had the opportunity to really spell out my view of things before the DNS privacy panel.

While sitting next to these giants from the DNS world, Stéphane Bortzmeyer, Bert Hubert and me discussed DoT, DoH, DNS centralization, user choice, quad-dns-hosters and more. The discussion didn’t get very heated but instead I think it showed that we’re all largely in agreement that we need more secure DNS and that there are obstacles in the way forward that we need to work further on to overcome. Moderator Jan-Piet Mens did an excellent job I think, handing over the word, juggling the questions and taking in questions from the audience.

Video

Video from the DNS Privacy panel. Duration 30 minutes.

Ten years, ten slots

Appearing in three scheduled slots during the same FOSDEM was a bit much, and it effectively made me not attend many other talks. They were all great fun to do though, and I appreciate people giving me the chance to share my knowledge and views to the world. As usually very nicely organized and handled. The videos of each presentation are linked to above.

I met many people, old and new friends. I handed out a lot of curl stickers and I enjoyed talking to people about my recently announced new job at wolfSSL.

After ten consecutive annual visits to FOSDEM, I have appeared in ten program slots!

I fully intend to go back to FOSDEM again next year. For all the friends, the waffles, the chats, the beers, the presentations and then for the waffles again. Maybe I will even present something…

HTTP/3 talk on video

Yesterday, I had attracted audience enough to fill up the largest presentation room GOTO 10 has, which means about one hundred interested souls.

The subject of the day was HTTP/3. The event was filmed with a mevo camera and I captured the presentation directly from my laptop as well, and I then stitched together the two sources into this final version late last night. As you’ll notice, the sound isn’t awesome and the rest of the “production” isn’t exactly top notch either, but hey, I don’t think it matters too much.

I’ll talk about HTTP/3 (Photo by Jon Åslund)
I’m Daniel Stenberg. I was handed a medal from the Swedish king in 2017 for my work on… (Photo by OpenTokix)
HTTP/2 vs HTTP/3 (Photo by OpenTokix)
Some of the challenges to deploy HTTP/3 are…. (Photo by Jonathan Sulo)

The slide set can also be viewed on slideshare.

QUIC and missing APIs

I trust you’ve heard by now that HTTP/3 is coming. It is the next destined HTTP version, targeted to get published as an RFC in July 2019. Not very far off.

HTTP/3 will not be done over TCP. It will only be performed over QUIC, which is a transport protocol replacement for TCP that always is done encrypted. There’s no clear-text version of QUIC.

TLS 1.3

The encryption in QUIC is based on TLS 1.3 technologies which I believe everyone thinks is a good idea and generally the correct decision. We need to successively raise the bar as we move forward with protocols.

However, QUIC is not only a transport protocol that does encryption by itself while TLS is typically (and designed as) a protocol that is done on top of TCP, it was also designed by a team of engineers who came up with a design that requires APIs from the TLS layer that the traditional TLS over TCP use case doesn’t need!

New TLS APIs

A QUIC implementation needs to extract traffic secrets from the TLS connection and it needs to be able to read/write TLS messages directly – not using the TLS record layer. TLS records are what’s used when we send TLS over TCP. (This was discussed and decided back around the time for the QUIC interim in Kista.)

These operations need APIs that still are missing in for example the very popular OpenSSL library, but also in other commonly used ones like GnuTLS and libressl. And of course schannel and Secure Transport.

Libraries known to already have done the job and expose the necessary mechanisms include BoringSSL, NSS, quicly, PicoTLS and Minq. All of those are incidentally TLS libraries with a more limited number of application users and less mainstream. They’re also more or less developed by people who are also actively engaged in the QUIC protocol development.

The QUIC libraries in progress now are typically using either one of the TLS libraries that already are adapted or do what ngtcp2 does: it hosts a custom-patched version of OpenSSL that brings the needed functionality.

Matt Caswell of the OpenSSL development team acknowledged this situation already back in September 2017, but so far we haven’t seen this result in updated code shipped in a released version.

curl and QUIC

curl is TLS library agnostic and can get built with around 12 different TLS libraries – one or many actually, as you can build it to allow users to select TLS backend in run-time!

OpenSSL is without competition the most popular choice to build curl with outside of the proprietary operating systems like macOS and Windows 10. But even the vendor-build and provided mac and Windows versions are also built with libraries that lack APIs for this.

With our current keen interest in QUIC and HTTP/3 support for curl, we’re about to run into an interesting TLS situation. How exactly is someone going to build curl to simultaneously support both traditional TLS based protocols as well as QUIC going forward?

I don’t have a good answer to this yet. Right now (assuming we would have the code ready in our end, which we don’t), we can’t ship QUIC or HTTP/3 support enabled for curl built to use the most popular TLS libraries! Hopefully by the time we get our code in order, the situation has improved somewhat.

This will slow down QUIC deployment

I’m personally convinced that this little API problem will be friction enough when going forward that it will slow down and hinder QUIC deployment at least initially.

When the HTTP/2 spec shipped in May 2015, it introduced a dependency on the fairly new TLS extension called ALPN that for a long time caused head aches for server admins since ALPN wasn’t supported in the OpenSSL versions that was typically installed and used at the time, but you had to upgrade OpenSSL to version 1.0.2 to get that supported.

At that time, almost four years ago, OpenSSL 1.0.2 was already released and the problem was big enough to just upgrade to that. This time, the API we’re discussing here is not even in a beta version of OpenSSL and thus hasn’t been released in any version yet. That’s far worse than the HTTP/2 situation we had and that took a few years to ride out.

Will we get these APIs into an OpenSSL release to test before the QUIC specification is done? If the schedule sticks, there’s about six months left…

My talks at FOSDEM 2019

I’ll be celebrating my 10th FOSDEM when I travel down to Brussels again in early February 2019. That’s ten years in a row. It’ll also be the 6th year I present something there, as I’ve done these seven talks in the past:

My past FOSDEM appearances

2010. I talked Rockbox in the embedded room.

2011. libcurl, seven SSL libs and one SSH lib in the security room.

2015. Internet all the things – using curl in your device. In the embedded room.

2015. HTTP/2 right now. In the Mozilla room.

2016. an HTTP/2 update. In the Mozilla room.

2017. curl. On the main track.

2017. So that was HTTP/2, what’s next? In the Mozilla room.

DNS over HTTPS – the good, the bad and the ugly

On the main track, in Janson at 15:00 on Saturday 2nd of February.

DNS over HTTPS (aka “DoH”, RFC 8484) introduces a new transport protocol to do secure and private DNS messaging. Why was it made, how does it work and how users are free (to resolve names).

The presentation will discuss reasons why DoH was deemed necessary and interesting to ship and deploy and how it compares to alternative technologies that offer similar properties. It will discuss how this protocol “liberates” users and offers stronger privacy (than the typical status quo).

How to enable and start using DoH today.

It will also discuss some downsides with DoH and what you should consider before you decide to use a random DoH server on the Internet.

HTTP/3

In the Mozilla room, at 11:30 on Saturday 2nd of February.

HTTP/3 is the next coming HTTP version.

This time TCP is replaced by the new transport protocol QUIC and things are different yet again! This is a presentation about HTTP/3 and QUIC with a following Q&A about everything HTTP. Join us at Goto 10.

HTTP/3 is the designated name for the coming next version of the protocol that is currently under development within the QUIC working group in the IETF.

HTTP/3 is designed to improve in areas where HTTP/2 still has some shortcomings, primarily by changing the transport layer. HTTP/3 is the first major protocol to step away from TCP and instead it uses QUIC. I’ll talk about HTTP/3 and QUIC. Why the new protocols are deemed necessary, how they work, how they change how things are sent over the network and what some of the coming deployment challenges will be.

DNS Privacy panel

In the DNS room, at 11:55 on Sunday 3rd of February.

This isn’t strictly a prepared talk or presentation but I’ll still be there and participate in the panel discussion on DNS privacy. I hope to get most of my finer points expressed in the DoH talk mentioned above, but I’m fully prepared to elaborate on some of them in this session.