Category Archives: Work

Work stuff

IT Politics, Work

One year in still no visa

3 Comments

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”.

Lots of things have happened in my life since last April. I quit my job at Mozilla and started a new job at wolfSSL, again working for a US based company. One that I cannot go visit.

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.


cURL and libcurl, wolfSSL

curl up 2019 is over

(I will update this blog post with more links to videos and PDFs to presentations as they get published, so come back later in case your favorite isn’t linked already.)

The third curl developers conference, curl up 2019, is how history. We gathered in the lovely Charles University in central Prague where we sat down in an excellent class room. After the HTTP symposium on the Friday, we spent the weekend to dive in deeper in protocols and curl details.

I started off the Saturday by The state of the curl project (youtube). An overview of how we’re doing right now in terms of stats, graphs and numbers from different aspects and then something about what we’ve done the last year and a quick look at what’s not do good and what we could work on going forward.

James Fuller took the next session and his Newbie guide to contributing to libcurl presentation. Things to consider and general best practices to that could make your first steps into the project more likely to be pleasant!

Long term curl hacker Dan Fandrich (also known as “Daniel two” out of the three Daniels we have among our top committers) followed up with Writing an effective curl test where the detailed what different tests we have in curl, what they’re for and a little about how to write such tests.

Sign seen at the curl up dinner reception Friday night

After that I was back behind the desk in the classroom that we used for this event and I talked The Deprecation of legacy crap (Youtube). How and why we are removing things, some things we are removing and will soon remove and finally a little explainer on our new concept and handling of “experimental” features.

Igor Chubin then explained his new protect for us: curlator: a framework for console services (Youtube). It’s a way and tooling that makes it easier to provide access to shell and console oriented services over the web, using curl.

Me again. Governance, money in the curl project and someone offering commercial support (Youtube) was a presentation about how we intend for the project to join a legal entity SFC, and a little about money we have, what to spend it on and how I feel it is good to keep the project separate from any commercial support ventures any of us might do!

While the list above might seems like more than enough, the day wasn’t over. Christian Schmitz also did his presentation on Using SSL root certificate from Mac/Windows.

Our local hero organizer James Fuller then spoiled us completely when we got around to have dinner at a monastery with beer brewing monks and excellent food. Good food, good company and curl related dinner subjects. That’s almost heaven defined!

Sunday

Daylight saving time morning and you could tell. I’m sure it was not at all related to the beers from the night before…

James Fuller fired off the day by talking to us about Curlpipe (github), a DSL for building http execution pipelines.

The class room we used for the curl up presentations and discussions during Saturday and Sunday.

Robin Marx then put in the next gear and entertained us another hour with a protocol deep dive titled HTTP/3 (QUIC): the details (slides). For me personally this was a exactly what I needed as Robin clearly has kept up with more details and specifics in the QUIC and HTTP/3 protocols specifications than I’ve managed and his talk help the rest of the room get at least little bit more in sync with current development.

Jakub Nesetril and Lukáš Linhart from Apiary then talked us through what they’re doing and thinking around web based APIs and how they and their customers use curl: Real World curl usage at Apiary.

Then I was up again and I got to explain to my fellow curl hackers about HTTP/3 in curl. Internal architecture, 3rd party libs and APIs.

Jakub Klímek explained to us in very clear terms about current and existing problems in his talk IRIs and IDNs: Problems of non-ASCII countries. Some of the problems involve curl and while most of them have their clear explanations, I think we have to lessons to learn from this: URLs are still as messy and undocumented as ever before and that we might have some issues to fix in this area in curl.

To bring my fellow up to speed on the details of the new API introduced the last year I then made a presentation called The new URL API.

Clearly overdoing it for a single weekend, I then got the honors of doing the last presentation of curl up 2019 and for an audience that were about to die from exhaustion I talked Internals. A walk-through of the architecture and what libcurl does when doing a transfer.

Summary

I ended up doing seven presentations during this single weekend. Not all of them stellar or delivered with elegance but I hope they were still valuable to some. I did not steal someone else’s time slot as I would gladly have given up time if we had other speakers wanted to say something. Let’s aim for more non-Daniel talkers next time!

A weekend like this is such a boost for inspiration, for morale and for my ego. All the friendly faces with the encouraging and appreciating comments will keep me going for a long time after this.

Thank you to our awesome and lovely event sponsors – shown in the curl up logo below! Without you, this sort of happening would not happen.

curl up 2020

I will of course want to see another curl up next year. There are no plans yet and we don’t know where to host. I think it is valuable to move it around but I think it is even more valuable that we have a friend on the ground in that particular city to help us out. Once this year’s event has sunken in properly and a month or two has passed, the case for and organization of next year’s conference will commence. Stay tuned, and if you want to help hosting us do let me know!


cURL and libcurl, wolfSSL

commercial curl support!

If you want commercial support, ports of curl to other operating systems or just instant help to fix your curl related problems, we’re here to help. Get in touch now! This is the premiere. This has not been offered by me or anyone else before.

I’m not sure I need to say it, but I personally have authored almost 60% of all commits in the curl source code during my more than twenty years in the project. I started the project, I’ve designed its architecture etc. There is simply no one around with my curl experience and knowledge of curl internals. You can’t buy better curl expertise.

curl has become one of the world’s most widely used software components and is the transfer engine doing a large chunk of all non-browser Internet transfers in the world today. curl has reached this level of success entirely without anyone offering commercial services around it. Still, not every company and product made out there has a team of curl experts and in this demanding time and age we know there are times when you rather hire the right team to help you out.

We are the curl experts that can help you and your team. Contact us for all and any support questions at support@wolfssl.com.

What about the curl project?

I’m heading into this new chapter of my life and the curl project with the full knowledge that this blurs the lines between my job and my spare time even more than before. But fear not!

The curl project is free and open and will remain independent of any commercial enterprise helping out customers. I realize me offering companies and organizations to deal with curl problems and solving curl issues for compensation creates new challenges and questions where boundaries go, if for nothing else for me personally. I still think this is worth pursuing and I’m sure we can figure out and handle whatever minor issues this can lead to.

My friends, the community, the users and harsh critiques on twitter will all help me stay true and honest. I know this. This should end up a plus for the curl project in general as well as for me personally. More focus, more work and more money involved in curl related activities should improve the project.

It is with great joy and excitement I take on this new step.

cURL and libcurl, Work

I’m on team wolfSSL

4 Comments

Let me start by saying thank you to all and everyone who sent me job offers or otherwise reached out with suggestions and interesting career moves. I received more than twenty different offers and almost every one of those were truly good options that I could have said yes to and still pulled home a good job. What a luxury challenge to have to select something from that! Publicly announcing me leaving Mozilla turned out a great ego-boost.

I took some time off to really reflect and contemplate on what I wanted from my next career step. What would the right next move be?

I love working on open source. Internet protocols, and transfers and doing libraries written in C are things considered pure fun for me. Can I get all that and yet keep working from home, not sacrifice my wage and perhaps integrate working on curl better in my day to day job?

I talked to different companies. Very interesting companies too, where I have friends and people who like me and who really wanted to get me working for them, but in the end there was one offer with a setup that stood out. One offer for which basically all check marks in my wish-list were checked.

wolfSSL

On February 5, 2019 I’m starting my new job at wolfSSL. My short and sweet period as unemployed is over and now it’s full steam ahead again! (Some members of my family have expressed that they haven’t really noticed any difference between me having a job and me not having a job as I spend all work days the same way nevertheless: in front of my computer.)

Starting now, we offer commercial curl support and various services for and around curl that companies and organizations previously really haven’t been able to get. Time I do not spend on curl related activities for paying customers I will spend on other networking libraries in the wolfSSL “portfolio”. I’m sure I will be able to keep busy.

I’ve met Larry at wolfSSL physically many times over the years and every year at FOSDEM I’ve made certain to say hello to my wolfSSL friends in their booth they’ve had there for years. They’re truly old-time friends.

wolfSSL is mostly a US-based company – I’m the only Swede on the team and the only one based in Sweden. My new colleagues all of course know just as well as you that I’m prevented from traveling to the US. All coming physical meetings with my work mates will happen in other countries.

commercial curl support!

We offer all sorts of commercial support for curl. I’ll post separately with more details around this.

cURL and libcurl, Mozilla, Network, Work

I’m leaving Mozilla

8 Comments

It’s been five great years, but now it is time for me to move on and try something else.

During these five years I’ve met and interacted with a large number of awesome people at Mozilla, lots of new friends! I got the chance to work from home and yet work with a global team on a widely used product, all done with open source. I have worked on internet protocols during work-hours (in addition to my regular spare-time working with them) and its been great! Heck, lots of the HTTP/2 development and the publication of that was made while I was employed by Mozilla and I fondly participated in that. I shall forever have this time ingrained in my memory as a very good period of my life.

I had already before I joined the Firefox development understood some of the challenges of making a browser in the modern era, but that understanding has now been properly enriched with lots of hands-on and code-digging in sometimes decades-old messy C++, a spaghetti armada of threads and the wild wild west of users on the Internet.

A very big thank you and a warm bye bye go to everyone of my friends at Mozilla. I won’t be far off and I’m sure I will have reasons to see many of you again.

My last day as officially employed by Mozilla is December 11 2018, but I plan to spend some of my remaining saved up vacation days before then so I’ll hand over most of my responsibilities way before.

The future is bright but unknown!

I don’t yet know what to do next.

I have some ideas and communications with friends and companies, but nothing is firmly decided yet. I will certainly entertain you with a totally separate post on this blog once I have that figured out! Don’t worry.

Will it affect curl or other open source I do?

I had worked on curl for a very long time already before joining Mozilla and I expect to keep doing curl and other open source things even going forward. I don’t think my choice of future employer should have to affect that negatively too much, except of course in periods.

With me leaving Mozilla, we’re also losing Mozilla as a primary sponsor of the curl project, since that was made up of them allowing me to spend some of my work days on curl and that’s now over.

Short-term at least, this move might increase my curl activities since I don’t have any new job yet and I need to fill my days with something…

What about toying with HTTP?

I was involved in the IETF HTTPbis working group for many years before I joined Mozilla (for over ten years now!) and I hope to be involved for many years still. I still have a lot of things I want to do with curl and to keep curl the champion of its class I need to stay on top of the game.

I will continue to follow and work with HTTP and other internet protocols very closely. After all curl remains the world’s most widely used HTTP client.

Can I enter the US now?

No. That’s unfortunately not related, and I’m not leaving Mozilla because of this problem and I unfortunately don’t expect my visa situation to change because of this change. My visa counter is now showing more than 214 days since I applied.

Firefox, Mozilla, Security, Web

How to DoH-only with Firefox

2 Comments

Firefox supports DNS-over-HTTPS (aka DoH) since version 62.

You can instruct your Firefox to only use DoH and never fall-back and try the native resolver; the mode we call trr-only. Without any other ability to resolve host names, this is a little tricky so this guide is here to help you. (This situation might improve in the future.)

In trr-only mode, nobody on your local network nor on your ISP can snoop on your name resolves. The SNI part of HTTPS connections are still clear text though, so eavesdroppers on path can still figure out which hosts you connect to.

There’s a name in my URI

A primary problem for trr-only is that we usually want to use a host name in the URI for the DoH server (we typically need it to be a name so that we can verify the server’s certificate against it), but we can’t resolve that host name until DoH is setup to work. A catch-22.

There are currently two ways around this problem:

  1. Tell Firefox the IP address of the name that you use in the URI. We call it the “bootstrapAddress”. See further below.
  2. Use a DoH server that is provided on an IP-number URI. This is rather unusual. There’s for example one at 1.1.1.1.

Setup and use trr-only

There are three prefs to focus on (they’re all explained elsewhere):

network.trr.mode – set this to the number 3.

network.trr.uri – set this to the URI of the DoH server you want to use. This should be a server you trust and want to hand over your name resolves to. The Cloudflare one we’ve previously used in DoH tests with Firefox is https://mozilla.cloudflare-dns.com/dns-query.

network.trr.bootstrapAddress– when you use a host name in the URI for the network.trr.uri pref you must set this pref to an IP address that host name resolves to for you. It is important that you pick an IP address that the name you use actually would resolve to.

Example

Let’s pretend you want to go full trr-only and use a DoH server at https://example.com/dns. (it’s a pretend URI, it doesn’t work).

Figure out the bootstrapAddress with dig. Resolve the host name from the URI:

$ dig +short example.com
93.184.216.34

or if you prefer to be classy and use the IPv6 address (only do this if IPv6 is actually working for you)

$ dig -t AAAA +short example.com
2606:2800:220:1:248:1893:25c8:1946

dig might give you a whole list of addresses back, and then you can pick any one of them in the list. Only pick one address though.

Go to “about:config” and paste the copied IP address into the value field for network.trr.bootstrapAddress. Now TRR / DoH should be able to get going. When you can see web pages, you know it works!

DoH-only means only DoH

If you happen to start Firefox behind a captive portal while in trr-only mode, the connections to the DoH server will fail and no name resolves can be performed.

In those situations, normally Firefox’s captive portable detector would trigger and show you the login page etc, but when no names can be resolved and the captive portal can’t respond with a fake response to the name lookup and redirect you to the login, it won’t get anywhere. It gets stuck. And currently, there’s no good visual indication anywhere that this is what happens.

You simply can’t get out of a captive portal with trr-only. You probably then temporarily switch mode, login to the portal and switch the mode to 3 again.

If you “unlock” the captive portal with another browser/system, Firefox’s regular retries while in trr-only will soon detect that and things should start working again.

Mozilla, Work

administrative purgatory

9 Comments

 your case is still going through administrative processing and we don’t know when that process will be completed.

Last year I was denied to go to the US when I was about to travel to San Francisco. Me and my employer’s legal team never got answers as to why this happened so I’ve personally tried to convince myself it was all because of some human screw-up. Because why would they suddenly block me? I’ve traveled to the US almost a dozen times over the years.

The fact that there was no reason or explanation given makes any theory as likely as the next. Whatever we think or guess might have happened can be true. Or not. We will probably never know. And I’ve been told a lot of different theories.

Denied again

In early April 2018 I applied for ESTA again to go to San Francisco in mid June for another Mozilla All Hands conference and… got denied. The craziness continues. This also ruled out some of the theories from last year that it was just some human error by the airline or similar…

As seen on the screenshot, this decision has no expire date… While they don’t provide any motivation for not accepting me, this result makes it perfectly clear that it wasn’t just a mistake last year. It makes me view last year with different eyes.

Put in this situation, I activated plan B.

Plan B

I then applied for a “real” non-immigrant visa – even though it feels that having been denied ESTA probably puts me in a disadvantage for that as well. Applying for this visa means filling in a 10-something-page “DS-160” form online on a site that sometimes takes minutes just to display the next page in the form where they ask for a lot of personal details. After finally having conquered that obstacle, I paid the 160 USD fee and scheduled an appointment to appear physically at the US embassy in Sweden.

I acquired an “extraction of the population register” (“personbevis” in Swedish) from the Swedish tax authorities – as required (including personal details of my parents and siblings), I got myself a new mugshot printed on photo paper and was lucky enough to find a date for an appointment not too far into the future.

Appointment

I spent the better part of a fine Tuesday morning in different waiting lines at my local US embassy where I eventually was called up to a man at a counter behind a window. I was fingerprinted, handed over my papers and told the clerk I have no idea why I was denied ESTA when asked, and no, I have not been on vacation in Iraq, Iran or Sudan. The clerk gave me the impression that’s the sort of thing that is the common reason for not getting ESTA.

When I answered the interviewer’s question that I work for Mozilla, he responded “Aha, Firefox?” – which brightened up my moment a little.

Apparently the process is then supposed to take “several weeks” until I get to know anything more. I explained that I needed my passport in three weeks (for another trip) and he said he didn’t expect them to be done that quickly.  Therefore I got the passport back while they process my application and I’m expected to mail it to them when they ask for it.

The next form

When I got back home again, I got an email from “the visa unit” asking me to fill in another form (in the shape of a Word document). And what a form it is! It might be called “OMB 1405-0226” and has this fancy title:

“SUPPLEMENTAL QUESTIONS FOR VISA APPLICANTS”

Among other things it requires me to provide info about all trips abroad (with dates and duration) I’ve done over the last 15 years. What aliases I use on social media sites (hello mr US visa agent, how do you like this post so far?), every physical address I’ve lived at in the last 15 years, information about all my employers the last 15 years and every email address I’ve used during the last 5 years.

It took me many hours digging through old calendars, archives and memories and asking around in order to fill this in properly. (“hey that company trip we did to Germany back in 2005, can you remember the dates?”) As a side-note: it turns out I’ve been in the US no less than nine times the last fifteen years. In total I managed to list sixty-five different trips abroad for this period.

How do I submit my filled-in form, with all these specific and very private details from my life for the last 15 years, back to “the visa unit”? By email. Good old insecure, easy to snoop on, email! At least I’m using my own mail server (and it is configured to prefer TLS for connections) but that’s a small comfort.

Is it worth it?

This is a very time and energy consuming process – I understand why this puts people off and simply make them decide its not worth it to go there. And of course I understand that I’m in a lucky position where I’ve not had to deal with this much in the past.

I have many friends and contacts in the US in both my personal and professional life. I would be sad if I couldn’t go there ever again. It would give me grief personally since it’ll limit where I can go on vacation and who out of my friends I can visit, but it will also limit my professional life as interesting Mozilla, Internet, open source and curl related events that I’d like to attend are frequently hosted there.

What’s happening?

So the weeks came and went and on May 29th,  six weeks after I was interviewed at the embassy, I checked the online service that allows me to check my application progress. It said “Case Created: April 17” and the following useful addition “Case Last Updated: April 17”.

Wat? Did something go fatally wrong here? I emailed the embassy to double-check. I got this single sentence response back:

Dear Sir,

You don't have to do anything, your case is still going through administrative processing and we don't know when that process will be completed.

In my life I’ve visited a whole series of countries for which I’ve been required to apply for a visa. None of them have ever taken more than a few weeks, including countries with complicated bureaucracy like India and China. What are they doing all this time?

At the time of this writing, more than 100 days have passed and I have still not heard back from them. I know this is unusually long and I have a strong suspicion this means they will deny me visa, but for some reason they want to keep me unaware for a while more.

No All Hands in the US

I clearly underestimated the time this required so I missed our meeting in SF this year again…

Mozilla has since then announced that a number of the forthcoming All Hands conferences in the coming years will be held outside of the US. Unfortunately several of them are to be held in Canada, and there are indications that having being denied entry to the US means that Canada will deny me as well. But I have yet to test that!

Why they deny me?

Me knowingly, I’ve never broken a law, rule or regulation that would explain this. Some speculations me and others can think of include…

  1. I’m the main author of curl, a tool that is used in a lot of security research and proof of concept exploits of security vulnerabilities
  2. I’m the main author of libcurl, a transfer library that is one of the world’s most widely used software components. It is subsequently also used extensively by malware and other offensive and undesired software.
  3. I use the name haxx.se domain for many of my sites and email address etc. haxx or hacking could be interpreted by some, not as “To program a computer in a clever, virtuosic, and wizardly manner” but as the act to “gain unauthorized access to data in a system or computer”.
  4. It’s been suggested that my presence at multiple conferences in the US over the years could’ve been a violation of the ESTA rules – but the rules explicitly allow this. I have not violated the ESTA rules.

Administrative Processing

It’s been 102 days now. I’m not optimistic.

Firefox, Mozilla, Network, Security

quic wg interim Kista

The IETF QUIC working group had its fifth interim meeting the other day, this time in Kista, Sweden hosted by Ericsson. For me as a Stockholm resident, this was ridiculously convenient. Not entirely coincidentally, this was also the first quic interim I attended in person.

We were 30 something persons gathered in a room without windows, with another dozen or so participants joining from remote. This being a meeting in a series, most people already know each other from before so the atmosphere was relaxed and friendly. Lots of the participants have also been involved in other protocol developments and standards before. Many familiar faces.

Schedule

As QUIC is supposed to be done “soon”, the emphasis is now a lot to close issues, postpone some stuff to “QUICv2” and make sure to get decisions on outstanding question marks.

Kazuho did a quick run-through with some info from the interop days prior to the meeting.

After MT’s initial explanation of where we’re at for the upcoming draft-13, Ian took us a on a deep dive into the Stream 0 Design Team report. This is a pretty radical change of how the wire format of the quic protocol, and how the TLS is being handled.

The existing draft-12 approach…

Is suggested to instead become…

What’s perhaps the most interesting take away here is that the new format doesn’t use TLS records anymore – but simplifies a lot of other things. Not using TLS records but still doing TLS means that a QUIC implementation needs to get data from the TLS layer using APIs that existing TLS libraries don’t typically provide. PicoTLS, Minq, BoringSSL. NSS already have or will soon provide the necessary APIs. Slightly behind, OpenSSL should offer it in a nightly build soon but the impression is that it is still a bit away from an actual OpenSSL release.

EKR continued the theme. He talked about the quic handshake flow and among other things explained how 0-RTT and early data works. Taken from that context, I consider this slide (shown below) fairly funny because it makes it look far from simple to me. But it shows communication in different layers, and how the acks go, etc.

HTTP

Mike then presented the state of HTTP over quic. The frames are no longer that similar to the HTTP/2 versions. Work is done to ensure that the HTTP layer doesn’t need to refer or “grab” stream IDs from the transport layer.

There was a rather lengthy discussion around how to handle “placeholder streams” like the ones Firefox uses over HTTP/2 to create “anchors” on which to make dependencies but are never actually used over the wire. The nature of the quic transport makes those impractical and we talked about what alternatives there are that could still offer similar functionality.

The subject of priorities and dependencies and if the relative complexity of the h2 model should be replaced by something simpler came up (again) but was ultimately pushed aside.

QPACK

Alan presented the state of QPACK, the HTTP header compression algorithm for hq (HTTP over QUIC). It is not wire compatible with HPACK anymore and there have been some recent improvements and clarifications done.

Alan also did a great step-by-step walk-through how QPACK works with adding headers to the dynamic table and how it works with its indices etc. It was very clarifying I thought.

The discussion about the static table for the compression basically ended with us agreeing that we should just agree on a fairly small fixed table without a way to negotiate the table. Mark said he’d try to get some updated header data from some server deployments to get another data set than just the one from WPT (which is from a single browser).

Interop-testing of QPACK implementations can be done by encode  + shuffle + decode a HAR file and compare the results with the source data. Just do it – and talk to Alan!

And the first day was over. A fully packed day.

ECN

Magnus started off with some heavy stuff talking Explicit Congestion Notification in QUIC and it how it is intended to work and some remaining issues.

He also got into the subject of ACK frequency and how the current model isn’t ideal in every situation, causing to work like this image below (from Magnus’ slide set):

Interestingly, it turned out that several of the implementers already basically had implemented Magnus’ proposal of changing the max delay to min(RTT/4, 25 ms) independently of each other!

mvfst deployment

Subodh took us on a journey with some great insights from Facebook’s deployment of mvfast internally, their QUIC implementation. Getting some real-life feedback is useful and with over 100 billion requests/day, it seems they did give this a good run.

Since their usage and stack for this is a bit use case specific I’m not sure how relevant or universal their performance numbers are. They showed roughly the same CPU and memory use, with a 70% RPS rate compared to h2 over TLS 1.2.

He also entertained us with some “fun issues” from bugs and debugging sessions they’ve done and learned from. Awesome.

The story highlights the need for more tooling around QUIC to help developers and deployers.

Load balancers

Martin talked about load balancers and servers, and how they could or should communicate to work correctly with routing and connection IDs.

The room didn’t seem overly thrilled about this work and mostly offered other ways to achieve the same results.

Implicit Open

During the last session for the day and the entire meeting, was mt going through a few things that still needed discussion or closure. On stateless reset and the rather big bike shed issue: implicit open. The later being the question if opening a stream with ID N + 1 implicitly also opens the stream with ID N. I believe we ended with a slight preference to the implicit approach and this will be taken to the list for a consensus call.

Frame type extensibility

How should the QUIC protocol allow extensibility? The oldest still open issue in the project can be solved or satisfied in numerous different ways and the discussion waved back and forth for a while, debating various approaches merits and downsides until the group more or less agreed on a fairly simple and straight forward approach where the extensions will announce support for a feature which then may or may involve one or more new frame types (to be in a registry).

We proceeded to discuss other issues all until “closing time”, which was set to be 16:00 today. This was just two days of pushing forward but still it felt quite intense and my personal impression is that there were a lot of good progress made here that took the protocol a good step forward.

The facilities were lovely and Ericsson was a great host for us. The Thursday afternoon cakes were great! Thank you!

Coming up

There’s an IETF meeting in Montreal in July and there’s a planned next QUIC interim probably in New York in September.

Firefox, Mozilla, Web

Inside Firefox’s DOH engine

14 Comments

DNS over HTTPS (DOH) is a feature where a client shortcuts the standard native resolver and instead asks a dedicated DOH server to resolve names.

Compared to regular unprotected DNS lookups done over UDP or TCP, DOH increases privacy, security and sometimes even performance. It also makes it easy to use a name server of your choice for a particular application instead of the one configured globally (often by someone else) for your entire system.

DNS over HTTPS is quite simply the same regular DNS packets (RFC 1035 style) normally sent in clear-text over UDP or TCP but instead sent with HTTPS requests. Your typical DNS server provider (like your ISP) might not support this yet.

To get the finer details of this concept, check out Lin Clark’s awesome cartoon explanation of DNS and DOH.

This new Firefox feature is planned to get ready and ship in Firefox release 62 (early September 2018). You can test it already now in Firefox Nightly by setting preferences manually as described below.

This article will explain some of the tweaks, inner details and the finer workings of the Firefox TRR implementation (TRR == Trusted Recursive Resolver) that speaks DOH.

Preferences

All preferences (go to “about:config”) for this functionality are located under the “network.trr” prefix.

network.trr.mode – set which resolver mode you want.

0 – Off (default). use standard native resolving only (don’t use TRR at all)
1 – Race native against TRR. Do them both in parallel and go with the one that returns a result first.
2 – TRR first. Use TRR first, and only if the name resolve fails use the native resolver as a fallback.
3 – TRR only. Only use TRR. Never use the native (after the initial setup).
4 – Shadow mode. Runs the TRR resolves in parallel with the native for timing and measurements but uses only the native resolver results.
5 – Explicitly off. Also off, but selected off by choice and not default.

network.trr.uri – (default: none) set the URI for your DOH server. That’s the URL Firefox will issue its HTTP request to. It must be a HTTPS URL (non-HTTPS URIs will simply be ignored). If “useGET” is enabled, Firefox will append “?ct&dns=….” to the URI when it makes its HTTP requests. For the default POST requests, they will be issued to exactly the specified URI.

“mode” and “uri” are the only two prefs required to set to activate TRR. The rest of them listed below are for tweaking behavior.

We list some publicly known DOH servers here. If you prefer to, it is easy to setup and run your own.

network.trr.credentials – (default: none) set credentials that will be used in the HTTP requests to the DOH end-point. It is the right side content, the value, sent in the Authorization: request header. Handy if you for example want to run your own public server and yet limit who can use it.

network.trr.wait-for-portal – (default: true) this boolean tells Firefox to first wait for the captive portal detection to signal “okay” before TRR is used.

network.trr.allow-rfc1918 – (default: false) set this to true to allow RFC 1918 private addresses in TRR responses. When set false, any such response will be considered a wrong response that won’t be used.

network.trr.useGET – (default: false) When the browser issues a request to the DOH server to resolve host names, it can do that using POST or GET. By default Firefox will use POST, but by toggling this you can enforce GET to be used instead. The DOH spec says a server MUST support both methods.

network.trr.confirmationNS – (default: example.com) At startup, Firefox will first check an NS entry to verify that TRR works, before it gets enabled for real and used for name resolves. This preference sets which domain to check. The verification only checks for a positive answer, it doesn’t actually care what the response data says.

network.trr.bootstrapAddress – (default: none) by setting this field to the IP address of the host name used in “network.trr.uri”, you can bypass using the system native resolver for it. This avoids that initial (native) name resolve for the host name mentioned in the network.trr.uri pref.

network.trr.blacklist-duration – (default: 60) is the number of seconds a name will be kept in the TRR blacklist until it expires and can be tried again. The default duration is one minute. (Update: this has been cut down from previous longer defaults.)

network.trr.request-timeout – (default: 3000) is the number of milliseconds a request to and corresponding response from the DOH server is allowed to spend until considered failed and discarded.

network.trr.early-AAAA – (default: false) For each normal name resolve, Firefox issues one HTTP request for A entries and another for AAAA entries. The responses come back separately and can come in any order. If the A records arrive first, Firefox will – as an optimization – continue and use those addresses without waiting for the second response. If the AAAA records arrive first, Firefox will only continue and use them immediately if this option is set to true.

network.trr.max-fails – (default: 5) If this many DoH requests in a row fails, consider TRR broken and go back to verify-NS state. This is meant to detect situations when the DoH server dies.

network.trr.disable-ECS – (default: true) If set, TRR asks the resolver to disable ECS (EDNS Client Subnet – the method where the resolver passes on the subnet of the client asking the question). Some resolvers will use ECS to the upstream if this request is not passed on to them.

Split-horizon and blacklist

With regular DNS, it is common to have clients in different places get different results back. This can be done since the servers know from where the request comes (which also enables quite a degree of spying) and they can then respond accordingly. When switching to another resolver with TRR, you may experience that you don’t always get the same set of addresses back. At times, this causes problems.

As a precaution, Firefox features a system that detects if a name can’t be resolved at all with TRR and can then fall back and try again with just the native resolver (the so called TRR-first mode). Ending up in this scenario is of course slower and leaks the name over clear-text UDP but this safety mechanism exists to avoid users risking ending up in a black hole where certain sites can’t be accessed. Names that causes such TRR failures are then put in an internal dynamic blacklist so that subsequent uses of that name automatically avoids using DNS-over-HTTPS for a while (see the blacklist-duration pref to control that period). Of course this fall-back is not in use if TRR-only mode is selected.

In addition, if a host’s address is retrieved via TRR and Firefox subsequently fails to connect to that host, it will redo the resolve without DOH and retry the connect again just to make sure that it wasn’t a split-horizon situation that caused the problem.

When a host name is added to the TRR blacklist, its domain also gets checked in the background to see if that whole domain perhaps should be blacklisted to ensure a smoother ride going forward.

Additionally, “localhost” and all names in the “.local” TLD are sort of hard-coded as blacklisted and will never be resolved with TRR. (Unless you run TRR-only…)

TTL as a bonus!

With the implementation of DNS-over-HTTPS, Firefox now gets the TTL (Time To Live, how long a record is valid) value for each DNS address record and can store and use that for expiry time in its internal DNS cache. Having accurate lifetimes improves the cache as it then knows exactly how long the name is meant to work and means less guessing and heuristics.

When using the native name resolver functions, this time-to-live data is normally not provided and Firefox does in fact not use the TTL on other platforms than Windows and on Windows it has to perform some rather awkward quirks to get the TTL from DNS for each record.

Server push

Still left to see how useful this will become in real-life, but DOH servers can push new or updated DNS records to Firefox. HTTP/2 Server Push being responses to requests the client didn’t send but the server thinks the client might appreciate anyway as if it sent requests for those resources.

These pushed DNS records will be treated as regular name resolve responses and feed the Firefox in-memory DNS cache, making subsequent resolves of those names to happen instantly.

Bootstrap

You specify the DOH service as a full URI with a name that needs to be resolved, and in a cold start Firefox won’t know the IP address of that name and thus needs to resolve it first (or use the provided address you can set with network.trr.bootstrapAddress). Firefox will then use the native resolver for that, until TRR has proven itself to work by resolving the network.trr.confirmationNS test domain. Firefox will also by default wait for the captive portal check to signal “OK” before it uses TRR, unless you tell it otherwise.

As a result of this bootstrap procedure, and if you’re not in TRR-only mode, you might still get  a few native name resolves done at initial Firefox startups. Just telling you this so you don’t panic if you see a few show up.

CNAME

The code is aware of CNAME records and will “chase” them down and use the final A/AAAA entry with its TTL as if there were no CNAMEs present and store that in the in-memory DNS cache. This initial approach, at least, does not cache the intermediate CNAMEs nor does it care about the CNAME TTL values.

Firefox currently allows no more than 64(!) levels of CNAME redirections.

about:networking

Enter that address in the Firefox URL bar to reach the debug screen with a bunch of networking information. If you then click the DNS entry in the left menu, you’ll get to see the contents of Firefox’s in-memory DNS cache. The TRR column says true or false for each name if that was resolved using TRR or not. If it wasn’t, the native resolver was used instead for that name.

Private Browsing

When in private browsing mode, DOH behaves similar to regular name resolves: it keeps DNS cache entries separately from the regular ones and the TRR blacklist is then only kept in memory and not persisted to disk. The DNS cache is flushed when the last PB session is exited.

Tools

I wrote up dns2doh, a little tool to create DOH requests and responses with, that can be used to build your own toy server with and to generate requests to send with curl or similar.

It allows you to manually issue a type A (regular IPv4 address) DOH request like this:

$ dns2doh --A --onlyq --raw daniel.haxx.se | \
curl --data-binary @- \
https://dns.cloudflare.com/.well-known/dns \
-H "Content-Type: application/dns-udpwireformat"

I also wrote doh, which is a small stand-alone tool (based on libcurl) that issues requests for the A and AAAA records of a given host name from the given DOH URI.

Why HTTPS

Some people giggle and think of this as a massive layer violation. Maybe it is, but doing DNS over HTTPS makes a lot of sense compared to for example using plain TLS:

  1. We get transparent and proxy support “for free”
  2. We get multiplexing and the use of persistent connections from the get go (this can be supported by DNS-over-TLS too, depending on the implementation)
  3. Server push is a potential real performance booster
  4. Browsers often already have a lot of existing HTTPS connections to the same CDNs that might offer DOH.

Further explained in Patrick Mcmanus’ The Benefits of HTTPS for DNS.

It still leaks the SNI!

Yes, the Server Name Indication field in the TLS handshake is still clear-text, but we hope to address that as well in the future with efforts like encrypted SNI.

Bugs?

File bug reports in Bugzilla! (in “Core->Networking:DNS” please)

If you want to enable HTTP logging and see what TRR is doing, set the environment variable MOZ_LOG component and level to “nsHostResolver:5”. The TRR implementation source code in Firefox lives in netwerk/dns.

Caveats

Credits

While I have written most of the Firefox TRR implementation, I’ve been greatly assisted by Patrick Mcmanus. Valentin Gosu, Nick Hurley and others in the Firefox Necko team.

DOH in curl?

Since I am also the lead developer of curl people have asked. The work on DOH for curl has not really started yet, but I’ve collected some thoughts on how DNS-over-HTTPS could be implemented in curl and the doh tool I mentioned above has the basic function blocks already written.

Other efforts to enhance DNS security

There have been other DNS-over-HTTPS protocols and efforts. Recently there was one offered by at least Google that was a JSON style API. That’s different.

There’s also DNS-over-TLS which shares some of the DOH characteristics, but lacks for example the nice ability to work through proxies, do multiplexing and share existing connections with standard web traffic.

DNScrypt is an older effort that encrypts regular DNS packets and sends them over UDP or TCP.

Firefox, Mozilla, Open Source, Web

Firefox Quantum

29 Comments

Next week, Mozilla will release Firefox 57. Also referred to as Firefox Quantum, from the project name we’ve used for all the work that has been put into making this the most awesome Firefox release ever. This is underscored by the fact that I’ve gotten mailed release-swag for the first time during my four years so far as a Mozilla employee.

Firefox 57 is the major milestone hundreds of engineers have worked really hard toward during the last year or so, and most of the efforts have been focused on performance. Or perhaps perceived end user snappiness. Early comments I’ve read and heard also hints that it is also quite notable. I think every single Mozilla engineer (and most non-engineers as well) has contributed to at least some parts of this, and of course many have done a lot. My personal contributions to 57 are not much to write home about, but are mostly a stream of minor things that combined at least move the notch forward.

[edited out some secrets I accidentally leaked here.] I’m a proud Mozillian and being part of a crowd that has put together something as grand as Firefox 57 is an honor and a privilege.

Releasing a product to hundreds of millions of end users across the world is interesting. People get accustomed to things, get emotional and don’t particularly like change very much. I’m sure Firefox 57 will also get a fair share of sour feedback and comments written in uppercase. That’s inevitable. But sometimes, in order to move forward and do good stuff, we have to make some tough decisions for the greater good that not everyone will agree with.

This is however not the end of anything. It is rather the beginning of a new Firefox. The work on future releases goes on, we will continue to improve the web experience for users all over the world. Firefox 58 will have even more goodies, and I know there are much more good stuff planned for the releases coming in 2018 too…

Onwards and upwards!

(Update: as I feared in this text, I got a lot of negativism, vitriol and criticism in the comments to this post. So much that I decided to close down comments for this entry and delete the worst entries.)