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Clutter isn’t just material stuff scattered about your floor and shelves. Clutter can consume us in digital form, too — from an overabundance of browser bookmarks and open tabs to navigating a world wide web that’s littered with junk. The right browser extension, however, can really help clean things up… 

Tranquility Reader

Want to sweep away all the mess around your website reading material, like images, ads, and links to other content you don’t care about? Tranquility Reader does just that. Hit the extension’s toolbar button and presto — everything but the words disappear. 

The extension offers a few other nice features as well, like the ability to save content offline for later reading, customizable font sizes and color, add annotations to saved pages, and more.

Turn Off the Lights for Firefox

Clear out everything on your desktop except the video you want to watch. With the flick of a button, Turn Off the Lights for Firefox fades out everything on screen except your video player. 

More than just a fancy light switch, the extension offers a bunch of great customization features, including… 

• Auto HD for YouTube
• Mouse-wheel volume control
• Atmosphere lighting or background imagery
• Lots of fun fade out/in visual effects

Unhook

Speaking of uncluttering your video experience, Unhook elegantly removes a bunch of distracting YouTube elements. 

Enjoy YouTube with more breathing room once Unhook removes all those “rabbit hole” temptations like related or recommended videos, trending content, homepage suggestions, user comments, and much more. Unhook features 20+ customization options. 

Minimal Theme for Twitter

Streamline your social media. Minimal Theme for Twitter offers a few new looks for a stripped down scrolling experience. 

Great features let you do things like… 

• Customize the dimensions of Twitter’s timeline and interface buttons 
• Remove promoted posts
• Hide unwanted elements like search bar, Tweet button, view counts & more
• “Writer” mode shows just the tweet composer, removing all other interface distractions

Link Gopher

Have you ever kept a web page open for days or maybe even weeks just because it contains a bunch of links you’ve been meaning to save and organize in some fashion, some day? Link Gopher can help. 

Simple but such a time saver — with a single click Link Gopher grabs all links from within a web page and sorts them in a new tab, so you can easily copy/paste anywhere for proper organization. Any duplicate links are automatically removed. 

OneTab

This is like an emergency escape hatch when you find yourself overwhelmed with open browser tabs. Click the toolbar button and OneTab grabs all of your open links and lists them on a single scrollable page. You’ll save a lot of CPU and memory once your previously open tabs go dormant on a listing page. 

OneTab is a simple and effective way of dealing with sudden tab overload. But if you need more robust tab management tools, you might be interested to check out these other great tab manager extensions. 

We hope some of these extensions help you achieve a less cluttered, more serene online experience. If you’d like to keep exploring, you can find thousands of extensions on addons.mozilla.org. 

YouTube wants you to experience YouTube in very prescribed ways. But with the right browser extension, you’re free to alter YouTube to taste. Change the way the site looks, behaves, and delivers your favorite videos. 

Enhancer for YouTube

With dozens of customization features, Enhancer for YouTube has the power to dramatically reorient the way you watch videos. 

While a bunch of customization options may seem overwhelming, Enhancer for YouTube actually makes it very simple to navigate its settings and select just your favorite features. You can even choose which of your preferred features will display in the extension’s easy access interface that appears just beneath the video player.

<figcaption class="wp-element-caption">Enhancer for YouTube offers easy access controls just beneath the video player.</figcaption>

Key features… 

• Customize video player size 
• Change YouTube’s look with a dark theme
• Volume booster
• Ad blocking (with ability to whitelist channels you OK for ads)
• Take quick screenshots of videos
• Change playback speed
• Set default video quality from low to high def
• Shortcut configuration

Return YouTube Dislike

Do you like the Dislike? YouTube removed the display that revealed the number of thumbs-down Dislikes a video has, but with Return YouTube Dislike you can bring back the brutal truth. 

“Does exactly what the name suggests. Can’t see myself without this extension. Seriously, bad move on YouTube for removing such a vital tool.”

Firefox user OFG

“i have never smashed 5 stars faster.”

Firefox user 12918016 YouTube High Definition

Though its primary function is to automatically play all YouTube videos in their highest possible resolution, YouTube High Definition has a few other fine features to offer. 

In addition to automatic HD, YouTube High Definition can…

• Customize video player size
• HD support for clips embedded on external sites
• Specify your ideal resolution (4k – 144p)
• Set a preferred volume level 
• Also automatically plays the highest quality audio

YouTube NonStop

So simple. So awesome. YouTube NonStop remedies the headache of interrupting your music with that awful “Video paused. Continue watching?” message. 

Works on YouTube and YouTube Music. You’re now free to navigate away from your YouTube tab for as long as you like and not fret that the rock will stop rolling. 

YouTube Audio

Another simple but great extension for music fans, YouTube Audio disables the video broadcast and just streams audio to save you a ton of bandwidth. 

This is an essential extension if you have limited internet bandwidth and only want the music anyway. Click YouTube Audio’s toolbar button to mute the video stream anytime you like. Also helps preserve battery life. 

Unhook: Remove YouTube Recommended Videos & Comments

Instant serenity for YouTube! Unhook lets you strip away unwanted distractions like the promotional sidebar, endscreen suggestions, trending tab, and much more. 

More than two dozen customization options make this an essential extension for anyone seeking escape from YouTube rabbit holes. You can even hide notifications and live chat boxes. 

“This is the best extension to control YouTube usage, and not let YouTube control you.”

Firefox user Shubham Mandiya PocketTube

If you subscribe to a lot of YouTube channels PocketTube is a fantastic way to organize all your subscriptions by themed collections. 

Group your channel collections by subject, like “Sports,” “Cooking,” “Cat videos” or whatever. Other key features include…

• Add custom icons to easily identify your channel collections
• Customize your feed so you just see videos you haven’t watched yet, prioritize videos from certain channels, plus other content settings
• Integrates seamlessly with YouTube homepage 
• Sync collections across Firefox/Android/iOS using Google Drive and Chrome Profiler

<figcaption class="wp-element-caption">PocketTube keeps your channel collections neatly tucked away to the side. </figcaption> AdBlocker for YouTube

It’s not just you who’s noticed a lot more ads lately. Regain control with AdBlocker for YouTube. 

The extension very simply and effectively removes both video and display ads from YouTube. Period. Enjoy a faster, more focused YouTube. 

SponsorBlock

It’s a terrible experience when you’re enjoying a video or music on YouTube and you’re suddenly interrupted by a blaring ad. SponsorBlock solves this problem in a highly effective and original way. 

Leveraging the power of crowd sourced information to locate where—precisely— interruptive sponsored segments appear in videos, SponsorBlock learns where to automatically skip sponsored segments with its ever growing database of videos. You can also participate in the project by reporting sponsored segments whenever you encounter them (it’s easy to report right there on the video page with the extension). 

SponsorBlock can also learn to skip non-music portions of music videos and intros/outros, as well. If you’d like a deeper dive of SponsorBlock we profiled its developer and open source project on Mozilla Distilled. 

We hope one of these extensions enhances the way you enjoy YouTube. Feel free to explore more great media extensions on addons.mozilla.org. 

 

During July I’ll be visiting family in Mongolia but I’ve also a few things that are very geeky that I want to do.

The first thing I want to do is plug the Ripe Atlas probes I have. It’s litle devices that look like that :

They enable anybody with a ripe atlas or ripe account to make measurements for dns queries and others. This helps making a global better internet. I have three of these probes I’d like to install. It’s good because last time I checked Mongolia didn’t have any active probe. These probes will also help Internet become better in Mongolia. I’ll need to buy some network cables before leaving because finding these in mongolia is going to be challenging. More on atlas at https://atlas.ripe.net/.

The second thing I intend to do is map Mongolia a bit better on two projects the first is related to Mozilla and maps gps coordinateswith wifi access point. Only a little part of The capital Ulaanbaatar is covered as per https://location.services.mozilla.com/map#11/47.8740/106.9485 I want this to be way more because having an open data source for this is important in the future. As mapping is my new thing I’ll probably edit Openstreetmap in order to make the urban parts of mongolia that I’ll visit way more usable on all the services that use OSM as a source of truth. There is already a project to map the capital city at http://hotosm.org/projects/mongolia_mapping_ulaanbaatar but I believe osm can server more than just 50% of mongolia’s population.

I got inspired to write this post by mu son this morning, look what he is doing at 17 months :

Last week I gave a talk at the Philly Tech Week 2015 Dev Day organized by the delightful people at technical.ly on some of the tricks/strategies we use in the Firefox OS Gaia Email app.  Note that the credit for implementing most of these techniques goes to the owner of the Email app’s front-end, James Burke.  Also, a special shout-out to Vivien for the initial DOM Worker patches for the email app.

I tried to avoid having slides that both I would be reading aloud as the audience read silently, so instead of slides to share, I have the talk script.  Well, I also have the slides here, but there’s not much to them.  The headings below are the content of the slides, except for the one time I inline some code.  Note that the live presentation must have differed slightly, because I’m sure I’m much more witty and clever in person than this script would make it seem…

Cover Slide: Who!

Hi, my name is Andrew Sutherland.  I work at Mozilla on the Firefox OS Email Application.  I’m here to share some strategies we used to make our HTML5 app Seem faster and sometimes actually Be faster.

What’s A Firefox OS (Screenshot Slide)

But first: What is a Firefox OS?  It’s a multiprocess Firefox gecko engine on an android linux kernel where all the apps including the system UI are implemented using HTML5, CSS, and JavaScript.  All the apps use some combination of standard web APIs and APIs that we hope to standardize in some form.

Here are some screenshots.  We’ve got the default home screen app, the clock app, and of course, the email app.

It’s an entirely client-side offline email application, supporting IMAP4, POP3, and ActiveSync.  The goal, like all Firefox OS apps shipped with the phone, is to give native apps on other platforms a run for their money.

And that begins with starting up fast.

Fast Startup: The Problems

But that’s frequently easier said than done.  Slow-loading websites are still very much a thing.

The good news for the email application is that a slow network isn’t one of its problems.  It’s pre-loaded on the phone.  And even if it wasn’t, because of the security implications of the TCP Web API and the difficulty of explaining this risk to users in a way they won’t just click through, any TCP-using app needs to be a cryptographically signed zip file approved by a marketplace.  So we do load directly from flash.

However, it’s not like flash on cellphones is equivalent to an infinitely fast, zero-latency network connection.  And even if it was, in a naive app you’d still try and load all of your HTML, CSS, and JavaScript at the same time because the HTML file would reference them all.  And that adds up.

It adds up in the form of event loop activity and competition with other threads and processes.  With the exception of Promises which get their own micro-task queue fast-lane, the web execution model is the same as all other UI event loops; events get scheduled and then executed in the same order they are scheduled.  Loading data from an asynchronous API like IndexedDB means that your read result gets in line behind everything else that’s scheduled.  And in the case of the bulk of shipped Firefox OS devices, we only have a single processor core so the thread and process contention do come into play.

So we try not to be a naive.

Seeming Fast at Startup: The HTML Cache

If we’re going to optimize startup, it’s good to start with what the user sees.  Once an account exists for the email app, at startup we display the default account’s inbox folder.

What is the least amount of work that we can do to show that?  Cache a screenshot of the Inbox.  The problem with that, of course, is that a static screenshot is indistinguishable from an unresponsive application.

So we did the next best thing, (which is) we cache the actual HTML we display.  At startup we load a minimal HTML file, our concatenated CSS, and just enough Javascript to figure out if we should use the HTML cache and then actually use it if appropriate.  It’s not always appropriate, like if our application is being triggered to display a compose UI or from a new mail notification that wants to show a specific message or a different folder.  But this is a decision we can make synchronously so it doesn’t slow us down.

Local Storage: Okay in small doses

We implement this by storing the HTML in localStorage.

Important Disclaimer!  LocalStorage is a bad API.  It’s a bad API because it’s synchronous.  You can read any value stored in it at any time, without waiting for a callback.  Which means if the data is not in memory the browser needs to block its event loop or spin a nested event loop until the data has been read from disk.  Browsers avoid this now by trying to preload the Entire contents of local storage for your origin into memory as soon as they know your page is being loaded.  And then they keep that information, ALL of it, in memory until your page is gone.

So if you store a megabyte of data in local storage, that’s a megabyte of data that needs to be loaded in its entirety before you can use any of it, and that hangs around in scarce phone memory.

To really make the point: do not use local storage, at least not directly.  Use a library like localForage that will use IndexedDB when available, and then fails over to WebSQLDatabase and local storage in that order.

Now, having sufficiently warned you of the terrible evils of local storage, I can say with a sorta-clear conscience… there are upsides in this very specific case.

The synchronous nature of the API means that once we get our turn in the event loop we can act immediately.  There’s no waiting around for an IndexedDB read result to gets its turn on the event loop.

This matters because although the concept of loading is simple from a User Experience perspective, there’s no standard to back it up right now.  Firefox OS’s UX desires are very straightforward.  When you tap on an app, we zoom it in.  Until the app is loaded we display the app’s icon in the center of the screen.  Unfortunately the standards are still assuming that the content is right there in the HTML.  This works well for document-based web pages or server-powered web apps where the contents of the page are baked in.  They work less well for client-only web apps where the content lives in a database and has to be dynamically retrieved.

The two events that exist are:

“DOMContentLoaded” fires when the document has been fully parsed and all scripts not tagged as “async” have run.  If there were stylesheets referenced prior to the script tags, the script tags will wait for the stylesheet loads.

“load” fires when the document has been fully loaded; stylesheets, images, everything.

But none of these have anything to do with the content in the page saying it’s actually done.  This matters because these standards also say nothing about IndexedDB reads or the like.  We tried to create a standards consensus around this, but it’s not there yet.  So Firefox OS just uses the “load” event to decide an app or page has finished loading and it can stop showing your app icon.  This largely avoids the dreaded “flash of unstyled content” problem, but it also means that your webpage or app needs to deal with this period of time by displaying a loading UI or just accepting a potentially awkward transient UI state.

(Trivial HTML slide)

<link rel=”stylesheet” ...> <script ...></script> DOMContentLoaded!

This is the important summary of our index.html.

We reference our stylesheet first.  It includes all of our styles.  We never dynamically load stylesheets because that compels a style recalculation for all nodes and potentially a reflow.  We would have to have an awful lot of style declarations before considering that.

Then we have our single script file.  Because the stylesheet precedes the script, our script will not execute until the stylesheet has been loaded.  Then our script runs and we synchronously insert our HTML from local storage.  Then DOMContentLoaded can fire.  At this point the layout engine has enough information to perform a style recalculation and determine what CSS-referenced image resources need to be loaded for buttons and icons, then those load, and then we’re good to be displayed as the “load” event can fire.

After that, we’re displaying an interactive-ish HTML document.  You can scroll, you can press on buttons and the :active state will apply.  So things seem real.

Being Fast: Lazy Loading and Optimized Layers

But now we need to try and get some logic in place as quickly as possible that will actually cash the checks that real-looking HTML UI is writing.  And the key to that is only loading what you need when you need it, and trying to get it to load as quickly as possible.

There are many module loading and build optimizing tools out there, and most frameworks have a preferred or required way of handling this.  We used the RequireJS family of Asynchronous Module Definition loaders, specifically the alameda loader and the r-dot-js optimizer.

One of the niceties of the loader plugin model is that we are able to express resource dependencies as well as code dependencies.

RequireJS Loader Plugins

var fooModule = require('./foo'); var htmlString = require('text!./foo.html'); var localizedDomNode = require('tmpl!./foo.html');

The standard Common JS loader semantics used by node.js and io.js are the first one you see here.  Load the module, return its exports.

But RequireJS loader plugins also allow us to do things like the second line where the exclamation point indicates that the load should occur using a loader plugin, which is itself a module that conforms to the loader plugin contract.  In this case it’s saying load the file foo.html as raw text and return it as a string.

But, wait, there’s more!  loader plugins can do more than that.  The third example uses a loader that loads the HTML file using the ‘text’ plugin under the hood, creates an HTML document fragment, and pre-localizes it using our localization library.  And this works un-optimized in a browser, no compilation step needed, but it can also be optimized.

So when our optimizer runs, it bundles up the core modules we use, plus, the modules for our “message list” card that displays the inbox.  And the message list card loads its HTML snippets using the template loader plugin.  The r-dot-js optimizer then locates these dependencies and the loader plugins also have optimizer logic that results in the HTML strings being inlined in the resulting optimized file.  So there’s just one single javascript file to load with no extra HTML file dependencies or other loads.

We then also run the optimizer against our other important cards like the “compose” card and the “message reader” card.  We don’t do this for all cards because it can be hard to carve up the module dependency graph for optimization without starting to run into cases of overlap where many optimized files redundantly include files loaded by other optimized files.

Plus, we have another trick up our sleeve:

Seeming Fast: Preloading

Preloading.  Our cards optionally know the other cards they can load.  So once we display a card, we can kick off a preload of the cards that might potentially be displayed.  For example, the message list card can trigger the compose card and the message reader card, so we can trigger a preload of both of those.

But we don’t go overboard with preloading in the frontend because we still haven’t actually loaded the back-end that actually does all the emaily email stuff.  The back-end is also chopped up into optimized layers along account type lines and online/offline needs, but the main optimized JS file still weighs in at something like 17 thousand lines of code with newlines retained.

So once our UI logic is loaded, it’s time to kick-off loading the back-end.  And in order to avoid impacting the responsiveness of the UI both while it loads and when we’re doing steady-state processing, we run it in a DOM Worker.

Being Responsive: Workers and SharedWorkers

DOM Workers are background JS threads that lack access to the page’s DOM, communicating with their owning page via message passing with postMessage.  Normal workers are owned by a single page.  SharedWorkers can be accessed via multiple pages from the same document origin.

By doing this, we stay out of the way of the main thread.  This is getting less important as browser engines support Asynchronous Panning & Zooming or “APZ” with hardware-accelerated composition, tile-based rendering, and all that good stuff.  (Some might even call it magic.)

When Firefox OS started, we didn’t have APZ, so any main-thread logic had the serious potential to result in janky scrolling and the impossibility of rendering at 60 frames per second.  It’s a lot easier to get 60 frames-per-second now, but even asynchronous pan and zoom potentially has to wait on dispatching an event to the main thread to figure out if the user’s tap is going to be consumed by app logic and preventDefault called on it.  APZ does this because it needs to know whether it should start scrolling or not.

And speaking of 60 frames-per-second…

Being Fast: Virtual List Widgets

…the heart of a mail application is the message list.  The expected UX is to be able to fling your way through the entire list of what the email app knows about and see the messages there, just like you would on a native app.

This is admittedly one of the areas where native apps have it easier.  There are usually list widgets that explicitly have a contract that says they request data on an as-needed basis.  They potentially even include data bindings so you can just point them at a data-store.

But HTML doesn’t yet have a concept of instantiate-on-demand for the DOM, although it’s being discussed by Firefox layout engine developers.  For app purposes, the DOM is a scene graph.  An extremely capable scene graph that can handle huge documents, but there are footguns and it’s arguably better to err on the side of fewer DOM nodes.

So what the email app does is we create a scroll-region div and explicitly size it based on the number of messages in the mail folder we’re displaying.  We create and render enough message summary nodes to cover the current screen, 3 screens worth of messages in the direction we’re scrolling, and then we also retain up to 3 screens worth in the direction we scrolled from.  We also pre-fetch 2 more screens worth of messages from the database.  These constants were arrived at experimentally on prototype devices.

We listen to “scroll” events and issue database requests and move DOM nodes around and update them as the user scrolls.  For any potentially jarring or expensive transitions such as coordinate space changes from new messages being added above the current scroll position, we wait for scrolling to stop.

Nodes are absolutely positioned within the scroll area using their ‘top’ style but translation transforms also work.  We remove nodes from the DOM, then update their position and their state before re-appending them.  We do this because the browser APZ logic tries to be clever and figure out how to create an efficient series of layers so that it can pre-paint as much of the DOM as possible in graphic buffers, AKA layers, that can be efficiently composited by the GPU.  Its goal is that when the user is scrolling, or something is being animated, that it can just move the layers around the screen or adjust their opacity or other transforms without having to ask the layout engine to re-render portions of the DOM.

When our message elements are added to the DOM with an already-initialized absolute position, the APZ logic lumps them together as something it can paint in a single layer along with the other elements in the scrolling region.  But if we start moving them around while they’re still in the DOM, the layerization logic decides that they might want to independently move around more in the future and so each message item ends up in its own layer.  This slows things down.  But by removing them and re-adding them it sees them as new with static positions and decides that it can lump them all together in a single layer.  Really, we could just create new DOM nodes, but we produce slightly less garbage this way and in the event there’s a bug, it’s nicer to mess up with 30 DOM nodes displayed incorrectly rather than 3 million.

But as neat as the layerization stuff is to know about on its own, I really mention it to underscore 2 suggestions:

1, Use a library when possible.  Getting on and staying on APZ fast-paths is not trivial, especially across browser engines.  So it’s a very good idea to use a library rather than rolling your own.

2, Use developer tools.  APZ is tricky to reason about and even the developers who write the Async pan & zoom logic can be surprised by what happens in complex real-world situations.  And there ARE developer tools available that help you avoid needing to reason about this.  Firefox OS has easy on-device developer tools that can help diagnose what’s going on or at least help tell you whether you’re making things faster or slower:

– it’s got a frames-per-second overlay; you do need to scroll like mad to get the system to want to render 60 frames-per-second, but it makes it clear what the net result is

– it has paint flashing that overlays random colors every time it paints the DOM into a layer.  If the screen is flashing like a discotheque or has a lot of smeared rainbows, you know something’s wrong because the APZ logic is not able to to just reuse its layers.

– devtools can enable drawing cool colored borders around the layers APZ has created so you can see if layerization is doing something crazy

There’s also fancier and more complicated tools in Firefox and other browsers like Google Chrome to let you see what got painted, what the layer tree looks like, et cetera.

And that’s my spiel.

Links

The source code to Gaia can be found at https://github.com/mozilla-b2g/gaia

The email app in particular can be found at https://github.com/mozilla-b2g/gaia/tree/master/apps/email

(I also asked for questions here.)

It was brought to my attention recently by reputable sources that the recent announcement of increased usage in recent years produced an internal firestorm within Mozilla. Key figures raised alarm that some of the tech press had interpreted the blog post as a sign that Thunderbird was not, in fact, dead. As a result, they asked Thunderbird community members to make corrections to emphasize that Mozilla was trying to kill Thunderbird.

The primary fear, it seems, is that knowledge that the largest open-source email client was still receiving regular updates would impel its userbase to agitate for increased funding and maintenance of the client to help forestall potential threats to the open nature of email as well as to innovate in the space of providing usable and private communication channels. Such funding, however, would be an unaffordable luxury and would only distract Mozilla from its central goal of building developer productivity tooling. Persistent rumors that Mozilla would be willing to fund Thunderbird were it renamed Firefox Email were finally addressed with the comment, "such a renaming would violate our current policy that all projects be named Persona."

This post is part 8 of an intermittent series exploring the difficulties of writing an email client. Part 1 describes a brief history of the infrastructure. Part 2 discusses internationalization. Part 3 discusses MIME. Part 4 discusses email addresses. Part 5 discusses the more general problem of email headers. Part 6 discusses how email security works in practice. Part 7 discusses the problem of trust. This part discusses why email security has largely failed.

At the end of the last part in this series, I posed the question, "Which email security protocol is most popular?" The answer to the question is actually neither S/MIME nor PGP, but a third protocol, DKIM. I haven't brought up DKIM until now because DKIM doesn't try to secure email in the same vein as S/MIME or PGP, but I still consider it relevant to discussing email security.

Unquestionably, DKIM is the only security protocol for email that can be considered successful. There are perhaps 4 billion active email addresses [1]. Of these, about 1-2 billion use DKIM. In contrast, S/MIME can count a few million users, and PGP at best a few hundred thousand. No other security protocols have really caught on past these three. Why did DKIM succeed where the others fail?

DKIM's success stems from its relatively narrow focus. It is nothing more than a cryptographic signature of the message body and a smattering of headers, and is itself stuck in the DKIM-Signature header. It is meant to be applied to messages only on outgoing servers and read and processed at the recipient mail server—it completely bypasses clients. That it bypasses clients allows it to solve the problem of key discovery and key management very easily (public keys are stored in DNS, which is already a key part of mail delivery), and its role in spam filtering is strong motivation to get it implemented quickly (it is 7 years old as of this writing). It's also simple: this one paragraph description is basically all you need to know [2].

The failure of S/MIME and PGP to see large deployment is certainly a large topic of discussion on myriads of cryptography enthusiast mailing lists, which often like to partake in propositions of new end-to-end encryption of email paradigms, such as the recent DIME proposal. Quite frankly, all of these solutions suffer broadly from at least the same 5 fundamental weaknesses, and I see it unlikely that a protocol will come about that can fix these weaknesses well enough to become successful.

The first weakness, and one I've harped about many times already, is UI. Most email security UI is abysmal and generally at best usable only by enthusiasts. At least some of this is endemic to security: while it mean seem obvious how to convey what an email signature or an encrypted email signifies, how do you convey the distinctions between sign-and-encrypt, encrypt-and-sign, or an S/MIME triple wrap? The Web of Trust model used by PGP (and many other proposals) is even worse, in that inherently requires users to do other actions out-of-band of email to work properly.

Trust is the second weakness. Consider that, for all intents and purposes, the email address is the unique identifier on the Internet. By extension, that implies that a lot of services are ultimately predicated on the notion that the ability to receive and respond to an email is a sufficient means to identify an individual. However, the entire purpose of secure email, or at least of end-to-end encryption, is subtly based on the fact that other people in fact have access to your mailbox, thus destroying the most natural ways to build trust models on the Internet. The quest for anonymity or privacy also renders untenable many other plausible ways to establish trust (e.g., phone verification or government-issued ID cards).

Key discovery is another weakness, although it's arguably the easiest one to solve. If you try to keep discovery independent of trust, the problem of key discovery is merely picking a protocol to publish and another one to find keys. Some of these already exist: PGP key servers, for example, or using DANE to publish S/MIME or PGP keys.

Key management, on the other hand, is a more troubling weakness. S/MIME, for example, basically works without issue if you have a certificate, but managing to get an S/MIME certificate is a daunting task (necessitated, in part, by its trust model—see how these issues all intertwine?). This is also where it's easy to say that webmail is an unsolvable problem, but on further reflection, I'm not sure I agree with that statement anymore. One solution is just storing the private key with the webmail provider (you're trusting them as an email client, after all), but it's also not impossible to imagine using phones or flash drives as keystores. Other key management factors are more difficult to solve: people who lose their private keys or key rollover create thorny issues. There is also the difficulty of managing user expectations: if I forget my password to most sites (even my email provider), I can usually get it reset somehow, but when a private key is lost, the user is totally and completely out of luck.

Of course, there is one glaring and almost completely insurmountable problem. Encrypted email fundamentally precludes certain features that we have come to take for granted. The lesser known is server-side search and filtration. While there exist some mechanisms to do search on encrypted text, those mechanisms rely on the fact that you can manipulate the text to change the message, destroying the integrity feature of secure email. They also tend to be fairly expensive. It's easy to just say "who needs server-side stuff?", but the contingent of people who do email on smartphones would not be happy to have to pay the transfer rates to download all the messages in their folder just to find one little email, nor the energy costs of doing it on the phone. And those who have really large folders—Fastmail has a design point of 1,000,000 in a single folder—would still prefer to not have to transfer all their mail even on desktops.

The more well-known feature that would disappear is spam filtration. Consider that 90% of all email is spam, and if you think your spam folder is too slim for that to be true, it's because your spam folder only contains messages that your email provider wasn't sure were spam. The loss of server-side spam filtering would dramatically increase the cost of spam (a 10% reduction in efficiency would double the amount of server storage, per my calculations), and client-side spam filtering is quite literally too slow [3] and too costly (remember smartphones? Imagine having your email take 10 times as much energy and bandwidth) to be a tenable option. And privacy or anonymity tends to be an invitation to abuse (cf. Tor and Wikipedia). Proposed solutions to the spam problem are so common that there is a checklist containing most of the objections.

When you consider all of those weaknesses, it is easy to be pessimistic about the possibility of wide deployment of powerful email security solutions. The strongest future—all email is encrypted, including metadata—is probably impossible or at least woefully impractical. That said, if you weaken some of the assumptions (say, don't desire all or most traffic to be encrypted), then solutions seem possible if difficult.

This concludes my discussion of email security, at least until things change for the better. I don't have a topic for the next part in this series picked out (this part actually concludes the set I knew I wanted to discuss when I started), although OAuth and DMARC are two topics that have been bugging me enough recently to consider writing about. They also have the unfortunate side effect of being things likely to see changes in the near future, unlike most of the topics I've discussed so far. But rest assured that I will find more difficulties in the email infrastructure to write about before long!

[1] All of these numbers are crude estimates and are accurate to only an order of magnitude. To justify my choices: I assume 1 email address per Internet user (this overestimates the developing world and underestimates the developed world). The largest webmail providers have given numbers that claim to be 1 billion active accounts between them, and all of them use DKIM. S/MIME is guessed by assuming that any smartcard deployment supports S/MIME, and noting that the US Department of Defense and Estonia's digital ID project are both heavy users of such smartcards. PGP is estimated from the size of the strong set and old numbers on the reachable set from the core Web of Trust.
[2] Ever since last April, it's become impossible to mention DKIM without referring to DMARC, as a result of Yahoo's controversial DMARC policy. A proper discussion of DMARC (and why what Yahoo did was controversial) requires explaining the mail transmission architecture and spam, however, so I'll defer that to a later post. It's also possible that changes in this space could happen within the next year.
[3] According to a former GMail spam employee, if it takes you as long as three minutes to calculate reputation, the spammer wins.

Several years back, Ehsan and Jeff Muizelaar attempted to build a unified history of mozilla-central across the Mercurial era and the CVS era. Their result is now used in the gecko-dev repository. While being distracted on yet another side project, I thought that I might want to do the same for comm-central. It turns out that building a unified history for comm-central makes mozilla-central look easy: mozilla-central merely had one import from CVS. In contrast, comm-central imported twice from CVS (the calendar code came later), four times from mozilla-central (once with converted history), and imported twice from Instantbird's repository (once with converted history). Three of those conversions also involved moving paths. But I've worked through all of those issues to provide a nice snapshot of the repository [1]. And since I've been frustrated by failing to find good documentation on how this sort of process went for mozilla-central, I'll provide details on the process for comm-central.

The first step and probably the hardest is getting the CVS history in DVCS form (I use hg because I'm more comfortable it, but there's effectively no difference between hg, git, or bzr here). There is a git version of mozilla's CVS tree available, but I've noticed after doing research that its last revision is about a month before the revision I need for Calendar's import. The documentation for how that repo was built is no longer on the web, although we eventually found a copy after I wrote this post on git.mozilla.org. I tried doing another conversion using hg convert to get CVS tags, but that rudely blew up in my face. For now, I've filed a bug on getting an official, branchy-and-tag-filled version of this repository, while using the current lack of history as a base. Calendar people will have to suffer missing a month of history.

CVS is famously hard to convert to more modern repositories, and, as I've done my research, Mozilla's CVS looks like it uses those features which make it difficult. In particular, both the calendar CVS import and the comm-central initial CVS import used a CVS tag HG_COMM_INITIAL_IMPORT. That tagging was done, on only a small portion of the tree, twice, about two months apart. Fortunately, mailnews code was never touched on CVS trunk after the import (there appears to be one commit on calendar after the tagging), so it is probably possible to salvage a repository-wide consistent tag.

The start of my script for conversion looks like this:

#!/bin/bash set -e WORKDIR=/tmp HGCVS=$WORKDIR/mozilla-cvs-history MC=/src/trunk/mozilla-central CC=/src/trunk/comm-central OUTPUT=$WORKDIR/full-c-c # Bug 445146: m-c/editor/ui -> c-c/editor/ui MC_EDITOR_IMPORT=d8064eff0a17372c50014ee305271af8e577a204 # Bug 669040: m-c/db/mork -> c-c/db/mork MC_MORK_IMPORT=f2a50910befcf29eaa1a29dc088a8a33e64a609a # Bug 1027241, bug 611752 m-c/security/manager/ssl/** -> c-c/mailnews/mime/src/* MC_SMIME_IMPORT=e74c19c18f01a5340e00ecfbc44c774c9a71d11d # Step 0: Grab the mozilla CVS history. if [ ! -e $HGCVS ]; then hg clone git+https://github.com/jrmuizel/mozilla-cvs-history.git $HGCVS fi

Since I don't want to include the changesets useless to comm-central history, I trimmed the history by using hg convert to eliminate changesets that don't change the necessary files. Most of the files are simple directory-wide changes, but S/MIME only moved a few files over, so it requires a more complex way to grab the file list. In addition, I also replaced the % in the usernames with @ that they are used to appearing in hg. The relevant code is here:

# Step 1: Trim mozilla CVS history to include only the files we are ultimately # interested in. cat >$WORKDIR/convert-filemap.txt <<EOF # Revision e4f4569d451a include directory/xpcom include mail include mailnews include other-licenses/branding/thunderbird include suite # Revision 7c0bfdcda673 include calendar include other-licenses/branding/sunbird # Revision ee719a0502491fc663bda942dcfc52c0825938d3 include editor/ui # Revision 52efa9789800829c6f0ee6a005f83ed45a250396 include db/mork/ include db/mdb/ EOF # Add the S/MIME import files hg -R $MC log -r "children($MC_SMIME_IMPORT)" \ --template "{file_dels % 'include {file}\n'}" >>$WORKDIR/convert-filemap.txt if [ ! -e $WORKDIR/convert-authormap.txt ]; then hg -R $HGCVS log --template "{email(author)}={sub('%', '@', email(author))}\n" \ | sort -u > $WORKDIR/convert-authormap.txt fi cd $WORKDIR hg convert $HGCVS $OUTPUT --filemap convert-filemap.txt -A convert-authormap.txt

That last command provides us the subset of the CVS history that we need for unified history. Strictly speaking, I should be pulling a specific revision, but I happen to know that there's no need to (we're cloning the only head) in this case. At this point, we now need to pull in the mozilla-central changes before we pull in comm-central. Order is key; hg convert will only apply the graft points when converting the child changeset (which it does but once), and it needs the parents to exist before it can do that. We also need to ensure that the mozilla-central graft point is included before continuing, so we do that, and then pull mozilla-central:

CC_CVS_BASE=$(hg log -R $HGCVS -r 'tip' --template '{node}') CC_CVS_BASE=$(grep $CC_CVS_BASE $OUTPUT/.hg/shamap | cut -d' ' -f2) MC_CVS_BASE=$(hg log -R $HGCVS -r 'gitnode(215f52d06f4260fdcca797eebd78266524ea3d2c)' --template '{node}') MC_CVS_BASE=$(grep $MC_CVS_BASE $OUTPUT/.hg/shamap | cut -d' ' -f2) # Okay, now we need to build the map of revisions. cat >$WORKDIR/convert-revmap.txt <<EOF e4f4569d451a5e0d12a6aa33ebd916f979dd8faa $CC_CVS_BASE # Thunderbird / Suite 7c0bfdcda6731e77303f3c47b01736aaa93d5534 d4b728dc9da418f8d5601ed6735e9a00ac963c4e, $CC_CVS_BASE # Calendar 9b2a99adc05e53cd4010de512f50118594756650 $MC_CVS_BASE # Mozilla graft point ee719a0502491fc663bda942dcfc52c0825938d3 78b3d6c649f71eff41fe3f486c6cc4f4b899fd35, $MC_EDITOR_IMPORT # Editor 8cdfed92867f885fda98664395236b7829947a1d 4b5da7e5d0680c6617ec743109e6efc88ca413da, e4e612fcae9d0e5181a5543ed17f705a83a3de71 # Chat EOF # Next, import mozilla-central revisions for rev in $MC_MORK_IMPORT $MC_EDITOR_IMPORT $MC_SMIME_IMPORT; do hg convert $MC $OUTPUT -r $rev --splicemap $WORKDIR/convert-revmap.txt \ --filemap $WORKDIR/convert-filemap.txt done

Some notes about all of the revision ids in the script. The splicemap requires the full 40-character SHA ids; anything less and the thing complains. I also need to specify the parents of the revisions that deleted the code for the mozilla-central import, so if you go hunting for those revisions and are surprised that they don't remove the code in question, that's why.

I mentioned complications about the merges earlier. The Mork and S/MIME import codes here moved files, so that what was db/mdb in mozilla-central became db/mork. There's no support for causing the generated splice to record these as a move, so I have to manually construct those renamings:

# We need to execute a few hg move commands due to renamings. pushd $OUTPUT hg update -r $(grep $MC_MORK_IMPORT .hg/shamap | cut -d' ' -f2) (hg -R $MC log -r "children($MC_MORK_IMPORT)" \ --template "{file_dels % 'hg mv {file} {sub(\"db/mdb\", \"db/mork\", file)}\n'}") | bash hg commit -m 'Pseudo-changeset to move Mork files' -d '2011-08-06 17:25:21 +0200' MC_MORK_IMPORT=$(hg log -r tip --template '{node}') hg update -r $(grep $MC_SMIME_IMPORT .hg/shamap | cut -d' ' -f2) (hg -R $MC log -r "children($MC_SMIME_IMPORT)" \ --template "{file_dels % 'hg mv {file} {sub(\"security/manager/ssl\", \"mailnews/mime\", file)}\n'}") | bash hg commit -m 'Pseudo-changeset to move S/MIME files' -d '2014-06-15 20:51:51 -0700' MC_SMIME_IMPORT=$(hg log -r tip --template '{node}') popd # Echo the new move commands to the changeset conversion map. cat >>$WORKDIR/convert-revmap.txt <<EOF 52efa9789800829c6f0ee6a005f83ed45a250396 abfd23d7c5042bc87502506c9f34c965fb9a09d1, $MC_MORK_IMPORT # Mork 50f5b5fc3f53c680dba4f237856e530e2097adfd 97253b3cca68f1c287eb5729647ba6f9a5dab08a, $MC_SMIME_IMPORT # S/MIME EOF

Now that we have all of the graft points defined, and all of the external code ready, we can pull comm-central and do the conversion. That's not quite it, though—when we graft the S/MIME history to the original mozilla-central history, we have a small segment of abandoned converted history. A call to hg strip removes that.

# Now, import comm-central revisions that we need hg convert $CC $OUTPUT --splicemap $WORKDIR/convert-revmap.txt hg strip 2f69e0a3a05a

[1] I left out one of the graft points because I just didn't want to deal with it. I'll leave it as an exercise to the reader to figure out which one it was. Hint: it's the only one I didn't know about before I searched for the archive points [2].
[2] Since I wasn't sure I knew all of the graft points, I decided to try to comb through all of the changesets to figure out who imported code. It turns out that hg log -r 'adds("**")' narrows it down nicely (1667 changesets to look at instead of 17547), and using the {file_adds} template helps winnow it down more easily.

In an xpcshell test, I recently needed a way to monitor all network requests and access both request and response data so I can save them for later use. This required a little bit of digging in Mozilla’s devtools code so I thought I’d write a short blog post about it.

This code will be used in a testcase that ensures that calendar providers in Lightning function properly. In the case of the CalDAV provider, we would need to access a real server for testing. We can’t just set up a few servers and use them for testing, it would end in an unreasonable amount of server maintenance. Given non-local connections are not allowed when running the tests on the Mozilla build infrastructure, it wouldn’t work anyway. The solution is to create a fakeserver, that is able to replay the requests in the same way. Instead of manually making the requests and figuring out how the server replies, we can use this code to quickly collect all the requests we need.

Without further delay, here is the code you have been waiting for:

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/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ var allRequests = []; /** * Add the following function as a request observer: * Services.obs.addObserver(httpObserver, "http-on-examine-response", false); * * When done listening on requests: * dump(allRequests.join("\n===\n")); // print them * dump(JSON.stringify(allRequests, null, " ")) // jsonify them */ function httpObserver(aSubject, aTopic, aData) { if (aSubject instanceof Components.interfaces.nsITraceableChannel) { let request = new TracedRequest(aSubject); request._next = aSubject.setNewListener(request); allRequests.push(request); } } /** * This is the object that represents a request/response and also collects the data for it * * @param aSubject The channel from the response observer. */ function TracedRequest(aSubject) { let httpchannel = aSubject.QueryInterface(Components.interfaces.nsIHttpChannel); let self = this; this.requestHeaders = Object.create(null); httpchannel.visitRequestHeaders({ visitHeader: function(k, v) { self.requestHeaders[k] = v; } }); this.responseHeaders = Object.create(null); httpchannel.visitResponseHeaders({ visitHeader: function(k, v) { self.responseHeaders[k] = v; } }); this.uri = aSubject.URI.spec; this.method = httpchannel.requestMethod; this.requestBody = readRequestBody(aSubject); this.responseStatus = httpchannel.responseStatus; this.responseStatusText = httpchannel.responseStatusText; this._chunks = []; } TracedRequest.prototype = { uri: null, method: null, requestBody: null, requestHeaders: null, responseStatus: null, responseStatusText: null, responseHeaders: null, responseBody: null, toJSON: function() { let j = Object.create(null); for (let m of Object.keys(this)) { if (typeof this[m] != "function" && m[0] != "_") { j[m] = this[m]; } } return j; }, onStartRequest: function(aRequest, aContext) this._next.onStartRequest(aRequest, aContext), onStopRequest: function(aRequest, aContext, aStatusCode) { this.responseBody = this._chunks.join(""); this._chunks = null; this._next.onStopRequest(aRequest, aContext, aStatusCode); this._next = null; }, onDataAvailable: function(aRequest, aContext, aStream, aOffset, aCount) { let binaryInputStream = Components.classes["@mozilla.org/binaryinputstream;1"] .createInstance(Components.interfaces.nsIBinaryInputStream); let storageStream = Components.classes["@mozilla.org/storagestream;1"] .createInstance(Components.interfaces.nsIStorageStream); let outStream = Components.classes["@mozilla.org/binaryoutputstream;1"] .createInstance(Components.interfaces.nsIBinaryOutputStream); binaryInputStream.setInputStream(aStream); storageStream.init(8192, aCount, null); outStream.setOutputStream(storageStream.getOutputStream(0)); let data = binaryInputStream.readBytes(aCount); this._chunks.push(data); outStream.writeBytes(data, aCount); this._next.onDataAvailable(aRequest, aContext, storageStream.newInputStream(0), aOffset, aCount); }, toString: function() { let str = this.method + " " + this.uri; for (let hdr of Object.keys(this.requestHeaders)) { str += hdr + ": " + this.requestHeaders[hdr] + "\n"; } if (this.requestBody) { str += "\r\n" + this.requestBody + "\n"; } str += "\n" + this.responseStatus + " " + this.responseStatusText if (this.responseBody) { str += "\r\n" + this.responseBody + "\n"; } return str; } }; // Taken from: // http://hg.mozilla.org/mozilla-central/file/2399d1ae89e9/toolkit/devtools/webconsole/network-helper.js#l120 function readRequestBody(aRequest, aCharset="UTF-8") { let text = null; if (aRequest instanceof Ci.nsIUploadChannel) { let iStream = aRequest.uploadStream; let isSeekableStream = false; if (iStream instanceof Ci.nsISeekableStream) { isSeekableStream = true; } let prevOffset; if (isSeekableStream) { prevOffset = iStream.tell(); iStream.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0); } // Read data from the stream. try { let rawtext = NetUtil.readInputStreamToString(iStream, iStream.available()) let conv = Components.classes["@mozilla.org/intl/scriptableunicodeconverter"] .createInstance(Components.interfaces.nsIScriptableUnicodeConverter); conv.charset = aCharset; text = conv.ConvertToUnicode(rawtext); } catch (err) { } // Seek locks the file, so seek to the beginning only if necko hasn't // read it yet, since necko doesn't eek to 0 before reading (at lest // not till 459384 is fixed). if (isSeekableStream && prevOffset == 0) { iStream.seek(Components.interfaces.nsISeekableStream.NS_SEEK_SET, 0); } } return text; }

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Over the years I’ve organized or tried to organize pgp key signing parties every time I go somewhere. I the last year I’ve organized 3 that were successful (eg with more then 10 attendees).

1. Have a venue

I’ve tried a bunch of times to have people show up at the hotel I was staying in the morning - that doesn’t work. Having catering at the venues is even better, it will encourage people to come from far away (or long distance commute). Try to show the path in the venues with signs (paper with PGP key signing party and arrows help).

2. Date and time

Meeting in the evening after work works better ( after 18 or 18:30 works better).

Let people know how long it will take (count 1 hour/per 30 participants).

3. Make people sign up

That makes people think twice before saying they will attend. It’s also an easy way for you to know how much beer/cola/ etc.. you’ll need to provide if you cater food.

I’ve been using eventbrite to manage attendance at my last three meeting it let’s me :

• know who is coming
• Mass mail participants
• have them have a calendar reminder

4 Reach out

For such a party you need people to attend so you need to reach out.

I always start by a search on biglumber.com to find who are the people using gpg registered on that site for the area I’m visiting (see below on what I send).

Then I look for local linux users groups / *BSD groups  and send an announcement to them with :

• date
• venue
• link to eventbrite and why I use it
• ask them to forward (they know the area better than you)
• I also use lanyrd and twitter but I’m not convinced that it works.

for my last announcement it looked like this :

Subject: GnuPG / PGP key signing party September 26 2014 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="t01Mpe56TgLc7mgHKVMajjwkqQdw8XvI4" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --t01Mpe56TgLc7mgHKVMajjwkqQdw8XvI4 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hello my name is ludovic, I'm a sysadmins at mozilla working remote from europe. I've been involved with Thunderbird a lot (and still am). I'm organizing a pgp Key signing party in the Mozilla san francisco office on September the 26th 2014 from 6PM to 8PM. For security and assurances reasons I need to count how many people will attend. I'v setup a eventbrite for that at https://www.eventbrite.com/e/gnupg-pgp-key-signing-party-making-the-web-o= f-trust-stronger-tickets-12867542165 (please take one ticket if you think about attending - If you change you mind cancel so more people can come). I will use the eventbrite tool to send reminders and I will try to make a list with keys and fingerprint before the event to make things more manageable (but I don't promise). for those using lanyrd you will be able to use http://lanyrd.com/ccckzw. Ludovic ps sent to buug.org,nblug.org end penlug.org - please feel free to post where appropriate ( the more the meerier, the stronger the web of trust).= ps2 I have contacted people listed on biglumber to have more gpg related people show up. --=20 [:Usul] MOC Team at Mozilla QA Lead fof Thunderbird http://sietch-tabr.tumblr.com/ - http://weusepgp.info/ 5. Make it easy to attend

As noted above making a list of participants to hand out helps a lot (I’ve used http://www.phildev.net/pius/ and my own stuff to make a list). It make it easier for you, for attendees. Tell people what they need to bring (IDs, pen, printed fingerprints if you don’t provide a list).

6. Send reminders

Send people reminder and let them know how many people intend to show up. It boosts audience.

I’m organizing a pgp Keysigning party in the Mozilla san francisco office on September the 26th 2014 from 6PM to 8PM.

For security and assurances reasons I need to count how many people will attend. I’ve setup a eventbrite for that at https://www.eventbrite.com/e/gnupg-pgp-key-signing-party-making-the-web-of-trust-stronger-tickets-12867542165 (please take one ticket if you think about attending - If you change you mind cancel so more people can come).

I will use the eventbrite tool to send reminders and I will try to make a list with keys and fingerprint before the event to make things more manageable (but I don’t promise).

For those using lanyrd you will be able to use http://lanyrd.com/ccckzw.(Please tweet the event to get more people in).

This post is part 7 of an intermittent series exploring the difficulties of writing an email client. Part 1 describes a brief history of the infrastructure. Part 2 discusses internationalization. Part 3 discusses MIME. Part 4 discusses email addresses. Part 5 discusses the more general problem of email headers. Part 6 discusses how email security works in practice. This part discusses the problem of trust.

At a technical level, S/MIME and PGP (or at least PGP/MIME) use cryptography essentially identically. Yet the two are treated as radically different models of email security because they diverge on the most important question of public key cryptography: how do you trust the identity of a public key? Trust is critical, as it is the only way to stop an active, man-in-the-middle (MITM) attack. MITM attacks are actually easier to pull off in email, since all email messages effectively have to pass through both the sender's and the recipients' email servers [1], allowing attackers to be able to pull off permanent, long-lasting MITM attacks [2].

S/MIME uses the same trust model that SSL uses, based on X.509 certificates and certificate authorities. X.509 certificates effectively work by providing a certificate that says who you are which is signed by another authority. In the original concept (as you might guess from the name "X.509"), the trusted authority was your telecom provider, and the certificates were furthermore intended to be a part of the global X.500 directory—a natural extension of the OSI internet model. The OSI model of the internet never gained traction, and the trusted telecom providers were replaced with trusted root CAs.

PGP, by contrast, uses a trust model that's generally known as the Web of Trust. Every user has a PGP key (containing their identity and their public key), and users can sign others' public keys. Trust generally flows from these signatures: if you trust a user, you know the keys that they sign are correct. The name "Web of Trust" comes from the vision that trust flows along the paths of signatures, building a tight web of trust.

And now for the controversial part of the post, the comparisons and critiques of these trust models. A disclaimer: I am not a security expert, although I am a programmer who revels in dreaming up arcane edge cases. I also don't use PGP at all, and use S/MIME to a very limited extent for some Mozilla work [3], although I did try a few abortive attempts to dogfood it in the past. I've attempted to replace personal experience with comprehensive research [4], but most existing critiques and comparisons of these two trust models are about 10-15 years old and predate several changes to CA certificate practices.

A basic tenet of development that I have found is that the average user is fairly ignorant. At the same time, a lot of the defense of trust models, both CAs and Web of Trust, tends to hinge on configurability. How many people, for example, know how to add or remove a CA root from Firefox, Windows, or Android? Even among the subgroup of Mozilla developers, I suspect the number of people who know how to do so are rather few. Or in the case of PGP, how many people know how to change the maximum path length? Or even understand the security implications of doing so?

Seen in the light of ignorant users, the Web of Trust is a UX disaster. Its entire security model is predicated on having users precisely specify how much they trust other people to trust others (ultimate, full, marginal, none, unknown) and also on having them continually do out-of-band verification procedures and publicly reporting those steps. In 1998, a seminal paper on the usability of a GUI for PGP encryption came to the conclusion that the UI was effectively unusable for users, to the point that only a third of the users were able to send an encrypted email (and even then, only with significant help from the test administrators), and a quarter managed to publicly announce their private keys at some point, which is pretty much the worst thing you can do. They also noted that the complex trust UI was never used by participants, although the failure of many users to get that far makes generalization dangerous [5]. While newer versions of security UI have undoubtedly fixed many of the original issues found (in no small part due to the paper, one of the first to argue that usability is integral, not orthogonal, to security), I have yet to find an actual study on the usability of the trust model itself.

The Web of Trust has other faults. The notion of "marginal" trust it turns out is rather broken: if you marginally trust a user who has two keys who both signed another person's key, that's the same as fully trusting a user with one key who signed that key. There are several proposals for different trust formulas [6], but none of them have caught on in practice to my knowledge.

A hidden fault is associated with its manner of presentation: in sharp contrast to CAs, the Web of Trust appears to not delegate trust, but any practical widespread deployment needs to solve the problem of contacting people who have had no prior contact. Combined with the need to bootstrap new users, this implies that there needs to be some keys that have signed a lot of other keys that are essentially default-trusted—in other words, a CA, a fact sometimes lost on advocates of the Web of Trust.

That said, a valid point in favor of the Web of Trust is that it more easily allows people to distrust CAs if they wish to. While I'm skeptical of its utility to a broader audience, the ability to do so for is crucial for a not-insignificant portion of the population, and it's important enough to be explicitly called out.

X.509 certificates are most commonly discussed in the context of SSL/TLS connections, so I'll discuss them in that context as well, as the implications for S/MIME are mostly the same. Almost all criticism of this trust model essentially boils down to a single complaint: certificate authorities aren't trustworthy. A historical criticism is that the addition of CAs to the main root trust stores was ad-hoc. Since then, however, the main oligopoly of these root stores (Microsoft, Apple, Google, and Mozilla) have made their policies public and clear [7]. The introduction of the CA/Browser Forum in 2005, with a collection of major CAs and the major browsers as members, and several [8] helps in articulating common policies. These policies, simplified immensely, boil down to:

1. You must verify information (depending on certificate type). This information must be relatively recent.
2. You must not use weak algorithms in your certificates (e.g., no MD5).
3. You must not make certificates that are valid for too long.
4. You must maintain revocation checking services.
5. You must have fairly stringent physical and digital security practices and intrusion detection mechanisms.
6. You must be [externally] audited every year that you follow the above rules.
7. If you screw up, we can kick you out.

I'm not going to claim that this is necessarily the best policy or even that any policy can feasibly stop intrusions from happening. But it's a policy, so CAs must abide by some set of rules.

Another CA criticism is the fear that they may be suborned by national government spy agencies. I find this claim underwhelming, considering that the number of certificates acquired by intrusions that were used in the wild is larger than the number of certificates acquired by national governments that were used in the wild: 1 and 0, respectively. Yet no one complains about the untrustworthiness of CAs due to their ability to be hacked by outsiders. Another attack is that CAs are controlled by profit-seeking corporations, which misses the point because the business of CAs is not selling certificates but selling their access to the root databases. As we will see shortly, jeopardizing that access is a great way for a CA to go out of business.

To understand issues involving CAs in greater detail, there are two CAs that are particularly useful to look at. The first is CACert. CACert is favored by many by its attempt to handle X.509 certificates in a Web of Trust model, so invariably every public discussion about CACert ends up devolving into an attack on other CAs for their perceived capture by national governments or corporate interests. Yet what many of the proponents for inclusion of CACert miss (or dismiss) is the fact that CACert actually failed the required audit, and it is unlikely to ever pass an audit. This shows a central failure of both CAs and Web of Trust: different people have different definitions of "trust," and in the case of CACert, some people are favoring a subjective definition (I trust their owners because they're not evil) when an objective definition fails (in this case, that the root signing key is securely kept).

The other CA of note here is DigiNotar. In July 2011, some hackers managed to acquire a few fraudulent certificates by hacking into DigiNotar's systems. By late August, people had become aware of these certificates being used in practice [9] to intercept communications, mostly in Iran. The use appears to have been caught after Chromium updates failed due to invalid certificate fingerprints. After it became clear that the fraudulent certificates were not limited to a single fake Google certificate, and that DigiNotar had failed to notify potentially affected companies of its breach, DigiNotar was swiftly removed from all of the trust databases. It ended up declaring bankruptcy within two weeks.

DigiNotar indicates several things. One, SSL MITM attacks are not theoretical (I have seen at least two or three security experts advising pre-DigiNotar that SSL MITM attacks are "theoretical" and therefore the wrong target for security mechanisms). Two, keeping the trust of browsers is necessary for commercial operation of CAs. Three, the notion that a CA is "too big to fail" is false: DigiNotar played an important role in the Dutch community as a major CA and the operator of Staat der Nederlanden. Yet when DigiNotar screwed up and lost its trust, it was swiftly kicked out despite this role. I suspect that even Verisign could be kicked out if it manages to screw up badly enough.

This isn't to say that the CA model isn't problematic. But the source of its problems is that delegating trust isn't a feasible model in the first place, a problem that it shares with the Web of Trust as well. Different notions of what "trust" actually means and the uncertainty that gets introduced as chains of trust get longer both make delegating trust weak to both social engineering and technical engineering attacks. There appears to be an increasing consensus that the best way forward is some variant of key pinning, much akin to how SSH works: once you know someone's public key, you complain if that public key appears to change, even if it appears to be "trusted." This does leave people open to attacks on first use, and the question of what to do when you need to legitimately re-key is not easy to solve.

In short, both CAs and the Web of Trust have issues. Whether or not you should prefer S/MIME or PGP ultimately comes down to the very conscious question of how you want to deal with trust—a question without a clear, obvious answer. If I appear to be painting CAs and S/MIME in a positive light and the Web of Trust and PGP in a negative one in this post, it is more because I am trying to focus on the positions less commonly taken to balance perspective on the internet. In my next post, I'll round out the discussion on email security by explaining why email security has seen poor uptake and answering the question as to which email security protocol is most popular. The answer may surprise you!

[1] Strictly speaking, you can bypass the sender's SMTP server. In practice, this is considered a hole in the SMTP system that email providers are trying to plug.
[2] I've had 13 different connections to the internet in the same time as I've had my main email address, not counting all the public wifis that I have used. Whereas an attacker would find it extraordinarily difficult to intercept all of my SSH sessions for a MITM attack, intercepting all of my email sessions is clearly far easier if the attacker were my email provider.
[3] Before you read too much into this personal choice of S/MIME over PGP, it's entirely motivated by a simple concern: S/MIME is built into Thunderbird; PGP is not. As someone who does a lot of Thunderbird development work that could easily break the Enigmail extension locally, needing to use an extension would be disruptive to workflow.
[4] This is not to say that I don't heavily research many of my other posts, but I did go so far for this one as to actually start going through a lot of published journals in an attempt to find information.
[5] It's questionable how well the usability of a trust model UI can be measured in a lab setting, since the observer effect is particularly strong for all metrics of trust.
[6] The web of trust makes a nice graph, and graphs invite lots of interesting mathematical metrics. I've always been partial to eigenvectors of the graph, myself.
[7] Mozilla's policy for addition to NSS is basically the standard policy adopted by all open-source Linux or BSD distributions, seeing as OpenSSL never attempted to produce a root database.
[8] It looks to me that it's the browsers who are more in charge in this forum than the CAs.
[9] To my knowledge, this is the first—and so far only—attempt to actively MITM an SSL connection.

We just released the second beta of Thunderbird 31. Please help us improve Thunderbird quality by uncovering bugs now in Thunderbird 31 beta so that developers have time to fix them.

There are two ways you can help

- Use Thunderbird 31 beta in your daily activities. For problems that you find, file a bug report that blocks our tracking bug 1008543.

- Use Thunderbird 31 beta to do formal testing.  Use the moztrap testing system to tests : choose run test - find the Thunderbird product and choose 31 test run.

Visit https://etherpad.mozilla.org/tbird31testing for additional information, and to post your testing questions and results.

Thanks for contributing and helping!

Ludo for the QA team

Updated links

This post is part 6 of an intermittent series exploring the difficulties of writing an email client. Part 1 describes a brief history of the infrastructure. Part 2 discusses internationalization. Part 3 discusses MIME. Part 4 discusses email addresses. Part 5 discusses the more general problem of email headers. This part discusses how email security works in practice.

Email security is a rather wide-ranging topic, and one that I've wanted to cover for some time, well before several recent events that have made it come up in the wider public knowledge. There is no way I can hope to cover it in a single post (I think it would outpace even the length of my internationalization discussion), and there are definitely parts for which I am underqualified, as I am by no means an expert in cryptography. Instead, I will be discussing this over the course of several posts of which this is but the first; to ease up on the amount of background explanation, I will assume passing familiarity with cryptographic concepts like public keys, hash functions, as well as knowing what SSL and SSH are (though not necessarily how they work). If you don't have that knowledge, ask Wikipedia.

Before discussing how email security works, it is first necessary to ask what email security actually means. Unfortunately, the layman's interpretation is likely going to differ from the actual precise definition. Security is often treated by laymen as a boolean interpretation: something is either secure or insecure. The most prevalent model of security to people is SSL connections: these allow the establishment of a communication channel whose contents are secret to outside observers while also guaranteeing to the client the authenticity of the server. The server often then gets authenticity of the client via a more normal authentication scheme (i.e., the client sends a username and password). Thus there is, at the end, a channel that has both secrecy and authenticity [1]: channels with both of these are considered secure and channels without these are considered insecure [2].

In email, the situation becomes more difficult. Whereas an SSL connection is between a client and a server, the architecture of email is such that email providers must be considered as distinct entities from end users. In addition, messages can be sent from one person to multiple parties. Thus secure email is a more complex undertaking than just porting relevant details of SSL. There are two major cryptographic implementations of secure email [3]: S/MIME and PGP. In terms of implementation, they are basically the same [4], although PGP has an extra mode which wraps general ASCII (known as "ASCII-armor"), which I have been led to believe is less recommended these days. Since I know the S/MIME specifications better, I'll refer specifically to how S/MIME works.

S/MIME defines two main MIME types: multipart/signed, which contains the message text as a subpart followed by data indicating the cryptographic signature, and application/pkcs7-mime, which contains an encrypted MIME part. The important things to note about this delineation are that only the body data is encrypted [5], that it's theoretically possible to encrypt only part of a message's body, and that the signing and encryption constitute different steps. These factors combine to make for a potentially infuriating UI setup.

How does S/MIME tackle the challenges of encrypting email? First, rather than encrypting using recipients' public keys, the message is encrypted with a symmetric key. This symmetric key is then encrypted with each of the recipients' keys and then attached to the message. Second, by only signing or encrypting the body of the message, the transit headers are kept intact for the mail system to retain its ability to route, process, and deliver the message. The body is supposed to be prepared in the "safest" form before transit to avoid intermediate routers munging the contents. Finally, to actually ascertain what the recipients' public keys are, clients typically passively pull the information from signed emails. LDAP, unsurprisingly, contains an entry for a user's public key certificate, which could be useful in large enterprise deployments. There is also work ongoing right now to publish keys via DNS and DANE.

I mentioned before that S/MIME's use can present some interesting UI design decisions. I ended up actually testing some common email clients on how they handled S/MIME messages: Thunderbird, Apple Mail, Outlook [6], and Evolution. In my attempts to create a surreptitious signed part to confuse the UI, Outlook decided that the message had no body at all, and Thunderbird decided to ignore all indication of the existence of said part. Apple Mail managed to claim the message was signed in one of these scenarios, and Evolution took the cake by always agreeing that the message was signed [7]. It didn't even bother questioning the signature if the certificate's identity disagreed with the easily-spoofable From address. I was actually surprised by how well people did in my tests—I expected far more confusion among clients, particularly since the will to maintain S/MIME has clearly been relatively low, judging by poor support for "new" features such as triple-wrapping or header protection.

Another fault of S/MIME's design is that it makes the mistaken belief that composing a signing step and an encryption step is equivalent in strength to a simultaneous sign-and-encrypt. Another page describes this in far better detail than I have room to; note that this flaw is fixed via triple-wrapping (which has relatively poor support). This creates yet more UI burden into how to adequately describe in UI all the various minutiae in differing security guarantees. Considering that users already have a hard time even understanding that just because a message says it's from example@isp.invalid doesn't actually mean it's from example@isp.invalid, trying to develop UI that both adequately expresses the security issues and is understandable to end-users is an extreme challenge.

What we have in S/MIME (and PGP) is a system that allows for strong guarantees, if certain conditions are met, yet is also vulnerable to breaches of security if the message handling subsystems are poorly designed. Hopefully this is a sufficient guide to the technical impacts of secure email in the email world. My next post will discuss the most critical component of secure email: the trust model. After that, I will discuss why secure email has seen poor uptake and other relevant concerns on the future of email security.

[1] This is a bit of a lie: a channel that does secrecy and authentication at different times isn't as secure as one that does them at the same time.
[2] It is worth noting that authenticity is, in many respects, necessary to achieve secrecy.
[3] This, too, is a bit of a lie. More on this in a subsequent post.
[4] I'm very aware that S/MIME and PGP use radically different trust models. Trust models will be covered later.
[5] S/MIME 3.0 did add a provision stating that if the signed/encrypted part is a message/rfc822 part, the headers of that part should override the outer message's headers. However, I am not aware of a major email client that actually handles these kind of messages gracefully.
[6] Actually, I tested Windows Live Mail instead of Outlook, but given the presence of an official MIME-to-Microsoft's-internal-message-format document which seems to agree with what Windows Live Mail was doing, I figure their output would be identical.
[7] On a more careful examination after the fact, it appears that Evolution may have tried to indicate signedness on a part-by-part basis, but the UI was sufficiently confusing that ordinary users are going to be easily confused.

We just released the first beta of Thunderbird 30. There will be two betas for 30 and probably 2 or more for 31. We need to start uncovering bugs nows so that developers have time to fix things.

Now is the time to get the betas and use them as you do with the current release  and file bugs. Makes these bugs block our tracking bug : 1008543.

For the next beta we will need more people to do formal testing - we will use moztrap and eventbrite to track this. The more participants to this (and other during the 31 beta period), the higher the quality. Follow this blog or subscribe to the Thunderbird-tester mailing list if you wish to make 31 a great release.

Ludo for the QA team

beets is the extensible music database tool every programmer with a music collection has dreamed of writing.  At its simplest it’s a clever tagger that can normalize your music against the MusicBrainz database and then store the results in a searchable SQLite database.  But with plugins it can fetch album art, use the Discogs music database for tagging too, calculate ReplayGain values for all your music, integrate meta-data from The Echo Nest, etc.  It even has a Music Player Daemon server-mode (bpd) and a simple HTML interface (web) that lets you search for tracks and play them in your browse using the HTML5 audio tag.

I’ve tried a lot of music players through the years (alphabetically: amarok, banshee, exaile, quodlibet, rhythmbox).  They all are great music players and (at least!) satisfy the traditional Artist/Album/Track hierarchy use-case, but when you exceed 20,000 tracks and you have a lot of compilation cd’s, that frequently ends up not being enough. Extending them usually turned out to be too hard / not fun enough, although sometimes it was just a question of time and seeking greener pastures.

But enough context; if you’re reading my blog you probably are on board with the web platform being the greatest platform ever.  The notable bits of the implementation are:

• Server-wise, it’s a mash-up of beets’ MPD-alike plugin bpd and its web plugin.  Rather than needing to speak the MPD protocol over TCP to get your server to play music, you can just hit it with an HTTP POST and it will enqueue and play the song.  Server-sent events/EventSource are used to let the web UI hypothetically update as things happen on the server.  Right now the client can indeed tell the server to play a song and hear an update via the EventSource channel, but there’s almost certainly a resource leak on the server-side and there’s a lot more web/bpd interlinking required to get it reliable.  (Python’s Flask is neat, but I’m not yet clear on how to properly manage the life-cycle of a long-lived request that only dies when the connection dies since I’m seeing the appcontext get torn down even before the generator starts running.)
• The client is implemented in Polymer on top of some simple backbone.js collections that build on the existing logic from the beets web plugin.
  • The artist list uses the polymer-virtual-list element which is important if you’re going to be scrolling through a ton of artists.  The implementation is page-based; you tell it how many pages you want and how many items are on each page.  As you scroll it fires events that compel you to generate the appropriate page.  It’s an interesting implementation:
    • Pages are allowed to be variable height and therefore their contents are too, although a fixedHeight mode is also supported.
    • In variable-height mode, scroll offsets are translated to page positions by guessing the page based on the height of the first page and then walking up/down from there based on cached page-sizes until the right page size is found.  If there is missing information because the user managed to trigger a huge jump, extrapolation is performed based on the average item size from the first page.
    • Any changes to the contents of the list regrettably require discarding all existing pages/bindings.  At this time there is no way to indicate a splice at a certain point that should simply result in a displacement of the existing items.
  • Albums are loaded in batches from the server and artists dynamically derived from them.  Although this would allow for the UI to update as things are retrieved, the virtual-list invalidation issue concerned me enough to have the artist-list defer initialization until all albums are loaded.  On my machine a couple thousand albums load pretty quickly, so this isn’t a huge deal.
  • There’s filtering by artist name and number of albums in the database by that artist built on backbone-filtered-collection.  The latter one is important to me because scrolling through hundreds of artists where I might only own one cd or not even one whole cd is annoying.  (Although the latter is somewhat addressed currently by only using the albumartist for the artist generation so various artists compilations don’t clutter things up.)
  • If you click on an artist it plays the first track (numerically) from the first album (alphabetically) associated with the artist.  This does limit the songs you can listen to somewhat…
  • visualizations are done using d3.js; one svg per visualization

“What’s with all those tastefully chosen colors?” is what you are probably asking yourself.  The answer?  Two things!

1. A visualization of albums/releases in the database by time, heat-map style.
   • We bin all of the albums that beets knows about by year.  In this case we assume that 1980 is the first interesting year and so put 1979 and everything before it (including albums without a year) in the very first bin on the left.  The current year is the rightmost bucket.
   • We vertically divide the albums into “albums” (red), “singles” (green), and “compilations” (blue).  This is accomplished by taking the MusicBrainz Release Group / Types and mapping them down to our smaller space.
   • The more albums in a bin, the stronger the color.
2. A scatter-plot using the echo nest‘s acoustic attributes for the tracks where:
   • the x-axis is “danceability”.  Things to the left are less danceable.  Things to the right are more danceable.
   • the y-axis is “valence” which they define as “the musical positiveness conveyed by a track”.  Things near the top are sadder, things near the bottom are happier.
   • the colors are based on the type of album the track is from.  The idea was that singles tend to have remixes on them, so it’s interesting if we always see a big cluster of green remixes to the right.
   • tracks without the relevant data all end up in the upper-left corner.  There are a lot of these.  The echo nest is extremely generous in allowing non-commercial use of their API, but they limit you to 20 requests per minute and at this point the beets echonest plugin needs to upload (transcoded) versions of all my tracks since my music collection is apparently more esoteric than what the servers already have fingerprints for.

Together these visualizations let us infer:

• Madonna is more dancey than Morrissey!  Shocking, right?
• I bought the Morrissey singles box sets. And I got ripped off because there’s a distinct lack of green dots over on the right side.

Code is currently in the webpd branch of my beets fork although I should probably try and split it out into a separate repo.  You need to enable the webpd plugin like you would any other plugin for it to work.  There’s still a lot lot lot more work to be done for it to be usable, but I think it’s neat already.  It definitely works in Firefox and Chrome.

Previously, I've been developing JSMime as a subdirectory within comm-central. However, after discussions with other developers, I have moved the official repository of record for JSMime to its own repository, now found on GitHub. The repository has been cleaned up and the feature set for version 0.2 has been selected, so that the current tip on JSMime (also the initial version) is version 0.2. This contains the feature set I imported into Thunderbird's source code last night, which is to say support for parsing MIME messages into the MIME tree, as well as support for parsing and encoding email address headers.

Thunderbird doesn't actually use the new code quite yet (as my current tree is stuck on a mozilla-central build error, so I haven't had time to run those patches through a last minute sanity check before requesting review), but the intent is to replace the current C++ implementations of nsIMsgHeaderParser and nsIMimeConverter with JSMime instead. Once those are done, I will be moving forward with my structured header plans which more or less ought to make those interfaces obsolete.

Within JSMime itself, the pieces which I will be working on next will be rounding out the implementation of header parsing and encoding support (I have prototypes for Date headers and the infernal RFC 2231 encoding that Content-Disposition needs), as well as support for building MIME messages from their constituent parts (a feature which would be greatly appreciated in the depths of compose and import in Thunderbird). I also want to implement full IDN and EAI support, but that's hampered by the lack of a JS implementation I can use for IDN (yes, there's punycode.js, but that doesn't do StringPrep). The important task of converting the MIME tree to a list of body parts and attachments is something I do want to work on as well, but I've vacillated on the implementation here several times and I'm not sure I've found one I like yet.

JSMime, as its name implies, tries to work in as pure JS as possible, augmented with several web APIs as necessary (such as TextDecoder for charset decoding). I'm using ES6 as the base here, because it gives me several features I consider invaluable for implementing JavaScript: Promises, Map, generators, let. This means it can run on an unprivileged web page—I test JSMime using Firefox nightlies and the Firefox debugger where necessary. Unfortunately, it only really works in Firefox at the moment because V8 doesn't support many ES6 features yet (such as destructuring, which is annoying but simple enough to work around, or Map iteration, which is completely necessary for the code). I'm not opposed to changing it to make it work on Node.js or Chrome, but I don't realistically have the time to spend doing it myself; if someone else has the time, please feel free to contact me or send patches.

…unless you're an expert at assembly, that is. The title of this post was obviously meant to be an attention-grabber, but it is much truer than you might think: poorly-written assembly code will probably be slower than an optimizing compiler on well-written code (note that you may need to help the compiler along for things like vectorization). Now why is this?

Modern microarchitectures are incredibly complex. A modern x86 processor will be superscalar and use some form of compilation to microcode to do that. Desktop processors will undoubtedly have multiple instruction issues per cycle, forms of register renaming, branch predictors, etc. Minor changes—a misaligned instruction stream, a poor order of instructions, a bad instruction choice—could kill the ability to take advantages of these features. There are very few people who could accurately predict the performance of a given assembly stream (I myself wouldn't attempt it if the architecture can take advantage of ILP), and these people are disproportionately likely to be working on compiler optimizations. So unless you're knowledgeable enough about assembly to help work on a compiler, you probably shouldn't be hand-coding assembly to make code faster.

To give an example to elucidate this point (and the motivation for this blog post in the first place), I was given a link to an implementation of the N-queens problem in assembly. For various reasons, I decided to use this to start building a fine-grained performance measurement system. This system uses a high-resolution monotonic clock on Linux and runs the function 1000 times to warm up caches and counters and then runs the function 1000 more times, measuring each run independently and reporting the average runtime at the end. This is a single execution of the system; 20 executions of the system were used as the baseline for a t-test to determine statistical significance as well as visual estimation of normality of data. Since the runs observed about a constant 1-2 μs of noise, I ran all of my numbers on the 10-queens problem to better separate the data (total runtimes ended up being in the range of 200-300μs at this level). When I say that some versions are faster, the p-values for individual measurements are on the order of 10-20—meaning that there is a 1-in-100,000,000,000,000,000,000 chance that the observed speedups could be produced if the programs take the same amount of time to run.

The initial assembly version of the program took about 288μs to run. The first C++ version I coded, originating from the same genesis algorithm that the author of the assembly version used, ran in 275μs. A recursive program beat out a hand-written assembly block of code... and when I manually converted the recursive program into a single loop, the runtime improved to 249μs. It wasn't until I got rid of all of the assembly in the original code that I could get the program to beat the derecursified code (at 244μs)—so it's not the vectorization that's causing the code to be slow. Intrigued, I started to analyze why the original assembly was so slow.

It turns out that there are three main things that I think cause the slow speed of the original code. The first one is alignment of branches: the assembly code contains no instructions to align basic blocks on particular branches, whereas gcc happily emits these for some basic blocks. I mention this first as it is mere conjecture; I never made an attempt to measure the effects for myself. The other two causes are directly measured from observing runtime changes as I slowly replaced the assembly with code. When I replaced the use of push and pop instructions with a global static array, the runtime improved dramatically. This suggests that the alignment of the stack could be to blame (although the stack is still 8-byte aligned when I checked via gdb), which just goes to show you how much alignments really do matter in code.

The final, and by far most dramatic, effect I saw involves the use of three assembly instructions: bsf (find the index of the lowest bit that is set), btc (clear a specific bit index), and shl (left shift). When I replaced the use of these instructions with a more complicated expression int bit = x & -x and x = x - bit, the program's speed improved dramatically. And the rationale for why the speed improved won't be found in latency tables, although those will tell you that bsf is not a 1-cycle operation. Rather, it's in minutiae that's not immediately obvious.

The original program used the fact that bsf sets the zero flag if the input register is 0 as the condition to do the backtracking; the converted code just checked if the value was 0 (using a simple test instruction). The compare and the jump instructions are basically converted into a single instruction in the processor. In contrast, the bsf does not get to do this; combined with the lower latency of the instruction intrinsically, it means that empty loops take a lot longer to do nothing. The use of an 8-bit shift value is also interesting, as there is a rather severe penalty for using 8-bit registers in Intel processors as far as I can see.

Now, this isn't to say that the compiler will always produce the best code by itself. My final code wasn't above using x86 intrinsics for the vector instructions. Replacing the _mm_andnot_si128 intrinsic with an actual and-not on vectors caused gcc to use other, slower instructions instead of the vmovq to move the result out of the SSE registers for reasons I don't particularly want to track down. The use of the _mm_blend_epi16 and _mm_srli_si128 intrinsics can probably be replaced with __builtin_shuffle instead for more portability, but I was under the misapprehension that this was a clang-only intrinsic when I first played with the code so I never bothered to try that, and this code has passed out of my memory long enough that I don't want to try to mess with it now.

In short, compilers know things about optimizing for modern architectures that many general programmers don't. Compilers may have issues with autovectorization, but the existence of vector intrinsics allow you to force compilers to use vectorization while still giving them leeway to make decisions about instruction scheduling or code alignment which are easy to screw up in hand-written assembly. Also, compilers are liable to get better in the future, whereas hand-written assembly code is unlikely to get faster in the future. So only write assembly code if you really know what you're doing and you know you're better than the compiler.

For Firefox OS the Gaia UI currently uses Travis CI to run a series of test jobs in parallel for each pull request.  While Travis has a neat ember.js-based live-updating web UI, I usually find myself either staring at my build watching it go nowhere or forgetting about it entirely.  The latter is usually what ends up happening since we have a finite number of builders available, we have tons of developers, each build takes 5 jobs, and some of those jobs can take up to 35 minutes to run when they finally get a turn to run.

I recently noticed ThinkGeek had a bunch of Dream Cheeky USB LED notifiers on sale.  They’re each a USB-controlled tri-color LED in a plastic case that acts as a nice diffuser.  Linux’s “usbled” driver exposes separate red/green/blue files via sysfs that you can echo numbers into to control them.  While the driver and USB protocol inherently support a range of 0-255, it seems like 0-63 or 0-64 is all they give.  The color gamut isn’t amazing but is quite respectable and they are bright enough that they are useful in daylight.  I made a node.js library at https://github.com/asutherland/gaudy-leds that can do some basic tricks and is available on npm as “gaudy-leds”.  You can tell it to do things by doing “gaudy-leds set red green blue purple”, etc.  I added a bunch of commander sub-commands, so “gaudy-leds –help” should give a lot more details than the currently spartan readme.

I couldn’t find any existing tools/libraries to easily watch a Travis CI build and invoke commands like that (though I feel like they must exist) so I wrote https://github.com/asutherland/travis-build-watcher.  While the eventual goal is to not have to manually activate it at all, right now I can point it at a Travis build or a github pull request and it will poll appropriately so it ends up at the latest build and updates the state of the LEDs each time it polls.

Relevant notes / context:

• There is a storied history of people hooking build/tree status up to LED lights and real traffic lights and stuff like that.  I think if you use Jenkins you’re particularly in luck.  This isn’t anything particularly new or novel, but the webmail notifiers are a great off-the-shelf solution.  The last time I did something like this I used a phidgets LED64 in a rice paper lamp and the soldering was much more annoying than dealing with a mess of USB cables.  Also, it could really only display one status at a time.
• There are obviously USB port scalability issues, but you can get a 24-port USB hub for ~$40 from Amazon/monoprice/etc.  (They all seem to be made by the same manufacturer.)  I coincidentally bought 24 of the notifiers after my initial success with 6, so I am really prepared for an explosion in test jobs!
• While I’m currently trying to keep things UNIXy with a bunch of small command-line tools operating together, I think I would like to have some kind of simple message-bus mechanism so that:
  • mozilla-central mach builds can report status as they go
  • webhooks / other async mechanisms can be used to improve efficiency and require less manual triggering/interaction on my end.  So if I re-spin a build from the web UI I won’t need to re-trigger the script locally and such.  Please let me know if you’re aware of existing solutions in this space, I didn’t find much and am planning to just use redis as glue for a bunch of small/independent pieces plus a more daemonish node process for polling / interacting with the web/AMQP.
• There are efforts underway to overhaul the continuous integration mechanism used for Gaia.  This should address delays in starting tests by being able to throw more resources at them as well as allow notification by whatever Mozilla Pulse’s successor is.

Several years ago, I embarked on a project to collect the headers of all the messages I could reach on NNTP, with the original intent of studying the progression of the most common news clients. More recently, I used this dataset to attempt to discover the prevalence of charsets in email messages. In doing so, I identified a critical problem with the dataset: since it only contains headers, there is very little scope for actually understanding the full, sad story of charsets. So I've decided to rectify this problem.

This time, I modified my data-collection scripts to make it much easier to mass-download NNTP messages. The first script effectively lists all the newsgroups, and then all the message IDs in those newsgroups, stuffing the results in a set to remove duplicates (cross-posts). The second script uses Python's nntplib package to attempt to download all of those messages. Of the 32,598,261 messages identified by the first set, I succeeded in obtaining 1,025,586 messages in full or in part. Some messages failed to download due to crashing nntplib (which appears to be unable to handle messages of unbounded length), and I suspect my newsserver connections may have just timed out in the middle of the download at times. Others failed due to expiring before I could download them. All in all, 19,288 messages were not downloaded.

Analysis of the contents of messages were hampered due to a strong desire to find techniques that could mangle messages as little as possible. Prior experience with Python's message-parsing libraries lend me to believe that they are rather poor at handling some of the crap that comes into existence, and the errors in nntplib suggest they haven't fixed them yet. The only message parsing framework I truly trust to give me the level of finess is the JSMime that I'm writing, but that happens to be in the wrong language for this project. After reading some blog posts of Jeffrey Stedfast, though, I decided I would give GMime a try instead of trying to rewrite ad-hoc MIME parser #N.

Ultimately, I wrote a program to investigate the following questions on how messages operate in practice:

• What charsets are used in practice? How are these charsets named?
• For undeclared charsets, what are the correct charsets?
• For charsets unknown to a decoder, how often would ASCII suffice?
• What charsets are used in RFC 2047 encoded words?
• How prevalent are malformed RFC 2047 encoded words?
• When HTML and MIME are mixed, who wins?
• What is the state of 8-bit headers?

While those were the questions I seeked the answers to originally, I did come up with others as I worked on my tool, some in part due to what information I was basically already collecting. The tool I wrote primarily uses GMime to convert the body parts to 8-bit text (no charset conversion), as well as parse the Content-Type headers, which are really annoying to do without writing a full parser. I used ICU to handle charset conversion and detection. RFC 2047 decoding is done largely by hand since I needed very specific information that I couldn't convince GMime to give me. All code that I used is available upon request; the exact dataset is harder to transport, given that it is some 5.6GiB of data.

Other than GMime being built on GObject and exposing a C API, I can't complain much, although I didn't try to use it to do magic. Then again, in my experience (and as this post will probably convince you as well), you really want your MIME library to do charset magic for you, so in doing well for my needs, it's actually not doing well for a larger audience. ICU's C API similarly makes me want to complain. However, I'm now very suspect of the quality of its charset detection code, which is the main reason I used it. Trying to figure out how to get it to handle the charset decoding errors also proved far more annoying than it really should.

Some final background regards the biases I expect to crop up in the dataset. As the approximately 1 million messages were drawn from the python set iterator, I suspect that there's no systematic bias towards or away from specific groups, excepting that the ~11K messages found in the eternal-september.* hierarchy are completely represented. The newsserver I used, Eternal September, has a respectably large set of newsgroups, although it is likely to be biased towards European languages and under-representing East Asians. The less well-connected South America, Africa, or central Asia are going to be almost completely unrepresented. The download process will be biased away towards particularly heinous messages (such as exceedingly long lines), since nntplib itself is failing.

This being news messages, I also expect that use of 8-bit will be far more common than would be the case in regular mail messages. On a related note, the use of 8-bit in headers would be commensurately elevated compared to normal email. What would be far less common is HTML. I also expect that undeclared charsets may be slightly higher.

Charsets

Charset data is mostly collected on the basis of individual body parts within body messages; some messages have more than one. Interestingly enough, the 1,025,587 messages yielded 1,016,765 body parts with some text data, which indicates that either the messages on the server had only headers in the first place or the download process somehow managed to only grab the headers. There were also 393 messages that I identified having parts with different charsets, which only further illustrates how annoying charsets are in messages.

The aliases in charsets are mostly uninteresting in variance, except for the various labels used for US-ASCII (us - ascii, 646, and ANSI_X3.4-1968 are the less-well-known aliases), as well as the list of charsets whose names ICU was incapable of recognizing, given below. Unknown charsets are treated as equivalent to undeclared charsets in further processing, as there were too few to merit separate handling (45 in all).

• x-windows-949
• isolatin
• ISO-IR-111
• Default
• ISO-8859-1 format=flowed
• X-UNKNOWN
• x-user-defined
• windows-874
• 3D"us-ascii"
• x-koi8-ru
• windows-1252 (fuer gute Newsreader)
• LATIN-1#2 iso-8859-1

For the next step, I used ICU to attempt to detect the actual charset of the body parts. ICU's charset detector doesn't support the full gamut of charsets, though, so charset names not claimed to be detected were instead processed by checking if they decoded without error. Before using this detection, I detect if the text is pure ASCII (excluding control characters, to enable charsets like ISO-2022-JP, and +, if the charset we're trying to check is UTF-7). ICU has a mode which ignores all text in things that look like HTML tags, and this mode is set for all HTML body parts.

I don't quite believe ICU's charset detection results, so I've collapsed the results into a simpler table to capture the most salient feature. The correct column indicates the cases where the detected result was the declared charset. The ASCII column captures the fraction which were pure ASCII. The UTF-8 column indicates if ICU reported that the text was UTF-8 (it always seems to try this first). The Wrong C1 column refers to an ISO-8859-1 text being detected as windows-1252 or vice versa, which is set by ICU if it sees or doesn't see an octet in the appropriate range. The other column refers to all other cases, including invalid cases for charsets not supported by ICU.

DeclaredCorrectASCIIUTF-8 Wrong C1OtherTotal ISO-8859-1230,526225,6678838,1191,035466,230 Undeclared148,0541,11637,626186,796 UTF-875,67437,6001,551114,825 US-ASCII98,238030498,542 ISO-8859-1567,52918,527086,056 windows-125221,4144,3701543,31913029,387 ISO-8859-218,6472,13870712,31923,245 KOI8-R4,61642421,1126,154 GB23121,3075901121,478 Big562260801741,404 windows-125634310045398 IBM437842570341 ISO-8859-1331160317 windows-125113197161290 windows-12506969014101253 ISO-8859-7262600131183 ISO-8859-9127110017155 ISO-2022-JP766903148 macintosh67570124 ISO-8859-16015101116 UTF-7514055 x-mac-croatian0132538 KOI8-U282030 windows-125501800624 ISO-8859-4230023 EUC-KR0301619 ISO-8859-14144018 GB180301430017 ISO-8859-800001616 TIS-620150015 Shift_JIS840113 ISO-8859-391111 ISO-8859-10100010 KSC_56013609 GBK4206 windows-1253030025 ISO-8859-510034 IBM8500404 windows-12570303 ISO-2022-JP-22002 ISO-8859-601001 Total421,751536,3732,22611,52344,8921,016,765

The most obvious thing shown in this table is that the most common charsets remain ISO-8859-1, Windows-1252, US-ASCII, UTF-8, and ISO-8859-15, which is to be expected, given an expected prior bias to European languages in newsgroups. The low prevalence of ISO-2022-JP is surprising to me: it means a lower incidence of Japanese than I would have expected. Either that, or Japanese have switched to UTF-8 en masse, which I consider very unlikely given that Japanese have tended to resist the trend towards UTF-8 the most.

Beyond that, this dataset has caused me to lose trust in the ICU charset detectors. KOI8-R is recorded as being 18% malformed text, with most of that ICU believing to be ISO-8859-1 instead. Judging from the results, it appears that ICU has a bias towards guessing ISO-8859-1, which means I don't believe the numbers in the Other column to be accurate at all. For some reason, I don't appear to have decoders for ISO-8859-16 or x-mac-croatian on my local machine, but running some tests by hand appear to indicate that they are valid and not incorrect.

Somewhere between 0.1% and 1.0% of all messages are subject to mojibake, depending on how much you trust the charset detector. The cases of UTF-8 being misdetected as non-UTF-8 could potentially be explained by having very few non-ASCII sequences (ICU requires four valid sequences before it confidently declares text UTF-8); someone who writes a post in English but has a non-ASCII signature (such as myself) could easily fall into this category. Despite this, however, it does suggest that there is enough mojibake around that users need to be able to override charset decisions.

The undeclared charsets are described, in descending order of popularity, by ISO-8859-1, Windows-1252, KOI8-R, ISO-8859-2, and UTF-8, describing 99% of all non-ASCII undeclared data. ISO-8859-1 and Windows-1252 are probably over-counted here, but the interesting tidbit is that KOI8-R is used half as much undeclared as it is declared, and I suspect it may be undercounted. The practice of using locale-default fallbacks that Thunderbird has been using appears to be the best way forward for now, although UTF-8 is growing enough in popularity that using a specialized detector that decodes as UTF-8 if possible may be worth investigating (3% of all non-ASCII, undeclared messages are UTF-8).

HTML

Unsuprisingly (considering I'm polling newsgroups), very few messages contained any HTML parts at all: there were only 1,032 parts in the total sample size, of which only 552 had non-ASCII characters and were therefore useful for the rest of this analysis. This means that I'm skeptical of generalizing the results of this to email in general, but I'll still summarize the findings.

HTML, unlike plain text, contains a mechanism to explicitly identify the charset of a message. The official algorithm for determining the charset of an HTML file can be described simply as "look for a <meta> tag in the first 1024 bytes. If it can be found, attempt to extract a charset using one of several different techniques depending on what's present or not." Since doing this fully properly is complicated in library-less C++ code, I opted to look first for a <meta[ \t\r\n\f] production, guess the extent of the tag, and try to find a charset= string somewhere in that tag. This appears to be an approach which is more reflective of how this parsing is actually done in email clients than the proper HTML algorithm. One difference is that my regular expressions also support the newer <meta charset="UTF-8"/> construct, although I don't appear to see any use of this.

I found only 332 parts where the HTML declared a charset. Only 22 parts had a case where both a MIME charset and an HTML charset and the two disagreed with each other. I neglected to count how many messages had HTML charsets but no MIME charsets, but random sampling appeared to indicate that this is very rare on the data set (the same order of magnitude or less as those where they disagreed).

As for the question of who wins: of the 552 non-ASCII HTML parts, only 71 messages did not have the MIME type be the valid charset. Then again, 71 messages did not have the HTML type be valid either, which strongly suggests that ICU was detecting the incorrect charset. Judging from manual inspection of such messages, it appears that the MIME charset ought to be preferred if it exists. There are also a large number of HTML charset specifications saying unicode, which ICU treats as UTF-16, which is most certainly wrong.

Headers

In the data set, 1,025,856 header blocks were processed for the following statistics. This is slightly more than the number of messages since the headers of contained message/rfc822 parts were also processed. The good news is that 97% (996,103) headers were completely ASCII. Of the remaining 29,753 headers, 3.6% (1,058) were UTF-8 and 43.6% (12,965) matched the declared charset of the first body part. This leaves 52.9% (15,730) that did not match that charset, however.

Now, NNTP messages can generally be expected to have a higher 8-bit header ratio, so this is probably exaggerating the setup in most email messages. That said, the high incidence is definitely an indicator that even non-EAI-aware clients and servers cannot blindly presume that headers are 7-bit, nor can EAI-aware clients and servers presume that 8-bit headers are UTF-8. The high incidence of mismatching the declared charset suggests that fallback-charset decoding of headers is a necessary step.

RFC 2047 encoded-words is also an interesting statistic to mine. I found 135,951 encoded-words in the data set, which is rather low, considering that messages can be reasonably expected to carry more than one encoded-word. This is likely an artifact of NNTP's tendency towards 8-bit instead of 7-bit communication and understates their presence in regular email.

Counting encoded-words can be difficult, since there is a mechanism to let them continue in multiple pieces. For the purposes of this count, a sequence of such words count as a single word, and I indicate the number of them that had more than one element in a sequence in the Continued column. The 2047 Violation column counts the number of sequences where decoding words individually does not yield the same result as decoding them as a whole, in violation of RFC 2047. The Only ASCII column counts those words containing nothing but ASCII symbols and where the encoding was thus (mostly) pointless. The Invalid column counts the number of sequences that had a decoder error.

CharsetCountContinued2047 ViolationOnly ASCIIInvalid ISO-8859-156,35515,6104990 UTF-836,56314,2163,3112,7049,765 ISO-8859-1520,6995,695400 ISO-8859-211,2472,66990 windows-12525,1743,075260 KOI8-R3,5231,203120 windows-125676556800 Big551146280171 ISO-8859-71652603 windows-12511573020 GB2312126356051 ISO-2022-JP10285049 ISO-8859-13784500 ISO-8859-9762100 ISO-8859-471200 windows-1250682100 ISO-8859-5662000 US-ASCII3810380 TIS-620363400 KOI8-U251100 ISO-8859-16221022 UTF-7172183 EUC-KR174409 x-mac-croatian103010 Shift_JIS80003 Unknown7207 ISO-2022-KR70000 GB1803061001 windows-12554000 ISO-8859-143000 ISO-8859-32100 GBK20002 ISO-8859-61100 Total135,95143,3603,3613,33810,096

This table somewhat mirrors the distribution of regular charsets, with one major class of differences: charsets that represent non-Latin scripts (particularly Asian scripts) appear to be overdistributed compared to their corresponding use in body parts. The exception to this rule is GB2312 which is far lower than relative rankings would presume—I attribute this to people using GB2312 being more likely to use 8-bit headers instead of RFC 2047 encoding, although I don't have direct evidence.

Clearly continuations are common, which is to be relatively expected. The sad part is how few people bother to try to adhere to the specification here: out of 14,312 continuations in languages that could violate the specification, 23.5% of them violated the specification. The mode-shifting versions (ISO-2022-JP and EUC-KR) are basically all violated, which suggests that no one bothered to check if their encoder "returns to ASCII" at the end of the word (I know Thunderbird's does, but the other ones I checked don't appear to).

The number of invalid UTF-8 decoded words, 26.7%, seems impossibly high to me. A brief check of my code indicates that this is working incorrectly in the face of invalid continuations, which certainly exaggerates the effect but still leaves a value too high for my tastes. Of more note are the elevated counts for the East Asian charsets: Big5, GB2312, and ISO-2022-JP. I am not an expert in charsets, but I belive that Big5 and GB2312 in particular are a family of almost-but-not-quite-identical charsets and it may be that ICU is choosing the wrong candidate of each family for these instances.

There is a surprisingly large number of encoded words that encode only ASCII. When searching specifically for the ones that use the US-ASCII charset, I found that these can be divided into three categories. One set comes from a few people who apparently have an unsanitized whitespace (space and LF were the two I recall seeing) in the display name, producing encoded words like =?us-ascii?Q?=09Edward_Rosten?=. Blame 40tude Dialog here. Another set encodes some basic characters (most commonly = and ?, although a few other interpreted characters popped up). The final set of errors were double-encoded words, such as =?us-ascii?Q?=3D=3FUTF-8=3FQ=3Ff=3DC3=3DBCr=3F=3D?=, which appear to be all generated by an Emacs-based newsreader.

One interesting thing when sifting the results is finding the crap that people produce in their tools. By far the worst single instance of an RFC 2047 encoded-word that I found is this one: Subject: Re: [Kitchen Nightmares] Meow! Gordon Ramsay Is =?ISO-8859-1?B?UEgR lqZ VuIEhlYWQgVH rbGeOIFNob BJc RP2JzZXNzZW?= With My =?ISO-8859-1?B?SHVzYmFuZ JzX0JhbGxzL JfU2F5c19BbXiScw==?= Baking Company Owner (complete with embedded spaces), discovered by crashing my ad-hoc base64 decoder (due to the spaces). The interesting thing is that even after investigating the output encoding, it doesn't look like the text is actually correct ISO-8859-1... or any obvious charset for that matter.

I looked at the unknown charsets by hand. Most of them were actually empty charsets (looked like =??B?Sy4gSC4gdm9uIFLDvGRlbg==?=), and all but one of the outright empty ones were generated by KNode and really UTF-8. The other one was a Windows-1252 generated by a minor newsreader.

Another important aspect of headers is how to handle 8-bit headers. RFC 5322 blindly hopes that headers are pure ASCII, while RFC 6532 dictates that they are UTF-8. Indeed, 97% of headers are ASCII, leaving just 29,753 headers that are not. Of these, only 1,058 (3.6%) are UTF-8 per RFC 6532. Deducing which charset they are is difficult because the large amount of English text for header names and the important control values will greatly skew any charset detector, and there is too little text to give a charset detector confidence. The only metric I could easily apply was testing Thunderbird's heuristic as "the header blocks are the same charset as the message contents"—which only worked 45.2% of the time.

Encodings

While developing an earlier version of my scanning program, I was intrigued to know how often various content transfer encodings were used. I found 1,028,971 parts in all (1,027,474 of which are text parts). The transfer encoding of binary did manage to sneak in, with 57 such parts. Using 8-bit text was very popular, at 381,223 samples, second only to 7-bit at 496,114 samples. Quoted-printable had 144,932 samples and base64 only 6,640 samples. Extremely interesting are the presence of 4 illegal transfer encodings in 5 messages, two of them obvious typos and the others appearing to be a client mangling header continuations into the transfer-encoding.

Conclusions

So, drawing from the body of this data, I would like to make the following conclusions as to using charsets in mail messages:

1. Have a fallback charset. Undeclared charsets are extremely common, and I'm skeptical that charset detectors are going to get this stuff right, particularly since email can more naturally combine multiple languages than other bodies of text (think signatures). Thunderbird currently uses a locale-dependent fallback charset, which roughly mirrors what Firefox and I think most web browsers do.
2. Let users override charsets when reading. On a similar token, mojibake text, while not particularly common, is common enough to make declared charsets sometimes unreliable. It's also possible that the fallback charset is wrong, so users may need to override the chosen charset.
3. Testing is mandatory. In this set of messages, I found base64 encoded words with spaces in them, encoded words without charsets (even UNKNOWN-8BIT), and clearly invalid Content-Transfer-Encodings. Real email messages that are flagrantly in violation of basic spec requirements exist, so you should make sure that your email parser and client can handle the weirdest edge cases.
4. Non-UTF-8, non-ASCII headers exist. EAI not withstanding, 8-bit headers are a reality. Combined with a predilection for saying ASCII when text is really ASCII, this means that there is often no good in-band information to tell you what charset is correct for headers, so you have to go back to a fallback charset.
5. US-ASCII really means ASCII. Email clients appear to do a very good job of only emitting US-ASCII as a charset label if it's US-ASCII. The sample size is too small for me to grasp what charset 8-bit characters should imply in US-ASCII.
6. Know your decoders. ISO-8859-1 actually means Windows-1252 in practice. Big5 and GB1232 are actually small families of charsets with slightly different meanings. ICU notably disagrees with some of these realities, so be sure to include in your tests various charset edge cases so you know that the decoders are correct.
7. UTF-7 is still relevant. Of the charsets I found not mentioned in the WHATWG encoding spec, IBM437 and x-mac-croatian are in use only due to specific circumstances that limit their generalizable presence. IBM850 is too rare. UTF-7 is common enough that you need to actually worry about it, as abominable and evil a charset it is.
8. HTML charsets may matter—but MIME matters more. I don't have enough data to say if charsets declared in HTML are needed to do proper decoding. I do have enough to say fairly conclusively that the MIME charset declaration is authoritative if HTML disagrees.
9. Charsets are not languages. The entire reason x-mac-croatian is used at all can be traced to Thunderbird displaying the charset as "Croatian," despite it being pretty clearly not a preferred charset. Similarly most charsets are often enough ASCII that, say, an instance of GB2312 is a poor indicator of whether or not the message is in English. Anyone trying to filter based on charsets is doing a really, really stupid thing.
10. RFCs reflect an ideal world, not reality. This is most notable in RFC 2047: the specification may state that encoded words are supposed to be independently decodable, but the evidence is pretty clear that more clients break this rule than uphold it.
11. Limit the charsets you support. Just because your library lets you emit a hundred charsets doesn't mean that you should let someone try to do it. You should emit US-ASCII or UTF-8 unless you have a really compelling reason not to, and those compelling reasons don't require obscure charsets. Some particularly annoying charsets should never be written: EBCDIC is already basically dead on the web, and I'd like to see UTF-7 die as well.

When I have time, I'm planning on taking some of the more egregious or interesting messages in my dataset and packaging them into a database of emails to help create testsuites on handling messages properly.