Journal tags: authentication

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Authentication

Two-factor authentication is generally considered A Good Thing™️ when you’re logging in to some online service.

The word “factor” here basically means “kind” so you’re doing two kinds of authentication. Typical factors are:

  • Something you know (like a password),
  • Something you have (like a phone or a USB key),
  • Something you are (biometric Black Mirror shit).

Asking for a password and an email address isn’t two-factor authentication. They’re two pieces of identification, but they’re the same kind (something you know). Same goes for supplying your fingerprint and your face: two pieces of information, but of the same kind (something you are).

None of these kinds of authentication are foolproof. All of them can change. All of them can be spoofed. But when you combine factors, it gets a lot harder for an attacker to breach both kinds of authentication.

The most common kind of authentication on the web is password-based (something you know). When a second factor is added, it’s often connected to your phone (something you have).

Every security bod I’ve talked to recommends using an authenticator app for this if that option is available. Otherwise there’s SMS—short message service, or text message to most folks—but SMS has a weakness. Because it’s tied to a phone number, technically you’re only proving that you have access to a SIM (subscriber identity module), not a specific phone. In the US in particular, it’s all too easy for an attacker to use social engineering to get a number transferred to a different SIM card.

Still, authenticating with SMS is an option as a second factor of authentication. When you first sign up to a service, as well as providing the first-factor details (a password and a username or email address), you also verify your phone number. Then when you subsequently attempt to log in, you input your password and on the next screen you’re told to input a string that’s been sent by text message to your phone number (I say “string” but it’s usually a string of numbers).

There’s an inevitable friction for the user here. But then, there’s a fundamental tension between security and user experience.

In the world of security, vigilance is the watchword. Users need to be aware of their surroundings. Is this web page being served from the right domain? Is this email coming from the right address? Friction is an ally.

But in the world of user experience, the opposite is true. “Don’t make me think” is the rallying cry. Friction is an enemy.

With SMS authentication, the user has to manually copy the numbers from the text message (received in a messaging app) into a form on a website (in a different app—a web browser). But if the messaging app and the browser are on the same device, it’s possible to improve the user experience without sacrificing security.

If you’re building a form that accepts a passcode sent via SMS, you can use the autocomplete attribute with a value of “one-time-code”. For a six-digit passcode, your input element might look something like this:

<input type="text" maxlength="6" inputmode="numeric" autocomplete="one-time-code">

With one small addition to one HTML element, you’ve saved users some tedious drudgery.

There’s one more thing you can do to improve security, but it’s not something you add to the HTML. It’s something you add to the text message itself.

Let’s say your website is example.com and the text message you send reads:

Your one-time passcode is 123456.

Add this to the end of the text message:

@example.com #123456

So the full message reads:

Your one-time passcode is 123456.

@example.com #123456

The first line is for humans. The second line is for machines. Using the @ symbol, you’re telling the device to only pre-fill the passcode for URLs on the domain example.com. Using the # symbol, you’re telling the device the value of the passcode. Combine this with autocomplete="one-time-code" in your form and the user shouldn’t have to lift a finger.

I’m fascinated by these kind of emergent conventions in text messages. Remember that the @ symbol and # symbol in Twitter messages weren’t ideas from Twitter—they were conventions that users started and the service then adopted.

It’s a bit different with the one-time code convention as there is a specification brewing from representatives of both Google and Apple.

Tess is leading from the Apple side and she’s got another iron in the fire to make security and user experience play nicely together using the convention of the /.well-known directory on web servers.

You can add a URL for /.well-known/change-password which redirects to the form a user would use to update their password. Browsers and password managers can then use this information if they need to prompt a user to update their password after a breach. I’ve added this to The Session.

Oh, and on that page where users can update their password, the autocomplete attribute is your friend again:

<input type="password" autocomplete="new-password">

If you want them to enter their current password first, use this:

<input type="password" autocomplete="current-password">

All of the things I’ve mentioned—the autocomplete attribute, origin-bound one-time codes in text messages, and a well-known URL for changing passwords—have good browser support. But even if they were only supported in one browser, they’d still be worth adding. These additions do absolutely no harm to browsers that don’t yet support them. That’s progressive enhancement.

Web Forms: Now You See Them, Now You Don’t! by Jason Grigsby

Jason is on stage at An Event Apart Chicago in a tuxedo. He wants to talk about how we can make web forms magical. Oh, I see. That explains the get-up.

We’re always being told to make web forms shorter. Luke Wroblewski has highlighted the work of companies that have reduced form fields and increased conversion.

But what if we could get rid of forms altogether? Wouldn’t that be magical!

Jason will reveal the secrets to this magic. But first—a volunteer from the audience, please! Please welcome Joe to the stage.

Joe will now log in on a phone. He types in the username. Then the password. The password is hodge-podge of special characters, numbers and upper and lowercase letters. Joe starts typing. Jason takes the phone and logs in without typing anything!

The secret: Jason was holding an NFC security key in his hand. That works with a new web standard called WebAuthn.

Passwords are terrible. People share them across sites, but who can blame them? It’s hard to remember lots of passwords. The only people who love usernames and passwords are hackers. So sites are developing other methods to try to keep people secure. Two factor authentication helps, although it doesn’t help us with phishing attacks. The hacker gets the password from the phished user …and then gets the one-time code from the phished user too.

But a physical device like a security key solves this problem. So why aren’t we all using security keys (apart from the fear of losing the key)? Well, until WebAuthn, there wasn’t a way for websites to use the keys.

A web server generates a challenge—a long string—that gets sent to a website and passed along to the user. The user’s device generates a credential ID and public and private keys for that domain. The web site stores the public key and credential ID. From then on, the credential ID is used by the website in challenges to users logging in.

There were three common ways that we historically proved who we claimed to be.

  1. Something you know (e.g. a password).
  2. Something you have (e.g. a security key).
  3. Something you are (e.g. biometric information).

These are factors of identification. So two-factor identification is the combination of any of those two. If you use a security key combined with a fingerprint scanner, there’s no need for passwords.

The browser support for the web authentication API (WebAuthn) is a bit patchy right now but you can start playing around with it.

There are a few other options for making logging in faster. There’s the Credential Management API. It allows someone to access passwords stored in their browser’s password manager. But even though it’s newer, there’s actually better browser support for WebAuthn than Credential Management.

Then there’s federated login, or social login. Jason has concerns about handing over log-in to a company like Facebook, Twitter, or Google, but then again, it means fewer passwords. As a site owner, there’s actually a lot of value in not storing log-in information—you won’t be accountable for data breaches. The problem is that you’ve got to decide which providers you’re going to support.

Also keep third-party password managers in mind. These tools—like 1Password—are great. In iOS they’re now nicely integrated at the operating system level, meaning Safari can use them. Finally it’s possible to log in to websites easily on a phone …until you encounter a website that prevents you logging in this way. Some websites get far too clever about detecting autofilled passwords.

Time for another volunteer from the audience. This is Tyler. Tyler will help Jason with a simple checkout form. Shipping information, credit card information, and so on. Jason will fill out this form blindfolded. Tyler will first verify that the dark goggles that Jason will be wearing don’t allow him to see the phone screen. Jason will put the goggles on and Tyler will hand him the phone with the checkout screen open.

Jason dons the goggles. Tyler hands him the phone. Jason does something. The form is filled in and submitted!

What was the secret? The goggles prevented Jason from seeing the phone …but they didn’t prevent the screen from seeing Jason. The goggles block everything but infrared. The iPhone uses infrared for Face ID. So the iPhone, it just looked like Jason was wearing funky sunglasses. Face ID then triggered the Payment Request API.

The Payment Request API allows us to use various payment methods that are built in to the operating system, but without having to make separate implementations for each payment method. The site calls the Payment Request API if it’s supported (use feature detection and progressive enhancement), then trigger the payment UI in the browser. The browser—not the website!—then makes a call to the payment processing provider e.g. Stripe.

E-commerce sites using the Payment Request API have seen a big drop in abandonment and a big increase in completed payments. The browser support is pretty good, especially on mobile. And remember, you can use it as a progressive enhancement. It’s kind of weird that we don’t encounter it more often—it’s been around for a few years now.

Jason read the fine print for Apple Pay, Google Pay, Microsoft Pay, and Samsung Pay. It doesn’t like there’s anything onerous in there that would stop you using them.

On some phones, you can now scan credit cards using the camera. This is built in to the operating system so as a site owner, you’ve just got to make sure not to break it. It’s really an extension of autofill. You should know what values the autocomplete attribute can take. There are 48 different values; it’s not just for checkouts. When users use autofill, they fill out forms 30% faster. So make sure you don’t put obstacles in the way of autofill in your forms.

Jason proceeds to relate a long and involved story about buying burritos online from Chipotle. The upshot is: use the autocomplete, type, maxlength, and pattern attributes correctly on input elements. Test autofill with your forms. Make it part of your QA process.

So, to summarise, here’s how you make your forms disappear:

  1. Start by reducing the number of form fields.
  2. Use the correct HTML to support autofill. Support password managers and password-pasting. At least don’t break that behaviour.
  3. Provide alternate ways of logging in. Federated login or the Credentials API.
  4. Test autofill and other form features.
  5. Look for opportunities to replace forms entirely with biometrics.

Any sufficiently advanced technology is indistinguishable from magic.

—Arthur C. Clarke’s Third Law

Don’t our users deserve magical experiences?

Twitter permissions

Twitter has come in for a lot of (justifiable) criticism for changes to its API that make it somewhat developer-hostile. But it has to be said that developers don’t always behave responsibly when they’re using the API.

The classic example of this is the granting of permissions. James summed it up nicely: it’s just plain rude to ask for write-access to my Twitter account before I’ve even started to use your service. I could understand it if the service needed to post to my timeline, but most of the time these services claim that they want me to sign up via Twitter so that I can find my friends who are also using the service — that doesn’t require write access. Quite often, these requests to authenticate are accompanied by reassurances like “we’ll never tweet without your permission” …in which case, why ask for write-access in the first place?

To be fair, it used to be a lot harder to separate out read and write permissions for Twitter authentication. But now it’s actually not that bad, although it’s still not as granular as it could be.

One of the services that used to require write-access to my Twitter account was Lanyrd. I gave it permission, but only because I knew the people behind the service (a decision-making process that doesn’t scale very well). I always felt uneasy that Lanyrd had write-access to my timeline. Eventually I decided that I couldn’t in good conscience allow the lovely Lanyrd people to be an exception just because I knew where they lived. Fortunately, they concurred with my unease. They changed their log-in system so that it only requires read-access. If and when they need write-access, that’s the point at which they ask for it:

We now ask for read-only permission the first time you sign in, and only ask to upgrade to write access later on when you do something that needs it; for example following someone on Twitter from the our attendee directory.

Far too many services ask for write-access up front, without providing a justification. When asked for an explanation, I’m sure most of them would say “well, that’s how everyone else does it”, and they would, alas, be correct.

What’s worse is that users grant write-access so freely. I was somewhat shocked by the amount of tech-savvy friends who unwittingly spammed my timeline with automated tweets from a service called Twitter Counter. Their reactions ranged from sheepish to embarrassed to angry.

I urge you to go through your Twitter settings and prune any services that currently have write-access that don’t actually need it. You may be surprised by the sheer volume of apps that can post to Twitter on your behalf. Do you trust them all? Are you certain that they won’t be bought up by a different, less trustworthy company?

If a service asks me to sign up but insists on having write-access to my Twitter account, it feels like being asked out on a date while insisting I sign a pre-nuptial agreement. Not only is somewhat premature, it shows a certain lack of respect.

Not every service behaves so ungallantly. Done Not Done, 1001 Beers, and Mapalong all use Twitter for log-in, but none of them require write-access up-front.

Branch and Medium are typical examples of bad actors in this regard. The core functionality of these sites has nothing to do with posting to Twitter, but both sites want write-access so that they can potentially post to Twitter on my behalf later on. I know that I won’t ever want either service to do that. I can either trust them, or not use the service at all. Signing up without granting write-access to my Twitter account isn’t an option.

I sent some feedback to Branch and part of their response was to say the problem was with the way Twitter lumps permissions together. That used to be true, but Lanyrd’s exemplary use of Twitter for log-in makes that argument somewhat hollow.

In the case of Branch, Medium, and many other services, Twitter authentication is the only way to sign up and start using the service. Using a username and password isn’t an option. On the face of it, requiring Twitter for authentication doesn’t sound all that different to requiring an email address for authentication. But demanding write-access to Twitter is the equivalent of demanding the ability to send emails from your email address.

The way that so many services unnecessarily ask for write-access to Twitter—and the way that so many users unquestioningly grant it—reminds me of the password anti-pattern all over again. Because this rude behaviour is so prevalent, it has now become the norm. If we want this situation to change, we need to demand more respect.

The next time that a service demands unwarranted write-access to your Twitter account, refuse to grant it. Then tell the people behind that service why you’re refusing to sign up.

And please take a moment to go through the services you’ve already authorised.