[sebk]

WebAuthn goes to great lengths to preserve user privacy, much more so than past alternatives, so I don't think there's a expansion of information, especially when the device is probed for capabilities which is extremely pervasive with browsers today. There is some new info with attestation, but other than it not being very widespread in practice, attestation keys are shared by a minimum of 100k devices.

In general, the intent of attestation seems to be enterprise use cases where companies want to issue authenticators that meet certain capabilities, and only allow those capabilities as attested by a trusted party. For instance, a company might mandate Webauthn with user verification for their internal systems, and they don't want an employee using a software based virtual authenticator that fakes UV and keeps key material in plain text, so they issue Yubikeys to their staff and only allow Yubikeys to be used for logging in (issued or otherwise, as the RP can't differentiate them). I have not seen a single instance of attestation being used to gatekeep access to an otherwise public service, but I'd like to see some examples if there are any. Enterprise attestation is a different beast, however, and can uniquely identify an individual security key, but this has significant management overhead and will not be seen outside of enterprise use cases.

Now I understand you personally don't value attestation as highly as some other features of WebAuthn and that's fine, I'm on the same boat. However that's the nature of standards and how they come about, there's multiple interests in the working groups. It's hard to say what's the "biggest" security increase because that's entirely relative to the individual or corporation implementing, consuming, or standarizing the functionality.

As to whether there can be a phishing-resistant trust-establishment mechanism, I absolutely agree that there can be. All I'm saying is that there isn't an interoperable one currently, and that it's hard to establish interoperability across vendors and without an online sync fabric (I'd presume most users would want to export key material to a file or otherwise not rely necesarily on a third party phone-home service to export keys). I also think that it exceeds the scope of FIDO and will have to be primarily OS-vendor-driven. For me, personally, this along with something like the recovery extension that Yubico is promoting is one of the potential future features I'm most excited about.

Related, and for the other reason why import/export is hard, which is the reasoning about the ecosystem, I don't think that even with such a mechanism we'll ever be able to export keys out if iCloud Keychain and into KeePassXC. What will most likely happen is that credentials generated by KeePaasXC and backed by hardware, will be able to be imported/exported in/out of devices in the same trust circle, using a KeePassXC sync fabric as the sync mechanism.

[danShumway]

> There is some new info with attestation, but other than it not being very widespread in practice, attestation keys are shared by a minimum of 100k devices.

I would question whether 100k devices is actually a big enough pool to protect privacy. Regardless, that is "an expansion of information", right? It's a pretty decent fingerprinting vector to start with when combined with other device information.

> For instance, a company might mandate Webauthn with user verification for their internal systems, and they don't want an employee using a software based virtual authenticator that fakes UV and keeps key material in plain text

At the point where a company is in that position, they should be supplying their own locked down devices. This is an extremely narrow use case, much more narrow than "I'd like to be able to use this on a Linux machine." And the companies that are in that position have much greater resources to solve that problem by issuing dedicated hardware that's locked down in general. It doesn't need to be part of the spec.

In practice, where this will be used most often is with banking apps, which I've argued elsewhere are not nearly responsible enough to be trusted with this extra information and are usually startlingly insecure. They can get on board with basic security techniques that the rest of the industry has already implemented before we discuss giving them more control over my hardware.

People keep billing this as a compromise, but it's not really. The attestation proponents are asking for a capability that doesn't exist, they're asking for a level of insight into my hardware that login methods have never provided before. The status quo is "no, of course you don't get that." If they want to change the status quo, asking for "compromise" isn't the way to do it, providing real proof that it's not going to be abused (which, I'll mention in a second I don't think is safe to assume) and that it'll provide meaningful security increases is where they should start.

> I have not seen a single instance of attestation being used to gatekeep access to an otherwise public service, but I'd like to see some examples if there are any.

Continuing from the above, I've seen both intent (https://developer.apple.com/forums/thread/708982) and practice (https://arstechnica.com/civis/threads/passwordless-google-ac...).

Also attestation in the form of SafetyNet (https://developer.android.com/training/safetynet/attestation) and the more recent Play Integrity API has been used for DRM in plenty of instances, even for very trivial services like Netflix. So it seems pretty reasonable to extrapolate out that services that already use attestation for DRM today are going to use it when it's available for WebAuthn.

The default assumption ought to be that this is going to be abused. Every instance of attestation in the past has been abused. Why would we just assume that suddenly companies are going to be nice about it?

> However that's the nature of standards and how they come about, there's multiple interests in the working groups.

Right, and the way you force that collaboration is by refusing to go along with standards that are harmful. I'm not part of this standards process, it's their job to build a standard that appeals to me if they want me to use it. If they can't do that, then I won't use it. And I'll advise other people not to use it and I'll tell people (truthfully) that I believe it's a harmful standard. As users/stakeholders, we force collaboration by laying out very clearly where our limits are so we can focus on finding solutions that solve multiple use-cases.

I'm willing to compromise on a lot of stuff. Not this. If the big stakeholders also aren't willing to compromise on it, then we'll stick with passwords. That's fine with me. The FIDO group doesn't have an inherent right to have people pay attention to them. It's their job to come up with a standard that's good enough that people want to pay attention to it.

> All I'm saying is that there isn't an interoperable one currently, and that it's hard to establish interoperability across vendors and without an online sync fabric

Some of us would argue that is also entirely the FIDO Alliance's problem to solve given that they exist to build the FIDO standard and are the most invested party in getting the rest of us to adopt their solution.

Normally when people get together to build Open standards, they start with an Open implementation as a proof of concept. FIDO Alliance seems to be under the impression that it's everyone else's problem that nobody has built an Open implementation of their "Open" spec for them. That's just not how this should work.

> and will have to be primarily OS-vendor-driven

It's a good thing that all of those OS-vendors are part of the FIDO Alliance and are currently involved in a process that provides them with a great opportunity to sit down with each other and hash this out then.

> What will most likely happen is that credentials generated by KeePaasXC and backed by hardware, will be able to be imported/exported in/out of devices in the same trust circle, using a KeePassXC sync fabric as the sync mechanism.

That wouldn't solve any of my problems; the sync fabric isn't the important part -- I want to control my own keys. What does an "Open" sync fabric that restricts keys to specific devices even look like? That's certainly not Open in the sense that I control the sync fabric or can compile/change it myself.

[sebk]

100k devices is the minimum. Also I already agreed that this is an expansion of information, were it to be requested in practice and the user chose to provide it. And I don't believe the use case for attestation in enterprise settings is narrow. For the "own locked down devices" is that Enterprise Attestation exists, which has management overhead in both its configurations, wheras normal attestation does not.

I can't comment on the intent link, as there's no information. But the "practice" link is simply incorrect. Google does in fact allow a Yubikey to be used as a passkey, I have one configured myself. It shows up as "FIDO2 security key". What I assume is happening in that link you sent is that the user's yubikey does not have a PIN set for the FIDO2 interface, which means that it can't provide user verification and therefore is not a passkey as far as Google is concerned. This is the kind of reasoning about the capabilities of the authenticator that I was talking about, and it doesn't have to do with attestation.

> it's their job to build a standard that appeals to me if they want me to use it

They're appealing to OEMs, vendors and service providers as well. I also don't quite see how merely having attestation in the standard is harmful. RPs and users can chose not to require or provide it. If RPs decided they needed it for malicious purposes, would not having it in the standard suffice for them to be benign?

> That wouldn't solve any of my problems; the sync fabric isn't the important part -- I want to control my own keys.

It would, because then the sync fabric is free to provide you with an exported version that's wrapped in a key of your choosing. It's open in the sense that any one software can import/export keys out of hardware devices that are currently restricted to the hardware vendor.

[JohnFen]

> I also don't quite see how merely having attestation in the standard is harmful.

Because having it there makes it an option, and I think that history is pretty clear that if you give the tech industry a bat, they will beat their users with it sooner or later.

[danShumway]

> This is the kind of reasoning about the capabilities of the authenticator that I was talking about, and it doesn't have to do with attestation.

It seems like it does though... correct me if I'm wrong, but attestation is how Google knows that it's a Yubikey and that it doesn't have a PIN/biometrics set. And in practice, it's not allowed to be used to provide user verification; there's a restriction on functionality. Yes, you can use it as a Yubikey, but you can't use it for the new passkey system.

> For the "own locked down devices" is that Enterprise Attestation exists, which has management overhead in both its configurations, wheras normal attestation does not.

Good? Attestation should have an overhead. Getting rid of the overhead is exactly what I don't want. You can have attestation today through existing methods, and they're basically sufficient for enterprises that need them. It costs a bit of money, which is good because it'll force enterprises to think about it. And importantly, it doesn't really work for restricting consumer accounts, it's mostly useful for orgs where devices are controlled. Which is again, good, that's the best outcome. Enterprises can restrict their devices, but there are barriers to entry that prevent those restrictions from being applied to general consumers using their own devices.

The other thing you can do if you don't want to go the hardware route is you can have a custom login app for your enterprise. You shouldn't, you should provide users with devices if you're going to restrict those devices -- but there's nothing stopping an org from having a custom authenticator that works outside of the standard.

The only problem they'll have is if they want general users outside of the org to install that app just to log in. Which again, is very good. It's good that you can build a custom solution for within an enterprise, but that there are significant challenges in front of trying to force that solution on regular users.

Heck, you can even use the Play Integrity API to help. Should the Play Integrity API exist? No, probably not. But it does and it's usable for dedicated authenticators, so we certainly don't need another solution on top of it.

This is a rare use-case, and it's probably fine for the orgs that need it to use something other than passkeys. There's no real danger to them of lock-out, they're already doing this today so they can just keep doing what they're already doing.

> I also don't quite see how merely having attestation in the standard is harmful.

Because every single time that we've had attestation in the past -- literally every single time -- it's been used for DRM. Hopefully this conversation doesn't matter because Apple is just blocking attestation, but what do you see in the industry that makes you think this time would be different? Has something radically changed at Netflix over the past couple of years?

When has attestation ever not been abused?

Here's the Chromium team expressing similar fears: https://www.chromium.org/security-keys/ Are those fears unfounded? I don't generally assume that Google is going to be leading the charge on user freedom, and if even they are kind of creeped out about the potential here, then I trust that there's a real risk of abuse.

> It's open in the sense that any one software can import/export keys out of hardware devices that are currently restricted to the hardware vendor.

Right, but if you're talking about trusted devices, unless that's something the user controls, exporting/importing doesn't matter. The point is that the user should be able to export their key and import it to any authenticator they choose without fear that their authenticator is going to be blocked from logging in to a service.

[sebk]

Attestation doesn't carry that information. Also consider that Apple zeroes out attestation for its devices and works just fine with Google as passkeys. What's happening here is that when an RP is registering an authenticator, it can include a property that's called userVerification which in a Yubikey is backed by a PIN, and Google sets it as required. The restriction in functionality that you mention is exactly what Google wants though, but not for malicious purposes. Google doesn't want someone stealing your yubikey and having that suffice to log in to your account. They want user verification so that if that Yubikey is stolen, an attacker also needs to know the PIN, thus providing two factors. Again, Google does not prevent you from using Yubikeys. It prevents you from using security keys that aren't configured for user verification, and they don't do that through attestation.

> Right, but if you're talking about trusted devices, unless that's something the user controls, exporting/importing doesn't matter. The point is that the user should be able to export their key and import it to any authenticator they choose without fear that their authenticator is going to be blocked from logging in to a service.

No, not just physical devices. Anything that represents a device with a wrapping key. That could be a software implementation that's just a file you control. What I'm saying though is that for the general case which is what a standard is concerned with, we won't see the standard-mandated ability to export passkeys across sync fabrics. I don't see a world where you can export passkeys from Apple iCloud Keychain and import them into Google Password Manager. But I do see a world where you create passkeys in your Mac with KeePassXC, and can use an open sync fabric from KeePassXC to sync them to your Android device, and a flat file as well, and I believe this will happen not under the purview of FIDO. Whether those flat files can then hop on to another sync fabric (say, 1Password) to later be imported into hardware devices will definitely not be a part of a standard, but given the analogy to password managers, it doesn't matter; those capabilities can still be built.

As far as the Chromium post, I find that one slightly more dystopic than attestation as a feature. They say If Chrome becomes aware that websites are not meeting these expectations, we may withdraw Security Key privileges from those sites, and similar other warnings. They don't say that they will warn users, they say that they will withdraw privileges. Do you want your browser deciding for you what websites you can log in to?

[JohnFen]

> Google doesn't want someone stealing your yubikey and having that suffice to log in to your account.

But it's not Google's place to make that decision for me.

[danShumway]

> Also consider that Apple zeroes out attestation for its devices

This may be the saving grace because it may end up being that whether or not attestation is part of the standard doesn't matter because companies won't be able to use it. But it doesn't mean that attestation is harmless, it means that we're very lucky that (for now) Apple is deciding to effectively make it impossible for a commercial service to actually use it reliably.

> It prevents you from using security keys that aren't configured for user verification, and they don't do that through attestation.

Fair point, I don't know that this is actually using attestation and that it's not just the Yubikey reporting back that it doesn't support that field. I do quibble somewhat with "they're not blocking Yubikeys, they're just blocking <description of a Yubikey>." But... yeah, I'll grant you're probably right that this is not using attestation.

> I don't see a world where you can export passkeys from Apple iCloud Keychain and import them into Google Password Manager.

That's exactly what I mean when I say it wouldn't be sufficient. When I talk about syncing, I'm talking about transferring into and out of ecosystems, not just specific devices. What you're describing is a system where I can use the KeePassXC ecosystem to use keys across multiple devices. But I can't transfer those keys out of the KeePassXC ecosystem (unless hopefully other vendors like 1Password add support), and if someone starts using iCloud, they're stuck with same vendor lock-in.

This is effectively saying, "you'll have a closed ecosystem for most people, but people who know enough beforehand to avoid it can somewhat avoid it." We should expect better from a standards body that purports to be building an Open standard.

I really don't see how this is an out-of-scope problem for the FIDO Alliance. They have input from every single major OS. All of the players are in the same space. And their entire job is to dictate how this is going to work. I'm just asking them to do that job. A spec for portability is not that big of an ask compared to everything else they're already working on as part of this.

It's not really that different than a spec for logging in using a standardized QR code, or over Bluetooth -- all of which was considered in-scope for them to to work on. Portability is just part of the general interoperability work that we should be expecting them to do.

> Do you want your browser deciding for you what websites you can log in to?

Of course not; in very typical fashion Google's solution to the problem may be worse than the problem itself. Google is very fond of recognizing that a feature is abusable and saying, "well, how about we prevent that abuse by giving ourselves even more capricious power?"

But I do think it shows I'm not being paranoid, that this is a legitimate worry that even Google recognizes is worth worrying about. Google is part of the FIDO Alliance and it's not looking at attestation as a theoretical risk; it's looking at it as a very plausible risk that it needs to have policies around.

Which I think is pretty reasonable given that every single instance of attestation in the past has been used for DRM, and there's nothing special about attestation in this spec that would stop that from happening. I really do think the burden of proof here is on you to describe why you think Netflix/Banks/etc... are suddenly going to act differently now than they have with every other attestation method they've had access to leading up to now.

The only answer I can think of is, "they'll act differently because Apple is effectively killing attestation for platform keys for everyone." But that's not really a defense of attestation, it's just something to thank Apple for.

[sebk]

let me restate, they're not "blocking the description of a Yubikey" either. You can register one, and in fact I just did to try it out. The Yubikey needs to be configured with a PIN which you do through Yubikey manager. They're blocking authenticators that don't have additional protection other than just presence.

> That's exactly what I mean when I say it wouldn't be sufficient

I think we're confusing what the role of a standard is, versus what other features can be built around a standard capability. With an open fabric, vendors like KeePassXC can allow exports in formats that can then be imported by other sync fabrics as I described previously. The standard mandating it would be a good reason for vendors not to adopt the standard, or adopt a crippled version. Given the fact that WebAuthn ties capabilites to the authenticator at registration time I think it's understandable that vendors like Apple want give RPs assurance that keys are entirely contained in an ecosystem that guarantees those assertions. You will have options, including not using Apple/Microsoft/Google's sync fabrics, and to move off these sync fabrics if you consider them insufficient, but not by exporting keys directly.

> I really don't see how this is an out-of-scope problem for the FIDO Alliance (...) It's not really that different than a spec for logging in using a standardized QR code

Logging in using a QR code or BLE is part of the hybrid transport in CTAP, which deals with how authenticators communicate with clients. It's very much within FIDO. Establishing trust between devices in different ecosystems to form a circle of trust so that key material can be shared doesn't really have anything to do with logging in to services, so it's not WebAuthn. It also doesn't deal with client to authenticator communication as there's no client. If anything, a standard like TPM (ISO/IEC 11889) is a better fit, but probably too low level for that exact use case.

> Which I think is pretty reasonable given that every single instance of attestation in the past has been used for DRM

Going back to attestation, I don't think that in general it's in the best interest of services to not allow you to log in to them, but I can see a bank in their typical backwards-fashion issuing some branded keys and only letting you use those (Symantec, I'm looking at you). The reality is that standard or not, if RPs want this functionality, it'll be there. Standards simply attempt to provide the bare minimum for interoperability that every party can agree to. The alternative is not an attestation-free world. It's a bank asking you to log in with a flawed key they purchased from an ancient vendor because there's no standard offering that does what they want. I'd much rather have a Bank of America branded Yubikey with enterprise attestation using WebAuthn than some weak and poorly implemented proprietary token like the ones they issue today.