[didntcheck]

If anything I'm worried that corporate security people will hear of "attacks" like this and blindly add "must use attestation with passkeys" to their checklists, and desktop computing will end up in the same state as mobile, where you have to have an unmodified OS install from one of a handful of authorized fiefdoms to log into your bank. It's a long way off, due to the amount of old laptops with no TPM about, but a plausible future

Edit: I may be misunderstanding the scope of attestation in a FIDO/Webauthn context. Is it a legitimate concern that it would lock out other OSes, or would you simply need a hardware key (or perhaps a TPM), but could run what you want above it?

[parliament32]

> add "must use attestation with passkeys" to their checklists

We already do. Mostly from the compliance side: I can't call passkeys "phishing-resistant" unless I can lock them down into unexportable passkey providers only. Some more details from a previous comment of mine:

From a corporate compliance perspective, I need to ensure that employee keys are stored in a FIPS-compliant TPM and unexportable. Key loss is not an issue because we have, ya know, an IT department. The only way I can ensure this happens is by whitelisting AAGUIDs and enforcing attestation.

With these factors I can also get out of the MFA hellhole (because I can prove that whitelisted vendor X already performs MFA on-device without me having to manage it: for example, WHFB requires something you have (keys in your TPM) and either something you are (face scan / fingerprint) or something you know (PIN), without me having to store/verify any of those factors or otherwise manage them). Same goes for passkeys stored in MS Authenticator on iOS/Android.

[jesseendahl]

>I can't call passkeys "phishing-resistant" unless I can lock them down into unexportable passkey providers only

I don't think this is accurate. As far as I know, no credential managers (except for maybe KeePassX) allow export of passkeys, and will instead only allow for secure transfer via the new Credential Exchange Protocol.

[parliament32]

> secure transfer via the new Credential Exchange Protocol

If it's "transferable", it's not phishing-resistant (ie it's possible for a user to get bamboozled into transferring their keys to a bad actor), right? Regardless of mechanism.

You might've missed the "FIPS" part as well. This requirement effectively means the keys (or the keys to decrypt the keys) must be stored in a tamper-resistant hardware crypto device (read: your TPM) and basically no credential managers (apart from the first-party ones we have whitelisted) use the TPM for storing your keys.

[cyberax]

> It's a long way off, due to the amount of old laptops with no TPM about, but a plausible future

TPMs can't create hardware-attested passkeys, at least they couldn't do that with the TPM 2.0 spec.

And you can just use a USB hardware token to get attested keys. Or you can use WebAuthn over Bluetooth to your phone, essentially using your phone's secure enclave (or its equivalent) as the key source.

Being able to require attested passkeys is a _good_ thing.

[ndriscoll]

Except it means backing up or moving your credentials is somewhere between a pain and infeasible, and you're requiring people to go buy another device for little to no real security benefit. Every browser already generates strong random passwords that are tied to specific sites. They've done so for many years. Passkey attestation in a non-managed-org context is trying to solve a problem that's way past the point of diminishing returns while making things more fragile for users. You also can't really do attestation without having a blessed set of vendors (otherwise a software implementation could do it), so lockin is required.

[cyberax]

> Except it means backing up or moving your credentials is somewhere between a pain and infeasible

That's the point.

> and you're requiring people to go buy another device for little to no real security benefit.

No. The benefit is clearly there: hardware-originated keys can not be stolen under any normal circumstances. Meanwhile, synced passkeys are just fancy login/password pairs, so they can be exfiltrated by an attacker. E.g. by scanning the RAM of the passkey manager.

Of course, the operating system can try to add additional barriers, but the underlying keys must at some point be in clear text form.

[ndriscoll]

Right, that makes such a system unusable for normal people, so it is not a good thing to force it upon them. The benefit is not clearly there because anything that can manipulate local memory can also just use the key directly, or if there's some kind of physical button press required, wait for the user to log in and then do whatever they want with the session cookie or alter page contents or do anything else it wants. If the token doesn't display what it's authorizing (e.g. a yubikey), you could also watch for any usage, block that request to the device, and instead auth against their bank. If you need multiple button presses (e.g. they need to press again to confirm a transfer), say there was an error and ask them to try again.

Normal people are however not concerned with these Mission Impossible scenarios, and random passwords are good enough while being easy to use without an IT department to fix when it goes wrong. A password manager (which every browser has built in) already associates passwords to domains for phishing resistance. Users already should never need to enter a password manually unless the site did something stupid to try to block the password manager from working.

[cyberax]

> Right, that makes such a system unusable for normal people, so it is not a good thing to force it upon them.

Whut? Passkeys work perfectly fine for "normal people".

> The benefit is not clearly there because anything that can manipulate local memory can also just use the key directly

Correct. But it does require fairly high level of system access. Hardware-bound keys also allow full hardware-attested authentication.

> Normal people are however not concerned with these Mission Impossible scenarios, and random passwords are good enough while being easy to use without an IT department to fix when it goes wrong.

If you're using truly random passwords, then you're using a password manager. And if you're using a password manager, then why not just use passkeys?

All the popular password managers support them: BitWarden, 1Pass, iCloud Keychain, even LastPass.

[ndriscoll]

Passkeys don't offer anything above random passwords, and hardware attested passkeys obviously cannot work with a software password manager, which is the point.

Also like I keep saying, every browser already has a password manager. You don't need an external one. Notably though, Firefox's password manager doesn't support software passkeys, so they are completely unusable for me, for example. I'm certainly not going to sign up for some SaaS so I can use a worse version of passwords.

[lxgr]

> synced passkeys are just fancy login/password pairs, so they can be exfiltrated by an attacker. E.g. by scanning the RAM of the passkey manager.

That’s an overly reductionist view.

Lots of password compromises still happen due to credential reuse across services, server-side compromises paired with brute-force-able passwords, and phishing/MITM attacks, and software-based WebAuthN credentials prevent all of these.

[lxgr]

> Or you can use WebAuthn over Bluetooth to your phone, essentially using your phone's secure enclave (or its equivalent) as the key source.

As far as I remember, attestation is fully gone on iOS ("Passkeys" or otherwise), and mostly gone on Android too.

[cyberax]

It's still there. You can request an attested credential, it just won't be synced.

[lxgr]

Not on iOS, except for devices with MDM profiles explicitly opting a given RP domain in.

It's unfortunately not possible to even request a non-synced credential anymore for non-MDM-approved websites.

[jeroenhd]

The spec tells websites to please not do validation on specific hardware. You can do a light form of remote attestation, but you'll have to convince the user to use passkeys only and not some kind of username+password backup, which is still a tough sell.

If you want remote attestation, Safari already has it, but I'm not sure if their attempt at standardising is going anywhere. It's been a while since the draft got updated or mentioned anywhere.

[lxgr]

> If you want remote attestation, Safari already has it

No, Safari/Apple gave up on remote attestation when they introduced passkeys, except for MDM devices where the MDM profile can allow attestation for RP domains on an opt-in basis.

[jesseendahl]

>except for MDM devices where the MDM profile can allow attestation for RP domains on an opt-in basis.

And even then, the attestation you get in that scenario is just an attestation that the passkey was created on a managed device. It is not a hardware/device attestation.

[lxgr]

But only Apple devices can be managed, and presumably that’s in turn attested to by Apple cryptographic keys in hardware?

[lxgr]

If this "attack" convinces security people of anything that just thinking through the FIDO/WebAuthN specs and threat model didn't already, I'd be concerned about the general quality of their work.

[mjg59]

The attestation is purely the MFA token, not the OS

[tialaramex]

It is still almost always unwanted garbage though, which is why the specification says please don't.

We know from the Web PKI how this goes. People who have no idea what they're doing copy-paste a "good" list in 2025, but in 2035 the fact a third of vendors on that "good" list are now known villains and another third went bankrupt doesn't change the problem that stuff on the list works and everything else doesn't, because it was mindlessly copy-pasted

Narrowly, the vendor attestation could make sense if you're BigBank and you bought every employee (or maybe every customer, I wish) a FooCo security key, you can require FooCo security keys. If you're big enough you could have FooCo make you a custom model (maybe with your company logo) and attest every key is the custom model. I expect Yubico would sell you that product, if you were willing to commit to the volume. You get assurance of the exact hardware properties, and you retain the option to shop around by updating your software to trust different attestation. IMO not worth standardizing, but people really wanted this and better it exists but isn't used than it doesn't exist so they walk away.