Things I learnt about passkeys when building passkeybot

by emadda • 7 months ago

173 146 7 months ago

BoppreH• 7 months ago

Love these "lessons learned" posts, keep the coming!

My only feedback is about the Quickstart of passkeybot, "feed this example into a good LLM with these instructions". I undeerstand the idea, but I was a bit shocked that the first time I see these sort of instructions is for an auth framework.

loloquwowndueo• 7 months ago

How to add passkeybot support to your site, according to their official guide:

start

(1) Copy / paste example_http_server into your LLM of choice (use a paid/good model). (2) Prompt: Implement the HTTP handlers here for my project,..

Um, no? How about you give me real instructions on how to do it? I’m not going to delegate a security-critical task to an LLM. And since I need to review it carefully myself anyway, I might as well write it all by hand, right? Like, the whole premise is I just need to implement a couple of webhooks.

gear54rus• 7 months ago

It's absolutely hilarious that someone would think that this passes for API docs nowdays. Still it's good to know what to avoid on the very first glance.

jiggawatts• 7 months ago

It's also a bit of a "bootstrapping" issue. How does anyone expect the AIs to learn to do things correctly if the instructions are not published for them to pick up during training?

This is like those "contact your system admin" error messages. I am the system admin!

the_mitsuhiko• 7 months ago

I think it's good. Quite frankly, it's the better experience to be given the right prompts to onboard into something than having to guess that the inputs are the right for the LLM.

emadda3• 7 months ago

Yes, that is true, I was assuming that any LLM code was going to be checked by the developer. Step 7 in the guide is "review your code and ensure the important logic commented in the example server is still present".

The LLM is only for converting the JS based example code into your language X and HTTP framework Y (instead of giving example code for every combination of X and Y).

The standard implementation is in a single file `http_server.ts`, which is around 200 lines of well commented code, with important logic commented (around 5 lines). The example code can be run locally with a few commands.

The repo also contains a sequence diagram [1], a description of the HTTP handlers needed [2], and a live demo [3] where you can see the request/responses.

Thanks for your feedback I have made this clearer in the readme.

- [1] https://github.com/emadda/passkeybot/tree/master?tab=readme-...

- [2] https://github.com/emadda/passkeybot/tree/master?tab=readme-...

- [3] https://demo.enzom.dev/

ChrisMarshallNY• 7 months ago

Thanks for that!

I am in the middle of writing a passkey-driven server dashboard app (native SwiftUI app, with a small server component).

In the future, I would like to use passkeys as much as possible, but they do present a bit more friction to users than Sign in with Apple. When I was initially learning them I wrote this up: https://littlegreenviper.com/series/passkeys/

tptacek• 7 months ago

Regarding PKCE, the way I remember it is that OAuth2 was deliberately designed to eliminate as much actual cryptography as possible, relying instead on same-origin and TLS security; PKCE is one of the few things that introduces an actual cryptography primitive.

boombapoom• 7 months ago

i wish passkeys could replace passwords, not suppliment them

spockz• 7 months ago

Why? Passwords can be remembered and entered on other devices for recovery. The plethora of passkeys out there cannot.

A bit the same why although I love the keychain in macOS, it also makes me uncomfortable. Lose your phone and laptop in a theft or fire and you are locked out from your Apple account. Goodbye online presence.

wkat42424• 7 months ago

That's exactly the issue I have with passkeys. All that lockin to big tech. I tried bit warden but most sites with passkeys didn't work with it (like Amazon and PayPal). And on android it only wants to use the Google version (I don't use a Google account on my phone so that's not possible).

AlotOfReading6• 7 months ago

The "standard" answer is that you should either use synced passkeys, or enroll multiple passkeys with the provider. The problem is that some providers (e.g. Paypal, some banks) only support one passkey, and synced passkeys aren't supposed to be trusted for attestation (unless they're synced by Apple/Google/Microsoft).

ianburrell• 7 months ago

Passkeys work well with password manager. The password manager also stores the long random password to get in without passkey. The advantage is that passkeys are immune to phishing. Sites also turn off 2FA for passkeys which reduces the hassle.

AlotOfReading6• 7 months ago

And I wish passkeys could cover all the use cases of passwords, yet here we are. Passwords are simple and well understood. Passkeys have all sorts of sharp edges that you won't discover until you're hurt by them.

yawaramin4• 7 months ago

Passwords are also simply phished, and many people have discovered those sharp edges by getting their accounts hacked.

xg15• 7 months ago

generateKey is a JS API that allows you to create new key pairs, where the private key cannot be extracted similar to passkeys.

Is that "cannot be extracted" from JS only, or is this an actual device-locked, TPM/SEP-bound key like passkeys?

If it is, it seems kind of like the buried lede to me that there is a browser API that lets any website built its own completely unstandardized quasi-passkey system and lock the key to the current device.

ajross• 7 months ago

Yes, where practical. Though recognize that by their very nature web apps aren't part of the trust network. The browser and security stack can make a key for them to use, but it's not possible to be sure that the user of that key is not subject to attack at the backend (or even front end, really the best you can do there is XSS protection, which is hardly at the standard of "crytographically secure").

And likewise you as the app vendor can know the key was generated, and that it works, but you can't[1] know that it's actually locked to a device or that it's non-exportable. You could be running in a virtualized environment that logged everything.

Basically it's not really that useful. Which is sort of true for security hardware in general. It's great for the stuff the device vendors have wired up (which amounts to "secured boot", "identifying specific known devices" and "validating human user biometrics on a secured device"), but not really extensible in the way you'd want it to be.

[1] Within the bounds of this particular API, anyway. There may be some form of vendor signing you can use to e.g. verify that it was done on iOS or ChromeOS or some other fully-secured platform. I honestly don't know.

machinationu2• 7 months ago

it's possible with CPU secure attestation, but it's not something you will encounter on regular personal computers.

the capability is there, but it would he massively inconvenient, since it requires a lot of lockdown

might be the next generation of anti-cheats though

smallnix• 7 months ago

In oauth2: when I /1 associate a random uuidv4 for each new flow with my user (server side), /2 stick that uuid into the state parameter, and then /3 look up my user with this on callback-endpoint execution. Isn't PKCE in that case redundant?

esseph2• 7 months ago

If you can, switch to uuid v7 if you're indexing by that id. Performance improvement while still not being sequential IDs.

SahAssar3• 7 months ago

For this sort of use-case v4 might be better. It has more randomness and you will probably delete the old ids as soon as they are used anyway, so the indexed space will probably be small.

SahAssar3• 7 months ago

I think one point of PKCE is that the oauth token is never sent to the client (it is exchanged on the backchannel), so it theoretically is more protected.

Of course if you trust the client (no bad browser extensions, updated browser) and have good TLS settings and no MITM risk and make sure the your IDs are single-use then it seems like that should be fine.

gethly• 7 months ago

Oauth's PKCE verifies the continuity of the flow as it is essentially a saga(multi-step process). For example you can initiate oauth access grant request multiple times with the same data, but PKCE ensures that each of those initiations can be individually identified. Do not confuse PKCE with state field, which is for XSS and has no obfuscation.

Just to be clear, the PKCE secret can be the same for each initiation, but in the end its goal is to ensure that the first request matches with the last one. And yes, there is "plain" PKCE method but that is just for testing. SHA256 is the default one used to obfuscate the secret.

ximm2• 7 months ago

I also think these are very similar. The main difference in my view is that the state parameter is checked by the client, while PKCE is checked by the server.

I run an authentication server and requiring PKCE allows me to make sure that XSS protection is handled for all clients.

emadda3• 7 months ago

PKCE protects the auth token from interception by making it so that only your code that started the flow can redeem it by proving they have the secret code_verifier on the redeem_token() call.

The code_challenge == sha256(code_verifier). You will share the code_challenge at the start of the flow.

EGreg• 7 months ago

The authenticator GUI only shows “sign in to your_domain.com”. It never allows a more general “sign this content for your_domain.com”. E.g. “sign this transaction request to move £50 to Bob's account”.

That is why you should ship a pristine HTML+CSS+JS environment that can use subtle web crypto. YOU show what is being signed. And then the device can sign its hash using the secure enclave.

And you CAN do attestation even on consumer devices, by using the Device or AppAttest framework (I think that’s what it’s called). I did it myself in our app. It does show up 100% of the time but when it does it’s useful.

PS: being the web3 / blockchain geek that I am, I will tell you stuff that triggers anticryptobros on HN.

The Web3 ecosystem already has a standard called EIP712 for signing structured data. If you want to stick to standards, use that!

The secure enclaves all use P-256 (sometimes called R-256) while Bitcoin / Web3 uses K-256 (the Koeblitz curve, they distrust the NIST curve or whatever).

So that means you’re going to have to use Abstract Accounts and the new precompiled smart contracts to verify P256 signatures, which only Binance Smart Chain and a handful of other chains have deployed. Luckily BSC is the most widely used chain by volume and has plenty of money sloshing around so you can build your trustless programs there. If you want to be totally trustless — LET THE SMART CONTRACTS GENERATE THE CHALLENGE TO BE SIGNED BY THE AUTHENTICATOR. Then have it sign the temporary k256 public key (from the keypair) to use, as long as your session is open you can then add use your private key to sign transactions. As usual, do this for small amounts per day, transactions that move larger amounts should still require use of multisig keys etc.)

QGQBGdeZREunxLe• 7 months ago

Computerphile added a passkey video today https://www.youtube.com/watch?v=xYfiOnufBSk

emadda3• 7 months ago

I just watched this, it is very good.

coldpie12• 7 months ago

The passkey spec authors think websites should be able to ban clients which allow users to manage their own data[1,2]. It makes me really hesitant to adopt passkeys if my client could get banned because it's open source and lets me control my client how I want to. It appears to be more useful for vendor lock-in than anything else[3]. A shame, since it could've been a cool tech if they had built it to be resilient to this kind of abuse, but it's clear they think vendor lock-in is actually a core feature of the protocol.

[1] Spec author quote: "To be very honest here, you risk having KeePassXC blocked by relying parties." https://github.com/keepassxreboot/keepassxc/issues/10407#iss...

[2] https://www.smokingonabike.com/2025/01/04/passkey-marketing-...

[3] https://fy.blackhats.net.au/blog/2024-04-26-passkeys-a-shatt...

yawaramin4• 7 months ago

Apple doesn't do attestation, so effectively this feature is dead in the water.

lelandbatey• 7 months ago

Per the article, Apple does do attestation. By default attestation is off unless you have enterprise management turned on.

But the existence of attestation means Apple could at any time in the future make attestation on by default and suddenly our devices control our secrets more than we do.

jeroenhd9• 7 months ago

The point of passkeys is that they're unexportable. Software implementations like Bitwarden/KeepassXC/etc. making them exportable go right against the point of the protocols.

I personally think the ability to export+import passkeys is a good thing from a backup point of view, but he's not wrong in suggesting that companies actually using the high security features of passkeys will eventually block software implementations like these.

This isn't about vendor lock-in. Nobody is asking for KeepassXC to remove passkey support. This is about security software implementing an API and not fulfilling the expectations that come with such an implementation. To quote the comment you linked:

That's fine. Let determined people do that, but don't make it easy for a user to be tricked into handing over all of their credentials in clear text.

coldpie12• 7 months ago

It's fine for them to make suggestions for projects to improve their software. The problem is threatening clients with being banned because they don't agree with those suggestions. If a website is able to ban me because of the passkey client I'm using, then I'm just not going to use passkeys. It's too unreliable.

personally think the ability to export+import passkeys is a good thing from a backup point of view

It's not a "good thing," it's absolutely critical. If I can't back up my credentials in a location that I trust, then it's not an acceptable login method. What happens if my PC goes down and I couldn't export my data? I just can't log in anywhere? KeePassXC lets me do that, but the spec authors think it's appropriate to ban me for using it because it lets me manage my own data. That's bonkers.

nabogh• 7 months ago

I agree with you but the whole thing makes me uncomfortable. We're definitely making it easier for these security conscious companies to do vendor lock in if we encourage passkey use.

stubish• 7 months ago

But the natural result is vendor lock in. To stop exports of keys, sites will need a whitelist and secure method to verify the hardware or software implementation has not been tampered with. If an implementation is banned, the obvious solution is to allow it to pretend to be a non-banned implementation. Or admin level processes smuggling keys out of approved implementations. I don't think anyone wants an arms race, thus the vague threats to remove features that users are demanding before they will consider buying into the ecosystem.

sigmar• 7 months ago

Both things can be true:

1) that they're enforcing these specs for technical reasons, not because they want vendor lock-in

2) a result of these decisions in the long term is vendor lock-in

xoa2• 7 months ago

The point of passkeys is that they're unexportable. Software implementations like Bitwarden/KeepassXC/etc. making them exportable go right against the point of the protocols.

No, that is absolutely not the point. The points of using pub/priv keys for asymmetric auth instead of passwords (symmetric, manually generated auth) are:

- Server-side (ie, central point) hacks no longer matter an iota from a user auth pov. No more having to worry about reuse anywhere else, about going around changing passwords, nada, because the server simply doesn't have anything that can be used for auth anymore at all. No more concerns about whether they're storing it with the right hash functions or whatever, they could publish all the public keys in plain text and it'd be irrelevant. This fantastically changes the economics of attacks, since now instead of hacking one place and getting thousands/millions/hundreds of millions of credentials you'd have to hack every single separate client.

- As a practical matter, the process means eliminating the whole ancient hodgepodge of password requirements (often outright anti-security) and bad practices and manual generation work. Everything gets standardized on something that will always be random, unique, and secure.

And that should be it. That's the point and the value, always was. The only goal should be to put a nice UX and universal standard around. But of course, modern enshittified tech being enshittified, they had to shove in a bunch of stupid fucking bullshit garbage like what you're talking about.

Spivak• 7 months ago

At this time I'm not really sure if anyone can really say there's a 'point' to passkeys anymore. They just are exportable now, both Google's and Apple's implementation are synced instead of device-bound putting them at the level of Bitwarden / KeepassXC. Backups and multi-device have become a critical feature for users which breaks attestation so it's really just those weirdos with Yubikeys.

I think we're verrry slowly inching toward shedding all the security nerd self-indulgences and getting to what I think is the eventual endgame which PassKeys are just keys and ultimately a fairly user friendly way of getting people to use a password manager without it feeling like one. All the other features seem like noise.

otterley4• 7 months ago

So if a client ever goes rogue someday (either intentionally or has been compromised) and starts shipping off private material to a malicious third party, you think relying parties shouldn’t have the option not to trust that client anymore?

pjc503• 7 months ago

Doesn't doing so necessarily lock out all the users using that client?

coldpie12• 7 months ago

Sure that's bad, but the trouble is you're not thinking about what the alternative is. If users don't have control over their own data, then someone else does.

As stated by the spec authors on KeePassXC's bug tracker, open source software may be modified by the user, so cannot be trusted. The passkey proposal is for all of your keys to be managed by proprietary software validated by your phone or your computer's TPM module. That means one of three big, US-based tech companies will control all of the world's login data. Those 3 companies are all currently involved in the largest fascist-taint-tongue-polishing in US history, and we want to hand them control over the world's logins. That's a much, much bigger risk than some users doing something stupid.

The spec needs to be written with the assumption that the user's private keystore may be hostile to the user's own interests, because in the real world, it is. It needs to be written to mitigate damage to the user from a hostile keystore. Instead, the spec places total trust in the keystore. This is a fatal error.

godelski5• 7 months ago

A few weeks ago I had a bug with bitwarden where every passkey wanted to load from the macbook instead of bitwarden. I ended up being locked out of a few accounts that didn't have OTPs as a fallback. Mostly inconsequential stuff like Twitter.

I love passkeys, but they're still kinda hard to use. There's several sites that wont let you enroll multiple ones and it's easy for systems to step on each other like the aforementioned experience.

The problem is fallback. All my banking apps have SMS OTP fallbacks and that's no better than having only SMS OTP. If you're building these systems make sure you have good fallbacks. What matters in design is not so much how well it works when things go right but how well it works when things go wrong. With security you really cannot ignore edge cases

awesome_dude• 7 months ago

I read this thinking "The BEST security is the WORST usability, and vice versa"

The easier it is to do things, like use another channel, the harder it is to keep secure.

The easier it is to keep secure, the harder it is to use.

jeroenhd9• 7 months ago

I don't think this is a security vs usability thing. A lot of UIs are intentionally confusing.

Apple wants you to use iCloud passkeys, Microsoft wants you to use Microsoft Account passkeys, Google wants you to use Google passkeys. Even if you have a dedicated USB device plugged in, browsers keep defaulting to the cloud accounts.

Bitwarden's approach is to simply hijack the passkey request before the browser can respond and throw itself front and center. It's a terrible hack but it works on every browser at the very least.

If these companies cared about their users more than they cared about throwing up walled gardens, they wouldn't put a USB key behind "Choose another method" -> "Dedicated device" -> "Security key" -> "Confirm" while offering one-click login with their cloud account. And they would offer a proper API for third party applications to integrate into the native passkey storage.

godelski5• 7 months ago

That's one way to read but I think a narrow way. Besides, my issue wasn't actually an issue with security now was it?

In practice we don't actually want the best security though. We frequently make concessions. I mean with my bank I don't want "the best" security. If I lose my credentials I don't want to go broke. If my credentials get hacked (especially if hacked by no fault of my own!) I want that money recovered. These things would not be possible with "the best" security.

In fact, in a different interpretation I would call those paths less secure. Ability to recover is a security feature just as much as it's not.

Both security and privacy do not have unique all encompassing solutions. They are dependent upon the threat model.

Importantly when designing things you have to understand modes of failure. When you design a bridge you design it to fail in certain ways because when/if it fails you want it to do so in the safest possible way. Why does this pattern of thinking not also apply here? It seems just as critical here! In physical security you also have to design things for both fail open and fail closed. You don't want you always fail close, doing so gets people killed! So why is the thinking different in software?

Not to mention:

How do I login from my Linux machine if I'm only using my iCloud key?

Your logic would lock me into the apple ecosystem forever and that's a worse security setting than anything else we discussed. Apple decides to become evil and I'm just fucked. Or swap Apple with Microsoft who is actively demonstrating that transition

morshu9001• 7 months ago

Some of the things that came out before passkeys were harder and not more secure, like OTP. Especially the way that earlier versions of Google Authenticator implemented it. We're finally close to a permanent "remember me" button that most people wanted, but it needs a bit more polishing.

xandrius• 7 months ago

If you're using Firefox, it's a known bug and you can fix it by reverting the bitwarden extension and then wait for the fix.

nixosbestos2• 7 months ago

Can you give any more details about this? I had bumped into this and couldn't figure out if it was actually Bitwarden extension but or a Firefox bug.

xboxnolifes• 7 months ago

All my banking apps have SMS OTP fallbacks and that's no better than having only SMS OTP.

In terms of security, yes. But not in terms of convenience.

quantummagic2• 7 months ago

The scariest thing is the casual mention of the Digital Credentials API[1]. Forget passkeys, when you need government issued credentials to surf the net, the good times are over.

[1] https://developer.chrome.com/blog/digital-credentials-api-sh...

jeroenhd9• 7 months ago

There are plenty of websites and services already where you need to prove your identity to use them. The digital credentials API is an attempt to standardise that which is already legally required in the US, the UK, Australia, and the EU, except without having to upload a picture of your ID to a shady third party website.

quantummagic2• 7 months ago

I've never had to upload my government ID to any site; and none of my family have either. It's beyond naive to think that enshrining such a protocol won't lead to more widespread adoption, and even legislation requiring it. It's infrastructure that is quietly being built first, and enthusiastic authoritarian governments will eagerly embrace it.

realusername• 7 months ago

Have you read their document? They require Google Wallet with the Google Play Services to prove your id on your desktop computer, it's absolute insanity. No thanks.

I've never seen a legitimate use case where I need to prove my identity to use a website anyways.

pjc503• 7 months ago

The UK law is age verification not identity verification. Now, everyone in practice has collapsed that distinction, whether from incompetence or malice..

mariusor4• 7 months ago

It's likely that the websites need your actual government issued credentials are not your twitters and your hacker news, but government websites that actually need to link the web user to the citizen. As an example my country has a portal that you use as a citizen to book appointments to government institutions, keeps you updated about the status of your requests, allows you to securely upload scans for additional documents that your request might need, etc.

arccy• 7 months ago

until your gov decides that websites need to age-check everyone with the equivalent of showing some ID...

IgorPartola3• 7 months ago

One thing I ran into recently when I played around with passkeys is the problem of orphaned keys. Basically if I log into a website using the passkey and then go to my account settings and remove that passkey then log out I have a problem. Now I can’t sign in but when I go to recover my account iOS/macOS will refuse to create a new passkey because one already exists for this website. So I have to go to my passwords list and manually remove it. I believe I was correctly using the JS API for signaling orphaned keys but the OS still wouldn’t remove it so it was a situation of having to educate the user to remove the orphaned key manually (and hoping the user doesn’t get confused and remove the wrong key). You also apparently can’t create more than one passkey for the same username and the same website. So if I initially create an account from my MacBook and the passkey gets listed as “MacBook”, I then go to log in from my iPhone and it still uses the “MacBook” passkey because of iCloud sync. But this is confusing because I cannot have an iPhone key.

Overall it’s not terrible but I think these edge cases are going to keep biting people and need to be addressed in some way. And yes I understand that I could use a Yubikey or Bitwarden or some such but the point was that I wanted to see how this flow works for “normal” users who just use the iCloud Keychain and the experience leaves something to be desired.

bobbylarrybobby• 7 months ago

Why would a website leave you with an account but no way to log in aside from the account recovery procedure?

IgorPartola3• 7 months ago

You register from your MacBook, then add your Android phone, then remove your MacBook key, the lose your Android phone.

The messed up thing is that the simplest backup option is a magic login link which is obviously less secure. Also you cannot sink a passkey between platforms unless you use a third party Authenticator so you have to have a backup method of some sort even if not for recovery reasons.

godelski5• 7 months ago

  > So if I initially create an account from my MacBook and the passkey gets listed as “MacBook”, I then go to log in from my iPhone and it still uses the “MacBook” passkey because of iCloud sync. But this is confusing because I cannot have an iPhone key.

Now try using a Windows or Linux computer...

This is why I strongly prefer to not use OSX passkeys. How the fuck am I supposed to login on my nix machines if you only allow me to enroll one passkey?!

IgorPartola3• 7 months ago

Which Linux? And are you saying Windows an Linux options are better or worse?

wewewedxfgdf• 7 months ago

Learning and building an outsourced security system at the same time ..... urgh.

WolfeReader• 7 months ago

For coders, building can be a great source of learning.

Example: this article.

arjie2• 7 months ago

If I'm being honest, I regret every passkey I ever made. With my old flow, I knew when to use my Yubikey, when to use my OTP, and when to use SMS 2FA. With the new flow, these things say "use your passkey" and I don't know where in god's name I did this. If I did this on my iPhone in a WebUI that popped up when I followed a link to buy something, then it's never going to be on Chrome or Bitwarden.

I've decided to stop adding new ones. I'll just OTP 2FA. It's simple, reliable, and I can keep it in Bitwarden safely.

ChadNauseam• 7 months ago

I can't blame you. I know the passkey UX on Windows was absolutely horrible (and probably still is). However I can't say that I relate. I use 1Password and I don't think I've literally ever been asked to use the native UI. It always goes straight to 1Password. I'm not sure why we have different experiences. (I use a mac, an iphone, and a google pixel)

arjie2• 7 months ago

1Password has then implemented things better. I have a Mac, an iPhone, and a Linux desktop. I don’t know why I’m in this state. PEBKAC is entirely possible but OTP 2FA is foolproof for this fool.

comex• 7 months ago

It's all a bit of a mess right now, but with some fiddling in settings you should be able to get your passkeys in one place (probably Bitwarden) and access them everywhere.

Safari on iOS can store and use passkeys from any app that implements the right system API, including the default Apple Passwords but also Bitwarden and Chrome.

For desktop, you can either use a browser extension provided by some password managers (such as Bitwarden), or if you're on a Mac, Safari and Chrome can access passkeys from other apps similarly to on iOS (but not as many providers support this API on Mac as on iOS, and in particular Bitwarden doesn't, so you'd have to use the extension for that).

PunchyHamster• 7 months ago

But much of the recommendations say to use the counter as a heuristic rather than evidence of a cloned authenticator because there are many legitimate reasons the counter can be wrong.

I'm curious on why there would be any legitimate reason for that. Security wise it should not happen, it's just some implementations being crappy or some bad practice like reusing same passkey with different devices ?

js2• 7 months ago

BTW, if you're looking for something minimal that you can self host, say for a home lab environment, I landed on Pocket ID:

https://pocket-id.org/

Things I learnt about passkeys when building passkeybot

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