A greatly simplified and opiniated wrapper to invoke the webauthn protocol more conviniently.

Check out the demos:

• Basic Demo
• Minimal Example (CDN)
• Minimal Example (repository)
• Testing Playground

REQUIRES NODE v19+!!! (because the WebCrypto is only available as crypto global starting from node 19!)

npm install @passwordless-id/webauthn

import * as webauthn from '@passwordless-id/webauthn'

<script type="module">
  import * as webauthn from 'https://unpkg.com/@passwordless-id/webauthn'
</script>

The webauthn module is basically a "bundle" composed of the following modules:

• client: used for invoking webauthn in the browser
• server: used for verifying responses in the server
• parsers: used to parse part or all of the encoded data without verifications
• utils: various encoding, decoding, challenge generator and other utils

It was designed that way so that you can import only the module(s) you need. That way, the size of your final js bundle is reduced even further. Importing all is dependency free and < 10kb anyway.

import { client } from '@passwordless-id/webauthn' 

client.isAvailable()

Returns true or false depending on whether the Webauthn protocol is available on this platform/browser. Particularly linux and "exotic" web browsers might not have support yet.

await client.isLocalAuthenticator()

This promise returns true or false depending on whether the device itself can act as authenticator. Otherwise, an "extern" authenticator like a smartphone or usb security key can be used. This information is mainly used for information messages and user guidance.

The registration process occurs in four steps:

1. The browser requests a challenge from the server
2. The browser triggers client.register(...) and sends the result to the server
3. The server parses and verifies the payload
4. The server stores the credential key of this device for the user account

Note that unlike traditionnal authentication, the credential key is attached to the device. Therefore, it might make sense for a single user account to have multiple credential keys.

The challenge is basically a nonce to avoid replay attacks.

const challenge = /* request it from server */

Remember it on the server side during a certain amount of time and "consume" it once used.

Example call:

import { client } from '@passwordless-id/webauthn' 

const registration = await client.register("Arnaud", "a7c61ef9-dc23-4806-b486-2428938a547e", {
  "authenticatorType": "auto",
  "userVerification": "required",
  "timeout": 60000,
  "attestation": false,
  "debug": false
})

Parameters:

• username: The desired username.
• challenge: A server-side randomly generated string.
• options: See below.

The registration object looks like this:

{
  "username": "Arnaud",
  "credential": {
    "id": "3924HhJdJMy_svnUowT8eoXrOOO6NLP8SK85q2RPxdU",
    "publicKey": "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEgyYqQmUAmDn9J7dR5xl-HlyAA0R2XV5sgQRnSGXbLt_xCrEdD1IVvvkyTmRD16y9p3C2O4PTZ0OF_ZYD2JgTVA==",
    "algorithm": "ES256"
  },
  "authenticatorData": "SZYN5YgOjGh0NBcPZHZgW4_krrmihjLHmVzzuoMdl2NFAAAAAAiYcFjK3EuBtuEw3lDcvpYAIN_duB4SXSTMv7L51KME_HqF6zjjujSz_EivOatkT8XVpQECAyYgASFYIIMmKkJlAJg5_Se3UecZfh5cgANEdl1ebIEEZ0hl2y7fIlgg8QqxHQ9SFb75Mk5kQ9esvadwtjuD02dDhf2WA9iYE1Q=",
  "clientData": "eyJ0eXBlIjoid2ViYXV0aG4uY3JlYXRlIiwiY2hhbGxlbmdlIjoiYTdjNjFlZjktZGMyMy00ODA2LWI0ODYtMjQyODkzOGE1NDdlIiwib3JpZ2luIjoiaHR0cDovL2xvY2FsaG9zdDo4MDgwIiwiY3Jvc3NPcmlnaW4iOmZhbHNlfQ=="
}

Then simply send this object as JSON to the server.

import { server } from '@passwordless-id/webauthn' 

const expected = {
    challenge: "a7c61ef9-dc23-4806-b486-2428938a547e", // whatever was randomly generated by the server
    origin: "http:https://localhost:8080",
}
const registrationParsed = await server.verifyRegistration(registration, expected)

Either this operation fails and throws an Error, or the verification is successful and returns the parsed registration. Example result:

{
  "username": "Arnaud",
  "credential": {
    "id": "3924HhJdJMy_svnUowT8eoXrOOO6NLP8SK85q2RPxdU",
    "publicKey": "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEgyYqQmUAmDn9J7dR5xl-HlyAA0R2XV5sgQRnSGXbLt_xCrEdD1IVvvkyTmRD16y9p3C2O4PTZ0OF_ZYD2JgTVA==",
    "algorithm": "ES256"
  },
  "client": {
    "type": "webauthn.create",
    "challenge": "a7c61ef9-dc23-4806-b486-2428938a547e",
    "origin": "http:https://localhost:8080",
    "crossOrigin": false
  },
  "authenticator": {
    "rpIdHash": "SZYN5YgOjGh0NBcPZHZgW4_krrmihjLHmVzzuoMdl2M=",
    "flags": {
      "userPresent": true,
      "userVerified": true,
      "backupEligibility": false,
      "backupState": false,
      "attestedData": true,
      "extensionsIncluded": false
    },
    "counter": 0,
    "aaguid": "08987058-cadc-4b81-b6e1-30de50dcbe96",
    "name": "Windows Hello Hardware Authenticator"
  },
  "attestation": null
}

NOTE: Currently, the attestation which proves the exact model type of the authenticator is not verified. Do I need attestation?

There are two kinds of authentications possible:

• by providing a list of allowed credential IDs
• by letting the platform offer a default UI to select the user and its credential

Both have their pros & cons (TODO: article).

The authentication procedure is similar to the procedure and divided in four steps.

1. Request a challenge and possibly a list of allowed credential IDs
2. Authenticate by

Example call:

import { client } from 'webauthn'

const authentication = await webauthn.authenticate(["3924HhJdJMy_svnUowT8eoXrOOO6NLP8SK85q2RPxdU"], "56535b13-5d93-4194-a282-f234c1c24500", {
  "authenticatorType": "auto",
  "userVerification": "required",
  "timeout": 60000
})

Example response:

{
  "credentialId": "3924HhJdJMy_svnUowT8eoXrOOO6NLP8SK85q2RPxdU",
  "authenticatorData": "SZYN5YgOjGh0NBcPZHZgW4_krrmihjLHmVzzuoMdl2MFAAAAAQ==",
  "clientData": "eyJ0eXBlIjoid2ViYXV0aG4uZ2V0IiwiY2hhbGxlbmdlIjoiNTY1MzViMTMtNWQ5My00MTk0LWEyODItZjIzNGMxYzI0NTAwIiwib3JpZ2luIjoiaHR0cDovL2xvY2FsaG9zdDo4MDgwIiwiY3Jvc3NPcmlnaW4iOmZhbHNlLCJvdGhlcl9rZXlzX2Nhbl9iZV9hZGRlZF9oZXJlIjoiZG8gbm90IGNvbXBhcmUgY2xpZW50RGF0YUpTT04gYWdhaW5zdCBhIHRlbXBsYXRlLiBTZWUgaHR0cHM6Ly9nb28uZ2wveWFiUGV4In0=",
  "signature": "MEUCIAqtFVRrn7q9HvJCAsOhE3oKJ-Hb4ISfjABu4lH70MKSAiEA666slmop_oCbmNZdc-QemTv2Rq4g_D7UvIhWT_vVp8M="
}

Parameters:

• credentialIds: The list of credential IDs that can be used for signing.
• challenge: A server-side randomly generated string, the base64url encoded version will be signed.
• options: See below.

import { server } from '@passwordless-id/webauthn' 

const credentialKey = { // obtained from database by looking up `authentication.credentialId`
    id: "3924HhJdJMy_svnUowT8eoXrOOO6NLP8SK85q2RPxdU",
    publicKey: "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEgyYqQmUAmDn9J7dR5xl-HlyAA0R2XV5sgQRnSGXbLt_xCrEdD1IVvvkyTmRD16y9p3C2O4PTZ0OF_ZYD2JgTVA==",
    algorithm: "ES256"
} as const

const expected = {
    challenge: "56535b13-5d93-4194-a282-f234c1c24500", // whatever was randomly generated by the server
    origin: "http:https://localhost:8080",
    userVerified: true, // should be set if `userVerification` was set to `required` in the authentication options (default)
    counter: 0 // for enhanced security, you can store the number of times this authenticator was used and ensure it increases each time
}

const authenticationParsed = await server.verifyAuthentication(authentication, credentialKey, expected)

Either this operation fails and throws an Error, or the verification is successful and returns the parsed registration. Example result:

{
  "credentialId": "3924HhJdJMy_svnUowT8eoXrOOO6NLP8SK85q2RPxdU",
  "client": {
    "type": "webauthn.get",
    "challenge": "56535b13-5d93-4194-a282-f234c1c24500",
    "origin": "http:https://localhost:8080",
    "crossOrigin": false,
    "other_keys_can_be_added_here": "do not compare clientDataJSON against a template. See https://goo.gl/yabPex"
  },
  "authenticator": {
    "rpIdHash": "SZYN5YgOjGh0NBcPZHZgW4_krrmihjLHmVzzuoMdl2M=",
    "flags": {
      "userPresent": true,
      "userVerified": true,
      "backupEligibility": false,
      "backupState": false,
      "attestedData": false,
      "extensionsIncluded": false
    },
    "counter": 1
  },
  "signature": "MEUCIAqtFVRrn7q9HvJCAsOhE3oKJ-Hb4ISfjABu4lH70MKSAiEA666slmop_oCbmNZdc-QemTv2Rq4g_D7UvIhWT_vVp8M="
}

Please note that the parsed result is returned for the sake of completeness. It is already verified, including the signature.

It should be truly random. Otherwise, your whole implementation might become vulnerable.

Unlike traditional authentication, you can have multiple public/private key pairs per user: one per device.

Only credentialId is provided during the authentication.

So either you maintain a mapping credentialId -> username in your database, or you add the username in your frontend to backend communication.

You can not specify any credential ids during authentication. In that case, the platform will pop-up a default dialog to let you pick a user and perform authentication. Of course, the look and feel is platform specific.

Unlike the webauthn protocol, some defaults are different:

• The timeout is one minute by default.
• If the device can act as authenticator itself, it is preferred instead of asking which authenticator type to use.
• The userVerification is required by default.
• The protocol "Relying Party ID" is always set to be the origin domain
• The username is used for both the protocol level user "name" and "displayName"

If you want to parse the encoded registration or authentication without verifying it, it is possible using the parsers module.

import { parsers } from 'webauthn'

// TODO

The following options are available for both register and authenticate.

• timeout: Number of milliseconds the user has to respond to the biometric/PIN check. (Default: 60000)
• userVerification: Whether to prompt for biometric/PIN check or not. (Default: "required")
• authenticatorType: Which device to use as authenticator. Possible values:
  • 'auto': if the local device can be used as authenticator it will be preferred. Otherwise it will prompt for an external device. (Default)
  • 'local': use the local device (using TouchID, FaceID, Windows Hello or PIN)
  • 'extern': use an external device (security key or connected phone)
  • 'both': prompt the user to choose between local or external device. The UI and user interaction in this case is platform specific.
• attestation: (Only for registration) If enabled, the device attestation and clientData will be provided as base64 encoded binary data. Note that this is not available on some platforms. (Default: false)
• debug: If enabled, parses the "data" objects and provide it in a "debug" properties.

clientData

webauthn.parseAuthenticator('eyJ0eXBlIjoid2...')

{
  "type": "webauthn.create",
  "challenge": "MzIwZDAzMzQtNDhjNy00N2NhLTgzNjktOTM5NDc0Yzg1Zjdi",
  "origin": "http:https://localhost:8080",
  "crossOrigin": false
}

authenticatorData

webauthn.parseAuthenticator('SZYN5YgOjGh0NB...')

{
  "rpIdHash": "SZYN5YgOjGh0NBcPZHZgW4_krrmihjLHmVzzuoMdl2M=",
  "flags": {
    "userPresent": true,
    "userVerified": true,
    "backupEligibility": false,
    "backupState": false,
    "attestedData": true,
    "extensionsIncluded": false
  },
  "counter": 0,
  "aaguid": "08987058-cadc-4b81-b6e1-30de50dcbe96",
  "name": "Windows Hello Hardware Authenticator"
}

Please note that aaguid and name are only available during registration.