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@simplewebauthn/server

Installation​

Node LTS 20.x or higher​

This package is available on npm:

npm install @simplewebauthn/server

It can then be imported into all types of Node applications thanks to its support for both CommonJS and ECMAScript modules (ESM) projects:

// CommonJS (NodeJS)
const SimpleWebAuthnServer = require('@simplewebauthn/server');

// ES Module (NodeJS w/module support, TypeScript, Babel, etc...)
import SimpleWebAuthnServer from '@simplewebauthn/server';

Deno v1.33.x or higher​

This package is also available for installation in Deno projects from deno.land/x:

import {...} from 'https://deno.land/x/simplewebauthn/deno/server.ts';

Additional data structures​

Documentation below will refer to the following TypeScript types. These are intended to be inspirational, a simple means of communicating the shape of the values you'll need to be capable of persisting in your database:

import type {
  AuthenticatorTransportFuture,
  CredentialDeviceType,
  Base64URLString,
} from '@simplewebauthn/types';

type UserModel = {
  id: any;
  username: string;
};

/**
 * It is strongly advised that credentials get their own DB
 * table, ideally with a foreign key somewhere connecting it
 * to a specific UserModel.
 *
 * "SQL" tags below are suggestions for column data types and
 * how best to store data received during registration for use
 * in subsequent authentications.
 */
type Passkey = {
  // SQL: Store as `TEXT`. Index this column
  id: Base64URLString;
  // SQL: Store raw bytes as `BYTEA`/`BLOB`/etc...
  publicKey: Uint8Array;
  // SQL: Foreign Key to an instance of your internal user model
  user: UserModel;
  // SQL: Store as `TEXT`. Index this column. A UNIQUE constraint on (webAuthnUserID + user) also
  // achieves maximum user privacy
  webauthnUserID: Base64URLString;
  // SQL: Consider `BIGINT` since some authenticators return atomic timestamps as counters
  counter: number;
  // SQL: `VARCHAR(32)` or similar, longest possible value is currently 12 characters
  // Ex: 'singleDevice' | 'multiDevice'
  deviceType: CredentialDeviceType;
  // SQL: `BOOL` or whatever similar type is supported
  backedUp: boolean;
  // SQL: `VARCHAR(255)` and store string array as a CSV string
  // Ex: ['ble' | 'cable' | 'hybrid' | 'internal' | 'nfc' | 'smart-card' | 'usb']
  transports?: AuthenticatorTransportFuture[];
};

Below is a sample database schema showing how a passkeys table can track WebAuthn-specific user IDs while still allowing use of typical internal database user IDs through the rest of the site (click here for an interactive version of the schema):

FIDO2 Metadata download button

Keep this table structure in mind as you proceed through the following sections.

Identifying your RP​

Start by defining some constants that describe your "Relying Party" (RP) server to authenticators:

// Human-readable title for your website
const rpName = 'SimpleWebAuthn Example';
// A unique identifier for your website
const rpID = 'simplewebauthn.dev';
// The URL at which registrations and authentications should occur
const origin = `https://${rpID}`;

These will be referenced throughout registrations and authentications to ensure that authenticators generate and return credentials specifically for your server.

Registration​

"Registration" is analogous to new account creation. Registration uses the following exported methods from this package:

import {
  generateRegistrationOptions,
  verifyRegistrationResponse,
} from '@simplewebauthn/server';

Registration occurs in two steps:

  1. Generate registration options for the browser to pass to a supported authenticator
  2. Verify the authenticator's response

Each of these steps need their own API endpoints:

1. Generate registration options​

One endpoint (GET) needs to return the result of a call to generateRegistrationOptions():

// (Pseudocode) Retrieve the user from the database
// after they've logged in
const user: UserModel = getUserFromDB(loggedInUserId);
// (Pseudocode) Retrieve any of the user's previously-
// registered authenticators
const userPasskeys: Passkey[] = getUserPasskeys(user);

const options: PublicKeyCredentialCreationOptionsJSON = await generateRegistrationOptions({
  rpName,
  rpID,
  userName: user.username,
  // Don't prompt users for additional information about the authenticator
  // (Recommended for smoother UX)
  attestationType: 'none',
  // Prevent users from re-registering existing authenticators
  excludeCredentials: userPasskeys.map(passkey => ({
    id: passkey.id,
    // Optional
    transports: passkey.transports,
  })),
  // See "Guiding use of authenticators via authenticatorSelection" below
  authenticatorSelection: {
    // Defaults
    residentKey: 'preferred',
    userVerification: 'preferred',
    // Optional
    authenticatorAttachment: 'platform',
  },
});

// (Pseudocode) Remember these options for the user
setCurrentRegistrationOptions(user, options);

return options;

These options can be passed directly into @simplewebauthn/browser's startRegistration() method.

Guiding use of authenticators via authenticatorSelection

generateRegistrationOptions() also accepts an authenticatorSelection option that can be used to fine-tune the registration experience. When unspecified, defaults are provided according to passkeys best practices. These values can be overridden based on Relying Party needs, however:

residentKey - one of:​

  • 'discouraged'
    • Won't consume discoverable credential slots on security keys, but also won't generate synced passkeys on Android devices.
  • 'preferred'
    • Will always generate synced passkeys on Android devices, but will consume discoverable credential slots on security keys.
  • 'required'
    • Same as 'preferred'

userVerification - one of:​

  • 'discouraged'
    • Won't perform user verification if interacting with an authenticator won't automatically perform it (i.e. security keys won't prompt for PIN, but interacting with Touch ID on a macOS device will always perform user verification.) User verification will usually be false.
  • 'preferred'
    • Will perform user verification when possible, but will skip any prompts for PIN or local login password when possible. In these instances user verification can sometimes be false.
  • 'required'
    • Will always provides multi-factor authentication, at the expense of always requiring some users to enter their local login password during auth. User verification should never be false.

authenticatorAttachment - one of:​

  • 'cross-platform'
    • Browsers will guide users towards registering a security key, or mobile device via hybrid registration.
  • 'platform'
    • Browser will guide users to registering the locally integrated hardware authenticator.

1a. Supported Attestation Formats​

If attestationType is set to "direct" when generating registration options, the authenticator will return a more complex response containing an "attestation statement". This statement includes additional verifiable information about the authenticator.

Attestation statements are returned in one of several different formats. SimpleWebAuthn supports all current WebAuthn attestation formats, including:

  • Packed
  • TPM
  • Android Key
  • Android SafetyNet
  • Apple
  • FIDO U2F
  • None
info

Attestation statements are an advanced aspect of WebAuthn. You can ignore this concept if you're not particular about the kinds of authenticators your users can use for registration and authentication.

2. Verify registration response​

The second endpoint (POST) should accept the value returned by @simplewebauthn/browser's startRegistration() method and then verify it:

const { body } = req;

// (Pseudocode) Retrieve the logged-in user
const user: UserModel = getUserFromDB(loggedInUserId);
// (Pseudocode) Get `options.challenge` that was saved above
const currentOptions: PublicKeyCredentialCreationOptionsJSON =
  getCurrentRegistrationOptions(user);

let verification;
try {
  verification = await verifyRegistrationResponse({
    response: body,
    expectedChallenge: currentOptions.challenge,
    expectedOrigin: origin,
    expectedRPID: rpID,
  });
} catch (error) {
  console.error(error);
  return res.status(400).send({ error: error.message });
}

const { verified } = verification;
Support for multiple origins and RP IDs

SimpleWebAuthn optionally supports verifying registrations from multiple origins and RP IDs! Simply pass in an array of possible origins and IDs for expectedOrigin and expectedRPID respectively.

When finished, it's a good idea to return the verification status to the browser to display appropriate UI:

return { verified };

3. Post-registration responsibilities​

Assuming verification.verified is true then RP's must, at the very least, save the credential data in registrationInfo to the database:

const { registrationInfo } = verification;
const {
  credentialID,
  credentialPublicKey,
  counter,
  credentialDeviceType,
  credentialBackedUp,
} = registrationInfo;

const newPasskey: Passkey = {
  // `user` here is from Step 2
  user,
  // Created by `generateRegistrationOptions()` in Step 1
  webAuthnUserID: currentOptions.user.id,
  // A unique identifier for the credential
  id: credentialID,
  // The public key bytes, used for subsequent authentication signature verification
  publicKey: credentialPublicKey,
  // The number of times the authenticator has been used on this site so far
  counter,
  // Whether the passkey is single-device or multi-device
  deviceType: credentialDeviceType,
  // Whether the passkey has been backed up in some way
  backedUp: credentialBackedUp,
  // `body` here is from Step 2
  transports: body.response.transports,
};

// (Pseudocode) Save the authenticator info so that we can
// get it by user ID later
saveNewPasskeyInDB(newPasskey);
Regarding counter

Tracking the "signature counter" allows Relying Parties to potentially identify misbehaving authenticators, or cloned authenticators. The counter on subsequent authentications should only ever increment; if your stored counter is greater than zero, and a subsequent authentication response's counter is the same or lower, then perhaps the authenticator just used to authenticate is in a compromised state.

It's also not unexpected for certain high profile authenticators, like Touch ID on macOS, to always return 0 (zero) for the signature counter. In this case there is nothing an RP can really do to detect a cloned authenticator, especially in the context of multi-device credentials.

@simplewebauthn/server knows how to properly check the signature counter on subsequent authentications. RP's should only need to remember to store the value after registration, and then feed it back into startAuthentication() when the user attempts a subsequent login. RP's should remember to update the credential's counter value in the database afterwards. See Post-authentication responsibilities below for how to do so.

Authentication​

"Authentication" is analogous to existing account login. Authentication uses the following exported methods from this package:

import {
  generateAuthenticationOptions,
  verifyAuthenticationResponse,
} from '@simplewebauthn/server';

Just like registration, authentication span two steps:

  1. Generate authentication options for the browser to pass to a FIDO2 authenticator
  2. Verify the authenticator's response

Each of these steps need their own API endpoints:

1. Generate authentication options​

One endpoint (GET) needs to return the result of a call to generateAuthenticationOptions():

// (Pseudocode) Retrieve the logged-in user
const user: UserModel = getUserFromDB(loggedInUserId);
// (Pseudocode) Retrieve any of the user's previously-
// registered authenticators
const userPasskeys: Passkey[] = getUserPasskeys(user);

const options: PublicKeyCredentialRequestOptionsJSON = await generateAuthenticationOptions({
  rpID,
  // Require users to use a previously-registered authenticator
  allowCredentials: userPasskeys.map(passkey => ({
    id: passkey.id,
    transports: passkey.transports,
  })),
});

// (Pseudocode) Remember this challenge for this user
setCurrentAuthenticationOptions(user, options);

return options;

These options can be passed directly into @simplewebauthn/browser's startAuthentication() method.

Support for custom challenges

Power users can optionally generate and pass in their own unique challenges as challenge when calling generateAuthenticationOptions(). In this scenario options.challenge still needs to be saved to be used in verification as described below.

2. Verify authentication response​

The second endpoint (POST) should accept the value returned by @simplewebauthn/browser's startAuthentication() method and then verify it:

const { body } = req;

// (Pseudocode) Retrieve the logged-in user
const user: UserModel = getUserFromDB(loggedInUserId);
// (Pseudocode) Get `options.challenge` that was saved above
const currentOptions: PublicKeyCredentialRequestOptionsJSON =
  getCurrentAuthenticationOptions(user);
// (Pseudocode} Retrieve a passkey from the DB that
// should match the `id` in the returned credential
const passkey: AuthenticatorDevice = getUserPasskey(user, body.id);

if (!passkey) {
  throw new Error(`Could not find passkey ${body.id} for user ${user.id}`);
}

let verification;
try {
  verification = await verifyAuthenticationResponse({
    response: body,
    expectedChallenge: currentOptions.challenge,
    expectedOrigin: origin,
    expectedRPID: rpID,
    authenticator: passkey,
  });
} catch (error) {
  console.error(error);
  return res.status(400).send({ error: error.message });
}

const { verified } = verification;

When finished, it's a good idea to return the verification status to the browser to display appropriate UI:

return { verified };
Support for multiple origins and RP IDs

SimpleWebAuthn optionally supports verifying authentications from multiple origins and RP IDs! Simply pass in an array of possible origins and IDs for expectedOrigin and expectedRPID respectively.

3. Post-authentication responsibilities​

Assuming verification.verified is true, then update the user's authenticator's counter property in the DB:

const { authenticationInfo } = verification;
const { newCounter } = authenticationInfo;

saveUpdatedCounter(passkey, newCounter);

Troubleshooting​

Below are errors you may see while using this library, and potential solutions to them:

DOMException [NotSupportedError]: Unrecognized name.​

Authentication responses may unexpectedly error out during verification. This appears as the throwing of an "Unrecognized name" error from a call to verifyAuthenticationResponse() with the following stack trace:

DOMException [NotSupportedError]: Unrecognized name.
    at new DOMException (node:internal/per_context/domexception:70:5)
    at __node_internal_ (node:internal/util:477:10)
    at normalizeAlgorithm (node:internal/crypto/util:220:15)
    at SubtleCrypto.importKey (node:internal/crypto/webcrypto:503:15)
    at importKey (/Users/swan/Developer/simplewebauthn/packages/server/src/helpers/iso/isoCrypto/importKey.ts:9:27)
    at verifyOKP (/Users/swan/Developer/simplewebauthn/packages/server/src/helpers/iso/isoCrypto/verifyOKP.ts:57:30)
    at Object.verify (/Users/swan/Developer/simplewebauthn/packages/server/src/helpers/iso/isoCrypto/verify.ts:31:21)
    at verifySignature (/Users/swan/Developer/simplewebauthn/packages/server/src/helpers/verifySignature.ts:34:20)
    at verifyAuthenticationResponse (/Users/swan/Developer/simplewebauthn/packages/server/src/authentication/verifyAuthenticationResponse.ts:206:36)
    at async /Users/swan/Developer/simplewebauthn/packages/server/345.ts:26:24

This appears to be an issue with some environments running versions of Node prior to v18 LTS.

To fix this, update your call to generateRegistrationOptions() to exclude -8 (Ed25519) from the list of algorithms:

const options = await generateRegistrationOptions({
  // ...
  supportedAlgorithmIDs: [-7, -257],
});

You will then need to re-register any authenticators that generated credentials that cause this error.

Error: Signature verification with public key of kty OKP is not supported by this method​

Authentication responses may unexpectedly error out during verification. This appears as the throwing of a "Signature verification with public key of kty OKP is not supported" error from a call to verifyAuthenticationResponse() with the following stack trace:

Error: Signature verification with public key of kty OKP is not supported by this method
    at Object.verify (/xxx/node_modules/@simplewebauthn/server/script/helpers/iso/isoCrypto/verify.js:30:11)
    at verifySignature (/xxx/node_modules/@simplewebauthn/server/script/helpers/verifySignature.js:25:76)
    at verifyAuthenticationResponse (/xxx/node_modules/@simplewebauthn/server/script/authentication/verifyAuthenticationResponse.js:162:66)

This is caused by security key responses in Firefox 118 and earlier being incorrectly composed by the browser when the security key uses Ed25519 for its credential keypair.

To fix this, update your call to generateRegistrationOptions() to exclude -8 (Ed25519) from the list of algorithms:

const options = await generateRegistrationOptions({
  // ...
  supportedAlgorithmIDs: [-7, -257],
});

You will then need to re-register any authenticators that generated credentials that cause this error.

ERROR extractStrings is not a function​

Registration responses may unexpectedly error out during verification. This appears as the throwing of an "extractStrings is not a function" error from a call to verifyRegistrationResponse() with the following stack trace:

ERROR  extractStrings is not a function
    at readString (/node_modules/.pnpm/[email protected]/node_modules/cbor-x/dist/node.cjs:520:1)
    at read (/node_modules/.pnpm/[email protected]/node_modules/cbor-x/dist/node.cjs:343:1)
    at read (/node_modules/.pnpm/[email protected]/node_modules/cbor-x/dist/node.cjs:363:1)
    at checkedRead (/node_modules/.pnpm/[email protected]/node_modules/cbor-x/dist/node.cjs:202:1)
    at Encoder.decode (/node_modules/.pnpm/[email protected]/node_modules/cbor-x/dist/node.cjs:153:1)
    at Encoder.decodeMultiple (/node_modules/.pnpm/[email protected]/node_modules/cbor-x/dist/node.cjs:170:1)
    at Object.decodeFirst (/node_modules/.pnpm/@[email protected]/node_modules/@simplewebauthn/server/script/helpers/iso/isoCBOR.js:30:1)
    at decodeAttestationObject (/node_modules/.pnpm/@[email protected]/node_modules/@simplewebauthn/server/script/helpers/decodeAttestationObject.js:12:1)
    at verifyRegistrationResponse (/node_modules/.pnpm/@[email protected]/node_modules/@simplewebauthn/server/script/registration/verifyRegistrationResponse.js:100:1)
    at AuthnService.verifyRegistrationResponse (/home/deploy/mx/modules/authn/authn.service.js:89:1)

This is caused by the @vercel/ncc dependency not supporting runtime use of require() within other third-party packages used by the project, like @simplewebauthn/server's use of cbor-x.

To fix this, add CBOR_NATIVE_ACCELERATION_DISABLED=true in your project's env file to disable the use of require() in cbor-x.

Alternatively, the following can be added to your project to inject this value into your project's runtime environment:

function nodeEnvInjection() {
  /**
   * `@vercel/ncc` does not support the use of `require()` so disable its
   * use in the `@simplewebauthn/server` dependency called `cbor-x`.
   *
   * https://github.com/kriszyp/cbor-x/blob/master/node-index.js#L10
   */
  process.env['CBOR_NATIVE_ACCELERATION_DISABLED'] = 'true';
}

// Call this at the start of the project, before any imports
nodeEnvInjection()

Error: String values for `userID` are no longer supported​

See Advanced Guides > @simplewebauthn/server > Custom User IDs for more information.