Complete a WebAuthn Passkey Assertion

This API is used to validate a WebAuthn authentication ceremony by providing the values returned from the WebAuthn JavaScript API call, but it does not authenticate the user. This API can be used to confirm that a user has access to a particular passkey without authenticating them.

Request#

Assert a WebAuthn Authentication Ceremony

POST/api/webauthn/assert

OpenAPI Spec

Request Headers#

X-FusionAuth-TenantIdStringoptional

The unique Id of the tenant used to scope this API request.

The tenant Id is not required on this request even when more than one tenant has been configured because the tenant can be identified based upon the request parameters or it is otherwise not required.

Specify a tenant Id on this request when you want to ensure the request is scoped to a specific tenant. The tenant Id may be provided through this header or by using a tenant locked API key to achieve the same result.

See Making an API request using a Tenant Id for additional information.

Request Body#

The credential in the request body contains data returned by the WebAuthn JavaScript API call. The credential.response.authenticatorData, credential.response.clientDataJSON, credential.response.signature, and credential.response.userHandle fields must be converted to base64url-encoded strings for the FusionAuth API request. See WebAuthn JavaScript API Binary Format for details.

credential.clientExtensionResultsObjectoptional

The results for WebAuthn extensions requested during authentication. FusionAuth does not currently support any WebAuthn authentication extensions.

credential.idStringrequired

A base64url-encoded version of the credential Id used by the authenticator for this ceremony.

credential.rpIdStringoptional

If the tenant configuration overrides the Relying Party Id, this parameter should match tenant.webAuthnConfiguration.relyingPartyId, otherwise the value should be omitted from the request object.

credential.response.authenticatorDataStringrequired

The base64url-encoded authenticator data from the WebAuthn JavaScript API response, which includes information on the passkey used to complete the ceremony and other data important for validation. See Converting ArrayBuffer to base64url-encoded String for details on converting this value for the FusionAuth API request.

credential.response.clientDataJSONStringrequired

The base64url-encoded client data from the WebAuthn JavaScript API response. This contains important information for the WebAuthn authentication validation process, including the one-time challenge generated when the registration ceremony began. See Converting ArrayBuffer to base64url-encoded String for details on converting this value for the FusionAuth API request.

credential.response.signatureStringrequired

The base64url-encoded signature from the WebAuthn JavaScript API response. The authenticator generates the signature using the selected passkey's private key by signing over the binary concatenation of credential.response.authenticatorData and the SHA-256 hash of credential.response.clientDataJSON before they are converted to base64url-encoded strings. See Converting ArrayBuffer to base64url-encoded String for details on converting this value for the FusionAuth API request.

credential.response.userHandleStringoptional

The base64url-encoded user handle from the WebAuthn JavaScript API response. This field is only required when the user was not identified prior to the authentication ceremony through the use of a client-side discoverable passkey. See Converting ArrayBuffer to base64url-encoded String for details on converting this value for the FusionAuth API request.

credential.typeStringrequired

The credential type of the passkey. The only value supported by WebAuthn is public-key.

originStringrequired

The browser request origin during the authentication ceremony. For example, example.com.

rpIdStringrequired

If the tenant configuration overrides the Relying Party Id, this parameter should match tenant.webAuthnConfiguration.relyingPartyId, otherwise the value should be the browser request origin's effective domain during the ceremony.

twoFactorTrustIdStringoptional

The Multi-Factor Trust identifier returned by the Multi-Factor Login API response. This value may be provided to bypass the Multi-Factor challenge when a User has Multi-Factor enabled.

Example Request JSON

{
  "credential": {
    "id": "HdN9wqP9mqOonacmiM2gIjASFYg",
    "response": {
      "authenticatorData": "mPsv4VW-wth0V9gzsxWRFn-1SyC9gM4-QC4ptMFDNhUFAAAAKQ==",
      "clientDataJSON": "eyJjaGFsbGVuZ2UiOiJTeTYzQldla285blFsYzVOQmVWcE1BWjFtQ0hvdzBXUXVFeDRJU2xuQzR3IiwiY3Jvc3NPcmlnaW4iOmZhbHNlLCJvcmlnaW4iOiJodHRwczovL2Z1c2lvbmF1dGguaW8iLCJ0eXBlIjoid2ViYXV0aG4uZ2V0In0=",
      "signature": "MEUCIQDUwlDp9aNcYQmvpVGLJ35H8lRWjWsfjVsfPf_5HhY3GwIgahBhISBxv82ZS4ll8TZiJp5bIN2CGx_-VjUymfzKqGA=",
      "userHandle": "NzAzZmUyZDItMmQzOS00Y2I3LWI3NmQtMGI5OTE4ZWQyNDU3"
    },
    "type": "public-key"
  },
  "origin": "https://auth.piedpiper.com",
  "rpId": "piedpiper.com"
}

Response#

The response for this API contains the WebAuthn passkey used to complete the assertion.

Response Codes

Code	Description
200	The request was successful. The response will contain a JSON body.
400	The request was invalid and/or malformed. The response will contain an Errors JSON Object with the specific errors. This status will also be returned if a paid FusionAuth license is required and is not present.
500	There was an internal error. A stack trace is provided and logged in the FusionAuth log files. The response will be empty.
503	The search index is not available or encountered an exception so the request cannot be completed. The response will contain a JSON body.

Response Body#

credential.algorithmLong

The identifier for the signing algorithm used with the passkey. These values are defined by the IANA COSE Algorithms registry. FusionAuth supports a subset of these algorithms.

Supported algorithms

Name	Value	Description
RS256	-257	RSASSA-PKCS1-v1_5 using SHA-256
RS384	-258	RSASSA-PKCS1-v1_5 using SHA-384
RS512	-259	RSASSA-PKCS1-v1_5 using SHA-512
PS256	-37	RSASSA-PSS w/ SHA-256
PS384	-38	RSASSA-PSS w/ SHA-384
PS512	-39	RSASSA-PSS w/ SHA-512
ES256	-7	ECDSA w/ SHA-256
ES384	-35	ECDSA w/ SHA-384
ES512	-36	ECDSA w/ SHA-512

credential.attestationTypeString

The type of attestation provided when the passkey was registered. Passkeys registered in FusionAuth will have a value of none. Imported passkeys may have another value.

credential.authenticatorSupportsUserVerificationBoolean

Indicates whether this authenticator supports user verification. User verification ensures that the user is authorized to use the authenticator.

This value is currently determined by whether user verification occurred during the registration of this passkey rather than by other means, such as examining FIDO authenticator metadata.

credential.credentialIdString

The credential Id generated by the authenticator is stored as a base64url-encoded string. This value is used by authenticators to look up a passkey during an authentication ceremony and to prevent multiple passkeys from being registered on the same authenticator for a single user.

credential.dataObject

An object that can hold any information about the passkey that should be persisted.

credential.discoverableBoolean

Indicates whether the passkey is "client-side discoverable." Discoverable passkeys can be used in authentication ceremonies without first identifying the user (e.g. by requiring the user to complete a form field).

credential.displayNameString

The display name for the passkey selected during registration. This value should have been selected by the user.

credential.idUUID

The unique identifier for this passkey.

credential.insertInstantLong

The instant that the passkey was added to the FusionAuth database.

credential.lastUseInstantLong

The instant that the passkey was last used to complete a WebAuthn ceremony.

credential.nameString

A unique name meant to disambiguate passkeys with the same credential.displayName.

credential.publicKeyString

The passkey's public key, encoded in PEM format.

credential.relyingPartyIdString

The Relying Party Id used at the time the passkey was registered.

credential.signCountInteger

A signature counter for the passkey. The signature count can be used by a Relying Party to identify a cloned or malfunctioning authenticator.

credential.tenantIdUUID

The Id of the tenant to which this passkey belongs.

credential.transportsArray<String>

A list of transport types supported by the authenticator that generated the passkey. This value is used as a hint to help identify eligible authenticators during a WebAuthn ceremony.

FusionAuth treats the list of transports as strings to maximize authenticator compatibility. These values are used as hints during WebAuthn ceremonies and missing, extra, or unexpected values should not cause a ceremony to fail. Some common values are:

internal - the authenticator is integrated with the client device
usb - the authenticator can be contacted over USB
nfc - the authenticator can be contacted over Near Field Communication (NFC)
ble - the authenticator can be contacted over Bluetooth Smart (Bluetooth Low Energy, or BLE)
cable - "cloud-assisted" BLE. This transport is used for Android devices acting as an authenticator connected to the computer over Bluetooth
hybrid - replacement for the cable transport

credential.userAgentString

The user agent at the time the passkey was registered. This can be useful for troubleshooting purposes.

credential.userIdUUID

The Id of the user that this passkey belongs to.

Example Response JSON

{
  "credential": {
    "algorithm": -7,
    "attestationType": "none",
    "authenticatorSupportsUserVerification": true,
    "credentialId": "HdN9wqP9mqOonacmiM2gIjASFYg",
    "data": {},
    "displayName": "Chrome Touch ID",
    "name": "richard@fusionauth.io",
    "id": "c664318a-2384-4c35-9475-9a200e1d3b72",
    "insertInstant": 1668011701792,
    "discoverable": false,
    "lastUseInstant": 1668021630599,
    "publicKey": "-----BEGIN PUBLIC KEY-----\nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEz9DI9AQfZn1aDJG5sw3Ckl7SoQ7E\nLPElDoJMijphvVigTcNMTc8H9Xptl8B20QHMOXGTzaUxLGNY1c8yhw9VVA==\n-----END PUBLIC KEY-----",
    "relyingPartyId": "piedpiper.com",
    "signCount": 41,
    "tenantId": "30663132-6464-6665-3032-326466613934",
    "transports": [
      "internal"
    ],
    "userId": "703fe2d2-2d39-4cb7-b76d-0b9918ed2457"
  }
}