Secure context
This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The authenticatorData
property of the AuthenticatorAssertionResponse
interface returns an ArrayBuffer
containing information from the authenticator such as the Relying Party ID Hash (rpIdHash), a signature counter, test of user presence, user verification flags, and any extensions processed by the authenticator.
Syntax
var authnrData = authenticatorAssertionResponse.authenticatorData;
Value
An ArrayBuffer
that has a ArrayBuffer.byteLength
of at least 37 bytes, containing the following fields:
- rpIdHash (32 bytes) - A SHA256 hash of the relying party ID that was seen by the browser. The server will ensure that this hash matches a hash of its own origin in order to prevent phishing or other man-in-the-middle attacks.
- flags (1 bytes) - A bitfield that indicates various attributes that were asserted by the authenticator. The bits are as follows, where "bit 0" is the least significant bit and all bits not specifically mentioned below are "reserved for future use":
- Bit 0, User Presence (UP) - If set, authenticator validated that the user was present through some Test of User Presence (TUP), such as touching a button on the authenticator.
- Bit 2, User Verification (UV) - If set, authenticator verified the actual user, through a biometric, PIN, or other authentication method.
- Bit 6, Attested Credential Data (AT) - If set, attestedCredentialData will immediately follow the first 37 bytes of this authenticatorData.
- Bit 7, Extension data (ED) - If set, extension data is present. Extension data will follow attestedCredentialData if it is present, or will immediatelly follow the first 37 bytes of the authenticatorData if no attestedCredentialData is present.
- signCount (4 bytes) - A signature count from the authenticator. The server will use this counter to detect authenticator cloning.
- attestedCredentialData (variable length) - The credential that was created. This is only present during a navigator.credentials.create() call. This is a sequence of bytes with the following format:
- AAGUID (16 bytes) - Authenticator Attestation Globally Unique Identifier, a unique number that identifies the model of the authenticator (not the specific instance of the authenticator) so that a relying party can understand the characteristics of the authenticator by looking up its metadata statement.
- credentialIdLength (2 bytes) - The length of the credential ID that immediately follows these bytes.
- credentialId (variable length) - A unique identifier for this credential so that it can be requested for future authentications. The credential is "credentialIdLength" bytes long.
- credentialPublicKey (variable length) - A COSE encoded public key. This public key will be stored on the server associated with a user's account and be used for future authentications.
- extensions (variable length) - An optional CBOR map of extensions.
Examples
var options = { challenge: new Uint8Array(26), // will be another value, provided by the relying party server timeout: 60000 }; navigator.credentials.get({ publickey: options }) .then(function (assertionPKCred) { var authenticatorData = assertionPKCred.response.authenticatorData; // Maybe try to convert the authenticatorData to see what's inside // Send response and client extensions to the server so that it can // go on with the authentication }).catch(function (err) { console.error(err); });
Specifications
Specification | Status | Comment |
---|---|---|
Web Authentication: An API for accessing Public Key Credentials Level 1 The definition of 'authenticatorData' in that specification. |
Recommendation | Initial definition. |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
authenticatorData | Chrome
Full support
67
| Edge Full support 18 | Firefox
Full support
60
| IE No support No | Opera No support No | Safari Full support 13 | WebView Android Full support 70 | Chrome Android Full support 70 | Firefox Android
Full support
60
| Opera Android No support No | Safari iOS Full support 13.3 | Samsung Internet Android No support No |
Legend
- Full support
- Full support
- No support
- No support
- See implementation notes.
- See implementation notes.
- User must explicitly enable this feature.
- User must explicitly enable this feature.