ox/_esm/webauthn/Authenticator.js

Ethereum Standard Library

import * as Base64 from '../core/Base64.js';
import * as Bytes from '../core/Bytes.js';
import * as Cbor from '../core/Cbor.js';
import * as CoseKey from '../core/CoseKey.js';
import * as Hash from '../core/Hash.js';
import * as Hex from '../core/Hex.js';
/**
 * Gets the authenticator data which contains information about the
 * processing of an authenticator request (ie. from `Authentication.sign`).
 *
 * :::warning
 *
 * This function is mainly for testing purposes or for manually constructing
 * autenticator data. In most cases you will not need this function.
 * `authenticatorData` is typically returned as part of the
 * authenticator response.
 *
 * :::
 *
 * @example
 * ```ts twoslash
 * import { Authenticator } from 'ox/webauthn'
 *
 * const authenticatorData = Authenticator.getAuthenticatorData({
 *   rpId: 'example.com',
 *   signCount: 420,
 * })
 * // @log: "0xa379a6f6eeafb9a55e378c118034e2751e682fab9f2d30ab13d2125586ce194705000001a4"
 * ```
 *
 * @example
 * ### With Attested Credential Data
 *
 * Include a credential ID and public key in the authenticator data (for registration responses):
 *
 * ```ts twoslash
 * import { P256 } from 'ox'
 * import { Authenticator } from 'ox/webauthn'
 *
 * const { publicKey } = P256.createKeyPair()
 *
 * const authenticatorData = Authenticator.getAuthenticatorData({
 *   rpId: 'example.com',
 *   flag: 0x41, // UP + AT
 *   credential: {
 *     id: new Uint8Array(32),
 *     publicKey,
 *   },
 * })
 * ```
 *
 * @param options - Options to construct the authenticator data.
 * @returns The authenticator data.
 */
export function getAuthenticatorData(options = {}) {
    const { credential, flag = 5, rpId = window.location.hostname, signCount = 0, } = options;
    const rpIdHash = Hash.sha256(Hex.fromString(rpId));
    const flag_bytes = Hex.fromNumber(flag, { size: 1 });
    const signCount_bytes = Hex.fromNumber(signCount, { size: 4 });
    const base = Hex.concat(rpIdHash, flag_bytes, signCount_bytes);
    if (!credential)
        return base;
    // AAGUID (16 bytes of zeros)
    const aaguid = Hex.fromBytes(new Uint8Array(16));
    // Credential ID
    const credentialId = Hex.fromBytes(credential.id);
    const credIdLen = Hex.fromNumber(credential.id.length, { size: 2 });
    // COSE public key
    const coseKey = CoseKey.fromPublicKey(credential.publicKey);
    return Hex.concat(base, aaguid, credIdLen, credentialId, coseKey);
}
/**
 * Extracts the signature counter from the authenticator data.
 * The counter is a 4-byte big-endian unsigned integer at bytes 33–36.
 *
 * Useful for detecting cloned authenticators: if the counter is non-zero and
 * does not monotonically increase between assertions, it may indicate a cloned key.
 *
 * @example
 * ```ts twoslash
 * import { Authenticator } from 'ox/webauthn'
 *
 * const signCount = Authenticator.getSignCount(
 *   '0x49960de5880e8c687434170f6476605b8fe4aeb9a28632c7995cf3ba831d97630500000001',
 * )
 * // @log: 1
 * ```
 *
 * @param authenticatorData - The authenticator data hex string.
 * @returns The signature counter.
 */
export function getSignCount(authenticatorData) {
    const bytes = Bytes.fromHex(authenticatorData);
    if (bytes.length < 37)
        return 0;
    return (((bytes[33] << 24) |
        (bytes[34] << 16) |
        (bytes[35] << 8) |
        bytes[36]) >>>
        0);
}
/**
 * Constructs the Client Data in stringified JSON format which represents client data that
 * was passed to `credentials.get()` or `credentials.create()`.
 *
 * :::warning
 *
 * This function is mainly for testing purposes or for manually constructing
 * client data. In most cases you will not need this function.
 * `clientDataJSON` is typically returned as part of the authenticator response.
 *
 * :::
 *
 * @example
 * ```ts twoslash
 * import { Authenticator } from 'ox/webauthn'
 *
 * const clientDataJSON = Authenticator.getClientDataJSON({
 *   challenge: '0xdeadbeef',
 *   origin: 'https://example.com',
 * })
 * // @log: "{"type":"webauthn.get","challenge":"3q2-7w","origin":"https://example.com","crossOrigin":false}"
 * ```
 *
 * @param options - Options to construct the client data.
 * @returns The client data.
 */
export function getClientDataJSON(options) {
    const { challenge, crossOrigin = false, extraClientData, origin = window.location.origin, type = 'webauthn.get', } = options;
    return JSON.stringify({
        type,
        challenge: Base64.fromHex(challenge, { url: true, pad: false }),
        origin,
        crossOrigin,
        ...extraClientData,
    });
}
/**
 * Constructs a CBOR-encoded attestation object for testing WebAuthn registration
 * verification. Combines the authenticator data with an attestation statement.
 *
 * :::warning
 *
 * This function is mainly for testing purposes. In production, the attestation
 * object is returned by the authenticator during `navigator.credentials.create()`.
 *
 * :::
 *
 * @example
 * ```ts twoslash
 * import { P256 } from 'ox'
 * import { Authenticator } from 'ox/webauthn'
 *
 * const { publicKey } = P256.createKeyPair()
 *
 * const attestationObject = Authenticator.getAttestationObject({
 *   authData: Authenticator.getAuthenticatorData({
 *     rpId: 'example.com',
 *     flag: 0x41,
 *     credential: { id: new Uint8Array(32), publicKey },
 *   }),
 * })
 * ```
 *
 * @param options - Options to construct the attestation object.
 * @returns The CBOR-encoded attestation object as a Hex string.
 */
export function getAttestationObject(options) {
    const { attStmt = {}, authData, fmt = 'none' } = options;
    return Cbor.encode({
        fmt,
        attStmt,
        authData: Hex.toBytes(authData),
    });
}
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