doc: Fully Expanded Passkey Objects + JSDoc types

[coolaj86]

TODO:

• Decode PEM to JWK
• correct CBOR parser for credentialId

Partial at go-webauthn/webauthn#291 (comment)

aaguid lookup: https://passkeydeveloper.github.io/passkey-authenticator-aaguids/explorer/?combined

Passkey (WebAuthn Credential) Registration (Creation)

./fixtures/apple-m2-01-credential-creation-response.json (fully decoded):

{
  "authenticatorAttachment": "platform",

  "id": "BvvM60zMdJwPG8Z2eeBjXu9nyd8",
  "rawId": "BvvM60zMdJwPG8Z2eeBjXu9nyd8",
  "rawIdHex": "06fbcceb4ccc749c0f1bc67679e0635eef67c9df",

  "response": {

    "attestationObject": "o2NmbXRkbm9uZWdhdHRTdG10oGhhdXRoRGF0YViYvyNDyj998pf0HSG0UpSMrRAgHVyp9ZDvZgDE0HEs2jBdAAAAAPv8MAcVTk7MjAtuAgVX170AFAb7zOtMzHScDxvGdnngY17vZ8nfpQECAyYgASFYINbKXNDEO9D2GzLehw5365SM4scbsysvT4DsOVZkCZqHIlggr6WD8AitmkMfu8UIs-QgwdGtjUmkMrhz_lhP-jxMG-g",
    "attestationObjectHex": "a363666d74646e6f6e656761747453746d74a06861757468446174615898bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9dfa5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",
    "attestation": {
      "fmt": "none",
      "attStmt": {},
      "authData": "bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9dfa5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",
      "authenticator": {
        "rpidHash": "bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda30",
        "isUserPresent": true,
        "userVerified": true,
        "isMultiDeviceCredential": true,
        "isBackedUp": true,
        "hasAttestedCredential": true,
        "hasExtensionData": false,
        "signCount": 0,
        "attestedCredentialData": "fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9df",
        "attestedCredential": {
          "aaguid": "fbfc3007-154e-4ecc-8c0b-6e020557d7bd",
          "credentialId": "06fbcceb4ccc749c0f1bc67679e0635eef67c9df",
          "publicKeyCBOR": "a5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",
          "publicKeyCOSE": {
            "1": 2,
            "3": -7,
            "-1": 1,
            "-2": "6761747453746d74a06861757468446174615898bf2343ca3f7df297f41d21b4",
            "-3": "ad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc3007154e4ecc8c0b"
          },
          "publicKeyJWK": {
            "kty": "EC",
            "alg": "ES256",
            "x": "",
            "y": ""
          }
        },
        "extensions": null
      }
    },

    "authenticatorData": "vyNDyj998pf0HSG0UpSMrRAgHVyp9ZDvZgDE0HEs2jBdAAAAAPv8MAcVTk7MjAtuAgVX170AFAb7zOtMzHScDxvGdnngY17vZ8nfpQECAyYgASFYINbKXNDEO9D2GzLehw5365SM4scbsysvT4DsOVZkCZqHIlggr6WD8AitmkMfu8UIs-QgwdGtjUmkMrhz_lhP-jxMG-g",
    "authenticatorDataHex": "bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9dfa5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",
    "authenticator": {
      "rpidHash": "bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda30",
      "isUserPresent": true,
      "userVerified": true,
      "isMultiDeviceCredential": true,
      "isBackedUp": true,
      "hasAttestedCredential": true,
      "hasExtensionData": false,
      "signCount": 0,
      "attestedCredentialData": "fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9df",
      "attestedCredential": {
        "aaguid": "fbfc3007-154e-4ecc-8c0b-6e020557d7bd",
        "credentialId": "06fbcceb4ccc749c0f1bc67679e0635eef67c9df",
        "publicKeyCBOR": "a5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",
        "publicKey": {
          "1": 2,
          "3": -7,
          "-1": 1,
          "-2": "21b452948cad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc300715",
          "-3": "8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9dfa501"
        },
        "publicKeyJWK": {
          "kty": "EC",
          "alg": "ES256",
          "crv": "P-256",
          "x": "IbRSlIytECAdXKn1kO9mAMTQcSzaMF0AAAAA-_wwBxU",
          "y": "jAtuAgVX170AFAb7zOtMzHScDxvGdnngY17vZ8nfpQE"
        }
      }
    },

    "clientDataJSON": "eyJ0eXBlIjoid2ViYXV0aG4uY3JlYXRlIiwiY2hhbGxlbmdlIjoidlZuWVVhWC1XMVZkcUtCWjdEdE5jcWdjR1MwbUVyNktCQzdmVmE5QkRHYyIsIm9yaWdpbiI6Imh0dHBzOi8vbG9jYWwucG9ja2V0aWQuYXBwIiwiY3Jvc3NPcmlnaW4iOmZhbHNlfQ",
    "clientDataJSONHex": "7b2274797065223a22776562617574686e2e637265617465222c226368616c6c656e6765223a2276566e595561582d57315664714b425a3744744e637167634753306d4572364b4243376656613942444763222c226f726967696e223a2268747470733a2f2f6c6f63616c2e706f636b657469642e617070222c2263726f73734f726967696e223a66616c73657d",
    "clientDataJSONString": "{\"type\":\"webauthn.create\",\"challenge\":\"vVnYUaX-W1VdqKBZ7DtNcqgcGS0mEr6KBC7fVa9BDGc\",\"origin\":\"https://local.pocketid.app\",\"crossOrigin\":false}",
    "clientData": {
      "type": "webauthn.create",
      "challenge": "vVnYUaX-W1VdqKBZ7DtNcqgcGS0mEr6KBC7fVa9BDGc",
      "origin": "https://local.pocketid.app",
      "crossOrigin": false
    },

    "publicKey": "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE1spc0MQ70PYbMt6HDnfrlIzixxuzKy9PgOw5VmQJmoevpYPwCK2aQx-7xQiz5CDB0a2NSaQyuHP-WE_6PEwb6A",
    "publicKeyHex": "3059301306072a8648ce3d020106082a8648ce3d03010703420004d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",
    "publicKeyDer": "3059301306072a8648ce3d020106082a8648ce3d03010703420004d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8",

    "publicKeyAlgorithm": -7,
    "publicKeyAlgo": "ES256",
    "publicKeyAlgorithmName": "ES256",

    "transports": [
      "hybrid",
      "internal"
    ]

  },

  "type": "public-key"
}

Passkey (WebAuthn Credential) Authentication (Attestation)

./fixtures/apple-m2-02-credential-request-response.json (fully decoded):

{
  "authenticatorAttachment": "platform",

  "id": "BvvM60zMdJwPG8Z2eeBjXu9nyd8",
  "rawId": "BvvM60zMdJwPG8Z2eeBjXu9nyd8",
  "rawIdHex": "06fbcceb4ccc749c0f1bc67679e0635eef67c9df",

  "response": {

    "authenticatorData": "vyNDyj998pf0HSG0UpSMrRAgHVyp9ZDvZgDE0HEs2jAdAAAAAA",
    "authenticatorDataHex": "bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda301d00000000",
    "authenticator": {
      "rpidHash": "bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda30",
      "isUserPresent": true,
      "userVerified": true,
      "isMultiDeviceCredential": true,
      "isBackedUp": true,
      "hasAttestedCredential": false,
      "hasExtensionData": false,
      "signCount": 0,
      "attestedCredentialData": null,
      "attestedCredential": null
    },

    "clientDataJSON": "eyJ0eXBlIjoid2ViYXV0aG4uZ2V0IiwiY2hhbGxlbmdlIjoiY0pDM1Bwa3pLOVBQeWFwRDJOQXVlTjBqVmltMUJPLU1iWHh6NDRXMWNUdyIsIm9yaWdpbiI6Imh0dHBzOi8vbG9jYWwucG9ja2V0aWQuYXBwIiwiY3Jvc3NPcmlnaW4iOmZhbHNlfQ",
    "clientDataJSONHex": "7b2274797065223a22776562617574686e2e676574222c226368616c6c656e6765223a22634a433350706b7a4b39505079617044324e4175654e306a56696d31424f2d4d6258787a34345731635477222c226f726967696e223a2268747470733a2f2f6c6f63616c2e706f636b657469642e617070222c2263726f73734f726967696e223a66616c73657d",
    "clientDataJSONString": "{\"type\":\"webauthn.get\",\"challenge\":\"cJC3PpkzK9PPyapD2NAueN0jVim1BO-MbXxz44W1cTw\",\"origin\":\"https://local.pocketid.app\",\"crossOrigin\":false}",
    "clientData": {
      "type": "webauthn.get",
      "challenge": "cJC3PpkzK9PPyapD2NAueN0jVim1BO-MbXxz44W1cTw",
      "origin": "https://local.pocketid.app",
      "crossOrigin": false
    },

    "hash": "e2eacf22fcb185ebab56d30ff6c3a48e370b55a5a7bb237cc891c57f4b145f13",

    "signature": "MEQCIEbaFzFqEPDuzy_CqEj4WcTGhIBw10YhHXS9H9RDK7uqAiAHTR4wgpiwITNvfGZCijobw66ovUnzeh2r8mdzl4al-Q",
    "signatureHex": "3044022046da17316a10f0eecf2fc2a848f859c4c6848070d746211d74bd1fd4432bbbaa0220074d1e308298b021336f7c66428a3a1bc3aea8bd49f37a1dabf267739786a5f9"

  },

  "type": "public-key"
}

Code Examples

Registration

'use strict';

let Passkey = require('$/src/lib/passkey.js');
let Bytes = require('$/src/lib/bytes.js');

// ./fixtures/apple-m2-01-credential-creation-response.json
let regResp = {
  authenticatorAttachment: 'platform',
  id: 'BvvM60zMdJwPG8Z2eeBjXu9nyd8',
  rawId: 'BvvM60zMdJwPG8Z2eeBjXu9nyd8',
  rawIdHex: '06fbcceb4ccc749c0f1bc67679e0635eef67c9df',
  response: {
    attestationObject:
      'o2NmbXRkbm9uZWdhdHRTdG10oGhhdXRoRGF0YViYvyNDyj998pf0HSG0UpSMrRAgHVyp9ZDvZgDE0HEs2jBdAAAAAPv8MAcVTk7MjAtuAgVX170AFAb7zOtMzHScDxvGdnngY17vZ8nfpQECAyYgASFYINbKXNDEO9D2GzLehw5365SM4scbsysvT4DsOVZkCZqHIlggr6WD8AitmkMfu8UIs-QgwdGtjUmkMrhz_lhP-jxMG-g',
    attestationObjectHex:
      'a363666d74646e6f6e656761747453746d74a06861757468446174615898bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9dfa5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8',
    authenticatorData:
      'vyNDyj998pf0HSG0UpSMrRAgHVyp9ZDvZgDE0HEs2jBdAAAAAPv8MAcVTk7MjAtuAgVX170AFAb7zOtMzHScDxvGdnngY17vZ8nfpQECAyYgASFYINbKXNDEO9D2GzLehw5365SM4scbsysvT4DsOVZkCZqHIlggr6WD8AitmkMfu8UIs-QgwdGtjUmkMrhz_lhP-jxMG-g',
    authenticatorDataHex:
      'bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda305d00000000fbfc3007154e4ecc8c0b6e020557d7bd001406fbcceb4ccc749c0f1bc67679e0635eef67c9dfa5010203262001215820d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87225820afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8',
    clientDataJSON:
      'eyJ0eXBlIjoid2ViYXV0aG4uY3JlYXRlIiwiY2hhbGxlbmdlIjoidlZuWVVhWC1XMVZkcUtCWjdEdE5jcWdjR1MwbUVyNktCQzdmVmE5QkRHYyIsIm9yaWdpbiI6Imh0dHBzOi8vbG9jYWwucG9ja2V0aWQuYXBwIiwiY3Jvc3NPcmlnaW4iOmZhbHNlfQ',
    clientDataJSONHex:
      '7b2274797065223a22776562617574686e2e637265617465222c226368616c6c656e6765223a2276566e595561582d57315664714b425a3744744e637167634753306d4572364b4243376656613942444763222c226f726967696e223a2268747470733a2f2f6c6f63616c2e706f636b657469642e617070222c2263726f73734f726967696e223a66616c73657d',
    publicKey:
      'MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE1spc0MQ70PYbMt6HDnfrlIzixxuzKy9PgOw5VmQJmoevpYPwCK2aQx-7xQiz5CDB0a2NSaQyuHP-WE_6PEwb6A',
    publicKeyHex:
      '3059301306072a8648ce3d020106082a8648ce3d03010703420004d6ca5cd0c43bd0f61b32de870e77eb948ce2c71bb32b2f4f80ec395664099a87afa583f008ad9a431fbbc508b3e420c1d1ad8d49a432b873fe584ffa3c4c1be8',
    publicKeyAlgorithm: -7,
    publicKeyAlgorithmName: 'ES256',
    transports: ['hybrid', 'internal'],
  },
  type: 'public-key',
};

let resp = Passkey.reg.parse(regResp);
Object.assign(regResp.response, resp);

function bytesToHex(key, val) {
  if (val instanceof Uint8Array) {
    return Bytes.bytesToHex(val);
  }
  return val;
}

let json = JSON.stringify(regResp, bytesToHex, 2);
console.log(json);

Authentication

'use strict';

let Passkey = require('$/src/lib/passkey.js');
let Bytes = require('$/src/lib/bytes.js');

// ./fixtures/apple-m2-02-credential-request-response.json
let authnResp = {
  authenticatorAttachment: 'platform',
  id: 'BvvM60zMdJwPG8Z2eeBjXu9nyd8',
  rawId: 'BvvM60zMdJwPG8Z2eeBjXu9nyd8',
  rawIdHex: '06fbcceb4ccc749c0f1bc67679e0635eef67c9df',
  response: {
    authenticatorData: 'vyNDyj998pf0HSG0UpSMrRAgHVyp9ZDvZgDE0HEs2jAdAAAAAA',
    authenticatorDataHex:
      'bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda301d00000000',
    clientDataJSON:
      'eyJ0eXBlIjoid2ViYXV0aG4uZ2V0IiwiY2hhbGxlbmdlIjoiY0pDM1Bwa3pLOVBQeWFwRDJOQXVlTjBqVmltMUJPLU1iWHh6NDRXMWNUdyIsIm9yaWdpbiI6Imh0dHBzOi8vbG9jYWwucG9ja2V0aWQuYXBwIiwiY3Jvc3NPcmlnaW4iOmZhbHNlfQ',
    clientDataJSONHex:
      '7b2274797065223a22776562617574686e2e676574222c226368616c6c656e6765223a22634a433350706b7a4b39505079617044324e4175654e306a56696d31424f2d4d6258787a34345731635477222c226f726967696e223a2268747470733a2f2f6c6f63616c2e706f636b657469642e617070222c2263726f73734f726967696e223a66616c73657d',
    signature:
      'MEQCIEbaFzFqEPDuzy_CqEj4WcTGhIBw10YhHXS9H9RDK7uqAiAHTR4wgpiwITNvfGZCijobw66ovUnzeh2r8mdzl4al-Q',
    signatureHex:
      '3044022046da17316a10f0eecf2fc2a848f859c4c6848070d746211d74bd1fd4432bbbaa0220074d1e308298b021336f7c66428a3a1bc3aea8bd49f37a1dabf267739786a5f9',
  },
  type: 'public-key',
};

let resp = Passkey.authn.parse(authnResp);
Object.assign(authnResp.response, resp);

function bytesToHex(key, val) {
  if (val instanceof Uint8Array) {
    return Bytes.bytesToHex(val);
  }
  return val;
}

let json = JSON.stringify(authnResp, bytesToHex, 2);
console.log(json);

[coolaj86]

Simple CBOR Parser

Example

import CBOR from './cbor.js';

let cborHex = 'bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda301d00000000';
let cborBytes = Bytes.hexToBytes(cbor);
let data = CBOR.parse(cborBytes);
console.log(data);

let CBOR = require('./cbor.js');

let cborHex = 'bf2343ca3f7df297f41d21b452948cad10201d5ca9f590ef6600c4d0712cda301d00000000';
let cborBytes = Bytes.hexToBytes(cbor);
let data = CBOR.parse(cborBytes);
console.log(data);

Parser

'use strict';
// jshint bitwise: false

/**
 * @license CC0-1.0
 *
 * @root/cbor-parser.js - for WebAuthn Passkey data
 *
 * Authored in 2024 by AJ ONeal
 * To the extent possible under law, the author(s) have dedicated all copyright
 * and related and neighboring rights to this software to the public domain
 * worldwide. This software is distributed without any warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication along with
 * this software. If not, see <https://creativecommons.org/publicdomain/zero/1.0/>.
 */

// for ESM
let CBOR = {};

// for CommonJS:
//let CBOR = module.exports;

CBOR.parse = function (bytes) {
  let cbor = CBOR.create(bytes);
  let result = cbor._parse();
  return result;
};

CBOR.create = function (data) {
  let cbor = {};

  cbor._data = new DataView(data.buffer, data.byteOffset, data.byteLength);
  cbor._offset = 0;

  cbor._parse = function () {
    let initialByte = cbor._readByte();
    let majorType = initialByte >> 5; // First 3 bits
    let additionalInfo = initialByte & 0x1f; // Last 5 bits
    return cbor._parseItem(majorType, additionalInfo);
  };

  cbor._parseItem = function (majorType, additionalInfo) {
    switch (majorType) {
      case 0:
        return cbor._parseUnsignedInt(additionalInfo);
      case 1:
        return cbor._parseNegativeInt(additionalInfo);
      case 2:
        return cbor._parseByteString(additionalInfo);
      case 3:
        return cbor._parseTextString(additionalInfo);
      case 4:
        return cbor._parseArray(additionalInfo);
      case 5:
        return cbor._parseMap(additionalInfo);
      case 6:
        return cbor._parseTag(additionalInfo);
      case 7:
        return cbor._parseSimpleValue(additionalInfo);
      default:
        throw new Error(`Unsupported major type: ${majorType}`);
    }
  };

  cbor._parseUnsignedInt = function (additionalInfo) {
    return cbor._decodeLength(additionalInfo);
  };

  cbor._parseNegativeInt = function (additionalInfo) {
    let unsignedValue = cbor._decodeLength(additionalInfo);
    return -1 - unsignedValue;
  };

  cbor._parseByteString = function (additionalInfo) {
    let length = cbor._decodeLength(additionalInfo);
    return cbor._readBytes(length);
  };

  cbor._parseTextString = function (additionalInfo) {
    let length = cbor._decodeLength(additionalInfo);
    let textBytes = cbor._readBytes(length);
    return new TextDecoder().decode(textBytes);
  };

  cbor._parseArray = function (additionalInfo) {
    if (additionalInfo === 31) {
      // Indefinite length array
      let array = [];
      while (cbor._peekByte() !== 0xff) {
        array.push(cbor._parse());
      }
      cbor._readByte(); // consume stop code
      return array;
    }
    let length = cbor._decodeLength(additionalInfo);
    let array = [];
    for (let i = 0; i < length; i += 1) {
      array.push(cbor._parse());
    }
    return array;
  };

  cbor._parseMap = function (additionalInfo) {
    if (additionalInfo === 31) {
      // Indefinite length map
      let map = {};
      while (cbor._peekByte() !== 0xff) {
        let key = cbor._parse();
        let value = cbor._parse();
        map[key] = value;
      }
      cbor._readByte(); // consume stop code
      return map;
    }
    let length = cbor._decodeLength(additionalInfo);
    let map = {};
    for (let i = 0; i < length; i += 1) {
      let key = cbor._parse();
      let value = cbor._parse();
      map[key] = value;
    }
    return map;
  };

  // Parse tags (e.g. for big numbers)
  cbor._parseTag = function (additionalInfo) {
    let tag = cbor._decodeLength(additionalInfo);
    let value = cbor._parse();
    if (tag === 18) {
      // Special type for positive bignum
      return value;
    }
    return { tag, value };
  };

  cbor._parseSimpleValue = function (additionalInfo) {
    switch (additionalInfo) {
      case 20:
        return false;
      case 21:
        return true;
      case 22:
        return null;
      case 23:
        return undefined;
      case 24:
        return cbor._readByte(); // simple value
      case 25:
        return cbor._parseFloat16();
      case 26:
        return cbor._parseFloat32();
      case 27:
        return cbor._parseFloat64();
      case 31:
        return null; // Indefinite-length item (handled by array/map)
      default:
        throw new Error(`Unsupported simple value: ${additionalInfo}`);
    }
  };

  cbor._decodeLength = function (additionalInfo) {
    if (additionalInfo < 24) {
      return additionalInfo;
    }
    if (additionalInfo === 24) {
      return cbor._readByte();
    }
    if (additionalInfo === 25) {
      return cbor._readUint16();
    }
    if (additionalInfo === 26) {
      return cbor._readUint32();
    }
    if (additionalInfo === 27) {
      return cbor._readUint64();
    }
    throw new Error(`Unsupported additional info: ${additionalInfo}`);
  };

  cbor._readUint16 = function () {
    let val = cbor._data.getUint16(cbor._offset);
    cbor._offset += 2;
    return val;
  };

  cbor._readUint32 = function () {
    let val = cbor._data.getUint32(cbor._offset);
    cbor._offset += 4;
    return val;
  };

  cbor._readUint64 = function () {
    let high = cbor._data.getUint32(cbor._offset);
    let low = cbor._data.getUint32(cbor._offset + 4);
    cbor._offset += 8;
    return (BigInt(high) << 32n) | BigInt(low);
  };

  cbor._readByte = function () {
    let b = cbor._data.getUint8(cbor._offset);
    cbor._offset += 1;
    return b;
  };

  cbor._peekByte = function () {
    return cbor._data.getUint8(cbor._offset);
  };

  cbor._readBytes = function (length) {
    let bytes = new Uint8Array(cbor._data.buffer, cbor._offset, length);
    cbor._offset += length;
    return bytes;
  };

  cbor._parseFloat16 = function () {
    let u16 = cbor._readUint16();

    let exponentBits = u16 >> 10;
    let exponent = exponentBits & 0x1f;

    let mantissa = u16 & 0x3ff;

    // Check for subnormal numbers (exponent = 0) or zero
    if (exponent === 0) {
      // Subnormal number or zero: exponent is implicitly -14, no leading 1 in mantissa
      let f16 = mantissa * 5.96e-8; // 2^(-24)
      return f16;
    }

    // Check for special cases (exponent = 31): infinity or NaN
    if (exponent === 31) {
      if (mantissa !== 0) {
        return NaN;
      }
      return Infinity;
    }

    // Normalize the fraction (add the implicit leading 1 for normalized numbers)
    let normalizedMantissa = mantissa / 1024 + 1;
    // Adjust the exponent (bias of 15)
    let adjustedExponent = exponent - 15;
    // Calculate the result as: (1 + fraction) * 2^(exponent - bias)
    let f16 = normalizedMantissa * 2 ** adjustedExponent;

    return f16;
  };

  cbor._parseFloat32 = function () {
    return cbor._data.getFloat32(cbor._offset, false);
  };

  cbor._parseFloat64 = function () {
    let val = cbor._data.getFloat64(cbor._offset, false);
    cbor._offset += 8;
    return val;
  };

  return cbor;
};

// for ESM:
export default CBOR;