sign.js

const timespan = require('./lib/timespan');
const PS_SUPPORTED = require('./lib/psSupported');
const validateAsymmetricKey = require('./lib/validateAsymmetricKey');
const jws = require('jws');
const includes = require('lodash.includes');
const isBoolean = require('lodash.isboolean');
const isInteger = require('lodash.isinteger');
const isNumber = require('lodash.isnumber');
const isPlainObject = require('lodash.isplainobject');
const isString = require('lodash.isstring');
const once = require('lodash.once');
const { KeyObject, createSecretKey, createPrivateKey } = require('crypto')

const SUPPORTED_ALGS = ['RS256', 'RS384', 'RS512', 'ES256', 'ES384', 'ES512', 'HS256', 'HS384', 'HS512', 'none'];
if (PS_SUPPORTED) {
  SUPPORTED_ALGS.splice(3, 0, 'PS256', 'PS384', 'PS512');
}

const sign_options_schema = {
  expiresIn: { isValid: function(value) { return isInteger(value) || (isString(value) && value); }, message: '"expiresIn" should be a number of seconds or string representing a timespan' },
  notBefore: { isValid: function(value) { return isInteger(value) || (isString(value) && value); }, message: '"notBefore" should be a number of seconds or string representing a timespan' },
  audience: { isValid: function(value) { return isString(value) || Array.isArray(value); }, message: '"audience" must be a string or array' },
  algorithm: { isValid: includes.bind(null, SUPPORTED_ALGS), message: '"algorithm" must be a valid string enum value' },
  header: { isValid: isPlainObject, message: '"header" must be an object' },
  encoding: { isValid: isString, message: '"encoding" must be a string' },
  issuer: { isValid: isString, message: '"issuer" must be a string' },
  subject: { isValid: isString, message: '"subject" must be a string' },
  jwtid: { isValid: isString, message: '"jwtid" must be a string' },
  noTimestamp: { isValid: isBoolean, message: '"noTimestamp" must be a boolean' },
  keyid: { isValid: isString, message: '"keyid" must be a string' },
  mutatePayload: { isValid: isBoolean, message: '"mutatePayload" must be a boolean' },
  allowInsecureKeySizes: { isValid: isBoolean, message: '"allowInsecureKeySizes" must be a boolean'},
  allowInvalidAsymmetricKeyTypes: { isValid: isBoolean, message: '"allowInvalidAsymmetricKeyTypes" must be a boolean'}
};

const registered_claims_schema = {
  iat: { isValid: isNumber, message: '"iat" should be a number of seconds' },
  exp: { isValid: isNumber, message: '"exp" should be a number of seconds' },
  nbf: { isValid: isNumber, message: '"nbf" should be a number of seconds' }
};

function validate(schema, allowUnknown, object, parameterName) {
  if (!isPlainObject(object)) {
    throw new Error('Expected "' + parameterName + '" to be a plain object.');
  }
  Object.keys(object)
    .forEach(function(key) {
      const validator = schema[key];
      if (!validator) {
        if (!allowUnknown) {
          throw new Error('"' + key + '" is not allowed in "' + parameterName + '"');
        }
        return;
      }
      if (!validator.isValid(object[key])) {
        throw new Error(validator.message);
      }
    });
}

function validateOptions(options) {
  return validate(sign_options_schema, false, options, 'options');
}

function validatePayload(payload) {
  return validate(registered_claims_schema, true, payload, 'payload');
}

const options_to_payload = {
  'audience': 'aud',
  'issuer': 'iss',
  'subject': 'sub',
  'jwtid': 'jti'
};

const options_for_objects = [
  'expiresIn',
  'notBefore',
  'noTimestamp',
  'audience',
  'issuer',
  'subject',
  'jwtid',
];

/**
 * (Asynchronous) If a callback is supplied, the callback is called with the err or the JWT.
 *
 * (Synchronous) Returns the JsonWebToken as string
 * @param {object | Buffer | string} payload Represents valid JSON.
 * @param {string | Buffer | object | KeyObject} secretOrPrivateKey Contains either the secret for HMAC algorithms or the PEM encoded private key for RSA and ECDSA. In case of a private key with passphrase an object `{ key, passphrase }` can be used (based on [crypto documentation](https://nodejs.org/api/crypto.html#crypto_sign_sign_private_key_output_format)), in this case be sure you pass the `algorithm` option. When signing with RSA algorithms the minimum modulus length is 2048 except when the allowInsecureKeySizes option is set to true. Private keys below this size will be rejected with an error.
 * @param {object?} options Options
 * @param {string} options.algorithm (default: `HS256`)
 * @param {string | number} options.expiresIn Expressed in seconds or a string describing a time span vercel/ms.
 * @param {string | number} options.notBefore Expressed in seconds or a string describing a time span vercel/ms.
 * @param options.audience
 * @param options.issuer
 * @param options.jwtid
 * @param options.subject
 * @param options.noTimestamp
 * @param options.header
 * @param options.keyid
 * @param {boolean} options.mutatePayload If `true`, the sign function will modify the payload object directly. This is useful if you need a raw reference to the payload after claims have been applied to it, but before it has been encoded into a token.
 * @param {boolean} options.allowInsecureKeySizes If `true` allows private keys with a modulus below 2048 to be used for RSA.
 * @param {boolean} options.allowInvalidAsymmetricKeyTypes If `true`, allows asymmetric keys which do not match the specified algorithm. This option is intended only for backwards compatability and should be avoided.
 * @param {function?} callback
 * @returns {*}
 */
module.exports = function (payload, secretOrPrivateKey, options, callback) {
  if (typeof options === 'function') {
    callback = options;
    options = {};
  } else {
    options = options || {};
  }

  const isObjectPayload = typeof payload === 'object' &&
                        !Buffer.isBuffer(payload);

  const header = Object.assign({
    alg: options.algorithm || 'HS256',
    typ: isObjectPayload ? 'JWT' : undefined,
    kid: options.keyid
  }, options.header);

  function failure(err) {
    if (callback) {
      return callback(err);
    }
    throw err;
  }

  if (!secretOrPrivateKey && options.algorithm !== 'none') {
    return failure(new Error('secretOrPrivateKey must have a value'));
  }

  if (secretOrPrivateKey != null && !(secretOrPrivateKey instanceof KeyObject)) {
    try {
      secretOrPrivateKey = createPrivateKey(secretOrPrivateKey)
    } catch (_) {
      try {
        secretOrPrivateKey = createSecretKey(typeof secretOrPrivateKey === 'string' ? Buffer.from(secretOrPrivateKey) : secretOrPrivateKey)
      } catch (_) {
        return failure(new Error('secretOrPrivateKey is not valid key material'));
      }
    }
  }

  if (header.alg.startsWith('HS') && secretOrPrivateKey.type !== 'secret') {
    return failure(new Error((`secretOrPrivateKey must be a symmetric key when using ${header.alg}`)))
  } else if (/^(?:RS|PS|ES)/.test(header.alg)) {
    if (secretOrPrivateKey.type !== 'private') {
      return failure(new Error((`secretOrPrivateKey must be an asymmetric key when using ${header.alg}`)))
    }
    if (!options.allowInsecureKeySizes &&
      !header.alg.startsWith('ES') &&
      secretOrPrivateKey.asymmetricKeyDetails !== undefined && //KeyObject.asymmetricKeyDetails is supported in Node 15+
      secretOrPrivateKey.asymmetricKeyDetails.modulusLength < 2048) {
      return failure(new Error(`secretOrPrivateKey has a minimum key size of 2048 bits for ${header.alg}`));
    }
  }

  if (typeof payload === 'undefined') {
    return failure(new Error('payload is required'));
  } else if (isObjectPayload) {
    try {
      validatePayload(payload);
    }
    catch (error) {
      return failure(error);
    }
    if (!options.mutatePayload) {
      payload = Object.assign({},payload);
    }
  } else {
    const invalid_options = options_for_objects.filter(function (opt) {
      return typeof options[opt] !== 'undefined';
    });

    if (invalid_options.length > 0) {
      return failure(new Error('invalid ' + invalid_options.join(',') + ' option for ' + (typeof payload ) + ' payload'));
    }
  }

  if (typeof payload.exp !== 'undefined' && typeof options.expiresIn !== 'undefined') {
    return failure(new Error('Bad "options.expiresIn" option the payload already has an "exp" property.'));
  }

  if (typeof payload.nbf !== 'undefined' && typeof options.notBefore !== 'undefined') {
    return failure(new Error('Bad "options.notBefore" option the payload already has an "nbf" property.'));
  }

  try {
    validateOptions(options);
  }
  catch (error) {
    return failure(error);
  }

  if (!options.allowInvalidAsymmetricKeyTypes) {
    try {
      validateAsymmetricKey(header.alg, secretOrPrivateKey);
    } catch (error) {
      return failure(error);
    }
  }

  const timestamp = payload.iat || Math.floor(Date.now() / 1000);

  if (options.noTimestamp) {
    delete payload.iat;
  } else if (isObjectPayload) {
    payload.iat = timestamp;
  }

  if (typeof options.notBefore !== 'undefined') {
    try {
      payload.nbf = timespan(options.notBefore, timestamp);
    }
    catch (err) {
      return failure(err);
    }
    if (typeof payload.nbf === 'undefined') {
      return failure(new Error('"notBefore" should be a number of seconds or string representing a timespan eg: "1d", "20h", 60'));
    }
  }

  if (typeof options.expiresIn !== 'undefined' && typeof payload === 'object') {
    try {
      payload.exp = timespan(options.expiresIn, timestamp);
    }
    catch (err) {
      return failure(err);
    }
    if (typeof payload.exp === 'undefined') {
      return failure(new Error('"expiresIn" should be a number of seconds or string representing a timespan eg: "1d", "20h", 60'));
    }
  }

  Object.keys(options_to_payload).forEach(function (key) {
    const claim = options_to_payload[key];
    if (typeof options[key] !== 'undefined') {
      if (typeof payload[claim] !== 'undefined') {
        return failure(new Error('Bad "options.' + key + '" option. The payload already has an "' + claim + '" property.'));
      }
      payload[claim] = options[key];
    }
  });

  const encoding = options.encoding || 'utf8';

  if (typeof callback === 'function') {
    callback = callback && once(callback);

    jws.createSign({
      header: header,
      privateKey: secretOrPrivateKey,
      payload: payload,
      encoding: encoding
    }).once('error', callback)
      .once('done', function (signature) {
        // TODO: Remove in favor of the modulus length check before signing once node 15+ is the minimum supported version
        if(!options.allowInsecureKeySizes && /^(?:RS|PS)/.test(header.alg) && signature.length < 256) {
          return callback(new Error(`secretOrPrivateKey has a minimum key size of 2048 bits for ${header.alg}`))
        }
        callback(null, signature);
      });
  } else {
    let signature = jws.sign({header: header, payload: payload, secret: secretOrPrivateKey, encoding: encoding});
    // TODO: Remove in favor of the modulus length check before signing once node 15+ is the minimum supported version
    if(!options.allowInsecureKeySizes && /^(?:RS|PS)/.test(header.alg) && signature.length < 256) {
      throw new Error(`secretOrPrivateKey has a minimum key size of 2048 bits for ${header.alg}`)
    }
    return signature
  }
};