ses/src/tame-date-constructor.js

Hardened JavaScript for Fearless Cooperation

// @ts-check

import {
  Date,
  TypeError,
  apply,
  construct,
  defineProperties,
} from './commons.js';

export default function tameDateConstructor() {
  const OriginalDate = Date;
  const DatePrototype = OriginalDate.prototype;

  // Use concise methods to obtain named functions without constructors.
  const tamedMethods = {
    /**
     * `%SharedDate%.now()` throw a `TypeError` starting with "secure mode".
     * See https://github.com/endojs/endo/issues/910#issuecomment-1581855420
     */
    now() {
      throw TypeError('secure mode Calling %SharedDate%.now() throws');
    },
  };

  /**
   * Tame the Date constructor.
   * See https://github.com/endojs/endo/issues/910#issuecomment-1581855420
   *
   * Common behavior
   *   * `new Date(x)` coerces x into a number and then returns a Date
   *     for that number of millis since the epoch
   *   * `new Date(NaN)` returns a Date object which stringifies to
   *     'Invalid Date'
   *   * `new Date(undefined)` returns a Date object which stringifies to
   *     'Invalid Date'
   *
   * OriginalDate (normal standard) behavior preserved by
   * `%InitialDate%`.
   *   * `Date(anything)` gives a string with the current time
   *   * `new Date()` returns the current time, as a Date object
   *
   * `%SharedDate%` behavior
   *   * `Date(anything)` throws a TypeError starting with "secure mode"
   *   * `new Date()` throws a TypeError starting with "secure mode"
   *
   * @param {{powers?: string}} [opts]
   */
  const makeDateConstructor = ({ powers = 'none' } = {}) => {
    let ResultDate;
    if (powers === 'original') {
      // eslint-disable-next-line no-shadow
      ResultDate = function Date(...rest) {
        if (new.target === undefined) {
          return apply(OriginalDate, undefined, rest);
        }
        return construct(OriginalDate, rest, new.target);
      };
    } else {
      // eslint-disable-next-line no-shadow
      ResultDate = function Date(...rest) {
        if (new.target === undefined) {
          throw TypeError(
            'secure mode Calling %SharedDate% constructor as a function throws',
          );
        }
        if (rest.length === 0) {
          throw TypeError(
            'secure mode Calling new %SharedDate%() with no arguments throws',
          );
        }
        return construct(OriginalDate, rest, new.target);
      };
    }

    defineProperties(ResultDate, {
      length: { value: 7 },
      prototype: {
        value: DatePrototype,
        writable: false,
        enumerable: false,
        configurable: false,
      },
      parse: {
        value: OriginalDate.parse,
        writable: true,
        enumerable: false,
        configurable: true,
      },
      UTC: {
        value: OriginalDate.UTC,
        writable: true,
        enumerable: false,
        configurable: true,
      },
    });
    return ResultDate;
  };
  const InitialDate = makeDateConstructor({ powers: 'original' });
  const SharedDate = makeDateConstructor({ powers: 'none' });

  defineProperties(InitialDate, {
    now: {
      value: OriginalDate.now,
      writable: true,
      enumerable: false,
      configurable: true,
    },
  });
  defineProperties(SharedDate, {
    now: {
      value: tamedMethods.now,
      writable: true,
      enumerable: false,
      configurable: true,
    },
  });

  defineProperties(DatePrototype, {
    constructor: { value: SharedDate },
  });

  return {
    '%InitialDate%': InitialDate,
    '%SharedDate%': SharedDate,
  };
}