Lexical Free Smallest Sandbox

smallest-sandbox.js

const outerLexicalEnvironment = {
  window: {},
  global: {},
  Object: {},
  Function: {},
  self: {},
  globalThis: {},
  Error: {},
  TypeError: {},
  JSON: {},
  Number: {},
  String: {},
  Array: {},
  Date: {},
  Boolean: {},
  RegExp: {},
  Proxy: {},
};

for (const key of Object.keys(self)) outerLexicalEnvironment[key] = {};

const outerLexicalEnvironmentList = Object.keys(outerLexicalEnvironment);

Object.freeze(outerLexicalEnvironment);
Object.freeze(outerLexicalEnvironmentList);

const sandbox = (code) => {
  try {
    let result;
    with (outerLexicalEnvironment) {
      function isObject(obj) {
        return obj !== null && typeof obj === "object";
      }

      function setValue(obj, key, value) {
        const keylist = key.split(".");
        const e = keylist.shift();
        if (keylist.length > 0) {
          if (!isObject(obj[e])) obj[e] = {};
          setValue(obj[e], keylist.join("."), value);
        } else {
          obj[key] = value;
          return obj;
        }
      }
      const obj1 = {};
      setValue(obj1, "prototype.constructor", null);
      setValue(obj1, "__proto__.constructor", null);

      for (const item of outerLexicalEnvironmentList) {
        try {
          eval(
            `${item}.constructor = null;${item}.prototype.constructor = null;${item}.__proto__.constructor = null;`
          );
        } catch (e) {}
      }

      const evalEnvironment = {
        eval: function (code) {
          return eval(
            `function lock (code) { "use strict"; return eval(\`${code}\`) }; lock()`
          );
        },
      };
      result = evalEnvironment.eval(code);
    }
    return result;
  } catch (e) {}
};

console.log(`window:`, sandbox("window"));
console.log(`"normal":`, sandbox('"normal"'));
console.log(`eval:`, sandbox("eval"));
console.log(`Object:`, sandbox("Object"));
console.log(`Function:`, sandbox("Function"));
console.log(
  `const a = function () { return this }; a():`,
  sandbox(`const a = function () { return this }; a()`)
);
console.log(
  `const a = function () { return window }; a():`,
  sandbox(`const a = function () { return window }; a()`)
);
console.log(`self: `, sandbox("self"));
console.log(
  `const a = function () { return self }; a():`,
  sandbox(`const a = function () { return self }; a()`)
);
console.log(`globalThis: `, sandbox("globalThis"));
console.log(
  `sandbox(\`const fn = Error.__proto__.constructor; (new fn('return window'))()\`)`,
  sandbox(`const fn = Error.__proto__.constructor; (new fn('return window'))()`)
);
console.log(
  `sandbox(\`try { throw new Error() } catch (e) { console.log(e.__proto__.valueOf) }\`)`,
  sandbox(
    `try { throw new Error() } catch (e) { console.log(e.__proto__.valueOf) }`
  )
);
sandbox(`(123).constructor.constructor`)