JS: confidential variables (for safely transmitting a score)

Is it possible to retrieve a randomly generated value declared within an anonymous function (IIFE), and if so, how can it be achieved?

(function () {
  // assuming a complex, obscured random function
  var salt = random()*10000|0;

  // assuming an event manager
  Events.on('custom event', function () {
    // perform some amazing tasks with the salt variable here
  });
})()

Factors considered:

  • The function is loaded through ajax.
  • It runs on load, making breakpoint inclusion challenging.
  • There may exist a sleek solution to test for any potential injection (if such a thing exists).

Answer №1

An easily identifiable flaw in your JavaScript code allows the salt value to be exposed. While it may not be accessible to code outside of the IIFE (Immediate Invocation Function Expression - as you referred to as an anonymous function), attempting to hide it from a debugger by placing a breakpoint inside the IIFE will not prevent it from being seen.

For instance, it is possible to set a breakpoint at the exact point where the salt value is generated and view its contents. Alternatively, if the code loading process is done dynamically through AJAX, setting a breakpoint at that section and stepping through the loading process can eventually lead to identifying where the salt value is created.

Answer №2

There are a couple of methods to exploit this vulnerability. One option is to establish a breakpoint and change the salt value, or you could manipulate Math.random to consistently output a specific value. Unfortunately, there are limited ways to defend your program against these attacks. Additionally, identifying the affected code within a minified and obfuscated script can be extremely challenging.

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