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JavaScript timers can be bypassed with “Infinity”

8 points| CryoLogic | 4 years ago |youtube.com

11 comments

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dragonwriter|4 years ago

Its not “bypassing” if you have to write the code used to setup the timer to do it.

I suppose it implies the existence of a class of potential problems if an application (1) accepts user input for timer delays, (2) requires a certain minimum delay, (3) only checks that the entered amount is >= the minimum without considering overflow behavior. But, since this behavior is well-documented (the MDN page on setTimeout covers it), it doesn't seem like any kind of notable discovery.

exevp|4 years ago

Also the example of bypassing this is rather contrived:

1) bypassing some timer in an API service requires the API to accept the string „Infinity“ and convert it to the JavaScript value Infinity - which is highly unlikely. Instead, the value would just fail the numeric validation.

2) bypassing some timer in client-side code by injecting Infinity seems overly complex - if you alter client-side code you might aswell just remove the validation instead of abusing edge cases of the language runtime.

himinlomax|4 years ago

Am I missing something or is this as dumb as it looks? How's that different from using 0?

CryoLogic|4 years ago

If a NodeJS application accepts a value from the client application, but validates against an early call (e.g. min 25 mins from now) the Infinity value can bypass that validation.

Because it's a relatively unknown side effect, most validations probably wouldn't check for Infinity.

Plus although Infinity pops off the timer at 0 seconds, a validation based on millisecond math would fail because Infinity > 25 minutes in milliseconds.

whoomp12342|4 years ago

this is no different than passing 0 right? I fail to see the significance, other than the fact that infinity doesn't work the way you think it would.

zodiakzz|4 years ago

"Hack"? Cute. Is this guy's first day at programming?