Ding-O-Tron

Description

Ding-O-Tron

What came first? The ding...or the flag?

https://uscybercombine-s4-web-ding-o-tron.chals.io/

Author: tsuto

Solution

The application let's you ring the bell and that seems to be it. If we look into source code it's loading Wasm (Web Assembly)

Ding-O-Tron

At the end of main.js we see commented function:

runWasm();

// giveFlag();

If we activate this function we get trolled by Emotional Damage wav

> giveFlag()
wasm_exec.js:22 [LOL] Did you think it would be that easy? Can you find my secret hidden function?

First I tried to debug the wasm with The WebAssembly Binary Toolkit, but wasm2c generate 900'000+ lines of code and that was pain. Since javascript is expsed to client let's see what functions we have:

> let prop, i = 0;
for (prop in window) {
  if (typeof window[prop] == "function") {
    console.log(i++, prop);
  }
}

VM3603:5 0 'alert'
VM3603:5 1 'atob'
VM3603:5 2 'blur'
VM3603:5 3 'btoa'
...
VM3603:5 197 'runWasm'
VM3603:5 198 'pad'
VM3603:5 199 'playSound'
VM3603:5 200 'updateCount'
VM3603:5 201 'yay'
VM3603:5 202 'winner'
VM3603:5 203 'ding'
VM3603:5 204 'giveFlag'
VM3603:5 205 'superSecretFunction_312e4c286bcb2ad0'
...

Ding-O-Tron-1

Flag: SIVUSCG{d1ng_d1ng_d1ng_d1ng}